momentum part2

Designing with Momentum

Review the design of a patch antennaDraw the antenna layoutExamine and use different layer and mesh settingsCreate a multi-layer substrate layer definitionDefine a via to feed the antennaPlot the far field radiation pattern

VIA FED to center of PATCHResonating Frequency : 3.8GHzLayout Physical Area : <1 square inchSubstrate : 25 mil alumina : Er=10Feedline at 12.5 mil

Calculate the geometry

Far Field Radiation Pattern

"5.001248.01098.32

83

2m

e

e

rf

CLength

L=500 mil

250

ADS Data Display used to calculate the values

Where

C=speed of light in meters

Conversion of length_meters/2.5e-2 is approximate

Also, W (width) will be ? of length

Half wavelength

radiation ..

3D view of design

Air

Alumina12.5

Alumina 12.5

Ground

cond=striphole=via

cond2=strip

cond=strip

hole=via

cond2=strip

Signal Feed on cond2 drawing layer : microstrip 25 mils wide Via on hole layer is drawn as a sheet of metal : 0 width

Drawing the patch ..

Active default entry layer : cond

Coordinate Entry draws the shape at exact X-Y coordinates

Select the type of shape : Rectangle

Next, vias .

1 2 3

1. Polygon should NOT be used.

2. Rectangle or square is OK.

3.polyline is recommended for Momentum solutions because current is modeled as traveling on one vertical sheet of metal.

Vias must be mapped through each individual substrate layer they pass through.

Next, how to draw vias

Enable snappin and Edge Snap

1. Select the drawing layer and snapping mode

2. Select the polyline command

Feedline

Via 3. Click to draw the viaZoom in and click on the first point and then double-click to finish the polyline command

Next, Ports .

Patch Antenna

Select the drawing layer and snap modes. Click the port icon and insert the port. Then select : Momentum > Port Editor and set the type.

Reference line drawn after selecting the port and type : Single (also the default if none is select)

To name substrate definitions, use : Save Asand the dialog entries are saved.

To add substrate layers, name them, and Add. You can also modify existing layers.

After defining the substrate layers, map the Metallization Layers

Result : cond2 is mapped as a strip

Mapping cond2 as a Strip above Alumina_2 :

Click on the Substrate Layer : --

Select the Layout Layer : cond2

Set the type : Sheet Conductor

Click : Strip

Result : Hole layer is mapped as a via through Alumina

Mapping hole as a Via through Alumina :

Click on the Substrate Layer : Alumina

Select the Layout Layer : hole

Click : Via

Example : patch and feedline have separate layer meshes!

Use the Global tab for setting frequency

Use Layer tab for setting Number of cells and Edge Mesh

Precedence : If two or more drawing layers overlap on the same substrate layer, one of the metals overlapping must take precedence (highest value). Default is arbitrary decided by mesh engine (no error reported)

Thin Layer Overlap : If two drawing layers are separated by a thin substrate layer, then mesh cells that overlap may cause incorrect answers. Thin layer extraction prevents this from happening

Global Mesh

Precedence =0 Precedence =1

Substrate Setup

Simulation setup is the same with or without vias. Results of the antenna simulation show resonance is approximately 3.8GHz.

1. Select the Sweep Type and the frequency range.

2. Click on Add to Frequency Plan List

3. Click on apply then on Simulate

AFS data point (trace) are calculated from the simulated possible 25 sample points (circles).

Next, AFS

AFS : Adaptive Frequency Sampling

- a method of comparing sampled S-parameter data points to a rational

fitting model.

- When the fitting model and the sampled data converge, the AFS

algorithm is the complete and the S-parameter data is written into the

dataset.

Take a design named filter as an example :

- filter : the ADS schematic simulation of the filter

- filter_mom : the Momentum results.

- filter_mom_a : the Momentum Adaptive results.

- filter_opt : the optimized results.

