A single-layer efficient polarization-insensitive electromagnetic rectifying metasurface for wireless power transfer

In this paper, an efficient electromagnetic rectifying metasurface (ERM) is proposed for wireless power transfer. The unit cell for the proposed ERM is composed of a cross-shaped energy capture structure that can absorb the electromagnetic power from the free space. The capture efficiency of the centrally symmetric structure exhibits insensitivity to the polarization of the incident wave. By directly connecting the Schottky diode to the ERM unit cell, the received electromagnetic power can be converted to DC power. The merit of the proposed ERM design is that no extra matching circuit is required, which can reduce the size, complexity, and insertion loss. To demonstrate the concept, a prototype of a 4 × 4-element ERM was fabricated and measured. The experimental results show that the proposed ERM array can produce up to 166 mW output DC power with an efficiency of 71.1% at an incident power density of 1050 μW/cm². The polarization stability of the ERM is also verified by measurement with less than 10% efficiency reduction for different polarizations of the incident wave.