Efficiency Improvement of 6.78MHz Metamaterials for WPT System

There are many applications for wireless power transfer (WPT), but as the transmission distance increases, the magnetic field energy decays and the transmission efficiency drops sharply. In this paper, a focused electromagnetic metamaterial (MM) unit is designed. When the operating frequency is 6.78 MHz, the permeability of the metamaterial unit is negative, and the purpose of focusing the magnetic field is achieved. The WPT system using a 3$\times$ 3 array metamaterial was established. Through simulation, the magnetic field diagram and transmission efficiency of WPT system with metamaterial slab varying different transmission distances are obtained. The magnetic field around the Rx coil is significantly improved after adding the MM slab. When the transmitting and receiving coils are 20cm apart, the transmission efficiency of the system is improved the most with 41.03%.