CST Simultaneous Excitation

[anmolb80]

Hey guys,

I need to simultaneously excite 3 ports with different excitation signals. I am doing this by selecting the excitation signal in the simulation module (shown in Figure 1 attached). I am having trouble with the simulation results. The S-parameters obtained from the simulation do not make any sense (Figure2). Can someone please tell me if this is the right method for excitation or not?
I do not get any problems with the S-parameters when I excite all ports with the same excitation signal (Figure3). For this case i dont use simultaneous excitation. I just set a signal as reference signal and simulate. How come the simulation results dont make any sense when simultaneous excitation is used? any help would be much appreciated.

 

[FvM]

The S-parameters obtained from the simulation do not make any sense (Figure2).

How can you know?

You have magnitude only s-parameters, phase is unknown. Thus you can't predict if superimposing signals at multiple input ports will increase or decrease the magnitude at a certain frequency.

Presumed you are modelling a linear system (e.g an antenna array), the result with simultaneous excitation can be predicted from the complete (magnitude and phase) set of s parameters.

 

[anmolb80]

Thanks for the reply FvM. The S-parameters obtained from the simulation (figure 2) dont make sense to me because of the labelled notation. CST usually provide both the reflection coefficients and coupling parameters in the S-parameters folder. you can see this in figure 3. but for some reason when I try to simultaneously excite ports I only get 3 signals in the S-parameters folder instead of the expected 9 signals (like figure 3).
so what im trying to understand is what exactly does the "simulataneous excitation" option in CST do and also what the labelling in figure 2 means (S11? S21?)
Again any help is much appreciated! thanks