Robust Wireless Power Transfer Based on a Needle Beam Generated by a Transmissive Metasurface

To achieve a long-distance robust wireless power transfer (WPT) in the microwave band, a transmissive metasurface that can tightly focus vector beams is presented in this paper. We first design a unit cell that can independently and simultaneously control the phase and polarization of the transmitted wave. Then, a metasurface is constructed by the designed unit cell according to the required polarization and phase distribution. Finally, a focused needle beam with a small full-width at half-maximum (FWHM) is obtained. The needle beam is non diffractive in a distance about $3.8\ \lambda$ , which is suitable for robust WPT. The proposed design method paves a new way for the WPT systems based on vector beams.