Custom IC for Ultralow Power RF Energy Scavenging

This letter presents a custom IC that provides an efficient interface between an ultralow power RF rectifying antenna (rectenna) power source and a microbattery for maximum power scavenging. The energy scavenger IC operates a boost converter in pulsed fixed-frequency discontinuous conduction mode to present a positive resistance to the rectenna. It uses current-starved circuitry, a nonoverlapping gate drive, and a subthreshold current source to achieve a nominal supply current in the 200-nA range for V _DD = 2.5 V. Experimental results are given with the IC scavenging energy from a 1.93-GHz patch rectenna to a battery with voltages ranging from 2.5 to 4.15 V. Overall conversion efficiency including all control losses is demonstrated at over 35% at an input power of just 1.5 μW and at over 70% at input power levels over 30 μW. The IC is fabricated in a 5-V, 0.35-μm CMOS process. Although the IC was designed for RF energy scavenging, the low-power boost converter can be applied to other power sources such as wind, vibration, and temperature.