Transverse Resonance, Standing Wave, and Resonator Formulations of the Ridge Waveguide Eigenvalue Problem and its Application to the Design of E-Plane Finned Waveguide Filters

Utilizing the rigorous field distribution of the ridge waveguide eigemnortes, this paper presents an accurate computer-aided design of compact, low-cost, low-insertion-loss evanescent-mode waveguide band-pass filters with bilateral metallic E-plane fins. 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 band-pass filters of different ridge gap widths and is compared with the classical standing wave and resonator modematching 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.