What are the F-parameters, how are they computed in CST and what is the relationship between S- and F-parameters?
In CST, they can be obtained, when running the integral solver and having a farfield-source imported. However, because I have no other active port, I cannot see the S-parameters. Those F-parameters are also having a real and an imaginary part, being dimensionless, like the S-parameters.
I suspect that the reference signal might be somehow normalized, but it is just a guess.
Thank you!
Best Answer
F-parameters are used to calculate antenna coupling coefficients between nearfield or farfield sources. If a field source is not activated, only receiving coupling coefficients will be computed for that source. However, this option is only available for simultaneous field source excitation.
In general, S-Parameter results are given as the ratio of incident and reflected voltage wave spectra at a port, where only one port is excited and all others are perfectly matched. Consequently, for transient simulations, all port signals first have to be transformed into the frequency domain, providing broadband results for one port excitation with only one simulation run.
However, in the case of simultaneous excitation, several ports are stimulated at once, so it is not possible to apply the general S-Parameter definition anymore. Instead, the incident and reflected spectra are given as incident and reflected F-Parameters, all normalized to the spectrum of the reference signal. Thus, F-Parameters are not necessarily normalized to any incident spectra or any input/output power(s). The incident F-Parameter of e.g. port number 1 is shown in a form similar to F1[ampl, phase, signal] or just as F1[simul1] in case that the excitation setting string of the given port is too long, whereas the reflected F-Parameter is given as F1,simul1 (in both cases simul1 is assumed to be the combination name of the simultaneous excitation).