High-Efficiency 10-GHz Low-Cost Scalable Rectenna Subarrays

This paper details the design and characterization of rectenna subarrays for far-field wireless power transfer at 10GHz. The designs are scalable to larger areas with dc combining. Two 4-element subarrays are presented: one with a rectifier per antenna element, and one with 4 antenna elements per rectifier. The first subarray consists of dual polarized Coptic-cross elements, optimized for higher incident power densities with dc combining. The second subarray is a linearly polarized patch array with a differential feed coupled to a single active rectifier for improved efficiency at lower incident power densities through RF combining. Both designs are fabricated on a thin layer of polyimide mounted atop expanded PTFE for moisture resistance and mechanical flexibility. For a broadside incident plane wave, the subarrays demonstrate up to 35% conversion efficiency at power densities below 1mW/cm². An efficiency of 50% is measured for the RF-combined subarray at 0.837mW/cm² power density.