An Azimuth Plane Omnidirectional Circularly-Polarized Antenna Mountable on Metal Platform

Developing omnidirectional circularly-polarized antennas that can be installed on metal platforms such as vehicles and aircraft presents significant challenges. In this paper, an omnidirectional circularly-polarized antenna consists by a metal cavity and metal ground is proposed. Specifically, the vertical-polarized electric field component is generated by a thin open cavity positioned above the metal platforms with small gap. The horizontal-polarized component is produced by equivalent magnetic current at the cavity opening. To maintain consistent amplitude levels for tow polarization components, some slots are etched into the metal cavity to facilitate omnidirectional circularly-polarized functionality. The proposed antenna achieves a gain variation of less than 2 dB and radiates circularly-polarized waves in the entire azimuth plane. Owing to its omnidirectional and miniaturized characteristics, the antenna holds potential for applications in wide-angle scanning arrays in future work. The antenna offers the advantages of omnidirectional circularly-polarized radiation and isotropic radiation, making it suitable for low-altitude platforms, such as unmanned aerial vehicles (UAVs).