An experimental evaluation of surrounding RF energy harvesting devices

In this paper, we present a study of RF energy harvesting devices. The surrounding RF power density was measured. The average of the total radiation power density in broadband (1GHz-3.5GHz) is in the order of -12dBm/m² (63μW/m²). The maximum of the RF density power is measured in 1.8GHz-1.9GHz frequency band, it is around -14dBm/m². Two rectifiers have been designed and simulated at 1.85GHz and 2.45 GHz. The choice of the load to optimize the recovered DC power is studied, and the various antennas were optimized and evaluated. Multiple rectennas have been designed to recover the ambient RF energy. The best performance is obtained with a spiral antenna. The DC energy harvested in out-door ambient, near a mobile phone base station, is presented. The maximum harvested DC power is around 0.1 μW. The harvested energy can directly supply some devices such as low power wireless sensors or can be used to trickle charge a super-capacitor or rechargeable micro-battery.