Coupled-Mode Analysis of Line Parameters of Coupled Microstrip Lines - Abstract

Abstract

An approximate method to obtain the line parameters of multiple coupled microstrip lines based on the full-wave analysis is presented. The technique uses the coupled-mode equations for the amplitudes of currents on each line. The coupling matrix in the equations, expressed by overlap integrals between the eigenmode fields of each isolated single line, characterizes the electromagnetic natures of the coupled lines. The eigenvalues and eigenvectors of the matrix yield the propagation constants, the ratios of line currents, and the characteristic impedances of the coupled modes. The proposed method is applied to two nonidentical coupled lines and three nonidentical coupled lines in a single plane, and two identical coupled lines in dual planes. The numerical results for the mode propagation constants and characteristic mode impedances are compared with those obtained by the direct numerical solution method for the coupled lines. Both results show a good agreement.