Hi,

in CST Studio Suite  I am trying to add waveguide port signals together and then make fft to obtain spectrogram, so I can observe time how modes arise.

I can do thin to one mode signal. I was able to use 1D merge to join two modes and then FFT them, but once I have tried to add 3 or more modes together FFT fails with derivation by 0 error.

How can I add like 50 waveguide port signals and fft them all together?

Thanks.