Wideband Rectifying Metasurface with Enhanced Efficiency for Wireless Power Transmission via Harmonic Feedback Design

We present a wideband rectifying metasurface (RMS) with enhanced system efficiency for wireless power transmission and energy harvesting. The RMS consists of periodic arrays with integrated diodes, with a high input impedance matched with the diodes, thus eliminating the matching network between metasurface (MS) and rectifier. Besides, a unique harmonic feedback network is embedded in each unit cell, rectifying the high-order harmonic generated by the diode repeatedly, improving the total efficiency over a wide bandwidth. The converted DC power is channeled to one single load through the DC-paths formed by the branches of MS and a series of inductors, avoiding additional DC-combination networks. The MS can effectively capture EM energy at an operating band of 2-3.5 GHz, and the simulated radiation-AC efficiency is up to 99% at 2.8 GHz. A finite 8 × 8 array is fabricated and measured. The total conversion efficiency reaches a peak value of 60.5% at 2.7 GHz when the power density is 25dBm/m2, and is greater than 40% from 2.3 GHz to 2.9 GHz, exhibiting a wide bandwidth of 23.1% compared with existing state-of-the-art studies. The integrated MS-based RF energy harvester with the advantages of a simple structure is of great significance for wireless power transfer and energy harvesting applications.