Wireless Power Delivery to Low-Power Mobile Devices Based on Retro-Reflective Beamforming

This letter presents an experimental study on wireless power delivery to low-power mobile devices based on retro-reflective beamforming. In our scheme, a pilot signal composed of an impulse train is broadcast from a mobile device. The pilot signal is received and analyzed by a wireless charger that includes four antenna elements. Then, according to the analysis outcome, the wireless charger constructs a focused power beam onto the mobile device. In our experiments, the total power transmitted from the wireless charger is approximately 1 Watt; 14 mW of power is harvested by the mobile device 50-cm distance away. Our experimental results successfully demonstrate that the power beam in reaction to the pilot signal is capable of tracking the mobile device´s location dynamically. In addition, since the pilot signal´s spectrum covers a certain frequency range, the carrier of wireless power in our scheme can be configured among multiple frequencies.