Researchers Wake, Wirelessly Power Sensors Using Energy Harvested From an Unmanned Aerial Vehicle
Flying over a field of sensors, the UAV can select sensors to wake and even provide wireless power — though from a distance of four feet.
Researchers at the American University of Beirut and the Institute of Electronics, Computer, and Telecommunications Engineering (CNR IEIIT) have published a paper detailing an energy-harvesting system to allow a drone to both wake and power ground-based sensor systems wholly wirelessly.
"In this paper," the researchers explain in the publication's abstract, "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 -18.2dBm and a sensor can be triggered starting at power levels that are as low as -40 dBm. The designed system relies on passive components to boost the received signal to 4.5V at the output. Moreover, the address detector is characterised by a current consumption of 160nA in idle mode. The proposed solution can therefore be implemented in situations where it is critical to minimise the power consumption of sensors that rely on RF harvesting as their source of power."
According to the team's tests of the system, the current implementation of the system allows for remote sensor activation from a distance of 27.5 meters (around 90 feet) with the ability to target a specific sensor from an array; actually powering the sensor, however, required the UAV to come within 1.2 meters (around 4 feet) — though work on a high-efficiency rectenna system could improve this.
The team's work has been published as early access in the journal IEEE Sensors Letters under closed-access terms, with more information available in an interview with IEEE Spectrum.
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