Design of circularly polarized spin-multiplexed multibeam metasurface for satellite communications

To address the issues of limited coverage area, low spectral efficiency, and susceptibility to polarization mismatch in transmission with traditional single-beam, linearly polarized antennas, a circular polarization spin-multiplexed multi-beam metasurface capable of suppressing polarization deviation and improving spectrum utilization efficiency is proposed in this paper. The unit consists of a resonant metallic ring and a cross-shaped slotted metallic patch. By adjusting the arm length and rotation angle of the slotted cross-shaped structure, a 360° range of geometric phase and resonant phase shift is achieved. Based on the spin-decoupling principle and the electric field superposition theorem, a 40 × 40 circular polarization spin-multiplexed multi-beam metasurface array was designed. A linearly polarized patch antenna was employed as the feed for co-simulation and experimental validation. The results demonstrate that, within 28.8–31.2 GHz, the metasurface converts linearly polarized waves into dual circularly polarized quad-beams transmitted at different angles, with an axial ratio below 2 dB. The dual-beam amplitude ratio for LHCP and RHCP closely aligns with the preset value of 1:0.9. The proposed unequal-gain circular polarization spin-multiplexed multi-beam metasurface provides two independent orthogonal circular polarization transmission channels, thereby significantly improving spectral efficiency and anti-interference capability in satellite communications.