Phase-Only Beam Forming Method Based on Digital Code Metasurface

In this article, a phase-only beam forming method based on digital code metasurface (DCM) is proposed for sidelobe level suppression. First, a joint magnitude-and-phase equivalent model is established for a 2-bit DCM by using space-time-coding. The proposed scheme is devoted to forming the relative reflective magnitudes between metasurface units to fit special weights, which addresses the problem that the traditional phase-only metasurface can only modulate the reflective phase. Compared with the preparation of unequal-magnitude metasurface units in hardware, the proposed strategy can achieve an improved weight-fitting effect while keeping the low system complexity. Numerical simulations have illustrated that the peak sidelobe level can be maximally suppressed from about -10 dB of the conventional 2-bit metasurfaces to about -28.5 dB with the set Dolph-Chebyshev weight of -30 dB. The results are discussed in different situations, such as the length of time sequences, beam scanning, and 2-D beam forming. Moreover, the proposed equivalent model and corresponding optimization method are also applicative for other special array weights to achieve diverse functions, which have potential performance improvements in radar detection and wireless communications.