Returns the active s-parameters of the network for a defined wave excitation a.

The active s-parameter at a port is the reflection coefficients when other ports are excited. It is an important quantity for active phased array antennas.

Active s-parameters are defined by [1]:

\[\mathrm{active(s)}_{m} = \sum_{i=1}^N s_{mi}\frac{a_i}{a_m}\]

where \(s\) are the scattering parameters and \(N\) the number of ports

Parameters:a (complex array of shape (n_ports)) – forward wave complex amplitude (pseudowave formulation [2])
Returns:s_act – active S-parameters for the excitation a
Return type:complex array of shape (n_freqs, n_ports)

See also

active Z-parameters
active Y-parameters
active VSWR


    1. Pozar, IEEE Trans. Antennas Propag. 42, 1176 (1994).
  1. Williams, IEEE Microw. Mag. 14, 38 (2013).