Broadband low-profile and Low-RCS circular polarization metasurface antenna based on hybrid mechanism with characteristic mode analysis

In this letter, we present a broadband low-profile and low-RCS circularly polarized (CP) antenna, comprising three layered integrated components: metasurface (MS) layer based on a centrosymmetric architecture with dual-effect control components, an absorbing layer featuring four disk-shaped patches, and an aperture-coupled feed network, which are separated by dielectric substrates. These dual-effect control components simultaneously broaden the CP bandwidth by indirect mode suppression and achieve RCS reduction via phase-cancellation effects. An aperture-coupled feeding structure, implemented with microstrip lines and an L-shaped slot, is employed to excite two orthogonal modes with a 90^° phase difference, thereby achieving CP radiation. Then, leveraging the hybrid mechanism of phase cancellation and absorption, an absorbing layer is employed to further attenuate the RCS. Finally, a low-profile CP antenna with dimensions of λ₀×λ₀×0.075λ₀ at 5 GHz is successfully designed, fabricated, and experimentally validated. The experimental results demonstrate that the measured 3 dB axial ratio (AR) bandwidth of the MS antenna spans from 3.78 GHz to 6.41 GHz, covering 51.7 % of the frequency range. The corresponding impedance bandwidth ranges from 3.82 GHz to 6.38 GHz, achieving 50.2 % bandwidth. Furthermore, the MS antenna exhibits a 10 dB RCS reduction bandwidth from 6 GHz to 8.91 GHz, representing 40 % of the frequency range. The peak gain is measured at 13.1 dBic at the center frequency of 5.8 GHz.