  We demonstrate an RF energy harvesting rectenna design based on a
metamaterial perfect absorber (MPA). With the embedded Schottky diodes, the
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 power. This leads to factor of 16
improvement of RF-DC conversion efficiency at ambient intensity level.
