Leveraging UAVs for Passive RF Charging and Ultralowpower Wake-Up of Ground Sensors

In this letter, we design and implement a radio frequency (RF) energy harvesting and wake-up system that scavenges a 2.4-GHz signal from an unmanned aerial vehicle (UAV). The signal transmitted by the UAV is harvested and rectified to dc voltage to power a sensor on the ground. Additionally, the UAV modulates the transmitted signal to encode an address that triggers a particular sensor from sleep mode to active mode. The proposed system exhibits high sensitivity to low power levels. In fact, charging can be initiated from input power levels as low as -18.2 dBm, and a sensor can be triggered starting at power levels that are as low as 0 dBm. The designed system relies on passive components to boost the received signal to 4.5 V at the output. Moreover, the address detector is characterized by a current consumption of 160 nA in idle mode. The proposed solution can therefore be implemented in situations where it is critical to minimize the power consumption of sensors that rely on RF harvesting as their source of power.