Design of Near-Field Focused Metasurface for High-Efficient Wireless Power Transfer With Multifocus Characteristics

This paper presents a new design of near-field focused metasurface for high-efficiency wireless power transfer with multifocus characteristics. A general synthesis procedure is outlined to design metasurfaces with desired multiple foci in the near-field zone. The unit cell of printed tridipole is used to realize the focused metasurface which has a large range of phase shift and is adapted to near-field focusing applications. Different feeding and focusing designs of the printed tridipole metasurfaces are proposed and analyzed. Two kinds of metasurfaces with 20×20 elements are designed, fabricated, and measured at 5.8 GHz. One is the single-feed and single-focus case, and the other is single-feed and two-focus case. Two-dimensional planar near-field scanning technique is implemented to measure the E-field focusing characteristics. Full-wave simulations and experiments demonstrate that the proposed focusing metasurfaces have a high wireless power transfer efficiency of 70%. The relative bandwidth with 50% power focusing efficiency is about 16%. The measured results are in good agreement with the theoretical designs and simulated results, which verify the feasibility and correctness of the proposed approach in this paper.