Demonstration of a highly efficient RF energy harvester for Wi-Fi signals

This paper demonstrates a highly efficient radio frequency (RF) energy harvester to scavenge 2.45 GHz Wi-Fi energies from commercial available wireless routers. The measured Wi-Fi signal strength available in the normal working space is -44 to -18 dBm. In order to harvest and utilize such small signals, a complete system is designed to include a high gain antenna array, a high efficiency rectifier and a boost converter for voltage conditioning. The system can harvest a final DC power of 76.35 μW at a distance of 40 cm away from the wireless router. As the distance increases, the harvested power decreases gradually. A maximum working distance of 2.4 m is measured. The total RF to DC power conversion efficiency is measured to be from 9.76% at 2.4 m to 33.7% at 40 cm away from the router. The output DC voltage are in the range of 1.5 to 7.36 V, which is sufficient to supply various applications such as portable calculators, LED arrays and energy storage devices such as super-capacitors and batteries.