Suppressing Grating Lobes in a Transmitting All-Metal Phase-Gradient Metasurface

Radiofrequency (RF) transparent all-metal phase-gradient metasurfaces (PGMs), which are essential components for implementing an all-metal Near-field Meta-Steering (NFMS) antenna system, introduce undesired dominant grating lobes that severely restrict their potential applications. This study reveals a practical method to identify and suppress unwanted grating lobes. First, the dominant propagating modes are determined by analyzing the floquet modes, and then the undesired grating lobes are reduced by applying an evolutionary algorithm. The concept is validated through full-wave numerical simulations by designing four-layered metallic meta-atom and supercell. The present research shows that it is feasible to suppress the grating lobes significantly, indicating the promising potential of all-metal PGMs as a building block for fully metallic beam-steering antenna systems.