oscillator design for manufacture page 1 of 17 applied wave research inc. 1960 east grand ave, el...

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Applied Wave Research Inc. 1960 East Grand Ave, EL Segundo, CA 90245 Tel +1 310-726-3000 Fax +1 310-726-3005

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Overview Microwave Office 2002 v5.00 incorporates state-of-the -art linear, non-linear and systems simulation technology under an intuitive Windows user interface that greatly increases the efficiency of designers. This application note describes how these capabilities are applied to the design and manufacture of a W-CDMA 2.3 GHz VCO. Using a design built and tested by an independent semi-conductor manufacturer, this note will demonstrate the ease with which Microwave Office can take this type of design from concept through to a complete manufacturing documentation pack, including mask generation. We will use linear, non-linear and non-linear noise analysis for this oscillator design. These capabilities will enable us to set up and check the required conditions for oscillation and allow the simulation of the oscillation frequency, output waveforms, output spectrum, noise spectrum and phase noise. A highly effective “tuning-mode” optimization and yield analysis allows rapid and automatic adjustment of a designated circuit parameter in order to meet the oscillation frequency specification. Highlights of the these new features are: ??Precise determination of the oscillation frequency under large-signal conditions ??Rigorous computation of the large -signal spectrum, including spurious harmonic products ??Rigorous phase noise analysis including bias dependence and the effects of flicker noise upconversion

The unique features and advanced tools in Microwave Office 2002 v5.00 greatly reduce the time required to complete a new design:

?? Intelligent Cells speed up the schematic design process removing the need for equations. ?? Sophisticated routing elements allow simple routing of RF and DC lines while retaining the required

theoretical design parameters. ?? EM-based models greatly improve the accuracy of the schematic design compared to today’s

standard equation-based models. These can also be Intelligent Cells. ?? XML-based component libraries can be used to design with real components including real parasitics

and physical attributes. The user can easily produce these libraries to replicate their current, complete , approved parts library. ?? The final complete layout can simply be copied into a 2.5D planar simulator to investigate potential

problems, such as cross coupling, and to analyse possible hotspots and/or breakdown areas. Once the initial design has been completed and analysed for yield optimisation, the integrated layout tool allows the finished design to be completed. Manufacturing documentation can be produced directly from the layout ensuring dimensioned drawings represent the original schematic design exactly. Board masks in GERBER (RS-274X), GDSII or DXF format are produced in one simple command, and Excellon Drill data can also be exported. A complete bill of materials can then be compiled, again from the same original schematic design. At no time are any of these tasks dissociated from the design, ensuring no details are missed.

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This application note will take you through the design flow, detailing the output one can expect in just a few hours work by using Microwave Office 2002 v5.00.

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Design Task

We will design a VCO based on an application note from Infineon. Application note No. 061: W-CDMA 2.3 GHz VCO using BFR360F and BBY58 -02V

…This application note (No. 061) describes a VCO design for W-CDMA applications. The

circuit offers a low phase noise of less than –90 dBc/Hz @ 10 kHz despite the fact that a standard, low-cost, low Q chip inductor is used as the resonator circuit. Of course, one cannot expect this VCO design to have a tightly toleranced, highly repeatable frequency of oscillation since the tolerance of the inductor used in the tank circuit is +/- 0.3 nH which corresponds to +/- 20 % of the nominal 1.5 nH value. The main purpose of this application note was not to present an oscillator suitable for mass production, but to point out the excellent potential of the BFR360F transistor for low-cost, low phase noise VCOs.

Supply Voltage 3V Supply Current 8.5 mA Control Voltage Range 0.85 to 2 V

Operating Frequency 2300 to 2360 MHz Output Power 0 dBm Harmonics < -13 dBc

Methodology

Circuit Theory Theory suggests a suitable oscillator configuration – let’s start with a Clapp Common Collector design (figure 1). Using a real device, we need to calculate the DC bias conditions.

