2-D Beam Scanning Multi-Beam Antenna Based on Rotman Lens and Mechanical Sweeping Metasurface

In this paper, a compact multi-beam antenna is proposed with passive 2-D beam scanning capability. The antenna is composed of a Rotman lens beamforming network (BFN), a slotted waveguide array (SWA), and a mechanical sweeping phase gradient metasurface. The combination of the two orthogonal scanning beam ranges from the Rotman lens and the metasurface makes the proposed antenna achieve 2-D beam steering capability. To improve the crossover level (COL) and the sidelobe level (SLL) of the beams steered by the Rotman lens, the technology of dual sources excitation is used to increase the virtual source aperture size and the equivalent source number, optimizing the COL and the SLL by the tapered magnitude distribution. Numerical analysis and full-wave simulation are used to evaluate the performance variation of the different source aperture sizes. Since the large aperture of the SWA array can generate a quasi-plane wave above its radiation aperture, the metasurface can be fitted close to the SWA array with high spillover efficiency, resulting in a low antenna profile (<0.41 λ). The antenna can achieve ± 50° beam scanning range in the multibeam switching plane and ± 40° in the metasurface mechanical sweeping plane with the minimum COL of - 2.6 dB.