Transmission line characterization in MWS

Can somebody guide me how to calculate the freqency dependant line impedance, attenuation constant and propagation constant of an arbirtrary transmission line calculated by FDTD (MWS)
I have access to E and H, the S-parameters, and of course the time responses.
In this case I cannot use the port characteristics because they don't represent correctly my structure (a strip line surrounded by conductive soft magnetic materials on dielectric (that we can consider lossless with respect to the mangetic materials)
I have to take a cross-section at some distance of the excitation ports
I dont even know if thoses characteristics are constant along the line (being able to express L/m for exemple).

Hello Supaswing,
You can use the eigenmode solver and extract the line impedance and Beta\Alpha of the line with respect to the propogating\attenuating mode.
If you cannot use eigenmode\port data, try defining Voltage and Current monitors along your structure, i.e. sample Z=V/I along the line at the same time index.
Good luck,
P.