In this paper, a novel wideband high-gain and low scattering antenna using shared-aperture metamaterial superstrate (SAMS) is designed, fabricated and measured. The superstrate unit cell consisting of two frequency selective surface (FSS) layers with a positive reflection phase gradient is designed to enhance the antenna gain. Then, three different sizes of single units are arranged as a shared-aperture configuration to form the metamaterial superstrate, which is loaded onto the antenna. By

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... izing the phase compensation property along different units, the antenna gain enhancement bandwidth is effectively broadened. By adjusting the SAMS loading height, the antenna radar cross section (RCS) is also reduced obviously owing to the different reflective wave phases of PRS and antenna ground. After loading SAMS, the antenna possesses an impedance bandwidth of 44.7% from 7.8 GHz to 12.3 GHz, covering the whole X band. From 7.9 GHz to 12.1 GHz, the antenna has an obvious gain enhancement, with a peak of 7 dB, meanwhile, the antenna RCS is effectively reduced from 4 GHz to 12 GHz and the maximum RCS reduction reaches 25.4 dB at 8.6 GHz for x-polarized incident wave and 15.8 dB for y-polarized incident wave. The results are validated by both numerical simulation and experimental measurements.