Monolithic SLA-Based Capacitively-loaded High-Q Coaxial Resonators and Bandpass Filters

This paper discusses the design, manufacturing and testing of additively-manufactured coaxial resonators and filters with high unloaded quality factor (Qu). A stereolithographic (SLA)-based integration concept that facilitates the realization of monolithic 3D printed coaxial-resonator-based bandpass filters (BPFs) is explored in detail. In particular, we present a study on alternative resonator sizes and non-radiating perforations for monolithic coaxial resonators and BPFs in the frequency range of 1-12 GHz. The applicability of the SLA-based concept to complex frequency-dependent couplings is also explored with the purpose of enhancing the BPF's out-of-band rejection. For proof-of-concept demonstration, various resonator and BPF prototypes - with and without frequency-dependent couplings - were designed, manufactured and measured. They exhibited Qu between 1638-3520 and passbands centered at 5 GHz with fractional bandwidths between 13-14.2% and insertion loss < 0.35 dB.