Tools for Materials Characterization


ADS Script: Layout to SYMMIC

This script is used on a MMIC layout to generate the template file for input to SYMMIC. SYMMIC is a thermal simulator for MMICs provided by CapeSym, Inc. (

To use LayoutToSYMMIC.ael on a project with a MMIC design, first configure the SYMMIC device templates to represent the thermally significant devices in the design. The device template includes all the information on the stack up and the operating conditions in an easy-to-configure format. For the MMIC_Amp example project shown above, a generic FET template was configured (in SYMMIC) to the materials and dimensions of the FETs in the output stage of the amplifier. The device template was saved as Stage2FET.xml and then the number of gates and finger width was changed to match the FETs in the driver stage and the device was saved again as Stage1FET.xml. With these device templates defined, the LayoutToSYMMIC Application Extension Language (AEL) macro can then be used to position the devices for thermal analysis of the MMIC.

Begin by opening the layout of the MMIC design in Advanced Design System (ADS). The boundary of the layout is determined from the overall dimensions (length by width) of this layout. Run the AEL macro LayoutToSYMMIC.ael using the Command Line utility in the Tools menu of the Main window. A dialog will appear showing the components of the layout. In this dialog, select a subcircuit that contains the devices to be analyzed and press the Enter Subcircuit button. Once the proper device level has been reached, the devices may be added to the data file by using the Add to Layout button.

If you want to generate a table of device powers along with the layout, check the box above the list of schematics on the right side and select the schematic for the simulation to run. In the example shown, the schematic NLWholeAmp defines a harmonic balance simulation at a specific frequency and input power level. The simulation schematic chosen on the right must have the MMIC schematic chosen on the left as an immediate subcircuit in order for the power table to be generated.

Before adding devices to the layout, enter the name of the device template file in the edit box, e.g. "Stage2FET.xml". If this device template represents half of a full device, check the Mirror template in X checkbox to put both halves of the device in the layout. If the device(s) have a different orientation in the ADS layout than the device templates in SYMMIC, use the drop-down box at the right to add an angle offset. This offset angle is the movement of the SYMMIC device template necessary to give it the same orientation of as the device in the ADS layout. For example, the FETs in ADS's DemoKit library are defined with the gates horizontal whereas the gates are vertical in SYMMIC's generic FET template, so a counterclockwise rotation of the generic FET template is required.

Select one or more devices to add and then press the Add To Layout button. Entries are created in the layout template file to place the centers of the device templates at the same locations found in the project. The macro also reproduces the rotation angle and flipped states of the devices in the project., but these can always be modified later in SYMMIC if there are discrepancies.

Additional devices from other subcircuits can be added using different device templates. Once all thermally significant devices have been added, use the Complete button to close the layout template. The layout template .xml file will be created in the networks subfolder. Move or copy this file to a folder containing the device template files so that the layout can be successfully loaded in SYMMIC. In SYMMIC set the power levels for the devices. When a device template is used repetitively with the same power level, this process can expedited by opening the device template before opening the layout and setting the power just once. Then, open the layout template in SYMMIC and run the thermal analysis by selecting Run simulation from the Solver menu.