The backdoor coupling effect of unmanned aerial vehicles (UAVs) under high-power microwave (HPM) irradiation is an important topic in the field of electromagnetic protection and countermeasures.

This paper investigates the electromagnetic coupling characteristics of a certain type of mini-UAV under HPM exposure, aiming to reveal its electromagnetic response and damage mechanisms under different frequencies and incidence angles.

Based on the UAV kinematic model and spatial energy transfer theory, a dual-coordinate system model incorporating flight attitude variations was established. Using the COMSOL Multiphysics simulation platform, the electric field and current distributions on the UAV fuselage and internal flight control motherboard were systematically analyzed within the 1—18 GHz frequency range under various incident angles.

The simulation results indicate that the typical backdoor coupling pathway of the selected UAV——the openings on both sides of the fuselage——is the critical channel connecting external irradiation and internal damage. As the frequency and incident angle increase, the electric field and induced current density on the fuselage surface increase significantly. Particularly near 14 GHz, a strong resonance occurs due to the match between the aperture size and the Ku-band waveguide dimensions, leading to a sharp rise in current density at this frequency. The FM25V05 chip on the flight control motherboard is prone to overvoltage at 14, 15, 16, and 18 GHz. The V_dd pin voltage reaches 21.868 V at 18 GHz, far exceeding its operational threshold and potentially causing functional failure.

This study provides a theoretical basis and simulation support for frequency selection and operational strategy development in HPM-based anti-UAV systems.