The Interrogation Footprint of RFID-UAV: Electromagnetic Modeling and Experimentations

The combined use of unmanned aerial vehicles (UAV) and radiofrequency identification (RFID) devices is an emerging topic of the environmental monitoring, which combines the versatility of multi-copter airframes with the potentiality of low-cost wireless sensors. This paper introduces some performance metrics suitable to quantify the capability of an RFIDrone to scan a surface equipped with radio-sensors. By using simple propagation models, an optimal drone-surface distance is mathematically derived at the purpose to maximize the electromagnetic footprint for the specific choice of system parameters, such as the sensor type and position, the reader sensitivity, the ground reflectivity, the radiated power, and the flight velocity. Theoretical achievements and some preliminary experimentations indicate that omnidirectional antennas are preferred for the drone so that 9–12 m footprints could be achieved with state-of-the-art readers and battery-less or battery-assisted RFID sensors, provided that the UAV flights at 3–5 m from the surface to be monitored. In this condition, the hit-rate of arrays of tags is better than 90% for a flying speed less than 1.8 km/h. The read performance is instead sensibly degraded by the presence of multi path in case of sensors spaced out the surface.