Fast rational function fitting of broadband multi-port responses via repeated random sampling

A methodology is presented for the computationally-efficient and accurate rational approximation of broadband electromagnetic responses of passive multi-ports. The proposed method relies on the repeated rational interpolation of subsets of the frequency data with the number of samples in each set being a fraction of that in the original set. The generated poles from the subsets are appropriately combined to serve as the poles of the multi-port system and to solve for the residues of its rational function fit. The expediency of this methodology is demonstrated through its application to the fitting of several multi-port broadband data.