Joint Waveform and Beamforming Optimization for MIMO Wireless Power Transfer

TL;DR

This paper presents a joint optimization of waveform and beamforming in MIMO wireless power transfer systems, significantly enhancing output power by leveraging rectenna nonlinearity and adaptive strategies.

Contribution

It introduces a comprehensive joint optimization framework for waveform and beamforming in multi-sine MIMO WPT, considering practical rectenna nonlinearities and combining schemes.

Findings

Joint design increases DC power output by leveraging beamforming and frequency diversity.

The proposed method achieves up to 180% higher power than beamforming-only approaches.

Optimization adapts to channel state information and practical circuit constraints.

Abstract

In this paper, we study a multi-sine multiple-input multiple-output (MIMO) wireless power transfer (WPT) system with the objective to increase the output DC power. We jointly optimize the multi-sine waveform and beamforming accounting for the rectenna nonlinearity, and consider two combining schemes for the rectennas at the receiver, namely DC and RF combinings. For DC combining, the waveform and transmit beamforming are optimized, as a function of the channel state information (CSI). For RF combining, the optimal transmit and receive beamformings are provided in closed form and the waveform is optimized. We also consider a practical RF combining circuit using phase shifter and RF power combiner and optimize the waveform, transmit beamforming, and analog receive beamforming adaptive to the CSI. Two types of performance evaluations, based on the nonlinear rectenna model and accurate and realistic circuit simulations, are provided. The evaluations demonstrate that the joint waveform and beamforming design can increase the output DC power by leveraging the beamforming gain, the frequency diversity gain, and the rectenna nonlinearity. It also shows that the joint waveform and beamforming design provides a higher output DC power than the beamforming-only design with a relative gain of 180% in a two-transmit antenna sixteen-sinewave two-receive antenna setup.