Re: Frequency Range in CST?
[quote="Is there any physical meaning why results are different for different frequency ranges? Why is it favourable to take 0THz as lower limit?[/quote]
I would take the lower freq=0THz case as more accurate. Remember, T=1/df, where df = bandwidth of signal, so the bandwidth of the lower freq=0THz case is larger and at the same time the simulation will be shorter.
I do see a small, but distinct resonance, at around 340THz in the lower freq=0THz case, which is probably the same ripple that you see in the lower freq=1THz case. In my opinion, the smoothing you see in the lower freq=0THz case is because of the increased bandwidth of the excitation signal.
Since you increased the solver accuracy of the lower freq=1THz model and it is already well converged, one more thing to try is to run the lower freq=0THz case with an increased solver accuracy of 20dB and see if the resonances which get deeper and shift up in frequency a little. By increasing the simulation time you are the solver is forced to integrate the S-parameters using more data points and you may see an overal improved resolution in the frequency domain.