HFSS15: Characteristic Impedance Column

The Characteristic Impedance Column (Zo) lists three options (Zpi, Zpv, and Zvi) in its drop down menu. The last two options Zpv and Zvi will appear only if you provide a voltage through defining an integration line for a specific mode such that a unique voltage for that mode can be computed. These quantities Zpi, Zpv, and Zvi need not be equal to each other. Other than TEM modes, these three quantities will give different results since the voltage is not unique and the result depends on the path used to compute the voltage.

In case you do not define an integration line only Zpi is shown.

Note: For more information, see calculate the characteristic impedance.

Electromagnetic power P = E x H (with magnitude of P i.e. the Poynting vector as 1 watt) is injected into the 3D model to calculate the fields, voltages, and currents. The basic equations for characteristic impedance are as follows:

The expressions for characteristic impedance in terms of power vary as follows:

When using Zpi:

When using Zpv:

Finally, for Zvi the following expression holds.

Note For more information about how HFSS defines these values, see Calculating the Z_PI Impedance, and Calculating the Z_PV Impedance.