- filter_opt_a : the optimized Adaptive results.

freq Independent frequency variable

GAMMAn Modal propagation constant of port n (calculated for single,

differential, and coplanar ports only)

PORTZn Impedance of Port n

S S-matrix, normalized to PORTZn

S(I, j) S-parameters for each port pairing, normalized to PORTZnS_50 S-matrix, normalized to 50 ohms

S_50(i, j) S-parameters for each port pairing, normalized to 50 ohms

S_Z0 S-matrix, normalized to Z0

S_Z0(I, j) S-parameters for each port pairing, normalized to Z0 of each port

Z0n Characteristic impedance of Port n (calculated for single,

differential, and coplanar ports only, others are 50 ohms)(Note that these are included in the datasets for Momentum simulations but not for MomentumRF)

All standard dataset variables, plus

S_CONV Boolean results for AFS convergence (success=1, fail=0) of

the entire S-matrix at a given frequency

S_CONV(I, j) Boolean results for AFS convergence (success=1, fail=0) of

S(i, j) at a given frequency

S_ERROR Estimated error of the entire S-matrix at a given frequency

(< -60 dB for converged frequency points)

S_ERROR(I, j) Estimated error of S(i, j) at a given frequency (< -60 dB for

converged frequency points)

Next, post processing

Add specific frequency points.

For example, do this to view antenna patterns or currents at a particular frequency.

This example will reuse the existing data and only simulate at 3.859 GHz

Far field pattern

Exact frequency from simulation data can be specified.

Select the desired frequency, type, and port :

Visualization window opens. You specify the View, E field type, and scale. These steps are described in the lab exercise!

Far Field shows the direction of radiation and relative strength.

Note, you can rotate the structure!

Lab 1 : Momentum Basics : Microstrip Meander Line

Lab 2 : Momentum RF Mode : RFIC Launch

Lab 3 : Designing with Momentum : Via-fed Patch Antenna

Lab 4 : Momentum Techniques : 3 dB Splitter

You are here

Draw the patch, feedline, and via

Setup the substrate and layer mapping

Precompute the substrate

Mesh separate layers differently

100, 125

600, -125

Coordinate Entry

Map Strip and Via

Setup and run the AFS simulation

Plot the resonant response

Reuse files and simulate at resonant freq

Plot the far field pattern

OPTIONAL steps available

Momentum Techniques

Understand Thick Conductor settingUtilize different Momentum port typesMesh curved structures efficientlyControl various layout settingsADS schematic simulation with layout look-alike component

Embed a Thin Film Resistor for simulation

First, Thick Conductor information ..

Use it when the Width/Height ratio > a factor of 5.You can still specify metal as: perfect conductor, impedance (Z), or with conductivity (sigma ).Does Visualization can still be used.Increases the simulation time

NOTE: Thickness and conductivity values are still used for calculating metal loss with Thick Conductor.

More

h2

h1,t[1]

[2]

1 layer sheet conductor

2 substrate layers

1 metal strip layer

Thick Conductor=Up

USER Setting

[1]

[2] h2

h1

t

2 layer conductor with sides

3 substrate layers

2 strip layers + 1 via layer

Momentum Engine

3-D Metal expansion

Surface impedance model based on coupled skin effect model.

Mutual internal coupling of surface currents is also included.An example

ADS schematic components generated into layout, resulting in a structure solved in Momentum with expected results:

TECHNIQUES REQUIRED:

Mesh-arbitrary geometry with curves.

Ports-different port types (single & internal).

Creating a look-alike component for ADS simulator.

Microstrip artwork generated into layout for solution in Momentum. First, meshing curved

structures .

Simulation time is directly proportional to Mesh density but NOT directly proportional to accuracy. Experience will help determine the trade-off between simulation time and accuracy

Next, port type

45 degrees: 10 cell/ 20 degrees: 20 cell/ 5 degrees: 30 cell/

I

P1 P2

P3P5

P4

P5

P4

Single port is calibrated:

1/2 extension at port boundary for all simulation frequencies

Exploded view ports 4 &5

No room for single port calibration extension.

Calibration extension.

Port 1,2,3 are Single. But ports 4 and 5 are too close back-to-back for Momentum port calibration. The half-wavelength extension would overlap the geometry. Therefore, ports 4 and 5 must become Internal ports!

Next, internal port extension

Define the port as internal. Then place the port at any point on the metal surface.

Momentum automatically recognizes internal ports

At Momentum simulation time, the single ports (default) are converted to Internal ports, if they cannot be calibrated.

When this happens, a warning message appears.

Next, simulation

Sweep from 1 to 10GHz: Simulation result show about 6dB loss for splitter at ports 2 and 3.

The structure will become a 3dB splitter after ports 4 and 5 have a resistor connected between them.

All five port impedances set to 50 ohms (default for single and internal ports).

Next, using Momentum data in an ADS circuit simulation

Dataset assigned to an SNP: Layout look-alike component:2 different ways to do it!

