genesysv8 v8.1 addendum -...

GENESYS V8

V8.1 Addendum

Copyright 1986-2002

Eagleware Corporation635 Pinnacle CourtNorcross, GA 30071

Phone: (678) 291-0995FAX: (678) 291-0971E-Mail: [email protected]://www.eagleware.com

Printed in the USA

Table of Contents

Chapter 1: What’s new in Genesys 8.1 .....................................................................9 New SPECTRASYS system simulator is now available ...................................... 9 Graph Improvements ........................................................................................... 9 New Coax cable models ...................................................................................... 9 New SYSTEM models.......................................................................................... 9 FILTER, A/FILTER, M/FILTER........................................................................... 10 LAYOUT............................................................................................................. 10 SCHEMAX.......................................................................................................... 10 EMPOWER ........................................................................................................ 10 HARBEC ............................................................................................................ 10 Optimization and Yield ....................................................................................... 10 Tables................................................................................................................. 10 Ease-of-use Improvements ................................................................................ 11

Changes from GENESYS 8.0.................................................................................... 11 New Linear Models ............................................................................................ 11 SCHEMAX - Schematic Capture........................................................................ 12 Test Link - Instrument Interface ......................................................................... 12 Simulation........................................................................................................... 12 Graphing............................................................................................................. 12 Layout................................................................................................................. 12 Support............................................................................................................... 12

Chapter 2: FILTER.....................................................................................................13 Overview .................................................................................................................... 13 Walkthrough............................................................................................................... 13

Chapter 3: A/FILTER .................................................................................................19 Overview .................................................................................................................... 19 Walkthrough............................................................................................................... 19 Parameters ................................................................................................................ 21

Component Defaults .......................................................................................... 21 Preferences ........................................................................................................ 21

Chapter 4: M/FILTER.................................................................................................23 Overview .................................................................................................................... 23

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Walkthrough............................................................................................................... 23 Chapter 5: Advanced TLINE Operation...................................................................31

Overview .................................................................................................................... 31 Advanced TLINE Example......................................................................................... 31 Advanced TLINE Dialog Box ..................................................................................... 41

Chapter 6: TESTLINK................................................................................................43 TESTLINK Walkthrough............................................................................................. 43 TESTLINK Instrument Interface Overview................................................................. 46 TESTLINK Hardware Interface .................................................................................. 48

Chapter 7: Workspace Window ...............................................................................51

Chapter 8: SCHEMAX ...............................................................................................53 Schematic Element Properties .................................................................................. 53

Parameters Tab.................................................................................................. 53 Simulation Tab ................................................................................................... 55 Schematic Part Layout Options.......................................................................... 56

Zooming ..................................................................................................................... 57 Chapter 9: LAYOUT...................................................................................................59

Step And Repeat........................................................................................................ 59 GDSII Setup............................................................................................................... 59

Chapter 10: Graphs and Tables.................................................................................61 Markers ...................................................................................................................... 61

Fly-over Tool Tips............................................................................................... 62 Graphs and Markers Are Customizable............................................................. 63

Advanced Marker Types............................................................................................ 63 Peak Markers ..................................................................................................... 63 Delta Markers ..................................................................................................... 64 Marker Names.................................................................................................... 65 Bandwidth Markers............................................................................................. 65

Marker Properties ...................................................................................................... 66 Keyboard commands................................................................................................. 67 Mouse Actions ........................................................................................................... 68 Zooming On Charts.................................................................................................... 68

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Chapter 11: SPECTRASYS (System Simulation) Operation ...................................69 Overview .................................................................................................................... 69 System Models .......................................................................................................... 69 Glossary..................................................................................................................... 70

Chapter 12: SPECTRASYS Dialog Box Reference ..................................................73 System Simulation Parameters - General ................................................................. 73 System Simulation Parameters - Paths ..................................................................... 74 System Simulation Parameters - Calculate ............................................................... 75 System Simulation Parameters - Composite Spectrum ............................................ 77 System Simulation Parameters - Options.................................................................. 79

Chapter 13: SPECTRASYS Walkthrough..................................................................81 Creating a Schematic ................................................................................................ 81 Adding a SPECTRASYS simulation .......................................................................... 82 Level Diagrams.......................................................................................................... 84 Tuning Parameters .................................................................................................... 85 Add an Amplifier......................................................................................................... 86 Add a Mixer................................................................................................................ 88 Multiple Signals.......................................................................................................... 89

Chapter 14: SPECTRASYS: How it Works................................................................91 Amplifiers ................................................................................................................... 91

General RF and VGA (Variable Gain) Amplifier Parameters............................. 91 Channel Definitions.................................................................................................... 93

Channelized Measurements and Measurement Bandwidth .............................. 93 Channel (Path) Frequency ................................................................................. 93 Offset Channel ................................................................................................... 94

Coherency.................................................................................................................. 95 Overview ............................................................................................................ 95

Composite Spectrum ................................................................................................. 97 Identifying Spectral Origin .................................................................................. 97 Path Spectrum.................................................................................................. 100 Noise Spectrum................................................................................................ 101 Intermod Spectrum........................................................................................... 101

Intermods & Harmonics ........................................................................................... 101 Calculate Intermods and Harmonics................................................................ 101

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Cascaded Intermod Equations......................................................................... 105 Intermod Tests ......................................................................................................... 105

Calculate IIP3 (TOI).......................................................................................... 105 Mixers....................................................................................................................... 106 Noise ........................................................................................................................ 108

Broadband Noise.............................................................................................. 108 Paths ........................................................................................................................ 110

Measurements are Defined by Paths............................................................... 110 Path Frequency................................................................................................ 111 Directional Energy (Node Voltage and Power) ................................................ 111 Transmitted Energy.......................................................................................... 112

Outputs .................................................................................................................... 113 Analyzer Mode ................................................................................................. 113 Level Diagrams ................................................................................................ 115 Composite Spectrum........................................................................................ 117 Controlling Spectrum Limits ............................................................................. 119 Simulation Speed-Ups ..................................................................................... 121

Sources.................................................................................................................... 121 Synthesis ................................................................................................................. 124

Chapter 15: SPECTRASYS Tips ..............................................................................127

Chapter 16: Menu/Toolbar........................................................................................129 Schematic Menu ...................................................................................................... 129 Graph Menu ............................................................................................................. 130 Main Graph Toolbar ................................................................................................. 131

Chapter 17: Filter Synthesis Examples...................................................................133 FILTER\Gaussian_12dB.wsp .................................................................................. 133 MFILTER\Chebyshev Bandpass.wsp ...................................................................... 135 AFILTER\Lowpass Minimum Inductor.wsp.............................................................. 139 AFILTER\Lowpass Minimum Capacitor.wsp ........................................................... 141 AFILTER\Lowpass Single Feedback.wsp................................................................ 143 AFILTER\Lowpass Multiple Feedback.wsp ............................................................. 145 AFILTER\Bandpass Maximum Gain Dual Amplifier.wsp......................................... 147

Chapter 18: SPECTRASYS Examples .....................................................................149

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SPECTRASYS\Getting Started\GS1_Setup.WSP .................................................. 149 SPECTRASYS\Getting Started\GS2_Spec_Prop.WSP.......................................... 152 SPECTRASYS\Getting Started\GS3_Sources.WSP............................................... 155 SPECTRASYS\Getting Started\GS4_Chan_Meas.WSP ........................................ 160 SPECTRASYS\Getting Started\GS5_Paths.WSP................................................... 163 SPECTRASYS\Getting Started\GS6_Noise.WSP................................................... 166 SPECTRASYS\Getting Started\GS7_Coherent.WSP............................................. 170 SPECTRASYS\Getting Started\GS8_Intermods.WSP............................................ 172 SPECTRASYS\Getting Started\GS9_Mixers.WSP ................................................. 178 SPECTRASYS\Amplifiers\Feed Forward Amplifier.WSP........................................ 182 SPECTRASYS\Amplifiers\Quad Hybrid Matrix Amp.WSP...................................... 187 SPECTRASYS\TX & RX\TX and RX Chain.WSP ................................................... 190 SPECTRASYS\Noise\TX Noise in RX Band.WSP.................................................. 193 SPECTRASYS\Transmitters\Diversity TX and Hybrid Amp.WSP........................... 196

Chapter 19: Measurement Overview.......................................................................199 Overview .................................................................................................................. 199 Linear Measurements .............................................................................................. 199 Nonlinear Measurements......................................................................................... 201 Operators ................................................................................................................. 201 Sample Measurements............................................................................................ 203 Using Non-Default Simulation/Data ......................................................................... 203 Using Equation Results (post-processing) .............................................................. 204

Chapter 20: Linear Measurements ..........................................................................205 S-Parameters........................................................................................................... 205 H-Parameters........................................................................................................... 206 Y-Parameters........................................................................................................... 207 Z-Parameters ........................................................................................................... 208 Voltage Standing Wave Ratio (VSWR) ................................................................... 209 Input Impedance / Admittance (ZINi, YINi) .............................................................. 210 Voltage Gain ............................................................................................................ 211 Noise Measure (NMEAS) ........................................................................................ 212 Noise Figure (NF) / Minimum Noise Figure (NFMIN) .............................................. 213 Constant Noise Circles (NCI)................................................................................... 214 Noise Correlation Matrix Parameters....................................................................... 215 Simultaneous Match Gamma at Port i (GMi) ........................................................... 216

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Simultaneous Match Admittance / Impedance at Port i(ZMi, YMi) ......................... 217 Maximum Available Gain (GMAX) ........................................................................... 218 Available Gain & Power Gain Circles (GA, GP) ...................................................... 219 Unilateral Gain Circles at Port i (GU1, GU2) ........................................................... 220 Stability Factor (K), Stability Measure (B1).............................................................. 221 Input / Output Plane Stability Circles (SB1, SB2) .................................................... 222 Optimal Gamma for Noise (GOPT).......................................................................... 223 Optimal Admittance / Impedance for Noise (YOPT, ZOPT) .................................... 224 Effective Noise Input Temperature (NFT)................................................................ 225 Normalized Noise Resistance (RN) ......................................................................... 226 Reference Impedance (ZPORTi) ............................................................................. 227

Chapter 21: Nonlinear Measurements ....................................................................229 Port Power (Pport) ..................................................................................................... 229 Probe Current (Iprobe) ................................................................................................ 230 Node Voltage (Vnode) ................................................................................................ 231 Reference Impedance (ZPORTi) ............................................................................. 232

Chapter 22: SPECTRASYS Measurements.............................................................233 Adjacent Channel Power (ACP[U or L][n])............................................................... 233 Adjacent Channel Frequency (ACF[U or L][n]) ........................................................ 234 Added Noise (AN) .................................................................................................... 235 Cascaded Gain (CGAIN) ......................................................................................... 236 Cascaded Third Order Intermod Gain (CGAINIM3) ................................................ 237 Conducted Third Order Intermod Power (CIM3P) ................................................... 238 Carrier to Noise Ratio (CNR) ................................................................................... 239 Cascaded Noise Figure (CNF) ................................................................................ 240 Channel (or Path) Frequency (CF) .......................................................................... 241 Channel Noise Power (CNP) ................................................................................... 242 Channel Power (CP) ................................................................................................ 243 Desired Channel Power (DCP)................................................................................ 244 Desired Third Order Intermod Channel Power (DCPIM3) ....................................... 245 Gain (GAIN) ............................................................................................................. 246 Generated Third Order Intermod Power (GIM3P) ................................................... 247 Image Frequency (IMGF)......................................................................................... 248 Input Third Order Intercept (IIP3)............................................................................. 249 Mixer Image Channel Power (IMGP)....................................................................... 250

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Mixer Image Rejection Ratio (IMGR)....................................................................... 251 Offset Channel Frequency (OCF)............................................................................ 252 Offset Channel Power (OCP) .................................................................................. 253 Output Third Order Intercept (OIP3) ........................................................................ 254 Spurious Free Dynamic Range (SFDR) .................................................................. 256 Stage Dynamic Range (SDR).................................................................................. 257 Stage Noise Figure (SNF) ....................................................................................... 258 Stage Output 1 dB Compression Point (SOP1DB).................................................. 259 Stage Output Third Order Intercept (SOIP3) ........................................................... 260 Stage Output Saturation Power (SOPSAT)............................................................. 261 Third Order Intermod Gain (GAINIM3) .................................................................... 262 Tone Channel Frequency (TCF).............................................................................. 263 Tone Channel Power (TCP) .................................................................................... 264 Total Third Order Intermod Power (TIM3P)............................................................. 266

Chapter 23: New System Elements and Behavioral Models.................................267 Coupled Antenna (ANTC)........................................................................................ 267 RF Attenuator (ATTN).............................................................................................. 268 RF Attenuator (ATTN_VAR) .................................................................................... 269 Dual Directional Coupler (COUPLER2) ................................................................... 270 Ideal three port circulator (CIR3) ............................................................................. 271 RF Circulator (CIR) .................................................................................................. 272 Single RF Directional Coupler (COUPLER1) .......................................................... 273 Time Delay (DELAY)................................................................................................ 274 Ideal gain block (GAIN) - LINEAR ........................................................................... 275 Hybrid 90 Degree Coupler (HYBRID1) .................................................................... 276 RF Isolator (ISO)...................................................................................................... 277 Ideal isolator (ISOLATOR)....................................................................................... 278 LOG_DET (Log Detector) ........................................................................................ 279 RF Mixer (MIXERA, MIXERP) ................................................................................. 280 Antenna Path Loss (PATH) ..................................................................................... 282 Ideal Phase Shift (PHASE) ...................................................................................... 283 RF Amplifier (RFAMP) ............................................................................................ 284 RF Switch SPDT (SPDT)......................................................................................... 286 RF 2 Way - 0° Splitter / Combiner (SPLIT2)............................................................ 287 RF 2 Way - 0°/ 180° Splitter / Combiner (SPLIT2180) ............................................ 288

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RF 2 Way - 0°/ 90° Splitter / Combiner (SPLIT290) ................................................ 289 RF 3 Way - 0° Splitter / Combiner (SPLIT3)............................................................ 290 RF 4 Way - 0° Splitter / Combiner (SPLIT4)............................................................ 291 RF 5 Way - 0° Splitter / Combiner (SPLIT5)............................................................ 293 RF Switch SPST (SPST) ......................................................................................... 295 VGA (Variable Gain Amplifier) ................................................................................. 296

Chapter 24: Filter Elements (System Toolbar) .......................................................299 Bessel Bandpass Filter (BPF_BESSEL)................................................................. 299 Butterworth Bandpass Filter (BPF_BUTTER) ........................................................ 300 Chebyshev Bandpass Filter (BPF_CHEBY) ........................................................... 301 Elliptic Bandpass Filter (BPF_ELLIPTIC) ............................................................... 302 Pole / Zero Bandpass Filter (BPF_POLES)............................................................ 303 Bessel Bandstop Filter (BSF_BESSEL) ................................................................. 305 Butterworth Bandstop Filter (BSF_BUTTER) ......................................................... 306 Chebyshev Bandstop Filter (BSF_CHEBY)............................................................ 307 Elliptic Bandstop Filter (BSF_ELLIPTIC) ................................................................ 308 Pole / Zero Bandstop Filter (BSF_POLES)............................................................. 309 Duplexer with Chebyshev Filters (DUPLEXER_C)................................................. 311 Duplexer with Elliptic Filters (DUPLEXER_E) ........................................................ 313 Bessel Highpass Filter (HPF_BESSEL) ................................................................. 315 Butterworth Highpass Filter (HPF_BUTTER) ......................................................... 316 Chebyshev Highpass Filter (HPF_CHEBY)............................................................ 317 Elliptic Highpass Filter (HPF_ELLIPTIC) ................................................................ 318 Pole / Zero Highpass Filter (HPF_POLES) ............................................................ 319 Bessel Lowpass Filter (LPF_BESSEL)................................................................... 321 Butterworth Lowpass Filter (LPF_BUTTER)........................................................... 322 Chebyshev Lowpass Filter (LPF_CHEBY) ............................................................. 323 Elliptic Lowpass Filter (LPF_ELLIPTIC).................................................................. 324 Pole / Zero Lowpass Filter (LPF_POLES) .............................................................. 325

Chapter 1: What’s new in Genesys 8.1

New SPECTRASYS system simulator is now available

!" RF System / Architecture design tool !" Identify the origin, path, and phase of spectral components !" Over 30 channelized system measurements !" New graphs: Level diagrams and composite spectrums

Graph Improvements

• Popup (fly-over) tool-tip info; just hover the cursor over a marker or trace. • Rectangular Zoom (on rectangular charts) • New Marker types:

o Peak (follows peaks during tuning) o Valley (follows valleys during tuning) o Bandwidth (automatically measures bandwidth) o Relative left and right o Standard

• Added new Marker Properties dialog box (can now enter a marker frequency by X-value)

• Marker text will no longer overlap other marker text • Greatly expanded Graph toolbar • Added Mark All Traces toggle (can now mark individual traces) • Added level-of-detail simplification to Smith charts (increases rendering speed) • Improved graph traces: auto-bold traces, each sweep trace is drawn in a unique

color • Improved autoscale ranges • Improved graph printing

New Coax cable models

!" CABLE, RG6, RG8, RG9, RG58, RG59, RG214 New SYSTEM models

!" RFAMP, MIXERP (passive), MIXERA (active), SPDT, SPST, !" ATTN (attenuator), ATTN_VAR (variable attenuator), !" SPLIT2 (2 way splitter / combiner), SPLIT290 (2 way 90° splitter), !" SPLIT2180 (2 way 180° splitter), SPLIT3, SPLIT4, SPLIT5, !" LPF_BUTTER (Lowpass Butterworth Filter), LPF_BESSEL (Lowpass Bessel), !" LPF_CHEBY, LPF_ELLIPTIC, LPF_POLES (Lowpass Pole Zero Filter), !" BPF_BUTTER (Bandpass Butterworth Filter), BPF_BESSEL (Bandpass Bessel), !" BPF_CHEBY, BPF_ELLIPTIC, BPF_POLES (Bandpass Pole Zero Filter), !" HPF_BUTTER (Highpass Butterworth Filter), HPF_BESSEL (Highpass Bessel), !" HPF_CHEBY, HPF_ELLIPTIC, HPF_POLES (Highpass Pole Zero Filter),

What’s new in Genesys 8.1

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!" BSF_BUTTER (Bandstop Butterworth Filter), BSF_BESSEL (Bandstop Bessel), !" BSF_CHEBY, BSF_ELLIPTIC, BSF_POLES (Bandstop Pole Zero Filter), !" DUPLEXER_C (Chebyshev Duplexer), DUPLEXER_E (Elliptic Duplexer) !" DELAY (Time delay), PHASE (Ideal Phase Shift), CIRCULATOR, !" ISO (Isolator), COUPLER1 (Single Directional Coupler), !" COUPLER2 (Dual Directional Coupler), HYBRID1 (90 Degree Hybrid Coupler) !" LOG_DET (Log Detector), VARAMP (Variable Gain Amplifier), !" ANTC (Coupled Antenna), PATH (Antenna Path) !" Improved range warnings

FILTER, A/FILTER, M/FILTER

!" Integrated into GENESYS framework !" Allows viewing of response while designing filter !" Allows modification of filter even after integration with larger circuit. For example,

you can tune the order or bandwidth of a filter and watch a SPECTRASYS simulation, which uses that filter update as you tune.

!" Can now synthesize a filter by right-clicking on a part in SCHEMAX LAYOUT

!" Added GDSII import !" Added GDSII export !" Added Step and Repeat function !" Added ability to edit schematic part parameters from within LAYOUT (on right

button menu) !" Improved Gerber and DXF import

SCHEMAX

• Added Fit To Page and Center Schematic menu commands • Added Synthesis tab to SCHEMAX Part Properties dialog box

o New – disable parts open / shorted o Use any symbol as a sub-network o Easily attach an S-Parameter file to any part

• Expanded System toolbar (many new parts) • Local error messages (Orange parts, with right click info)

EMPOWER

!" Improved memory usage HARBEC

!" Added Temperature !" More efficient multi-tone

Optimization and Yield

!" Can now disable Opt targets Tables

!" Added the ability for Tables to automatically save data to an external file

Changes from GENESYS 8.0

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Ease-of-use Improvements

• Improved Zooming o Mouse wheel, middle mouse button click and middle double click o (Implemented for SCHMAX, LAYOUT, and Graphs)

• Implemented Workspace tree Copy and Paste (on right button menu) • Implemented Workspace tree Drag and Drop to copy and paste workspace items • Added Help buttons to dialog boxes • Improved Setup Variables dialog box (less confusing) • Improved DisCo symbols (for printed output) • Improved toolbar icons

Changes from GENESYS 8.0

With GENESYS 8.0, Eagleware upgraded the following synthesis modules: !" EQUALIZE is now embedded in Genesys and has a new automatic mode !" MATCH is now embedded in Genesys, has an all-new user interface which

allows for immediate response viewing !" OSCILLATOR is now embedded in Genesys and supports custom oscillator

types !" S/FILTER now supports distributed designs !" Advanced T/LINE is embedded in Genesys and provides automatic conversion of

schematics to/from electrical to any Genesys process Here are some highlights of the enhancements from Genesys 8.0: New Linear Models

• Lange Coupler • 4, 6, 8 finger configurations • Linear models and layouts for EM simulation • Full set of parameters: width, spacing, length of fingers, substrate, etc.

• Coplanar Waveguide • Single lines with or without lower ground plane • Supports several discontinuities

• Striplines • Offset-coupler lines (two horizontal lines, broadside coupled) • Offset stripline (single line not centered between ground planes)

• Suspended & Inverted Microstrip • Suspended (line between two horizontal ground planes) • Inverted ( conductor between dielectric and ground plane)

• Square Coaxial Lines • Square outer conductor with square or round inner conductor

• Negation • One and two port negation elements are used with an s-parameter file to

remove the effects of a circuit element or to de-embed a port. • Signal Control Modules

What’s new in Genesys 8.1

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• RF Circulators • RF Isolators • RF Couplers • RF Splitters/Combiners • RF Switches

SCHEMAX - Schematic Capture

!" DisCos - smart discontinuity models !" Custom units !" Right mouse button menu !" Symbol editor

Test Link - Instrument Interface

!" Read data from a wide range of test equipments Simulation

!" Nonlinear noise & linearized noise of nonlinear devices !" Increased non-linear simulation speed !" Optimization limits !" Tuning to standard values

Graphing

!" Wizard to build plots (parameters, equations) !" Improved marker readouts

Layout

!" X-ray and hollow drawing modes !" Right mouse button menu !" Gerber improvements !" Parts lists and Bill of Materials !" Ruler Tool !" Pour and Polygon editing improvements !" User selectable layouts

Support

!" Automatic code renewal from the web !" Optional subscription service

Chapter 2: FILTER

Overview

Note: Additional documentation for FILTER is given online in the HF Filter Design and Computer Simulation book.

FILTER makes designing L-C filters and delay equalizers a snap. With GENESYS you can simulate the filter performance, customize or optimize the filter and check the effects of parasitics.

FILTER synthesizes many L-C filter types suitable for a wide range of applications. Principle features include:

!" 20 filter topologies !" Topology choices provide for practical realizations and specific application needs !" A wide range of transfer approximations (amplitude and delay response shapes) !" Effective noise bandwidth calculation !" Complete integration with GENESYS

Walkthrough

The FILTER L-C filter synthesis module is integrated into the main GENESYS environment. All synthesis programs design circuits as prompt values are changed.

In this walkthrough, the following filter is designed:

!" 50 Ω source and load terminations !" Chebyshev lowpass filter !" 0.25 dB of passband ripple !" 7th order !" 70 MHz cutoff frequency !" Minimum capacitor configuration

Create a new filter by right-clicking the Synthesis folder in the GENESYS workspace window, and choose "Add Filter". The Create a New Filter dialog appears as shown.

FILTER

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Select Factory Default Values as shown above to load FILTER settings from the original shipped values. Click OK to accept the default name "FILTER1".

The Filter Properties window appears with a schematic and frequency response graph. Your screen should look similar to the one below.

On the Filter Properties Topology tab, select Lowpass as the type, Chebyshev as the Shape, and Minimum Capacitor as the subtype, as shown below.

Walkthrough

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On the Settings tab, enter 50 for the input resistance, 70 for the Cutoff Frequency, 7 for the order, 0.25 for the Passband Ripple, and 0.25 for the Attenuation at Cutoff, as shown below:

Note: In the case of odd order Chebyshev filters, the output impedance is equal to the input impedance. For even order Chebyshev filters, the output impedance will be greater or less than the input impedance, depending on the subtype selected. Certain filter types allow specifying the output impedance independent of the input impedance. For these filters, FILTER requests the desired output impedance.

Since this is an odd order Chebyshev filter, the calculated output resistance is equal to the input resistance. This value is shown with the 3 dB frequency in the text area at the bottom of the Settings tab.

The filter schematic is designed and updated as prompt values are changed. The schematic below represents the desired filter.

FILTER

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The frequency response for this filter is shown below.

The schematic and graph created by FILTER are easily modifiable to customize the design.

The default Q's entered on the Defaults tab are remembered and used until they are changed again. FILTER initially assigns the same Q value (from the defaults) to all inductors and all capacitors. These can be changed by entering the desired Q values directly into the components on the schematic created by FILTER.

The effective Q of resonators (inductor and capacitor combinations) is given by:

For example, an inductor Q of 120 and capacitor Q of 600 results in a resonator Q of 100. The Defaults tab is shown below.

Walkthrough

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FILTER directly computes the lowpass prototype values (often called "G values") for popular response shapes and does not use tables, so any passband ripple greater than zero and less than 3 dB may be chosen. This is true even for elliptic Cauer-Chebyshev filters. The G values calculated for the currently selected filter design are shown on the G Values tab, as shown below.

Note: The cutoff frequency of all-pole filters, such as Butterworth, is normally defined as the 3 dB attenuation frequency. The cutoff of filters with ripple in the passband, such as Chebyshev, is often defined as the ripple value. FILTER allows the user to specify the attenuation of the cutoff frequency for Butterworth and Chebyshev filters. For these filters, Aa is prompted. For normally defined cutoff attenuation, enter Aa equal to the ripple for Chebyshev filters, and Aa equal to 3.0103 dB for Butterworth filters.

FILTER

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The Summary tab, shown below, shows the summation of the G values of the filter. This quantity may be used to estimate the filter insertion loss and group delay of the filter at frequencies well removed from the cutoff.

The "Estimate Order" button on the Settings tab opens a utility for estimation of the required order of a filter based on passband and attenuation requirements. In the figure below, the required attenuation at 0.75 MHz and 2.5 MHz are specified. The required filter order is approximately 8. Also shown are the frequencies for the 3 db attenuation points.

Chapter 3: A/FILTER

Overview

A/FILTER makes designing active filters fast and easy. A/FILTER also includes EQUALIZE for active equalizer synthesis. With a GENESYS simulator, you can simulate the filter performance, customize or optimize the filter, and check the effects of parasitic reactances or finite op-amp parameters, such as unity gain bandwidth.

Note: Several A/FILTER examples with measured results are presented in the Filters section of the Examples manual.

A/FILTER synthesizes many filter types suitable for a wide range of applications. Principle features include:

!" Over 30 filter topologies. Choices provide for practical realization of specific application needs. Many types allow specification of passband gain.

!" A wide range of transfer approximations (amplitude, phase and delay response shapes).

!" Effective noise bandwidth calculation

!" Full integration with GENESYS Environment

Walkthrough

The first design example will be a Single Feedback 7th order lowpass filter with a 0.25 dB passband ripple Chebyshev response. The cutoff frequency is 10 kHz and the filter will have +2dB gain in the passband.

A/Filter is launched by right-clicking on the Synthesis folder in the workspace window and selecting "Add Active Filter." A name for the active filter can be entered next, or the default name can be used by simply clicking OK. You also have the option to use your last saved values or the factory loaded values. The A/Filter dialog box will then be displayed. This is where all of the filter options and parameters are entered.

Under the Topology tab, the filter type, shape, and subtype are set. The Settings tab allows control of parameters specific to the filter type currently selected in the Topology tab. The Options tab allows the specification of input and output buffers, and op-amp parameters, among other non-filter-specific options. The G Values tab allows manual manipulation of the G Values used to synthesize the filters. The Summary tab contains a verbal description of the currently synthesized filter.

A/FILTER

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In the Topology tab in the A/Filter dialog box (shown in the figure above), select Lowpass as the filter type, Chebyshev as the filter shape, and Single Feedback as the filter subtype. Next, click on the Settings tab. Set the Order to 7. Filters up to 21st order may be designed for most types. The suggested range at the bottom of the window gives a reminder of the valid range for the currently selected input.

Next, enter a Passband Ripple of 0.25. A/Filter directly computes the lowpass prototype G values for popular response shapes and does not use tables for these shapes, so any real value less than 3 dB may be chosen for the passband ripple. This is true even for elliptic Cauer-Chebyshev filters.

The cutoff frequency of all-pole filters, such as Butterworth, is normally defined as the 3 dB attenuation frequency. The cutoff of filters with ripple in the passband, such as Chebyshev, is often defined as the ripple value. A/Filter allows specification of the attenuation at the cutoff frequency for Butterworth and Chebyshev filters. For normally defined cutoff attenuation, enter the Attenuation at Cutoff equal to the ripple value for Chebyshev filters, and 3.01 dB for Butterworth filters.

For this example, enter 0.25 for the Attenuation at Cutoff.

Next, for Butterworth and Chebyshev filters, A/Filter prompts for the Cutoff Frequency, i.e. the frequency at which the specified cutoff attenuation will occur.

Enter 0.01 for the Cutoff Frequency. Cutoff Frequency must be specified in MHz, and 0.01 MHz = 10 kHz.

The Resonator R is the desired value for the selectable resistors in the current filter. Resonator C is the desired value of capacitance. Certain filter types allow the user to

Parameters

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specify one or more part values. When this is the case, A/Filter prompts for the value. This can be any valid part value. Not all of the part values are selectable. Some filter types allow selection of resistors, whereas some do not allow any freedom. This is discussed in further detail in the A/Filter Types section.

For this example, enter 10000 for the Resonator R value, and 10000 for the Resonator C value.

The schematic of the filter is shown in the schematic window as it is below.

Parameters

Component Defaults

A/FILTER allows specification of capacitor Q and operational amplifier characteristics. SuperStar then uses these values in the determination of the filter response. To view or change these values, select Components from the Setup menu. Several input boxes are displayed. The first is the desired value for capacitor Q. A new value can be specified, or simply press Enter or one of the vertical arrow keys to move to another field.

The op-amp parameters allow A/FILTER to model virtually any real amplifier by knowing critical operating parameters. The Input Resistance is the series DC input resistance of the amplifier. The Output Resistance is the apparent DC output resistance. GDC is the DC open-loop gain, and the 0 dB frequency is the frequency in MHz at which the amplifier’s characteristic curve yields a maximum gain of 0 dB. Typical amplifier parameters are available from online help in A/FILTER.

Preferences

Most of the filter topologies designed by A/FILTER use a minimum number of components, and do not match to a specified source or load termination. For this reason, the transmission and reflection parameters may behave erratically unless a matching buffer is added at either end. For instance, the Minimum Inductor and Minimum Capacitor types assume a near zero source termination, and near infinite load resistance.

Unless low or high values are specified for the source and load terminations (A/FILTER default) the source sees a mismatch and voltage follower buffers must be added on each port. These buffers add a shunt resistance equal to the source resistance on the source side of the input buffer. A/FILTER does not do this by default, but it can be enabled by selecting the Preferences option from the Setup menu.

A/FILTER

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Two options are available. They are:

1. Zo matching buffer...Matching buffer (follower) with resistance equal to the specified port termination resistance.

2. Voltage follower...Voltage follower with no matching resistor.

These can be placed on either port, or not used at all.

Some filter types have no gain built inherently into their structure. If no gain is allowed in a filter that has been designed but voltage followers are used, A/FILTER can add feedback resistors to these followers in an attempt to provide the requested gain. The preferences box contains four other options to customize the way that A/FILTER selects sections during the filter design process. They are:

1. Allow third order sections

2. Distribute Gain

3. Use simple first order section

4. Reverse order of poles

A/FILTER can design a three pole section using a single op-amp. This is useful since it can eliminate parts from a design, but it does not allow gain. It can, however, be used to simplify the overall filter design for orders greater than two. The section has a high sensitivity to component tolerances, since one element can tune three poles simultaneously. The three pole section allows specification of a single value for all resistors. This provides a greater component flexibility than the two pole section, but does not allow gain. Check the Allow Third Order Sections box if the three pole section should be used in designs.

When a filter contains more than one section which can provide gain, A/FILTER can distribute the required gain evenly among them. This can lessen the strain on each op-amp, and in some cases allow a lower bandwidth amplifier to be used. Check the Distribute Gain box to have the overall gain distributed through the allowed sections.

In odd order filters not using the three pole section, a single inverting amplifier is used to realize the extra pole. This can add an extra gain section, but it adds parts to a design. However, buffering capability is present in the more complex circuit, so a voltage follower on the output is not normally required. Check the 'Use Simple First Order Section' box for A/FILTER to use a single RC section rather than an additional op-amp pole.

By default, A/FILTER places all pole pairs first in the filter cascade. For the real pole to be placed first, or for the pole pairs to be reversed, check the 'Reverse Order of Poles' box. This may be desirable in low-noise design, since most of the gain occurs in the first section with the poles reversed. Even 0dB gain filters will generally amplify the signal in some stages while attenuating it in others, so use this option with caution. When this option is on, the amplifying sections will be first, so the input level must be much smaller to avoid saturating the op-amps in the first stages. For more details on gain levels in individual sections, see Chapter 5.

Chapter 4: M/FILTER

Overview

=M/FILTER= is the GENESYS synthesis program which designs microwave distributed filters. SPICE simulation poorly supports distributed circuits and Touchstone does not include the models required for certain popular microwave filters, so the preferred GENESYS simulator for use with =M/FILTER= is =SuperStar= Professional.

A feature of =M/FILTER= is the ability to absorb discontinuties during synthesis. Independent =SuperStar= response calculation verifies the synthesis process.

Note: The book HF Filter Design and Computer Simulation also includes additional information on filter theory, elements and a variety of practical microwave filter structures.

The principal features of =M/FILTER= include:

!" Lowpass, highpass, bandstop and a wide range of bandpass filter types

!" Five different implementation processes including simple electrical, microstrip, stripline, slabline and coaxial.

!" Full Integration with GENESYS environment

!" Automatically displays layout or schematic on screen

!" Allows specification of units, size and cross hairs for final board layout

Walkthrough

The M/FILTER distributed filter synthesis module is integrated into the main GENESYS environment. All synthesis programs design circuits as prompt values are changed.

In this walkthrough, the following filter is designed:

!" 50 Ω source and load terminations !" Chebyshev lowpass filter !" 0.25 dB of passband ripple !" 7th order !" 2 GHz cutoff frequency !" Stepped impedance configuration !" Microstrip

Create a new filter by right-clicking the Synthesis folder in the GENESYS workspace window, and choose "Add MFilter" as shown below. The Create a New MFilter dialog appears.

M/FILTER

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Select Factory Default Values to load the original shipped prompt values. Click OK to accept the default name "MFilter1".

The Select Layout Settings File dialog appears. Select Standard.ly$ in the selection box to use default properties for the layout which will be created. Click OK to open the MFILTER program.

The Substrate Needed dialog appears. This dialog indicates that a substrate definition must be created before a physical filter is designed. Click OK to create a substrate definition.

Walkthrough

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The Edit Substrate dialog appears. This dialog allows custom substrate definitions to be created. Click Load from GENESYS Library to load a predefined substrate.

The Load Substrate dialog appears. Select "Rogers RO3003 1/2 oz ED 30 mil" as shown below and click OK.

M/FILTER

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The substrate information is loaded and displayed in the Edit Substrate box as shown below. Click OK to open the M/FILTER program and design a filter using this substrate.

M/FILTER opens and displays the layout, schematic, and frequency response as shown below. The schematic is hidden behind the layout in this figure.

Walkthrough

27

On the Topology tab in the M/FILTER window, enter the following settings:

M/FILTER

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On the Settings tab in the M/FILTER window, enter the following settings:

For this type of filter, the output resistance is uniquely defined by the input resistance and the specified parameters.

Min Z is the minimum impedance you feel is practical and Max Z is the maximum impedance you feel is practical. More extreme values result in more ideal responses before optimization and better stopband performance.

For information on the Estimate Order utility, see the Walkthrough in the FILTER section

Ensure that Create a Layout is checked on the Options tab, and click the Select Manufacturing Process button.

Walkthrough

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The Convert Using Advanced TLINE dialog appears as shown below. Make the selections shown and click OK. (For information about using Advanced TLINE, see Advanced TLINE Overview.)

Click OK to close the Advanced TLINE dialog and design the filter using the new settings.

FILTER directly computes the lowpass prototype values (often called "G values") for popular response shapes and does not use tables, so any passband ripple greater than zero and less than 3 dB may be chosen. This is true even for elliptic Cauer-Chebyshev filters. The G values calculated for the currently selected filter design are shown on the G Values tab, as shown below.

M/FILTER

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Note: The cutoff frequency of all-pole filters, such as Butterworth, is normally defined as the 3 dB attenuation frequency. The cutoff of filters with ripple in the passband, such as Chebyshev, is often defined as the ripple value. FILTER allows the user to specify the attenuation of the cutoff frequency for Butterworth and Chebyshev filters. For these filters, Aa is prompted. For normally defined cutoff attenuation, enter Aa equal to the ripple for Chebyshev filters, and Aa equal to 3.0103 dB for Butterworth filters.

You have now told M/FILTER that you wish to design a seventh-order stepped low-pass filter, with a cutoff at 2 GHz.

GENESYS automatically computes and displays the new layout, schematic, and frequency response as parameters are changed in M/FILTER. Notice that S21 is plotted using the left scale and S11 is plotted using the right scale. The cutoff frequency is shown center-graph by default. Click the Optimize button at the upper-right of the M/FILTER window to begin optimizing the filter to give the best frequency response.

The dotted lines indicate the frequency response using the pre-optimized values, whereas the solid responses show the new filter response using optimized values. After several rounds, improvement halts. Press ESCAPE to stop the optimization. The screen should look similar to the figure below.

The filter design is now complete. For information on creating an electromagnetic simulation for the automatically created layout, see the EMPOWER manual.

Chapter 5: Advanced TLINE Operation

Overview

Advanced TLINE is a time saving tool that allows the user to convert an existing electrical or physical transmission line topologies into 1 of 13 other electrical and physical transmission line topologies. The conversion takes into account changes in substrates, chamfered corners, symmetric steps, and transmission line discontinuities.

For more information, see the following topic: Advanced TLINE Dialog Box and Advanced TLINE Example.

Advanced TLINE Example

In this example an electrical model of a Hairpin filter will be created. Advanced TLINE will be use to convert the electrical schematic to a Microstrip physical schematic and a Stripline physical schematic from which layouts can be created for both of these topologies. A second substrate will be added and a new Hairpin filter will be created from this substrate.

Note: This example assumes that you are familiar with drawing schematics and entering parameters.

The figure below shows the original electrical schematic and the Advanced TLINE converted physical schematic from which the layout was derived.

Original Electrical Schematic

Converted Physical Schematic

Advanced TLINE Operation

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Completed Hairpin Layout

To create this Hairpin filter layout:

1. Create a new workspace by selecting “New” on the File menu.

2. Enter the following electrical schematic (Sch1) of the 2 Pole Hairpin filter using ten TLE models and one CPL model. Enter all of the model parameters as specified in the following diagram.


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Note: The physical orientation of all of these transmission line elements must be as shown in the above diagram so that GENESYS will automatically be able to determine the correct type and orientation of each DisCo (discontinuity). This only applies if DisCos are used in the Advanced TLINE conversion.

3. Add a second schematic (Sch2). Copy the contents of schematic Sch1 (Ctrl+A to Select All and Ctrl+C to Copy) to the newly created schematic Sch2 (Ctrl+V) to paste.

4. Add a Linear Simulation (Linear1). Use the following parameters: Type of Sweep: "Linear: Number of Points", Start Freq (MHz): 1650, Stop Freq (MHz): 2150, and Number of Points: 21.

