Lecturer
(Jia-Shiang Wang)
Radio Frequency-CAD Laboratory,
National Cheng Kung University,
Tainan, Taiwan
Outline
Momentum Basics: Microstrip Meander Line
Momentum RF Mode: RFIC Launch
Designing with Momentum: Via Fed Patch Antenna
Momentum Techniques: 3dB Splitter Look-alike
Momentum Optimization: 3 GHz Band Reject Filter
Advanced Topic: Coplanar Waveguide
Inductor EM simulation
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ADS Momentum
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Objectives
Know the use model Momentum with ADS.
Determine which circuits are best solved by Momentum.
Compare Momentum to Momentum RF.
Understand how the Momentum.
Use Momentum examples.
Simulation procedure.
Note on using ADS: it is recommended that you
know the basics of using ADS for S-Parameter
simulation. However, if you are new to ADS, this
course will provide enough basic instructions for
you to successful
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Who is Momentum?
2.5D (vias) simulation tool for passive circuits.
Motif style interface (connects to ADS).
Layout driven (accepts arbitrary geometry).
Method of Moments technique as planar solver.
Green s functions used to solve integral equations.
Unlimited substrate database for computation.
Full microwave or RF mode S-Parameter solutions.
Layout look-alike components for ADS simulation.
Co-simulation with ADS and optimization.
Visualization of current and far-field patterns.
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When should you use Momentum
When no analytical model exists- co-simulate with ADS.
Arbitrary geometry on a uniform planar substrate.
To determine coupling effects-thin layers and close proximity of metal.
To find narrow resonances not found using analytical-based models.
To display radiation patterns plot far-fields (antennas, etc.)
To display current patterns and density.
For CPW: coplanar waveguide results with no slot mode.
When 3D solvers take too long or are not required.
To optimize (modify geometry) a passive layout to achieve desired
results.
Momentum has two modes: a regular mode and an RF mode!
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Method of Moments
Method of Moments
Maxwell s Equations
Matrix Equation
[ Z] [ I] = [ V]
Equivalent Circuit
[ Z] = [ R] + j
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[ L] + 1/ j
[ C] -1
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How Momentum-Microwave Works-1
Mesh strips, vias, slots with
rectangles and triangles.
(arbitrary surface mesh)
Model surface current in each
current cell.( linear distribution)
Solve matrix of unknown surface
current coefficients.
Calculate S-parameters.
[ Z] [ I] = [ V]
[ S]
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How Momentum-Microwave Works-2
Fullw ave EM
Maxwell s Equations
Matrix Equation
[ Z] [ I] = [ V]
Equivalent Circuit
[ Z] = [ R] + j [ L] + 1/ j
Fullwave electric & magnetic Green s functions.
includes space and surface radiation.
L(w)&C(w) are complex and frequency dependent
Z(w) matrix reload CPU intensive.
[ C] -1
[ S]
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How Momentum-RF works -1
Mesh strips, vias, slots with
rectangles and triangles.
(arbitrary surface mesh)
Perform mesh reduction while
maintaining integrity of solution.
Model surface current in each
current cell.( linear distribution)
Solve matrix of unknown surface
current coefficients.
Calculate S-parameters.
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How Momentum-RF works -2
Quasi-static EM
Maxwell s Equations
Electro & magneto-static Green s functions.
Near field / low freq approximation
Matrix Equation
[ Z] [ I] = [ V]
Equivalent Circuit
[ Z] = [ R] + j [ L0] + 1/ j
L (w) = L0 + L1 R +L2( R) 2 +
C(w) = C0 + C1 R +C2( R) 2+
Neglects far field radiation
L0 & C0 are real and frequency independent.
Z(w) matrix reload very fast.
