Compact and Wideband Millimeter-Wave 3D Printing Filtering Antenna with High Selectivity Based on Half-Mode Groove Gap Waveguide

This letter presents a compact and wideband millimeter-wave 3-D printing filtering antenna with high selectivity based on half-mode groove gap waveguide (HM-GGW). To begin with, a fifth-order bandpass filter (BPF) is developed using two HM-GGW resonators (HM-GGWRs) and three iris resonators. Four flexible transmission zeros (TZs) are generated by cross coupling and bypass coupling. The number and positions of the TZs can be elaborately adjusted by a disturbed pin on the metal cover plate. Then, based on the reflection coefficient matching principle, the second port of the original BPF is replaced with a stepped open-ended waveguide, and finally, a filtering antenna is realized, inheriting all the favorable performance characteristics of the BPF. For verification, a fifth-order filtering antenna prototype working in the Ka band is fabricated by 3-D printing technology. The prototype achieves a −10 dB IBW of 24.2% (ranging from 24.8 GHz to 31.62 GHz), features four adjustable radiation nulls (RNs), and exhibits a peak gain of 10.1 dBi along with a peak total efficiency of 97% across the entire operating band.