5. Add a Rectangular Graph (Graph1). Select "Linear1.Sch1" for the Default Simulation/Data to graph the Linear Sweep of the Electrical Hairpin schematic. Specify S11 and S21 measurements. The response should look as follows:


34

6. Add a substrate to be used for the Microstrip. Right click on the "Substrates"

folder and select "Add Substrate". Fill in the following substrate parameters:

7. Select the Hairpin electrical schematic (Sch2).


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Note: Advanced TLINE will convert the entire selected (or active) schematic or ONLY the selected components in the selected schematic. If no elements have been selected in the active schematic then the entire schematic will be converted.

8. Select "Convert Using Advanced TLINE..." on the schematic menu. The Advanced TLINE dialog box will be opened.

9. Select the dialog information as follows:

then click OK.

10. If a substrate HAS NOT been defined the following dialog appears:

and the user is given the opportunity to define a substrate before the conversion is completed. After this dialog is closed the Edit Substrate dialog box will appear.

11. Once Advanced TLINE has finished its conversion the the electrical schematic will be replaced with a physical schematic that looks like:


36

Notice that DisCos (discontinuities - round elements) have been placed onto the schematic at the appropriate discontinuity points (Automatically add DisCos checkbox) and that the physical lengths of the adjoining transmission lines have been adjusted to account for each discontinuity (Absorb DisCos, preserving circuit response when possible checkbox). For additional information on DisCos see Using Distributed Elements in the Users Guide.

Note: The orientation of the DisCos is based on the physical orientation of the transmission line elements in the original electrical schematic file. DisCo elements can be added manually by right clicking on the appropriate node and selecting the corresponding menu item.

12. Add a Rectangular Graph (Graph2). Select "Linear1.Sch2" for the Default Simulation/Data to graph the Linear Sweep of the Physical Hairpin schematic. Specify S11 and S21 measurements. The response should look as follows:


37

13. Add a layout (Layout1) to the Designs/Models folder. See Creating a Layout for

more information. The Layout Properties dialog box appears:


38

Specify the Design (Sch2 Only), Units, and Box Settings as shown above. Click OK.

14. A layout will appear with randomly placed transmission line elements. To group these elements in the shape of a Hairpin filter select all of the parts in the layout (Ctrl+A). Then select "Connect Selected Parts" from the main layout menu. The connected parts will now look like a Hairpin filter but the filter will not be centered on the PWB. To center the filter on the PWB select "Center Selected on Page" from the main layout menu.

15. The Hairpin filter should now look like:

15. An EM simulation can be created, EM ports can be placed on the layout, the grid

can be adjusted, and an EMpower run can be made.

16. Advanced TLINE makes the job of changing the substrates real easy. To do this create a new substrate and load the "Rogers RO4003 1oz ED 32 mil" from the GENESYS Library. Click OK.


39

17. Select the previously converted Hairpin schematic (Sch2).

18. Select "Convert Using Advanced TLINE..." on the schematic menu. The Advanced TLINE dialog box will be opened.

19. Select the new substrate and verify that the remaining parameters in the dialog box are as follows:


40

then click OK.

17. The new physical schematic with the new substrate now looks like:

18. Clicking on the layout (Layout1) will show the new microstrip lines based on the

new substrate. Step 14 should be repeated and the Box Width and Height should be readjusted to fit the new wider Hairpin filter.

19. The layout now should look like:

Advanced TLINE Dialog Box

41

Advanced TLINE Dialog Box

To open: select the "Convert Using Advanced TLINE..." item on the schematic menu.

Note: By default all transmission line elements in the schematic will be converted unless the user manually selects the transmission line elements to be converted.


42

Process - Specifies the type of transmission line that the currently selected schematic transmission line elements will be converted to.

Substrate - Defines the Substrate to be used for the conversion. Note: If a substrate has not been defined when OK is pressed the user will be given an opportunity to select or create one.

Unused - This is a variable parameter that will changed based on the selected Process. Specifics of this parameter can be found in the TLINE section of the manual.

Via Hole Radius - Defines the via hole radius to be used in the conversion.

Conversion Frequency - Defines the frequency for the match of performance characteristics during conversion.

Automatically Add DisCos - Discos will automatically be added to the schematic if necessary.

About Discos - Brings up Disco help.

Use chamfered corners - Chamfered corners will be used on all corners.

Use symmetric steps - All steps in width of adjacent transmission lines will be centered.

Absorb DisCos, preserving circuit response when possible - Compensates the necessary line lengths to account for all discontinuities.

See also Coax, Square Coax, Coplanar,Coplanar with Ground, Microstrip, Inverted Microstrip, Suspended Microstrip, Slabline, and Stripline for additional information

Chapter 6: TESTLINK

TESTLINK Walkthrough

The purpose of the TESTLINK feature of GENESYS is to import data from instruments. This allows measurements to be compared with the models which may have been used to develop the network being tested. Consider the case of a two port network being tested with a network analyzer. Typical device data is available in the TESTLINK demo mode. If the demo mode is selected when TESTLINK is installed, then TESTLINK can be exercised as if the PC were connected to an instrument.

Under Simulations/Data select: "Add TESTLINK"., using the name "TestLink Data". For instrument select: Network Analyzer. For Instrument, use any model. Then under Outputs, add a Rectangular Graph. Enter: S11, S12, S21, S22. Right click on "TestLink Data" on the workspace tree and select "Transfer All". A dialog box appears for each of the four traces, click O.K. for each. Another way of transferring data is to open the TestLink dialog box and using the "Get" or "Transfer All" buttons. The resulting graph is as shown below.

This data can also be used in Equations or in Optimization Targets, such as: TestLink Data.Data.db[s11] for the magnitude of s11 in db. For example, under Equations in the Workspace tree, enter "Using TestLink Data" on the first line and Error = .DB[s11] - .DB[s22]. Right click on the Outputs in the workspace tree and select: Add a Rectangular

TESTLINK

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Graph, enter a name. In the dialog box, make sure the Data Source is Equations, then enter "Error" on the first line. Select O.K. The error between s11 and s22 is then plotted.

Another use is in a schematic as two port element. There are currently two approaches. The first is to create an SPA element where each of the components is an element of the TESTLINK data. This approach is shown in the schematic below.

TESTLINK Walkthrough

45

If the data is updated by getting a new set of data from the instrument, the data in this element will be automatically updated. The data from the schematic is plotted along with the original TESTLINK data. Note that the two plots are essentially the same.

The second approach is to generate an s-parameter data file with the TESTLINK data. From the FILE menu, choose "Write an s-parameter file", and enter an appropriate name

TESTLINK

46

such as "Measured Data". Under Source of data select: TestLink.data". In a new schematic (Sch2), select "two port" from the Linear Toolbar, and add to the schematic as shown. Under file, "Browse" and find the "Measured Data" file previously generated. Enter in the space provided.

The resulting s-parameters are again the same as the measured data.

The only drawback to the second approach is that if new data is downloaded from the instrument, the file must be regenerated.

TESTLINK Instrument Interface Overview

Data from Network Analyzers, Spectrum Analyzers, and Oscilloscopes can be read into the GENESYS environment for analysis and display. The interface is called "TESTLINK" and is activated from the workspace tree by right-clicking on "Simulations/Data" and adding "TESTLINK". This brings up the TESTLINK dialog box.

Note: You must separately install SoftPlot (supplied with GENESYS TESTLINK) to use TESTLINK.

TESTLINK Instrument Interface Overview

47

Instrument Type - This is the instrument type. Available choices are "Network analyzer" for reading S-Parameters, "Spectrum Analyzer" for reading a power spectrum, and "Oscilloscope" for reading a time-domain waveform.

Instrument - This is the specific instrument model that can be selected for the specified instrument type.

Use Default GPIB Address - If this box is checked, the last successful address for that instrument will be used.

GPIB Address - specifies the GPIB address for the instrument.

Number of Ports - For network analyzers, specifies the number of ports to be measured. For example, if number of ports is 2, then S11, S21, S12, and S22 can be measured. For other instrument types, specifies the number of traces to measure.

Port Impedance - Port impedance of the selected instrument.

Accumulate Data - If clicked, then TESTLINK will save each set of data. Plotting data on a graph will show multiple traces with all data accumulated.

Pause between each trace - If checked, TESTLINK will pause before transferring each trace's data, allowing you to setup your instrument.

Transfer All - Transfers all data traces sequentially into TESTLINK. This is the equivalent of pressing all of the "Get" buttons in sequence.

Clear Data - Erases all transferred data.

Trace Setup Grid

Trace - For Network analyzers, always shows S11, S22, etc. For other

TESTLINK

48

instrument types, this field can be edited and is used to give convenient names to your data.

Source - Allows to specify which instrument channel contains the data for this trace. Additionally, for Network Analyzer, options are provided to make one S-Parameter equal to another, or to make an S-Parameter always zero. This is convenient for passive networks, for example, making S21=S12.

Get - Pressing this button transfers only this trace. Often, it will be more convenient to press the "Transfer All" button at the bottom of this dialog.

TESTLINK Hardware Interface

Set-up:

1. Connect PC to measurement instrument, such as an oscilloscope, network analyzer, or spectrum analyzer using a GPIB card or RS-232 port. A partial list of supported instruments is found below. There is no limit to the number of instruments. The instruments can be daisy-chained or connected in a “star” configuration. Verify the proper operation of the PC / instrument communication using the software supplied by the interface card manufacturer. A list of available GPIB interface cards is also provided.

2. Load the GENESYS software on the PC with TESTLINK option. Then insert a TESTLINK icon on the workspace tree and transfer the data into the GENESYS workspace. Then compare simulated versus measured data or use the data as models in larger simulations. See the TESTLINK walk-through for details on using TESTLINK data in simulations, equations, and other analyses.

HARDWARE REQUIREMENTS

PC Requirements:

Minimum System Requirement: Same as GENESYS

GPIB card: National Instruments: type PC-IIA, PC-AT, PC-PCMCIA, PC-USB

Agilent/Hewlett-Packard: HP82335, HP82340, HP82341, HP82350

ComputerBoards Inc.: GPIB card, type ISA-GPIB, ISA-GPIB/LC, ISA-GPIB-PC2A, PCI-GPIB, PCM-GPIB

ines: GPIB-PCMCIA, GPIB-PCI card

Note – TEST LINK can also use RS-232 port if the instrument supports it.

TESTLINK Hardware Interface

49

Network Analyzers:

Agilent: E835XA PNA Series

Anritsu Wiltron: 360, 371xx/372xx/373xx, MS462XX

Hewlett-Packard: HP8510, HP8711-14B/C, HP8751/52/53, HP8720 Series, HP4195, HP 4396A Network/Spectrum Analyzer, HP3561A, HP35660 Dynamic Signal Analyzer, HP4291A Impedance Analyzer, HP8757 Scalar Analyzer

Marconi Instruments/IFR: 6210 reflection analyzer 6200, 6800 series Microwave Test Sets

Rohde & Schwarz: ZVR/ZVC/ZVM series

Spectrum Analyzers:

Agilent/HP: E44XXA/B ESA-E, -L, PSA Series

Advantest: R3261/3361, R3265/3271, R3267/3273 series

Anritsu: MS2602, MS2650/60, MS612A, MT8801B Radio Comms Analyzer

Hewlett-Packard: HP8590 series, HP8560/1/2/3, HP8566B, HP8568A/B, HP3585, HP4195, HP8542E/HP8546A EMI Receiver

IFR: AN940 series, IFR 2398/2399

LG Precision: SA-9270/SA-7270

Marconi Instruments: 2380 and 2390 series, 2945 series (spectrum analyzer display only) 2965 series (graphical displays only)

Rohde & Schwarz: ESMI, FSA/B/M, FSE, FSP, FSIQ series, CMS50 series (spectrum analyzer display only) CMD55/65, CMU200 Radio Test Sets

Tektronix: 2711/2712

Oscilloscopes:

Fluke/Phillips: PM3350/55/65/75 Series, PM338XA/PM339XA Series

Hewlett-Packard: HP54120, HP54200A, HP54502A, HP54520C, HP54540C, HP54600 A Series, HP54645A/D, HP54750, HP548XXA Infinium Series, HP83480

LeCroy: LC300/LC500/9300/WaveRunner Series

Tektronix: TDS 200 to 800 series, 2432A, 7D20 Digitizer

Yokogawa: DL1520/DL1540 Series

Chapter 7: Workspace Window

Note: Be sure to try right-clicking in the Workspace Window. This is the easiest way to do most operations within GENESYS.

The GENESYS Workspace Window is an "organizer" for all loaded files. An example is shown below:

The Workspace Window contains a common Windows control known as a tree control. This is the same type of control used in the Windows Explorer, and in many email browsers.

A tree control is a window that displays a hierarchical list of items, such as the entries in an index, or the files and directories on a disk. Each item consists of a label and an optional bitmapped image, and each item can have a list of subitems associated with it. By clicking an item, the user can expand or collapse the associated list of subitems.

Workspace Window

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New in Version 8.1! To copy an item:

!" Right-click the item and choose "Copy"

!" Right-click again and choose "Paste", or

!" When multiple workspaces are loaded, use the left-button to drag the item from one workspace to the other

Tip: You can copy or drag an entire folder from one workspace to another, by selecting the folder instead of a sub-item.

To show any workspace item's menu:

!" Right-click the item in the workspace tree.

To create a new item:

!" Right-click the main node (folder) in the workspace tree.

!" Choose the desired item to create (For example, to create a new schematic, right-click the Designs node and choose "Add Schematic".)

To open an item (display its window):

!" Double-click the item, or

!" Select the item and press "Enter". To open or close a folder (Designs, Simulations/Data, etc.):

!" Double-click the folder, or

!" Click the "+" or "-" to the left of the folder, or

!" Select the item and press Enter. To delete an item:

!" Right-click the item and choose "Delete", or

!" Select the item and press the Delete key. To rename an item:

!" Left-click the item's name to select it and then slowly click it again (do not double-click it), or

!" Right-click the item and choose "Rename".

Note: The main nodes in the tree control (Designs, Equations, etc.) cannot be deleted or renamed.

Chapter 8: SCHEMAX

Schematic Element Properties

To open: Double-click any part in SCHEMAX, select a part and press Enter or F4. This dialog box is customized to match the currently selected part. Usually, one or more settings may be unavailable simply because the current part does not need that particular setting.

Parameters Tab

An example of the Parameters tab is shown below:

Model Parameters

Name - The name of the model parameter.

Description - A long description of the parameter.

Value - Specifies the actual parameter value.

SCHEMAX

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Units - The units that the parameter is specified in.

Default - If available, a default value for the parameter.

Show - When checked, this parameter is displayed (unless over-ridden by the global settings: Show Designators or Show Part Text.

Options - If available, varies by part.

Substrate - If available, specifies a substrate for the part to use.

Spice Information - Optional, enabled in Global SCHEMAX Options

Device - The SPICE device that is used when a SPICE net-list is exported.

Parms - Extra parameters for the SPICE model.

Output - The SPICE line that would be exported.

Tip: If you will be exporting a spice file, be sure to enable SPICE Details so that you can see and override spice translations (as needed) in the part dialog box.

Buttons

Browse - If available, allows the FILENAME parameter to be specified by browsing via a File Open dialog box.

Model - Allows you to change the model associated with the currently selected part. More Info.

Symbol - Allows you to change the symbol associated with the currently selected part. More Info.

Layout - Standard, Replace Part with Open or Short. More Info.

Show All - Checks all of the Show check boxes.

Hide All - Unchecks all of the Show check boxes.

Show Defaults - Sets all of the Show check boxes, based on the default settings for the part.

Element Help - Brings up element help on the currently selected part.

OK, Cancel - Accept or cancel setting changes.

Help - Brings up the help entry that you are currently reading.

Schematic Element Properties

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Simulation Tab

The Simulation tab is used to override the parameters on the Parameters tab. This is an advanced technique which is often used to refine a part in SPECTRASYS. When a part is first placed, the parameters are entered as usual. After the initial circuit is created and simulated, right click on a filter, for example and synthesize a custom circuit for the filter. Then, double-click the part in the system schematic, select the Simulation tab and use the radio buttons to select the parameters to use for simulations.

Radio Buttons

Use Parameters and Model as Entered - Usual setting; use the values from the Parameters tab for simulations.

Disable Part for All Simulations (Open Circuit) - The part is ignored during simulations (as an open circuit). This is shown in SCHEMAX as a purple X over the part.

Disable Part for All Simulations (Short Circuit) - The part is ignored during simulations (shorts ALL terminals together). This is shown in SCHEMAX as a green X over the part.

SCHEMAX

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Use Subnetwork or EM Simulation - Use the selected design or simulation from the current workspace instead of the values on the Parameters tab.

Use N Port Datafile - use the data file specified instead of the values on the Parameters tab. The number of ports combo box selects the number of ports that are defined in the data file specified.

Buttons

Browse - Brings up the File Open dialog box.

Note: The part on the schematic shows the status of the Simulation settings as follows: When a part is disabled, the part will be drawn with an X over it and the text parameter block will be grayed. The X will be drawn in PURPLE if the circuit is OPEN and GREEN if the circuit is SHORTED. When a subnetwork is used, the part will have SUBNET: <name> displayed as the first parameter and the rest of the parameters are grayed. When a datafile is used, the part will have DATAFILE: <filename> displayed as the first parameter and the rest of the parameters are grayed. The simulation parameter line will displayed if the designator display is enabled, either on the Parameters tab or in Tools / Options / SCHEMAX Global Options.

Schematic Part Layout Options

If you do not want a schematic part to appear in LAYOUT:

1. Open the schematic part’s dialog box (double-click on the part).

2. Click the Layout button. The dialog box shown below appears.

3. Choose the desired option, and click the OK button.

Tip: Often in RF circuits, you want to model packaging and/or component parasitics. This is done by placing lumped elements in series or parallel with the actual component. However, you don’t want these parts to appear on the layout. For capacitors, simply choose “Replace part with open”. For inductors and resistors, choose “Replace part with short”.

Zooming

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Zooming

There are three ways to zoom on a schematic:

1. Using the toolbar Zoom buttons:

Zoom In Zoom Out Zoom To Fit Zoom To Page Zoom To Rectangle

2. Using the Middle mouse button and/or Scroll Wheel:

Zoom In Middle button (default, can be changed in SCHEMAX global options)

Zoom To Fit Middle button double-click Zoom In Mouse wheel forward Zoom Out Mouse wheel back Using the keyboard:

Zoom In Ctrl + Page Up + (plus key) Zoom Out Ctrl + Page Down - (minus key) Zoom To Fit Ctrl + Home Z Zoom To Page Ctrl + End Zoom To Rectangle X Zoom To Fit With Margin Shift + Z

NOTE: As you zoom out, SCHEMAX will selectively skip drawing excessive details. This is intentional; it is similar to using a street atlas, a state map, and a world map. Only the appropriate details are shown at a particular zoom setting. Text that would obscure your schematic is dropped and the remaining (more important) text is drawn extra large so that it is still readable even though you are zoomed out. Only the on-screen view is modified, the actual schematic is unchanged.

Chapter 9: LAYOUT

Step And Repeat

Selecting Step And Repeat from the Layout menu brings up the following dialog.

Rows - Number of rows to repeat.

Columns - Number of columns to repeat.

Note: The original selection is included in the step and repeat pattern. (In other words, a 1 row by 1 column step and repeat has no effect.)

X Offset - Distance to move in the X direction before placing a copy of the selection.

Y Offset - Distance to move in the Y direction before placing a copy of the selection.

Use IC Pin Order - Arranges pads and port numbers for DIPP style integrated circuit packages. (In a U pattern.)

GDSII Setup

Selecting Export/GDSII File from the File menu brings up the following dialog.

LAYOUT

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Scale - Scales the layout objects by the indicated factor. The default is 1 (actual size).

Tolerance - Curves are drawn as a series of line segments. This number specifies the maximum deviation from the actual curve for these segments. Smaller numbers give better approximations (smoother curves), but can cause mathematical underflows (and possibly erroneous DXF objects) if below about 1 mil.

Resolve To Polygons -Resolves crossed polygons into a single entity. For example, orthogonal crossed lines could be resolved into a single polygon in the shape of a cross..

Show Drill Holes - Turns on or off the display of drill holes in the DXF file.

Drillhole Layer - Specifies the layer on which to show drill holes. This number is only used if Show Drill Holes is selected (see above).

Chapter 10: Graphs and Tables

Markers

Markers can be added to Rectangular, Smith, and Polar Charts (any graphical output except the 3D graph).

Here is a graph before clicking a data point on the graph to add a marker (using the left mouse button):

Here is the graph after clicking (with a newly placed "standard" marker):

Graphs and Tables

62

Markers are placed on the specific trace you clicked on, but the Mark All Traces mode will display additional markers flags on all the relevant traces of the chart. To mark both traces, click on the Mark All Traces toolbar button:

Whenever a marker is "selected" (currently active marker), the marker text colors are inverted (white on a colored rectangle). The figure below shows two markers. The one on the right is selected.

Fly-over Tool Tips

When the mouse cursor "hovers" over a marker or graph data point, GENESYS will display a "tool tip" pop-up beside the mouse, as shown above. These can be very useful when part of the marker text is obscured or when the value of a data point is needed, but no marker is desired.

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Graphs and Markers Are Customizable

There are many graph and marker options. The vertical lines can be hidden, as can the the Trace Symbols. The marker text can be placed on the right. Use the Graph menu or toolbar to quickly change the graph and marker settings. Titles and annotations can be added (right-click on the chart and select an item from the pop-up menu); graph legends can be moved (just drag them into place).

Note: If you do not like the small circles/squares/triangles which show each data point, you can uncheck "Show Symbols On Trace" on the Graph Menu.

This example demonstrates a less cluttered chart:


GENESYS now has several marker types (which are available for rectangular graphs only): Standard (non-moving, fixed frequency), Peak, Valley, Bandwidth, and Delta (on the left or right). Standard is the normal, non-moving marker style. Peak and Valley markers will automatically track the peaks/valleys of your graph, even while tuning. Delta markers automatically track the position of another marker and are adjusted to the relative offset (dB down). Bandwidth markers are a composite marker (just for ease-of-use); Bandwidth markers are simply Peak markers that drop 2 Delta markers that measure the bandwidth of the peak.

Peak Markers

To place a Standard marker on a graph, just position the mouse over the spot where the marker is needed and click the graph trace (on or near a data point) with the left mouse button. The marker can then be changed to one of the other marker types like Peak, as desired.

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Here's an example of what happens when the red marker from the previous example is changed to a peak marker (notice how the marker travels to the nearest peak):

Delta Markers

To place a Delta marker, select the marker you wish the delta marker to be "relative to" and click the Delta on Left (or Delta on Right) toolbar button. The Marker Properties dialog box can be used to set the "dB Down" value of the new delta marker. Here's an example of a Delta Right maker relative to the first marker:

Notice the delta value (-2.68 dB) is displayed. That's the actual value derived from the simulation data, even though the Delta marker's default dB down of -3.0103 dB was requested. The Delta marker will always be placed on an actual simulation data point. To get the Delta marker value closer to the desired -3 dB down, the number of data points in the simulation should be increased as needed. Since this Delta marker is


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"attached" to a Peak marker, both will track tuning changes in tandem. Also notice that the original marker has automatically been named "M1", so that the Delta marker can reference it.

Marker Names

Markers may be named for reference or documentation purposes. A marker must be named if it is to be referenced by a Delta marker. Bandwidth markers are automatically named in the form BW1, BW2, etc. Other markers are automatically named M1, M2, etc. as shown in the example above. The marker names can be hidden using the marker properties dialog box, however, the name will always be displayed on a tool tip.

Bandwidth Markers

Here's an example of a Bandwidth marker, along with its' associated Delta markers:

Notice that the actual measured bandwidth of 24 MHz is displayed; it is calculated directly from the positions of the two Delta markers (which are both set to -6.0 dB down). As mentioned above, the number of data points in the simulation may need to be increased (so that the Delta markers may be positioned with sufficient precision). The dB down settings of both Delta markers associated with the Bandwidth marker can be adjusted at the same time by setting the Bandwidth marker's properties. The dB down can also be set independently (to different values) by setting an individual Delta marker's properties.

Tip: If you need the bandwidth to based on a fixed center frequency, just place a bandwidth marker normally and bring up properties. (Double-click the marker.) Then change the marker type to Standard and enter the desired frequency. The relative markers will automatically follow the marker to its new location.

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Marker Properties

To open: double-click on any marker on a chart.

Name -The marker's name (which is optional, unless this marker needs to be referenced by a Delta marker).

Mark All traces - When checked, the selected marker will flag all relevant traces, not just the one that was originally clicked on.

Show Name - When checked, the markers name will be drawn on the chart. Marker names are always displayed in the marker's tool tip.

Style - Selects the type of marker.

Marker Placement - Sets the x-axis value (usually frequency) of a Standard marker to the specified value.

Peak/Valley Aperture - Controls the "window" that is used to detect peaks and valleys and reject noise spikes. Lower numbers will enable the detection of smaller peaks, but may also detect a local spike as a peak, instead of skipping over it. The Default button will restore the factory default values for the aperture. This is a "global" setting that affects all graphs in GENESYS.

Delta Marker Settings - Controls the placement of a Delta marker. Relative offset is usually negative (to measure dB down), but can be positive as well. The Relative To combo box selects the name of the marker that the Delta marker is measured from.

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Keyboard commands

• Tab - Cycles through markers, selecting each one in turn. If the last marker is selected, Tab unselects it. If no marker is selected, Tab selects the first marker

• Shift+Tab - Selects the previous marker

• Enter - Brings up marker properties dialog box, unless there is no marker selected, in which case the graph properties dialog box is displayed

• Delete - Deletes the currently selected marker

• Shift+Delete - Delete all markers. (Prompts with a yes/no conformation box before actually deleting the markers.)

• Arrow keys - The up, down, left, and right arrow keys have several functions, based on the currently selected marker's style

• Standard marker - The reference frequency is moved left or right on the graph

• Peak marker - The marker jumps to the next peak (if any)

• Valley marker - The marker jumps to the next valley (if any)

• Bandwidth marker - The relative markers are moved to increase or decrease the bandwidth. This changes the delta values of the "child" relative markers, so each arrow key does not necessarily move the marker by a single data point

• Delta markers - The relative delta is increased or decreased. This just changes the dB Down value of the marker, so each arrow key press does not necessarily move the marker by a single data point

• Ctrl+Arrow keys - Pans (scrolls) the chart up, down, left, or right

• Shift+Arrow keys - Moves the marker up or down to the next trace on the graph (if any)

• Ctrl+Shift+S - Changes the current marker's style to Standard

• Ctrl+Shift+P - Changes the current marker's style to Peak

• Ctrl+Shift+V - Changes the current marker's style to Valley

• Ctrl+Shift+B - Changes the current marker's style to Bandwidth

• Ctrl+Shift+L - Changes the current marker's style to Delta Left

• Ctrl+Shift+R - Changes the current marker's style to Delta RightMarkers can be manipulated through the keyboard; here is a list of commonly used commands:

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Mouse Actions

!" Left-Click - Create a new Standard marker

!" Shift+Left-Click - Create a new Peak marker

!" Ctrl+Left-Click - Create a new Valley marker

!" Ctrl+Shift+Left-Click - Create a new Bandwidth marker

!" Left-Button-Double-Click - Display Marker Properties for the selected marker

Markers can be selected by either by clicking on them, or by cycling with the Tab key.

Tip: You can also use Shift+Left-Button to place a PEAK marker, Ctrl+Left-Button to place a VALLEY marker, and Ctrl+Shift+Left-Button to place a BANDWIDTH marker (with its' associated left and right delta markers).

Zooming On Charts

Rectangular, Smith, and Polar charts can be zoomed in or out using the Main GENESYS Toolbar. Normally only the X-axis (on rectangular charts) is zoomed. Hold down the Ctrl key to also zoom the Y-axis. Depending on the particular circumstances, some of these buttons may be grayed out.

!" To zoom in, click the Zoom In button ( ), or press the + (plus) key; Ctrl+Page Up may also be used.

!" To zoom out, click the Zoom Out button ( ), or press the - (minus) key; Ctrl+Page Down may also be used.

!" To maximize the display, click the Maximize button ( ), or press Ctrl+Home. This zooms-to-fit all traces.

!" Zoom to the chart boundaries by clicking the Zoom To Page button ( ), or press Ctrl+End.

!" To zoom to a rectangular area, click the Zoom To Rectangle button ( ).

!" Clicking the middle mouse button also zooms the graph in. Double-clicking the middle button does a complete zoom out.

!" The mouse wheel zooms the graph in or out.

Tip: Use Ctrl+LeftArrow, Ctrl+RightArrow, Ctrl+UpArrow, and Ctrl+DownArrow to pan (scroll) charts.

Chapter 11: SPECTRASYS (System Simulation) Operation

Overview

SPECTRASYS is a spectral domain system simulator. Because of its unique implementation, it has several advantages over traditional simulators. The main focus of SPECTRASYS is to aid the user is analyzing and optimizing the RF performance of a chosen architecture which consists of two or more RF blocks or elements.

The best way to think about SPECTRASYS is to compare the SPECTRASYS schematic or block diagram to a circuit board and the SPECTRASYS simulation graph to a spectrum analyzer. Just like a circuit board, SPECTRASYS propagates every source and derived spectral component (harmonics, intermods, spurs, etc.) to every node in the system. The graph can then be set to examine the spectrum at any node in the system. Since a channel and a schematic path can be defined, you can examine any one of over 30 spectrum integrated measurements along this user-defined path on a level diagram.

SPECTRASYS has many advantages over traditional system simulators

!" SPECTRASYS is completely integrated into the GENESYS environment and provides the platform that ties all of the synthesis, circuit simulation, layout, electromagnetic simulation, and testing together.

!" Any linear component can be placed in the system schematic along with any of over 45 RF behavioral models.

!" Arbitrary topologies and multiple paths are automatically accounted for.

!" The user can view full spectrums at any node in the system.

!" Frequency dependent VSWR interactions between stages are automatically included.

!" All measurements are channel based and are a result of spectrum integration.

!" Level diagrams can display any of over 30 measurements along any user defined path.

!" The origins and paths of all spectral components on every node can be easily identified.

!" Broadband noise is readily analyzed and processed.

System Models

Linear (Y-matrix) models are created from the behavioral models in SPECTRASYS. These Y-matrix models are used to determine the impedance of each element along the propagating path of the signals. Once the impedance and gain are known, the correct

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node voltage for a given spectral component can be determined for every node for all elements. Using this technique, VSWR interactions are automatically accounted for.

For the system non-linear devices such as the RF amplifier and mixer (RFAMP, MIXERP, and MIXERA), a Y-matrix model is also used to determine the impedance and gain. However, the non-linear parameters of the models such as P1dB, PSAT, IP3, and IP2 are used to determine the non-linear behavior of the model (such as harmonic/intermod generation, mixing, and gain compression).

Glossary

Adjacent Channel – This is a channel that has the same bandwidth as the main channel but center frequency moved up or down by the channel bandwidth.

ACP - Adjacent Channel Power

Channel – The combination of the channel frequency and channel measurement bandwidth. For example, the channel 99.5 to 100.5 MHz would be specified as a channel frequency of 100 MHz with a channel bandwidth of 1 MHz.

Coherent Signal - Two signals which are at a constant phase offset are coherent. In SPECTRASYS, coherent signals must come from the same source.

Desired Spectrum – This is the spectrum that originated along the specified path and flowing in the same direction as the path.

IF – Intermediate Frequency.

IIP3 - Input Referenced Third Order Intercept.

Image Channel – This is the channel defined by the image frequency of the first mixer and the channel bandwidth. For example, the channel 1000 to 1001 MHz would have an image channel of 800 to 801 MHz if an LO Frequency of 900 MHz was specified.

LO – Local Oscillator.

Offset Channel – User defined channel relative to the main channel. For example, an offset channel specified as –50 MHz for a main Channel Frequency of 125 MHz would result in a channel of 75 MHz ± ½ Channel Bandwidth.

OIP3 - Output Third Order Intercept.

LO Side Injection – The relative indication of the LO frequency with respect to the mixer RF frequency. The RF frequency can be either the input or the output of the mixer. For example, if the mixer took a 1000 MHz and down converted it to a 100 MHz IF then an LO frequency of 900 MHz is Low Side LO injection and an LO frequency of 1100 MHz is High Side LO injection.

MDS – Minimum Detectable (Discernable) Signal which is equivalent to -174 dBm/Hz + System Noise Figure + 10 Log(Bandwidth)

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Non-Coherent Signal - Two signals which are not at constant phase offset are not coherent.

Path – The course a signal takes from the source node to the destination node.

RBW - Resolution Bandwidth

SFDR – Spurious Free Dynamic Range

Undesired Spectrum - Any spectrum flowing in a direction opposite of the path direction.

Chapter 12: SPECTRASYS Dialog Box Reference

System Simulation Parameters - General

This page sets the general settings for a SPECTRASYS Simulation. To reach this page, add a System Simulation by right-clicking on Simulations in the Workspace Window.

Design to Simulate - The schematic to use for the system simulation.

Measurement Bandwidth - Specifies the integration bandwidth to use for normal measurements.

Nominal Impedance - The default system impedance.

Recalculate Now - Closes this dialog and initiates an immediate recalculation of the system simulation.

Automatic Recalculation - When checked, enables SPECTRASYS to automatically recalculate the simulation on an as-needed basis.

Sources - Grid that defines the system simulator signal sources.

Name - Name of the signal source.

Port - Port to attach the signal to. More than one signal can be present at a port.

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Description - Description of the signal source.

Enable - Enables the source in the system simulation.

Add - Sources can be added by clicking the Add button.

Edit - Sources can be edited by clicking the Delete button.

Delete - Sources can be deleted by clicking the Delete button.

System Simulation Parameters - Paths

Many measurements require the definition of a path. For an overview of Paths, see the Paths section later in the Simulation manual.

Two functions exist on the “System Simulation” dialog box (shown below) to aid the user in specifying the path. The first is an “Add Primary Paths” button. All possible port-to-port paths will be added to the “System Simulation” for all ports that have a source defined. If no sources have been defined then no paths will be added. If the number of paths becomes very large then the user will be prompted before adding the paths. The second is an “Add Path” button which will prompt the user for the 1) Path Name, 2) From Node, and 3) To Node.

Add All Paths From All Sources - Automatically adds all possible paths between inputs (ports with signal sources) and input/output ports (all ports).

Add Path - Invokes a wizard to assist the manual creation of a path.

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Name - Specifies the path name. This name is used in output graphs to select the path's data.

Path (from Node, thru Node, to Node) - a sequence of node numbers is specified here. The system simulator chooses the shortest path which goes through the specified nodes in order.

Channel Frequency (MHz) - Specifies the path frequency at the input port. This frequency will be modified as the signal travels through mixers. The channel frequency at each node can be found using the CF (Channel Frequency) Measurement.

Delete - Paths can be deleted by clicking the Delete button.

System Simulation Parameters - Calculate

Calculate Intermods and Harmonics - There are 2 different intermod and harmonic calculation modes. They are:

Spectral - This is the normal SPECTRASYS calculation mode which will process all spectrums individually. All identifying spectral origin and path information will be preserved. However, for large numbers of the input carriers, the intermod calculation time will increase.

Spectral (Harmonics Only) - This is the same as the 'Spectral' mode except that no intermods will be calculated, only harmonics. Simulation speed will increase over the normal 'Spectral' mode since only harmonics are being calculated. However, all identifying spectral origination and path information is preserved.


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Calculate Noise - When checked SPECTRASYS will calculate noise. Every component in the block diagram will add noise to the system. A complex noise correlation matrix is used to determine the noise power at each noise. For large number of components the simulation time will increase. Better speed performance can be achieved for a large number of components by disabling noise calculations.

System Temperature - This is the temperature of the entire schematic under simulation. This is the temperature needed to determine the thermal noise power level.

Thermal Noise - Automatically calculated info display that shows the thermal noise power given the specified temperature.

Number of Noise Points - This is the number of points used to represent the entire band of noise. Noise will automatically be created beginning at the frequency specified by 'Ignore Frequency Below' and ending at the frequency specified by 'Ignore Frequency Above'.

See 'Broadband Noise' for additional information.

Calculate IIP3 (TOI) - When checked SPECTRASYS will calculate input and output third order intercept points. Intercept calculations are not based on cascaded equations but rather 2 tones (or even more for the manual mode) with a user defined frequency offset will created at the input to the system. All intercept and intermod levels will be based on the actual tone levels. The cascaded intermod equations make the assumption that the interfering tones are never attenuated. Consequently, erroneous results will result when modeling and entire receiver since the IF filter will typically attenuate the interfering tones. Cascaded intermod equations will give the wrong results for this case.

Manual - When checked the manual IIP3 mode is entered and the user must specify the interfering tones as well as a desired signal in the main channel so the correct in-channel gain can be determined. When unchecked the automatic IIP3 mode is entered and SPECTRASYS will create the two interfering tones and calculate the results. Some of the following additional parameters are needed to complete the automatic IIP3 simulation.

Tone Spacing - (automatic and manual) This is the spacing between the main channel and the first interfering tone, which also happens to be the spacing between the two interfering tones. If more that two tones are used (manual mode only) then this only represents the frequency between the main channel and the first interfering tone.

Input Port - (automatic only) This is the port number where the two interfering tones will be created.

Gain Test Power Level - (automatic only) This is the power level of a signal that will be created within the channel to determine the gain of the main channel. This particular power level is not that critical. However, this level should be low enough so that there is no question that the nonlinear devices such as the amplifiers and

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mixers are operating in the linear range. This in-channel gain is needed to determine the correct input third order intercept point.

2 Tone Power Level - (automatic only) This is the actual power level of both interfering tones.

See 'Calculate IIP3 (TOI)', 'Calculate Intermods', and 'Cascaded Intermod Equations' for additional information.

System Simulation Parameters - Composite Spectrum

Show Contributors - This group is used to break down the entire spectrum into its components. The box must be checked along with appropriate sub-contributors in order to obtain the spectral component origin identification and path information.

Totals - This contributor shows the total power traveling in each direction at the node of interest. For example, if three elements were connected at a particular node then power would be flowing in three different directions. In this particular case a trace representing the power level flowing in each direction would be shown on the composite spectrum plot.

Signals - This contributor shows all source spectral components.

Intermods and Harmonics - This contributor shows all intermod and harmonic spectral components. Spectral component origin identification will only identify intermods and harmonics if this category has be enabled.


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Noise - This contributor shows all noise spectral components. Since every element generates noise once enabled noise can be seen from every element at any given node.

Combine Individual Components - This option will combine all like spectral components into either a Signal, Intermods and Harmonics, or Noise category. Each category will be represented by a different color on the graph. When this option is enabled all spectral component origination and path information is lost.

Individual Components, Above - This threshold is used to show only individual spectral components above the given threshold. This parameter is mainly used to reduce clutter on the graph such as the case when lots of spectral components appear on the same graph. NOTE: This option must be selected in order to view the origination and path of spectral components.

Enable Analyzer Mode - This checkbox enables the analyzer mode and its settings.

Resolution Bandwidth (RBW) - This is the resolution bandwidth of the analyzer. A simple explanation of a spectrum analyzer is a sweeping receiver that displays power in the bandwidth of the IF filter (or Resolution Bandwidth filter). The SPECTRASYS analyzer behaves in a similar fashion where the RBW will determine the actual integration bandwidth.

Filter Shape - This parameter determines the shape of the resolution bandwidth filter that is used for integration.

Brickwall (Ideal) - This filter is an ideal rectangular filter whose skirts are infinitely steep.

Gaussian (to -100 dBc, ± 30 Chan BW) - This bandpass filter is based on a Gaussian three element lowpass filter prototype. Data will be ignored that is farther than 30 channels away from the center frequency. With this 3 element lowpass prototype the attenuation 30 channels from the center will be about -100 dBc.



Randomize Noise - This checkbox enables random noise. Random noise will be added to the total of the noise at a particular node. This will give the user a much

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better idea of what the simulated spectrum would really look like on a spectrum analyzer.

Add Analyzer Noise - This checkbox enables the analyzer noise floor.

