A -31 dBm Sensitivity High-Efficiency RF Energy Harvesting System With Burst Charging Mode for IoT Applications

This paper presents a novel high-sensitivity high-efficiency radio frequency (RF) energy harvester with a burst charging technology. The popular high-sensitivity scheme is increasing the number of RF rectifier’s stages to output higher voltage which is suitable to supply downstream electronics. This will reduce the input signal amplitude and power conversion efficiency (PCE), which in turn needs more stages and is thus lost in a vicious circle. This paper uses an optimal-stage high-efficiency RF rectifier to solve this problem. A low-frequency (LF) charge pump (CP) is cascaded with the rectifier to raise the DC voltage. To further improve the sensitivity, the system uses a burst charging mode to remove the charge pump’s loading effect on the RF rectifier. Measurements demonstrate a -31 dBm sensitivity for 1 V output across a capacitive load in a 55 nm CMOS process technology. The power conversion efficiency equals 31.3% at -25 dBm.