Energy-Efficient RIS-assisted SWIPT System With Electromagnetic-Compliant Model

In this article, we conduct the system optimization for a reconfigurable intelligent surface (RIS)-assisted simultaneous wireless power transfer (SWIPT) network. In particular, a problem of energy efficiency maximization subject to the physical limitations and quality of service (Q0S) is introduced. Specifically, the existence of potential eavesdroppers and the physical features, which are exposed by the end-to-end transfer model based on the S-parameter analysis, of the main ends are considered. For tackling the above complicated issue, the Sherman-Morrison formula is first adopted to transform it into a more solvable form. Then the alternative solving approaches are introduced to optimize the beamforming vector of the transmitter, artificial noise, power splitting ratio of the dual-demand receiver, and reflection coefficient of the RIS iteratively. The results demonstrate the effectiveness of the proposed algorithms and the practice-oriented model.