Reconfigurable Intelligent Surface-Aided Wireless Power Transfer Systems: Analysis and Implementation

TL;DR

This paper introduces a multi-tile RIS beam scanning algorithm that significantly improves wireless power transfer efficiency for IoT devices by focusing RF energy, validated through simulations and real-world experiments.

Contribution

It proposes a novel multi-tile RIS beam scanning algorithm that requires only power information, enabling efficient beam focusing with hardware limitations.

Findings

Achieved about 20 dB increase in received power using the proposed algorithm.

Validated the algorithm's effectiveness through simulations and real-life experiments.

Demonstrated substantial enhancement in power transfer efficiency with RIS.

Abstract

Reconfigurable intelligent surface (RIS) is a promising technology for RF wireless power transfer (WPT) as it is capable of beamforming and beam focusing without using active and power-hungry components. In this paper, we propose a multi-tile RIS beam scanning (MTBS) algorithm for powering up internet-of-things (IoT) devices. Considering the hardware limitations of the IoT devices, the proposed algorithm requires only power information to enable the beam focusing capability of the RIS. Specifically, we first divide the RIS into smaller RIS tiles. Then, all RIS tiles and the phased array transmitter are iteratively scanned and optimized to maximize the receive power. We elaborately analyze the proposed algorithm and build a simulator to verify it. Furthermore, we have built a real-life testbed of RIS-aided WPT systems to validate the algorithm. The experimental results show that the proposed MTBS algorithm can properly control the transmission phase of the transmitter and the reflection phase of the RIS to focus the power at the receiver. Consequently, after executing the algorithm, about 20 dB improvement of the receive power is achieved compared to the case that all unit cells of the RIS are in OFF state. By experiments, we confirm that the RIS with the MTBS algorithm can greatly enhance the power transfer efficiency.