Design of Filtering Antenna Using Half-Mode Substrate Integrated Waveguide Technology

A low-profile filtering antenna using half-mode substrate integrated waveguide (HMSIW) is proposed. The filtering antenna consists of three parts: a half-mode substrate-integrated cavity (HMSIC), a rectangular patch, and two pairs of shoring vias. The HMSIC is employed as the first stage resonator, and the rectangular patch is utilized as the last stage resonator as well as the radiator. The rectangular patch is placed close to the HMSIC for bandwidth enhancement and filtering performance improvement. Two radiation nulls are observed at both lower and upper band-edges, leading to achieving high out-of-band selectivity. The optimized filtering antenna was fabricated by standard printed circuit board (PCB) technology and tested. It demonstrates a low profile $0.015\ \lambda_{0}$ , and compact size $0.73\ \lambda_{0}\times 0.49\ \lambda_{0}$ . The measured results, which agree well with simulated ones, exhibit a fractional bandwidth of 5.1%, a maximum realized gain of 6.3 dBi, and a flat passband gain response along with good out-of-band rejection.