Efficient computation and orthonormalization of multiple TEM numerical modes arising from FEM for microwave computer-aided-design

摘要

Multi-conductor devices are very common in microwave engineering, such as in combline or interdigital filters. The electromagnetic fields in these devices involve multiple transverse electromagnetic (TEM) modes, which can be characterized by the Finite Element Method (FEM). This paper presents an efficient formulation not only to compute but also to subsequently orthonormalize these multiple TEM modes using FEM matrices and basis functions. This formulation can be used in computer aided design as an intermediate step between the transmission line analysis and the full-wave characterization with all higher-order modes, as it will be shown with a filter example.