Analysis on scattering parameters for coupled microstrip lines with bend discontinuities

In this paper, we propose a method to analyze the scattering parameters for coupled microstrip lines with bend discontinuities. The key idea of the proposed method is to analyze the coupled bends and parallel coupled lines individually. Specifically, the equivalent π circuit model is built to approximate coupled bends and the corresponding scattering matrix is obtained by converting Z-matrix; the scattering matrix of parallel coupled lines is acquired by the odd-even mode theory. Then, we can compute the scattering parameters of the coupled microstrip lines with bend discontinuities based on the cascade property of transmission matrix, which is transformed from the scattering matrix. The agreement between theoretical results and simulation results shows the effectiveness of the proposed method. Moreover, the method avoids complex mixed integral operations and provides guidance for designing bent coupled microstrip lines.