A Reconfigurable Rectifier With Optimal Loading Point Determination for RF Energy Harvesting From-22 dBm to-2 dBm

This brief introduces a wide working range rectifier with reconfigurable stage to accommodate with input power from -22 dBm to -2 dBm and maintain high rectifier efficiency. An auxiliary rectifier is designed for self-start-up functions. The measured rectifier peak efficiency is 39% at -5 dBm, and sensitivity efficiency is 7.5% at -22 dBm in static state. Self-start-up performance difference is less than 4% in the normal working range. Compared to conventional fixed stage rectifier, our design achieves 2x (+19%) peak efficiency improvement and high-efficiency range (eta(Rect) > 20%) is improved by 14 dB. And a novel fractional open-circuit voltage approximation method is also proposed to determine the optimized loading point in wide input range to help in maximum power point tracking (MPPT). Optimal fraction number is 0.5 in simulation and 0.6 is verified in measurement. Compared to other designs in literature, our proposed method shows better accuracy, simplicity, and avoiding redundancy over working range from -22 dBm to -2 dBm, with measured MPPT accuracy over 87%.