Ultrathin Low-RCS Circularly Polarized Antenna Using 2-Bit Hybrid Metasurface Optimized by Genetic Algorithm

To address the requirements of stealth platforms for low-profile antennas, this letter proposes an ultrathin low-scattering circularly polarized (CP) slot array by integrating with a genetically optimized 2-bit phase gradient metasurface (PGM). This approach achieves broadband RCS reduction (both in-band and out-of-band) under far-field illumination. The performance is robust for both linearly polarized (LP) and CP waves at incidence angles from normal to oblique, all while maintaining a 0.09λ₀ low profile. Compared to periodic counterparts, the genetically-optimized aperiodic topology improves RCS reduction bandwidth and impedance bandwidth, with the bandwidth of RCS reduction of more than 8 dB is 13.1 GHz to 23.5 GHz. The co-designed structure preserves circular polarization integrity and radiation efficiency from 10.48 GHz to 13.46 GHz. Experimental validation demonstrates wideband RCS reduction by more than 4.5 dB is 96.8% (8.35 GHz to 24 GHz). This work establishes a low-profile stealth antenna paradigm for conformal low-observable platforms.