Analyzer Noise Floor - When the 'Add Analyzer Noise' is checked analyzer noise will be added to the total noise at a particular node. This parameter will also aid the user in correlating the simulation results with what would actually be measured on a spectrum analyzer.

Limit Frequencies - This checkbox enables frequency limiting of the analyzer mode. This mode is used to restrict the analyzer calculations to a particular frequency range. Only frequencies within this range will make use of the analyzer. This may be useful if the initial frequency range is very large and/or the resolution bandwidth is very small.

Start - The beginning frequency of the analyzer. Stop - The ending frequency of the analyzer. Step - The frequency step size between analyzer data points.

NOTE: The size of the data file may increase depending on the settings of the analyzer mode. Furthermore, as the data file increases in size so does the typical simulation time. As an example, the smaller the resolution bandwidth the more data points are needed to represent the data, the larger the data file will be, and most likely the simulation time will increase.

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Ignore Spectrum - This group is used to limit or restrict the number of spectrums created by SPECTRASYS.

Level Below - All spectrums that are below this threshold will not be created by SPECTRASYS. This threshold should be set to the highest acceptable level if optimal speed is an issue.

Frequency Below (default = 0 Hz) - All spectral components whose frequency is below this threshold will be ignored and will not be created. Likewise, this is the lower noise frequency limit.

Frequency Above (default = 5 times the highest source frequency) - All spectral components whose frequency is above this threshold will be ignored and will not be created. Likewise, this is the upper noise frequency limit.

User Defined Offset Channel - This group is only used in conjunction with the 'Offset Channel Frequency' and 'Offset Channel Power' measurements.

Freq Offset From Channel - This is the relative frequency offset from the current channel frequency.

Measurement Bandwidth - This is the integration bandwidth for the 'Offset Channel Power' measurement.

See 'Offset Channel' for additional information.

Maximum Number of Spectrums To Generate - This group is used to limit or restrict the maximum number of spectrums that will be created by SPECTRASYS.

Max Spectrums - This parameter

Mixer Warning - This group is used to control mixer warnings in SPECTRASYS.

Mixer LO Range - This threshold widow level is used by SPECTRASYS to warn the user in case the mixer LO power level falls outside the specified range. This window applies to each mixer on a case by case basis. The total LO power for the given mixer will be determined by integrating the LO spectrum and then comparing this power level to the 'LO Drive Level' for this mixer. If this power level is outside the 'Mixer LO Range' window then a warning will be issued for this mixer either indicating that the mixer is being starved or over driven.

NOTE: All parameters on this page will support equations and can also be made tunable by placing a question mark in front of the parameter value.

Chapter 13: SPECTRASYS Walkthrough

Creating a Schematic

The first step in creating a SPECTRASYS simulation is to create a schematic. For this walkthrough, we will create the following schematic:

The following circuit elements are used in this schematic:

!" Input: AC Power (PAC), on main toolbar

!" Attenuator, on system toolbar

!" Isolator, on system toolbar

!" Text ("3dB Resistive Pad") on main toolbar

!" Resistors, on lumped toolbar (or press R)

!" Ground and output, on main toolbar (or press G and O)

Note: Your node numbers may vary from the picture above depending upon how you draw the circuit.

This simple circuit will illustrate the capability of SPECTRASYS to include lumped elements (unlike other types of system simulators).

Note: The walkthrough at this point is saved in Examples\SPECTRASYS\Walkthrough\1 - Create Schematic.WSP

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Adding a SPECTRASYS simulation

Next, we will add a SPECTRASYS simulation to the workspace. To add the SPECTRASYS simulation:

1. Right-click on the Simulations/Data tab in the workspace window.

2. Select "Add System Simulation". Accept the name "System1".

3. On the Settings tab, change the "Measurement Bandwidth/Channel" to 1 MHz.

4. Click OK to accept the system simulation parameters. SPECTRASYS will automatically calculate.

5. Right-click on the Outputs tab in the workspace window.

6. Select "Add Rectangular Graph". Enter the name "Output Spectrum".

7. Click "Measurement wizard" to add a new measurement.

8. Select Simulation "System1 (Sch1) Composite Spectrum" and press Next.

9. Select Pport (power at a port/node), select item P2, and press Finish.

10. Click OK to close the Graph Properties dialog box. You will see a simple graph with the output spectrum.

Note: This graph will be easier to read if you make it larger than the default size.

11. To make this graph easier to see and understand, we can switch to spectrum analyzer mode. Double-click on "System1" in the workspace window.

12. Enter 200 MHz for "Ignore Spectrum/Frequency Above".

13. Click on the Composite Spectrum Tab. Check "Enable Analyzer Mode". Press OK. Your graph should now look more like a spectrum analyzer displaying the data, including random noise.

Note: The two total spectrums shown are the spectrums going both directions (Signal + noise from input; thermal noise only from output) at node two. To see only the spectrum going one direction, you can plot the spectrum along a path.

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Note that you can see all of the pieces that combine to make this composite signal, and can use markers and fly-over help to determine exactly where the signals came from. To do this:

14. Double-click on "System1" in the workspace window.

15. Click on the Composite Spectrum Tab.

16. Check "Signals" and "Intermods and Harmonics".

17. Select the radio button "Individual Components".

18. Press OK. You will see a graph like the one below. Placing a marker on the peak will show the source of the signal, and moving the cursor over the marker will give more details. In this case, the green signal started at the input, INP_PAC1, went out the port, and through the listed nodes and elements.

Note: You can zoom in easily on the graph using your mouse wheel or using the zoom buttons on the toolbar.


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Note: The walkthrough at this point is saved in Examples\SPECTRASYS\Walkthrough\2 - Add Simulation.WSP

Level Diagrams

Another tool in SPECTRASYS is the level diagram. To create a level diagram:

1. You must first add a path to the system simulation. Double-click on "System1" in the workspace window.

2. On the "Paths" tab, click "Add Path". Enter the beginning path node 1, and ending path node 2. Enter the name "Forward".

Note: You can also click "Add Primary Paths" to automatically add all paths.

3. Click OK.

4. Right-click on the Outputs tab in the workspace window.

5. Select "Add Rectangular Graph". Enter the name "Level diagram".

6. Click "Measurement wizard" to add a new measurement.

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7. Select Simulation "System1 (Sch1) Path Forward" and press Next.

8. Choose measurement CGAIN (Cascaded Gain) and press Finish. Press OK. You will see a level diagram similar to the one shown below. This diagram shows the total cascaded gain through the system at each node.

Note: The walkthrough at this point is saved in Examples\SPECTRASYS\Walkthrough\3 - Level Diagram.WSP

Tuning Parameters

Like the rest of the GENESYS environment, SPECTRASYS features real-time tuning. In addition to the tuning of element values, all parameters in the system simulation dialog box can be tuned.

1. Double-click "Sch1" in the workspace window to open the schematic.

2. Double-click the input.

3. Click the Tune checkbox on the "AC Power" line to allow tuning of the power in dBm.

4. Click OK to close the dialog box.

5. Double-click "System1" in the workspace window to open the system dialog box.


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6. Type ?1 (question mark followed by 1) in the channel measurement bandwidth.

7. Double-click "Output Spectrum" in the workspace window to open the output spectrum.

8. Tune the input power and bandwidth.

Try tuning the resolution bandwidth to 3 MHz and the input power to 0 dBm. This will allow you to see a good picture of the resolution bandwidth. It also clearly distinguishes the power coming from the input (containing a signal) and the power coming from the output (containing only noise).

Note: The walkthrough at this point is saved in Examples\SPECTRASYS\Walkthrough\4 - Tuning Parameters.WSP

Add an Amplifier

Let's add an amplifier to this circuit. Modify the schematic to look like the following. Don't forget that you can hold Alt down while moving the output to break the connection to the resistor. The RF Amplifier is found on the System toolbar.

1. If you haven't been saving your work, you should save your file now.

2. Open the "Output Spectrum" graph. With the input power tuned to 0 dBm and the measurement bandwidth set to 1 MHz, you should see the following graphs. Note that the noise has risen 20 dB: 15 dB from the amplifier gain, and 5 dB from the amplifier noise figure.

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Note that on the output spectrum, you can see the harmonics. Try passing your mouse over the harmonic to see the level and the source.

Note: The walkthrough at this point is saved in Examples\SPECTRASYS\Walkthrough\5 - Amplifier.WSP

Add a Mixer

Next, we will mix our 100 MHz signal up to 2 GHz using a 1.9 GHz LO and a mixer.

1. Modify the schematic to be:

Note that we changed the units on the LO to GHz. This is very easy to do inside the schematic element dialog box. The mixer is the "Passive Mixer" found on the System toolbar.

2. Looking at the output spectrum, you will see the RF and LO sneaking through. You will also see intermods which were generated.

3. Add another graph called "Input Spectrum". Add measurement P1 from "System1.Composite". You will see that the LO has come back towards the input and is being sent backwards along the RF chain. You will also see that the second harmonic generated at the amplifier comes back towards the input. Seeing these "Sneak paths" is one of the more powerful features of SPECTRASYS.

Note: You must have "Show Contributors/Signals" checked to see the sneak paths below noise.

Note: The walkthrough at this point is saved in Examples\SPECTRASYS\Walkthrough\6 - Mixer.WSP

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Multiple Signals

SPECTRASYS can easily handle many signals simultaneously. We will add more signals to the input port to see the impact on the system.

1. Double-click on the system simulation.

2. Uncheck the "Enable" checkbox on the first source line to disable the 100 MHz signal coming into Port 1.

3. Click on the Add button on the third (empty) source line.

4. Make the source box look like:

5. Press OK to close the Source box.

6. On the first Forward Path line in the Paths tab, enter "100" for the channel frequency. This is necessary because we now have many signals coming into the input, and we need to specify which one to track for the level diagram.

7. Click OK to close the system dialog and start simulation.

8. Zooming in on the input and output will show the following spectra. (You can either use a mouse wheel or the zoom icons on the toolbar.) Notice all of the junk coming in and out of the circuit!


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Note: The completed walkthrough is saved in Examples\SPECTRASYS\Walkthrough\7 - Multiple Signals.WSP

Chapter 14: SPECTRASYS: How it Works

Amplifiers

This section will describe the fundamental operation of how SPECTRASYS simulates RF amplifiers.

General RF and VGA (Variable Gain) Amplifier Parameters

Gain - Small signal low frequency gain. The actual amplifier gain will change according to the gain compression and frequency rolloff of the amplifier.

Noise Figure - Amount of noise added to the circuit by the amplifier. The noise figure is assumed to be flat across frequency. A time domain simulation is performed to determine the noise figure If the amplifier is in compression.

Output P1dB - Output 1 dB compression point.

Output Saturation Power - Output saturated output power.

Output IP3 - Output third order intercept.

Output IP2 - Output second order intercept.

Reverse Isolation - Attenuation from the output to the input. The reverse isolation is assumed to be flat across frequency.

Reference Impedance - Input and output impedance of the amplifier.

Corner Frequency - The frequency at which the input signals will begin to be attenuated by the 'Rolloff Slope dB/Decade' parameter.

Rolloff Slope dB/Decade - The slope of the frequency rolloff specified in dB attenuation per decade in frequency.

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The following diagram is a high level view of the operation of the amplifier.

The amplifier operation is as follows:

1. Determine Total Input Power - The entire input spectrum of the amplifier is integrated to determine the total input power.

2. Add Noise - Noise is added to the input spectrum. The noise may be modified as the amplifier enters compression.

3. Determine Amplifier Gain - The actual gain of the amplifier will depend on how close the amplifier is to compression and saturation. A polynomial curve fit is done between the small signal linear gain curve, and the output P1dB and saturation points to determine the actual gain curve of the amplifier. Using the input power and the non-linear polynomial gain curve, the actual gain of the amplifier can be determined.

4. Create Intermods and Harmonics - Using the non-linear parameters of output P1dB, Saturation Power, IP3, and IP2, intermods and harmonics will be created. See the Calculate Intermod and Harmonics section for additional information.

5. Frequency Rolloff - All signals, intermods, and harmonics will be attenuated as a function of frequency according to the attenuation slope that begins at the the corner frequency. NOTE: Noise will bypass this step and will not be rolled off with frequency.

6. Reverse Isolation for Internally Created Intermods and Harmonics - Once intermods and harmonics have been created and rolled off with frequency, these intermods and harmonics will appear at the amplifier input and continue to propagate backwards through the system.

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7. Reverse Isolation for Reverse Traveling Signals - Reverse isolation will be applied to all reverse traveling signals that encounter the amplifier output before its input.

Channel Definitions

Channelized Measurements and Measurement Bandwidth

Over 30 different types of measurements are available for SPECTRASYS. Many of these measurements integrate spectrum power. A frequency and bandwidth are required in order for SPECTRASYS to know where to integrate the spectrums. The Channel Frequency specifies the center integration frequency and the ‘Measurement Channel Bandwidth’ specifies the range of frequencies to integrate over.

For example, if a power amplifier was designed for a 5 MHz carrier operation in the 2 GHz band, then you must set the ‘Measurement Channel Bandwidth’ to 5 MHz. If a carrier is injected into the input of the amplifier at 1990 MHz, then all measurements along the path will integrate their spectrums from 1987.5 to 1992.5 MHz, i.e. 1990 ± 2.5 MHz.

See: System Simulation Dialog box, General Tab

Channel (Path) Frequency

Since each spectrum can contain a large number of spectral components and frequencies, SPECTRASYS must be able to determine the area of the spectrum over which to integrate to determine power levels. A ‘Channel Frequency’ and a ‘Measurement Bandwidth’ define this integration area. SPECTRASYS can automatically identify the desired ‘Channel Frequency’ in an unambiguous case where only one frequency is on the ‘from node’. An error will appear if more than one frequency is available. In this case the user must specify the intended frequency for the designated path.

A unique ‘Channel Frequency’ exists for each node along the specified path. Consequently, each node along the path will have the same ‘Channel Frequency’ until a frequency translation element such as a mixer is encountered. SPECTRASYS automatically deals with frequency translation through a mixer. The individual mixer parameters of ‘Desired Output (Sum or Difference)’ and ‘LO Injection (High of Low)’ are used to determine the desired frequency at the output of the mixer. A mixer is the only device that causes a frequency translation of the center frequency. For the following schematic, the channel frequency (CF) is shown in the table. Notice that CF is 100 MHz at all nodes before the mixer, and 10 MHz after the mixer (i.e. IF frequency).


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The ‘Channel Frequency’ is a critical parameter for SPECTRASYS since most of the measurements are based on this parameter. If this frequency is incorrectly specified then all measurements using this frequency will be incorrect. The easiest way to verify the ‘Channel Frequency’ that SPECTRASYS is using is to look at the ‘Channel Frequency’ measurement in a Table or a Rectangular Graph.

Offset Channel

The offset channel is a special measurement that allows specification of a user defined channel and bandwidth relative to the main channel. The user can specify the 'Freq Offset from Channel' and 'Measurement Bandwidth' parameters on the "Options" page of the 'System Simulation' dialog box.

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When these parameters are used in conjunction with the 'Offset Channel Frequency' and 'Offset Channel Power' measurements the user is able to determine the integrated channel power for an arbitrary channel relative to the main channel. Furthermore, both the 'Freq Offset from Channel' and the 'Measurement Bandwidth' parameters can be made tunable by placing a '?' in front the parameter to be tuned.

For example, perhaps you would like to determine the power of the phase noise at 100 kHz offset from the main channel. The 'Freq Offset from Channel' would be set to '0.1' MHz and the 'Measurement Bandwidth' could be set to the a user defined bandwidth; for example: 10 kHz or '0.01' MHz. The 'OCF' (Offset Channel Frequency) measurement could be added to a table to show the user the actual frequency being used for the 'OCP' (Offset Channel Power) measurement. It's always a good idea to add this frequency measurement to a table so the user knows that all parameters have been correctly specified. Furthermore, when a mixer is encountered, the user will know exactly which frequency is being used for the offset channel power measurement. The 'OCP' measurement can be added to a level diagram or a table to show the power of the phase noise as it travels along the specified path.

Coherency

Overview

Coherent signals have similar direction, amplitude, and phase and originate from a common source. If two coherent signals have the same amplitude and phase when


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added together will cause a power increase by 3 dB. Furthermore, if the same two signals had the same amplitude but where exactly 180 degrees out of phase they would cancel each other out. Whereas, two non-coherent signals of the same amplitude when added together will only produce a 1.5 dB increase in output power and two identical non-coherent signals will not cancel each other out.

SPECTRASYS deals with coherent and non-coherent signals and follows these rules:

1) Each source is non-coherent with any other source.

For example, the following two sources on input "Port 1" are considered non-coherent:

Source1: CW: 100 MHz, -50 dBm, 0 Deg

Source2: CW: 100 MHz, -50 dBm, 0 Deg

even though they both have the same frequency, amplitude, and phase.

2) Once a source divided (split, coupled, etc) it will be coherent with itself if the divided paths are added back together.

For example, assume a signal source drives a 2 way splitter before being amplified by two parallel amplifiers which are then combined back together, as shown below. Since the signal source appeared on the common node of the 2 way splitter each of the splitter output would contain part of the coherent signal.

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Use of a splitter is also a convenient way to create multiple coherent sources. The following 4-way splitter creates four coherent sources.

Composite Spectrum

Identifying Spectral Origin

Since each spectral component is tracked separately and SPECTRASYS knows the direction of travel of all signals, the user can find the origin and path of each spectral component by placing a marker on the graph or simply flying the mouse over the spectral component of interest. When a graph marker is added to a plot, the marker will attach itself to the closest data point. Also the mouse flyover text appears when the mouse is over the marker symbols (trace segment endpoints) or the marker text on the right side of the graph. These marker symbols can be enabled or disabled. The default marker symbols look like large round dots. If the user is having a difficult time trying to get the mouse flyover text to popup it is because the mouse cursor is not near a marker symbol. The best solution to this problem is to enable the marker symbols so the user can see the marker locations and place the mouse cursor accordingly.

There exists a long and short form of spectral identification. The short form appears when a marker is placed on a graph. The long form will appear on mouse flyover near the mouse cursor (if the text is not too long) and will also be displayed on the status bar of the GENESYS window.

The format of the spectral identification is as follows:

GENERAL FORMAT

Line 1 - Marker Frequency, Marker Power (Voltage) Level (the Frequency and Power appear on different lines for marker text on the right of the graph)

Line 2 - [Frequency Equation], Origin Node, Next Node, ..., Current Node

Frequency Equation

From the frequency equation the user can identify which source frequencies created the spectrum. This equation is written like a typical mathematical equation. The long form of


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the equation will contain the actual name of the source, whereas the short form uses a short hand notation to indicate the source. The short hand notation is "S" for source plus the index number of the source. For example, S1 would mean the first source listed in the Sources Table of the 'System Simulation' dialog box; S2 the second, and so on regardless of the actual name of the source.

Frequency Equation Examples

[S1+2xS2] - Source1 (first source in the source table) + 2nd Harmonic of Source2 (second source in the source table)

[S1-S2+S3] - Source1 (first source) - Source2 (second source) + Source3 (third source)

[S2+3x[2xS3]] - Source2 (second source) + 3rd Harmonic of a 2nd Harmonic of Source3 (third source)

Sometimes the frequency of the equation may be negative. In this case, the user should simply use the absolute value of this frequency equation.

Path

The path of the spectral component can be determined by examining the comma delimited sequence of node numbers (short form) or reference designators (long form) which identify the node or element where the spectrum was created and the node or element sequence that the signal took to arrive at the destination node. The first node number or reference designator after the closing frequency equation bracket shows the reference designator or node number where the spectrum first appeared or was created. The subsequent node numbers or reference designators indicate the path that the spectral component took to arrive at the node under investigation.

Path Examples

[S1-2xS2],6,7,8,12,5,2 Would indicated that a third order intermod (S1-2xS2) was created at node 6 then traveled through nodes 7, 8, 12, 5 and then arrived at node 2 (which is the current node under investigation).

NOTE: Currently, mixer sum and difference frequencies and the LO frequency used for the frequency translation are not supported in the spectral component identification. However, the input source to the mixer is identified and the user can figure out the actual output frequency of the mixer used for the creation of the spectral component.

Feature Activation

The spectral identification feature is activated from the "Composite Spectrum" page of the System Simulation dialog box. The check boxes involved are: Totals (i.e. the sum of all signals), Show Signals (i.e. sources), Show Intermods and Harmonics, and Show Individual Components. For the spectral origins to show on markers or flyover help, the "Show Individual Components" box must be checked.

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EXAMPLE: Consider the Getting Stated # 8 example. In the schematic, there are two amplifiers. Each can create second harmonics of the input signal. If the output power of the second amplifier is plotted, it is easy to identify source and amplitude of each of these harmonics. This is true even though they are of the same frequency. Consider the first source (S1) at 100 MHz at the input node # 1 in the schematic below.


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For the power from RFAMP_2 at node # 7, consider the second harmonic (i.e. [2xS1] ). One component is generated in the first amplifier and first appears at node # 4. The designator is [2xS1],4,6,8,7. The amplitude is about -95 dBm as shown either in the flyover box or in the marker text. Notice that the flyover text has the long form of the identifier, whereas the marker text is the short form. The component generated in the second amplifier (RFAMP_2) has the designator [2xS1],7 since it first appears at node # 7. The amplitude is -90 dBm.

TROUBLESHOOTING: If the identifiers do not appear on the graphs, check the "Composite Spectrum" page of the System Simulation dialog box. Make sure that the "Show Individual Components" box is checked. If intermods or harmonics are desired, put a check mark in the "Show Intermods and Harmonics" box.

Path Spectrum

Along every path there are 5 categories of spectrums that every signal will be part of. These spectrums are: desired, undesired, noise, intermod, and total.

Desired and Undesired Spectrum

The definition of ‘Desired Spectrum’ is spectrum that is traveling in the same direction as the desired path. All other spectrum originating from other sources will be present at the node of interest but will be specified as ‘Undesired Spectrum’ since it didn't originate along the desired path direction. Each and every node along the path contains both ‘Desired’ and ‘Undesired’ spectrums.

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As with a real circuit board, all signal sources propagate their signals to every node in the system since perfect isolation is unrealizable with real components. Consequently, real signals propagate in both directions at every node. SPECTRASYS follows this same model and signals travel in both directions at a every node. However, the user is typically only interested in the RF power traveling in a particular direction. For example, if the user created a schematic of a single conversion super heterodyne receiver the cascaded gain for the primary receive path would only make sense looking in the direction from the receiver front end to the IF output. The direction of the LO radiation along the path from the LO to the receive antenna port would be in a direction opposite that of the received signal. As a result, the ‘Desired Spectrum’ for the received signal would be in the forward direction (from the receiver front end to the IF output) and the ‘Undesired Spectrum’ would be any other signal that didn’t originate from the receiver front end that is traveling in the reverse direction. However, looking at the signals along the LO radiation path, the LO signals would be the ‘Desired Spectrum’ and the received signals would be the ‘Undesired Spectrum’. All signals that are members of the ‘Desired Spectrum’ and ‘Undesired Spectrum’ are also members of the ‘Total Spectrum’.

See the example “Getting Started #5.wsp” for a good illustration of 'Desired' and 'Undesired' spectrum.

Noise Spectrum

All spectrums created from noise sources in the schematic are placed in the ‘Noise Spectrum’ and also in the ‘Total Spectrum’.

Intermod Spectrum

All spectrums created from intermods between two or more signals are placed in the ‘Intermod Spectrum’ and also in the ‘Total Spectrum’.

Total Spectrum

Every spectrum passing through a node will appear in this spectrum category.


Calculate Intermods and Harmonics

This example will help the user understand how SPECTRASYS deals with intermods and how the nonlinear devices handle these intermods. The user will also understand the difference between generated, conducted, and total third order intermod power.

Calculated Products

The following nonlinear second and third order products will be created for each pair of input signals F1 and F2 (listed in increasing frequency assuming F2 is greater than F1):

F2 - F1 2F1 3F1


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2F1 - F2 F1 + F2 2F1 + F2

F1 2F2 2F2 + F1

F2 3F2

2F2 - F1

Fig. 1 The relative levels of spectral components for the small signal regime and equal amplitudes of the signal's tones

Definitions of symbols:

P - Fundamental Tone Power

IPn - Nth Order Intercept Point

H1 - Fundamental Tone

H2 - 2nd Harmonic

H3 - 3rd Harmonic

IMn - Nth Order Intermods

IMn,m - Nth Order Intermods due to M tones

SPECTRASYS uses the formulas for calculation of the nonlinear products which correspond to the small signal model (Taylor expansion of the nonlinear characteristics).


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2nd Order Intermod Products

The amplitude of the second order intermod products (F2 - F1 and F1 + F2) are equal to the tone power level minus IP2 or in other words IM2 = Ptone - IP2.

2nd Harmonics

The amplitude of the second harmonics are calculated as follows . The amplitude of the second harmonic is equal to the tone power level minus the difference between IP2 (second order intercept) and the tone power level of the device.

3rd Order 2 Tone Products

The amplitude of the third order products (2F1 - F2, 2F2 - F1, 2F1 + F2, and 2F2 + F1) are equal to 2 times the quantity of the tone power level minus IP3 or in other words IM3 = 2 (Ptone - IP3).

Carrier Triple Beats (3rd Order 3 Tone Products)

When more that two carriers are present in a channel, 3rd order intermod products can be created by the multiplication of three carriers. These intermods are called carrier triple beats. SPECTRASYS will create triple beats for all combinations of 3 or more carriers. Working out the math, carrier triple beats will be 6 dB higher that the 3rd order 2 tone products. This calculation of the triple beat level assumes that the amplitude of all input signals is the same. The frequency combinations of the carrier triple beats are as follows:

F1 - F2 + F3 F1 - F2 - F3 F1 + F2 + F3 F1 + F2 - F3

3rd Harmonics

The amplitude of the third harmonics are 9.542 dB below the 3rd order 2 tone products.

Measurements

SPECTRASYS creates intermods for all input sources driving nonlinear elements such as amplifiers and mixers. Cascaded intermod equations are NOT used by SPECTRASYS. There are two serious drawbacks using the cascaded equations. See the section 'Cascaded Intermod Equations' for additional information. Also see the 'Calculate IIP3 (TOI)' section.

Linear elements will not create intermods. However, these elements will conduct them from prior stages where they were created. The 'Total Third Order Intermod Power' (TIM3P) can be separated into two distinct groups of intermods. The first group is 'Generated' intermods and the second is 'Conducted' intermods from a prior stage. SPECTRASYS is able to separate intermods into these two groups. This allows the user to quickly determine the weak intermod link in


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a cascade of stages. This total is the non-coherent sum of the generated and conducted third order intermod power. 'Generated Third Order Intermod Power' (GIM3P) is the total third order intermod power that is created in a particular stage. This measurement will only show the intermod levels for the stages that created them. 'Conducted Third Order Intermod Power' (CIM3P) is the total third order intermod power conducted from the prior stage. This measurement, when used in conjunction with the 'Generated Third Order Intermod Power (GIM3P)', will identify the stages in the chain that are the weakest link and are the highest contributor to the total intermod power. The stage prior to the stage where the conducted intermods are dominant through the rest of the chain, is the weak link in the chain.

See the 'Getting Started #8.wsp' for an illustration of these measurements.

Tone Dissimilar Amplitude

In most cases, it is assumed the two tone inputs have equal amplitude. Mathematically, this is the most convenient or easiest way to analyze intermod distortion. However, this method is not always an accurate model of the real problem (like after the IF filter). When both input amplitudes are equal, the third order IM product level changes 3 dB for every 1 dB change in amplitude. However, when you have dissimilar interfering tone amplitudes the adjacent tone will change by 2 dB for every 1 dB. The alternate tone will change 1 dB for every 1 dB of change. Channel Bandwidth and Intermods

The bandwidth of third order products is greater than the individual bandwidth of the sources that created them. For example, if two 1 Hz tones were used to create intermods, the resulting bandwidth would be 3 Hz. The bandwidth follows the intermod equation that determines the frequency except for the fact that bandwidth cannot be subtracted. For example, if the third order intermod equation is: Fim3 = F1 - 2*F2 then the equation for the resulting bandwidth would be: BWim3 = BW1 + 2*BW2. If BW1 = 30 kHz and BW = 1 MHz, then the resulting bandwidth would be 2.03 MHz. The user needs to make sure that the 'Channel Measurement Bandwidth' is set wide enough to integrate all of this energy.

Calculate Intermods and Harmonics

A checkbox named 'Calculate Intermods and Harmonics' located on the "Calculate" page of the 'System Simulation' dialog box can be used to disable/enable all calculation of all intermods and harmonics. Simulation speed will be increased for large number of carriers and nonlinear stages if intermods and harmonics are being calculated. The user can disable this option to increase the simulation speed if intermod and harmonic calculations are unimportant.

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Cascaded Intermod Equations

Cascaded intermod equations are NOT used by SPECTRASYS. There are two serious drawbacks using the cascaded equations. First, the equations assume that the interfering input signals are never attenuated through the cascade of stages. This may be fine for simple line-up of elements. However, in the case of a super heterodyne receiver, the interfering signals should be attenuated after passing through the first mixer. Continuing the cascaded intermod analysis past the point where the interfering signals are attenuated will result in erroneous results. Secondly, with cascaded intermod equations it is very difficult to know which stages are the weak links in a chain. In order to solve these two problems, all intermod measurements require that two or more interfering signals be applied to the cascaded input. For IIP3 measurements a third source is also needed.

Intermod Tests

Calculate IIP3 (TOI)

This function needs to be enabled in order for the Input Third Order Intercept (IIP3 or TOI) point or Output Third Order Intercept (OIP3 or TOI) point can be calculated correctly. Cascaded intermod equations are NOT used by SPECTRASYS. There are two serious drawbacks using the cascaded equations. See the section 'Cascaded Intermod Equations' for additional information. Also see the 'Calculate Intermods and Harmonics' section for additional information.

This function can be enabled by checking the 'Calculate IIP3 (TOI)' checkbox located on the "Calculate" page of the 'System Simulation' dialog box.

Manual (Advanced) Mode For this particular mode the user must create a minimum of 3 sources. The first source represents the desired signal and SPECTRASYS will use this information to determine the in channel gain and the channel frequency. The two (or more) other sources are the actual signals that are used to create intermods in the channel. The user must make sure that the desired signal and the interfering tones are spaced properly such that intermods will fall within the bandwidth of the desired channel. Furthermore, for this particular technique there is no restriction on the number of interfering signals used to create the intermods. The total intermod power found within the channel will be used to determine the actual output and input intercept points. For this mode of operation the user needs to only specify the frequency offset from the desired channel to the first interfering tone. If at least 3 sources are not created at the correct frequencies and the tone offset is not set correctly intermods will not appear within the channel and it will appear that intermods are not working. This mode is enabled when the 'Manual (Advanced)' checkbox has been checked. Automatic 2 Tone


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In this particular mode SPECTRASYS will create the needed 3 sources to calculate intermods and intercept points. However, in this case the user needs to specify some additional information such as the 'Input Port', 'Tone Spacing', 'Gain Test Power Level', and the '2 Tone Power Level' parameters. Three sources are needed to make intermod measurements. The first source is created at the channel frequency and is used to determine the 'in channel' gain of the chain. The user must specify the level of this source through the 'Gain Test Power Level' parameter. This level should be above the noise floor and be well below the level that would cause non-linear behavior. The 'Input Port' specifies the port where the 3 signal sources are created. The 'Tone Spacing' determines the spacing between the desired channel and the first interfering tone. This same spacing is also used between the two interfering tones. Because of this spacing we are guaranteed that intermods will be created in the channel. The '2 Tone Power Level' is used to specify the actual level of both interfering tones. These parameters are shown graphically in the plot below.

For the 'Input Third Order Intercept (IIP3)' and 'Output Third Order Intercept (OIP3)' measurements the '2 Tone Power Level' doesn't really matter since these parameters are based on relative measurements. However, this '2 Tone Power Level' is very important when determining the absolute intermod power level and should be set according to the maximum interference levels seen by the circuit.

This mode is enabled as long the 'Manual (Advanced)' checkbox is unchecked.

Mixers

Mixers are key elements in any RF system that translates frequencies like super heterodyne receivers and transmitters. Many times their performance is critical to the

Mixers

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proper operation of the system and can be one of the most challenging components to characterize and make behave properly under all system conditions.

SPECTRASYS will aid the user in understanding the output spectrum of the mixer and all of its non-ideal characteristics such as isolation.

Two types of mixers are available in SPECTRASYS, they are: Passive and Active. The only difference between the Passive and Active mixer is respectively the "Conversion Loss" and "Conversion Gain".

The following dialog box shows the properties for a passive mixer. (See "RF Mixer" in the Element Manual for more information)

The 'Desired Output' parameters is only used by SPECTRASYS to determine the desired channel frequency along a path defined through the mixer. This parameter does not affect the operation of the mixer in any way.

The 'LO Drive Level' parameter is currently only used by the mixer to determine if the actual simulated LO power level is within the targeted LO range.

When a signal spectrum arrives at a mixer port the following actions occur:


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Signal Spectrum Arriving at the LO Port - The LO spectrum will be propagated (without a frequency translation) to the RF and IF ports with their respective isolation and the final LO power level at these ports will also take into account the impedance for that particular node. The LO signal will be convolved with the RF/IF signals and harmonics/intermods, allowing the effect of phase noise to be sen.

Signal Spectrum Arriving at the RF Port - The following spectrums will be created at the other mixer ports:

a. LO Port - All RF port spectrums will be propagated to the LO port through the 'LO to RF Isolation'

b. IF Port - Several spectral components will created at this port.

1) All RF port spectrums will be propagated to the IF port through the 'RF to IF Isolation'

2) Both the Sum and Difference spectrums between the LO spectrum and the RF spectrum will be created. The undesired outputs (sum or difference) will be attenuated by the image rejection.

3) All second and third order products will be created at the IF port for all second and third order combinations of the RF input spectrums.

4) Compression will be calculated in the same way as for amplifiers.

Signal Spectrum Arriving at the IF Port - Spectrums will be treated identically to the RF port, being propagated from IF to RF.

Mixer LO Level Warning - Maintaining proper mixer LO level is important to guarantee the performance of any mixer. Typically, this is a level that can easily be overlooked from one design turn to another. The user must specifically check the LO power level to ensure that the mixer is operating in the expected range. With SPECTRASYS this process is much easier and the user will automatically be notified if the mixer is being over or under driven. The user has control of the LO drive level of each mixer and a global system simulation parameter that will check that the LO power is within a user specified widow of the LO drive level. The user specified mixer LO parameter is the 'Mixer LO Range' specified on the 'Options' tab of the 'System Simulation' dialog box. During system calculations, SPECTRASYS will integrate the entire LO spectrum power and this power will be compared to the mixer LO drive level. If this LO power is outside the specified LO range a local error will be created and the mixer will change color indicating to the user that a potential error has occurred in the mixer.

Noise

Broadband Noise

SPECTRASYS can process large blocks of spectrum very quickly and broadband noise

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is no exception. Noise can come from any of three different sources. These are:

1. Thermal noise of passive components

2. Added noise of active components

3. Noise source applied to a port

SPECTRASYS uses the following four parameters found on the 'Options' page and 'Calculate' page of the 'System Simulation' dialog box to determine the frequency range, power level, and number of points needed to represent the broadband noise:

1. Ignore Frequency Below

2. Ignore Frequency Above

3. System Temperature

4. Number of Noise Points

Ignore Frequency Below - Lower noise frequency limit.

Ignore Frequency Above - Upper noise frequency limit.

System Temperature - This is the global ambient temperature of the system and determines the absolute power level of the thermal noise. For convenience SPECTRASYS will automatically calculate the resulting thermal noise power and display it just below the edit field.

Number of Noise Points - This is the initial number of noise points that will be used by SPECTRASYS to generate noise. Setting the correct number of noise points can be very unwieldy for a high frequency system that may contain narrow band filters (IF for example). Not selecting enough noise points to correctly represent the noise in a narrowband filter could result in completely ignoring the narrow band filter which would give erroneous results. However, on the other extreme adding too many noise points will slow down the simulation. SPECTRASYS automatically knows which frequencies in the noise spectrum need more points. It will automatically insert them into the noise spectrum so that the entire noise spectrum will be accurately represented even through narrow band filters. It will do this based on the frequencies of all the known sources in the simulation. Since SPECTRASYS uses smart noise point insertion, the 'Number of Noise Points' parameter is not important unless the user wants to add additional noise points.

Noise sources are not discussed in this section. Please refer to the 'Sources Section' for more information about noise sources.

NOTE: Noise will not be calculated unless the ‘Calculate Noise’ checkbox in the 'System Simulation' dialog box has been checked.


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Paths

Measurements are Defined by Paths

Since spectrums are propagated to every node in the schematic the user must have some way of indicating signal direction in order to make useful measurements. A path is used for just such purpose. Basically, a path is a node number sequence and is defined by specifying:

1. Name (or use the default i.e. Path1)

2. ‘from node’

3. ‘thru nodes’ (optional)

4. and ‘to node’

Given the ‘from node’ and the ‘to node’ SPECTRASYS will pick the shortest path between the two node even though several paths may exist. If the user would like to look an alternate path then ‘thru nodes’ can be specified.

In the example below, if the following two paths existed: a) 1,3,9,6,8,2 and b) 1,5,10,4,7,2 then specifying the path as: “1,2” SPECTRASYS would select path (a). However, if the user wanted to specify path (b) then by simply finding a unique node(s) then this can could be specified i.e. “1,10,2”. There is no restriction on the number of nodes used to specify a path. In some cases several ‘thru’ nodes may need to be specified to uniquely identify a path.

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In order for SPECTRASYS to be able to locate the path a signal source must be present on the ‘from node’. If a source has not been created or has been disabled then SPECTRASYS will not be able to locate the path.

The ‘from node’ and the ‘to node’ can be any node in the schematic and is not restricted to an input or an output port. However, the first node in the path (node sequence) must be the ‘from node’ and the last node must be the ‘to node’. All nodes in the path must be separated by commas and the ‘thru nodes’ can be in any order.

Two functions exist on the "Paths" page of the System Simulation dialog box (shown below) to aid the user in specifying the path. The first is an “Add All Paths From All Sources” button. All possible port-to-port paths will be added to the “System Simulation” for all ports that have a source defined. If no sources have been defined then no paths will be added. If the number of paths becomes very large then the user will be prompted before adding the paths. The second is an “Add Path” button which will prompt the user for the 1) Path Name, 2) From Node, and 3) To Node.

See the 'System Simulation Parameters - Paths' section for additional information.

Path Frequency

This is the same as the 'Channel Frequency'. See Channel Frequency for more information.

Directional Energy (Node Voltage and Power)

When more than two connections occur at a node a convention must be established in order to make sense of the information contained at the node for viewing a table or a level diagram. The value that is reported for a node along a path that has more than two elements is the value seen by the series element in the path entering the node.

For example, in the following example we have defined two paths 'Path1_2' which is the path from node 1 to node 2 and 'Path3_2' which is the path from node 3 to node 2. On a level diagram or in a table the value reported at node 5 for 'Path1_2' would be the value of the measurement leaving terminal 2 of the resistor R1 entering node 5. Likewise, the impedance seen along this path is that seen looking from terminal 2 of the resistor R1 into node 5. Consequently, the impedance seen by R1 is the L1 to port 3 network in parallel with the C1 to port 2 network. In a similar manner the value reported at node 5 for the 'Path3_2' would be the value of the measurement leaving terminal 2 of inductor L1 entering node 5. The impedance for the node looking from terminal 2 of inductor L1 is most likely to be completely different from the impedance seen by R1 or even C1 because from the inductors perspective, the R1 to port 1 network is in parallel with the C1 to port 2 network.

SPECTRASYS knows about the direction of all of the paths and will determine the correct impedance looking along that path. As a result all measurements contain the correct values as seen looking along the path of interest. Remember, absolute node impedance and resulting measurements based on that impedance don't make any sense since they are totally dependent on the which direction from which we look into the node.


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Transmitted Energy

Transmitted energy is only the energy flowing in the forward direction.

