An Analysis of Beamed Wireless Power Transfer in the Fresnel Zone Using a Dynamic, Metasurface Aperture

TL;DR

This paper explores a dynamic, reconfigurable metasurface aperture for near-field wireless power transfer within the Fresnel zone, analyzing tradeoffs and providing design formulas for system performance.

Contribution

It introduces a metasurface-based dynamic focusing approach for near-zone wireless power transfer and derives approximate formulas for key performance metrics.

Findings

Gaussian optics formulas effectively estimate transfer efficiency.

Numerical calculations confirm the accuracy of the derived formulas.

Tradeoff analysis relates spot size, aperture size, wavelength, and focal distance.

Abstract

Wireless power transfer (WPT) has been an active topic of research, with a number of WPT schemes implemented in the near-field (coupling) and far-field (radiation) regimes. Here, we consider a beamed WPT scheme based on a dynamically reconfigurable source aperture transferring power to receiving devices within the Fresnel (near-zone) region. In this context, the dynamic aperture resembles a reconfigurable lens capable of focusing power to a well-defined spot, whose dimension can be related to a point spread function (PSF). Near-zone focusing can be achieved by generating different amplitude or phase profiles over the aperture, which can be realized using traditional architectures, such as phased arrays. Alternatively, metasurface guided-wave apertures can achieve dynamic focusing, with potentially lower cost implementations. We present an initial tradeoff analysis of the near-zone WPT concept, relating key parameters such as spot size, aperture size, wavelength, focal distance, and availability of sources. We find that approximate design formulas derived from the Gaussian optics approximation provide useful estimates of system performance, including transfer efficiency and coverage volume. The accuracy of these formulas is confirmed using numerical calculations.