A 2.4GHz ambient RF energy harvesting system with −20dBm minimum input power and NiMH battery storage

We describe a radio frequency (RF) energy harvester and power management circuit that trickle charges a battery from incident power levels as low as -20dBm. We designed the harvester for the 2.4 GHz RF band to leverage the ubiquity of energy that is produced by Wi-Fi, Bluetooth, and other devices. This paper reports on the design and current status of the harvester and compares our performance to other published results. In this incident power regime, rectified voltages are low, so power management circuit operation in the 100mV regime is critical. This paper describes a novel rectenna design, boost converter, and battery charger for RF energy harvesting specifically tuned to this low-power regime. At −20dBm RF input power, the harvesting system (rectenna, boost converter, and battery charger) sources 5.8µJ into a rechargeable battery after 1 hour.