Investigation on Falling and Damage Mechanisms of UAV Illuminated by HPM Pulses

Unmanned aerial vehicle (UAV), when illuminated by high-power microwave (HPM), is vulnerable to losing control and even falling to the ground with damage. To explore the mechanism of the UAV's falling and its damage caused by HPM, the HPM radiation experiments on a certain kind of UAV are carried out. It is concluded that the UAV's cable is the main energy coupling path from HPM according to the analysis of the cable connection relationships among the flight control system (FCS), the electronic speed control (ESC) board, and the motors based on the experiment. Furthermore, the coupled voltages of the cable's termination load are obtained when the UAV is radiated by HPM with different carrier frequencies or incident directions using numerical calculation and typical test verification. To facilitate the analysis of circuit level, the equivalence of radiation and injection test is analyzed, so the waveform of the control signal related to the UAV's flight is recorded by the injection test. According to the experimental results and the principle of the UAV's flight dynamics, the effect mechanisms of the UAV's falling and its damage are clarified. The experimental results show that the carrier frequency of the HPM leading to the falling and damage of the UAV mainly depends on the length of the internal cable inside the UAV. The pulsewidth and the repetition frequency of HPM resulting in the UAV's falling are related to the pulsewidth and the period of the control signal of FCS. In addition, the coupled voltages induced on the twisted three-wire cables due to the illumination of HPM are verified to enter into the control signal port through parasitic capacitance and, finally, to damage the vulnerable components, including the metal–oxide–semiconductor field-effect transistor inside the ESC and the motor of the UAV. The damage mechanism is determined to be the high-voltage breakdown and large current burning.