Metasurface for Near-Field Wireless Power Transfer with Reduced Electric Field Leakage

Abstract

Wireless power transfer is a breakthrough technology which can be used in all aspects of humans daily life. Here, a bi-layer metasurface as a transmitter for near-field wireless power transfer is proposed and studied. The novelty and advantage of the proposed metasurface is the spatial separation of the electric and magnetic near fields. Magnetic fields responsible for power transfer are sufficiently high on top of the metasurface whereas the electric fields are almost completely confined between two layers of the metasurface. These unique properties have been obtained due to the special metasurface design based on two orthogonal layers of resonant wires immersed in high-permittivity background. The theoretical and experimental study reveal the quasi-uniform magnetic field distribution over the metasurface dimensions of $40\times 40$ cm2 that makes it suitable for wireless power transfer via resonant magnetic coupling to one or several receivers placed above it. Compared with a conventional planar spiral coil solution, the specific absorption rate of the proposed metasurface is reduced by 47 times, which enables to greatly increase the allowable transferred power without violating the safety regulation and reducing the efficiency.