[ C0] -1
[ S]
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Comparison of RF mode to Microwave mode
DC
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200 GHz
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Spice, Mom & MomRF Model differences
SPICE
Momentum RF
Spice model
Momentum MW
S parameters S parameters
RF mode
MW mode
Quasi-static inductance
Quasi-static capacitance
DC conductor loss (s)
DC substrate loss (s)
dielectric loss (tgd)
skin effect loss
substrate wave radiation
space wave radiation
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Overview of the Momentum process
Start here:
or
Start here:
* Substrate is computed in
Momentum or Can be read
from a pre-computed
database.
ADS
interface
1a) Schematic with artwork
1b) Layout artwork
S12
2) Define the substrate*
0.00
MOM
interface
Mag. [dB]
-0.02
3) Mesh and solve
-0.04
-0.06
4) Display Results
-0.08
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Frequency
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Example Microstrip line in ADS schematic is transferred to
ADS layout for Momentum solution
Required Port
Schematic components must have
artwork that can transfer to layout.
If not, draw the geometry or import
The artwork into ADS layout.
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Momentum begins in the ADS layout window
Momentum
Menu
File > Import
Microstrip geometry with ports,
generated from schematic or
can be drawn in layout.
more
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ADS Layout: drawing and layer features
1.Drawing icons
Entry Layers
POP-UP.
Note: Do not
use default
layer 0 not
recognized in
momentum
Specify the entry layer before
drawing strips and slots for
momentum. However some
layers are reserved for
momentum.
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ADS layout: drawing and layer features
Ports for
Momentum
Snap Modes
Use Traces (Pins)
and paths (no pins).
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Momentum Menu commands in the layout window
Enable regular Momentum or Momentum RF.
Substrate layer and metal/slot/via layer definitions.
Port type and impedance settings.
Substrate enclosures can be described.
Layout component look-alike for schematic.
Mesh patterns defined and cleared.
Simulation s-parameter setups, including datasets.
Optimization setup by parameterizing the layout.
Visualize currents and radiation patterns.
Save files for use in a 3D tool.
Next, some details on substrates
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Momentum requires these 2 layers definitions
Substrate Layers
Metallization Layers
Strip (metal) or slot
(located at the interface of two
substrates)
Strip (metal) or slot
Via extends through substrate
Substrate layers can be read from schematic or
define in the Substrate Editor (Next slide).
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Substrate Editor: Substrate Layers tab
Update From schematic
Means that the MSUB definition
is copied from ADS schematic.
Next, you define the Metallization (drawing layers)
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Substrate Editor: Metallization Layers tab
1) Select the Substrate interface -and then select the layout drawing
layer (metal drawing layer).
2) Specify Strip or slot between 2
interfaces or a Via through a
substrate layer.
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After defining the layers, use: Substrate >
Precompute. If the definition has already
been computed, Momentum will find it in
the database. If not, it will compute it.
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Define the Mesh pattern
Global mesh is the default,
with default setting. But
you have choices.
In general, small patterns
are more accurate but take
more time to solve.
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Mesh reduction: converts
some rectangles and
triangles to polygons for
fewer currents to solve.
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Global mesh example with edge mesh
1 - Port
2 - Calibration Line
3 - Mesh
4 Edge Mesh
The calibration line
Is automatically
drawn when the
port is defined
more on this later.
1
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Here, the cell size is the same for all
parts of the geometry, except for the
edges around each primitive.
4
3
2
Note: you can view the mesh, ports,
and reference line before simulating
and make adjustments if desired.
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Primitive mesh example
The center primitive of this geometry has a
different mesh density (50 cells/wavelength)
than the two outside geometries (20
cells/wavelength)
1
2
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Port Editor: define port types (Properties)
First, you select the port
and then you define its
properties:
Single port (default) is
attached to the edge
and the calibration
reference plane is drawn
parallel to the edge
Port connector icon
in schematic or
layout is used to
add ports.
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Summary of port types
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Simulation control: S-parameters
To set up a simulation: choose the
sweep type and enter the values.
Dataset name can
be specified.
Default is layout
name_mom.
Also, data display
can automatically
open with all Sparameters plotted
if box is checked.
