Modulated Metasurface Antenna for Straight-Line Flat-Top Beamforming With Shared Aperture

In this letter, a fan-shaped aperture-modulated metasurface antenna (MMA) is proposed for straight-line flat-top beamforming at a specified elevation angle. The desired beam pattern is decomposed into multiple adjacent sub-beams, implemented via a multibeam shared-aperture technique. Unlike conventional circular or rectangular apertures, the fan-shaped design effectively suppresses beam splitting within a 7% relative bandwidth. Mushroom-shaped electromagnetic bandgap structures are introduced at the aperture edges to reflect surface waves, thereby reducing sidelobes. Global optimization of the unit cell geometries further enhances antenna gain, achieving a uniform flat-top pattern. A prototype operating at 15 GHz demonstrates a measured peak gain of 17.3 dBi with a flat-top pattern having a 2 dBi gain variation range of about 45°, showing good agreement with the simulation results.