Pin-Loaded Rectangular Hollow-Waveguide Cavities for Filter Design with Excellent Suppression of Spurious Passbands

Pin-loaded rectangular hollow-waveguide resonators for the realization of high-power filters in the mm-wave bands are investigated. Through the introduction of a conducting pin inside rectangular hollow-waveguide cavities, the first resonant modes are influenced in a way that improves the separation of modes. Using these resonators for filters, the advantageous larger dimensions of rectangular hollow-waveguide filters are combined with the excellent suppression of spurious passbands of other filter technologies like combline filters or evanescent-mode filters. The resulting filters do not only exhibit a wide stopband up to high frequencies, but also stand out through simplified manufacturing as well as improved power handling capabilities. The introduced filters, therefore, are highly suitable for applications in the mm-wave bands, which is demonstrated by the design and measurement of a prototype filter with a midband frequency of 35GHz with a bandwidth of 1GHz and a stopband reaching beyond 70GHz.