Figure 1: Common Collector Design

C

B

E

1

2

3C1

C2

Rbias

Cb

RL

Lt

Cv

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Using the Gummel Poon model parameters provided by the manufacturer (Infineon) found directly from the Microwave Office non-linear device library (figure 2) , the IV curves of the device can be plotted (figure 3).

Swp Step

ISTEP_step=ISTEP_stop=ISTEP_start=

VSWEEP_step=VSWEEP_stop=VSWEEP_start=

ID=

.05 mA

.2 mA0 mA.1 V6 V0 VIV1

C

B

E

1

2

3

NET=ID=

"BFR360F" S1

Figure 2: Device Library Figure 3: DC IV curves

The bias configuration requires knowledge of Vbe vs. Ic (figure 4). From the simulated plots and Vcc=3 V, we need Vce=2.55 V. The following bias network was created to satisfy these conditions (figure 5).

Figure 4: Vbe vs Ic Figure 5: Bias Network The measured current is Icq=9.7mA at Vce=2.47V. This fundamental work can all be undertaken at the ideal schematic level. The next step is to determine the feedback necessary to create a negative resistance network. Theory on this step can be provided. This now forms our negative resistance source, to which we match a real tank circuit. The resonant frequency is that defined by the tank circuit at the point

0 2 4 6Voltage (V)

IV curve

- 5

0

5

10

15

20

25IVCurve (mA)ivcurve

R=ID=

2.2e+004 OhmR1

R =ID=

51 OhmR2

V=ID=

3 VV1

L=ID=

80.5 nHL1

L=ID=

80.5 nHL2

ID= VM1

ID= AMP1 C

B

E

1

2

3

NET=ID=

"BFR360F" S1

DLI Dicap D30 330pF

VStep=VStop=VStart=

ID=

.01 V1 V0 VV1

ID=AMP1

C

B

E

1

2

3

NET=ID=

"BFR360F" S1


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where the reactance cancels with that of the negative resistance source. The OSCTEST element should be used to break the feedback loop to ensure these fundamental conditions are met. Real World Design Taking this ideal design into the real world, practical components can be added to provide real interconnects and real component models for those ideal devices. Components are replaced with those from the XML based library, and will now model specific parasitics for a given ideal element, along with exact package outline and footprint (figure 6).

BFR360F

IND

L=ID=

0.657 nHL1

IND

L=ID=

0.556 nHL2

IND

L=ID=

0.381 nHL3

CAP

C=ID=

4.3e-002 pFC1

CAP

C=ID=

6.6e-002 pFC2

CAP

C=ID=

0.123 pFC3

CAP

C=ID=

1.e-002 pFC4

CAP

C=ID=

4.7e-002 pFC5

CAP

C=ID=

3.6e-002 pFC6 S

C

B

E

1

2

3

4

GBJTID= GP_BFR360_1

PORT

Z=P=

50 Ohm1

PORT

Z=P=

50 Ohm2

PORT

Z=P=

50 Ohm3

Figure 6: XML Library

Routing Microstrip line models are added to route the connections around the board as required by the schematic design and EM-based Intelligent Cells replace the discontinuities and are used to proved more accurate models for the discontinuity and ensure line widths agree at junctions without any further input from the designer (figure 7).

1 3

2


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MSUB

Name=ErNom=

Tand=Rho=

T=H=

Er=

RO/RO4350B1 3.48 0.004 0.7 1.7e-002 mm0.508 mm3.48

MLIN

L=W =ID=

0.35 mm0.5 mmTL1

1

2

3

4

MCROSSX$ID=MX1

MTRACE

M=BType=

L=W=ID=

0.6 2 1.903 mmwtrace mmX1

MLIN

L=W=ID=

0 mmwtrace mmTL2

MLIN

L=W =ID=

0.1 mm0.5 mmTL3

MULTCAP

Temp=Orient=

DiCode=Size=

C =ID=

27 DegC0 1 6 0.7 pFC1

RES

R =ID=

24000 OhmR1

MSTEPX$

Offset=ID=

0 mmMS1

wtrace=.6

Figure 7: Unique Features

Once the automatic electrical layout generated from the schematic diagram is complete, surrounding board constraints can be added such as ground plane and vias along with mounting holes if required. The practical design is now complete (figure 8).

