Custom IC for Ultra-low Power RF Energy Harvesting

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Abstract
This paper presents a custom IC that provides an efficient interface between an ultra-low power RF rectifying antenna (rectenna) source and a microbattery, with the goal of maximum power harvesting. The energy harvester IC uses current-starved circuitry, a non-overlapping gate-drive, and a sub-threshold current source to achieve a nominal supply current in the 200 nA range for VDD = 2.5 V. Experimental results are given with the IC harvesting energy from a 1.93 GHz patch rectenna to a battery with voltages ranging from 2.5 V to 4.15 V. Overall conversion efficiency including all control losses is demonstrated at over 35% at an input power of just 1.5 muW and at over 70% at input power levels over 30 muW. The IC is fabricated in a 5 V, 0.35 mum CMOS process. Although the IC was designed for RF energy harvesting, the low power boost converter can be applied to other power sources such as wind, vibrations, and temperature.