Ultrabroadband RCS Reduction and Gain Enhancement of Patch Antennas by Phase Gradient Metasurfaces

In this letter, a novel design based on phase gradient metasurfaces (PGMs) is proposed to reduce the radar cross section (RCS) and enhance the gain of patch antennas. The PGM unit consists of a cross-dipole and three square-dipole rings. The proposed antenna is composed of a conventional patch radiator and four surrounding sequential-rotated PGMs. On the one hand, an ultrabroadband RCS reduction is achieved due to the PGMs phase discontinuity deflects the signal away from the specular direction by the PGMs. On the other hand, a gain enhancement is achieved because the enlarged equivalent radiation aperture owing to the coupling effect between the PGMs and the patch. A prototype operating at Ku band is designed, fabricated, and measured. It is demonstrated that an over 6 dB RCS reduction is obtained from 9.31 to 28.22 GHz, and an average 1.5 dB gain enhancement is obtained within the working band of 14.2-15.5 GHz, which can be used in stealth platforms.