# S-parameters

S-parameters data consist of the S-parameters for all active ports as well as a table of reference impedances used at each port.

S-parameters are requested with the SP card or with an S-parameter configuration in CADFEKO. Two tables of data are printed to the output file. The first lists the impedance at each port.
                     S-PARAMETER REFERENCE IMPEDANCES AT PORTS

port     impedance in Ohm
1        5.00000E+01
2        1.00000E+02
Further into the output file the S-parameters are listed for each source as shown below. Note that inactive ports are only used as sink ports, that is, they are not excited and no data block is created for these.
Note: Ports are set to inactive in CADFEKO in the Request S-parameters dialog and in EDITFEKO the source (such as the A1 or AE card) must be set to zero amplitude.
All the ports are loaded and Feko therefore also writes the loading information to the output file. For example, for an S-parameter request using edge ports, the following data will be written to the output file:
                      DATA FOR EDGE LOADS

Name:
Complex impedance:             ( 5.00000E+01 +j 0.00000E+00) Ohm (freq. dep.)
Attached to port:              Edge port
Port between triangle labels:
Union1.Face53_1  Union1.Face53_2
Port edge length in m:         4.60000E-03
Number of edges:               2
Indices of the edges:          809   814
For the S-parameter data, the second data line below gives S21 or the coupling to port 2 when port 1 is excited.
                              SCATTERING PARAMETERS

ports                                        magnitude          phase
sink source     real part   imag. part      linear      in dB     in deg.
S     1      1   8.20232E-01 -3.08302E-01   8.76260E-01   -1.1473    -20.60
S     2      1  -1.09955E-02 -5.19575E-03   1.21613E-02  -38.3004   -154.71
Sum |S|^2 of these S-parameters:    7.67979E-01   -1.1465