Range Expansion for Wireless Power Transfer: A Joint Beamforming and Waveform Architecture

Far-field Wireless Power Transfer (WPT) has emerged as a viable power source for Internet of Things (IoT) and Wireless Sensor Network (WSN). Expansion of the power transfer range is an important challenge to enable the design of efficient networks of small autonomous devices and drive the massive numbers of devices using a single wireless power source. Several signal design strategies have been proposed and verified to maximize the output DC power at the receiver under a transmit power constraint. In this paper, we study channel-adaptive beamforming and waveform to expand the power transfer range as well as output DC power performance. To that end, we have designed, prototyped a far-field WPT system and established a WPT testbed in a realistic indoor environment. The experiments have been conducted in a variety of wireless channel conditions in an indoor office environment with various distances. The measurement data have been fitted using simple analytical model to analyze the output DC power and achievable range improvement depending on the signal design schemes and the number of tones and antennas. The model shows a clear relationship between signal design versus output DC power and achievable range, and enables to predict the achievable power transfer range for given transmit power constraint and target received DC power. Results highlight the significant benefit of a channel-adaptive joint beamforming and waveform architecture to expand the power transfer range.