Electromagnetic Signatures for Drone Detection and Recognition

Abstract

Modern unmanned aerial vehicle (UAV) platforms predominantly rely on electric propulsion for controlled flight. Most current UAV propulsion systems employ brushless DC (BLDC) thrust motors. This paper demonstrates the passive detection of UAV electric propulsion systems using a dynamically changing alternating electromagnetic (EM) field created by BLDC thrust motors and power lines in the very low frequency and low frequency range. A high-performance low noise amplifier and a commercial Airspy HF+ SDR paired with a compact ferrite-core magnetic antenna, are used to capture near-field magnetic emissions from four different drones. The tested platforms include the mass-produced DJI Mini 2, DJI Mavic 2 Enterprise, DJI Air 3S, and the Eachine Tyro 109. The measured EM spectrum consistently exhibits motor phase commutation components and electronic speed controller PWM components with propulsion load-dependent sidebands, allowing extraction of time-, frequency-, and amplitude-dependent propulsion-related BLDC motor EM signatures for UAV detection and recognition. The results of the experiment show the capabilities of drone swarm detection and recognition of each flight mode of the propulsion system.