Dual-circularly Polarized Metasurface Antenna Design

Dual-circularly polarized antennas are widely used in the field of wireless communication due to their advantages of effectively reducing multipath effects, reducing polarization losses and increasing channel capacity. In this paper, a dual-circularly polarized metasurface antenna is proposed and it provides a design procedure for modifying the metasurface structure to achieve circular polarization performance. Firstly, the physical properties of the original metasurface structure are analyzed using characteristic mode analysis. Based on the distribution of characteristic currents, the metasurface structure is modified to obtain two degenerate characteristic modes within the operating frequency band. Secondly, cross-shaped microstrip feedlines are strategically positioned and fed using slot-coupling to excite the two degenerate modes with a phase difference of 90 degrees and equal excitation amplitudes, thereby achieving dual circular polarization radiation. The antenna exhibits a measured axial ratio bandwidth of 24.8% and 20.2% at the port-1 and port-2, respectively, indicating excellent dual circular polarization radiation. Additionally, both ports exhibit a stable radiation gain of around 5 dBi within the operating band.