MSUB

N a m e =

ErNom=Tand=

Rho=

T =H =

E r =

RO/RO4350B1

3 .48 0 . 0 0 4

0.7

1.7e-002 mm0.508 mm3.48

MLIN

L =

W =I D =

0.35 mm

0 . 5 m mTL1

MLIN

L=

W=ID=

0 . 3 5 m m

0.5 mmTL2

MLIN

L =W =

I D =

0.35 mm0 . 6 m m

TL3

M S T E P X $

Offset=I D =

0 mmMS1

MLIN

L =W =I D =

0.15 mmw t r a c e m mTL4

1

2

3

4

MCROSSX$ID= MX1

MLIN

L=W=

ID=

0.25 mmwtrace mm

TL5

MLIN

L =

W =

I D =

0.2 mm

wt race mm

T L 6

MTRACE

M=

BType=L =

W=ID=

0.6

2 1.902 mm

w t r a c e m mX1

1

2

3

4

MCROSSX$ID=MX2

MTRACE

M=BType=

L=W=

ID=

0.6 2

1.903 mmwtrace mm

X2 MLIN

L =

W =

I D =

0 mm

w t r a c e m m

TL7

MLIN

L=W=

ID=

0.1 mm0.5 mm

TL8

12

3

M T E E X $ID=M T 1

MLIN

L=

W=

ID=

0 mm

w t r a c e m m

TL9 MLIN

L=

W=

ID=

0.3 mm

wtrace mm

TL10

MULTCAP

T e m p =

Orient=D i C o d e =

S i z e =

C =

I D =

2 7 D e g C

0 1 6

0 . 7 p F

C 1

12

3

M T E E X $I D =M T 2

MLIN

L=

W=

ID=

0.41 mm

w t r a c e m m

TL11

M L I N

L =

W =

I D =

0.4 mm

wtrace mm

T L 1 2

12

3

M T E E X $I D = M T 3

MLIN

L=

W=

ID=

0 . 4 1 m m

wtrace mm

TL13

MLIN

L =

W =

I D =

0 . 3 m m

w t r a c e m m

TL14

MULTCAP

Temp=

Orient=DiCode=

S i z e =

C =

ID=

27 DegC

0 1 6

1.8 pF

C2

MULTCAP

T e m p =

Orient=

D i C o d e =S i z e =

C =

I D =

2 5 D e g C

0

1 6 0 . 7 p F

C 3

MLIN

L=

W=ID=

0.4 mm

w t r a c e m mTL15

CCIND

K =

L =C =

R 2 =R 1 =

I D =

0.000165

8 0 . 5 n H6.3e-002 pF

1.e-002 Ohm2 5 O h m

L 1

MTRACE

M=

BType=L=

W=

ID=

0.6

2 1 . 2 3 1 m m

wtrace mm

X3

R E S

R=

ID=

51 Ohm

R1

MLIN

L=W=

ID=

0 m mwtrace mm

TL16

MULTCAP

T e m p =

Orient=


C =I D =

25 DegC

0

1 6

0 . 6 p FC 4

MLIN

L=W=

ID=

0.2 mmwtrace mm

TL17

1

2

3

4

MCROSSX$ID=MX3

MLIN

L=W=

ID=

0.2 mmwtrace mm

TL18

M L I N

L =

W=ID=

0.4 mm

wtrace mmTL19

M L I N

L =

W =

I D =

0.2 mm

wtrace mm

T L 2 0

M U L T C A P

Temp=Or ient=

D i C o d e =

S i z e =C =

ID=

25 DegC0

1

6 0 . 6 p F

C 5

C C I N D

K =

L =C =

R 2 =

R 1 =

I D =

0.000165

8 0 . 5 n H6 . 3 e - 0 0 2 p F1.e-002 Ohm

2 5 O h m

L 2

MLIN

L =

W=ID=

0.7 mm

wtrace mmTL21

CCIND

K =L =

C =

R 2 =R 1 =

ID=

1 .38e -005 3.5 nH

5 .e -002 pF

1.e-003 Ohm1 Ohm

L 3

M L I N

L =

W =I D =

0.2 mm

wtrace mmT L 2 2

MLIN

L=W=

ID=

0.2 mmwtrace mm

TL23

1

2

3

4

MCROSSX$ID=MX4

