Evanescent mode triple ridge lowpass harmonic filter

Abstract From the Canadian patent

A waveguide lowpass filter has successive groups of three separate ridges spaced longitudinally in said filter. A centre ridge of each filter has a larger cross-sectional area than two side ridges which are the same size. All ridges are parallel to one another in a longitudinal direction. The groups are associated with shunt capacitances and the spaces between adjacent groups are associated with series inductances in an evanescent mode. In operation, the filter is capable of supporting a TE10 mode in the passband and three modes, TE10, TE20 and TE30 in the stopband. The filter has a relatively high power handling capability as compared to previous evanescent mode lowpass harmonic filters.