Change in the Spectrum of EM Radiation of the Electric Propulsion System of a UAV under Conditions of Forced Flight Stabilization

In the presence of new warfare technologies based on unmanned aerial vehicles (UAVs) or drones as a new type of mass production threats, today it is crucial to develop systems capable of detecting and defending people from the harmful objects flying high in the skies. Nowadays most drone detection methods are based on drone communication frequency recognition, thermal, audio signature detection or active radar technologies. Active radar technologies are easily detected due to their electromagnetic (EM) radiation and are one of the first to be destroyed or overflown. In the nearest future artificial intelligence instruments will be capable of performing full flight control and navigation without the need of any active radio communication EM radiation. This leaves us with very few technologies capable to detect drones in complete radio silence with no radio communication EM radiation on board. This paper presents a novel approach to the electrically powered drone detection techniques, where an electric propulsion system is an unavoidable drone design element. Our findings reveal significant variations in the EM radiation patterns across different types of drone electric propulsion engines and operational conditions. The paper presents the analysis of electric propulsion system structures installed in most common serial production drones, their propulsion engine control elements, sources of EM radiation and investigation of its frequency spectrum EM signature of a multirotor propulsion engines at various flight conditions and object drop tests performed. The change of the EM signature of drone dropping the object is presented as a key idea for safety system development to be used in the battlefield safety solutions.