Time-Division Energy Beamforming for Multiuser Wireless Power Transfer with Non-Linear Energy Harvesting

TL;DR

This paper introduces a novel time-division energy beamforming method for multiuser wireless power transfer that accounts for non-linear energy harvesting, optimizing beamforming and time allocation to maximize harvested energy.

Contribution

It proposes a new time-division beamforming approach that considers non-linear RF-DC conversion, improving energy transfer efficiency over traditional methods.

Findings

Outperforms conventional multi-beam energy transfer methods.

Effectively maximizes minimum harvested energy among users.

Uses alternating optimization and SCA for non-convex problem solving.

Abstract

Energy beamforming has emerged as a promising technique for enhancing the energy transfer efficiency of wireless power transfer (WPT). However, the performance of conventional energy beamforming may seriously degrade due to the non-linear radio frequency (RF) to direct current (DC) conversion at energy receivers (ERs). To tackle this issue, this letter proposes a new time-division energy beamforming, in which different energy beamforming matrices (of high ranks in general) are time shared to exploit the "convex-concave" shape of the RF-DC power relation at ERs. By considering a particular time duration for WPT, we maximize the minimum harvested DC energy among all ERs, by jointly optimizing the energy beamforming matrices and the corresponding time allocation. In order to solve the non-convex min-DC-energy maximization problem, we propose an efficient solution by using the techniques of alternating optimization and successive convex approximation (SCA). Numerical results show that the proposed time-division energy beamforming design indeed outperforms the conventional multi-beam and time-division-multiple-access (TDMA)-based energy transmissions.