A Cascade Structure with Burst Charging Mode for RF Energy Harvesting

This paper presents a novel RF energy harvest system with a burst charging mode, which achieves high sensitivity. The popular method to output high DC voltage under low input power is increasing the number of stages of the RF rectifier. However, this reduces the amplitude of the input RF signal and increases the power loss. When the amplitude of input RF signal is lower than the threshold voltage of MOSFET, the power conversion efficiency (PCE) of rectifier will drop sharply. Based on this principle, the proposed architecture uses a three-stage rectifier to output a direct-current (DC) voltage that exceeds the threshold voltage, and then uses a low-frequency charge pump working with a burst operation mode to output a high voltage. The post-layout simulation results show a -38.2 dBm sensitivity for 1 V output across a capacitive load in a 55nm CMOS process technology.