A 13.56 MHz antenna design with the efficiency improvement for the wireless power transfer system

Wireless power transfer is the most convenient solution for the electric device charging. However, it still keeps a disadvantage such as the transfer distance is short which is the most difficult to eliminate. Moreover, the relative position of the transmitter and the receiver depends on the movement of the electric vehicles in the dynamic wireless charging. Therefore the average efficiency is low in the charging area when the electric vehicle runs away from the optimized position of the transfer system. In this paper, a 13.56MHz antenna is designed by the finite element analysis. At the highest efficiency, the transfer distance is 55 cm. Otherwise, the solution to improve efficiency due to the variation of the charging position is proposed. The coupling system is strongly coupled magnetic resonance technology. The impedance is dynamically matched in the transmitter to improve the transfer efficiency. In the simulation, the 91.2% highest efficiency at 55 cm is obtained and it is improved maximum of 56.4% within 55 cm transfer distance and 40 cm misalignment with the proposed solution. The experimental system can improve efficiency depending on the position of receiver and lookup data.