Calculating highly oscillatory EM transients by using rational-function interpolation and FFT

We compare results for EM transients calculated using frequency domain analysis coupled with FFT with and without frequency-domain rational-function interpolation, in order to reduce the total number of frequency samples needed for accurate calculation of transients. To further reduce the total analysis time, we use zero-padding, for all frequencies where excitation spectrum is negligible. The proposed approach is applied to a problem of finding transient EM fields within metallic resonator with high Q-factor. The presented results show that time-domain response can be calculated more efficiently, with preserving the overall accuracy, if the proposed rational-function interpolation in frequency domain is used.