Superior Circularly Polarized Antenna via Spin-Momentum Locking

Circularly polarized (CP) radiation is critical in modern wireless communications and radar systems, yet conventional CP antenna designs are often constrained by limited tunability, structural complexity, and high sensitivity to minor deviations. A generalized methodology for realizing high-purity CP radiation is presented, leveraging the spin-momentum locking phenomenon inherent to evanescent waves. By engineering an efficient coupling mechanism facilitating radiation from spoof surface plasmons, this approach circumvents the structural complexities and potential sensitivities inherent in many conventional CP antenna designs. To validate this concept, a low-profile CP antenna is proposed to validate the method, and a systematic exploration of structural configurations provides insights into optimizing gain enhancement or polarization purity. Simulated results demonstrate high-purity CP radiation across 13.4-14.0 GHz, with an average axial ratio (AR) of 1.48 dB and a minimum AR of 0.25 dB. Experimental results confirm these findings, yielding an average AR of 0.99 dB, significantly outperforming existing designs. Furthermore, the antenna architecture demonstrates robust polarization fidelity during beam scanning. This work establishes a paradigm for developing simplified yet high-performance CP antennas, grounded in fundamental wave physics, with significant implications for advanced wireless communication and radar systems.