High-Performance 45° Slant-Polarized Omnidirectional Antenna for 2–66-GHz UWB Applications

The development of a 2–66-GHz ultra-wideband 45° slant-polarized omnidirectional antenna (SPOA) is described. The antenna is radome enclosed and consists of a wideband biconical antenna that provides omnidirectional radiation patterns with vertical polarization and a multiscreen polarizer that converts vertical polarization into 45° slant-polarization. To achieve high-performance radiation characteristics, the geometrical dimensions of the multiscreen polarizer are optimized. Invasive weed optimization algorithm is used as an optimizer tool. In the optimization procedure, the antenna impedance bandwidth, pattern ripple in the azimuth plane, and copolarized gain/cross-polarized gain ratio are optimization goals. A prototype of the 45° SPOA is fabricated and measured. The measured voltage standing wave ratio (VSWR) of the antenna is less than 2.15. Moreover, experimental results show that pattern ripple in the azimuth plane is lower than
$\pm {1}\,{\text{dB}}$
, and copolarized gain/cross-polarized gain ratio is higher than 26 dB, over 2–40-GHz frequency band. The efficiency of the fabricated antenna both in bandwidth and optimality of the results is compared with a number of commercially available wideband 45° SPOAs. Comparison results show that the designed antenna outperforms other 45° SPOAs.