Additively Manufactured and Monolithically-Integrated Triple-Mode Post-Loaded Cavity-Resonator-Based Bandpass Filters

This manuscript reports on a new class of triple-mode post-loaded cavity-resonator based bandpass filters (BPFs) alongside their design methodology and a monolithic integration scheme using stereolithography apparatus (SLA) 3D printing. The proposed BPF concept exhibits the following unique features: i) miniaturized size accomplished by combining three modes within the volume of a single post-loaded cavity resonator, ii) bespoke coupling element configurations that facilitate the realization of transmission zeros (TZs) in the out-of-band response and iii) monolithic SLA integration that further reduces the size and weight of the entire filter as opposed to conventional split-block manufacturing schemes. For proof-of-concept validation purposes, two three-pole/two-TZ BPFs and a six-pole/four-TZ BPF operating at 2.9 GHz, 3.2 GHz and 3.2 GHz with a fractional bandwidth (FBW) of 16.3%, 15.2%, 14.2% respectively, were designed, manufactured, and tested. They exhibited passbands with in-band insertion loss < 0.37 dB, that corresponds to an effective quality factor (
Q
_eff
s) > 780.