For example, lets suppose that we have a fixed attenuator of 3 dB in series with a bandpass filter that has 50 dB of rejection at 1 GHz which is outside the passband of the filter. Now lets suppose that we are going to look at the power level of this "out-of-band 1 GHz signal" along the path from the attenuator input to the output of the bandpass filter. Intuitively, we would expect to see 3 dB of attenuation of the 1 GHz signal across the 3 dB pad and then and additional 50 dB of rejection across the filter. However, when we closely examine the impedances and power levels at each node we see things in a slightly different light.

1) The input impedance of the 3 dB pad will not be exactly 50 ohms since its load impedance is the input impedance of the bandpass filter at the input frequency of 1 GHz which can be very low or very high. Consequently, if the applied power level is 0 dBm then the actual power level that will be transmitted through the attenuator (node 1 power) will be lower than the applied power.

2) Since the input impedance of the bandpass filter at the out-of-band frequency of 1 GHz can be very high or low there will be very little power at the input of this filter for this particular frequency that will actually be transmitted through the filter. Most of the energy will be reflected by the filter. Since the input power to the attenuator is very high and the input power to the bandpass filter is very low then it appears that the entire attenuation of the filter appears across the 3 dB pad.

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In other words the transmitted energy through any filter will be equal to the insertion loss.

When we realize that the power at each node is the actual power that is transmitted through the element to the next node in the path then the level diagrams make more sense. Another way that we can think of this node power is that this would be the actual power measured at that node with a power meter at that given frequency if the power meter was matched to the same impedance as seen by that load circuit.

Outputs

Analyzer Mode

The 'Analyzer Mode' is a unique tool to help the engineer visualize what the simulated spectrum would look like on a common spectrum analyzer. Since many time requirements standards specify how conducted emissions measurements are made with a spectrum analyzer, the analyzer mode has been added to allow the user to correlate the simulation data with data measured in the lab.

During the system simulation the analyzer will create an analyzer trace for every node in the system. Consequently, for systems with large number of nodes, the integrated analyzer traces alone can be time consuming if the analyzer properties are not optimized.

The analyzer mode can be enabled by checking the 'Enable Analyzer Mode' checkbox on the 'Composite Spectrum' tab of the 'System Simulation' dialog box.


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The analyzer has the following basic properties:

a. Resolution Bandwidth

b. Filter Shape

c. Randomize Noise

d. Analyzer Noise

e. Frequency Limits

Resolution Bandwidth

The analyzer can be thought of just like a spectrum analyzer that has a sweeping receiver that peak detects the total power within the resolution bandwidth. For the analyzer mode the user can specify the resolution bandwidth of this sweeping filter. The resolution bandwidth will default to the 'Measurement Channel Bandwidth' if no value has been specified.

Filter Shape

The filter shape when the analyzer integrates the spectrum to determine the actual power of the analyzer. This filter shape is analogous to the resolution bandwidth filter shape in a spectrum analyzer. However, a brickwall filter can be created theoretically and is implemented in the software as a user selection. Furthermore, a more realistic filter can also be selected which is created from a gaussian 3 element lowpass prototype. The user is able to select three widths for this particular filter which are 30, 60, or 200 channel bandwidths wide. No spectrum integration will occur outside the width of this filter. The reason there is a limit to this width is to reduce the amount of data collected, saved, and processed by SPECTRASYS. If simulation speed is important then using the narrowest filter shape will have the best simulation speed.

Randomize Noise

When this feature is enabled, random noise will be added around the resulting analyzer sweep. In this way the output will be more representative of a typical spectrum analyzer, at the expense of additional computation time.

Analyzer Noise

All spectrum analyzers have a limited dynamic range. They are typically limited on the upper end by intermods and spurious performance at the internal mixer output. On the lower end they are limited by the noise of the analyzer. This noise is a function of the internal architecture of the specific spectrum analyzer and the internal RF attenuator. The user has the ability to enter a noise floor for the analyzer to more accurately represent the data that will be measured in the lab.

Limit Frequencies

By default the entire spectrum from the lowest frequency to the highest frequency will be processed by the analyzer for every node in the system. In some cases this may be very

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time consuming. In order to improve the simulation speed and just show the area of interest, frequency limits can be enabled to restrict the computation range of the analyzer. The 'Start' and 'Stop' frequencies will determine the frequencies that the analyzer will process. The 'Step' is used to specify the number of simulation points. A new simulation point will be added for each 'Step'. The step size can be decreased until the maximum number of simulation points is greater than 20,000.

Number of Simulation Points

The number of simulation points for the graph is determined internally in SPECTRASYS. This parameter cannot be changed by the user. Since SPECTRASYS can deal with large frequencies ranges, the amounts of data collected for a single spectrum analyzer trace could be enormous. Furthermore, the analyzer function is not a post processing function. The number of simulation points cannot be changed without rerunning the simulation. In order to better control the amount of data collected, which is proportional to the simulation time, SPECTRASYS internally determines the number of simulation points to use.

Troubleshooting

1. What does it mean when the signal doesn't seem to be lined up with the integrated spectrum? All this means is the frequency resolution isn't small enough to accurately represent the signal of interest. If this is the case, there are a few things that can be done to increase this resolution. First, the resolution bandwidth can be reduced. If this is inadequate, the 'Limit Frequencies' feature should be enabled and the user can specify the 'Start', 'Stop', and 'Step' frequencies used for the analyzer.

Tunable Parameters

Any of the parameters in the 'Analyzer Mode' can be made tunable by placing a '?' in front of the parameter.

Level Diagrams

A level diagram is a diagram that can display measurements of cascaded stages along a user defined path. Each horizontal division of the x axis of the graph represents a stage along the path. The first division represents the input to the cascade and the last division represents the output of the cascade. The value of the measurements are displayed on the vertical axis.

The concept of level diagrams has been around for several years. RF designers have used level diagrams for decades to architect and design RF systems. These diagrams have not appeared in commercial RF simulation software until SPECTRASYS. Eagleware's implementation of a level diagram is unique and will help the RF engineer to optimize the RF system performance right from the diagram.

Level diagrams give the user a quick visual indication of the performance of the entire cascade. Node numbers are placed on the horizontal axis to show the node sequence of the path. Furthermore, schematic symbols are extracted from the schematic and placed at the bottom of the level diagram. These are the schematic symbols of the path of the


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level diagram. The user can change any of the schematic element parameters by double clicking on the desired symbol directly on the level diagram. The element parameters for that device will appear and the user can edit those parameters directly. The effects of these changes are shown immediately on the graph.

For the simple schematic below, the noise power along the main path was of interest. The nodes along the path are 1,5,4 and 2. The level diagram shows the noise power at each node and the schematic element between each node. This schematic symbol alleviates the need to refer back to the main schematic and allows changes to element parameters.

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For multiple connections at a node, energy can be traveling in multiple directions. For details on understanding the meaning of the node measurements in this case please refer to the section on Directional Energy.

Level diagrams and tables contain only transmitted energy information. In other words, this is the transmitted energy traveling from node to node along the specified path. See the Transmitted Energy section for additional information.

Composite Spectrum

Composite spectrum is unique feature in SPECTRASYS. A composite spectrum allows the user the ability to view full node spectrums and identify the spectral component origins and their path of travel to the designated node. There are three general spectral categories in SPECTRASYS. They are: 1) Signal, 2) Intermods and Harmonics, and 3) Noise. Furthermore, each source and their derived components (harmonics, intermods, spurs, etc.) will be propagating in all directions when then arrive at a node.

The makeup of composite spectrum consists of a trace for each:

1. Element representing the total power traveling from that element into the node 2. Signal component

3. Intermod and harmonic component 4. Noise component

Because of the way that SPECTRASYS keeps track of these spectral components independently and each component is represented by a trace on the graph, it is not uncommon to have hundreds and even thousands of spectral components (traces) at a


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single node. The user can determine which of the spectral pieces they would like to see. On the 'Composite Spectrum' tab of the System Simulation dialog box the user can check or uncheck which pieces of the spectrum they would like to see. The total from each element will always be shown and cannot be disabled. Furthermore, all spectral components can be ignored below a user specified level.

In order to view a composite spectrum plot, the user must select the 'System Simulation' and 'Composite' in the 'Default Simulation/Data or Equations' combo box of the rectangular graph properties (i.e. 'System1.Composite'). The user must then specify whether they want to display a voltage or a power measurement and the node number (i.e. P2 - power at node 2).

For example, a simple receiver (shown below) will have the antenna signal propagate forward through the receiver front end then through the mixer and the IF chain. However, after the LO arrives at the mixer it will propagate backwards through the receiver front end to arrive at the antenna input. In addition, this LO signal will also propagate forward through the IF chain. If we were to examine the receiver input on a spectrum analyzer we would see both the input signal from the antenna as well as the LO leakage. On the spectrum analyzer we would see both of these signals. However, we know that they are traveling in different directions. At the antenna input node we know that the received signal is traveling toward the IF chain and the LO leakage is traveling away from the IF chain.

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Unlike a spectrum analyzer, on the SPECTRASYS composite plot we can actually distinguish the direction of travel of all spectral components. Furthermore, a trace that represents the total from all directions in a node is represented. By simply placing the mouse over the trace the user is able to identify which direction the signals are traveling by seeing which element they are coming from. Think of this is as an N-way directional coupler with infinite directivity, so that we only see the signals traveling in the direction of interest. All of these signals from each direction of travel is an independent trace on the composite spectrum plot. For example, if we had three elements connected to a node we would see signals traveling from each of these elements.

For the example shown, the components in the RF input are at 90 and 100 MHz. Notice that the 90 MHz component is identified as from source S2 (i.e. the LO drive). The leakage path is from the LO input port [S2] or node 3, through nodes 7 and 4 (i.e. the mixer LO to RF isolation), and then through attenuator (ATTN_1). The power of -25 dBm is the result of the LO power of 10 dBm attenuated by 5 db and passing through the mixer isolation path with -30 db.

One of the most useful features of composite spectrum is is the ability to identify the origin and path of each spectral component. See 'Identifying Spectral Origin' and 'System Simulation Parameters - Composite Spectrum' for more information.

Controlling Spectrum Limits

There are several ways in SPECTRASYS to the control the output spectrum. The user


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can control many pieces of the spectrum. Calculation of intermods, harmonics, and noise can all be enabled or disabled. When disabled all elements in the schematic will not calculate their respective pieces of the spectrum.

There are four parameters used by SPECTRASYS to limit the amplitude range and frequency limits of the spectrums. These parameters are:

1. Ignore Level Below

2. Ignore Frequency Below

3. Ignore Frequency Above

4. Max Spectrums

These parameters can be changed on the 'System Simulation Dialog Box'.

These parameters are used by SPECTRASYS to determine whether a spectral component should be kept or ignored. Any of these parameters are tunable and can be tuned by placing a '?' at the beginning of the entered value.

Ignore Level Below (default = -200 dBm) - Any calculated spectral component below this amplitude threshold will be ignored whereas any spectral component above this threshold will be kept.

Sources

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Ignore Frequency Below (default = 0 Hz) - Any spectral component whose frequency is below this frequency limit will be ignored. However, there are several cases where negative frequencies may be calculated at interim steps which will be folded back onto the positive frequency axis. This parameter will only affect the final folded frequencies and not the interim frequency steps.

Ignore Frequency Above (default = 5 times the highest source frequency) - Any spectral component whose frequency is above this frequency limit will be ignored.

All of these limits will apply to every node in the system. Consequently, if a source was created at 100 MHz and the 'Ignore Frequency Below' limit was set to 200 MHz then the 100 MHz source would be ignored and would not be processed by SPECTRASYS.

Simulation Speed-Ups

As with any other type of simulation the larger the number of spectral components that need to be processed the more time the simulator will take. Setting these limits to only calculate the frequencies and amplitude ranges of interest can speed up the calculation process. However, take caution when setting these limits so that intentional spectrums are not ignored. For example, If we had a 2 GHz transmitter that had an IF frequency of 150 MHz and we set the 'Ignore Frequency Below' limit to 200 MHz then the entire IF signal would not be present and consequently neither would the 2 GHz RF signal.

Sources

Sources are a very powerful feature of the SPECTRASYS. There are 4 basic types of sources. They are:

!" Continuous Wave (CW)

!" Modulated

!" Noise

!" User Defined

Signal sources (CW, Modulated, and User Defined) are defined by a center frequency, bandwidth, power level, phase shift, and number of points. Every one of these parameters can be tuned by placing a question mark in front of the parameter. All sources are assumed to have a uniform spectral density. Every source can be easily enabled or disabled by checking or unchecking the “Enable” checkbox in the source table on the “General” page of the System Simulation dialog box.


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By clicking on the "Edit" button of any source, the following "System Source Parameters" dialog box comes up. This page is used to enter parameters for each source, as described below.

Sources

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Center Frequency – This is the center frequency of the source in MHz.

Bandwidth – This parameter is the bandwidth of the source in MHz. The lower frequency of the source is the center frequency minus ½ the bandwidth and the upper frequency of the source is the center frequency plus ½ the bandwidth .

Power Level – This is the average power level of the source in dBm.

Phase Shift – This is the phase shift of the source in degrees.

Number of Points – This is the number of points that represent the source. Most of the time 2 points is adequate to represent the source. However, in cases where the source bandwidth is large and the frequency response of the circuit may affect the bandwidth of the source, the user may want to increase the number of the points.

CW - All CW sources have their bandwidth defined to be 1 Hz. Furthermore, the number of points has been set to 2 points and can not be changed by the user.

MODULATED - A modulated source is currently represented by a uniformly distributed spectrum of constant amplitude. This type of spectrum is currently time-invariant. The user can set the following parameters: center frequency, bandwidth, power level, phase shift, and number of points.

USER DEFINED - The user defined source is a very powerful feature of SPECTRASYS. The user can specify the frequency, amplitude, and phase in both relative and absolute values. Relative parameters are entered into a text file (*.src) to specify the desired source in the frequency domain. Having relative values specified in a source file is a great advantage because the absolute center frequency, power level, and phase shift can be tuned in the System Simulation dialog box. Absolute values would not allow the user the ability to tune these parameters. Furthermore, the “Step and Repeat” function can also be used with source files that contain relative values. The number of points parameter is not needed for this particular type of source since each frequency point is specified in the data file.

The following data is a source file example:

UNITS HZ DBC 'Nominal frequency FREQ 0 'If freq is zero, data is SSB offset. DATA 1 -30 10 -50 100 -70 1000 -80 10000 -90


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100000 -95 1e6 -100 ENDDATA

The source file consists of keywords, comments, and the actual frequency, amplitude, and optional phase data.

NOISE

Broadband noise can be added to any CW, Modulated, or User Defined source. Noise is added to these sources by checking the “Broadband Noise” checkbox. Noise is specified by upper and lower frequency limits and spectral density. The noise spectral density is the power in dBm in a 1 Hz bandwidth. For a noise-only source, the user can uncheck the “Include Signal” checkbox.

Source Parameter Tuning

Every source parameter can be tuned by placing a question mark in front of the parameter.

Summary

All sources in SPECTRASYS have bandwidth and spectral density. Sources have a center frequency, bandwidth, power level, phase shift, and number of points.

All sources are defined in the frequency domain.

!" Sources are Modeled in the Frequency Domain

!" Currently, Time Varying Sources are not Supported

!" CW Sources are Defined to have 1 Hz Bandwidth

!" Modulated Sources can have any Bandwidth

!" A Modulated Source is Represented by a Uniform Spectral Density

Synthesis

Circuits can directly synthesized from SPECTRASYS. Right clicking on the behavioral model will bring a context sensitive menu. This menu will list the synthesis modules available for the given element. The selected synthesis module will be invoked and the parameters of the behavioral model will be passed to this synthesis module. See the specific synthesis section for more information about each synthesis tool.

Synthesis

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Once the user is satisfied with the synthesis results, these results can be substituted back into the behavioral model. If a behavioral model have been directly synthesized the subnetwork substitution will be automatic as show below.


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At this point the parameters for the behavioral model will be disabled. For additional information on model substitution see the 'Simulation Tab' section of the Schematic Element Properties page in the User's Guide.

Chapter 15: SPECTRASYS Tips

The basic operation of SPECTRASYS involves the propagation of individual source spectra and all of their derived products (intermods, harmonics, etc.) to every node in the system. These spectrums will keep propagating until no additional spectrums are created. For instance, any new inputs arriving at the input of an amplifier will cause intermods and harmonics to be created at the amplifier output at that particular time. If additional signals arrive at the amplifier input at a future time then new intermods, harmonics, and other spurious products will be created at the amplifier output. This process continues until no additional spectrums are created. If loops exist in the system schematic, then the output from one element will feed the input of the next element and spectrum propagation could continue forever unless special features are placed within the software to limit spectral creation in this infinite loop. SPECTRASYS has special features to control loops and limit the total number of created spectrums.

Loops

Elements in parallel (parallel amplifiers connected via a 2 way splitter at the input and combined back together with a 2 way combiner at the output) can cause spectrums to be created that will propagate around this parallel path (or loop). If the gain of the amplifier is greater than its reverse isolation the spectrums will keep on growing as they travel around the path and will never die out (we would have an oscillator). The key point here is that if there are loops in the system schematic then it is very important to make sure that the element parameters are entered correctly so that signals don't grow in amplitude as they traverse around a loop. The simulation will only be as good as those parameters in the model. If the user is suspicious that the simulation is taking extra time then isolation parameters of the components that make up that loop can be increased to large values to see if that is the cause. The user can then start decreasing the isolation of the interested components until the desired response is achieved.

Maximum Number of Spectrums to Generate

As a last resort, you can limit the number of spectrums that will be generated. The number of spectrums generated at any time is shown in the simulation status window while SPECTRASYS is running. A typical number to force a limit to is 100000. See the Options Tab for more information.

Ignore Spectrum

As mentioned previously, SPECTRASYS will continue to process new spectrums until no additional spectrums have been calculated. However, in the case where a loop exists, spectrums will continue to be created around the loop until the 'Ignore Spectrum Below' threshold is reached at which time spectrums are not calculated below this threshold. The higher this threshold the fewer the number of calculated spectrums. In order to minimize the simulation time the user should set this threshold to calculate the least number of spectrums which will accurately represent the output. For example, if the user

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is not interested in seeing anything below -100 dBm and simulation speed is an issue, then setting the threshold to -100 dBm will improve the simulation speed.

Linear Elements

The more nodes in the system schematic, the more spectrums that will be created and propagated. This spectrum creation and propagation takes time. If several linear elements are used in the system schematic and simulation speed is an issue, then linear element circuits can be moved to new schematics and then linked into the system schematic using a 'Network' block. This 'Network' block will then point to this newly created schematics.

Intermods

One of the largest time consuming operations in SPECTRASYS is the calculation of a large number of intermods due to a large number of input signals into a non-linear device such as a mixer or amplifier. You can disable the calculation of intermods and harmonics until the initial architecture and basic budget parameters are set. This can be done by unchecking the 'Calculate Intermods and Harmonics' checkbox on the 'Calculate' tab of the 'System Simulation' dialog box.

If a large number of intermods are to be calculated (due to a large number of input signals) the best thing to do is to first establish the architecture and make sure that system is performing as expected for a small number of input signals. It is much faster to optimize the architecture with a small number of input signals, rather than wasting time waiting for complete system analysis for issues that can be resolved with far fewer input signals.

There are also different intermod and harmonic calculation modes that can increase the simulation speed. See the 'Calculate Intermods and Harmonics' section for additional information of these modes.

Analyzer Mode

During the system simulation the analyzer will create an analyzer trace for every node in the system. Consequently, for systems with large number of nodes the integrated analyzer traces alone can be time consuming if the analyzer properties are not optimized.

The simulation speed can be reduced by a careful selection of "Analyzer Mode" settings. If large frequency ranges are integrated with a small resolution bandwidth then the amount of data collected will be much larger and the simulation speed will decrease. Furthermore, enabling the 'Randomize Noise' feature may also slow down the simulation. In order to increase the simulation speed with the 'Analyzer Mode' enabled the user can disable the 'Randomize Noise' feature, increase the 'Resolution Bandwidth', and/or limit the frequency range over which a spectrum analyzer trace will be created. See the 'Analyzer Mode' section for additional information.

Chapter 16: Menu/Toolbar

Schematic Menu

Make Components Tunable - Forces selected components to be tunable/optimizable by adding question marks to the first value of each component. This only adds question marks to part values with a numerical value. In other words, if a variable is used for a particular value, it will not be made tunable.

Make Components Fixed - Forces selected components to be non-tunable by removing any question marks that were prefixed to the first value of each component. This only removes question marks on part values with a numerical value.

Convert Using Advanced TLine - Converts all electrical transmission line elements to physical transmission line elements (microstrip, stripline, coplanar, coax, etc). Discontinuities can be added and automatically compensated for. Also substrates can be converted from one to another.

About DisCos... - Displays online help for DisCos.

Center Schematic - Centers the schematic on the page.

Fit To Page - Resizes all the parts on a schematic so that it all fits on a single page (everything is inside the dark red frame).

Reapply Auto-Designators - Reassigns standardized designators to selected components. A designator is a part name like R1 or C3. The Auto-Designator feature builds component names by using the appropriate designator prefix (like R for a resistor

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or C for a capacitor) and appending a unique sequence number to the end. When you use this menu command, the designators are applied in geometric order, from left to right.

Renumber Nodes - Renumbers all nodes in the schematic, regardless of any selection. When you use this commend, the nodes are numbered in geometric order, from left to right. Grounds are always set to 0 and nodes that connect to a port are set to match the port number. This is primarily useful before exporting a SPICE file.

Bring to Front - Move the selected objects to the front.

Send to Back - Move the selected objects to the backs.

Keep Connected - Wires will remain connected to components as they are moved. Note: The ALT key will temporarily toggle this function as long as the key is held down.

Show Part Text - Show or hide all component parameter text.

Schematic Properties - Shows the Schematic Properties dialog box, which allows you to specify settings such as: Page Width and Height, Title, Company Name, Company Address, etc.

Graph Menu

Marker Value On Right - Places marker values on the right of the graph.

Floating Marker Values - Places marker values at the classic location on the graph trace.

Marker Properties... - Opens the Marker Properties dialog box.

Marker Style - Displays a sub menu allowing easy access to commonly used marker properties.

Delete Marker - Deletes the currently selected marker.

Delete All Markers - Deletes all the markers on the current graph; it prompts yes/no before actually deleting the markers.

Show Symbols on Trace - Shows/hides the symbols (fat dots) on the trace.

Show Vertical Marker Lines - Shows/hides the vertical marker lines.

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Graph Properties... - Opens the Graph Properties dialog box.

Main Graph Toolbar

1. Update Dashed Traces. Same as selecting Update Dashed Traces from the

Actions Menu.

2. Place marker text in right margin of graph.

3. Display floating marker text beside the marker location.

4. Standard marker.

5. Change marker style to Peak.

6. Change marker style to Valley.

7. Change marker style to Bandwidth and insert 2 Delta markers..

8. Place a new Delta marker on the left side of the selected marker.

9. Place a new Delta marker on the right side of the selected marker.

10. Mark all traces.

11. Show Trace Symbols (fat dots on traces).

12. Show dashed Vertical marker lines at every marker position.

13. Display the Marker Properties dialog box.

14. Delete the selected marker.

15. Delete all markers on the current chart. (Prompts Yes/No before deleting the markers.)

Chapter 17: Filter Synthesis Examples

FILTER\Gaussian_12dB.wsp

A Gaussian filter shape is designed using the stored G values. To use this option of FILTER, go to the "G Values" tab of the Filter Properties box. Select the 'Load' button, then G12.PRO from the Proto directory. Notice the set of G values for various filter orders which fill the table of the dialog box.

For this example, the following requirements were selected: Topology Tab: Type: Lowpass, Subtype: Minimum capacitor Settings: Input Resistance = 50 ohm, Cutoff Frequency = 100 MHz, Order = 7 The resulting schematic is generated, with parameter values which meet the requirements.

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A plot of S21 and S11 are automatically produced. Notice that at the 100 MHz, the gain (S21) is -3.0104 db.

MFILTER\Chebyshev Bandpass.wsp

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Purpose: Demonstrate the use of the M/FILTER synthesis tool to generate a filter with distributed implementation. Process: M/FILTER can be used to synthesize thirteen topologies and supports variations on several of the structures. The overall design process can be divided into the following three steps:

1. Select 'Synthesis' from workspace tree. Enter 'Settings' listed above. Note plotted response and layout.

2. Select 'optimize' from 'MFilter Properties' box.

3. Perform EMPOWER simulation for optimized layout design.

The synthesis process is controlled from the 'MFilter Properties' dialog box shown below. For this example, a seventh order Chebyshev filter is to be designed and implemented in microstrip as 'hairpin' structures.

The following data was entered in this dialog box.

Topology:

Type = Bandpass Shape = Chebyshev Subtype = Hairpin

Settings:


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Input Resistance = 50 Passband Ripple = 0.05 dB Attenuation at Cutoff = 3 dB Order = 7 Low Freq Cutoff = 2000 MHz High Freq Cutoff = 2500 MHz Desired resonator Z = 60 Slide factor = 0 Tapped: checked Length of i/o lines = 20 deg.

Options:

Create a layout (checked) Manufacturing process (microstrip)

The resulting frequency response plots were generated automatically.

The M/FILTER tool also produces a schematic of linear models and a corresponding layout, as shown below.


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The layout can be used to generate DXF or Gerber type files and can also be used for electromagnetic (EMPOWER) analysis.

The second step is to optimize the design. M/FILTER automatically sets up optimization criteria based on the frequency response requirements. These criteria can be adjusted as desired. The physical parameters for the hairpin parameters can be found in the Equation block. Optimization is initiated clicking on the 'Optimize' button on the 'MFilter Properties' box. The resulting response which follows demonstrates that the design meets the requirements.


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Finally, the optimized design can be analyzed using EMPOWER to confirm the response and detect box modes. This EM simulation can be performed within the same workspace.

AFILTER\Lowpass Minimum Inductor.wsp

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AFILTER\Lowpass Minimum Inductor.wsp

A third order lowpass minimum inductor Chebyshev filter with 0.1 dB ripple and a 10 kHz cutoff is designed and simulated with mA741 op-amps. Measured results are included. The A/FILTER design schematic is shown in figure below.

This filter is designed using LC/GIC transforms. For more information on LC/GIC transforms, see Appendix E. In this particular filter, the transform yields a circuit that does not have a DC path to ground. This results in possible railing of bias voltages. To compensate, A/FILTER automatically includes a 100k resistor to ground at the output. This will work fine, as long as 100k is large compared to the impedance of the output capacitor within the filter passband. If it is not, the parallel combination of the shunt resistor and capacitor may cause a mismatch at the load. Therefore, if small valued capacitors must be used, the output resistor may need to be increased to restore the filter response.

There is an inherent loss of 6dB in this filter type. If your application requires no loss or requires gain, this can be achieved by the use of an output buffer. Output buffering is setup from the Setup menu, Preferences Window. Once enabled, the main A/FILTER window will have an input cell for gain to control the gain of the output buffer.


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Tuning the grounded resistor in each “D element” (R3 and R7 in the schematic above) directly affects the cutoff frequency. The “D elements” are independent enough that usually only one resistor needs to be adjusted unless a wide tuning range is needed.

This type is very sensitive to op-amp bandwidth. With a 1 MHz bandwidth amplifier, a 10 kHz filter may start to experience rolloff prematurely. This can usually be fixed by optimization within SuperStar.

A/FILTER automatically writes an optimization block into the circuit or schematic file. Several components within each filter type are marked for tuning and/or optimization. These parts can be used to tune the filter response back if other components are set to standard values, or vary slightly due to tolerances. (This will be illustrated in "Lowpass Multiple Feedback" example)

The following figure shows the predicted and measured responses. The circles show the response when using 347 op-amps (3 MHz bandwidth), while the triangles show the response when using mA741 op-amps (1 MHz bandwidth).

A final note on this filter type is that, even though it is a lowpass type, it will not actually pass DC due to the series capacitor at the input. If your application needs to pass DC, then a large resistor can be added in parallel to the input capacitor. The proper resistor value must be determined experimentally in SuperStar, but is generally in the neighborhood of a 100k. If the value is too large, it will have no effect; if it is too small, the filter will have gain at DC.

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AFILTER\Lowpass Minimum Capacitor.wsp

A fifth order lowpass minimum capacitor Chebyshev filter with 0.1dB ripple, 0.1dB Aa, and a 5 kHz cutoff frequency is designed and tested with mA741 op-amps. The A/FILTER design screen is shown in the figure below.

Resistors R4 and R8 can be used to completely tune the response to a different cutoff frequency. This filter is very insensitive to component tolerances, but fairly sensitive to op-amp bandwidth.

This type of filter has an inherent loss of 6dB within the passband. The circuit shown was initially constructed with 5% parts, and the response was 6.5dB down in the passband. All resistors and capacitors were replaced with 1% parts, and the new attenuation was 5.9dB.

The following figure shows the predicted and measured responses.


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AFILTER\Lowpass Single Feedback.wsp

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AFILTER\Lowpass Single Feedback.wsp

An eighth order single feedback lowpass Chebyshev filter with 0.1dB ripple, 0.1dB Aa and 10 kHz cutoff with 0dB gain is designed, simulated, and measured. The A/FILTER schematic is shown below.

This filter was designed with non-ideal op-amp parameters. In SCHEMAX, all non-tuned parts were placed on available values, and SuperStar then optimized the response to compensate. The figure below shows a plot of the predicted response of this filter. The solid trace shows the optimized response using LF347 op-amp parameters. The dotted trace shows the same circuit response, except that near-ideal op-amp parameters were added. The “ideal” response starts to roll-off prematurely, while the “non-ideal” response behaves as expected. This illustrates the necessity to correct for non-ideal elements.


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All non-tuned components were set to standard values and the filter was optimized in SuperStar to correct for the non-ideal components and for the standard values.

This filter was tuned in stages. After optimizing the overall response, the output node was moved from the output of the filter to points between each stage to allow SuperStar to show the calculated response for that stage. When the filter was constructed, each stage was tuned by referring to these cumulative responses.

The following figure shows the filter schematic modified to give the first stage response. The output of each successive stage was probed in the same way to obtain the individual responses. Note that when the second and third stages were probed that the responses are actually the cumulative response from all previous stages. The output of the fourth stage is, of course, the complete output of the filter.

The input level should be kept low, since the first section provides almost 20dB of gain near the cutoff. If the input level gets too large, the second and third sections can saturate, destroying the response. If the filter must handle larger signal levels, then the “Reverse order of poles" option in the Setup Menu, Preferences window should be toggled. In this example, the Reverse order option was set.

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AFILTER\Lowpass Multiple Feedback.wsp

A fifth order lowpass multiple feedback Chebyshev filter with a 10kHz cutoff, 0.1dB ripple and 0.1 Aa is designed and simulated with mA741 op-amp parameters. The following figure shows the A/FILTER design screen. This filter should be tuned as in the "Lowpass Single Feedback" example by placing the output between sections and tuning them separately.

In this example, all the capacitors were set to standard values, and the response was tuned using the resistors.

Element Tuning Effects:

R1 - adjusts gain with minimal perturbation of the response R4 & R5 - flattens gain, but cannot fix cutoff frequency R3 - adjusts gain of filter but distorts response R6 - redundant adjustment of R4 & R5. Only adjust if cap values are changed drastically.

R2, R4, R5 and R6 were optimized since the capacitors were changed drastically. Once optimized, only R2, R4 and R5 were adjusted on the bench.

The figure below shows the final schematic with standard value caps and optimized resistor values.


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AFILTER\Bandpass Maximum Gain Dual Amplifier.wsp

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AFILTER\Bandpass Maximum Gain Dual Amplifier.wsp

A fourth order bandpass dual amplifier Chebyshev filter with 0.1dB ripple and 0.1 Aa is designed, simulated, and measured with mA741op-amps. The following figure shows the A/FILTER schematic.

This filter should be tuned by probing between sections and tuning the sections individually. The filter response can be completely tuned by adjusting the series resistors between sections. The predicted and actual (measured) responses for this example are shown below.


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Chapter 18: SPECTRASYS Examples

SPECTRASYS\Getting Started\GS1_Setup.WSP

Illustrates: This example shows you the basic setup of a system simulation using a power input, two attenuators, an isolator, and an output port.

This example uses a AC Power input port (*INP_PAC) that contains a signal of -50dBm at 100 MHz. Next is an attenuator with a loss of 2dB. The next block is an isolator with an insertion loss of -1dB. The default isolation of the isolator is -30dB. Lastly a 3dB attenuator is made from a T configuration.

Steps:

1. Create the schematic: To place a AC Power input port, you should click on the drop down box named "Place an Input" and select "Input: AC Power". Set the frequency of the input to 100 MHz and power level to -50 dBm. Next, you want to place the attenuator and isolator blocks which are found in the "System" toolbar. Next, you will have to create the T network from resistors which are found in the "Lumped" toolbar.

2. Add a simulation: You add a system simulation by right-clicking on

"Simulations/Data" folder in the workspace window and selecting "Add System Simulation" from the drop down menu. On the "Path" page set "Path1" to "1,2" and press OK.

3. Add to your workspace:

a. Table1: Add 'Table1' by right clicking on "Outputs" folder of the workspace window and selecting "Add Table" from the popup menu. Add the following measurements: CF - Channel Frequency CP - Channel Power in dBm

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GAIN - Individual Stage Gain CGAIN - Cascaded Gain

b. Input Spectrum: Add rectangular graph by right clicking on the "Outputs"

folder of the workspace window and selecting "Add Rectangular Graph" from the pop-up menu. Set the name "Input Spectrum". Set the "Default Simulation/Data or Equations" to "System1.Path1". Add the measurement: P1 - Power of Node 1

c. Channel Power: Add a rectangular graph by right clicking on the

"Outputs" folder of the workspace window and selecting "Add Rectangular Graph" from the pop-up menu. Set the name to be "Channel Power". Add the measurement: CP - Channel Power in dBm

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EXERCISE: Change the loss of the attenuator and watch your spectrums change.

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SPECTRASYS\Getting Started\GS2_Spec_Prop.WSP

Illustrates: This example shows how SPECTRASYS displays the spectrums at every node and how measurements are defined by paths.

This example is a simple switch matrix that illustrates how every source spectrum is propagated to every node in the system, including all of the undesired sneak paths. In this particular case notice that the switches have a finite amount of port-to-port isolation. 'Input1' can be selected by setting both switch banks to control level '2'. This can be done in the tune window.

Set-up: In this example there are 4 input ports (INP_PAC) and two output ports. Each input port has a unique frequency, power level, and bandwidth. Two banks of switches are used to select any one of the 4 inputs. Each input path has an attenuator at its input. A total of 5 paths have been defined as follows:

Input1toOutput (1,2) Input2toOutput (4,2) Input3toOutput (5,2) Input4toOutput (6,2) Input4toInput1 (6,1)

Analysis:

1. Output Spectrum: The output spectrum is the power spectrum located at the output node 2. Notice that the desired signal of 100 MHz (with the switch matrix set to select 'Input2') is actually -0.5 dB below the un-desired signal of 150 MHz on 'Input4'. This is due to the off isolation of the switch 'SPDT_3' which is only 30 dB. (Flip the switch and notice the change in the output spectrum or change the isolation of 'SPDT_3').

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2. Input1 Spectrum: This spectrum shows the total spectrum (spectrum seen by a

spectrum analyzer) traveling in each direction at node 4 ('Input2' port node). One spectrum analyzer trace shows the total power leaving 'Input2' port and traveling in the direction of the output port. Another total power traces shows the power leaving the attenuator and traveling toward 'Input2'. It's each to see from these two different colored traces that the 100 MHz is traveling toward the output and all other signals are sneak signals and are arriving at the 'Input2' port.

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3. Signal Table: The channel frequency, channel power, and node sequence of each path is displayed in the table.

4. Input1 to Output: This is a level diagram showing the channel power of Input1 along 'Input1toOutput' path which is from node 1 to node 2. Multiple traces can be placed on the same level diagram but if the paths are different the data is not too meaningful since the path node numbers are different.

EXERCISE: Change the isolation requirements for all three switches to achieve at least a 20 dB signal to noise for each of the 4 outputs.

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Illustrates: how to use the various SPECTRASYS sources. SPECTRASYS can use both standard schematic sources, plus three different user defined sources.

Basics:

1. SPECTRASYS recognizes three different types of ports which are: a. INP: Standard Input Port b. INP_PAC: Input: AC Power c. OUT: Output Port Of these three ports, the INP_PAC is a schematic source since source parameters are defined in the schematic.

2. Three different user defined sources available in SPECTRASYS: a. CW: Continuous Wave (Frequency, Amplitude, and Phase) b. Modulated: (Frequency, Amplitude, Bandwidth, and Phase) c. File: (Frequency Offset, Amplitude, and Phase)

3. No spectrum will be created or processed until a schematic source or a user source has been defined.

4. User defined sources can be created and placed any of the three acceptable ports (*INP, INP_PAC, or *OUT).

5. Sources can be enable or disabled.

6. User defined sources are created and edited in the System Simulation dialog box.

7. All parameters for any source can be tuned by placing a '?' in front of the parameter to be tuned.

8. Multiple sources can be enabled at the same time on a single input or output port.

Set-up: This schematic shows a 4 way input combiner that drives an attenuator, isolator, and a coupler. Several sources are defined for the input and output ports.

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ADDING A SOURCE

1. Open the System Simulation dialog box.

2. Click the 'add' button.

3. Specify:

a. Source Name (if desired)

b. Input Port Number

c. Select the Signal Type (CW, Modulated, File)

d. Center Frequency

e. BW (Modulated Type only)

f. Power (Average)

g. Phase Shift

h. Number of Points (Modulated Type only)

EDITING A SOURCE


2. Click the 'edit' button on the row of the source to be edited.

3. Change the desired parameters.


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DELETING A SOURCE


2. Click the 'Delete' button on the row of the source to be deleted.

ADDING MULTIPLE CARRIERS

Multiple carriers can be added in two ways:

1. Individually add each carrier.

2. Use the 'step and repeat' function.

STEP AND REPEAT

The step and repeat function allows the user to quickly define multiple carriers at set intervals. The user has control over the following parameters between carriers:

a) Frequency Offset

b) Amplitude Offset

c) Phase Offset

d) Number of Signals

The Signal Type, Bandwidth, and Number of Points will be the same for every carrier.

FILE SOURCES

The user can define the shape of their source they would like in the frequency domain by using the file option. When a file source is created a file is created with the *.SRC extension that can be saved in the models directory. This file can then be reused or passed to others. This file contains a list of frequency offsets, amplitude offsets, and phase offsets. This allows the user to define a 1.25 MHz CDMA source for example and be able to use this same source over and over again at different frequencies and power levels. All file sources will automatically be loaded in the 'Signal Type' combo box if these files are saved in the 'Models' directory located under the 'GENESYS' directory.

File sources support two modes:

1) Single Sideband (SSB) - Only one half of the source needs to be specified. The other half of the source will be symmetric.

2) Double Sideband - Both the negative and positive offsets of the source need to be specified.

File example:

----------- 150 MHz File Source ------------- UNITS HZ DBC 'Nominal frequency

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FREQ 0 'If freq is zero, data is SSB offset. DATA 1e6 -3 2e6 -20 3e6 -25 4e6 -40 5e6 -100 ENDDATA -----------------------------

For more information about 'File Sources' see the simulation manual.

NOTE: All CW sources are defined to have 1 Hz of bandwidth.

The sources are listed in the SPECTRASYS dialog box shown below.

The resulting spectrum at the output contains continuous wave sources, modulated sources, and multiple frequencies defined in a file.


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EXERCISES

1. Disable sources and examine the spectrum.

2. Add more carriers to the 'Step and Repeat' source by placing a question mark '?' in the 'Number of Signals' edit box and tune this parameter to add more carriers.

3. Zoom into the carrier at 150 MHz and compare the spectrum with its file source.

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SPECTRASYS\Getting Started\GS4_Chan_Meas.WSP

Illustrates: the concept of a channel and channelized measurements.

