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Design Notes
SWITCH VIEWS AND SWITCH LISTS
Switch Views and Switch Lists provide an easy way for a designer to toggle between different versions of a model while maintaining a single layout cell for that instance. This could include linear models, nonlinear models, EM data, measured results, etc. Another interesting use for Switch Views is allowing designers to create an LVS view of their schematic parts that normally wouldn't make sense to an LVS engine like Touchstone files or EM models. This allows designers to run LVS from their real, RF schematics and alleviates the need for a DC schematic, which ultimately is a potential source of error for LVS.
Overview
This project is a simple example demonstrating Switch Views and Switch Lists using a simple microstrip line and using 5 different models for that line.
Definitions
Switch Views - alternative model views or model implementations. The Switch Views get a name of the designer's choosing. Normally, this name is standardized for all switch views containing a similar type of model. It is very important that Switch Views for a subcircuit contain the same number of ports as the top level circuit, a consistent port numbering scheme, and the same passed parameters.
Switch Lists - The mechanism through which the user picks the different Switch Views. A Switch List tells the simulator "when evaluating this circuit, see if there is a view called 'Nonlinear' for any of the parts in the circuit and use it if you find it, otherwise, just use the normal circuit models." The Switch List get a name of the designer's choosing. Switch lists are chosen on each individual Measurement by selecting them in the Configuration drop down menu.
The real value Switch Views and Switch Lists is that all Measurements point to the same Schematic and Layout, but can utilize different models.
Creating Switch Views
To create a Switch View for a subcircuit, make a new Schematic named "Subcircuit_Name/Switch_View_Name" where Subcircuit_Name is the name of the Schematic for which the Switch View is being created and Switch_View_Name is the name of the Switch View that is being created. Alternately, right click on a schematic and select Add Switch View to get a dialog to add the view.
Creating Switch Lists
To create a Switch List, select Simulate > Manage Simulation Filters From the Filters section, select the New button, type in the Switch List name, and click OK. Then select the Switch List you just created and in the Design View section, select New. From the new dialog that comes up, from the Select top level design for switch view, select the Subcircuit_Name used for your Switch View. Then from the Available view area, select the Switch View name and use the Add button to add this name to the View list area. Click OK when done. You can also add a Switch View name to the Available view list if you want to enter Switch View names this way.
Switch Views In This Project
This project is setup to focus only on Switch View concepts based on a transmission line model. Switch Views and Switch Lists are used to simulate 5 different models for this transmission line. These models include:
1. Closed Form Microstrip Model.
2. Quasi-Static Microstrip Model.
3. LC Equivalent Circuit Model.
4. EM Simulation with coarse gridding.
5. EM Simulation with fine gridding.
The default model is the Closed Form Microstrip Model, this is in the schematic named "model". The others are all in Switch Views as follows:
1. "quasi" = Quasi-Static Microstrip Model.
2. "equiv" = LC Equivalent Circuit Model.
3. "EM1" = EM Simulation with fine gridding.
4. "EM2" = EM Simulation with coarse gridding.
You can open each one of these schematics to see what they look like.
With this setup, anytime the subcircuit "model" is used in a schematic, the user can configure any of the Switch Views listed above.
Switch Lists In This Project
The Switch Lists that have been configured for this schematic can be seen by selecting Simulate > Manage Simulation Filters. For this project the following Switch Lists are included:
1. "lumped" - only looks for the Switch View named "equiv"
2. "EM_fine" - only looks for the Switch View named "EM1"
3. "all_with_order" - Has all the Switch Views listed in the order, "EM1","EM2", "equiv', "quasi".
4. "EM_coarse" - only looks for the Switch View named "EM2"
5. "quasistatic" - only looks for the Switch View named "quasi"
Using Switch Lists
With all the Switch Views and Switch Lists defined, they can be used in simulation. The graph S21 shows the simulation results using all the configured Switch Lists. To see this, look at the measurements on this graph, and pay particular attention to the Configuration setting on each Modify Measurement dialog box (double click on measurement in project browser to see this).
Several issues to note:
1. For a given Switch List, if the Switch View is not available, it goes back to the default for that Switch View. You can see this if you delete or rename all the Switch View schematics from the project and simulate. All the answers will be identical.
2. The Switch List "all_with_order" has several Switch Views listed. In this case, the simulation will use the first Switch View found in the list. So in this case, the measurement with this Switch_List matches the results with the "EM_fine" Switch List since the Switch View "EM1" is the first in the list. If you delete or rename this Switch View schematic and resimulate, the results will now match the "EM_coarse" Switch List measurement since the Switch View "EM2" is the first one in the list that was found.