SNP is a block-box and requires a Touchstone, CITIFILE or dataset. You set everything up!

Look-alike is a scaled version of the layout drawing. It is created in Momentum and available in the ADS library. It can also be parameterized.

Creating a look-alike layout component

Symbol: a scaled copy of the layout shape is created. Set min or max pin-pin distance, or layout units.Model: these parameters will be available in schematic. They are a subset of the Momentum simulation setup.

*modelDB: this is where the Momentum solution data is stored as file (after simulation)..

Create/Update dialog=set up the look-alike.

*modelDB:

Click OK and the entries will be passes to the look-alike.

Next, insert the look-alike

Be sure to check this box to have the file created form the last Momentum simulation!

Ref: The reference pin is created as a voltage reference for all the other pins of the componentConnect the Ref to ground or use to simulate floating ground.

Also, push/pop if schematic exists!

Component dialog=view or set up the Momentum simulation model. Parameters tab is for parameterizing the component.

Double click:

Simulation in schematic

Use any other ADS simulator: DC, AC, HB, Transient, etc.

If not checked when creating the component, it is automatically connected to ground but does not appear.

Or, use an SNP

S-Parameter N-portis a file based component that allows S-parameter data to be simulated.

To begin, set up the SNP

Next, Simulation

Lab

S5P File=mom dataset

S-parameter circuit simulator requires Terms (ports).

TFR is a standard ADS microstrip component.

3dB insertion loss at 6GHz for ports 2 and 3 with very good isolation. Output Z is about 50 Ohms.

Lab 1 : Momentum Basics : Microstrip Meander Line

Lab 2 : Momentum RF Mode : RFIC Launch

Lab 3 : Designing with Momentum : Via-fed Patch Antenna

Lab 4 : Momentum Techniques : 3 dB Splitter

You are here

Here is an overview

Open the splitter microstrip designVerify schematic component mapping to layout layersChange Momentum port arrow attributesVerify the internal portsModify layout layer settings and textCreate a look-alike componentSimulate the splitter from schematic

Generate the layout.

Try 3 different meshes for curves.

Internal ports

Set preference and layer settings for ports, text, and drawing layers:

Schematic with layout look-alike component for simulation:

Create the look-alike, simulation from schematic, plot the results, check the database.

DESIGN: splitter wtfr-generated into layout for simulation:

Layout drawing layers cond (splitter) and resi (TFR) are both mapped to the same substrate layer: Alumina.

Embedded layout TFR on RESI layer has conductivity set (50 ohms/sq).

Momentum results show a better match (Z=50 ohms) vs circuit simulator

Procedure: Via Fed Patch Antenna

The antenna is fed with microstrip and a via from below the patch surface. The result are close to the design goal. You will create the antenna from scratch the design is not provided in the example files.

Top view of the patch antenna mesh.

Antenna Resonance at about 3.8GHz

1. Draw the Patch geometry with Coordinate Entry

a. Before beginning, be sure to turn off (disable) the RF mode if it is on.

b. Open a new layout window from the ADS Main Window and save it

with the design name: patch

c. Be sure the entry drawing layer is cond (default). Click: Insert > Coordinate Entry

and the dialog will appear.

d. Click on the Insert Rectangle icon as the drawing shape.

Insert Rectangle

NOTE: Tour layout background color may be black.

e. Enter the coordinates (diagonal corners) in the dialog: x=100, y=125 and

click Apply. Then x=600, y=-125 and click Apply.

f. Click Option > Layers. Change the shape display for cond from filled to outline.

This will outline the geometry instead of filling it.

2. Draw the microstrip feed on another layer

a. Make sure that Coordinate Entry is still active before starting the next geometry.

Change the drawing layer to cond2. This will be the layer that is used for the feedline.

b. Select the rectangle icon to draw a Rectangle using coordinate entry. Then enter the

coordinates of the two diagonal corners: x=0, y=5 and x=320, y=-5 as shown here.

0,5

320,-5

Entry layer changed to cond2.

Toggle Vertex Snap Mode

3. Draw the Via

a. Set the entry drawing layer to hole (1). In general, there is no significance to the

process layer you choose expect for certain reserved process layers that are used

by Momentum (construction lines).

