A polarization-insensitive rectifying surface for 2.4 GHz WLAN band RF energy harvesting

This article introduces a polarization-insensitive rectifying surface for 2.4 GHz WLAN band RF energy harvesting. The unit cell of the rectifying surface is formed by combining an interdigital structure with a square ring structure, optimized for high RF harvest efficiency over a wide band. For optimal performance, our design employs a direct matching of the Schottky diodes to the rectifying surface, minimizing signal loss and enhancing rectification effectiveness. To demonstrate the concept, a 4\times 4 element rectifying surface array was fabricated and measured, yielding a total efficiency of 21% at an incident power density of 2.62~\mu W/cm2. The measured total efficiency remains higher than 18.9% over the 2.4-2.57 GHz range, covering the 2.4 GHz WLAN band. Furthermore, the total efficiency remains constant despite variations in the polarization angle of the incident wave. Our design demonstrates a highly efficient rectifying surface for harvesting low-power energy within the 2.4 GHz WLAN band, offering a promising solution for powering wireless devices.