Purpose: Generate layout for SYMMIC thermal analysis

Description

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. (www.symmic.net).

To use Layout_To_SYMMIC 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_HPA example project shown above, a generic FET template was configured (in SYMMIC) to the materials and dimensions of the MESFETs in the output stage of the amplifier. The device template was saved as OutputFET.xml and then the number of gates was changed to match the MESFETs in the driver stage and the device was saved again as DriverFET.xml. With these device templates defined, the Layout_To_SYMMIC script could then be used to position the devices for thermal analysis of the MMIC.

Run Layout_To_SYMMIC from AWR Design Environment. From the list of project schematics on the left side of the first dialog, select the schematic which has the layout for the MMIC. The boundary of the layout for this schematic determines the overall dimensions (length by width) of the MMIC. Selecting the Begin Layout button will begin creating the SYMMIC layout data file using this length and width. (Note: In some case the layout window might need to be resized or closed for this to work properly.)

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.

In the next 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.

Before adding devices to the layout, enter the name of the device template file in the edit box, e.g. "OutputFET.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 AWR 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 AWR layout. For example, the MESFETs in AWR's MESFET 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 data file to place the centers of the device templates at the same centers found in the project. The script 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. Export the data file to a folder containing the device template files so that the layout can be successfully loaded in SYMMIC. It is important that this file be given a .xml suffix when saving because data files in AWR are assumed to be .txt files by default.

If the power table was created while running the script, its entries can be updated by running the simulation in AWR Design Environment, as shown above. The power table reports the total power (PT) measurement across each device, which is the same as the TOT_PWRA annotation. The power table values can be used to set the power levels in SYMMIC.

The script is a *.bas file. You need to load it into your AWR project by using the Import... function within the Scripting Editor before you can run it from the Scripts menu. A video tutorial demonstrating the use of the script can be found at www.symmic.net.