MLIN

L=

W=

ID=

0.2 mm

wtrace mm

TL24

M L I N

L =

W=ID=

0.2 mm

wtrace mmTL25

M L I N

L =

W =I D =

0.21 mm

wtrace mmT L 2 6

MULTCAP

Temp=Or ient=D i C o d e =

S i z e =

C =ID=

25 DegC0 1

17

330 pFC 6

RES

R =

I D =

24000 Ohm

R 2

MULTCAP

T e m p =

Orient=


C =

I D =

2 5 D e g C

0

2 1 1 1.5 pF

C 7

1

2

3M T E E X $

I D =M T 4

MLIN

L =W =I D =

0.2 mmwt race mmTL27

M L I N

L =W=

ID=

0.25 mmwtrace mm

TL28

MULTCAP

T e m p =

Orient=D i C o d e =

S i z e =

C =

I D =

2 5 D e g C

0 1 1 7

3 3 0 p F

C 8

C C I N D

K =

L =

C =R2=R1=

ID=

0.000165

80.5 nH

6 . 3 e - 0 0 2 p F1.e-002 Ohm25 Ohm

L4

MLIN

L =W =

I D =

0.375 mmwt race mm

TL29

M U L T C A P

Temp=Orient=D i C o d e =

S i z e =

C =ID=

25 DegC0 2

11

3 p FC9

MLIN

L=

W=

ID=

0.85 mm

w t r a c e m m

TL30

DCVS

V =

I D =

3 V

V 1

A

OSCAPROBE

Vsteps=Fsteps=

Fend=Fs ta r t=

ID=

20 200

2 .6 GHz2 GHz

X 4

DCVSS

VStep=VStop=

VStart=

ID=

.5 V3 V

0 V

V2

MLIN

L=

W=

ID=

0 . 2 5 m m

wtrace mm

TL31

M S T E P X $

O f f s e t =

I D =

0 mm

MS2

MLSC

L =

W=

ID=

0 m m

wtrace mm

TL32

MLSC

L=W=

ID=

0 mmwtrace mm

TL33

MLSC

L=

W=

ID=

0 m m

wtrace mm

TL34

C

B

E

1

2

3

S U B C K T

N E T =

ID=

"BFR360F"

S1

S U B C K T

NET=

ID=

"varactor"

S2

PORT

Z=

P=

50 Ohm

1

wtrace=.6

This schematic is for oscillator frequency analysis

Oscillator probe element to determine oscillation frequency.Fstart and Fend bound the frequency search of the probeFsteps is the frequency steps between Fstart and Fend to find the oscillation condition

using a swept voltage source on the varactor


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Figure 8: Completed Design

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0 1.0

-0.5

-2.0

-3.0

1.0

-1.0

2.0

-2.0

0.2

-0.2

0.5

0.5

-0.5

-0.5

Neg Res and Tank circuitSwp Max

3GHz

Swp Min

2GHz

S[1,1]Tank circuit layout

S[2,2]VCO linear

0 1.0

1.0

-1.0

10.0

10.0

-10.0

5.0

5.0

-5.0

2.0

2.0

-2.0

3.0

3.0

-3.0

4.0

4.0

-4.0

0.2

0.2

-0.2

0.4

0.4

-0.4

0.6

0.6

-0.6

0.8

0.8

-0.8

Output MatchSwp Max

3V

Swp Min0V

LSSnm[PORT_1,PORT_1,1,1,1]VCO Layout Vtune

Simulation Results vs. Measured Data

Simulation data can be plotted in numerous ways, including data tables, and also exported as S-parameter files (figure 9).

