Wireless Power Transfer With Distributed Antennas: System Design, Prototype, and Experiments

In this article, we design and experiment a far-field wireless power transfer (WPT) architecture based on a distributed antenna system (DAS), so-called WPT DAS, that dynamically selects transmit antenna and frequency to increase the output dc power. Uniquely, spatial and frequency diversities are jointly exploited in the proposed WPT DAS with low complexity, low cost, and flexible deployment to combat the wireless fading channel. A numerical experiment is designed to show the benefits using antenna and frequency selections in spatially and frequency selective fading channels for single-user and multiuser cases. Accordingly, the proposed WPT DAS for single-user and two-user cases is prototyped. At the transmitter, we adopt antenna selection to exploit the spatial diversity and adopt frequency selection to exploit the frequency diversity. A low-complexity over-the-air limited feedback using an IEEE 802.15.4 RF interface is designed for antenna and frequency selections and reporting from the receiver to the transmitter. The proposed WPT DAS prototype is demonstrated in a real indoor environment. The measurements show that WPT DAS can boost the output dc power by up to 30 dB in a single-user case and boost the sum of the output dc power by up to 21.8 dB in the two-user case and broaden the service coverage area in a low cost, low complexity, and flexible manner.