Realization of Programmable Chessboard Mushroom-type Metasurface for Beamforming Applications

A reconfigurable microwave reflectarray metasurface (MS) is investigated for beamforming applications. The reflected beam direction is changed by applying external dc voltages, which create a reflection phase gradient on the structure. The studied MS comprises a chessboard-like array of metallic patches placed over a grounded dielectric slab with metallic vias connecting the patches to the controlling lines. Tunability is achieved with nonlinear capacitive loads (varactors) inserted between the corners of the metallic patches. The MS is studied analytically, numerically and experimentally, from which reshaping of the radiation pattern is observed according to the applied control voltages on the MS elements. The beamforming efficiency depends on the size of the MS and the beam width of the source antenna. It is shown that the proposed MS-based reflectarray with just 3-by-10 elements is already sufficient to redirect the beam in different directions.