Compact and low-cost topology for evanescent-mode waveguide filters with dielectric loading in the X Band

This work presents the design and implementation of a compact, three-pole, bandpass filter at 9.75GHz using evanescent-mode, quartz-loaded, rectangular-waveguide resonators arranged in a novel manufacturing topology. The simplicity of the proposed design results in a fast and low-cost manufacturing process, which is easily extendible for high-yield commercial deployment using wire electrical discharge machining. Additionally, a new figure of merit is introduced to compare the compactness and performance of the proposed filter to other cavity filters. Finally, measurements showed a center-frequency insertion loss of 0.53 dB, a 0.2 dB fractional bandwidth (FBW) of 5.9%, and a side-band rejection better than 20 dB at FBW = 25%. The prototype was realized in a brass housing that occupies a total volume of 8.27 cm³ (0.51 cubic inches).