Rigorous analysis of triple-ridge waveguides

A complete eigenvalue solution is presented for a triple-ridge waveguide which yields the cut-off frequencies of dominant and higher-order modes as a function of the geometrical parameters of the guide. The electromagnetic field distribution is determined in the waveguide cross-section allowing the calculation of the dominant mode impedance. The Ritz-Galerkin method is used for the numerical calculations, and edge effects are taken into account in the basis functions toaccelerate the convergence. This method can be applied to multiridge waveguides with an arbitrary disposition of ridges.