12

3

4

Click and then double click to finish the polyline

b. Verify that Vertex Snap mode is enabled (2).

c. Select the Polyline icon (3). Then zoom in very close to the end of the feedline. Then

add the polyline to the right end of the feedline (4), making sure to snap to the vertex

at each corner of the feedline. When using the polyline command, the mouse must

be double-clicked to complete the polyline drawing.

4. Set up the Substrate definition

a. In the Layout window, click: Momentum > Substrate > Create/Modify.

As shown here, be sure Momentumappears as the menu selection, notMomentum RF.

Later, you can save the substrate definition with a name.

Both substrate layers have the same values.

b. Set the first dielectric Alumina to thickness=12.5 mils and permittivity to 10. Click

Apply to write these settings.

c. Add another dielectric layer named Alumina_2 by modifying the name in the

Substrate Layer Name field. Then click the Add button. The new layer (Alumina_2)

should appear below the existing Alumina layer as shown here. If not, use the Cut

and Paste buttons to correct it.

d. Set the thickness of Alumina_2 to 12.5 mi; and the permittivity value to 10. Click

Apply to be sure the settings are written.

NOTE: DO NOT EXIT THIS DIALOG WINDOW YET.

5. Map the Strip Metallization layers to the substrate

a. In the Substrate editor, select the Metallization Layers tab.

By default, cond is mapped as a Strip on top of Alumina.

Click here on dashed line.

b. By default, the cond layout (process) layer should be mapped to Alumina as a

Strip. If not, change it so it appears as shown here.

c. Select the cond2 as the Layout Layer to be mapped (as shown here).

d. Select the dashed line (- - - - -) between the Alumina and Alumina_2 substrates.

This dashed line is the interface between the substrate (dielectric) layers where

only Strips and Slots are mapped (not Vias).

e. Click on Strip to map cond2 as a Strip between the two substrate layers.

Afterward, only the Unmap button will appear active.

6. Map the Via through the substrate

a. Select the Layout Layer hole (this is the via drawing layer) as shown here. Then

click the Alumina substrate layer. Vias are mapped through dielectrics and not

between interfaces.

b. Click the Via button. The result of the mapping is shown here: hole is a Via which

passes through the Alumina substrate layer.

c. Exit the substrate setup dialog click OK.

d. Click Momentum > Substrate > Save As and type in the name patch_substrate and

click OK. This saves the entries in the substrate create/edit dialog. The actual

calculated substrate for simulation is stored in a separate database (substrate

directory) using a numbered index. However, saving the substrate entries this way

(named) means you can recall it (Substrate > Open) for future use. Once computed,

Momentum will locate it and inform if it has already been calculated.

7. Precompute the substrate

a. Click Momentum > Substrate > Precompute.

b. Set the frequency from 1 to 10GHz, and click OK. The

computation will immediately run. Wait until it is finished

(check the status window) before going on to the next step.

8. Add a Port to the feedline.

a. As shown here, the entry drawing layer (1) must be set to cond2, because the input

port must connect to the feedline rectangle on cond2.

b. Select the Toggle Midpoint Snap Mode icon (2) to snap to the center of the edge

of the rectangle.

c. Select the Port icon (3), zoom in, and add a port to feedline left end (4).

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3

4

Toggle Midpoint Snap Mode

9. Define the Port type as: Single

a. Click on Momentum > Port Editor.

b. Select the port arrow on the drawing and it should automatically

appear as Single in the Port Properties Editor. Click Apply. The

construction line reference plane will be immediately drawn.

c. Exit the Port Editor: click OK.

10. Mesh separate Layers

The feedline (cond2), like all high frequency transmission lines, can use Edge Mesh for greater accuracy. The patch (cond) may not have as much current density along its edges, therefore the Edge Mesh is not required. Also, the patch can use a coarser mesh to save simulation time and Thin layer overlap should be on. Finally, Vias are not meshed (they are always one cell).

a. Begin by clicking Momentum > Mesh > Setup. Use the Global tab to set the

frequency value of 10GHz for the layer meshes that will be set up next. Also, turn

off Edge Mesh as shown here.

b. Select the Layer tab and select the cond layer (patch). Set it as shown here: 20

cell/wavelength and Edge Mesh OFF.

