TRANSVERSE RESONANCE, STANDING WAVE, AND RESONATOR FORMULATIONS OF THE RIDGE WAVE-GUIDE EIGENVALUE PROBLEM AND ITS APPLICATION TO THE DESIGN OF E-PLANE FINNED WAVE-GUIDE FILTERS

An accurate computer-aided design of compact, low-cost, low-insertion-loss evanescent-mode waveguide bandpass filters with bilateral metallic E-plane fins is presented. The rigorous field distribution of the ridge waveguide eigenmodes is applied to the design. The design theory takes into account the influences of both the finite fin thickness and the higher-order mode interaction at all discontinuities. The numerical advantage of the transverse resonance method for solving the related cross-sectional eigenvalue problem is demonstrated for the design of quasi-high-pass and bandpass filters of different ridge gap widths and is compared with the classical standing wave and resonator mode-matching techniques. Computer-optimized design data are given for filters with passbands in X-band (8-12 GHz) and E-band (60-90 GHz), which achieve high skirt selectivity and wide stopband. The theory is verified by measurements.