CHANNEL DEFINITION: A channel is defined by its frequency and bandwidth. In SPECTRASYS the Channel Frequency and Channel Measurement Bandwidth determine the channel. Each path can have a different channel frequency but all paths for the same simulation all use the same 'Channel Measurement Bandwidth'. The 'Channel Frequency' is specified on the 'Paths' page of the System Simulation dialog box and the 'Channel Measurement Bandwidth' is specified on the 'General' page of the same dialog box. Furthermore, a noise channel can also be specified. However, in this particular case the 'Channel Frequency' and the noise channel frequency will be the same. The bandwidth of the noise channel on the other hand can be independently specified. Additionally, the 'Channel Measurement Bandwidth' is used to scale the broadband signals on a spectrum plot just like the resolution bandwidth does on a spectrum analyzer. For example, the power level of a 1 MHz broadband signal will be 10 dB below the specified power if the 'Channel Measurement Bandwidth' is set to 100 kHz instead of 1 MHz.

MEASUREMENTS: Many of the measurements in SPECTRASYS will use the channel in one form or another. For example the 'Channel Power (CP)' measurement will integrate the node spectrum across this channel.

Set-up:

This example contains three signal sources on a single input port.

The signals are:

a. Desired Signal at a low power level at 100 MHz

b. Interfering narrowband tone at 95 MHz at a moderately high power level.

c. Interfering broadband signal at 109 MHz at a moderately high power level.

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Furthermore, intermod, harmonic, and IP3 calculations have been disabled. In this particular example the channel frequency is set to 100 MHz and the initial channel measurement bandwidth is 1e-6 MHz (1 Hz). Consequently, the channel is defined to be from 99.9999995 to 100.0000005 MHz. The Channel Power (CP) measurement will integrate the power spectrum across this frequency range. The Noise Measurement Bandwidth is set to 30 kHz. Consequently, the noise channel is defined to be from 99.985 to 100.015 MHz. Since there is no frequency translation device in this particular example the channel frequency remains constant at every node along the path.

OBSERVATIONS

Channel Table: This table shows the Channel Frequency (CF) at every node along the path. Since the channel bandwidth is 1 Hz (1e-6 MHz) wide only the 100 MHz Desired Signal is present in this bandwidth as shown in the Channel Power (CP) measurement. The Channel Noise Power measurement is showing thermal noise in a 30 kHz bandwidth (since 10 * Log(30,000) = 45dB) then the thermal noise of -173.91 dBm/Hz + 45 dB = -129 dB/Hz). The Carrier to Noise Ratio (CNR) is simply the ratio of the Channel Power to the Channel Noise Power.

EXERCISES

1. Tune the Noise Measurement Bandwidth and notice that the Channel Noise Power changes proportionally to the Log of this bandwidth. Notice that the other

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signals present do not affect this measurement since SPECTRASYS is able to distinguish noise signals from other types of signals.

2. Tune the Channel Measurement Bandwidth and notice that once the bandwidth is 10 MHz then the 95 MHz tone will be included in the Channel Power (CP) measurement and the total power will be higher. Why do we only see -53 dBm of power for the 95 MHz -50 dBm signal when the 'Channel Measurement Bandwidth' is set to 10 MHz instead of -50 dBm? Recall that the 95 MHz signal is a CW signal that has 1 Hz of bandwidth and the signal power will be distributed from 94.9999995 to 95.0000005 MHz. Since the 10 MHz bandwidth is exact, this CW signal is split in half and we only see half power or -53 dBm. If the 'Channel Measurement Bandwidth' is set to 10.000001 MHz bandwidth then we would set the entire -50 dBm signal.

3. Continue tuning the Channel Measurement Bandwidth until the 109 MHz modulated broadband signal falls within the channel. Furthermore, notice that the modulated broadband signal at 109 MHz will have its power scaled proportionally to the Log of the Channel Measurement Bandwidth until the Channel Measurement Bandwidth exceeds the bandwidth of this 2 MHz signal. Once the Channel Measurement Bandwidth (20 MHz) exceeds the upper edge of this signal then, as one would expect, the full power of the signal (-35 dBm) has been reached and will not be scaled past that point.

ADDITIONAL OBSERVATIONS

Notice that as the Channel Measurement Bandwidth is tuned that the modulated broadband signal at 109 MHz scales proportionally to the Log of the bandwidth just as it would on a spectrum analyzer.

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Illustrates: how to view desired and undesired spectrum paths. It will show how to analyze a system to find where the unwanted sneak paths exist.

Basics:

DEFINITION:

The definition of desired spectrum is spectrum that is traveling in the same direction as the desired path. All other spectrum traveling in the opposite direction will be present at the node of interest but will be specified as undesired (even if the signals have the same frequency) since it doesn't travel along the desired path.

Set-up:

In this example two signals of the same frequency of 100 MHz are combined together. The user can examine the spectrum levels along the various paths to gain an understanding of the differences between desired and undesired spectrum.

The sources have been defined as follows:

a. Input1: CW 100 MHz, -100 dBm, 0 Deg, 1 Pts

b. Input2: CW 100 MHz, -40 dBm, 0 Deg, 1 Pts

Three paths have been defined on the 'Paths' page as follows:

a. 'Input1toOutput' 1,3

b. 'Input2toOutput' 2,3

c. 'Input2toInput1' 2,1

For this particular example any spectrum originating from Input #1 is desired spectrum along the 'Input1toOutput' path. Any spectrum from 'Input2' will be undesired. Likewise, any spectrum originating from 'Input2' is desired spectrum along the 'Input2toOther' or

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'Input2toInput1' paths. And any spectrum from 'Input1' will be undesired. The 'Data Table' has Channel Frequency, Channel Power, Desired Channel Power displayed for 'Input1toOutput' paths. The 'Desired Channel Power' measurement calculates only the desired spectrum along its specified path.

OBSERVATIONS:

1. 'Data Table': Notice how the Channel Power for the 'Input1toOutput' path doesn't begin at the anticipated level of -100 dBm but instead has a level around -90.5 dBm. This is because the high level 100 MHz source on 'Input2' has snuck through the isolation of both the 2 to 1 combiner and the isolator connected to 'Input1'. However, the Desired Channel Power correctly shows the Channel Power for the 'Input1' signals since they are traveling along the 'Input1toOutput' path.

2. 'Input2 to Input1' graph: This level diagram shows the channel power from 'Input2' to 'Input1'. I can easily be seen that the -90.5 dBm level that appears at 'Input1' is due to the 'Input2' level traveling across the isolation of the 2 to 1 combiner and backwards through the 'Input1' isolator.


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3. "Inputs to Output' graph: This graph shows both level diagrams from the inputs ('Input1' and 'Input2') to the output. This graph also shows the difference between the 'Channel Power' and the 'Desired Channel Power' along the 'Input1toOutput' path.

4. 'Input1 Spec' and 'Output Spec' graphs: Since the graphs display the entire spectrum the user is unable to distinguish between desired and undesired spectrum. Rather, the composite spectrum is shown at each node ... just like a spectrum analyzer.

EXERCISES: Use the table and level diagrams to determine the amount of combiner isolation needed so that the 'Channel Power' and the 'Desired Channel Power' are identical for the first 2 nodes along the 'Input1toOutput' path. (Note: The combiner parameters can be changed directly from the level diagram by double clicking on the combiner.)

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SPECTRASYS\Getting Started\GS6_Noise.WSP

Illustrates: how SPECTRASYS deals with broadband noise, thermal noise, and element noise generated by components.

Basics: SPECTRASYS can process large blocks of spectrum very quickly and broadband noise is no exception. Noise can come from any of three different sources. These are:

a. Excess noise of passive components

b. Added noise of active components

c. Noise source applied to an input port

NOTE:

1) Noise will not be calculated unless the 'Calculate Noise' box is checked on the System Simulation dialog box.

2) Any parameter in the System Simulation dialog box can be tuned by placing a '?' in front of the parameter.

LIMITING NOISE FREQUENCY RANGE: There is no upper frequency limit in SPECTRASYS for processing any type of spectrum. Processing frequency components that are not of interest to the user can be a waste of time and resources. SPECTRASYS provides ways to limit noise processing to the frequencies of interest by the user. On the 'Options' page of the System Simulation dialog box the user can specify the frequency range of interest. Any frequency above or below the 'Ignore Spectrum Frequency' 'Above' or 'Below' parameter will be ignored during calculations. The default value for the 'Ignore Spectrum Frequency Below' threshold is: 0 Hz. The default value for the 'Ignore Spectrum Frequency Above' threshold is: 5 times the highest source frequency. Defaults values are used when these parameters are left blank.

EXCESS NOISE: All passive components will add excess noise at a level equivalent to their loss. For example, a 3 dB pad has a loss of 3 dB (also a noise figure of 3 dB) and would add excess noise to the system corresponding to this loss. Excess noise (in dBm) is calculated as 10 Log (F-1) where F is the noise factor. The conversion of Noise Figure to Noise Factor is:

Noise Factor (F) = 10 ^ (Noise Figure / 10)

ADDED NOISE: All active components will also add excess noise at a level equivalent to their noise figure. This noise is effectively added at the input of the active stage and will be amplified by the gain of the stage. See the Excess Noise section for equations.

THERMAL NOISE: When no broadband noise source is used in the system, thermal noise will be added to the system. The noise temperature and number of points used to represent the noise are specified on the 'Calculate' page of the System Simulation dialog box.


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NOISE SOURCE: A broadband noise source can be placed on any port in the system. The user can specify the frequency limits and power level of this source.

HOW IT WORKS: SPECTRASYS uses a complicated noise correlation matrix to determine the powers levels of the noise that appear at every node in the system. The details of this matrix are beyond the scope of this discussion. Suffice it to say that excess noise, added noise, thermal noise, and noise sources are all taken into account.

CHANNEL NOISE POWER: The Channel Noise Power is the total integrated noise power that exists within the channel. This is the base noise measurement that is used for many other noise measurements.

ANALYZER MODE: The 'Analyzer Mode' is basically a virtual spectrum analyzer. The user can enable 'Randomize Noise' to give the appearance of random noise that is present in spectrum analyzers. This parameter does not affect any of the channelized noise measurements and is used for visual effects only. Furthermore, the user can set the noise floor of the analyzer mode to a value representative of his instrument. Typical spectrum analyzers have noise floors in excess of 154 dBm per Hz. This allows the user to see data during the simulation that will be more representative of what will be measured in the lab. The 'Analyzer Mode' parameters are located on the 'Composite' page of the System Simulation dialog box.

OBSERVATIONS:

1. 'Main Path' graph: This level diagram shows the channel power along the main path of the system. The input noise power at the 'Main' input is thermal noise which is -173.91 dBm/Hz for a system that is at 21° C. Since the channel bandwidth is 1 MHz then the total noise power is going to be -173.91 dBm/Hz + 10 Log(1e6) = -113.91 dBm. Since the "gain + noise figure" of the amplifier is 25 dB, then the noise power at the amplifier output is 25 dB higher or -88.91 dBm. The attenuator after the amplifier will attenuate the total noise by the loss of the attenuator since the noise level is way above thermal noise. However, at the output of the coupler the channel noise power is much higher because we have a broadband noise source being fed into the coupled port. The noise source placed on the 'Noise' port is at -120 dBm/Hz. Since the channel bandwidth is 1 MHz then the total input noise power is -60 dBm. After passing through the 5 dB attenuator and the 10 dB coupler the resultant noise power level at the output is about -75 dBm. The total power is slightly higher that this because the noise along the main path is also added in.

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2. 'Amp Out' graph: Notice that at the amplifier output there are two total noise power traces that represent noise traveling from two directions (one from the output of the amplifier travelling to the output port and the one from the attenuator traveling to the 'Main' port.) From this spectrum plot the user can quickly identify the broadband noise source from 0 to 200 MHz that is travelling from the 'Noise' port to the 'Main' port.


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EXERCISES FOR THE USER

1. Disable the Noise source in the Systems Simulation dialog box. Notice how the total noise on the last node of the 'Main Path' level diagram is now much lower and only represents the noise along the main path.

2. Tune the 'Ignore Spectrum Frequency Above' parameters on the Systems Simulation dialog box. Observe the noise power levels on the graphs and level diagram to get a better feel for how SPECTRASYS uses this parameter to determine the broadband noise frequency.

3. Tune the 'Channel Measurement Bandwidth' on the System Simulation dialog box by a factor of 10 and notice how the noise power also changes by 10 dB.

4. Disable the 'Randomize Noise' on the 'Analyzer Mode' and observe the effect on the spectrum plots.

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SPECTRASYS\Getting Started\GS7_Coherent.WSP

Illustrates: how SPECTRASYS deals with coherent and non-coherent addition of signals.

Basics: SPECTRASYS is able to determine which spectrums are coherent and which ones are not. Basically, any signal being derived or created from the same source is coherent. Any other signal sources are considered non-coherent. Furthermore, a noise source is coherent with itself but will not be coherent with other noise signals.

Set-up: A single broadband signal source have been created at 'Input' port at a center frequency of 100 MHz, bandwidth of 20 MHz, and a power level of -50 dBm. This signal is split two ways and is amplified by parallel amplifiers. When these signals are combined back together at the amplifier output their power will be 6 dB higher than each individual signal since these signals are coherent and in phase.

OBSERVATIONS:

1. 'Output Spec' graph: This spectrum graph shows three components of the spectrum at the parallel amplifier output. One piece of the source signal travels from the input to the output through the top amplifier and the other travels through the bottom amplifier. The last spectral component is the total power. As can be seen from the marker text on this graph the user can identify both of the components traveling through the top and bottom amplifiers with their respective levels and the total power level at the amplifier output. As expected the user can see that these two spectral components have been added coherently since the total is 6 dB higher than the individual component level.

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EXERCISES:

1. Enable the second source which is identical to the first source in the System Simulation dialog box. Notice that the total power level at the at the output only increases by 3 dB. What is the reason? Answer: Both of the two system sources are independent and are considered non-coherent. Consequently, the total power only increases by 3 dB.

2. Tune the phase of the one of the paths. What happens to the output signal when the difference in phase between the paths are 180 degrees? What does the level diagram look like in this case. Notice how it is much easier to the see the signal cancellation that is taking place on the level diagram than a spectrum plot.

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SPECTRASYS\Getting Started\GS8_Intermods.WSP

Illustrates: how SPECTRASYS deals with intermods and how the non-linear devices handle these intermods. The user will also understand the difference between generated, conducted, and total third order intermod power.

Basics:

There are two intermod modes in SPECTRASYS:

Manual (Advanced) Mode: For this particular mode the user must create a minimum of 3 sources. The first source represents the desired signal and the corresponding channel frequency. The two other sources are the actual 2 tones that are used to create intermods in the channel. The user must make sure that the desired signal and the two interfering tones are spaced properly such that intermods will fall within the bandwidth of the desired channel. Furthermore, for this particular technique there is no restriction on the number of interfering signals used to create the intermods. The total intermod power found within the channel will be used to determine the actual output and input intercept points. For this mode of operation the user needs to only specify the frequency offset from the desired channel to the first interfering tone. If at least 3 sources are not created at the correct frequencies and the tone offset is not set correctly intermods will not appear within the channel and the perception will be that intermods are not working. This mode is enabled when the 'Manual (Advanced)' checkbox has been checked.

Automatic 2 Tone: In this particular mode SPECTRASYS will create the needed 3 sources to calculate intermods and intercept points. However, in this case the user needs to specify some additional information such as the 'Input Port', 'Tone Spacing', 'Gain Test Power Level', and the '2 Tone Power Level' parameters. Three sources are needed to make intermod measurements. The first source is created at the channel frequency and is used to determine the 'in channel' gain of the chain. The user must specify the level of this source through the 'Gain Test Power Level' parameter. This level should be above the noise floor and be well below the level that would cause non-linear behavior. The 'Input Port' specifies the port where the 3 signal sources are created. The 'Tone Spacing' determines the spacing between the desired channel and the first interfering tone. This same spacing is also used between the two interfering tones. Because of this spacing we are guaranteed that intermods will be created in the channel. The '2 Tone Power Level' is used to specify the actual level of both interfering tones. For the 'Input Third Order Intercept (IIP3)' and 'Output Third Order Intercept (OIP3)' measurements the '2 Tone Power Level' doesn't really matter since these parameters are based on relative measurements. However, this '2 Tone Power Level' is very important when determining the absolute intermod power level and should be set according to the maximum interference levels seen by the circuit. This mode is enabled as long the 'Manual (Advanced)' checkbox is unchecked.


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SPECTRASYS creates intermods for all input sources driving non-linear elements such as amplifiers and mixers. All linear elements will not create intermods. However, these elements will conduct them from prior stages where they were created. The 'Total Third Order Intermod Power (TIM3P)' can be separated into two distinct groups of intermods. The first group is 'Generated' intermods and the second is 'Conducted' intermods from a prior stage. SPECTRASYS is able to separate intermods into these two groups. This allows the user to quickly determine the weak intermod link in a cascade of stages. This total is the non-coherent sum of the Generated and Conducted Third Order Intermod Power. 'Generated Third Order Intermod Power (GIM3P)' is the total third order intermod power that is created in a particular stage. This measurement will only show the intermod levels for the stages that created them. 'Conducted Third Order Intermod Power (CIM3P)' is the total third order intermod power conducted in from the prior stage. This measurement when used in conjunction with the 'Generated Third Order Intermod Power (GIM3P)' will help the user quickly identify the stages in the chain that are the weakest link and are the highest contributor to the intermods. The stage prior to the stage where the conducted intermods are dominant through the rest of the chain is the weak link in the chain.

Set-up:

This example uses two cascaded amplifiers amongst other passive stages such as attenuators and a coupler. The 'Manual (Advance)' intermod test is illustrated in this example. Three input signal sources have been created. Two CW interfering tones at 80 and 100 MHz each having -20 dBm output power. The other signal source is a desired signal at 60 MHz having a power level of -120 dBm. The channel frequency is 60 MHz.

Analysis:

1. 'Amp #1 In' - This spectrum plot shows the small desired input signal at 60 MHz and the two interfering tones at 80 and 100 MHz at the input of the first amplifier. The power level of each of these interfering tones is -20 dBm.

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2. 'Amp #1 Out' - This spectrum shows the resulting third order intermods created from the two input tones at the output of the first amplifier. The output power of each tone is -10 dBm. Since the output IP3 of the first amplifier is +20 dBm then the difference between the tone the output IP3 is 30 dB. The output power of the third order intermods will be twice this delta value below the tone output power. This results in third order intermod power levels of -70 dBm. (The actual values in the table may be slightly lower due to the reduced amplifier gain with larger power input signals).


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3. 'Amp #2 In' - This spectrum shows the total input spectrum to the 2nd amplifier. This spectrum consists of the three source signals and the third order spectrum created from the first amplifier.

4. 'Amp #2 Out' - This spectrum shows the total output spectrum of the 2nd amplifier. This spectrum is the combined spectrum from the intermods that were conducted from the output of the 1st amplifier to the output of the 2nd amplifier and the intermods generated from the 2 interfering sources by the 2nd amplifier. The two intermod spectrums (conducted and generated) are combined non-coherently to get the total output spectrum.

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5. 'Intermod Table' - This table shows us the numeric values of the Channel Frequency, Channel Power, Generated Third Order Intermod Power, Conducted Third Order Intermods, Total Third Order Intermod Power, Gain of each stage, the first interfering Tone Channel Frequency, the Tone Channel Power, and Cascaded Gain.

6. 'Intermod Diagram' - This level diagram is one of the most useful graphs in this example. This level diagram shows the Generated, Conducted, and Total Third Order Intemod Power along the main path. From this graph the user can quickly identify that the first amplifier stage is the weak link in the chain. In other words, the 'generated' intermods at the output of the first amplifier are dominant and every subsequent stage is dominated by the 'conducted' intermods. Better intermod performance can be achieved by redistributing the gain between the first and second amplifiers.


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TONE DISSIMILAR AMPLITUDE: In most cases, analysis on devices assume the tone inputs have equal amplitude. Mathematically, this is the most convenient or easiest way to analyze intermod distortion. However, this method is not always an accurate model of the real problem. When both input amplitudes are equal, the third order IM product level changes 3 dB for every 1 dB change in amplitude. However, when you have dissimilar interfering tone amplitudes the adjacent tone will change by 2 dB for every 1 dB. The alternate tone will change 1 dB for every 1 dB of change.

CHANNEL BANDWIDTH AND INTERMODS: The bandwidth of third order products is greater than the individual bandwidth of the sources that created them. For example, if two 1 Hz tones were used to create intermods the resulting intermod bandwidth would be 3 Hz. The bandwidth follows the intermod equation that determines the frequency except for the fact that bandwidth cannot be subtracted. For example, if the third order intermod equation is: Fim3 = F1 - 2*F2 then the equation for the resulting bandwidth would be: BWim3 = BW1 + 2*BW2. If BW1 = 30 kHz and BW = 1 MHz then the resulting bandwidth would be 2.03 MHz. The user needs to make sure that the 'Channel Measurement Bandwidth' is set wide enough to integrate all of this energy.

EXERCISES:

1. Redistribute the gain between the first and second amplifiers to lower the total intermod power at the output of the cascade (node 2). Make sure that the cascaded gain still remains the same (10 dB). One Solution - The total intermod power at the output can be improved by over 5 dB by simply reducing the gain of the first stage from 20 to 16 dB of gain and increasing the gain of the second stage from 10 to 14 dB. The cascaded gain will still be 10 dB.

2. Go into System Simulation dialog box and change the 80 MHz tone source power to -21 dBm. Check each graph, and you will see the difference in tone amplitudes and IM amplitudes. Now go back into System1 properties and change the 100 MHz tone power level to -21 dBm. As you will see, both tones match each others and both IM's are now equal in amplitude as well. (The actual intermod power between the close in intermods (F1 - 2*F2 or F2 - 2*F1) may be slightly different due to other intermods falling on these same frequencies ... other factors such as impedance and frequency roll-off can also contribute to this difference).

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SPECTRASYS\Getting Started\GS9_Mixers.WSP

Illustrates: how SPECTRASYS simulates mixers as part of RF systems. Basics: The current mixer model in SPECTRASYS is a non-linear model that uses a 1dB compression point, a third order intercept point, a second order intercept point, and a saturation point. Furthermore, the user is able to specify the isolation parameters of the mixer along with the desired output product: sum or difference. The user can also specify the conversion loss and the LO level of the mixer. One of the uses of the LO Drive Level specification is to provide SPECTRASYS with the absolute power level of the LO so that the user can be notified if the actual LO power is outside the target LO power level range specified on the 'Options' page in the System Simulation dialog box. SPECTRASYS will process all isolation spectrum, LO to RF, RF to IF, and LO to IF. The mixer will also create third order intermods from all of its input sources. Obviously, sum and difference frequencies between all the input signals and all LO signals will be created. During the initial calculation process, SPECTRASYS ignores the desired signal direction through the mixer and signals on either the RF or IF side of the mixer will be converted to the appropriate sum and difference frequencies.

Set-up: This example contains a mixer with a filter and RF amplifier in the IF chain. Through equations the RF and the LO frequency are tied together so the channel can be changed by simply changing the RF frequency. The initial RF input frequency is 100 MHz and the LO frequency is 90 MHz. Since we have told the mixer that the desired mixer output is a 'difference' and not a 'sum', then the desired IF frequency will be 10 MHz.


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Analysis: 1) 'Mixer Out' graph - This graph shows the isolation (90 and 100 MHz) and sum and difference (190 and 10 MHz) outputs of the mixer. Notice that the level of LO leakage at the mixer output is much larger than the desired sum or difference frequencies. This large LO leakage level can easily drive a subsequent IF amplifier into compression unless that component is filtered.

2) 'IF Out' graph - This graph shows the IF output. The user will be able to see the 10 MHz output as well as the 2nd harmonic of the IF (even though this level is really low). Other components such as the LO leakage and other spurious responses can be seen. Furthermore, this spectrum gives the user a visual indication of the signal to noise ratio at this point in the RF chain.

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3) 'RF In' graph - This shows the spectrum at the input port. The 100 MHz input signal source can be seen along with the LO radiation signal at 90 MHz. The user should verify that the spurious responses at this point meet the regulatory requirements (i.e. FCC, ETSI, etc.)

4) 'Budget Table' - This table gives a general performance overview of this simple down-converter. This table shows the Channel Frequency, Channel Power, Channel Noise Power, Carrier-to-Noise Ratio, Cascaded Gain, and Cascaded Noise Figure. Many other parameters could have been presented in the table.


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Exercises: 1) Tune the 'RF' input signal and observe the spectrum at 'RF In', 'IF Out', and 'Mixer Out'. 2) Tune the Noise Figure of the amplifier and observe the cascaded noise figure, channel noise power and 'IF Out' spectrum. 3) Examine the spectrum at other nodes in the system. 4) Plot the Channel Power of the LO from the LO port to the RF input port. 5) Make the Loss in Attenuator ATTN_2 tunable. Adjust the loss until the Mixer is "starved". The Mixer symbol on the schematic will turn orange. What value of loss causes this condition? ( Answer: In the Mixer requirements, the "LO Drive Level" is 7 dBm. On the "Options" page of the System Simulation Parameters dialog box, the Mixer Warning (out-of-range) is set at +/- 2 dB. Therefore, when the 10 dBm level of the LO drive is reduced by 5 dB by the attenuator, then the resulting 5 dBm is at the lower threshold of 7 +/- 2 dBm.)

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SPECTRASYS\Amplifiers\Feed Forward Amplifier.WSP

Illustrates: the operation of a dual loop feed forward amplifier. Basics: The power that can be achieved from a power amplifier will be largely determined by the non-linearities in the high power amplifiers stages. A dual loop feed forward amplifier can be used to reduce the level of the intermods at the power amplifier output. The first loop of the feed forward amplifier will combine the non-linear output spectrum from the main amplifier with a phase and amplitude shifted input spectrum. These two spectrums will be combined coherently and the input carriers will be cancelled if the carriers are 180 degrees out of phase and of the same amplitude. We then end up with only intermods in the spectrum. The second loop will amplify and phase shift the intermod only (error) spectrum and it will be added back into the main amplifier path to cancel out the intermods from the output of the power amplifier. These two intermod spectrums must be180 degrees out of the phase and the same amplitude. Since amplifiers and other circuits have delay, a delay line needs to be added to shortest delay path so that the spectrums can arrive at the same time. Phase shifters and gain adjustments are typically added so that the power amplifiers can be adjusted during manufacturing. Set-up: RFAMP_1 is the main amplifier. Input signals from port 1 will be amplified by this amplifier and intermods will also be created. A sample of this distorted spectrum will be taken at COUPLER1_2 this will be passed toSPLIT2_1 where it will be combined with the delayed input spectrum.


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A sample of the undistorted input spectrum is taken from COUPLER1_1 and then delayed by about 190 degree by the delay line (RF_DELAY_1). This delay line must be added because there will be delay through RFAMP_1. Enough delay is added to place our phase adjustment (RF_PHASE_1) for this first loop at a good center point in its adjustment range. Out the output of SPLIT2_1 the input carriers will be canceled if they have the same amplitude and are 180 degrees out of phase. ATTN_VAR_1 is used to adjust the amplitude balance of the carriers. The user can examine the 'Error Amp Spec' graph to see the amplitude error and the 'Error Phase' graph to see the phase error of the carriers at the splitter output. The intermod only spectrum at the splitter output will be amplified by RFAMP_2 (error amplifier) and will be combined back into the main path through COUPLER1_3. A delay line (RF_DELAY_2) is about 370 degrees long so that the phase shifter (RF_PHASE_2) of the second loop will be set at a good nominal center point. The intermods at the output (port 2) must be the same amplitude and 180 degrees out of phase. ATTN_VAR_2 is used to adjust the amplitude of the intermods. Observations:

1. The user can examine the output spectrum on the 'Out Spec' graph. With the 'Analyzer Mode' enabled, the user is able to see the output of the power amplifier. Furthermore, having composite spectrum show the individual spectral components, we can quickly see the cancellation level between the individual pieces of the intermods and the actual output.

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2. SPECTRASYS knows the direction of travel of all spectral components at every

node in the system. The total power is represented by a trace for every travel direction at a node. By examining the 'Input Spectrum', the user can see the two input signals traveling from the input port into the power amplifier. Furthermore, the user can also see intermods and other spectrum traveling from inside the power amplifier to the output.

3. With individual components enabled for the composite spectrum, it is very easy

to identify the origin and path the spectrum takes to arrive at the examination point. By placing a marker on the intermod at 1958 MHz the user can identify all of the pieces of spectrum that make up that intermod and the path that it took to get to the input node. We see that the largest offender is -54.1 dBm (marker 'c') and its frequency is 1958 MHz which is the result of the frequency of source 1 minus the 2nd harmonic of source 2 [S1-2xS2]. This intermod was created at node 6, the output of RFAMP_1. It then propagated to nodes 7,9,13,12,3,12,13,9,14,15,1. We can see that the weak link in the chain is the reverse isolation of RFAMP_2.

4. Adjacent channels can be defined at the intermod frequencies to examine the intermods power along the main path. This can be seen on the 'ACP' (Adjacent Channel Power) level diagram. Through most of the main path in the system, notice how the intermod power of the 1952 and 1958 MHz intermods are at the same power level. From this level diagram the user can quickly see that the intermods are being created in RFAMP_1 and we can also see the cancellation of the intermods at the output. Furthermore, we see the intermod energy reappearing at the amplifier input.


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5. Optimization targets have been added to minimize the adjacent channel power.

Examining the optimization targets we can see that the adjacent channel power is trying to be minimized from Min=7 to Max=7. Since adjacent channel power (ACP) is a path (level diagram) measurement we need to tell GENESYS which node to perform the optimization. The user must specify the node index along the path and NOT the node number. Looking at the 'ACP' level diagram and starting with an index of 0 we see that the 7th index is at node 2. 7 in the index that we need to place in the optimizer for all level diagram measurements.

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Exercises: 1. Tune RF_PHASE_1 and examine the phase of the carriers traveling through both paths on the 'Error Phase' graph. Notice the path of amplified spectrum (marker c) and the input sampled path (marker d). The phase difference of these signal is 180 degrees to get the best cancellation. 2. Tune RF_PHASE_2 and examine the phase of the intermods traveling through both paths on the 'Out Phase' graph. Notice path of main spectrum (marker c) and the input sampled path (marker d). Again, the phase difference of these signal is 180 degrees to get the best cancellation. 3. Tune ATTN_VAR_1 and ATTN_VAR_2 and watch the respective amplitude balance for the carriers and intermods with the 'Error Spec' and 'Out Spec' graphs. 4. Tune the reverse isolation of RFAMP_2 and observe the intermod spectrum on the input ('Input Spectrum' graph) and notice that the improvement will change linearly with this isolation until the next dominant component is reached. 5. Run the optimization and notice the improvement in performance.

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Abstract: The hybrid matrix amplifier is a popular power amplifier configuration that incorporates redundancy. With the traditional design of using a single power amplifier for every transmitter the power amplifier becomes a single point of failure. If the amplifier dies, then so does the carrier and all of the transmitted information. The hybrid matrix amplifier will still provide output power (albeit a lower output power ... due to the loss of one amplifier) for all input signals. Furthermore, the reliability of power amplifiers is typically lower than the transmitter, so the likelihood of losing a carrier can be very high. Background: 90 Degree hybrid couplers are used at the input to shift each input signal (IN and ISO) by 90 degrees (ISO to 0 is a 90 degree shift and ISO to -90 is a 0 degree shift). These hybrid couplers are also used on the output to combine the amplified signals back together. Because of the phasing, carriers will either add or cancel at the output leaving a dedicated output for each carrier.

To illustrate this point let's look at a simple dual hybrid matrix amplifier (HYBRID1_1, RFAMP_1, RFAMP_2, and HYBRID1_2). Signals at the IN port of HYBRID1_1 will have a 90 degree phase shift into RFAMP_2 and a 0 degree phase shift into RFAMP_1. The output of RFAMP_2 will have a 0 degree phase shift at the -90 output port of the HYBRID1_2. This same signal that has a 0 degree output through RFAMP_1 will go through a 90 degree shift through HYBRID1_2 and will add constructively at the -90 output port to produce the desired, amplified output. However, RFAMP_1 will produce a

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total 0 degree phase shift at 0 port of HYBRID1_2 and RFAMP_2 will produce a total 180 degree phase shift at this same port and the signal will cancel. Consequently, the output port for the dual hybrid matrix amplifier is the -90 port of HYBRID1_2 for and the IN port of HYBRID1_1. The user can use the same logic to examine and verify that signals on the ISO port of HYBRID1_1 will appear at the 0 port of HYBRID1_2. Set-up: The following table shows the corresponding output ports for the input port and paths for the quad hybrid matrix power amplifier. Input Port Output Port Path Frequency 1 8 TXA 1800 MHz 2 7 TXB 1810 MHz 5 4 TXC 1820 MHz 6 3 TXD 1830 MHz Amplifiers specified along the path have been arbitrarily defined for each path since every amplifier will amplify each input carrier.

Observations:

1. Output spectrums are available for each output. The user can verify by looking at these outputs that the correct carrier is present and all of the other carriers have been cancelled. Consider the TXA output at frequency 1800 MHz. By zooming in on the 1800 MHz region, note that the other carriers are about 37 db lower than the primary output.


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2. Level diagrams have also been added for each input. Notice that the loss through

the input hybrid couplers is equal to the 3 dB splitting loss plus the insertion loss. However, the output couplers show a gain of 3 dB (because of the coherent addition taking place at that node) and a loss equal to the insertion loss.

Exercises:

1. Tune the isolation of the hybrid couplers and observe the levels of the cancelled carriers. Notice that a large change in isolation doesn't affect the cancelled carriers levels much. However, as the isolation is lowered spectrums will propagate for a longer period of time and the simulation will take longer to run.

2. Set the gain of one of the amplifiers and examine the power at each output. Notice every carrier is still present, even though the power for each carrier is lower.

3. Change the 'Phase Balance' of HYBRID1_6 to 5 degrees and notice the A (1800 MHz) and B (1810 MHz) carriers are not cancelled as much as the other carriers.

4. If we want to improve the performance of the carrier cancellation, the user must understand the origin of the spectrum at those carrier frequencies. Since the carriers are evenly spaced, intermods will also appear at those carrier frequencies. To determine the origin of this spectrum, enable the 'Signal', 'Intermods and Harmonics', and 'Show Individual Components ...' and place a marker at 1800, 1810, 1820, or 1830 MHz. Notice that both carrier intermods and other components are present.

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SPECTRASYS\TX & RX\TX and RX Chain.WSP

Abstract: This example shows a complete path through a transmitter and transmit/receive antennas and finally through a receiver.

Set-up: The schematic, as shown below, has a main path from transmitter IF to receiver IF. The frequencies simulated were:

Transmitter: IF = 220 MHz, LO = 1740 MHz, RF = 1960 MHz

rRceiver: IF = 150 MHz, LO = 2110 MHz, RF = 1960 MHz

Observations: The transmit path, shown below, begins at source # 1 and ends at the input to the transmit antenna. Notice the increase in channel power from -10 dBm at the input to over 34 dBm at the antenna.

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The transmitter output spectrum includes harmonics from the mixer and amplifiers. Only the total spectrum was selected for computation and plotting.

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The channel power along the entire path clearly shows the attenuation of the radiated path between antennas.

Exercises:

1. Vary the LO frequencies and observe the effect on channel power.

2. Add intermods and re-compute the outputs.

3. Adjust the LO power and "starve" the mixers. Observe the results.

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Abstract: This example demonstrates the use of a duplexer for a common antenna used by transmit and receive channels. The issues related to the filter design parameters and performance are examined. In particular, the effects of the transmit signal and noise in the receive band are simulated.

Set-up: The path of the transmit signal is from source # 1, through amplifier (RFAMP_1), and then through channel 'A' of the duplexer. The transmit signal is centered at 1960 MHz with a 1.25 MHz bandwidth. The upper edge of the receive band is at 1910 MHz. The duplexer is formed by two fifth order Elliptic bandpass filters. The passband for channels 'A' (transmit) and channel 'B' (receive band) are 1930 - 1990 MHz and 1850-1910 MHz, respectively. The linear response of the duplexer filters is shown below.

Observations: Notice that the duplexer filters for both channels are identical. The ripple is 0.5 db. The insertion loss is also 0.5 db. Attenuation in the stopband is 80 db. Of interest is the spectrum of the noise at the input to the receiver LNA (node # 9). The plot below shows the components from the duplexer and reflected power from the receiver LNA. Also shown is the source signal of 160 MHz through the amplifier and duplexer. Finally, the level diagram gives insight into the source of the noise from the duplexer. The large increase in noise power through the transmitter amplifier (+10 db) is only partially offset by filtering (-3 db).

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Exercises:

1. Adjust the noise figure of the transmit amplifier. Observe the effect on the receiver noise power.

2. Determine the sensitivity to changes in the filter order, ripple, and stopband attenuation. Why does an increase in the filter order from 5 to 7 have such a dramatic improvement in the noise response?

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SPECTRASYS\Transmitters\Diversity TX and Hybrid Amp.WSP

Abstract: This example includes two transmit channels combined through a hybrid amplifier. Two mixers are used to up-convert the modulated inputs up to RF frequencies.

Set-up: The sources # 1 and # 3 are 220 MHz modulated signals, which are combined with local oscillator signals of 1735 MHz and 1745 MHz, respectively. The resulting "sum" frequencies are 1955 and 1965 MHz. See example: SPECTRASYS\Amplifiers\Quad Hybrid Matrix Amp.WSP for a discussion of hybrid amplifiers. Except for the LO frequencies, the two channels are identical.

Observations: The transmitter output from source # 1 appears at node # 6, as shown below. Notice the significant power at the other (1965 MHz) RF frequency. Insight into this effect is obtained from phase measurements.

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GENESYS provides for a phase measurement of the node voltage at any node. Of particular interest is node # 6. The phase of each of the component at 1965 MHz is given. Notice that the paths are identified by node numbers along the path.

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Channel power is plotted below in a level diagram for the LO power contribution to Output # 1 (i.e. node 5).

Exercises:

1. Use power and phase measurements to identify system deficiencies, and make corrections.

Chapter 19: Measurement Overview

Overview

GENESYS supports a rich set of output parameters. All parameters can be used for any purpose, including graphing, tabular display, optimization, yield, and post-processing.

See also Linear Measurements, Non Linear Measurements, and Operators for additional information.

Linear Measurements

The following table shows the available Measurements. Where i and j are shown in the chart, port numbers can be used to specify a port. Some parameters (such as Ai) use only one port, e.g., A1 or VSWR2. Or, on a tabular output, the ports can be omitted (ie, S or Y), and measurements for all ports will be given.

Note: All available measurements and their operators for a given circuit or sub-circuit with their appropriate syntax are shown in the measurement wizard. To bring up the measurement wizard select "measurement wizard" from the graph properties dialog box.

Note: The section in this manual on S Parameters contains detailed information about many of these parameters.

Meas. Description Default Operator

Shown on Smith Chart

Sij S Parameters DBANG Sij Hij H Parameters* RECT -- YPij Y Parameters RECT -- ZPij Z Parameters RECT -- ZINi Impedance at port i with network terminations in

place RECT Sii

YINi Admittance at port i with network terminations in place

RECT Sii

ZPORTi Reference Impedance at port i RECT VSWRi VSWR at port i Linear (real) Sii Eij Voltage gain from port i to port j with network

terminations in place. DBANG --

Nij Noise correlation matrix parameters RECT -- GMAX Maximum available gain* dB (real) -- NF Noise figure* dB (real) -- NMEAS Noise measure* Linear (real) -- NFT Effective noise input temperature* Linear (real) --

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GOPT Optimal gamma for noise* DBANG GOPT YOPT Optimal admittance for noise* RECT GOPT ZOPT Optimal impedance for noise* RECT GOPT RN Normalized noise resistance* Linear (real) -- NFMIN Minimum noise figure* dB (real) -- ZMi Simultaneous match impedance at port i* RECT GMi YMi Simultaneous match admittance at port i* RECT Gmi GMi Simultaneous match gamma at port i* DBANG GMi K Stability factor* Linear (real) B1 Stability measure* Linear (real) SB1 Input plane stability circle*

Note: Filled areas are unstable regions.

