High Efficiency Ambient RF Energy Harvesting by a Metamaterial Perfect Absorber

We demonstrate a high-efficiency radio frequency (RF) energy harvesting device based on a metamaterial perfect absorber (MPA). With the embedded Schottky diodes, the MPA-based rectenna converts captured RF waves to DC power. The Fabry-Perot (FP) cavity resonance of the MPA greatly improves the amount of energy captured. Furthermore, the FP resonance exhibits a high Q-factor and significantly increases the voltage across the Schottky diodes, which improves the rectification efficiency, particularly at low intensity. This leads to a factor of 16 improvement of RF-DC conversion efficiency at ambient intensity level. Our MPA-based rectenna can obtain 100 μW power for an incident intensity of 0.4µW/cm2.