Phase-controlled Cooperative Wireless Power Transfer for Backscatter IoT Devices

Abstract

To supply energy for Internet of Things (IoT) devices, this paper proposes phase-controlled wireless power transfer by generating constructive standing waves, on multiple IoT devices, using distributed multiple antennas. The proposed approach realizes equitable power supply distribution among all the IoT devices by switching the phase sets for TX antennas in a time-division manner, and each phase set is optimized for individual IoT devices. In particular, our approach uses received signal strength indicator (RSSI) feedback packets to optimize the phase set of each TX antenna and applies a heuristic algorithm to reduce the number of RSSI feedback packets. We evaluated our approach using computer simulations and experimental micro benchmarks. The computer simulation assumes 64 antennas installed at 2 m intervals on the ceiling of a 15 m by 15 m by 2.5 m room and, each antenna emits 100 mW continuous nonmodulated sine waves. The simulation results show that each of the 10 IoT devices placed on the floor is able to receive an average of approximately 53.6 uW, which is approximately 5.1 times the existing method. The experimental micro benchmarks show the feasibility of the proposed method.