Global Mesh Freq=10GHz Mesh Density=30 cell/Edge Mesh: OFF

Cond Layer Mesh Density=20 cell/No Edge Mesh

Cond2 Layer Mesh Density=30 cell/Edge Mesh is No

c. Select cond2 (feedline) and set 30 cells/wavelength with Edge Mesh ON. Then click

OK to dismiss the dialog.

d. Click Momentum > Mesh > Precompute. The mesh will be calculated but only if the

substrate calculation has finished.

e. Verify that the meshed layout is complete like the one shown here.

11. Set up the Simulation and solve

a. Click: Momentum > Simulation > S-parameters.

b. Set up the following simulation: Sweep Type=Adaptive, Start=1GHz, Stop=10GHz,

and Sample Points Limit=25 as shown here. Also, turn off (uncheck) the Open data

display as shown.

c. Run the simulation by selecting Simulate. This will take a few moments. Afterward,

the results will be written to two datasets: patch_mom.ds and patch_mom_a.ds. The

default _mom is appended to both names (patch) and _a is appended to AFS dataset.

12. Plot the AFS simulation results

a. From the layout, open a new Data Display window: Window > New Data Display.

Then select patch_mom_a as the default dataset.

b. Insert a rectangular plot and add S(1,1) in dB. With Adaptive sweeps, a large number

of data points are derived from a few simulated data points. Here, approximately 15

frequencies are analyzed and from those data points about 450 frequencies are derived

and stored in the adaptive dataset with the extension: _a

c. Insert a marker on the dB(S(1,1)) trace to see the resonant frequency.

d. Add another plot of two traces: real part of Z0(1) for patch_mom_a and real part of

Z0(1) for the patch_mom dataset, you can see the impedance looking into the feedline.

This is the derived value from the AFS simulation.

e. Edit the trace and select Trace Options. Select

the Symbol at Data (circle) on the patch_mom.

Insert a marker as shown. These are the analysis

frequencies with more points concentrated around

the resonance. This Z value is calculated using the

cross section and the dielectric. It is not exactly 50

ohms which is the source Z.

13. Simulate again re-using simulation data

You can re-run the simulation to extend the frequency range or to simulate at a specific frequency. To do this, you simply add to the plan and reuse the previous simulation data. For a far field radiation pattern, the results can only be viewed for specific in a very narrow frequency band. While AFS (adaptive) can show the resonance, it may not actually simulation the specific frequency of interest. Therefore, the reuse feature can be used and a point added.

More data points simulated around resonance.

In the simulation Control dialog box:

a. Select the Sweep Type as Single.

b. Enter the frequency at the resonance: 3.859GHz

and click the Add to Frequency Plan List button.

c. Select the Reuse files from the previous

simulation button.

d. Simulate and answer Yes to the question box that

warns against reusing data if you make changes to

the structure or the mesh. The simulation will run

and your plot of S-11 will be updated to include the

new data point. Notice the status window messages.

14. Plot the Far Field Radiation Pattern Visualization

To examine the Far Field Plots, the resonant frequency must be selected and the calculations performed.

a. Click: Momentum > Post-Processing > Radiation Pattern.

b. When the radiation Pattern dialog box opens, select the frequency of 3.859GHz

which will appear in a list.

c. Ensure that 3D Visualization and Open display are checked as shown.

d. The Port 1 Excitation default settings should be:50 ohms and 1V as shown here.

e. Click Apply and then click on Compute to start the calculation of the far fields. The

status will show a message and a new window will open.

f. When the Visualization window opens, click: Far Field > FarField Plot to open the

Far Field Dialog box.

g. The following defaults should be in the dialog box as shown here: View_1, E for the

E field, Normalize and Log Scale with the Minimum dB set to -40 as shown. Then

click OK to display the plot.

h. When the Momentum Visualization window opens, you will see a 3D-plot of your

antenna.

i. Use the Mouse Controls to rotate, scale and pan. Or, try other settings such as the

Display Options.

j. When finished, close the window.

Procedure: 3dB Splitter

This design is an ADS microstrip in schematic with 5 ports ready to be refind.

1. Copy the schematic and examine the contents

a. Copy the supplied schematic design: splitter.dsn and then open it.

b. Confirm that the schematic looks like the one below:

NOTE on port numbers: Port 1 is the input,ports2 and 3 are the outputs. The output have 3dB of loss compared to the input. Ports 4 and 5 are used for connection of a resistor for a later circuit simulation.

