Frequency-Tuning Method Using the Reflection Coefficient in a Wireless Power Transfer System

In this letter, we compare two operating frequency tuning methods—the zero phase angle (ZPA) and the minimum reflection coefficient magnitude (MRCM) frequency tuning methods—to enhance the power transfer efficiency and output power in the wireless power transfer (WPT) system. For the MRCM frequency tuning method which has been introduced recently, the WPT system can be analyzed by considering the system as a matching network connected to a generator and a load. Through experiments, in the over-coupled region, the MRCM frequency tuning method has higher output power and efficiency than the ZPA frequency tuning method. Above all, the MRCM frequency tuning method does not need the information on the coupling coefficient as well as the primary and secondary resonators.