Reconfigurable Intelligent Surface-Assisted RF Wireless Power Transfer for Internet of Things System

Abstract

In this work, we study the utilization of reconfigurable intelligent surface (RIS) for assisting the radiofrequency (RF) based wireless power transfer (WPT) in the Internet of Things (IoT) system. The RIS device in this system is utilized to provide the line of sight (LOS) path when an obstacle blocks the direct power transmission from the transmitter to the receiver. In this work, we present a comprehensive modeling of the RIS-assisted RF WPT for IoT systems, which includes the spatial model, RIS-assisted RF WPT model, and total receiver power model. The performance of RIS-assisted RF WPT is evaluated by simulation matched to the IoT system. By simulation, we have verified that the RIS device can assist the RF WPT in the IoT system, especially when the obstacle completely blocks the power transmission directly from the transmitter to the receiver. The receiver can achieve 0,4714% end-to-end power transfer efficiency at a 1 meter distance from the RIS device. Meanwhile, 0,0290% end-to-end power transfer efficiency is achieved within a 15 meters distance from the RIS device. In this work, we have investigated the performance of RIS-assisted RF WPT with various numbers of unit cells in the RF WPT system. We found that increasing the number of unit cells in RF WPT after a certain number is ineffective for the RF WPT in an IoT system.