WIRELESS POWER TRANSMITTER, WIRELESS POWER RECEIVER, AND WIRELESS POWER TRANSFER SYSTEM

A wireless power transmitter includes an antenna that transmits a radio wave, a phase shift circuit that changes a phase of the radio wave transmitted from the antenna, a control device that controls the phase shift circuit, and a backscatter signal receiver that receives a backscatter signal. The control device executes phase optimization processing of controlling the phase shift circuit so that a strength of the backscatter signal received by the wireless power transmitter is maximized.