Modeling of Inhomogeneous and Lossy Waveguide Components by the Segmentation Technique Combined With the Calculation of Green’s Function by Ewald’s Method

This paper presents a novel algorithm for the analysis of piecewise homogeneous, possibly lossy, waveguide circuits. The algorithm is based on the segmentation technique to split the circuit into homogeneous building blocks, combined with the representation of the generalized admittance matrix (GAM) of each block by the boundary integral-resonant mode expansion (BI-RME) method. The GAMs are then recombined by a circuital cascading procedure. The core of the method is the calculation of the quasi-static Green's function of a rectangular box, which is required to determine the terms of the BI-RME pole-expansion of the GAM. The expressions of the quasi-static Green's function, manipulated by Ewald's technique to improve the convergence, are fully described, and numerical considerations for their efficient and accurate calculation are provided, with a particular focus on the proper selection of the splitting parameter. To demonstrate the correctness of the given formulas, the algorithm is developed and applied in the limited case of circuits segmentable into boxed building blocks. Numerical examples demonstrate the accuracy and efficiency of the proposed technique.