Experimental Study on the Effect of Synchronization Accuracy for Near-Field RF Wireless Power Transfer in Multi-Antenna Systems

TL;DR

This experimental study investigates how synchronization accuracy affects near-field RF wireless power transfer efficiency in multi-antenna systems, demonstrating significant gains with proper phase alignment and scalability benefits.

Contribution

The paper provides experimental validation of beamfocusing gains and phase error tolerances in multi-antenna WPT systems, highlighting practical synchronization requirements.

Findings

Fully synchronized beamfocusing achieves 14 dB gain.

Phase errors below 20° cause less than 1 dB loss.

Scaling antennas improves power transfer efficiency.

Abstract

Wireless power transfer (WPT) technologies hold promise for enhancing device autonomy, particularly for energy-limited IoT systems. This paper presents experimental results on coherent and non-coherent transmit diversity approaches for WPT, tested in the near field using the Techtile testbed. We demonstrate that a fully synchronized beamfocusing system achieves a 14 dB gain over non-coherent transmission, consistent with the theoretical 14.9 dB gain for a 31-element array. Additionally, phase alignment errors below 20{\deg} result in less than 1 dB of gain loss, while errors exceeding 40{\deg} lead to losses over 3 dB. These findings suggest that phase coherency requirements for WPT can be relaxed, and that scaling the number of antennas is a promising strategy for improving power transfer efficiency.