Fast frequency sweep using the Method of Moments: including the effect of the substrate

We propose an interpolation technique for the impedance matrix that accounts for the presence of the substrate. The method is based on the observation that, in the spectral domain, only a small part of the spectrum varies significantly with the frequency. Hence, it is possible to efficiently compute on-the-fly the rapidly varying part of the spectrum while interpolating the remainder. The proposed method is illustrated and validated through the example of a sphere above a layered substrate.