Focusing Metasurfaces of (Un)equal Power Allocations for Wireless Power Transfer

TL;DR

This paper proposes focusing metasurfaces tailored for different power allocations in wireless power transfer, demonstrating high efficiency and minimal depth of focus, to enhance power delivery in IoT environments.

Contribution

The work introduces novel metasurface designs capable of dual-polarized focusing with adjustable power ratios, validated through fabrication and testing.

Findings

Maximum focusing efficiencies of 71.6%, 65.2%, and 57.5% for different power allocations.

Fabricated metasurfaces achieve minimal -3 dB depth of focus.

Results align well with theoretical predictions.

Abstract

Focusing metasurfaces (MTSs) tailored for different power allocations in wireless power transfer (WPT) system are proposed in this letter. The designed metasurface unit cells ensure that the phase shift can cover over a 2{\pi} span with high transmittance. Based on near-field focusing theory, an adapted formula is employed to guide the phase distribution for compensating incident waves. Three MTSs, each with dimensions of 190*190 mm and comprising 19*19 unit cells, are constructed to achieve dual-polarized two foci with 1:1, 2:1, and 3:1 power allocations, yielding maximum focusing efficiencies of 71.6%, 65.2%, and 57.5%, respectively. The first two MTSs are fabricated and tested, demonstrating minimal -3 dB depth of focus (DOF). Results are aligned with theoretical predictions. These designs aim to facilitate power transfer to different systems based on their specific requirements in an internet of things (IoT) environment.