Photovoltaic-Assisted Self- V th-Cancellation CMOS Rectifier for Synergistic RF Energy Harvesting

A highly efficient CMOS rectifier for RF energy harvesting has been developed (using 0.18-mu m CMOS technology). To operate with high efficiency even under extremely low input power conditions, the voltage-doubler-based rectifier was implemented using an effective combination of self-Vth-cancellation (SVC) and photovoltaic (PV)-assisted techniques. In this rectifier, the threshold voltage (Vth) of the diode-connected MOSFET was compensated for by a DC bias voltage generated from not only the on-chip PV cells, but also from the output voltage of the rectifier itself. Therefore, the rectifier operated with high efficiency even under low input power conditions. Furthermore, a bias voltage limiter using simple pn diodes was adopted to regulate the excessive Vth compensation effectively and realize a high efficiency in the operation of the rectifier over a wide power range. The radio frequency to DC power conversion efficiency (PCE) of 30.8 0 10 was achieved at an input power level of -15 dBm, a frequency of 1 GHz, an output load resistance of 10 k Omega, and a light irradiance of 10 mW/m(2).