A Novel Technique for the Direct Determination of Multimode Equivalent Circuit Models for Substrate Integrated Waveguide Discontinuities

A novel technique is presented for the automatic, self-consistent and direct determination of wide-band lumped-element equivalent circuit models (if substrate integrated waveguide discontinuities. This technique is based on the full-wave analysis of substrate integrated waveguide components by using the Boundary Integral-Resonant Mode Expansion method, which provides a generalized admittance matrix of the components in the form of a pole expansion in the frequency domain. This expression of the admittance matrix permits to directly identify the topology of a multimodal equivalent circuit and the values of its lumped elements, thus avoiding any initial guess or fitting procedure. The basic theory of the full-wave analysis method and the procedure for determining the equivalent circuit model are reported. The features of the proposed technique are detailed through the modeling of an iris-like discontinuity. Moreover, this technique is validated by modeling substrate integrated waveguide filters, whose frequency response is compared with numerical and experimental results. The proposed method can be adopted to obtain libraries of parametric models of substrate integrated waveguide discontinuities, which can be included in computer aided design tools. The multimodal parametric model of an iris-like discontinuity is presented and discussed. C 2008 Wiley Periodicals. Inc. Int J RF and Microwave CAE 19: 423-433,2009.