An Ultrawideband Omnidirectional Circularly Polarized Antenna Enabled by Metasurface Integrating Dielectric Polarizer

In this letter, an omnidirectional circularly polarized antenna (OCPA) that operates across Ku band and K band is proposed. A metasurface whose phase difference decreases monotonically with increasing frequency is utilized to compensate for the slope of traditional dielectric polarizer's phase difference, forming a metasurface integrated dielectric polarizer (MIDP). Hence, a stable 90° phase difference level can be maintained across a wide frequency range, contributing to broadband omnidirectional circular polarized (CP) radiation. The proposed design yields an obvious advantage when compared with recently reported OCPA designs in terms of CP bandwidth while keeping a similar size. For validation, a prototype based on the concept above is designed and fabricated. It mainly consists of two parts: a biconical feed and the proposed MIDP. The measured results show that the antenna yields an overlapped bandwidth of 66.7% (70% impedance bandwidth and 66.7% axial ratio bandwidth).