Characteristic impedance[s] of the network ports.

This property stores the characteristic impedance of each port of the network. Because it is possible that each port has a different characteristic impedance each varying with frequency, z0 is stored internally as a fxn array.

However because z0 is frequently simple (like 50ohm), it can be set with just number as well.

Returns:z0 – characteristic impedance for network
Return type:numpy.ndarray of shape fxn