2. Identify the MSUB layer and Port Layers

By default Microstrip schematic elements have their metallization mapped to the condlayer. To change the default layer when generating a layout (not generally recommended), you must change the MSUB Cond1 parameter to another layer.

a. Edit the MSUB (double click) and down to the Cond1 parameter. Check the box to

Display parameter on schematic as shown here.

b. Click OK and the MSUB will display the layout drawing layer cond as the drawing

layer where the splitter will be generated. Remember that each microstrip component

references an MSUB. For example, Subst= Msub1 . This is how the microstrip layout

are specified.

c. Identify the port layout layer. Port connectors in schematic are also

mapped to a layout layer. They must also match the same layout

layer as the connecting structure. To display this, edit the ports

(double click), select the layer and check thebox to display the

layout layer, similar to displaying the MSUB layer name.

Now, you have verified that all components will be on the cond drawing layer when you generate the layout.

3. Generate the Layout

a. In the schematic window, generate the layout by clicking Layout > Generate

Update Layout.

b. When the dialog box appears, it indicates will start creating the layout from the P1

port. Click OK to continue.

c. Another dialog box will appear, indicating that all elements were placed in layout

without any problems. The MSUB is not placed and grounds should always be

removed from schematics before generating a layout. Click OK to dismiss this dialog.

Due to default size of the ports in layout, ports 4 and 5 may be difficult to see because they are too large. In the next step you will resize the ports.

4. Charge the port arrow size and remove unwanted text

a. In the layout, click: Edit > Component > Port/Ground Size. Change the size to 5,

then select any port and click Apply. You will see the port arrow size change.

Zoomed in view or ports 4 and 5.

NOTE: You could also change the port size using Options > Preferences (Placement Tab) and then regenerate the layout.

b. To remove undesired text from the layout, click Option > Layers and uncheck the

Vis (visibility) box as shown here for silk_screen layers 14 and 31. Then click Apply

but keep this opened for the next step.

NOTE: You could use the Entry Layer dialog to change visibility and selectability. But changing colors requires editing. The Edit button in the Entry Layer dialog brings up the Layer Editor with is the same as Options > Layers.

c. Set the cond layer Color and Pattern to a style that you prefer. For example,

choose a different color and use Both Filled and Outlined with a light pattern to

differentiate them. Click OK when finished.

5. Mesh the curved surface

For this step, try three global different meshes with Mesh Reduction.

a. Try 45 degrees with 10 cells. Precompute and view the results.

b. Try 5 degrees with 30 cells. Precompute and view the results.

c. Setup and compute a final mesh for the purpose of continuing the lab exercise (as

shown): Frequency: 10GHz, 30 cells/wavelength and Arc Resolution: 30

degrees, Edge Mesh ON. Precompute and view.

6. Set up, save, and open the substrate definition

a. In the Substrate setup (Momentum > Create/Modify), set the thickness to 25 and

the permittivity to 10. All other settings are defaults as shown with cond mapped

as a metal strip. Click OK when finished.

b. With the entries in the substrate editor, use Substrate > Save As to save the

substrate entries with the name: splitter_substrate.

c. Open the substrate (Substrate > Open). This is NOT a supplied substrate. Select

splitter_substrate.slm, and use Substrate > Create/Modify to open it and verify it

as shown here. Now close it.

Saved substrate has been named.

NOTE on substrates Saving a substrate definition means saving only the dialog entries. These are stored in the networks directory as .slm files. The actual calculated substrates for simulation are either supplied (shipped with ADS) or precomputed by you. At this time do not precompute the substrate.

7. Examine the Model Database

This step is part of the look-alike component.

a. Click the command: Momentum > Component > Model

Database.

b. The Model database dialog will appear empty because

the look-alike component has not yet been created.

However, this is where the models (citifiles) will be

viewed and deleted as desired. Later, you will go back

and see the model.

c. Close the dialog click OK.

8. Create the look-alike component

a. Click the command: Momentum > Component > Create/Update.

b. Size: When the dialog appears, set the Size: min pin-pin distance for schematic units

to 0.25 as shown here.

8. Create the look-alike component

a. Click the command: Momentum > Component >

Create/Update.

b. Size: When the dialog appears, set the Size: min

pin-pin distance for schematic units to 0.25 as

shown here.

c. Model: Be sure Model Type is Momentum MW

and that the substrate is set to splitter_substrate

as shown here.

d. Set the frequencies as shown. These setting will

be used for the look-alike component.

e. Click OK and click OK to the message (component created).

