Response surface modeling of microwave filters using coupling matrices

An efficient methodology for creating fast and accurate surrogate models of microwave filters is presented. Instead of approximating S-parameters of the filter structure under consideration directly, the proposed approach is based on response surface modeling of its coupling matrix coefficients. The dependence between designable parameters (filter dimensions) and coupling matrix coefficients is considerably smoother than for S-parameters. As a result, our approach allows obtaining accurate surrogates with substantially smaller number of training samples than required by conventional techniques. The proposed technique is illustrated using a 3^rd-order substrate-integrated waveguide filter, as well as compared with a benchmark method (here, direct kriging interpolation of S-parameters). An application of our modeling technique for filter optimization is also included.