Analysis of Electrical Characteristics of Edge-Coupled Microstrip Lines with a Dielectric Overlay

摘要

An analysis was performed of the electrical characteristics of edge-coupled microstrip lines with a dielectric overlay. This analysis is applicable to the design of broadband directional couplers, filters, and Schiffman phase shifters for microwave integrated circuit applications. The analysis incorporated an even- and odd-mode treatment that invokes a quasi-TEM propagation model. This treatment enabled the analysis to be formulated in terms of integro-differential equations involving equivalent sources at conductor and dielectric boundaries. The formulation was reduced to a form suitable for numerical solution by employing a method-of-moment solution with pulse expansions of equivalent sources and point matching of the boundary conditions. The analysis was implemented by a digital computer program that provides information on midband coupling, modal impedances, coupled line characteristic impedance, modal phase velocities, and coupled line phase velocities.