Broadband high-gain circularly polarized antenna based on reflective linear-to-circular polarization conversion metasurface

Abstract This paper presents the design of a novel reflective linear-to-circular polarization conversion metasurface (PCM) and its application to a wideband high-gain circularly polarized (CP) antenna. The proposed PCM efficiently converts incident linearly polarized (LP) waves into CP waves within an ultra-wideband range of 11.8–28.6 GHz, thereby laying a solid foundation for the design of the wideband CP antenna. By adding an LP microstrip antenna as the feed source above the PCM, the metasurface leverages its polarization conversion capability to reflect CP waves, simultaneously enhancing the antenna gain, and thus yields a wideband high-gain CP antenna. The designed CP antenna exhibits an impedance bandwidth and a 3 dB axial ratio (AR) bandwidth both spanning from 13.2 to 18.6 GHz, corresponding to a relative bandwidth of 34%. Notably, the 3 dB AR bandwidth perfectly matches the impedance bandwidth. Meanwhile, the antenna maintains a stable high gain exceeding 11 dBi across the entire operating bandwidth. Excellent agreement is achieved between the measured and simulated results, confirming that the proposed antenna simultaneously achieves a wide CP operating bandwidth, full-band 3 dB AR coverage, and high gain. Such characteristics make it highly valuable for potential applications requiring both wideband CP operation and high gain, such as microwave communications, precision radar, and satellite navigation systems.