HFSS15: Specifying Thermal Modifiers

To specify Thermal modifiers for a material:

1. In the View/ Edit materials dialog you must enable the View/ Edit Modifier checkbox for Thermal Modifier.

This causes the Properties of the Material table to expand to include a Thermal Modifier column. By default, the Thermal Modifier property is set to None.

2. Selecting Edit... from the drop down menu, rather than None causes the Edit Thermal Modifier dialog to appear.

3. Select Expression radio button to display the Parameters Modifier text field or the Quadratic radio button to display the tabs for Basic Coefficient Set and Advanced Coefficient Set.

• With Expression selected, you can write an equation for a thermal modifier in the Parameters Modifier text field.

The expression whether to use Celsius or Kelvin is totally problem dependent. If a material thermal coefficient is defined as alpha/c_deg, then it is Celsius. On the other hand, if a material thermal coefficient is alpha/k_deg, then it is Kelvin.

• Checking Use temperature dependent data set disables the Modifier text field. You can then use the drop down menu to select Add/Import Dataset. This lets you define the thermal modifier as a data set.

• With the Quadratic radio button selected, in the Basic Coefficient tab, you can edit fields for the TempRef and units, and fields for C1 and C2 for the following equation:

• P(Temp) = Pref[1+ C1(Temp - TempRef) + C2(Temp - TempRef)^2]

• where the Pref is defined as the reference relative permittivity.

• With the Quadratic radio button selected, in the Advanced Coefficient Set tab, you can edit fields for lower and upper temperature limits (TL and TU respectively) and select their units from the drop down.

You can also edit the constant value limit for the thermal modifier values outside the limits. By default, these are automatically calculated. Uncheck the Auto Calculate TML and TMU to specify new values for thermal modifier lower (TML) and thermal modifier upper (TMU).

4. Click OK to accept the edits and return to the View/ Edit materials dialog.