A Highly Efficient Polarization-Independent Metamaterial-Based RF Energy-Harvesting Rectenna for Low-Power Applications

A highly-efficient multi-resonant RF energy-harvesting rectenna based on a metamaterial perfect absorber featuring closely-spaced polarization-independent absorption modes is presented. Its effective area is larger than its physical area, and so efficiencies of 230% and 130% are measured at power densities of 10 uW/cm2 and 1 uW/cm2 respectively, for a linear absorption mode at 0.75 GHz. The rectenna exhibits a broad polarization-independent region between 1.4 GHz and 1.7 GHz with maximum efficiencies of 167% and 36% for those same power densities. Additionally, by adjustment of the distance between the rectenna and a reflecting ground plane, the absorption frequency can be adjusted to a limited extent within the polarization-independent region. Lastly, the rectenna should be capable of delivering 100 uW of power to a device located within 50 m of a cell-phone tower under ideal conditions.