A synchronous rectification-based PSK method is proposed for the receiver-to-transmitter communication in WPT systems.The communication can be used to provide a feedback path for the closed-loop control. The proposed method is to modulate the phase difference between the rectifier input voltage and thereceiver resonant current and demodulate the reflected phase difference between the inverter output voltage and the transmitter resonant current. The disturbances on power transfer caused by the PSK depend on the modulation depth, which can be minimized to reduce the disturbances. The communication method supports two encoding schemes: the binary encoding and the pulse frequency/width encoding. The data rate, pulse frequency, and pulse width are mainly limited by the operating frequency and coupling coefficient.