Quasi-Tem Analysis of Microwave Transmission Lines by the Finite Element Method

摘要

This paper describes a finite element approach to quasi-TEM analysis of several different types of isolated and coupled microwace transmission lines. Both the first and higher-order ordinary elements, as well as singular and infinite elements are used to solve for the potential and field distribution in the cross-section of the line. Next, the cross-sectional field distribution is inserted in a variational expression to compute the capacitance per unit length of the line and the effective e permittivity and characteristic impedance of the line are obtained from the capacitance value. A perturbationl approach is developed for estimating the losses due to conductor and dielectric dissipation and computing the attentuation constant. Lines treatable by this method may contain an arbitarty number of arbitrarily shaped conductors, including a system of conductors either placed above a single ground plane or between two parallel ground planes, and inhomogeneous dielectric regions that can be approximated locally by a number of homogeneous subregions. Keywords include: Microwave & millimeter waves; Digital circuits; Transmission lines; Characteristic impedance; Dielectric losses; Conductor losses; and Finite element method.