# Base Multiport Feko Simulation

A base multiport Feko simulation is required to generate the
required input data for the *Multiport post-processing*
application macro.

S-parameters are calculated in Feko by
loading all ports with the port reference impedance and then, in turn, exciting each
port in the model. The voltages and currents calculated at all the ports can be combined
to determine the S-parameter matrix. For multiport post-processing,
the field values (near and far fields) also need to be determined for each configuration
in the S-parameter calculation. This requires that *m+1*
simulation solutions need to be performed by default, where *m* is the number of
ports in the model.

*m*simulations for a model consisting of

*m*configurations:

- The loads for all configurations must be identical and set to the reference impedance for the multiport system.
- Each configuration has a single source and for all the configurations, each port is excited once.
- Requests in all configurations must be identical.
- All other configurations settings (except for the excitations) are identical.

Since the loads are identical for all configurations and only the source is modified between configurations, the simulation is performed efficiently when using the method of moments (MoM) since the expensive matrix fill and LU-decomposition is only performed once at each frequency.

For all subsequent configurations, only the right-hand side vector (sources) is updated and a backward substitution is performed before calculating the output for the requests.