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The momentum solution process
1
Substrate Calculator
Green s Function
4
3
Mesh Generator
2
5
Substrate Database
(Archive)
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Planar Solver
S-parameters
(ADS dataset)
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Simulation results: ADS Data Display window
Data display window can
be automatically named
Dataset name: a refers
to adaptive AFS.
Mag and phase plots for
all S-parameters
automatically plotted if
the box is checked in the
simulation control.
Or you can open a data
display window and plot
selected data. You will
practice this in the lab
exercises.
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Layout look-alike components for ADS schematics
Layout look-alike component created and inserted in
ADS schematic. ADS simulation runs Momentum or
component can be pre-solved.
Inserted look-alike
component from
ADS library.
Parameters Specify
how the component can
be modified for ADS
optimization from
schematic.
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Dataset is created
for use by ADS
simulator.
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Using ADS Momentum Examples
Click the Examples
Icon
Each project has
numerous designs with
solutions. Copy the
project into your
directory and use it for
your design!
Spiral Examples
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Example: spiral inductor with via and hole
in ground
Purpose of the hole in the ground plane is to
reduce capacitance of the inductor to ground.
Port1 and port2 are on different layers.
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Review
1.
2.
3.
4.
5.
6.
7.
8.
9.
Simulation procedure
Create a physical design
Choose Momentum or Momentum RF mode
Define the substrate characteristics
Solve the substrate (optional)
Assign port properties
Add a box or a waveguide (optional)
Set up and generate a circuit mesh
Simulate the circuit
View the result
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1.Create a physical design
Physical design created in schematic
window: spliter
Layout representation
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2. Momentum or Momentum RF mode
Momentum
Momentum RF
Click here to
switch the mode
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3.Define the substrate characteristic
Properties of the
selected layer
Set substrate
Layers here
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4.Define the substrate characteristics
Set Metallization
Layers here
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5.Solve the substrate (Optional)
Optional:
because the substrate
will computed during
the simulation if not
computed.
Choose the frequency
a Momentum simulation.
Not Needed for a Momentum
RF simulation.
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6. Assign port properties
5 types of ports:
- single
- internal
- Differential
- Common mode
- Ground reference
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7. Set up mesh
Momentum> Mesh> setup
Mesh frequency
The number of cells per
wavelength
Arc Facet Angle
Enable appropriate mode:
- Edge Mesh
- Transmission Line Mesh
- Thin Layer overlap extraction
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8.Generate mesh
Enter the frequency you want to use for
pre-computation of the mesh
The wavelength of this frequency will, in
part, determine the number of cells in the
mesh
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9. Simulate the circuit
Momentum > Simulation > S-parameters
1. Select the
sweep type and
the frequency
range
2. Click on Add
to frequency
Plan List
3. Click on apply
then on simulate
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10.View the results
Display window
Notice the name: mom_spliter
_a in mom_spliter_a
means the results
are taken from the
adaptive simulation.
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Time to do the lab exercise!
Lab 1: Momentum Basic: Microstrip Meander Line
Lab 2: Momentum RF Mode: RFIC Launch
Lab 3: Designing with Momentum: Via-fed Patch
Antenna
Lab 4: Momentum Techniques: 3dB Splitter
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Lab 1: Microstrip meander line
Start ADS
Copy the training project
Create the layout
Examine the Substrate
Examine Port setup
Set layer fill
View the mesh
Run the adaptive simulation
View the default data plots
Plot the S-21 data
S12
0.00
Mag. [dB]
-0.02
-0.04
-0.06
-0.08
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Frequency
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On-line Help and Examples
On-line ADS Help:
- Momentum:
Help > Topic and index (F1)
Manuals > Simulation > Momentum
- Layout:
Help > Topic and index (F1)
Manuals > Design and Display > Momentum
- Search:
Help > Topic and index (F1) > Search
Examples:
- At ADS main menu:
View > Example Directory > Momentum >
Tools > Example Search
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