Multi-Device Charging RIS-Aided Wireless Power Transfer Systems

As wireless charging devices are booming, wireless power transfer (WPT) systems are demanded to charge multiple devices simultaneously. Currently, reconfigurable intelligent surface (RIS) is emerging as a potential candidate for WPT applications owing to its energy-efficient feature. In this paper, we study multi-focus schemes that enable the RIS to charge multiple receivers simultaneously. We propose two multi-focus techniques: pattern addition (PA) and random unit cell interleaving (RUI). The two proposed methods can skillfully control received power levels with different weight factors given to each receiver. Mathematical analysis is rigorously presented and then verified by simulation. Simulation results demonstrate that wireless power relayed by the RIS is well distributed to all receivers.