Reconfigurable Intelligent Surface Aided Constant-Envelope Wireless Power Transfer

By reconfiguring the propagation environment of electromagnetic waves artificially, reconfigurable intelligent surfaces (RISs) have been regarded as a promising and revolutionary hardware technology to improve energy spectrum efficiency wireless networks. In this paper, we study RIS aided multiuser multiple-input multiple-output (MIMO) power transfer (WPT) system, where transmitter is equipped with constant-envelope analog beamformer. First, maximize total received users by jointly optimizing beamformer at phase-shifts RIS, propose two alternating optimization based suboptimal solutions leveraging semidefinite relaxation (SDR) successive convex approximation (SCA) techniques respectively. Then, considering user fairness, formulate another problem subject users’ individual minimum constraints. A low complexity iterative algorithm on both direction method multipliers (ADMM) SCA proposed solve problem. case multiple users, further analyze asymptotic performance number elements approaches infinity, bound loss caused phase quantization. Numerical results show correctness analysis effectiveness algorithms.