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

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 2π span with high transmittance. Based on near-field focusing theory, an adapted formula is employed to guide the phase distribution for compensating incident waves. Two MTSs, each with dimensions of 190×190 mm2 and comprising 19×19 unit cells, are constructed to achieve dual-polarized two foci with 1:1 and 2:1 power allocations, yielding high focusing efficiencies of 71.6% and 65.2%, respectively. These two MTSs are fabricated and tested, demonstrating a minimal of -3 dB depth of focus (DOF) and width of focus (WOF). Results are aligned with theoretical predictions. These designs aim to facilitate stable high-efficiency power transfer to different systems based on their specific requirements.