!freq-unit par-type data-frmt kywrd imp # GHZ S MA R 50 !-------------------------------------------------- !Freq MagS11 AngS11 2 0.64757 -155.64 2.1 0.93927 -159.43 2.2 1.5865 -144.17 2.3 1.6626 -84.158 2.4 0.91622 -55.395 2.5 0.58388 -48.915 2.6 0.48929 -42.023 2.7 0.46801 -38.559 2.8 0.51625 -39.601 2.9 0.42039 -40.48 3 0.48321 -40.828

Frequency (GHz) DB(PH_NOISE[1,1]) VCO Layout Phase Noise 1e-006 -68.32 2.1544e-006 -74.599 4.6416e-006 -82.137 1e-005 -89.574 2.1544e-005 -96.298 … …..

Figure 9 : Simulation Results

0 4 8 12 16Frequency (GHz)

Spectrum Analyzer

-80

-60

-40

-20

0

20

2.3966 GHz -19.48 dBm delta

2.3966 GHz 2.5629 dBm ref Spectral Output at 2V (dBm)

VCO Layout Vtune

0 0.6 1.2 1.8 2.4 3Voltage (V)

Frequency vs Vtune

2.2

2.25

2.3

2.35

2.4

2.45

2.5

OSC_FREQ (GHz)VCO Layout Vtune

0 1 2 3Voltage (V)

Pout vs Vtune

-8

-6

-4

-2

0

2

4

6

DB(|Pcomp[PORT_1,1,1]|) (dBm)VCO Layout Vtune

1e-006 1e-005 .0001 .001Frequency (GHz)

phase noise

-140

-130

-120

-110

-100

-90

-80

-70

-60

DB(PH_NOISE[1,1])VCO Layout Phase Noise


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Compared to measured data (screen shots taken from Infineon Application Note No. 061), these results are very convincing (figure 10).

Figure 10 : Simulation Results Vs. Measured Data

0 0.5 1 1.5 2 2.5 3Voltage (V)

Pout vs Vtune

-8

-6

-4

-2

0

2

4

6

DB(|Pcomp[PORT_1,1,1]|) (dBm)VCO Layout Vtune

0 0.5 1 1.5 2 2.5 3Voltage (V)

Frequency vs Vtune

2.2

2.25

2.3

2.35

2.4

2.45

2.5

OSC_FREQ (GHz)VCO Layout Vtune

1e-006 1e-005 .0001 .001Frequency (GHz)

phase noise

-140

-130

-120

-110

-100

-90

-80

-70

-60

DB(PH_NOISE[1,1])VCO Layout Phase Noise


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The dynamic tuner can be used interactively in real-time to adjust element parameters, such as the feedback resistor (figure 11) , and to see the immediate effect on the schematic simulation results and the layout if track routing or size is adjusted.

Figure 11.

Finally, these changes can be performed automatically using the Artificial Intelligent Optimizer that actually learns the quickest route to the best solution for a given schematic topology using some of the 10 different optimiser methods. The goals can come from the design specification - optimiser goals (figure 12) or from yield requirements given toleranced components and a required yield.

Figure 12.


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Design Documentation & Manufacturing Artwork All schematic and layout views can easily be cut and pasted into a document editor to produce the complete design history. This is exactly how this application note has been produced. Extra dimension information can also be added to the layout, snapped exactly to the any of the features such as the tracks produced by the schematic (figure 13). This is an accurate way to define critical dimensions and/or for quality screening to ensure that the board has been manufactured correctly.

1.00 mm +/- 0.01

0.600 mm +/- 0.010

0.60

0 m

m +

/- 0.

010

2.77

0 m

m +

/- 0.

010

0.600 mm +/- 0.010

Figure13: Critical Dimensions

Gerber (figure 14) and GDSII (figure 15) masks and Excellon drill file data (figure 16) can be easily produced from Microwave Office 2002.

