Hollow-Waveguide Horizontally Polarized Omnidirectional Antenna With Wideband and High-Gain Characteristics

A high-gain wideband horizontally polarized omnidirectional antenna (HPOA) based on the hollow-waveguide (HW) structure is investigated in this letter. The wideband parallel-plate waveguide (PPW) to single-ridge waveguide converter is first designed to achieve mode conversion from TEM mode to TE10 mode. By further integrating these converters with an axially-placed continuous transverse stub (CTS) radiating slot, stable high-gain horizontally polarized radiation is achieved. Multiple CTS radiating slots are arranged circumferentially to obtain good omnidirectional radiation properties. A compact center-excited annular PPW power divider serves as a feeding network to excite all CTS radiating slots to construct the complete HPOA. The antenna scalability can be realized by increasing the length of CTS slots and the scale of the feeding network to meet the gain requirements of different application scenarios. For demonstration, a prototype operating at 20-32 GHz is fabricated. The measured results indicate that good horizontally polarized omnidirectional radiation patterns with gain variation of less than 3 dB are obtained across the target frequency band.