Waveform Optimization for Radio-Frequency Wireless Power Transfer

TL;DR

This paper develops a waveform design method for RF wireless power transfer that maximizes energy delivery by optimizing multisine signals based on channel information, using novel models and suboptimal solutions.

Contribution

It introduces a new waveform optimization framework for SISO RF WPT systems considering non-linear diode models and proposes two suboptimal algorithms for maximizing harvested power.

Findings

Proposed solutions outperform existing waveform designs in simulations.

Channel-aware waveform optimization significantly increases energy transfer efficiency.

The non-linear diode model provides more accurate predictions of harvested power.

Abstract

In this paper, we study the waveform design problem for a single-input single-output (SISO) radio-frequency (RF) wireless power transfer (WPT) system in frequency-selective channels. First, based on the actual non-linear current-voltage model of the diode at the energy receiver, we derive a semi-closed-form expression for the deliverable DC voltage in terms of the incident RF signal and hence obtain the average harvested power. Next, by adopting a multisine waveform structure for the transmit signal of the energy transmitter, we jointly design the multisine signal amplitudes and phases overall frequency tones according to the channel state information (CSI) to maximize the deliverable DC voltage or harvested power. Although our formulated problem is non-convex and difficult to solve, we propose two suboptimal solutions to it, based on the frequency-domain maximal ratio transmission (MRT) principle and the sequential convex optimization (SCP) technique, respectively. Using various simulations, the performance gain of our solutions over the existing waveform designs is shown.