04 Microwave Office 5.0* G04 RS274-X Output Version 0.1 * %FSLAX36Y36*% %MOMM*% %SFA1B1*% G36* X-10416000 Y-2143000D02*

Y-2493000D01* X-9916000D01* Y-2143000D01* X-10416000D01* G37* G36* X-11516000Y-2143000D02* Y-2493000D01*

… …

Figure 14 : GERBER data and mask


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! Excellon Drill Data M48 M71, LZ T01C0.500 % T01 X-013326Y-001364 X-012906Y-006014 X-012896Y-004414 X-012036Y001346 X-009646Y-006103 X-009306Y-000693 X-009136Y001727 X-009026Y000507 X-007496Y-004503 X-007016Y001947 X-006616Y000807 X-006546Y-000403 T00 M30

… Figure 15: GDSII Mask Figure 16: Excellon Data File

Running a simple Visual Basic Script embedded into Microwave Office 2002, a complete parts list can be generated for the whole project, broken down into each schematic design (figure 17).

Figure 17 : Parts List extracted from Schematics


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Summary Microwave Office 2002 v5.00 incorporates state-of-the-art linear, non-linear and systems simulation technology under an intuitive windows user interface that greatly increases the efficiency of designers. Using these, along with the advanced tools and unique features of Microwave Office, we have taken a design task to finished manufacturing documentation and bill of materials. Oscillator design starts with theoretical circuits used for bias and component selection. Converting these into a practical design using company-approved parts is straightforward. Simulation results can be optimized taking into account parasitic strays and component tolerance information. Layout decisions are made while retaining the dynamic link to the simulated schematic design. Manufacturing information can easily be exported, including detailed parts lists or bill of materials, from the same single schematic design. Errors made by switching between individual tools, or conversions , are completely removed. Overleaf is a screen capture of the example design, based on the Infineon Application Note No. 061 for a W-CDMA 2.3 GHZ VCO using a BFR360F device. The simulation results very closely match the measured data.

Acknowledgements Andrew Wallace and AWR would like to acknowledge and thank Infineon for their permission to use the Application note No. 061 example in this application note.

Andrew Wallace – Technical Applications Engineer AWR Inc., 7 Paynes Park, Hitchin, HERTS SG5 1EH

Email: [email protected] Phone: +44 7753 692663


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Appendix 1 - Fundamentals of Oscillator Analysis in Microwave Office 2002 Oscillator Analysis in the Frequency Domain Generally speaking, oscillators may be analyzed either in the frequency domain by means of non-linear harmonic balance simulators or in the time domain by means of SPICE and its derivatives. Microwave Office takes the harmonic balance (frequency domain) approach with several important advantages: ??The steady-state is computed directly, avoiding the costly and potentially inaccurate time-

integration through transients. ??Using a steady state solution, optimisation, tuning and yeild analysis are possible. ??Frequency domain analysis accommodates multiport parameter descriptions of distributed

elements in a more natural way, resulting in highly accurate simulations that are compatible with measured or EM-simulated S-parameter data.

Microwave Office 2002 v5.00 analyzes oscillators based on a form of the Kurokawa oscillation condition. While frequency domain analysis is the de facto method of choice for the analysis of oscillators, particularly those that operate at high frequencies, oscillators present a rather serious challenge in the area of simulation technology. These difficulties stem from the mathematical implications, in high-Q circuits especially, of the lack of a priori knowledge of the fundamental oscillation frequency. To address these challenges Microwave Office resorts to a special device called the “oscillator probe” which eases these difficulties and allows for fast and robust oscillator simulations, even in cases of extremely high resonator Q. The Oscillator Probe Consider an oscillator in steady state operation. For the purposes of illustration, a highly simpli fied schematic of such a circuit is shown in figure A1.

Figure A1: Simplified Ocsillator Schematic Figure A2: Introduction of Voltage source


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Suppose that a sinusoidal voltage source of amplitude and frequency is applied to the oscillator at the node denoted by X in figure A2. The source impedance is given by :

0 ? = ? p

Z(? ) = ? ? ? ? p

Hence it is a short circuit at the source frequency and an open circuit elsewhere. The combination of the source and the impedance element, marked in figure A2, is referred to as the oscillator probe. Now, suppose that the probe voltage is equal in amplitude and phase to the steady state operating voltage at node X. Under those circumstances, no current flows through the probe at ? p. By definition of the probe impedance, no current flows through the probe at any other harmonic of ? p. This discussion leads to the conclusion that the problem of solving for an oscillator’s steady-state operation may be stated as follows: ??Connect the oscillator probe at a suitable node in the circuit. ??Find the source amplitude and frequency that results in zero current flow through the probe.

