Method to Reduce Metal Plate Effect Between Transmitter and Receiver in Wireless Power Transfer System

In this letter, the shape of a metal plate is proposed in a way to maximize the transmission efficiency when a metal plate is placed between transmitter and receiver in the wireless power transfer system. In case of the metal plate having slots, electromagnetic waves can penetrate into the metal plate if the direction of the slots is same as the direction of the magnetic field. Unit cell simulation is performed to investigate the relation between the transmission coefficient and the slot width. As a result, electromagnetic waves demonstrated it can penetrate through a very small slot of 0.1 mm. Based on the simulation results, a metal plate with slots in the same direction as the magnetic field generated by the receiving coil is designed. The efficiency of the wireless power transfer system is increased in line with the increase in slot width of the metal plate. Two types of slot width 0.1 and 1 mm are fabricated, and the efficiencies are measured. As a result, the efficiencies are 71% at 6.78 MHz and 81%, respectively.