Multibeam by Metasurface Antennas

We explore various possibilities for designing multibeam antennas using a single metasurface (MTS) aperture. Both single-source and multisource feeding schemes are considered. For the single-source case, two approaches are investigated. In the first one, the MTS aperture is divided into several angular sectors, each one devoted to the formation of a beam in a given direction. In the second approach, the whole aperture is shared by a superposition of individual modulations, which correspond to those required to obtain beams in the desired set of directions. It is shown that the latter solution provides beams with a higher gain. The configuration based on a multisource feeding scheme is also tailored by a superposition of modulation patterns. The main advantage of the latter approach is the possibility of having one independent beam at a time when each of the sources are active, as opposed to the single-source case where all the beams coexist at the same time. Closed-form expressions are provided for the MTS surface impedance in each of the proposed solutions. The design equations include appropriate amplitude tapering to improve the beam efficiency. Numerical results based on the method of moments are presented for validation.