Wireless Power Transfer Empowered by Reconfigurable Intelligent Surfaces

In order to wirelessly power the nonline of sight devices by a base station (BS) with massive antennas, multiple reconfigurable intelligent surfaces (RISs) are employed to control the signal transmission directions in a dual-hop communication scenario. The objective of this paper is to maximize the minimum harvested power among all devices by designing both the beamformer at the BS and the controllable phases of impinging signals at the RISs. An optimal and a suboptimal schemes are proposed by considering the metrics of both harvested power and system complexity. Results indicate that the suboptimal scheme can achieve about 80% harvested power of the optimal scheme with low communication overhead between the BS and RISs.