Two-Stage Passive Impedance Matching Network With Frequency Modulation Strategy

The mismatched impedance for PA caused by coil misalignment or load change, affects the efficiency of the wireless power transfer (WPT) system. In this paper, based on the narrowband frequency modulation, a two-stage passive matching network is proposed, which can match the varying load to the characteristic impedance of the PA. The limitation of a single T-network in frequency modulation is analyzed while the reactance nulling network and resistance conversion network are introduced. The detailed design method and frequency selection strategy are presented. To verify the feasibility of the network, the example matching network is designed for inductive loads, and a 1000W prototype is built with a reflected coefficient of less than 0.2.