Calculating Differential Impedance (Zdiff)

Using SI Xplorer's Impedance Wizard, you can configure and perform a differential impedance calculation.

Prerequisites:

• Use the Stackup Layers pane to select a layer. The Selected Layer Name field displays the currently selected layer.
• Use the Trace Cross Section button to open the HFSS Etch Factor window.
• Use the Frequency drop-down menu to select the frequency used for differential impedance calculations.

To calculate differential impedance:

1. Select the Analysis tab.
2. Select the Differential Nets tab.
3. Select your reference layers.
4. From the Trace Width and Trace Pitch fields, enter a trace width and pitch.
5. If you wish to define coplanar waveguide reference planes, select Define CPW ref. planes (edge-to-edge) to enable additional options.
   • You may select Left plane spacing, Right plane spacing, or both.
   • For W-element export, selecting Left plane spacing means that aggressors may only be added to the right of a victim trace; any traces to the left are removed. Selecting Right plane spacing means that aggressors may only be added to the left of a victim trace; any traces to the right are removed.
6. Click Compute Zdiff.
7. The Zdiff field updates to show the result.