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Abstract
The performance of time-reversal (TR) based far-field wireless power transfer (WPT) from an antenna array in a complex propagation environment is investigated in comparison with conventional array-based beamforming (BF). A two-step experiment is performed, namely 1) the propagation stage and 2) rectification stage. In the propagation stage, signal transmission is measured between the transmit array and receive antenna in an indoor multipath environment, for line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios. The results demonstrate that TR results in higher peak voltage compared to BF given the same average transmit power. In addition, while BF loses its ability to selectively send waves at the receiver due to impairment of the beam from multipath, TR can selectively focus waves at the receiver by inherently taking advantage of multipath. In the rectification stage, the resulting signals from the propagation stage are fed into a broadband rectifier for RF-to-DC conversion. It is shown that the signals received using TR lead to higher rectified DC voltage and rectification efficiency. The overall results suggest that TR can outperform BF with higher rectification efficiency given the same average transmit power. Through optimization of the TR pulse interval, array configuration and transmit power, further improvement in the performance of TR based WPT in a complex propagation environment is possible.
Highlights
Far-field wireless power transfer (WPT) is an emerging technology for wirelessly charging small, low power devices, which can be widely utilized in the fields of mobile devices, internet of things (IoT), sensors, and biomedical devices [1]–[7]
It can be concluded that given the same average transmit power, TR delivers higher peak voltage as a result of wave focusing that allows for more effective rectification of RF to DC compared to BF in a complex propagation environment
In this paper, we investigated the performance of timereversal (TR) based wireless power transfer (WPT) from an antenna array in comparison to conventional beamforming (BF) based WPT in a complex propagation environment
Summary
Far-field (radiative) wireless power transfer (WPT) is an emerging technology for wirelessly charging small, low power devices, which can be widely utilized in the fields of mobile devices, internet of things (IoT), sensors, and biomedical devices [1]–[7]. For far-field WPT, array-based beamforming (BF) is commonly used to focus electromagnetic energy at desired locations [8]–[14]. Antenna array is considered based on the theoretical development for simultaneous wireless information and power transfer applications. For mMIMO beamforming, the configuration and operation of the system could be quite complicated due to a large number of antennas used. TR applied in a complex propagation environment allows for spatial and temporal wave focusing by taking advantage of multipath, thereby selectively concentrating electromagnetic power at a desired location even with a single transmit antenna [20]–[26]. Previous studies have demonstrated that sending TR waveforms can deliver higher peak power (compared to sending narrowband signals) at desired locations in a complex propagation environment [17], [20], [26].
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