Highly efficient wireless power transfer using metamaterial slab with zero refractive property

A highly efficient wireless power transfer using a metamaterial slab with a zero refractive property is proposed. The proposed metamaterial slab consists of a spiral structure, a lumped element and a via through the ground. A prototype of a wireless power transfer system and a metamaterial slab was designed and fabricated. Experiment results prove the transfer efficiency improvement with the proposed metamaterial slab. The power transfer efficiency is improved by reducing the radiation loss through focusing the magnetic field. The power transfer efficiency is above 45% at a distance of 100-150 mm, and the resonant frequency is 6.78 MHz. The sizes of the transmitting coil and the metamaterial slab are 140 x 210 mm and 50 x 70 mm, respectively.