High-Efficiency Wireless-Power-Transfer System Using Fully Rollable Tx/Rx Coils and Metasurface Screen.

This work presents a high-efficiency reconfigurable wireless-power-transfer (WPT) system using fully rollable Tx/Rx coils and a metasurface (MS) screen working at 6.78 MHz, for the first time. The MS screens are placed between the Tx and Rx to magnify the power-transfer efficiency (PTE) of the WPT system. The proposed MS-based WPT can be rolled down or rolled up as required, which allows end-users to use the space more flexibly. In the measurement results, the PTE of the WPT is improved from 13.32% to 32.49% at a power-transfer distance (PTD) of 40 cm with one MS screen, 5.42% to 42.25% at a PTD of 50 cm with two MS screens, 1.78% to 49% at a PTD of 60 cm with three MS screens, 0.85% to 46.24% at a PTD of 70 cm with four MS screens. The measured PTE results indicate that the demonstrated MS screens are greatly effective for magnifying the PTE and the PTD of the WPT. In addition, the measured PTE results in the misaligned condition verify that the MS screens also help increase the PTE of the WPT even in the misalignment condition.