Momentum Optimization

Momentum Optimization, in combination with Momentum, is an effective software tool for automated electromagnetic (EM) design optimization of planar structures. Performing an optimization using Momentum enables you to adjust layout parameters in order to improve the circuit performance according to your design goals, and supports designs developed using the Momentum microwave or Momentum RF mode.

Optimization using Momentum is performed from within the schematic environment using parameterized Layout Components. This process is described in the Example section.

Momentum is an analysis tool that can be used to accurately account for various EM effects such as couplings or radiation. It is extremely valuable for design verification, but cannot, by itself, determine the layout that meets your design goals. Physical design is usually a trial and error process in which the designer uses Momentum to achieve the goals. Optimizing with Momentum, using parameterized layout components can save valuable engineering time. It can significantly shorten the design cycle, facilitating faster time-to-market, and for more complex structures, it can usually find better designs than those found manually.

What Can be Optimized Using Momentum?

Momentum Optimization enables you to optimize geometrical dimensions of 2D layout objects (shape optimization). This includes optimizing:

The objects can be metal strips, slots or vias. The underlining technology of object parameterization provides for significant flexibility in layout modification. The parameterization process is carried out within the ADS schemeatic drawing environment.

What Cannot be Optimized Using Momentum?

Momentum does not accommodate optimization of:

What Responses Can be Optimized Using Momentum?


Any response that can be defined using the optimization goal component in schematic can be optimized. Refer to Tuning, Optimization, and Statistical Design for more information. Typically it will be design goals for the S-parameters in any of the following forms:

Typical Steps for Optimization Using Momentum

In general, a typical Momentum Optimization session would take place as follows:

  1. Create an ADS layout to the best of your design experience using parameterized layout components. Draw it as close as possible to what you expect the final design to be. You do not need, however, to spend a lot of time selecting exact dimensions. Rather, take advantage of drawing convenience to save time.
  2. Setup an Momentum simulation: substrate, metalization, port, meshing, etc.
  3. Simulate your design using the Momentum > Simulation menu option. View the responses of interest. If you are satisfied with the circuit performances you do not need to optimize your design.
  4. Make as good a guess as possible whether some adjustments to layout dimensions could improve your circuit performance. Consider how the layout should be modified to achieve the desired improvement. If a fundamental change to the layout topology is needed, do it now and repeat the simulation.
  5. Define conceptually independent parameters to facilitate the desired layout modifications.
  6. Decide on how the circuit performance can be formally expressed by design goals in terms of frequency points, S-parameters, and upper, lower, equality or window specifications.
  7. Save your design.

The Optimization Process

  1. Create a layout component (see Creating a Layout Component) from the design and add the definition of the parameters you identified
  2. Create a schematic with the layout component
  3. Define the optimization goal(s)
  4. Setup the optimization parameters
  5. Run the optimization
  6. The optimum parameter values will be displayed in the status window
  7. Optionally resimulate the layout component from layout with the optimum parameter values

Example

This section provides an exercise illustrating how to set up, perform and view the results of co-optimization.

Copying an Example Project

Start by copying an ADS Momentum example project into your local directory.

  1. From the Main window, choose File > Copy Project...
  2. In the Copy Project dialog From Project section, choose Example Directory .
  3. Select Browse... .
  4. In the drop down menu, choose Momentum > Microwave select Coupled_line_filter_prj and click OK to select project.
  5. In the To Project section, select a location for the project to be copied to.
  6. Activate Copy Project Hierarchy and Open Project After Copy then, click OK. This opens the project and saves it to the new location.

Editing the Component

This section describes how to prepare and parameterize a component for co-optimization.

  1. When the project opens, dismiss the README window.
  2. Select the Coupled_line_filter layout window.
  3. From the Layout window toolbar, choose Momentum > Mesh > Clear.
  4. Next, choose Momentum > Component > Parameters . This opens the Momentum Component Parameters dialog.
  5. In the Create/Edit Parameter section, type L1 for the parameter name and. choose Subnetwork for the parameter type. The set the Default Value at 300 um.
  6. Click Add then select OK .
  7. In the Layout window double click on Microstrip Line TL6 to select it. This opens a new dialog.
  8. Select Parameter L in the MLIN column and set Line Length L to L1 in the Parameter Entry Mode column.
  9. Click OK to dismiss this dialog.

Creating the Parameterized Component

This section describes how to create the parameterized component.

  1. In the Layout window, select Momentum > Component > Create/Update . This opens the Create Layout Component dialog.
  2. In the Symbol section of this dialog, choose layout look-alike and enable Add reference pin.
  3. In the Model section, ensure the Model Type is set to Momentum RF , set the frequency range from 25 GHz to 50 GHz and deselect Edge Mesh.
  4. Click OK to create the parameterized component.
  5. This brings up two new dialogs, select OK in the message window advising you the component was successfully created and select No in the Add simulation to Model Database dialog.

Adding and Using the Component in a Schematic

This section describes how to add and use the parameterized layout component in the schematic.

  1. Open a new Schematic window. Insert the newly created component by opening the library browser and selecting Sub-networks > Coupled_line_filter_prj > Coupled_line_filter component. Place the layout component in the Schematic window.
  2. Add 2 S-parameter ports and 3 grounds to the schematic as shown in the following illustration.
  3. Add an S-parameter simulation block to the schematic. Set the Start frequency to 25 GHz , the Stop frequency to 50 GHz and the Step-size to 0.1 GHz .
  4. Click OK.

Optimization Setup for a Parameterized Layout Component in the Schematic

This section discusses setup required to the optimize a parameterized layout component during schematic simulation.

  1. Double click the Coupled_line_filter component. This brings up the Momentum Component dialog.
  2. Choose the Parameters tab, then select the Optimization Setup... , to bring up the Optimization dialog.
  3. In this dialog, set Optimization Status to Enabled , set the Minimum Value to 200 um and the Maximum Value to 400 um.
  4. Click OK.
  5. Add a Goal and an Optimization block to the schematic.
  6. For the Goal block set:
    • Expr = "dB(S11)"
    • SimInstanceName = "SP1"
    • Max = -10
    • Weight = 1
    • RangeVar[1] = "freq"
    • RangeMin[1] = 39 GHz
    • RangeMax[1] = 42 GHz
  7. In the Optimization block set the Optimization Type to Minimax.
  8. Save the schematic design as " filter_opt ". Choose File > Save Design As...
  9. From the Schematic window, choose Simulate > Simulate to start the simulation.
  10. After 9 iterations the optimized value of 207.039e-6 is shown in the status window.

 

Privacy Statement  | Terms of Use  | Legal | Contact Us  | © Agilent 2000-2008 

Contents
Additional Resources