In this manner, oscillator analysis is reduced to standard non-linear harmonic balance analysis running in the inner loop of a routine that attempts to locate probe parameters (amplitude and frequency) that result in zero current flow through its terminals. This outlined procedure is the basis for oscillator simulation in the Microwave Office design environment. By means of sophisticated algorithms, Microwave Office 2002 varies the probe frequency and voltage to rapidly descend from the approximate to the exact solution. Exact computation of the oscillatory steady-state is crucial to obtaining accurate noise predictions. Appendix 2 - Performing Oscillator Simulations Probe Parameters The oscillator probe (figure A3) may be found in the “Element” browser.

Figure A3: OSCAPROBE Figure A4: Tunable OSCTPROBE Figure A5: Noise Analysis

AOSCAPROBE

Vsteps=Fsteps=

Fend=Fstart=

ID=

20 200 2.6 GHz2 GHzX4

TOSCTPROBE

Par=Freq=

ID=

COAX.CX1.L 1.4 GHzX1

OSCNOISE

SwpType=OFsteps=

OFend=OFstart=

ID=

LOG10 .001 GHz1.e-006 GHzNS1


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Oscillator simulation takes effect when the following conditions are satisfied: ??The probe is connected to the oscillator circuit. ??Any measurement in the “Nonlinear” category or the OSC_FREQ (Oscillation Frequency)

measurement in the “Oscillator” category is defined. As usual in the case of negative resistance oscillators, we think of the active device as a negative resistance one-port connected in parallel with the resonator. The amplitude of oscillations builds up as long as the oscillations are sufficiently small and the active device exhibits negative resis tance. When the amplitude of oscillation grows beyond a certain point, the negative resistance of the device saturates and the circuit reaches steady-state oscillation. Subsequent to the detection of start-up frequency, the simulator switches to a mode whereby it effectively monitors the mentioned saturation of negative resistance, seeking the point where the real part of device impedance changes its sign. The point where the impedance changes its sign, it turns out, is an excellent initial guess for the final, rigorous analysis stage.

Harmonic Balance Parameters Standard non-linear harmonic balance simulation runs in the inner loop of oscillator analysis. For this reason, harmonic balance parameters apply as usual, controlling the number of harmonics and simulation accuracy. Default settings are appropriate in most circumstances. Due to peculiarities of oscillator analysis, it is recommended to leave the relative tolerance at default 1e-7 and the absolute tolerance at 1e -9. The user may adjust the number of harmonics to suit the application, although 5 should suffice in a large majority of cases. There is a single button that can be used to choose these default values.

Probe Connection In negative resistance oscillators, the probe should be connected between the resonator and the negative resistance-generating active device. In feedback oscillators, the probe should be connected to one of the nodes belonging to the feedback loop.

Tuning Probe Rather than simply predicting the frequency of oscillation using the OCSAPROBE, the tuning mode enforces the desired frequency by varying a designated circuit parameter (e.g. varactor bias or COAX length). Although existing optimization capabilities may be used for the same purpose, the tuning-mode exploits the mathematics of oscillator tuning directly and, in doing so, significantly out performs straightforward optimization. The new oscillator tuning element, OSCTPROBE, (figure A4) replaces the OCSAPROBE element. The simple user interface includes the frequency specification and the variable parameter identifier.

Noise Analysis Microwave Office 2002 v5.00 includes a full set of noise analysis features. Following accurate computation of the large-signal steady-state, designers may examine oscillators for phase noise, amplitude noise, total noise power, etc. Noise analysis is activated by dropping the noise element OSCNOISE (figure A5) onto the schematic and by specifying the desired simulation parameters such as the offset frequency range, number of sweep points and sweep type.

oscillator design for manufacture page 1 of 17 applied wave research inc. 1960 east grand ave, el...

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