RF energy harvester with peak power conversion efficiency tracking

Rectifier circuits or power harvesters are a critical module in a variety of wireless sensors, radio frequency identification (RFID) tags, and Internet-of-Thing (IoT) devices relying on harvested power from radio waves. The threshold compensation circuit techniques have been proposed in the literature to improve the Power Conversion Efficiency (PCE) of CMOS-based rectifiers. However, these circuits are designed to achieve maximum PCE at a specific input power level, and has significantly lower efficiency at other input power levels. In this paper, we propose a novel energy harvester which maximises its PCE over a wide input power range. The proposed design relies on sensing of the rectifier output voltage, management of the output current and reconfiguration of the rectifier. The design, which operates at 915 MHz, is demonstrated through simulations in a 130 nm CMOS process. The simulation results show that the harvester manages to develop a 3 V DC with -25 dBm input power sensitivity and its PCE remains above 60% for 23 dB input power range.