RCS Reduction and Gain Enhancement for the Circularly Polarized Array by Polarization Conversion Metasurface Coating

High-gain, low-profile circularly polarized (CP) array with low radar cross section (RCS) is proposed based on the ultrawide band (UWB) polarization conversion metasurface (PCM) coating. A chessboard-like coating is formed by a mess of arrow-shaped PCM elements that have UWB and high polarization conversion ratio. The coating is distributed beneath the dipoles, behaving as a reflector. With the PCM beneath each dipole, the CP radiation is achieved and enhanced in a low profile by the radiating wave and the reflected wave, which have equal amplitude and 90 degrees phase difference. With the chessboard-like coating, the incident wave is converted into the equal amplitude and out-of-phase reflected waves, which will cancel each other to reduce the backward scattering. The performances of the array are validated by both simulations and measurements. The results show that the left-hand CP radiation is achieved in 11.25 to 12.31 GHz with the RCS being reduced for more than 4.8 dB in 10.5 to 35.1 GHz.