Wireless Power Transmission System Based on Phase Conjugation

In this paper, a retro-reflective beamforming system for microwave wireless power transmission based on rotating-element electric-field vector (REV) method is implemented and experimentally studied. The wireless power transmitter consists of a four-channel integrated transceiver in the 2.45GHz frequency band. In the retro-reflective beamforming, the wireless power receiver (target) first broadcasts a continuous-wave pilot signal. The four receiving channels of the transmitter combine the received pilot signal, each with a phase delay that can be tuned independently. By optimizing the phased delays of the receiving channels with a phase searching algorithm based on the REV method, the phase distribution of the pilot signal arriving at the four elements of the antenna array is obtained. Then the four transmitting channels of the transmitter are fed with a phase distribution conjugate to that of the received pilot signal, which successfully focuses the power at the target.