None (Circle)

SB1 Circles

SB2 Output plane stability circle*

Note: Filled areas are unstable regions.

None (Circle)

SB2 Circles

NCI Constant noise circles* (shown at .25, .5, 1, 1.5, 2, 2.5, 3, and 6 dB less than optimal noise figure)

None (Circle)

NCI Circles

GA Available gain circles** None (Circle)

GA Circles

GP Power gain circles** None (Circle)

GP Circles

GU1 Unilateral gain circles at port 1** None (Circle)

GU1 Circles

GU2 Unilateral gain circles at port 2** None (Circle)

GU2 Circles

*Can only be used on 2-port networks **Gain circles are only available for 2-port networks. Circles are shown at 0, 1, 2, 3, 4, 5, and 6 dB less than optimal gain. In GA and GP, if K<1, then the 0dB circle is at GMAX, and the inside of this circle is shaded as an unstable region.

Note: On a graph or in optimization, measurements which use DBANG by default show the dB part, measurements which use MAGANG show the magnitude, and measurements which use RECT show the real part.

Note: For port numbers greater that 9 a comma is used to separate port numbers. For example, on a 12 port device some of the S-Parameters would be specified as follows: S1,11 S12,2 S12,11 S12,2 .

Nonlinear Measurements

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Meas. Description Default Operator

Shown on Smith Chart

Vnode Peak Voltage at node (node is the node number or the name of the node as specified by the voltage test point designator name)

MAG --

Iprobe Peak Current through probe (probe is the current probe designator name)

MAG --

Pport RMS Power delivered at port (port is the port number) DBM --

Operators

Measurements are combined with operators to change the data format. The general format for combining operators with measurements is:

operator[measurement] or

operator(measurement) where operator is one of the operators listed in the table below and measurement is one of the measurements listed in the table in the previous section.

Also available is the @ operator which may be combined with any other measurement to select a subset of a sweep. Its format is:

operator[measurement]@value where value is the independent value or range to pull data from. For ranges, separate values by : (colon).For multidimensional data, multiple ranges can be specified, separated by commas. The values can be the actual independent (frequency, etc.) data or can be #index, where index is the zero-based index of the data to use (such as a harmonic number in a nonlinear simulation). Some examples:

S21@900 Gives all data from S21 at 900 MHz. If the data comes from a parameter sweep, then the result will be a sweep of values, all at 900 MHz, vs. the swept parameter.

P2@#3

Returns the power in dBm at port 2 at the fourth data point (counting DC, that is the third harmonic for a single tone simulation).


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MAG[V5]@0:3,1:3 Returns the magnitude of the voltage at node 5, from 0 to 3 for the first swept parameter and from 1 to 3 for the second parameter.

All measurements have default operators. For instance, on a table, using S21 will display in dB/angle form and Z32 will display in rectangular (real & complex) form. Likewise, on a graph, S21 graphs in dB, while Z32 graphs the real part of Z32.

Note: To avoid confusion, measurements used in equations for post-processing must specify an operator.

Operator Description Meas. must be Result Is MAGANG[] Linear magnitude and angle in range -180 to

180 Complex Complex*

MAGANG360[] Linear magnitude and angle in range 0 to 360 Complex Complex* DBANG[] dB magnitude and angle in range -180 to 180 Complex** Complex* DBANG360[] dB magnitude and angle in range 0 to 360 Complex** Complex* RECT[] Rectangular (real + imag) Complex Complex MAG[] Linear magnitude Real/Complex Real ANG[] Angle in range -180 to 180 Complex Real ANG360[] Angle in range 0 to 360 Complex Real RE[] Real part of complex measurement Complex Real IM[] Imaginary part of complex measurement Complex Real DB[] dB Magnitude Real/Complex** Real GD[] Group delay Complex Real QL[] Loaded Q [ QL = (2 pi f) GD / 2 ] Complex Real TIME[] Converts Frequency domain to Time domain

via inverse Fourier Transform. Intended for use with Voltage/Current to get time waveforms.

Complex Real

*For post-processing equation purposes, the magnitude is in the real part of the result, and the angle is in the complex part of the result. **Only the following parameters can be displayed in dB form: S, GM, E, GOPT, GMAX, NF, NFMIN, and NMEAS.

Note that not all operators can be used with all measurements. The "Measurement must be" column above indicates which type of parameter each operator can use. For example, ANG[] (Angle) cannot be used with a real-valued parameter, such as GMAX, so ANG[GMAX] is not allowed.


Sample Measurements

203

Sample Measurements

Measurement Result in graph, Smith chart, optimization, or yield

Result on table

S22 dB Magnitude of S22 dB Magnitude plus angle of S22

QL[S21] Loaded Q of S21 Loaded Q of S21 MAG[S21] Linear Magnitude of S21 Linear Magnitude of S21 IM[Zin1] Input reactance at port 1. On a Smith

chart, S11 will be displayed, while IM[Zin1] will be used for the marker readouts.

Input reactance at port 1

S --- Shows dB Magnitude plus angle of all S Parameters

RECT[S] --- Shows real/imaginary parts of all S Parameters

SB1 On Smith or polar chart, shows input plane stability circles

Displays center, radius, and stability parameter of input plane stability circles

NCI On Smith or polar chart, shows constant noise circles

Displays center, and radius of all noise circles (27 numbers per frequency)

Using Non-Default Simulation/Data

In all dialog boxes which allow entry of measurements, there is a "Default Simulation/Data or Equations" combo box. Any measurement can override this default. The format to override the network is:

simulation.design.operator[measurement] where simulation is the name of the Simulation/Data from the Workspace Window, design is the name of the design to use, and operator[measurement] are as described in previous sections. An override is most useful for putting parameters from different networks on the same graph.

Additionally, the workspace can be overridden by using the following format:

workspace.simulation.design.operator[measurement] where workspace is the short name of the workspace as given in the Workspace Window. This allows direct comparison of results from different workspaces.

Some examples of overrides are:


204

Meas. Meaning Linear1.Filter.DB[S21] Show the dB magnitude of S21 from the Linear1

simulation of the Filter design EM1.Layout1.S11 Show the dB magnitude of S11 from the EMPOWER

analysis of Layout1 Filter.QL[S21] Shows the loaded Q of the Filter design using the

current simulation. Note that the simulation was not overriden, only the network.

DB[Linear1.FILTER.S21] (wrong)

ILLEGAL. The operator must go around the measurement, not the override.

Equations.X Shows the global equation variable X, which must contain post-processed results.

TUNEBP.Linear1.Filter.DB[S21] Overrides the workspace. Shows the dB magnitude of S21 from the Linear1 simulation of the Filter design from workspace TUNEBP.

Data1.A Show all input admittances from a "Link to data file". Note that in this case, the design name is not required.

Using Equation Results (post-processing)

Anywhere that a measurement is used, post-processed equation variables can be used. The format is:EQUATIONS.variableName

where variableName is a variable from the Global equations for that workspace. For example:

EQUATIONS.X uses variable X from the global equations. A workspace override can also be used with equations:

TUNEBP.EQUATIONS.Y shows variable Y from the global equations of workspace TUNEBP.

Inline equations can also be used anywhere a measurement can be used. Start the measurement with = to indicate an inline equation. For example:

=.MAG[V1] - .MAG[V2] will use the difference of V1 and V2. Notice that, as in the global equations, the periods and the operators (MAG[]) are required for inline equations. This measurement is actually equivalent to the following equations:

USING MeasurementContext TEMP=.MAG[V1] - .MAG[V2]

and then requesting the measurement EQUATIONS.TEMP where MeasurementContext is the Default Simulation/Data specified in the meas. dialog.

Chapter 20: Linear Measurements

S-Parameters

This S-parameter (or scattering parameter) measurements are complex functions of frequency. The frequency range and intervals are as specified in the Linear Simulation dialog box. The s-parameters assume a 50-ohm reference impedance unless otherwise specified. The s-parameters for an n-port network are of the form:

Sij for i, j equal 1, 2, ... n

Details on the S-parameters and their application are found in Section x.x of this Manual.

Values: Complex matrix versus frequency.

Simulations: Linear, EMPOWER

Default Format: Table: dB, angle Graph: dB Smith Chart: dB, angle

Commonly Used Operators:

Operator Description Result Type ANG[S11] Angle in range -180 to 180 degrees Real GD[S22] Group Delay Real QL[S21] Loaded Q Real Other Operators: DB[], MAG[], RECT[], ANG360[], RE[], IM[], MAGANG[], MAGANG360[],DBANG[]

Examples:

Measurement Result in graph, Smith chart, optimization, or yield

Result on table

S22 dB Magnitude of S22 dB Magnitude plus angle of S22 QL[S21] Loaded Q of S21 Loaded Q of S21 MAG[S21] Linear Magnitude of S21 Linear Magnitude of S21 S --- Shows dB Magnitude plus angle of all

S Parameters RECT[S] --- Shows real/imaginary parts of all S

Parameters GD[S21] Group delay of S21 Group delay of S21

Note: For port numbers greater that 9 a comma is used to separate port numbers. For example, on a 12 port device some of the S-Parameters would be specified as follows: S1,11 S12,2 S12,11 S12,2.

Linear Measurements

206

H-Parameters

This H-parameter ( or hybrid parameter) measurements are complex functions of frequency. The frequency range and intervals are as specified in the Linear Simulation dialog box. The H-parameters are only defined for a two port network, and are of the form:

Hij for i, j equal 1, 2

The equations relating the input voltage (V1) and current (I1) to the output voltage (V2) and current (I2) are:

V1 =H11 I1 + H12 V2

I2 = H21 I1 + H22 V2


Simulations: Linear

Default Format: Table: RECT Graph: RE Smith Chart: (none)


Operator Description Result Type RECT[H11] real/imaginary parts Real RE[H22] real part Real MAGANG[H21] Linear magnitude and angle

in range of -180 to 180 Real

Other Operators: MAG[], ANG[], ANG360[], IM[], MAGANG360[]

Examples:

Measurement Result in graph, Smith chart*, optimization, or yield

Result on table

H22 RE[H22] real part of H22 RECT[H] --- Shows real/imaginary parts of all H

Parameters MAG[H21] Linear Magnitude of H21 Linear Magnitude of H21 H --- Shows real/imaginary parts of all H

Parameters * Not available on Smith Chart

Y-Parameters

207

Y-Parameters

This Y-parameter ( or admittance parameter) measurements are complex functions of frequency. The frequency range and intervals are as specified in the Linear Simulation dialog box. The Y-parameters for an n-port network are of the form:

YPij for i, j equal 1, 2, ...n

For a two port network, the equations relating the input voltage (V1) and current (I1) to the output voltage (V2) and current (I2) are:

I1 =YP11 V1 + YP12 V2

I2 = YP21 V1 + YP22 V2


Simulations: Linear



Operator Description Result Type RECT[YP11] real/imaginary parts Real RE[YP22] real part Real MAGANG[YP21] Linear magnitude and angle


Other Operators: MAG[], ANG[], ANG360[], IM[] , MAGANG360[]

Examples:


Result on table

YP22 RE[YP22] real part of YP22 RECT[YP] --- Shows real/imaginary parts of all Y

Parameters MAG[YP21] Linear Magnitude of YP21 Linear Magnitude of YP21 YP --- Shows real/imaginary parts of all Y


Linear Measurements

208

Z-Parameters

This Z-parameter ( or impedance parameter) measurements are complex functions of frequency. The frequency range and intervals are as specified in the Linear Simulation dialog box. The Z-parameters for an n-port network are of the form:

ZPij for i, j equal 1, 2, ...n

For a two port network, the equations relating the input voltage (V1) and current (I1) to the output voltage (V2) and current (I2) are:

V1 =ZP11 I1 + ZP12 I2

V2 = ZP21 I1 + ZP22 I2


Simulations: Linear



Operator Description Result Type RECT[ZP11] real/imaginary parts Real RE[ZP22] real part Real MAGANwG[ZP21] Linear magnitude and angle



Examples:


Result on table

ZP22 RE[ZP22] real part of ZP22 RECT[ZP] --- Shows real/imaginary parts of all Z

Parameters MAG[ZP21] Linear Magnitude of ZP21 Linear Magnitude of ZP21 ZP --- Shows real/imaginary parts of all Z


Voltage Standing Wave Ratio (VSWR)

209

Voltage Standing Wave Ratio (VSWR)

The VSWR measurement is a real function of frequency. The measurements are made looking into the network from the port with other network terminations in place. The frequency range and intervals are as specified in the Linear Simulation dialog box. A port number "i" is used to identify the port:

VSWRi is the Voltage Standing Wave Ratio looking in from port i.

The VSWR is a measure of the energy reflected back to the port. The VSWR1 is related to the s-parameter S11 by:

VSWR1 = [ 1 + |S11| ] / [ 1 - |S11| ]

Therefore, as the reflected energy goes to zero, |S11| , goes to zero and the VSWR approaches unity. As the reflected energy increases, |S11| approaches unity, and VSWR goes to infinity.

Values: Real value versus frequency.

Simulations: Linear

Default Format: Table: RE (Real) Graph: RE (Real) Smith Chart: Sij(plots s-parameters)

Commonly Used Operators: None

Examples:


Result on table

VSWR1 VSWR1 VSWR VSWR --- Show VSWR for all ports * Not available on Smith Chart, plots s-parameters

Linear Measurements

210

Input Impedance / Admittance (ZINi, YINi)

The port impedance and admittance measurements are complex functions of frequency. The measurements are made looking into the network from the port with other network terminations in place. The frequency range and intervals are as specified in the Linear Simulation dialog box. A port number "i" is used to identify the port:

ZINi is the input impedance looking in from port i.

YINi is the input admittance looking in from port i.

Values: Complex value versus frequency.

Simulations: Linear

Default Format: Table: RECT Graph: RE Smith Chart: Sij(plots s-paramters)


Operator Description Result Type RECT[ZIN1] real/imaginary parts Real RE[YIN2] real part Real MAGANG[ZIN3] Linear magnitude and angle



Examples:


Result on table

ZIN2 RE[ZIN2] real part of ZIN2 RECT[ZIN] --- Shows real/imaginary parts for all ports MAG[YIN1] Linear Magnitude of Y21 Linear Magnitude of YIN1 ZIN RE[ZIN1] Shows real/imaginary parts of all ports * Not available on Smith Chart

Voltage Gain

211

Voltage Gain

This voltage gain measurements are complex functions of frequency. The frequency range and intervals are as specified in the Linear Simulation dialog box. The voltage gain, Eij , is the ratio of the output voltage (Vj) to the input voltage (Vi).

Eij = Vj / Vi

Note that due to reflections, the gain Eii may not be unity.


Simulations: Linear

Default Format: Table: DBANG Graph: dB Smith Chart: (none)


Operator Description Result Type DB[E12] gain from port 1 to port 2 Real DBANG[E21] db and angle in range of -

180 to 180 for gain from port 2 to 1

Real

Other Operators: MAG[], ANG[], ANG360[], RE[], IM[] , MAGANG360[]

Examples:


Result on table

E12 DB[E12] DBANG[E12] E --- Shows db/angle for all Eij * Not available on Smith Chart

Linear Measurements

212

Noise Measure (NMEAS)

The "Noise Measure" measurement is a real function of frequency and is available for 2-port networks only.

The noise measure is defined in terms of the noise figure (NF) and maximum available gain (GMAX) as:

NMEAS = [ NF - 1 ] / [ 1 - ( 1 / GMAX) ]

The noise measure represents the noise figure for an infinite number of networks in cascade.


Simulations: Linear

Default Format: Table: MAG[] Graph: MAG[] Smith Chart: (none)


Operator Description Result Type DB[NMEAS] noise measure in dB Real MAG[NMEAS] magnitude of the noise

measure Real

Examples:


Result on table

NMEAS MAG[NF] MAG[NF] DB[NMEAS] magnitude of the minimum noise

measure magnitude of the minimum noise measure

* Not available on Smith Chart

Noise Figure (NF) / Minimum Noise Figure (NFMIN)

213

Noise Figure (NF) / Minimum Noise Figure (NFMIN)

The "Noise Figure" measurements are real functions of frequency and are available for 2-port networks only.

The noise figure is defined as the ratio of input signal-to-noise power ratio (SNRIN) to the output signal-to-noise ratio (SNROUT):

NF = SNRIN / SNROUT

The noise figure is related to the minimum noise figure (NFMIN) by the expression:

NF = NFMIN + RN / GS * | YS - YOPT |2

where

Ys = Gs + j Bs = Source Admittance RN = Normalized Noise Resistance

The minimum noise figure represents the noise figure with ideal match of source impedance (i.e. YS = YOPT )


Simulations: Linear

Default Format: Table: dB Graph: dB Smith Chart: (none)


Operator Description Result Type DB[NF] noise figure in dB Real MAG[NF] magnitude of the noise figure Real

Examples:


Result on table

NF DB[NF] DB[NF] MAG[NFMIN] magnitude of the minimum noise

figure magnitude of the minimum noise figure


Linear Measurements

214

Constant Noise Circles (NCI)

A noise circle is a locus of load impedances for a given noise figure as a function of frequency. This locus is plotted on a Smith chart, with noise figure degradations of 0.25, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 and 6.0 dB from the optimal noise figure.

Note: See the section on S-Parameters for a detailed discussion of noise circles.

Values:Complex values versus frequency.

Simulations: Linear

Default Format: Table: center (MAG[], ANG[]), radius (Linear) Graph: (none) Smith Chart: Circles (6)


Examples:


Result on table

NCI noise circle locus of load impedances for optimal noise figure,

for each circle: center :MAG[], ANG[] radius: Linear

* Available on Smith Chart and Table only.

Noise Correlation Matrix Parameters

215

Noise Correlation Matrix Parameters

The noise correlation matrix elements are complex functions of frequency. The frequency range and intervals are as specified in the Linear Simulation dialog box. For a "n" noise sources, the elements are of the form:

Nij for i, j equal 1, 2

Note: See References [5,6] for a complete discussion of noise correlation matrix properties.


Simulations: Linear



Operator Description Result Type RECT[N11] real/imaginary parts Real RE[N22] real part Real MAGANG[N21] Linear magnitude and angle



Examples:


Result on table

N22 RE[N22] real part of N22 RECT[N] --- Shows real/imaginary parts of all N

Parameters MAG[N21] Linear Magnitude of H21 Linear Magnitude of N21 N --- Shows real/imaginary parts of all N


Linear Measurements

216

Simultaneous Match Gamma at Port i (GMi)

The "Simultaneous Match Gamma" is a complex function of frequency and is available for 2-port networks only. Computes the reflection coefficient that must be seen by the input port i to achieve a simultaneous conjugate match at both the input and output.

Values:Complex value versus frequency.

Simulations: Linear

Default Format: Table: RECT Graph: RE Smith Chart: GMi


Operator Description Result Type RECT[GM1] real/imaginary parts Real RE[GM1] real part Real MAGANG[GM2] Linear magnitude and angle



Examples:


Result on table

GM --- real / imaginary parts of gamma for all ports

GM1 RE[GM1] RECT[GM1]

Simultaneous Match Admittance / Impedance at Port i(ZMi, YMi)

217

Simultaneous Match Admittance / Impedance at Port i(ZMi, YMi)

The "Simultaneous Match Admittance" is a complex function of frequency and is available for 2-port networks only.

This is the value of admittance which must be seen at port i to achieve a simultaneous match at both input and output.


Simulations: Linear

Default Format: Table: RECT Graph: RE Smith Chart: GMi


Operator Description Result Type RECT[YM1] real/imaginary parts Real RE[YM1] real part Real MAGANG[ZM2] Linear magnitude and angle



Examples:


Result on table

YM --- real / imaginary parts of admittance for all ports

ZM1 RE[ZM1] RECT[ZM1]

Linear Measurements

218

Maximum Available Gain (GMAX)

The "Maximum Available Gain" measurement is a real function of frequency and is available for 2-port networks only.

For conditions where the stability factor (K) is greater than zero, i.e. the system is unconditionally stable, then:

GMAX = ( |S21| / |S12| ) * (K - sqrt(K2 - 1)) If K < 1, then GMAX is set to the maximum stable gain, therefore:

GMAX = |S21| / |S12|


Simulations: Linear

Default Format: Table: dB Graph: dB Smith Chart: (none)


Operator Description Result Type DB[GMAX] maximum available gain in

dB Real

MAG[GMAX] magnitude of the maximum available gain

Real

Examples:


Result on table

GMAX DB[GMAX] DB[GMAX] MAG[GMAX] magnitude of the maximum

available gain magnitude of the maximum available gain


Available Gain & Power Gain Circles (GA, GP)

219

Available Gain & Power Gain Circles (GA, GP)

An available gain input network circle is a locus of source impedances for a given gain below the optimum gain. This locus is plotted on a Smith chart, and is only available for 2-port networks. The center of the circle is the point of maximum gain. Circles are displayed for gains of 0, 1, 2, 3, 4, 5, and 6 dB less than the optimal gain. Similarly, the power gain output network circle is a locus of load impedances for a given gain below the optimum gain. If the stability factor K is less than unity, then the 0 dB circle is at GMAX, and the inside of this circle is shaded as an unstable region. The available power gain (Ga) and power gain (Gp) are defined as:

Ga = (available from network) / (power available from source)

Gp = (power deliver to load) / (power input to network)

Note: See the section on S-Parameters for a detailed discussion of Gain Circles.


Simulations: Linear

Default Format: Table: center (MAG[], ANG[]), radius (Linear) Graph: None Smith Chart: Circle


Examples:


Result on table

GA available gain circles center :MAG[], ANG[] radius:Linear GP power gain circles center :MAG[], ANG[] radius:Linear * Available on Smith Chart and Table only.

Linear Measurements

220

Unilateral Gain Circles at Port i (GU1, GU2)

A unilateral gain circle at port 1 is a locus of source impedances for a given transducer power gain below the optimum gain. This locus is plotted on a Smith chart, and is only available for 2-port networks. The center of the circle is the point of maximum gain. Circles are displayed for gains of 0, 1, 2, 3, 4, 5, and 6 dB less than the optimal gain. Similarly, the unilateral gain circle at port 2 is a locus of load impedances for a given transducer power gain below the optimum gain. The transducer power gain (Gt) is defined as:

Gt = (power deliver to load) / (power available from source)

For the "unilateral" transducer gain, S12 is set to zero.

Note: See the section on S-Parameters for a detailed discussion of Gain Circles.


Simulations: Linear

Default Format: Table: center (MAG[], ANG[]), radius (Linear) Graph: (none) Smith Chart: Circles


Examples:


Result on table

GU1 unilateral gain circle at port 1 center :MAG[], ANG[] radius:Linear GU2 unilateral gain circle at port 2 center :MAG[], ANG[] radius:Linear * Available on Smith Chart and Table only.

Stability Factor (K), Stability Measure (B1)

221

Stability Factor (K), Stability Measure (B1)

The "Stability Factor and Measure" parameters are real functions of frequency and are available for 2-port networks only. These parameters aid in determining the stability of the 2-port network. If S12 of a device is not zero, a signal path will exist from the output to the input. This feedback path creates an opportunity for oscillation. The stability factor, K, is:

K = ( 1 - |S11|2 - |S22|2 + |D|2 ) / (2 |S12| |S21|) where D = S11S22 - S12S21

From a practical standpoint when K>1, S11<1, and S22<1, the two-port is unconditionally stable. These are often stated as sufficient to insure stability. Theoretically, K>1 by itself is insufficient to insure stability, and an additional condition should be satisfied. One such parameter is the stability measure,B1, which should be greater than zero.

B1 = |S11|2 - |S22|2 - |D|2 > 0

Note: See the section on S-Parameters for a detailed discussion of stability analysis.


Simulations: Linear

Default Format: Table: Linear Graph: Linear Smith Chart: (none)


Examples:


Result on table

K stability factor stability factor B1 stability measure stability measure * Not available on Smith Chart

Linear Measurements

222

Input / Output Plane Stability Circles (SB1, SB2)

A output stability circle is a locus of load impedances for which the input reflection coefficient (S11) is unity. This locus is plotted on a Smith chart, and is only available for 2-port networks. This locus is a circle with radius Rout about a point Cout, where:

Rout = | S12S21 / (|S22|2 - |D|2) | Cout = (S22 - DS11) / (|S22|2 - |D|2)

The region inside or outside the circle may be the stable region. The filled areas of the graphs are the unstable regions. The input plane stability circle equations are the same as the output plane equations, with 1 and 2 in the subscripts interchanged.

Note: See the section on S-Parameters for a detailed discussion of stability analysis.


Simulations: Linear

Default Format: Table: center (MAG[], ANG[]), radius (Linear) Graph: (none) Smith Chart: Circle


Examples:


Result on table

SB1 input stability circle center :MAG[], ANG[] radius:Linear "par"**

SB2 output stability circle center :MAG[], ANG[] radius:Linear "par"**

* Available on Smith Chart and Table only.

** Parameter indicating the unstable region.

Optimal Gamma for Noise (GOPT)

223

Optimal Gamma for Noise (GOPT)

The "Optimal Gamma for Noise" is a real function of frequency and is available for 2-port networks only.

The optimal gamma is defined in terms of the reference admittance (Yo) and the optimal value of admittance (YOPT) as:

GOPT = [ Yo - YOPT ] / [ Yo + YOPT ]

Notice that gamma goes to zero if the reference admittance is optimal.


Simulations: Linear

Default Format: Table: Linear Graph: Linear Smith Chart: GOPT

Commonly Used Operators: none

Examples:


Result on table

GOPT gamma coefficient gamma coefficient

Linear Measurements

224

Optimal Admittance / Impedance for Noise (YOPT, ZOPT)

The "Optimal Admittance for Noise" is a complex function of frequency and is available for 2-port networks only.

The optimal admittance is the value of the input admittance which minimized the noise figure of the network. The optimal admittance is defined in terms of the source admittance (YS) and the noise resistance (RN) and the noise figures (NF, NFMIN) as:

NF = NFMIN + RN / Re[YS] | YS - YOPT |

The optimal impedance is the inverse of the optimal admittance, i.e. ZOPT = 1 / YOPT


Simulations: Linear

Default Format: Table: RECT Graph: RE Smith Chart: GOPT


Operator Description Result Type RECT[YOPT] real/imaginary parts Real RE[YOPT] real part Real MAGANG[YOPT] Linear magnitude and angle



Examples:


Result on table

YOPT real part of optimal admittance real / imaginary parts of admittance

Effective Noise Input Temperature (NFT)

225

Effective Noise Input Temperature (NFT)

The "Effective Noise Input Temperature" is a real function of frequency and is available for 2-port networks only.

The effective noise temperature is defined in terms of the noise figure (NF) and a standard temperature (To) in degrees Kelvin as:

NFT = To * [ NF - 1 ] where To = 300 degrees Kelvin


Simulations: Linear



Examples:


Result on table

NFT noise temperature in degrees Kelvin

noise temperature in degrees Kelvin


Linear Measurements

226

Normalized Noise Resistance (RN)

The "Normalized Noise Resistance" measurement is a real function of frequency and is available for 2-port networks only.

The noise resistance is normalized with respect to the input impedance of the network (Zo). See the definition of Nosie Figure (NF) for a discussion of RN.


Simulations: Linear



Examples:


Result on table

RN noise resistance noise resistance * Not available on Smith Chart

Reference Impedance (ZPORTi)

227


The reference impedance measurements are complex functions of frequency. The measurements are associated with the network terminations. The frequency range and intervals are as specified in the Linear Simulation dialog box. A port number "i" is used to identify the port:

ZPORTi is the reference impedance for port i.


Simulations: Linear



Operator Description Result Type RECT[ZPORT1] real/imaginary parts Real RE[ZPORT2] real part Real MAGANG[ZPORT3] Linear magnitude and angle



Examples:


Result on table

ZPORT2 RE[ZPORT2] RECT [ZPORT2] RECT[ZPORT] - - - Shows real/imaginary parts for all

ports MAG[ZPORT1] Linear Magnitude of ZPORT2 Linear Magnitude of ZPORT1 ZPORT - - - Shows real/imaginary parts of all ports


Chapter 21: Nonlinear Measurements

Port Power (Pport)

This power measurement is the RMS power delivered at the port. The port is identified by a port designator number.

Values: Real value in specified units.

Simulations: Nonlinear (dc analysis).

Default Format: Table: DBM Graph: DBM Smith Chart: (none)


Operator Description Result Type DBM[P1] RMS power at port 1 Real Other Operators: DB[], MAG[], ANG[], ANG360[], RE[], IM[]

Examples:


Result on table

P1 DBM[P1] = RMS power delivered to port 1

DBM[P1]



230

Probe Current (Iprobe)

This current measurement is the peak current through the specified current probe. The probe is identified by a probe designator name.



Default Format: Table: MAG Graph: MAG Smith Chart: (none)


Operator Description Result Type MAG[I1] linear magnitude of voltage

at probe 1 Real

Other Operators: DB[], ANG[], ANG360[], RE[], IM[]

Examples:


Result on table

ICP1 MAG[ICP1] = current through current probe 1

MAG[ICP1]


Node Voltage (Vnode)

231

Node Voltage (Vnode)

This voltage measurement is the peak voltage at the specified node. The node is the node number or the name of the node as specified by the voltage test point designator name.



Default Format: Table: MAG Graph: MAG Smith Chart: (none)


Operator Description Result Type MAG[V1] linear magnitude of voltage

at node 1 Real

Other Operators: DB[], DBM[], ANG[], ANG360[], RE[], IM[]

Examples:


Result on table

VTP2 MAG[VTP2] = voltage at test point TP2

MAG[VTP2]



232


The reference impedance measurements are complex functions of frequency. The measurements are associated with the network terminations. The frequency range and intervals are as specified in the Linear Simulation dialog box. This measurement is the same as the linear measurement of the same name. A port number "i" is used to identify the port:

ZPORTi is the reference impedance for port i.


Simulations: Linear

Default Format: Table: RECT Graph: RE Smith Chart: (None)


Operator Description Result Type RECT[ZPORT1] real/imaginary parts Real RE[ZPORT2] real part Real MAGANG[ZPORT3] Linear magnitude and angle



Examples:


Result on table

ZPORT2 RE[ZPORT2] RECT [ZPORT2] RECT[ZPORT] - - - Shows real/imaginary parts for all

ports MAG[ZPORT1] Linear Magnitude of ZPORT2 Linear Magnitude of ZPORT1 ZPORT - - - Shows real/imaginary parts of all ports * Not available on Smith Chart

Chapter 22: SPECTRASYS Measurements

Adjacent Channel Power (ACP[U or L][n])

This measurement is the integrated power of the specified adjacent channel. All adjacent channels are relative to the main channel frequency (CF). Consequently, channels exist above and below the main reference channel frequency. The user can specify which side of the main or reference channel that the adjacent channel is located on and also the channel number. The channel number is relative to the main or reference channel. Therefore, channel 1 would be the first adjacent channel, channel 2 would be the second adjacent channel, and so on.

U - Upper Side L - Lower Side n - Channel Number (any integer > 0)

For example, ACPL2 is the power of the second adjacent channel below that specified by the channel frequency (CF). If CF was 100 MHz and the channel bandwidth was 1 MHz then the main channel would be 99.5 to 100.5 MHz. Consequently, then ACPL2 would then be the integrated channel power between 97.5 and 98.5 MHz and ACPL1 would be the integrated channel power between 98.5 and 99.5 MHz.

NOTE: Only the first 2 adjacent channels on either side of the reference channel are listed in the 'Measurement Wizard". However, there is no restriction on the Adjacent Channel Number other than it must be non-negative and greater than or equal to 1.

Values: Real value in Watts.

Simulations: SPECTRASYS



Operator Description Result Type

DBM[ACPU2] 2nd upper adjacent channel power in dBm Real MAG[ACPU2] magnitude of the 2nd upper adjacent channel power in Watts Real Examples:


Result on table

DBM[ACPU2] DBM[ACPU2] DBM[ACPU2] MAG[ACPU2] MAG[ACPU2] MAG[ACPU2] * Not available on Smith Chart

SPECTRASYS Measurements

234

Adjacent Channel Frequency (ACF[U or L][n])

This measurement is the frequency of the specified adjacent channel. All adjacent channel frequencies are relative to the main 'Channel Frequency (CF)'. Consequently, channels exist above and below the main reference channel frequency. The user can specify which side of the main or reference channel that the adjacent channel is located on and also the channel number. The channel number is relative to the main or reference channel. Therefore, channel 1 would be the first adjacent channel, channel 2 would be the second adjacent channel, and so on.

U - Upper Side

L - Lower Side

n - Channel Number (any integer > 0)

For example, ACFU1 if the first adjacent channel above that specified by the channel frequency (CF). If CF was 100 MHz and the channel bandwidth was 1 MHz then the main channel would be 99.5 to 100.5 MHz. Consequently, then ACFU1 would then be the channel 100.5 to 101.5 MHz and ACFL1 would be 98.5 to 99.5 MHz.

NOTE: Only the first 2 adjacent channels on either side of the reference channel is listed in the 'Measurement Wizard". However, there is no restriction on the Adjacent Channel Number.

Values: Real value in MHz.




Examples:


Result on table

ACFL1 ACFL1 ACFL1 * Not available on Smith Chart

Added Noise (AN)

235

Added Noise (AN)

This measurement is the noise contribution of each individual stage along the specified path as shown by:

AN[n] = [CNF[n] - CNF[n-1]] (dB), where AN[0] = 0 dB, n = stage number

This measurement is simply the difference in the cascaded noise figure between the current node and the previous node. This measurement is very useful and will help the user identify the contribution to the noise figure by each stage along the path.

Values: Real value (numeric).





DB[AN] stage noise figure in dB Real MAG[AN] numeric value of the stage noise figure Real

Examples:


Result on table

DB[AN] DB[AN] DB[AN] MAG[AN] MAG[AN] MAG[AN] * Not available on Smith Chart


236

Cascaded Gain (CGAIN)

This measurement is the cascaded gain along the specified path. The 'Cascaded Gain' is the difference between the input 'Desired Channel Power' and the 'Desired Channel Power' at the nth stage as shown by:

CGAIN[n] = DCP[n] - DCP[0] (dB), where n = stage number

The 'Channel' is defined by the 'Channel Frequency' for the selected path and the system analysis 'Channel Measurement Bandwidth'. This measurement is not influenced by other signal sources that were created along another path since it is only based on the 'Desired Channel Power'.






DB[CGAIN] cascaded gain in dB Real MAG[CGAIN] numeric value of the cascaded gain Real

Examples:


Result on table

DB[CGAIN] DB[CGAIN] DB[CGAIN] MAG[CGAIN] MAG[CGAIN] MAG[CGAIN] * Not available on Smith Chart

Cascaded Third Order Intermod Gain (CGAINIM3)

237

Cascaded Third Order Intermod Gain (CGAINIM3)

This measurement is the cascaded gain of the third order intermods along the specified path. The 'Cascaded Third Order Intermod Gain' is the difference between the input 'Desired Third Order Intermod Channel Power' and the 'Desired Third Order Intermod Channel Power' at the nth stage as shown by:

CGAINIM3[n] = DCPIM3[n] - DCPIM3[0] (dB), where n = stage number

The 'Channel' is defined by the 'Channel Frequency' for the selected path and the system analysis 'Channel Measurement Bandwidth'. This measurement is not influenced by other signal sources that were created along another path since it is only based on the 'Desired Third Order Intermod Channel Power'.

NOTE: This measurement is used by the IIP3, OIP3, and SFDR measurements.






DB[CGAINIM3] cascaded third order intermod gain in dB Real MAG[CGAINIM3] numeric value of the cascaded third order intermod gain Real

Examples:


Result on table

DB[CGAINIM3] DB[CGAINIM3] DB[CGAINIM3] MAG[CGAINIM3] MAG[CGAINIM3] MAG[CGAINIM3] * Not available on Smith Chart


238

Conducted Third Order Intermod Power (CIM3P)

This measurement is the integrated total intermod power conducted from the prior stage. All Intermod only power is integrated across the defined channel for the specified path. This measurement will include intermod power from all paths and all sources at the prior node if those intermods fall within the channel. In equation form the conducted third order intermod power is:

CIM3P[n] = TIM3P[n-1] + GAIN[n], where CIM3P[0] = 0 dB and n = stage number

Using this measurement in conjunction with the 'Generated Third Order Intermod Power (GIM3P)' and the 'Total Third Order Intermod Power (TIM3P)' the user can quickly identify the weak intermod link in the cascaded chain and will guide the user in maximizing the Spurious Free Dynamic Range (SFDR).

NOTE: Two modes of intermod calculation exist: 1) Automatic 2 Tone and 2) Manual. In both of these cases the 'Channel' is assumed to contain intermod power and not the intermod tones themselves. Consequently, for the 'Automatic 2 Tone' case two tones are actually created internally by SPECTRAYS and feed into the system at the specified 'Tone Offset'. The first tone appears at one 'Tone Offset' from the 'Channel' and the second appears at two 'Tone Offset' from the 'Channel'. Both tones will start out with the power specified by the 'Two Tone Power Level'. For the 'Manual' case the user must manually create the tones, however, for this case there is no restriction on the number of tones that can be used to create the intermod spectrum. Only the intermods that fall within the defined 'Channel' will be reported by this measurement.






DBM[CIM3P] conducted third order intermod power in dBm Real MAG[CIM3P] magnitude of the conducted third order intermod power in

Watts Real

Examples:


Result on table

DBM[CIM3P] DBM[CIM3P] DBM[CIM3P] MAG[CIM3P] MAG[CIM3P] MAG[CIM3P] * Not available on Smith Chart

Carrier to Noise Ratio (CNR)

239

Carrier to Noise Ratio (CNR)

This measurement is the ratio of the 'Channel Power' (carrier) to 'Channel Noise Power' along the specified path as shown by:

CNR[n] = CP[n] - CNP[n] (dB), where n = stage number

Both the 'Channel Power' and the 'Channel Noise Power' are measured in the same 'Channel Measurement Bandwidth' which is specified on the 'System Simulation' dialog box.






DB[CNR] carrier to noise ratio in dB Real MAG[CNR] numeric value of the carrier to noise ratio Real

Examples:


Result on table

DB[CNR] DB[CNR] DB[CNR] MAG[CNR] MAG[CNR] MAG[CNR] * Not available on Smith Chart


240

Cascaded Noise Figure (CNF)

This measurement is the cascaded noise figure along the specified path. The 'Cascaded Noise Figure' is the 'Channel Noise Power' at the output of stage n minus the sum of the input 'Channel Noise Power' and the 'Cascaded Gain' at stage n as shown by:

CNF[n] = CNP[n] - (CNP[0] - CGAIN[n]) (dB), where n = stage number

The 'Noise Channel' is defined by the 'Channel Frequency' for the selected path and the system analysis 'Channel Measurement Bandwidth'.






DB[CNF] cascaded noise figure in dB Real MAG[CNF] numeric value of the cascaded noise figure Real

Examples:


Result on table

DB[CNF] DB[CNF] DB[CNF] MAG[CNF] MAG[CNF] MAG[CNF] * Not available on Smith Chart

Channel (or Path) Frequency (CF)

241

Channel (or Path) Frequency (CF)

Since each spectrum can contain a large number of spectral components and frequencies SPECTRASYS must be able to determine the area of the spectrum to integrate for various measurements. This integration area is defined by a ‘Channel Frequency’ and a ‘Measurement Bandwidth’. SPECTRASYS can automatically identify the desired ‘Channel Frequency’ in an unambiguous case where only one frequency is on the ‘from node’ of the designated path. An error will appear if more than one frequency is available. For this particular case the user must specify the intended frequency for this path in the 'System Simulation Dialog Box'.

A unique ‘Channel Frequency’ exists for each node along the specified path. Consequently, each node along the path will have the same ‘Channel Frequency’ until a frequency translation element such as a mixer is encountered. SPECTRASYS automatically deals with frequency translation through a mixer. The individual mixer parameters of ‘Desired Output (Sum or Difference)’ and ‘LO Injection (High of Low)’ are used to determine the desired frequency at the output of the mixer. A mixer is the only device that causes a frequency translation of the channel frequency. The ‘Channel Frequency’ is a critical parameter for SPECTRASYS since most of the measurements are based on this parameter. If this frequency is incorrectly specified then the user may get unexpected results since many measurements are based on this frequency. The easiest way to verify the ‘Channel Frequency’ that SPECTRASYS is using is to look at this measurement in a Table or a Rectangular Graph.





