Ultra-wideband RCS Reduction of Patch Antenna Using Phase Gradient Metasurface

Radar cross section (RCS) reduction of microstrip antennas is crucial for stealth applications, however, most existing methods suffer from limited bandwidth or degraded radiation performance. In this work, a novel patch antenna integrated with a phase gradient metasurface (PGM) is proposed to achieve ultra-wideband RCS reduction without compromising radiation characteristics. The antenna adopts a multilayer stacked configuration, in which an embedded probe feed excites the radiating patch via interlayer electromagnetic coupling. The PGM unit consists of five layers, with square metallic patches of varying sizes placed on the first and third layers. By adjusting the patch dimensions, three unit cells with broadband phase modulation are achieved. These are arranged in a clockwise-rotated 6 × 6 array around the patch antenna. Simulation and measurement results confirm that the PGM integration maintains stable radiation performance, with a measured 10-dB impedance bandwidth of 14.8% (19.55-22.67 GHz), gain between 6.51 and 7.67 dBi, and stable radiation efficiency and radiation patterns. Meanwhile, the PGM introduces phase discontinuities to redirect incident waves away from the specular direction, achieving RCS reduction greater than 10 dB over 8.2-10.5 GHz and 12.5-27.5 GHz (96.92%). Experimental results agree well with simulations, validating the proposed design's dual-functionality for radiation and scattering control.