Distributed Wireless Power Transfer System for Internet of Things Devices

The wireless power transfer via an electro-magnetic (EM) wave enables far-field power transfer for supplying power to Internet of Things (IoT) devices. However, the power attenuation of the EM wave leads to low end-to-end power transfer efficiency. In this paper, we provide an analytic and experimental study on the distributed wireless power transfer system as a means to overcome the low power transfer efficiency. In the distributed wireless power transfer system, a number of multiantenna power beacons, which are distributed over space, send out wireless power to charge IoT devices. Since each power beacon has a separate local oscillator and controller, it is very challenging to achieve frequency and phase synchronization among power beacons, which is the prerequisite for optimal distributed beamforming. In this paper, we study the performance of the distributed wireless power transfer system with or without the frequency and phase synchronization. Based on the experiment and simulation results, we show that the distributed wireless charging is advantageous in terms of the coverage probability as long as the optimal distributed beamforming is available in the distributed wireless power transfer system.