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 paper 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 LP and CP waves at incidence angles from normal to oblique, all while maintaining a 0.09 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{0}$</tex-math></inline-formula>. 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 13.1-23.5 GHz. The co-designed structure preserves circular polarization integrity and radiation efficiency from 10.48-13.46 GHz. Experimental validation demonstrates wideband RCS reduction by more than 4.5 dB is 96.8% (8.35-24 GHz). This work establishes a low-profile stealth antenna paradigm for conformal low-observable platforms.