momentum part2
TRANSCRIPT
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).
12
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.
This document was created with Win2PDF available at http://www.daneprairie.com.The unregistered version of Win2PDF is for evaluation or non-commercial use only.