Equivalent Circuit Modeling of Coupled Line Discontinuities for Multi-Section Stripline Coupler

Abstract

Offset broadside coupled lines are widely used in directional couplers and quadrature hybrids. Ideally, these lines can achieve good isolation characteristics, but in the case of multi-section lines, the characteristics deteriorate due to the effect of junction discontinuities between lines. We propose a novel equivalent circuit model of junction discontinuities and a method for extracting equivalent circuit constants to understand this effect and design a compensating structure accurately. Using this proposed method, we modeled a multi-section quadrature hybrid coupler. We constructed a circuit model of the multi-section quadrature hybrid that agrees well with the results of full-wave electromagnetic(EM) simulations. This method enables simple and efficient structural design of complex circuit structures with multi-section coupled lines that require several hours or more for EM simulation.