Hybrid-mode analysis of a broadside-coupled microstrip line

The purpose of the paper is to present a hybrid-mode analysis for obtaining dispersion characteristics of a broadside-coupled microstrip line. A characteristic equation for a propagation constant is derived via Galerkin´s method in the Fourier-transform domain. It is shown that the dependence of the solution on the basis functions is small. Computed effective dielectric constants in the low-frequency region agree well with other investigators´ numerical results, which are based upon the quasi-TEM method. Finally, dispersion characteristics, which are important in practical design, are demonstrated.