9. Set up a schematic using the look-alike component and TFR

a. Without closing the layout window, go to the ADS main window and open a new

schematic and save it with the name: splitter_lookalike.

b. Insert the Momentum look-alike component into the schematic using the ADS library

or by typing the name: splitter.

With no database files, these settings have no effect at this time.

c. Complete the design by adding and wiring the components as shown here. The

step by step instructions follow:

Insert an S_Param simulation controller.

S_Param: Start=100MHz, Stop=10GHz, Step=100MHz.

Insert three Terms (S-parameter palette or type Term).

Connect grounds to the Terms and to the Ref.

Insert a TFR by typing TFR in the Component History field.

Wire the TFR between ports 4 and 5.

Set the TFR: W=6 mil and L=12mil and Rs=50 Ohm.

Insert an MSUB for the TFR by typing MSUB in Component History field,

Set the MSUB to H=25 mil and Er=10.

10. Edit the look-alike compinent

a. In your schematic, double click the look-alike

component and the dialog will appear. Here,

you should see the same settings that you

entered in layout when you created the

component. When you simulate, the Momentum

database is queried for these settings. If

Momentum has the solution in the model

database, the data will be used, if not (as in our

case for this lab) the Momentum simulator will

run. Afterward, the model file. For now, be sure

the Reuse Model box is checked.

Double click

b. Click OK to close the dialog.

c. Push into the splitter look-alike by selecting it and then using the push icon (shown

here). You will see the original schematic. If a design has no schematic ( layout

only) you cannot push into it.

d. Pop back out to the schematic next step will be simulation.

11. Simulate the design and plot the results

a. Check the schematic to be sure it is correctly set up.

b. Click the Simulate icon or the F7 key to simulate.

c. Notice what happens: the Momentum simulator is launched and several windows,

including the status window will appear. Simply wait until the simulation is

completed.

d. When the simulation is finished, the ADS data display will open. Go ahead and

insert a rectangular plot (dB format) of S-31 and S-21 as shown here. Try putting a

marker on the 6GHz point to verify the splitter s 3dB response. If you do not have

the same response, go back and check your steps.

e. Save the data display . Automatic Internal port settings

NOTE on internal ports When simulated, Momentum will automatically change ports 4 and 5 to Internal because the half wavelength calibration line will overlap parts of the geometry. There is no need to specify ports 4 and 5 as internal, unless you want the excitation point somewhere other than the point on the edge of the geometry.

12. Check the model file

a. Go back to the splitter layout and use the

commands: Momentum > Component >

Model Database verify that the Momentum

simulation has resulted in a database model file.

b. Click on file as shown here and you should see the Model Parameters listed. This is

the model that the ADS circuit simulator will use if the parameters match.

c. Go back to the splitter_lookalike schematic window and run the simulation again.

As you may see, the simulation is now faster because the ADS simulator queries the

database and finds the Momentum citifile in the database.

NOTE on solving the circuit first in Momentum Another way to use the Momentum data is to solve the circuit first in Momentum. After the simulation, you create the look-alike component. Then, in schematic, set the look-alike to use the Momentum dataset as shown here: Model Type is File Based and browse for the dataset file. You can also set the format to netlist, Touchstone or citifile and use other S-parameter or measured data files. Of course, the other way to use Momentum data is to assign it to an SNP as shown in the lecture topic slides.

13. OPTIONAL Momentum Simulation with embedded TFR

a. Copy and open the supplied schematic and layout: splitter_wtfr.dsn. This is a

similar splitter with the thin film resistor included in the Momentum analysis.

b. Change Rs to 50 Ohms, instead of 100 Ohms, then generate the layout and save

the design.

c. In order to properly model a circuit that contains multiple conductor types on one

layer it will be necessary to map the additional metal. Go to Momentum > Substrate

> Create/Modify. Select the Metallization tab and verify that both resi and cond are

mapped to the same interface (on top of the Alumina layer). Set the Conductivity for

resi as shown here: 50 Ohms/square (same as the schematic).

d. Run the AFS simulation from, without mesh reduction, 1 to 10 GHz (25 points) and

plot the following results to verify the splitter performance. Plot S22 and S33 on a

Smith Chart to see the output impedance of each arm and the effects of the TFR.

e. Go back to the schematic, run an S-parameter simulation (new dataset name) and

compare the results for the impedance on the same plot.

f. Afterward, save your work and close the designs and windows.

End of exercise.

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