Examples:


Result on table

CF CF CF * Not available on Smith Chart


242

Channel Noise Power (CNP)

This measurement is the integrated noise power of the specified channel (identified by the 'Channel Frequency' (CF) and the 'Channel Measurement Bandwidth'). Each path has a unique channel frequency and SPECTRASYS can determine it in the unambiguous case where only one signal source is present on the initial node of the path. However, in the case of multiple signal source SPECTRASYS must be told what the 'Channel Frequency' is. Both the 'Channel Frequency' and the 'Channel Measurement Bandwidth' are specified on the 'Settings' page of the 'System Simulation Dialog Box'.

For example, if the 'Channel Measurement Bandwidth' was specified to .1 MHz and the 'Channel Frequency' was 2000 MHz then the CNP is the integrated noise power from 1999.95 to 2000.05 MHz.






DBM[CNP] channel noise power in dBm Real MAG[CNP] magnitude of the channel noise power in Watts Real

Examples:


Result on table

DBM[CNP] DBM[CNP] DBM[CNP] MAG[CNP] MAG[CNP] MAG[CNP] * Not available on Smith Chart

Channel Power (CP)

243

Channel Power (CP)

This measurement is the integrated power of the specified channel (identified by the 'Channel Frequency' (CF) and the 'Channel Measurement Bandwidth'). Each path has a unique channel frequency and SPECTRASYS can determine it in the unambiguous case where only one signal source is present on the initial node of the path. However, in the case of multiple signal source SPECTRASYS must be told what the 'Channel Frequency' is. Both the 'Channel Frequency' and the 'Channel Measurement Bandwidth' are specified on the 'Settings' page of the 'System Simulation Dialog Box'.

For example, if the 'Channel Measurement Bandwidth' was specified to .03 MHz and the 'Channel Frequency' was 220 MHz then the CP is the integrated power from 219.985 to 220.015 MHz.






DBM[CP] channel power in dBm Real MAG[CP] magnitude of the channel power in Watts Real

Examples:


Result on table

DBM[CP] DBM[CP] DBM[CP] MAG[CP] MAG[CP] MAG[CP] * Not available on Smith Chart


244

Desired Channel Power (DCP)

This measurement is the integrated power of the specified channel (identified by the 'Channel Frequency' (CF) and the 'Channel Measurement Bandwidth') traveling in the desired direction (path direction). Each path has a unique channel frequency and SPECTRASYS can determine it in the unambiguous case where only one signal source is present on the initial node of the path. However, in the case of multiple signal source SPECTRASYS must be told what the 'Channel Frequency' is. Both the 'Channel Frequency' and the 'Channel Measurement Bandwidth' are specified on the 'Settings' page of the 'System Simulation Dialog Box'. This measurement is not influenced by other signal sources that were created along another path even at the same frequency since the measurement path specifies the direction of interest.

For example, if the 'Channel Measurement Bandwidth' was specified to .03 MHz and the 'Channel Frequency' was 220 MHz then the DCP is the integrated power from 219.985 to 220.015 MHz. This power measurement will not even be affect by another 220 MHz signal traveling in the reverse direction even if it is much larger in amplitude.






DBM[DCP] desired channel power in dBm Real MAG[DCP] magnitude of the desired channel power in Watts Real

Examples:


Result on table

DBM[DCP] DBM[DCP] DBM[DCP] MAG[DCP] MAG[DCP] MAG[DCP] * Not available on Smith Chart

Desired Third Order Intermod Channel Power (DCPIM3)

245

Desired Third Order Intermod Channel Power (DCPIM3)

This measurement is the integrated third order intermod power of the specified channel (identified by the 'Channel Frequency' (CF) and the 'Channel Measurement Bandwidth') traveling in the desired direction (path direction). Each path has a unique channel frequency and SPECTRASYS can determine it in the unambiguous case where only one signal source is present on the initial node of the path. However, in the case of multiple signal source SPECTRASYS must be told what the 'Channel Frequency' is. Both the 'Channel Frequency' and the 'Channel Measurement Bandwidth' are specified on the 'Settings' page of the 'System Simulation Dialog Box'. This measurement is not influenced by other signal sources that were created along another path even at the same frequency since the measurement path specifies the direction of interest.

NOTE: This measurement is used by the 'Third Order Intermod Gain (GAINIM3)' and the 'Cascaded Third Order Intermod Gain (CGAINIM3)'.






DBM[DCPIM3] desired third order intermod channel power in dBm Real MAG[DCPIM3] magnitude of the desired third order intermod channel power

in Watts Real

Examples:


Result on table

DBM[DCPIM3] DBM[DCPIM3] DBM[DCPIM3] MAG[DCPIM3] MAG[DCPIM3] MAG[DCPIM3] * Not available on Smith Chart


246

Gain (GAIN)

This measurement is the individual stage gain along the specified path. The 'Gain' is the difference between the input 'Desired Channel Power' of the stage and the output 'Desired Channel Power' as shown by:

GAIN[n] = DCP[n] - DCP[n-1] (dB), where GAIN[0] = 0 dB, n = stage number

The 'Channel' is defined by the 'Channel Frequency' for the selected path and the system analysis 'Channel Measurement Bandwidth'. This measurement is not influenced by other signal sources that were created along another path since it is only based on the 'Desired Channel Power'.






DB[GAIN] gain in dB Real MAG[GAIN] numeric value of the gain Real

Examples:


Result on table

DB[GAIN] DB[GAIN] DB[GAIN] MAG[GAIN] MAG[GAIN] MAG[GAIN] * Not available on Smith Chart

Generated Third Order Intermod Power (GIM3P)

247

Generated Third Order Intermod Power (GIM3P)

This measurement is the generated intermod power created at the current stage. All Intermod only power is integrated across the defined channel for the specified path. In equation form the generated third order intermod power is:

GIM3P[n] = integration of the spectrum generated by intermods at stage n across the channel

Using this measurement in conjunction with the 'Conducted Third Order Intermod Power (CIM3P)' and the 'Total Third Order Intermod Power (TIM3P)' the user can quickly identify the weak intermod link in the cascaded chain and will guide the user in maximizing the Spurious Free Dynamic Range (SFDR).







DBM[GIM3P] generated third order intermod power in dBm Real MAG[GIM3P] magnitude of the generated third order intermod power in

Watts Real

Examples:


Result on table

DBM[GIM3P] DBM[GIM3P] DBM[GIM3P] MAG[GIM3P] MAG[GIM3P] MAG[GIM3P] * Not available on Smith Chart


248

Image Frequency (IMGF)

This measurement is the image frequency from the input to the first mixer. Any energy at the image frequency can seriously degrade the performance of a receiver. Even unfiltered noise at the image frequency will be converted into the IF band and degrade the sensitivity by as much as 3 dB. The image frequency measurements are provided to help the designer understand the impact of the image frequency on the performance of the receiver.

Since SPECTRASYS knows the 'Channel Frequency' of the specified path it also has the ability to figure out what the image frequency is up to the 1st mixer. This measurement will show what that frequency is. This image frequency is used to determine the area of the spectrum that will be integrated by the 'Mixer Image Channel Power' measurement to calculate the image power.

For example if we designed a 2 GHz receiver that had an IF frequency of 150 MHz using low LO side injection then the LO frequency would be 1850 MHz and image frequency for all stages from the input to the first mixer would be 1700 MHz. All noise and interference must be rejected at this frequency to maintain the sensitivity and performance of the receiver. Values: Real value in MHz.




Examples:


Result on table

IMGF IMGF IMGF * Not available on Smith Chart

Input Third Order Intercept (IIP3)

249

Input Third Order Intercept (IIP3)

This measurement is the third order intercept point referenced to the input along the specified path as shown by:

IIP3[n] = OIP3[n] - CGAINIM3[n] (dBm), where n = stage number

This measurement simple takes the computed 'Output Third Order Intercept' and references it to the input by subtracting the cascaded gain of the intermod path from the input to the current stage. The last IIP3 value for a cascaded chain will always be the actual input third order intercept for the entire chain.

In order to make this measurement three tones (signals) must actually be present at the input port, 1) channel frequency tone (desired main or primary channel), 2) first interfering tone, and 3) second interfering tone. Furthermore, the spacing of the two interfering tones needs to be such that intermods will actually fall into the main or primary channel. If these conditions are not met then no intermod power will be measured in the main channel.






Operator Description Result Type DBM[IIP3] input third order intercept in dBm Real MAG[IIP3] magnitude of the input third order intercept in Watts Real Examples:


Result on table

DBM[IIP3] DBM[IIP3] DBM[IIP3] MAG[IIP3] MAG[IIP3] MAG[IIP3] * Not available on Smith Chart


250

Mixer Image Channel Power (IMGP)

This measurement is the integrated power of the image channel from the input to the first mixer. Any energy at the image frequency can seriously degrade the performance of a receiver. Even unfiltered noise at the image frequency will be converted into the IF band and degrade the sensitivity by as much as 3 dB. The image frequency measurements are provided to help the designer understand the impact of the image frequency on the performance of the receiver.

Since SPECTRASYS knows the 'Channel Frequency' of the specified path it also has the ability to figure out what the image frequency is up to the 1st mixer. The 'Mixer Image Frequency' measurement will show what that frequency is. This image frequency is used to determine the area of the spectrum that will be integrated by the this measurement to calculate the image power. The 'Channel Measurement Bandwidth' located in the 'System Simulation Dialog Box' is used as the bandwidth for the this measurement.

For example if we designed a 2 GHz receiver that had an IF frequency of 150 MHz using low LO side injection then the LO frequency would be 1850 MHz and image frequency for all stages from the input to the first mixer would be 1700 MHz. If the receiver bandwidth was 5 MHz then the image channel would be from 1697.5 to 1702.5 MHz. All noise and interference must be rejected in this channel to maintain the sensitivity and performance of the receiver. Values: Real value in Watts.





DBM[IMGP] mixer image channel power in dBm Real MAG[IMGP] magnitude of the mixer image channel power in Watts Real

Examples:


Result on table

DBM[IMGP] DBM[IMGP] DBM[IMGP] MAG[IMGP] MAG[IMGP] MAG[IMGP] * Not available on Smith Chart

Mixer Image Rejection Ratio (IMGR)

251

Mixer Image Rejection Ratio (IMGR)

This measurement is the ratio of the 'Channel Power' to 'Mixer Image Channel Power (IMGP)' along the specified path as shown by:

IMGR[n] = CP[n] - IMGP[n] (dB), where n = stage number

For this particular measurement basically two channels exist both with the same 'Channel Measurement Bandwidth' 1) received or main channel and 2) 1st mixer image channel. The only difference is between these two channels are their frequencies, one is at the 'Channel Frequency (CF)' and the other is at the 'Mixer Image Frequency (IMGF)'.






DB[IMGR] mixer image rejection ratio in dB Real MAG[IMGR] numeric value of the mixer image rejection ratio Real

Examples:


Result on table

DB[IMGR] DB[IMGR] DB[IMGR] MAG[IMGR] MAG[IMGR] MAG[IMGR] * Not available on Smith Chart


252

Offset Channel Frequency (OCF)

The 'Offset Channel Frequency' and 'Offset Channel Power' are very useful measurements in SPECTRASYS. These measurements give the user the ability to create a user defined channel relative the the main channel. The user specifies both the 'Offset Frequency' (relative to the 'Channel Frequency (CF)') and the 'Offset Channel Bandwidth'. As with the 'Channel Frequency' measurement SPECTRASYS automatically deals with the frequency translations of the 'Offset Channel Frequency' through mixers. Both the 'Offset Frequency' and the 'Offset Channel Bandwidth' can be tuned by simply placing a question mark in front of the value to be tuned. This measurement simply returns the 'Offset Channel Frequency' for every node along the specified path. Values: Real value in MHz.




Examples:


Result on table

OCF OCF OCF * Not available on Smith Chart

Offset Channel Power (OCP)

253

Offset Channel Power (OCP)

The 'Offset Channel Frequency' and 'Offset Channel Power' are very useful measurements in SPECTRASYS. These measurements give the user the ability to create a user defined channel relative the the main channel. The user specifies both the 'Offset Frequency' (relative to the 'Channel Frequency (CF)') and the 'Offset Channel Bandwidth'. As with the 'Channel Frequency' measurement SPECTRASYS automatically deals with the frequency translations of the 'Offset Channel Frequency' through mixers. Both the 'Offset Frequency' and the 'Offset Channel Bandwidth' can be tuned by simply placing a question mark in front of the value to be tuned. This measurement returns the integrated 'Offset Channel Power' for every node along the specified path.

For example, if the 'Channel Frequency' was 2140 MHz, 'Offset Channel Frequency' was 10 MHz, and the 'Offset Channel Bandwidth" was 1 MHz then the OCP is the integrated power from 2149.5 to 2150.5 MHz.






DBM[OCP] offset channel power in dBm Real MAG[OCP] magnitude of the offset channel power in Watts Real

Examples:


Result on table

DBM[OCP] DBM[OCP] DBM[OCP] MAG[OCP] MAG[OCP] MAG[OCP] * Not available on Smith Chart


254

Output Third Order Intercept (OIP3)

This measurement is the third order intercept point referenced to the output along the specified path as shown by:

OIP3[n] = Virtual Tone Power[n] - Delta[n] / 2 (dBm), where n = stage number

Virtual Tone Power[n] = TCP[0] + CGAINIM3[n]

Delta[n] = Virtual Tone Power[n] - TIM3P[n]

Delta is the difference in dB between the 'Total Third Order Intermod Power (TIM3P)' in the channel and the first adjacent signal (tone) that created it for the current stage. This first adjacent signal (tone) channel is specified by the 'Tone Offset' and the 'Channel Measurement Bandwidth' in the 'System Simulation Dialog Box'. The channel where the intemod power is integrated is designated by the 'Channel Frequency (CF)' and the 'Channel Measurement Bandwidth' for the specified path. Since the signals (tones) may pass through filters and may be attenuated through the path a 'Virtual Tone Power' must be created where its power level is the un-attenuated power level. This power level is simply the 'Tone Channel Power (TCP)' at the input plus the 'Cascaded Third Order Intermod Gain (CGAINIM3)' at the current stage.

In order to make this measurement three tones (signals) must actually be present at the input port, 1) channel frequency tone (desired main or primary channel), 2) first interfering tone, and 3) second interfering tone. Furthermore, the spacing of the two interfering tones needs to be such that intermods will actually fall into the main or primary channel. If these conditions are not met then no intermod power will be measured in the main channel.





Output Third Order Intercept (OIP3)

255



DBM[OIP3] output third order intercept in dBm Real MAG[OIP3] magnitude of the output third order intercept in Watts Real

Examples:


Result on table

DBM[OIP3] DBM[OIP3] DBM[OIP3] MAG[OIP3] MAG[OIP3] MAG[OIP3] * Not available on Smith Chart


256

Spurious Free Dynamic Range (SFDR)

This measurement is the spurious free dynamic range along the specified path as shown by:

SFDR[n] = 2/3 [IIP3[n] - CNP[n]] (dB), where n = stage number

The 'Spurious Free Dyanmic Range' is the range between the Minimum Detectable (Discernable) Signal (MDS) and the input power which would cause the third order intermods to be equal to the MDS. The MDS is the smallest signal that can be detected and will be equivalent to the receiver noise floor with a signal to noise ratio of 0 dB. In other words the MDS = -174 dBm/Hz + System Noise Figure + 10 Log(Channel Bandwidth).






DB[SFDR] spurious free dynamic range in dB Real MAG[SFDR] magnitude of the spurious free dynamic range in Watts Real

Examples:


Result on table

DB[SFDR] DB[SFDR] DB[SFDR] MAG[SFDR] MAG[SFDR] MAG[SFDR] * Not available on Smith Chart

Stage Dynamic Range (SDR)

257

Stage Dynamic Range (SDR)

This measurement is the dynamic range of the stage along the specified path as shown by:

SDR[n] = SOP1DB[n] - CP[n] (dB), where n = stage number

This simple measurement shows the difference between the 1 dB compression point of the stage and current output 'Channel Power'. This measurement is extremely useful when trying to optimize each stage dynamic range and determine which stage that will go into compression first.






DB[SDR] stage dynamic range in dB Real MAG[SDR] numeric value of the stage dynamic range Real

Examples:


Result on table

DB[SDR] DB[SDR] DB[SDR] MAG[SDR] MAG[SDR] MAG[SDR] * Not available on Smith Chart


258

Stage Noise Figure (SNF)

This measurement is the noise figure of each individual stage along the specified path as shown by:

SNF[n] = [CNP[n] - CNP[n-1]] - GAIN[n] (dB), where n = stage number (Passive Stages)

OR

SNF[n] = Noise Figure of the Active Stage (dB), where n = stage number (Amplifier and Mixer Stages)

The 'Stage Noise Figure' is the noise figure of each individual stage. For all passive devices this noise figure is based on the channel power and stage gain. However, for amplifier and mixer stages this noise figure will be the noise figure entered in the parameters for these devices. This measurement is used to aid the user in determining the added noise by each stage in the cascade.






DB[SNF] stage noise figure in dB Real MAG[SNF] numeric value of the stage noise figure Real

Examples:


Result on table

DB[SNF] DB[SNF] DB[SNF] MAG[SNF] MAG[SNF] MAG[SNF] * Not available on Smith Chart

Stage Output 1 dB Compression Point (SOP1DB)

259

Stage Output 1 dB Compression Point (SOP1DB)

This measurement is the output 1 dB compression point specified in the element parameters for the particular stage. This parameter is currently only available for the SPECTRASYS non-linear behavioral models such as amplifiers and mixers. For all stages where this parameter is not specified a large default value of +100 dBm is used.






DBM[SOP1DB] stage output 1 dB compression point in dBm Real MAG[SOP1DB] numeric value of the stage output 1 dB compression point Real

Examples:


Result on table

DBM[SOP1DB] DBM[SOP1DB] DBM[SOP1DB] MAG[SOP1DB] MAG[SOP1DB] MAG[SOP1DB] * Not available on Smith Chart


260

Stage Output Third Order Intercept (SOIP3)

This measurement is the output third order intercept specified in the element parameters for the particular stage. This parameter is currently only available for the SPECTRASYS non-linear behavioral models such as amplifiers and mixers. For all stages where this parameter is not specified a large default value of +100 dBm is used.






DBM[SOIP3] stage output third order intercept in dBm Real MAG[SOIP3] numeric value of the stage output third order intercept Real

Examples:


Result on table

DBM[SOIP3] DBM[SOIP3] DBM[SOIP3] MAG[SOIP3] MAG[SOIP3] MAG[SOIP3] * Not available on Smith Chart

Stage Output Saturation Power (SOPSAT)

261

Stage Output Saturation Power (SOPSAT)

This measurement is the output saturation power specified in the element parameters for the particular stage. This parameter is currently only available for the SPECTRASYS non-linear behavioral models such as amplifiers and mixers. For all stages where this parameter is not specified a large default value of +100 dBm is used.






DBM[SOPSAT] stage output saturation power in dBm Real MAG[SOPSAT] numeric value of the stage output saturation power Real

Examples:


Result on table

DBM[SOPSAT] DBM[SOPSAT] DBM[SOPSAT] MAG[SOPSAT] MAG[SOPSAT] MAG[SOPSAT] * Not available on Smith Chart


262

Third Order Intermod Gain (GAINIM3)

This measurement is the individual third order intermod gain along the specified path. The 'Third Order Intermod Gain' is the difference between the input 'Desired Third Order Intermod Channel Power' of the stage and the output 'Desired Third Order Intermod Channel Power' as shown by:

GAINIM3[n] = DCPIM3[n] - DCPIM3[n-1] (dB), where GAINIM3[0] = 0 dB, n = stage number

The 'Channel' is defined by the 'Channel Frequency' for the selected path and the system analysis 'Channel Measurement Bandwidth'. This measurement is not influenced by other signal sources that were created along another path since it is only based on the 'Desired Third Order Intermod Channel Power'.






DB[GAINIM3] third order intermod gain in dB Real MAG[GAINIM3] numeric value of the third order intermod gain Real

Examples:


Result on table

DB[GAINIM3] DB[GAINIM3] DB[GAINIM3] MAG[GAINIM3] MAG[GAINIM3] MAG[GAINIM3] * Not available on Smith Chart

Tone Channel Frequency (TCF)

263

Tone Channel Frequency (TCF)

This measurement is the channel frequency of the tone channel used for intermod measurements such as: IIP3, OIP3, SFDR, etc.. The 'Tone Channel Frequency' is the frequency of the first adjacent tone to the generated intermods. The exact location of this channel is specified as a relative offset to the main or primary 'Channel Frequency (CF)' for the specified path. This primary channel frequency plus the 'Tone Offset' specified in the 'System Simulation Dialog Box' is the 'Tone Channel Frequency'. As with all other frequency measurements SPECTRASYS is able to deal with the frequency translation through all mixers. In order to make some intermod measurement three tones (signals) must actually be present at the input port, 1) channel frequency tone (desired main or primary channel), 2) first interfering tone, and 3) second interfering tone. Furthermore, the spacing of the two interfering tones needs to be such that intermods will actually fall into the main or primary channel. If these conditions are not met then no intermod power will be measured in the main channel.






Examples:


Result on table

TCF TCF TCF * Not available on Smith Chart


264

Tone Channel Power (TCP)

This measurement is the power of the tone channel used for intermod measurements such as: IIP3, OIP3, SFDR, etc.. The 'Tone Channel Frequency' is the frequency of the first adjacent tone to the generated intermods. This frequency plus the 'Channel Measurement Bandwidth' make up the 'Tone Channel'. The exact location of this channel is specified as a relative offset to the main or primary 'Channel Frequency (CF)' for the specified path. This primary channel frequency plus the 'Tone Offset' specified in the 'System Simulation Dialog Box' is the 'Tone Channel Frequency'. As with all other frequency measurements SPECTRASYS is able to deal with the frequency translation through all mixers. In order to make some intermod measurement three tones (signals) must actually be present at the input port, 1) channel frequency tone (desired main or primary channel), 2) first interfering tone, and 3) second interfering tone. Furthermore, the spacing of the two interfering tones needs to be such that intermods will actually fall into the main or primary channel. If these conditions are not met then no intermod power will be measured in the main channel.





Tone Channel Power (TCP)

265



DBM[TCP] tone channel power in dBm Real MAG[TCP] magnitude of the tone channel power in Watts Real

Examples:


Result on table

DBM[TCP] DBM[TCP] DBM[TCP] MAG[TCP] MAG[TCP] MAG[TCP] * Not available on Smith Chart


266

Total Third Order Intermod Power (TIM3P)

This measurement is the integrated total intermod power conducted from the prior stage plus the intermod power generated by the current stage. All Intermod power is integrated across the defined channel for the specified path. This measurement will include intermod power from all paths and all sources at the prior node as well as the current node if those intermods fall within the channel. In equation form the conducted third order intermod power is:

TIM3P[n] = integration of the total intermod spectrum at stage n across the channel

Using this measurement in conjunction with the 'Conducted Third Order Intermod Power (CIM3P)' and the 'Generated Third Order Intermod Power (GIM3P)' the user can quickly identify the weak intermod link in the cascaded chain and will guide the user in maximizing the Spurious Free Dynamic Range (SFDR).







DBM[TIM3P] total third order intermod power in dBm Real MAG[TIM3P] total third order intermod power in Watts Real

Examples:


Result on table

DBM[TIM3P] DBM[TIM3P] DBM[TIM3P] MAG[TIM3P] MAG[TIM3P] MAG[TIM3P] * Not available on Smith Chart

Chapter 23: New System Elements and Behavioral Models

Coupled Antenna (ANTC)

This element is used to provide a secondary RF output path from an antenna. This system symbol is available in SCHEMAX in the System toolbar.

Netlist syntax:

ANTC n1 n2 ISO= Phase= [ZIN=] [ZOUT=] [Name=] Parameters:

ISO Isolation or attenuation of coupled path in dB (nodes 1 to 2).

Phase Phase lag in coupled path in degrees.

ZIN Input impedance in ohms (default is 50 ohms).

ZOUT Output impedance in ohms (default is ZIN). The coupled antenna isolation and phase are assumed to be constant across frequency.

Note: The isolation is an attenuation and must be positive. The phase is a lag and must also be positive. The input and output impedances must be non-zero.

Examples:

ANTC 1 2 ISO=50 Phase=20 Touchstone Translation: None

Default SPICE Translation: None

New System Elements and Behavioral Models

268

RF Attenuator (ATTN)

This element is used to provide attenuation in the RF path. Furthermore, the return loss of the RF attenuator will be double the attenuation. Input and output impedances can be specified by the user. The output impedance defaults to the input impedance unless otherwise specified by the user. This system symbol is available in SCHEMAX in the System toolbar.

Netlist syntax:

ATTN n1 n2 L= [Zin=] [Zout=] [Name=] Parameters:

L Attenuation (or Loss) in dB.

Zin Input Impedance in ohms (default is 50).

Zout Output Impedance in ohms (default is Zin).

Attenuation is assumed to be constant across frequency. Note: As the ratio of Zin to Zout gets very large or very small the input and output impedances will affect the total insertion loss of the attenuator.

Examples:

Dissimilar Impedance Example:

ATTN 1 2 L=3 Zin=50 Zout=75

Complex Output Impedance (50 + j10 ohms) Example:

ATTN 1 2 L=3 Zout=complex(50,10) Touchstone Translation:

None Default SPICE Translation:

None

RF Attenuator (ATTN_VAR)

269

RF Attenuator (ATTN_VAR)

This element is used to provide variable attenuation in the RF path. Furthermore, the return loss of the RF attenuator will be double the total attenuation. Input and output impedances can be specified by the user. The output impedance defaults to the input impedance unless otherwise specified by the user. This element allows the user to separate the insertion loss from the attenuation and provides an appropriate schematic. This system symbol is available in SCHEMAX in the System toolbar.

Netlist syntax:

ATTN n1 n2 IL= L= [Zin=] [Zout=] [Name=] Parameters:

IL Insertion Loss in dB.

L Attenuation (or Loss) in dB.

Zin Input Impedance in ohms (default is 50 ohms).

Zout Output Impedance in ohms (default is Zin).

The total attenuation of the variable attenuator is simply the insertion loss plus the attenuation. Insertion Loss and Attenuation is assumed to be constant across frequency.

Note: As the ratio of Zin to Zout gets very large or very small the input and output impedances will affect the total insertion loss of the attenuator.

Examples:

ATTN_VAR 1 2 L=3 Zin=50 Zout=75 Touchstone Translation:


None


270

Dual Directional Coupler (COUPLER2)

This element is used to provide coupling in the RF path. This system symbol is available in SCHEMAX in the System toolbar.

Netlist syntax:

COUPLER2 n1 n2 n3 n4 IL= CPL1= CPL2= [DIR1=] [DIR2=] [Z0=] [Name=] Parameters:

IL Total Insertion Loss in dB (nodes 1 to 2).

CPL1 Coupling in dB (nodes 1 to 3).

CPL2 Coupling in dB (nodes 2 to 4).

DIR1 Directivity in dB (nodes 2 to 3, default is 30 dB).

DIR2 Directivity in dB (nodes 1 to 4, default is 30 dB).

Z0 Reference Impedance in ohms (default is 50 ohms).

The coupler isolation (nodes 2 to 3 and 1 to 4) is equal to the coupling + directivity. Insertion Loss, Coupling, and Directivity is assumed to be constant across frequency.

Note: The total insertion loss of the coupler includes components due to attenuation and due to coupling. A warning is given if the specified "Total Insertion Loss" is less than the minimum theoretical loss due to coupling. This minimum amount equals: -10 log [ 1 - 10+CPL * 0.1] db.

Examples:

COUPLER2 1 2 3 4 IL=0.75 CPL1=20 CPL2=20 Touchstone Translation: None


Ideal three port circulator (CIR3)

271

Ideal three port circulator (CIR3)

This ideal element symbol is available in SCHEMAX in the LUMPED toolbar.

NOTE: This element is in the LUMPED toolbar.

Netlist syntax:

CIR3 n1 n2 n3 Z= [Name=] Parameters:

Z Reference resistance in ohms. Examples:

CIR3 1 2 0 Z=50 Touchstone Translation:

CIR3 n1 n2 n3 Default SPICE Translation:

NONE


272

RF Circulator (CIR)

This element is used to provide directional control of signals in the RF path. This system symbol is available in SCHEMAX in the System toolbar.

Netlist syntax:

CIR n1 n2 n3 IL= ISO= [Z0=] [Name=] Parameters:

IL Insertion Loss in dB (nodes 1 to 2, 2 to 3, 3 to 1).

ISO Isolation in dB (nodes 2 to 1, 3 to 2, 1 to 3, default is 30 dB).


Insertion Loss, and Isolation is assumed to be constant across frequency.

Note: As the isolation is reduced to the point that it begins to approach the insertion loss the total insertion loss will no longer be the value specified by the user.

Examples:

CIR 1 2 3 IL=0.75 ISO=40 Touchstone Translation:


None

Single RF Directional Coupler (COUPLER1)

273

Single RF Directional Coupler (COUPLER1)

This element is used to provide coupling in the RF path. This system symbol is available in SCHEMAX in the System toolbar.

Netlist syntax:

COUPLER1 n1 n2 n3 IL= CPL= [DIR=] [Z0=] [Name=] Parameters:

IL Insertion Loss in dB (nodes 1 to 2).

CPL Coupling in dB (nodes 1 to 3).

DIR Directivity in dB (default is 30 dB).


The coupler isolation (nodes 2 to 3) is equal to the coupling + directivity. Insertion Loss, Coupling, and Directivity is assumed to be constant across frequency.

Note: The total insertion loss of the coupler is affected by the amount of coupling. When the coupling in dB is very low more energy is passed to the coupled port and the total insertion loss of the coupler will be higher than the specified value.

Examples:

COUPLER1 1 2 IL=0.75 CPL=20 Touchstone Translation:


None


274

Time Delay (DELAY)

This element is used to provide a pure time delay in the RF path. This system symbol is available in SCHEMAX in the System toolbar and the LUMPED toolbar.

Netlist syntax:

DELAY n1 n2 T= [Z0=] [Name=] Parameters:

T Time delay in ns.

Z0 Reference Impedance in ohms (default = 50) Note: The time delay must be greater or equal to zero. The time delay creates a linear phase shift as a function of frequency (f) of the form :

S21 = e-j 2 pi f T .

In the reverse direction, S12 = S21 . An alternate formulation (Model DELAY2) is available where S12 is the complex conjugate of S21. DELAY2 is available by choosing "Model" on the DELAY dialog box. This brings up the "Change Model" option. Under "New Model" select "DELAY2".

Examples:

DELAY 1 2 T=10

Touchstone Translation:

DELAY 1 2 T=10

Default SPICE Translation:

None

Ideal gain block (GAIN) - LINEAR

275

Ideal gain block (GAIN) - LINEAR



Note: n3 is normally grounded.

Netlist syntax:

GAIN n1 n2 n3 A= S= F= [Name=] Parameters:

A Flat gain for 0<FREQ<F (dB)

S Gain slope for FREQ>=F (dB/octave)

F Frequency at which gain slope starts (MHz). Examples:

GAIN 1 2 0 A=6 S=6 F=4 Touchstone Translation:

GAIN n1 n2 A= S= F= Default SPICE Translation:

None


276

Hybrid 90 Degree Coupler (HYBRID1)

This element is used to provide coupling in the RF path. This system symbol is available in SCHEMAX in the System toolbar. The default is an equal power split (3 db) between the "direct" port (-90 deg) and the "coupled" port (0 deg). Both paths are subject to the insertion loss.

Netlist syntax:

HYBRID1 n1 n2 n3 n4 IL= [CPL=] [ISO=] [GBAL=] [PBAL=] [Z0=] [Name=] Parameters:

IL Total Insertion Loss in dB (nodes 1 to 3 and 1 to 4, also for nodes 2 to 3 and 2 to 4). CPL Coupling in dB (nodes 1 to 3 and 1 to 4, default is 3 db). ISO Isolation in dB (nodes 1 to 2, default is 50 dB). GBAL Gain balance (gain difference between 0 deg and 90 deg paths, default is 0). PBAL Phase balance (phase difference between 0 deg and 90 deg paths, default is 0). Z0 Reference Impedance in ohms (default is 50 ohms).

The gain balance error is equally divided between the direct and coupled paths. However, the phase balance is associated with the direct (-90 deg) path only. The resulting s-parameters for the two paths are:

S31 = [ -IL (db) ] + [ -CPL (db) ] + [ 0.5 * GBAL (db) ] phase = 0 deg

S41 = [ -IL (db) ] + [ -CPL (db) ] + [- 0.5 * GBAL (db) ] phase = -90 deg - PBAL deg

Note: The coupling must always be greater than the insertion loss. If not, an error message will be provided. In addition, a warning is supplied if the gain balance is greater than the coupling.

Examples:

HYBRID1 1 2 3 4 IL=0.75 CPL=3 ISO=30 GBAL=0.1 PBAL=5.0 Touchstone Translation: None


RF Isolator (ISO)

277

RF Isolator (ISO)

This element is used to provide directional control of signals in the RF path. This system symbol is available in SCHEMAX in the System toolbar.

Netlist syntax:

ISO n1 n2 IL= ISO= [Z0=] [Name=] Parameters:

IL Insertion Loss in dB (nodes 1 to 2).

ISO Isolation in dB (nodes 2 to 1, default is 50 dB).

Z0 Reference Impedance in ohms (default is 50 ohms). Insertion Loss, and Isolation is assumed to be constant across frequency.


Examples:

ISO 1 2 IL=0.75 ISO=40 Touchstone Translation:


None


278

Ideal isolator (ISOLATOR)



Note: n3 is normally grounded.

Netlist syntax:

ISOLATOR n1 n2 n3 Z= [Name=] Parameters:

Z Reference resistance in ohms. Examples:

ISOLATOR 1 2 0 Z=50 Touchstone Translation:

ISOLATOR n1 n2 Default SPICE Translation:

None

LOG_DET (Log Detector)

279

LOG_DET (Log Detector)

This element is used to provide a dc output voltage proportional to the power of the RF input signal. This system symbol is available in SCHEMAX in the System toolbar.

Netlist syntax:

LOG_DET n1 n2 SLP=[INCPT=] [VMIN=] [VSAT=] [NFLR=] [Name=] Parameters:

SLP Slope of the output voltage scaling in v/dB.

INCPT Intercept on the power axis in dB.

VMIN Output voltage threshold in volts.

VSAT Output voltage saturation in volts.

The voltage scaling is as shown in the diagram below. The voltage is a linear function of the RF power with a given slope (SLP) within the range of VMIN to VSAT.

For additional details on amplifier models see the System Manual.

Examples:

LOG_DET n1 n2 SLP=0.1 INCPT=0 VMIN=1 VSAT=10

Touchstone Translation: None



280

RF Mixer (MIXERA, MIXERP)

This element is used to combine RF and Local Oscillator signals to generate sum and difference signals in the RF path. This system symbol is available in SCHEMAX in the System toolbar. There are two models: MIXERA ( Active), MIXERP (Passive). The only difference between the Active and Passive mixer is that the Active mixer has conversion gain and the Passive mixer has conversion loss.

Netlist syntax:

MIXERA n1 n2 CG= SUM= [LO=] [LTOR=] [LTOI=] [RTOI=] [Ip1db=] [Ipsat=] [IIP3=] [IIP2=] [Z0=] [IR=] [NF=] [Name=]

Parameters:

CL Conversion loss in dB (Passive Only)

CG Conversion gain in dB (Active Only)

SUM Desired output: Difference=0, Sum=1.

LO Local Oscillator drive level in dBm (default is 7 dBm).

LTOR Local oscillator to RF isolation in dB (default is 30 dB).*

LTOI Local oscillator to IF isolation in dB (default is 30 dB).*

RTOI RF to IF isolation in dB (default is 50 dB).*

Ip1db Input 1dB compression in dBm (default is 1 dBm).

Ipsat Input saturation power in dBm (default is 2 dBm).

IIP3 Input IP3 in dBm (default is 11 dBm).

IIP2 Input IP2 in dBm (default is 22 dBm).

Z0 Reference impedance in ohms (default is 50 ohms).*

IR Image Rejection in dB (default is 0 dB).

NF Noise Figure in dB (default is 0 dB).

RF Mixer (MIXERA, MIXERP)

281

* For Linear simulation only these variables are used. There is no frequency translation, only isolation. The resulting s-parameters are: S12 = S21 = -RTOI, S13 = S31 = -LTOR, S23 = S32 = -LTOI.

For additional details on mixer models see the Mixer section of the System Manual.

Examples:

MIXERA 1 2 CG=6 SUM=0 LO=7 LTOR=30 LTOI=30 RTOI=50 Ip1db=1 Ipsat=2 IIP3=11 IIP2=22



WARNING: For GENESYS Version 8.1, this model is not supported by HARBEC.


282

Antenna Path Loss (PATH)

This element is used to provide antenna gains and path losses for a pair of antennas. This system symbol is available in SCHEMAX in the System toolbar.

Netlist syntax:

PATH n1 n2 G1= G2= Lossa= Lossb= DIST= Loss1= Loss2= [ZIN=] [ZOUT=] Parameters:

G1 Gain of Antenna #1 in dB (default = 0 dB).

G2 Gain of Antenna #2 in dB (default = 0 dB).

Lossa Path loss for given distance (DIST) in dB/decade (default = 40 dB/decade).

Lossb Path loss at unit distance (DIST=1) (default = 100 dB).

DIST Distance between antennas (default = 1).

Loss1 Fixed loss #1 in dB (default = 0 dB).

Loss2 Fixed loss #2 in dB (default = 0 dB).

ZIN Input impedance in ohms (Port 1) (default is 50 ohms).

ZOUT Output impedance in ohms (Port 2) (default is ZIN). The coupled antenna gains and path losses are assumed to be constant across frequency. The total path loss is computed as:

Total Loss = Lossb + [Lossa * log10 (DIST)] -G1 - G2 + Loss1 + Loss2

The units for distance is miles. Therefore, the loss at one mile is 100 dB.

Note: The antenna gains should be positive. The losses must also be positive. The input and output impedances must be non-zero.

Examples:

PATH 1 2 G1=3 G2=6 LOssa=40 Lossb=100 DIST=100 Loss1=3 Loss2=10 Touchstone Translation: None


Ideal Phase Shift (PHASE)

283

Ideal Phase Shift (PHASE)

This element is used to provide a phase lag in the RF path. This system symbol is available in SCHEMAX in the System toolbar and the LUMPED toolbar.

Netlist syntax:

PHASE n1 n2 A= S= F= [Z0=] [Name=] Parameters:

A Constant phase shift for 0<FREQ<F (in degrees)

S Phase slope for FREQ>F (in degrees/octave)

F Frequency for onset of slope (in MHz)

Z0 Reference Impedance in ohms (default = 50)

Examples:

PHASE 1 2 A=45 S=45 F=5 Note: These elements can be cascaded to obtain arbitrary phase responses. The frequency (F) must be greater or equal to zero. The time delay creates a linear phase shift as a function of frequency (f) of the form :

S21 = e-j 2 pi f T .

In the reverse direction, S12 = S21 . An alternate formulation (PHASE2) is available where S12 is the complex conjugate of S21. PHASE2 is available by choosing "Model" on the PHASE dialog box. This brings up the "Change Model" option. Under "New Model" select "PHASE2". Use the same symbol.

Touchstone Translation:

PHASE n1 n2 A= S= F= Default SPICE Translation:

None


284

RF Amplifier (RFAMP)

This element is used to provide gain in the RF path. This system symbol is available in SCHEMAX in the System toolbar.

Netlist syntax:

RFAMP n1 n2 G= NF= [Op1db=] [Opsat=] [OIP3=] [OIP2=] [RISO=] [Z0=] [FC=] [Slope=] [Name=]

Parameters:

G Gain in dB.*

NF Noise Figure in dB.

Op1db Output 1db compression in dBm (default is 60 dBm).

Opsat Output Saturation Power (default is 63 dBm).

