A High-Selectivity Filtering Antenna Based on Dual-Post Coaxial Resonators

In this communication, a compact waveguide filtering antenna is designed using dual-post coaxial resonators. The dual-post coaxial resonator consists of a pair of identical metal posts, capable of generating two resonant modes with identical and opposite electric field directions, respectively. The coupling post structure is employed to excite the two modes to achieve positive coupling and negative coupling. The combination of different dual-post coaxial resonators can be used to design higher order filters with transverse topology, realizing multiple transmission zeros. Furthermore, additional transmission zeros can be generated through direct coupling between the source and load, resulting in enhanced out-of-band rejection performance. A fourth-order waveguide filtering antenna is fabricated and measured, achieving high-selectivity performance.