Broad passband, wide stopband, high power evanescent mode filters using capacitively-loaded ridges

This paper presents advanced structures that extend the class of capacitively-loaded evanescent mode filters and mitigate some of the limits that are common for this technology. Innovative design details and modifications with respect to a conventional structure are properly applied so as to improve the filter performance when high power, broad passband, and wide stopband are all required at relatively high frequency. The proposed structures combine coaxial capacitance based resonators with evanescent mode ridged waveguide sections so as to obtain capacitively-loaded ridge waveguide bandpass filters. The approach is validated by the design and experimental results of two X- and Ku-band filters. Particularly remarkable are the performance of the Ku-band filter, which has a wide passband from 12 to 18 GHz, a wide stopband up to 54 GHz, and which successfully handled 100 W of continuous power.