OIP3 Output IP3, in dBm (default is 70 dBm).


RISO Reverse Isolation in dB (default is 50 dB).*


FC Corner frequency in MHz (default is 1000 MHz).

slope Rolloff Slope in dB/decade (default is 0 dB/decade).

* For Linear operation, only these variables are used. The resulting s-parameters are: S21 = +G db, S12 = -RISO db.

The amplifier model includes the nonlinear effect of saturation or compression and the addition of noise. The default values for: Op1db, Opsat, OIP3, and OIP2 are a reasonably consistent set on nominal parameters. Their relative magnitudes are typically: Op1db < Opsat < OIP3 < OIP2. The absolute magnitudes are higher than typical networks. Rules of thumb for these parameters are:

IP2 = IP3 + ( 10 or 15 dBm), IP3 = Ip1db + (10 or 15 dBm), [ where leading "I" refers to Input, and "O" to Output]

RF Amplifier (RFAMP)

285

Op1db = OIP3 - 10.6 dBm, Ip1db = IIP3 - 9.6 dBm.


Note: The corner frequency and rolloff slope must be positive. The gain and reverse isolation should be greater than zero.

Examples:

RFAMP 1 2 G=10 NF=3 Op1db=60 Opsat=63 OIP3=70 OIP2=80 RISO=50 Touchstone Translation: None




286

RF Switch SPDT (SPDT)

This element is used to provide switched control of signals in the RF path. The user can set the switch in any one of three switch states, off, output 1, or output 2. This model supports both absorptive and reflective switches. The default switch is an absorptive switch with has Zopen (default is 50 ohm) impedances for all open switch ports. For a reflective switch the user can specify the open port impedance. Furthermore, the user can change the switch symbol to represent the state of the switch. This system symbol is available in SCHEMAX in the System toolbar.

Default Symbol: Alternate symbols that can be changed by the user:

Netlist syntax:

SPDT n1 n2 n3 IL= ISO= State= [Z0=] [Zopen=] [Name=] Parameters:

IL Insertion Loss in dB (between input and outputs 1 or 2).

ISO Isolation in dB (between input and output in off position, default is 30 dB).

State State of the switch 0-Off, 1-Output 1, and 2-Output 2 (default is 1).


Zopen Open Port Impedance in ohms (default is Z0). Insertion Loss, and Isolation is assumed to be constant across frequency.


Examples:

SPDT 1 2 3 IL=0.5 ISO=35 State=2 Zopen=complex(5,25) Touchstone Translation:


None

RF 2 Way - 0 Splitter / Combiner (SPLIT2)

287

RF 2 Way - 0° Splitter / Combiner (SPLIT2)

This element is used to split or combine RF paths. The phase difference between the two split paths is 0 degrees. This system symbol is available in SCHEMAX in the System toolbar.

Netlist syntax:

SPLIT2 n1 n2 n3 [IL=] [ISO=] [Gbal2=] [PH2=] [PH3=] [Z0=] [Name=] Parameters:

IL Insertion Loss in dB (nodes 1 to 2, 1 to 3, default is 3.0 dB).


Gbal2 Gain balance in dB (gain difference between paths 1->2, 1->3), default is 0).

PH2 Phase of output node 2 with respect to the input in degrees (default is 0).

PH3 Phase of output node 3 with respect to the input in degrees ( default is 0).

Z0 Reference Impedance in ohms (default is 50 ohms). Insertion loss, phase and isolation are assumed to be constant across frequency. The minimum insertion loss of an ideal splitter is 10*Log(1/N) dB, where N the number of paths. The gain balance error is assigned to the 1 -> 3 path only. However, the phase specifications apply to each output with respect to the input. The resulting s-parameters for the two paths are:

S21 = [ -IL (db) ] with phase = PH2 deg

S31 = [ -IL (db) ] + [ Gbal2 (db) ] with phase = PH3 deg

Note: As the isolation is reduced to the point that it begins to approach the insertion loss, the total insertion loss will no longer be the value specified by the user. Phase for each path should be negative.

Examples:

SPLIT2 1 2 3 IL=3.5 ISO=35 Gbal2=0.1 PH2=2 PH3=4 Touchstone Translation: None



288

RF 2 Way - 0°/ 180° Splitter / Combiner (SPLIT2180)


Netlist syntax:




Gbal2 Gain balance in dB (gain difference between paths(1->2, 1->3), default is 0).

PH2 Phase of node 2 with respect to input in degrees ( default is 0 degrees).

PH3 Phase of node 3 with respect to input in degrees ( default is -180 degrees).

Z0 Reference Impedance in ohms (default is 50 ohms). Insertion loss, phase and isolation are assumed to be constant across frequency. The minimum insertion loss of an ideal splitter is 10*Log(1/N) dB, where N the number of paths. The gain balance error is added to path 1 ->3 only. However, the phase specs apply to each output with respect to the input. The resulting s-parameters are:


S31 = [ -IL (db) ] + [Gbal2 (db) ] with phase = PH3 deg


Examples:

SPLIT2180 1 2 3 IL=3.5 ISO=35 Gbal2=-0.1 PH2=0 PH3=-180 Touchstone Translation: None


RF 2 Way - 0 / 90 Splitter / Combiner (SPLIT290)

289

RF 2 Way - 0°/ 90° Splitter / Combiner (SPLIT290)


Netlist syntax:






PH3 Phase of node 3 with respect to input in degrees ( default is -90 degrees).

Z0 Reference Impedance in ohms (default is 50 ohms). Insertion loss, phase and isolation are assumed to be constant across frequency. The minimum insertion loss of an ideal splitter is 10*Log(1/N) dB, where N the number of paths. The gain balance error is added to path 1 ->3 only. However, the phase specs apply to each output with respect to the input. The resulting s-parameters are:




Examples:

SPLIT290 1 2 3 IL=3.5 ISO=35 Gbal2=-0.1 PH2=0 PH3=-92 Touchstone Translation: None



290


This element is used to split or combine RF paths. The phase difference between the three split paths is 0 degrees. It is available in SCHEMAX in the System toolbar.

Netlist syntax:

SPLIT3 n1 n2 n3 n4 [IL=] [ISO=] [Gbal2=0] [Gbal3=] [PH2=] [PH3=] [PH4=] [Z0=] Parameters:

IL Insertion Loss in dB (nodes 1 to 2, 1 to 3, 1 to 4, default is 4.8 dB).

ISO Isolation in dB (nodes 2 to 3, 3 to 4, 2 to 4, default is 30 dB).



PH2 Phase of node 2 with respect to input in degrees (default is 0 degrees).



Z0 Reference Impedance in ohms (default is 50 ohms). Insertion loss, phase and isolation are assumed to be constant across frequency. The minimum insertion loss of an ideal splitter is 10*Log(1/N) dB, where N the number of paths. The gain balance error is the gain difference from the nominal path (i.e. path 1 -> 2). However, the phase specifications apply to each output with respect to the input. The resulting s-parameters for the two paths are:



S41 = [ -IL (db) ] + [ Gbal3(db) ] with phase = PH4 deg

Note: As the isolation is reduced to the point that it begins to approach the insertion loss the total insertion loss will no longer be the value specified by the user. Phase of each path should be negative. The total output energy must not exceed the input energy.

Example: SPLIT3 1 2 3 4 IL=5.0 ISO=35 Gbal2=-0.1 Gbal3=-0.1 PH2=2 PH3=2 PH4=2


291


This element is used to split or combine RF paths. The phase difference between the four split paths is 0 degrees. This system symbol is available in SCHEMAX in the System toolbar.

Netlist syntax:

SPLIT4 n1 n2 n3 n4 n5 [IL=] [ISO=] [Gbal2=] [Gbal3=] [Gbal4=] [PH2=] [PH3=] [PH4=] [PH5=] [Z0=] [Name=]

Parameters:

IL Insertion Loss in dB (nodes 1 to 2, 1 to 3, 1 to 4, 1 to 5, default is 6.021 dB).

ISO Isolation in dB (between any combination of nodes 2 thru 5, default is 30 dB).













292



Examples:

SPLIT4 1 2 3 4 5 IL=6.8 ISO=25 Gbal2=-0.1 Gbal3=-0.1 Gbal4=-0.1 PH2=2 PH3=2 PH4=2 PH5=2




293


This element is used to split or combine RF paths. The phase difference between the five split paths is 0 degrees. This system symbol is available in SCHEMAX in the System toolbar.

Netlist syntax:

SPLIT5 n1 n2 n3 n4 n5 n6 [IL=] [ISO=] [Gbal2=] [Gbal3=] [Gbal4=] [Gbal5=] [PH2=] [PH3=] [PH4=] [PH5=] [PH6=] [Z0=] [Name=]

Parameters:

IL Insertion Loss in dB (nodes 1 to 2, 1 to 3, 1 to 4, 1 to 5, default is 7.0 dB).

ISO Isolation in dB (between any combination of nodes 2 thru 5, default is 30 dB).












294



S41 = [ -IL (db) ] + [Gbal3(db) ] with phase = PH4 deg




Examples:

SPLIT5 1 2 3 4 5 6 IL=6.8 ISO=25 Gbal2=-0.1 Gbal3=-0.1 Gbal4=-0.1 PH2=2 PH3=2 PH4=2 PH5=3 PH6=3



RF Switch SPST (SPST)

295

RF Switch SPST (SPST)

This element is used to provide switched control of signals in the RF path. The user can set the switch in any one of three switch states, off or on. This model supports both absorptive and reflective switches. The default switch is an absorptive switch with has 50 ohm port impedances for all open switch ports. For a reflective switch the user can specify the open port impedance. Furthermore, the user change change the switch symbol to represent the state of the switch. For This system symbol is available in SCHEMAX in the System toolbar.

Default Symbol: Alternate symbols that can be changed by the user:

Netlist syntax:

SPST n1 n2 IL= ISO= State= [Z0=] [Zopen=] [Name=] Parameters:

IL Insertion Loss in dB (nodes 1 to 2 when closed).

ISO Isolation in dB (nodes 1 to 2 when open, default is 30 dB).

State State of the switch 0-Open, 1-Closed (default is 1).


Zopen Open Port Impedance in dB (default is Z0). Insertion Loss, and Isolation is assumed to be constant across frequency.


Examples:

SPST 1 2 IL=0.75 ISO=40 Touchstone Translation:


None


296

VGA (Variable Gain Amplifier)

This element is used to provide gain in the RF path. This system symbol is available in SCHEMAX in the System toolbar.

Netlist syntax:

VARAMP n1 n2 G= NF= [Op1db=] [Opsat=] [OIP3=] [OIP2=] [RISO=] [Z0=] [FC=] [Slope=] [GMIN=] [VSLOPE=] [Name=]

Parameters:

G Gain in dB.*

NF Noise Figure in dB.

Op1db Output 1db compression in dBm (default is 60 dBm).

Opsat Output Saturation Power (default is 63 dBm).



RISO Reverse Isolation in dB (default is 50 dB).*


FC Corner frequency in MHz (default is 1000 MHz).

slope Rolloff Slope in dB/decade (default is 0 dB/decade).

GMIN Minimum gain (default is 0).

VSLOPE Gain slope in dB/volt.

* For Linear operation, only these variables are used. The resulting s-parameters

VGA (Variable Gain Amplifier)

297

are: S21 = +G db, S12 = -RISO db.

The amplifier model includes the nonlinear effect of saturation or compression and the addition of noise. The default values for: Op1db, Opsat, OIP3, and OIP2 are a reasonably consistent set on nominal parameters. Their relative magnitudes are typically: Op1db < Opsat < OIP3 < OIP2. The absolute magnitudes are higher than typical networks. Rules of thumb for these parameters are:

IP2 = IP3 + ( 10 or 15 dBm), IP3 = Ip1db + (10 or 15 dBm), [ where leading "I" refers to Input, and "O" to Output]

Op1db = OIP3 - 10.6 dBm, Ip1db = IIP3 - 9.6 dBm.


Note: The corner frequency and rolloff slope must be positive. The gain and reverse isolation should be greater than zero.

Examples:

VARAMP 1 2 G=10 NF=3 Op1db=60 Opsat=63 OIP3=70 OIP2=80 RISO=30 GMIN=0 VSLOPE=0.5




Chapter 24: Filter Elements (System Toolbar)

Bessel Bandpass Filter (BPF_BESSEL)

This element is used to provide filtering in the RF path. This system symbol is available in SCHEMAX in the System toolbar.

Netlist syntax:

BPF_BESSEL n1 n2 FLO= FHI= N= [IL=] [Apass=] [AMAX=] [TYPE=] [Z1=] [Z2=] Parameters:

FLO Frequency of lower passband edge. FHI Frequency of higher passband edge. N Order of the filter. IL Insertion loss, in dB (default is 0 db). Apass Attenuation at passband edge, in dB (default is 3 dB). AMAX Maximum attenuation in stopband, in dB (default is 100 dB). TYPE Input impedance in stopband, short = 0, open = 1 (default is open). Z1 Input impedance in ohms (default is 50 ohms). Z2 Output impedance in ohms (default is Z1).

The Bessel filter characteristic has a flat group delay response in the passband generated by poles only. This results in no ripple in the passband, but a cutoff which is less sharp than some other filters. The insertion loss only affects the forward (S21) and backward (S12) transmission, but not the reflection coefficients (S11,S22). The input impedance in the stopband only affects the phase of the reflection coefficients. For additional details on filter types see the FILTER Synthesis Manual.

Note: The insertion loss and passband attenuation must be greater or equal to zero. The filter order must be an integer greater or equal to 1. The frequencies of the passband edges must be positive and the higher frequency must be larger than the lower frequency.

Examples:

BPF_BESSEL 1 2 FLO=2 FHI=4 N=4 Apass=6 TYPE=0 Touchstone Translation: None


Filter Elements (System Toolbar)

300

Butterworth Bandpass Filter (BPF_BUTTER)


Netlist syntax:

BPF_BUTTER n1 n2 FLO= FHI= N= [IL=] [Apass=] [AMAX=] [TYPE=] [Z1=] [Z2=] Parameters:

FLO Frequency of lower passband edge.

FHI Frequency of higher passband edge.

N Order of the filter.

IL Insertion loss, in dB (default is 0 db).

Apass Attenuation at passband edge, in dB (default is 3 dB).

AMAX Maximum attenuation in stopband, in dB (default is 100 dB).

TYPE Input impedance in stopband, short = 0, open = 1 (default is open).

Z1 Input impedance in ohms (default is 50 ohms).

Z2 Output impedance in ohms (default is Z1). The Butterworth filter characteristic is a maximally flat response in the passband generated by poles only. This results in no ripple in the passband, but a cutoff which is less sharp than some other filters. The insertion loss only affects the forward (S21) and backward (S12) transmission, but not the reflection coefficients (S11,S22). The input impedance in the stopband only affects the phase of the reflection coefficients.


Examples:

BPF_BUTTER 1 2 FLO=2 FHI=4 N=4 Apass=6 TYPE=0 Touchstone Translation: None

Chebyshev Bandpass Filter (BPF_CHEBY)

301

Chebyshev Bandpass Filter (BPF_CHEBY)


Netlist syntax:

BPF_CHEBY n1 n2 FLO= FHI= N= R= [IL=] [Apass=] [AMAX=] [TYPE=] [Z1=] [Z2=] Parameters:

FLO Frequency of lower passband edge. FHI Frequency of higher passband edge. N Order of the filter. R Ripple, in dB. IL Insertion loss, in dB. Apass Attenuation at passband edge, in dB (default is ripple). AMAX Maximum attenuation in stopband, in dB (default is 100 dB). TYPE Input impedance in stopband, short = 0, open = 1 (default is open). Z1 Input impedance in ohms (default is 50 ohms). Z2 Output impedance in ohms (default is Z1).

The Chebyshev filter characteristic exhibits ripple in the passband and generated by poles only. This results in a cutoff which is sharper than some other filters. The insertion loss only affects the forward (S21) and backward (S12) transmission, but not the reflection coefficients (S11,S22). The input impedance in the stopband only affects the phase of the reflection coefficients. The nominal value for the attenuation at the passband edge (Apass) is the ripple value. For filters of even order, the gain at dc is less than unity to avoid gains greater than unity in the passband.

Note: The insertion loss and passband attenuation must be greater or equal to zero. The filter order must be an integer greater or equal to 2. The frequency of the passband edges must be positive and the higher frequency must be larger than the lower frequency.

Example:

BPF_CHEBY 1 2 FLO=2 FHI=4 N=5 R=0.5 Apass=6 TYPE=0 Touchstone Translation: None



302

Elliptic Bandpass Filter (BPF_ELLIPTIC)


Netlist syntax:

BPF_ELLIPTIC n1 n2 FLO= FHI= N= R= Sbattn= [IL=] [AMAX=] [TYPE=] [Z1=] [Z2=] [Name=]

Parameters:

FLO Frequency of ripple lower passband edge. FHI Frequency of ripple higher passband edge. N Order of the filter. R Ripple, in dB. Sbattn Minimum stopband attenuation, in dB. IL Insertion loss, in dB (default is 0 db). AMAX Maximum attenuation in stopband, in dB (default is 100 dB). TYPE Input impedance in stopband, short = 0, open = 1 (default is open). Z1 Input impedance in ohms (default is 50 ohms). Z2 Output impedance in ohms (default is Z1).

The Elliptic filter characteristic exhibits ripple in the passband and generated by poles and zeros. This results in a cutoff which is sharper than most other filters. The insertion loss only affects the forward (S21) and backward (S12) transmission, but not the reflection coefficients (S11,S22). The input impedance in the stopband only affects the phase of the reflection coefficients. The value for the attenuation at the passband edge (Apass) is the ripple value. For filters of even order, the gain at dc is less than unity to avoid gains greater than unity in the passband. For additional details on filter types see the FILTER Synthesis Manual.

Note: The insertion loss must be greater or equal to zero. The filter order must be an integer greater or equal to 2. The frequencies of the passband edges must be positive and the higher frequency must be larger than the lower frequency. The stopband attenuation must be greater than the ripple.

Examples:

BPF_ELLIPTIC 1 2 FLO=2 FHI=4 N=5 R=0.5 Sbattn=20 TYPE=0

Pole / Zero Bandpass Filter (BPF_POLES)

303

Pole / Zero Bandpass Filter (BPF_POLES)


Netlist syntax:

BPF_POLES n1 n2 Poles= Zeros= FLO= FHI= Gain Factor= [AMAX=] [TYPE=] [IL=] [Z1=] [Z2=] [Name=]

Parameters:

Poles List of poles, in complex form: complex(a,b); complex(c,d)...* Zeros List of zeros, in complex form: complex(e,f); complex(g,h)...* Gain Factor Transfer function gain.** FLO Frequency at lower passband edge, in MHz. FHI Frequency at higher passband edge, in MHz. AMAX Maximum attenuation in stopband, in dB (default is 100 dB). TYPE Input impedance in stopband, short = 0, open = 1 (default is open). IL Insertion loss, in dB (default = 0 dB). Z1 Input impedance in ohms (default is 50 ohms). Z2 Output impedance in ohms (default is Z1).

* Roots are normalized with respect to the frequency of the passband edge in rad/sec.

** If gain is greater than unity (non-passive network) at any frequency, the gain of the entire filter is reduced until the maximum gain is unity.

The filter transfer function for the low frequency prototype is of the form:

G (s) = Gain Factor * [ s-complex (e,f)] [s-complex(g,h)] / [s-complex(a,b)] [s-complex(c,d)]

The generalized pole/zero filter characteristic completely defined by the user. The specified poles and zeros define the low frequency prototype for the filter. Transformations are used as necessary for highpass, bandpass, and bandstop variants. The insertion loss only affects the forward (S21) and backward (S12) transmission, but not the reflection coefficients (S11,S22). The input impedance in the stopband only affects the phase of the reflection coefficients.


304

Note: The insertion loss and maximum stopband attenuation must be greater or equal to zero. The frequencies of the passband edges must be positive and the higher frequency must be larger than the lower frequency. The number of poles must be 1 or greater.

Examples:

BPF_BUTTER 1 2 Poles=complex(-0.7,0.7);complex(-0.7,-0.7) Zeros=complex(-1.0,0) Gain Factor=1.0

FLO=2 FHI=4 AMAX=100 TYPE=0 Touchstone Translation: None


Bessel Bandstop Filter (BSF_BESSEL)

305

Bessel Bandstop Filter (BSF_BESSEL)


Netlist syntax:

BSF_BESSEL n1 n2 FLO= FHI= [Apass=] [AMAX=] [TYPE=] [IL=] N= [Z1=] [Z2=] [Name=]

Parameters:

FLO Frequency of lower passband edge, in MHz. FHI Frequency of higher passband edge, in MHz. N Order of the filter. IL Insertion loss, in dB. Apass Attenuation at passband edge, in dB (default is 3 dB). AMAX Maximum attenuation in stopband, in dB (default is 100 dB). TYPE Input impedance in stopband, short = 0, open = 1 (default is open). Z1 Input impedance in ohms (default is 50 ohms). Z2 Output impedance in ohms (default is Z1).



Examples:

BSF_BESSEL 1 2 FLO=2 FHI=4 Apass=6 TYPE=0 N=4 Touchstone Translation: None



306

Butterworth Bandstop Filter (BSF_BUTTER)


Netlist syntax:

BSF_BUTTER n1 n2 FLO= FHI= [Apass=] [AMAX=] [TYPE=] [IL=] N= [Z1=] [Z2=] [Name=]

Parameters:

FLO Frequency of lower passband edge, in MHz. FHI Frequency of higher passband edge, in MHz. N Order of the filter. IL Insertion loss, in dB. Apass Attenuation at passband edge, in dB (default is 3 dB). AMAX Maximum attenuation in stopband, in dB (default is 100 dB). TYPE Input impedance in stopband, short = 0, open = 1 (default is open). Z1 Input impedance in ohms (default is 50 ohms). Z2 Output impedance in ohms (default is Z1).

The Butterworth filter characteristic is a maximally flat response in the passband generated by poles only. This results in no ripple in the passband, but a cutoff which is less sharp than some other filters. The insertion loss only affects the forward (S21) and backward (S12) transmission, but not the reflection coefficients (S11,S22). The input impedance in the stopband only affects the phase of the reflection coefficients. For additional details on filter types see the FILTER Synthesis Manual.


Examples:

BSF_BUTTER 1 2 FLO=2 FHI=4 Apass=6 TYPE=0 N=4 Touchstone Translation: None


Chebyshev Bandstop Filter (BSF_CHEBY)

307

Chebyshev Bandstop Filter (BSF_CHEBY)


Netlist syntax:

BSF_CHEBY n1 n2 FLO= FHI= [Apass=] [AMAX=] [TYPE=] [IL=] N= R= [Z1=] [Z2=] [Name=]

Parameters:

FLO Frequency of lower passband edge, in MHz. FHI Frequency of higher passband edge, in MHz. N Order of the filter. R Ripple, in dB. IL Insertion loss, in dB. Apass Attenuation at passband edge, in dB (default is ripple). AMAX Maximum attenuation in stopband, in dB (default is 100 dB). TYPE Input impedance in stopband, short = 0, open = 1 (default is open). Z1 Input impedance in ohms (default is 50 ohms). Z2 Output impedance in ohms (default is Z1).

The Chebyshev filter characteristic exhibits ripple in the passband and generated by poles only. This results in a cutoff which is sharper than some other filters. The insertion loss only affects the forward (S21) and backward (S12) transmission, but not the reflection coefficients (S11,S22). The input impedance in the stopband only affects the phase of the reflection coefficients. The nominal value for the attenuation at the passband edge (Apass) is the ripple value. For filters of even order, the gain at dc is less than unity to avoid gains greater than unity in the passband. For additional details on filter types see the FILTER Synthesis Manual.


Examples:

BSF_CHEBY 1 2 FLO=2 FHI=4 Apass=6 TYPE=0 N=5 R=0.5 Touchstone Translation: None



308

Elliptic Bandstop Filter (BSF_ELLIPTIC)


Netlist syntax:

BSF_ELLIPTIC n1 n2 FLO= FHI= [AMAX=] [TYPE=] [IL=] N= R= Sbattn= [Z1=] [Z2=] Parameters:

FLO Frequency of ripple lower passband edge, in MHz. FHI Frequency of ripple higher passband edge, in MHz. N Order of the filter. R Ripple, in dB. Sbattn Stopband attenuation, in dB. IL Insertion loss, in dB. AMAX Maximum attenuation in stopband, in dB (default is 100 dB). TYPE Input impedance in stopband, short = 0, open = 1 (default is open). Z1 Input impedance in ohms (default is 50 ohms). Z2 Output impedance in ohms (default is Z1).



Examples:

BSF_ELLIPTIC 1 2 FLO=2 FHI=4 TYPE=0 N=5 R=0.5 Sbattn=20 Touchstone Translation: None


Pole / Zero Bandstop Filter (BSF_POLES)

309

Pole / Zero Bandstop Filter (BSF_POLES)


Netlist syntax:

BSF_POLES n1 n2 Poles= Zeros= FLO= FHI= Gain Factor= [AMAX=] [TYPE=] [IL=] [Z1=] [Z2=] [Name=]

Parameters:

Poles List of poles, in complex form: complex(a,b); complex(c,d)...*

Zeros List of zeros, in complex form: complex(e,f); complex(g,h)...*

Gain Factor Transfer function gain.**

FLO Frequency at lower passband edge, in MHz.

FHI Frequency at higher passband edge, in MHz.



IL Insertion loss, in dB (default = 0 dB).


Z2 Output impedance in ohms (default is Z1).





The generalized pole/zero filter characteristic completely defined by the user. The specified poles and zeros define the low frequency prototype for the filter.


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Transformations are used as necessary for highpass, bandpass, and bandstop variants. The insertion loss only affects the forward (S21) and backward (S12) transmission, but not the reflection coefficients (S11,S22). The input impedance in the stopband only affects the phase of the reflection coefficients.

Note: The insertion loss and maximum stopband attenuation must be greater or equal to zero. The frequencies of the passband edges must be positive and the higher frequency must be larger than the lower frequency. The number of poles must be 1 or greater.

Examples:

BSF_BUTTER 1 2 Poles=complex(-0.7,0.7);complex(-0.7,-0.7) Zeros=complex(-1.0,0) Gain Factor=1.0

FLO=2 FHI=4 AMAX=100 TYPE=0 Touchstone Translation: None


Duplexer with Chebyshev Filters (DUPLEXER_C)

311

Duplexer with Chebyshev Filters (DUPLEXER_C)

This element is used to provide a duplexer function in the RF path, made from two Chebyshev bandpass filters. The filters are marked "A" and "B" in the symbol. This system symbol is available in SCHEMAX in the System toolbar.

Netlist syntax:

DUPLEXER_C n1 n2 n3 FLOA= FHIA= FLOB= FHIB= NA= NB= RA= RB= ILA= ILB= Apass= [AMAX=] [ZIN=] [ZOUT=] [Name=]

Parameters:

FLOA Frequency of lower passband edge, Filter A. FHIAFrequency of higher passband edge, Filter A. FLOB Frequency of lower passband edge, Filter B. FHIB Frequency of higher passband edge, Filter B. NAOrder of the filter, Filter A. NB Order of the filter, Filter B. RA Ripple, Filter A, in dB. RB Ripple, Filter B, in dB. ILA Insertion loss, Filter A, in dB (default is 0 db). ILB Insertion loss, Filter B, in dB (default is 0 db). Apass Attenuation at passband edge, in dB (default is ripple). AMAX Maximum attenuation in stopband, in dB (default is 100 dB). ZIN Input impedance in ohms (default is 50 ohms). ZOUT Output impedances for Filters A & B, in ohms (default is 50 ohms).

The duplexer is a pair of filters with one common port. In this case the filters are of the Chebyshev type.The filter characteristic exhibits ripple in the passband and generated by poles only. Typically the value used for the attenuation at the passband edge (Apass) is set equal to the ripple value. An alternative method of forming a duplexer is to use two separate filter elements and connecting them together in the schematic.



312

Examples:

DUPLEXER_C 1 2 3 FLOA=1600 FHIA=1800 FLOB=1900 FHIB=2100 NA=5 NB=5 RA=0.5 RB=0.5 ILA=0.5 ILB=0.5 Apass=60.5 AMAX=100



Duplexer with Elliptic Filters (DUPLEXER_E)

313

Duplexer with Elliptic Filters (DUPLEXER_E)

This element is used to provide a duplexer function in the RF path, made from two Elliptic bandpass filters. The filters are marked "A" and "B" in the symbol. This system symbol is available in SCHEMAX in the System toolbar.

Netlist syntax:

DUPLEXER_E n1 n2 n3 FLOA= FHIA= FLOB= FHIB= Sbattn= [AMAX=] ILA= ILB= NA= NB= RA= RB= [ZIN=] [ZOUT=] [Name=]

Parameters:

FLOA Frequency of lower passband edge, Filter A. FHIA Frequency of higher passband edge, Filter A. FLOB Frequency of lower passband edge, Filter B. FHIB Frequency of higher passband edge, Filter B. NA Order of the filter, Filter A. NB Order of the filter, Filter B. RA Ripple, Filter A, in dB. RB Ripple, Filter B, in dB. Sbattn Minimum stopband attenuation, in dB. ILA Insertion loss, Filter A, in dB (default is 0 db). ILB Insertion loss, Filter B, in dB (default is 0 db). AMAX Maximum attenuation in stopband, in dB (default is 100 dB). ZIN Input impedance in ohms (default is 50 ohms). ZOUT Output impedances for Filters A & B, in ohms (default is 50 ohms).

The duplexer is a pair of filters with one common port. In this case the filters are of the Elliptic type. The Elliptic filter characteristic exhibits ripple in the passband and generated by poles and zeros. This results in a cutoff which is sharper than most other filters. An alternative method of forming a duplexer is to use two separate filter elements and connecting them together in the schematic.



314

Examples:

DUPLEXER_E 1 2 3 FLOA=1600 FHIA=1800 FLOB=1900 FHIB=2100 NA=5 NB=5 RA=0.5 RB=0.5 ILA=0.5 ILB=0.5 Sbattn=660 AMAX=100



Bessel Highpass Filter (HPF_BESSEL)

315

Bessel Highpass Filter (HPF_BESSEL)


Netlist syntax:

HPF_BESSEL n1 n2 Fpass= [Apass=] [AMAX=] [TYPE=] [IL=] N= [Z1=] [Z2=] [Name=]

Parameters:

Fpass Frequency of passband edge, in MHz. N Order of the filter. IL Insertion loss, in dB. Apass Attenuation at passband edge, in dB (default is 3 dB). AMAX Maximum attenuation in stopband, in dB (default is 100 dB). TYPE Input impedance in stopband, short = 0, open = 1 (default is open). Z1 Input impedance in ohms (default is 50 ohms). Z2 Output impedance in ohms (default is Z1).


Note: The insertion loss and passband attenuation must be greater or equal to zero. The filter order must be an integer greater or equal to 1. The frequency of the passband edge must be positive.

Examples:

HPF_BESSEL 1 2 Fpass=2 Apass=6 TYPE=0 N=4 Touchstone Translation: None



316

Butterworth Highpass Filter (HPF_BUTTER)


Netlist syntax:

HPF_BUTTER n1 n2 Fpass= [Apass=] [AMAX=] [TYPE=] [IL=] N= [Z1=] [Z2=] [Name=]

Parameters:

Fpass Frequency of passband edge, in MHz. N Order of the filter. IL Insertion loss, in dB. Apass Attenuation at passband edge, in dB (default is 3 dB). AMAX Maximum attenuation in stopband, in dB (default is 100 dB). TYPE Input impedance in stopband, short = 0, open = 1 (default is open). Z1 Input impedance in ohms (default is 50 ohms). Z2 Output impedance in ohms (default is Z1).

The Butterworth filter characteristic is a maximally flat response in the passband generated by poles only. This results in no ripple in the passband, but a cutoff which is less sharp than some other filters. The insertion loss only affects the forward (S21) and backward (S12) transmission, but not the reflection coefficients (S11,S22). The input impedance in the stopband only affects the phase of the reflection coefficients. For additional details on filter types see the FILTER Synthesis Manual.


Examples:

HPF_BUTTER 1 2 Fpass=2 Apass=6 TYPE=0 N=4 Touchstone Translation: None


Chebyshev Highpass Filter (HPF_CHEBY)

317

Chebyshev Highpass Filter (HPF_CHEBY)


Netlist syntax:

HPF_CHEBY n1 n2 Fpass= [Apass=] [AMAX=] [TYPE=] [IL=] N= R= [Z1=] [Z2=] [Name=]

Parameters:

Fpass Frequency of passband edge, in MHz. N Order of the filter. R Ripple, in dB. IL Insertion loss, in dB. Apass Attenuation at passband edge, in dB (default is ripple). AMAX Maximum attenuation in stopband, in dB (default is 100 dB). TYPE Input impedance in stopband, short = 0, open = 1 (default is open). Z1 Input impedance in ohms (default is 50 ohms). Z2 Output impedance in ohms (default is Z1).



Examples:

HPF_CHEBY 1 2 Fpass=2 Apass=6 TYPE=0 N=5 R=0.5 Touchstone Translation: None



318

Elliptic Highpass Filter (HPF_ELLIPTIC)


Netlist syntax:

HPF_ELLIPTIC n1 n2 Fpass= [AMAX=] [TYPE=] [IL=] N= R= Sbattn= [Z1=] [Z2=] [Name=]

Parameters:

Fpass Frequency of ripple passband edge, in MHz. N Order of the filter. R Ripple, in dB. IL Insertion loss, in dB. Sbattn Stopband attenuation, in dB. AMAX Maximum attenuation in stopband, in dB (default is 100 dB). TYPE Input impedance in stopband, short = 0, open = 1 (default is open). Z1 Input impedance in ohms (default is 50 ohms). Z2 Output impedance in ohms (default is Z1).


Note: The insertion loss must be greater or equal to zero. The filter order must be an integer greater or equal to 2. The frequency of the passband edge must be positive. The stopband attenuation must be greater than the ripple.

Examples:

HPF_ELLIPTIC 1 2 Fpass=2 TYPE=0 N=5 R=0.5 Sbattn=20 Touchstone Translation: None


Pole / Zero Highpass Filter (HPF_POLES)

319

Pole / Zero Highpass Filter (HPF_POLES)


Netlist syntax:

HPF_POLES n1 n2 Poles= Zeros= Fpass= Gain Factor= [AMAX=] [TYPE=] [IL=] [Z1=] [Z2=] [Name=]

Parameters:




Fpass Frequency at passband edge, in MHz.










The generalized pole/zero filter characteristic completely defined by the user. The specified poles and zeros define the low frequency prototype for the filter. Transformations are used as necessary for highpass, bandpass, and bandstop variants. The insertion loss only affects the forward (S21) and backward (S12) transmission, but not


320

the reflection coefficients (S11,S22). The input impedance in the stopband only affects the phase of the reflection coefficients.

Note: The insertion loss and maximum stopband attenuation must be greater or equal to zero. The frequency of the passband edge must be positive. The number of poles must be 1 or greater.

Examples:

HPF_BUTTER 1 2 Poles=complex(-0.7,0.7);complex(-0.7,-0.7) Zeros=complex(-1.0,0) Gain Factor=1.0

Fpass=2 AMAX=100 TYPE=0 Touchstone Translation: None


Bessel Lowpass Filter (LPF_BESSEL)

321

Bessel Lowpass Filter (LPF_BESSEL)


Netlist syntax:

LPF_BESSEL n1 n2 Fpass= [Apass=] [AMAX=] [TYPE=] [IL=] N= [Z1=] [Z2=] [Name=]

Parameters:

Fpass Frequency of passband edge, in MHz. Apass Attenuation at passband edge, in dB (default is 3 dB). AMAX Maximum attenuation in stopband, in dB (default is 100 dB). TYPE Input impedance in stopband, short = 0, open = 1 (default is open). IL Insertion loss, in dB. N Order of the filter. Z1 Input impedance in ohms (default is 50 ohms). Z2 Output impedance in ohms (default is Z1).



Examples:

LPF_BESSEL 1 2 Fpass=2 Apass=6 TYPE=0 N=4 Touchstone Translation: None



322

Butterworth Lowpass Filter (LPF_BUTTER)


Netlist syntax:

LPF_BUTTER n1 n2 Fpass= [Apass=] [AMAX=] [TYPE=] [IL=] N= [Z1=] [Z2=] [Name=]

Parameters:

Fpass Frequency of passband edge, in MHz.

Apass Attenuation at passband edge, in dB (default is 3 dB).



IL Insertion loss, in dB.

N Order of the filter.


Z2 Output impedance in ohms (default is Z1). The Butterworth filter characteristic is a maximally flat response in the passband generated by poles only. This results in no ripple in the passband, but a cutoff which is less sharp than some other filters. The insertion loss only affects the forward (S21) and backward (S12) transmission, but not the reflection coefficients (S11,S22). The input impedance in the stopband only affects the phase of the reflection coefficients. For additional details on filter types see the FILTER Synthesis Manual.


Examples:

LPF_BUTTER 1 2 Fpass=2 Apass=6 TYPE=0 N=4 Touchstone Translation: None


Chebyshev Lowpass Filter (LPF_CHEBY)

323

Chebyshev Lowpass Filter (LPF_CHEBY)


Netlist syntax:

LPF_CHEBY n1 n2 Fpass= [Apass=] [AMAX=] [TYPE=] [IL=] N= R= [Z1=] [Z2=] [Name=]

Parameters:

Fpass Frequency of passband edge, in MHz. Apass Attenuation at passband edge, in dB (default is ripple). AMAX Maximum attenuation in stopband, in dB (default is 100 dB). TYPE Input impedance in stopband, short = 0, open = 1 (default is open). IL Insertion loss, in dB. N Order of the filter. R Ripple, in dB. Z1 Input impedance in ohms (default is 50 ohms). Z2 Output impedance in ohms (default is Z1).



Examples:

LPF_CHEBY 1 2 Fpass=2 Apass=6 TYPE=0 N=5 R=0.5 Touchstone Translation: None



324

Elliptic Lowpass Filter (LPF_ELLIPTIC)


Netlist syntax:

LPF_ELLIPTIC n1 n2 Fpass= [AMAX=] [TYPE=] [IL=] N= R= Sbattn= [Z1=] [Z2=] [Name=]

Parameters:

Fpass Frequency of ripple passband edge, in MHz. AMAX Maximum attenuation in stopband, in dB (default is 100 dB). TYPE Input impedance in stopband, short = 0, open = 1 (default is open). IL Insertion loss, in dB. N Order of the filter. R Ripple, in dB. Sbattn Stopband attenuation, in dB. Z1 Input impedance in ohms (default is 50 ohms). Z2 Output impedance in ohms (default is Z1).


Note: The insertion loss must be greater or equal to zero. The filter order must be an integer greater or equal to 2. The frequency of the passband edge must be positive. The stopband attenuation must be greater than the ripple.

Examples:

LPF_ELLIPTIC 1 2 Fpass=2 TYPE=0 N=5 R=0.5 Sbattn=20 Touchstone Translation: None


Pole / Zero Lowpass Filter (LPF_POLES)

325

Pole / Zero Lowpass Filter (LPF_POLES)


Netlist syntax:

LPF_POLES n1 n2 Poles= Zeros= Fpass= Gain Factor= [AMAX=] [TYPE=] [IL=] [Z1=] [Z2=] [Name=]

Parameters:




Fpass Frequency at passband edge, in MHz.










The generalized pole/zero filter characteristic completely defined by the user. The specified poles and zeros define the low frequency prototype for the filter. Transformations are used as necessary for highpass, bandpass, and bandstop variants. The insertion loss only affects the forward (S21) and backward (S12) transmission, but not

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the reflection coefficients (S11,S22). The input impedance in the stopband only affects the phase of the reflection coefficients.

Note: The insertion loss and maximum stopband attenuation must be greater or equal to zero. The frequency of the passband edge must be positive. The number of poles must be 1 or greater.

Examples:

LPF_BUTTER 1 2 Poles=complex(-0.7,0.7);complex(-0.7,-0.7) Zeros=complex(-1.0,0) Gain Factor=1.0

Fpass=2 AMAX=100 TYPE=0 Touchstone Translation: None


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