Study on the Shielding Effectiveness of Airborne Navigation Equipment Enclosures under High-Intensity Radiated Fields (HIRF)

High-Intensity Radiated Fields (HIRF) can cause significant electromagnetic interference (EMI) to aircraft and their onboard systems, posing a threat to flight safety. To enhance the interference immunity of navigation devices, this study establishes a 3D simulation model based on the actual structure of a GNSS receiver and utilizes CST software to analyze the shielding effectiveness (SE) under varying conditions, including frequency, material properties, polarization, incident angle, and aperture configuration. The results show that structural differences, aperture coupling effects, and material characteristics have a significant impact on SE. In particular, strong single-point resonances frequently occur in the 3–10 GHz range, leading to severe SE fluctuations, while shielding performance generally deteriorates above 10 GHz due to reduced structural stability. To validate the simulation results, an anechoic chamber test was conducted, revealing signal faults in the GNSS receiver under high-frequency HIRF conditions, thereby confirming the validity of the simulation and the risk of coupling. Based on these findings, the study proposes optimization strategies including aperture control, resonance suppression, material selection, and multi-polarization/multi-directional protection, providing theoretical and engineering references for electromagnetic compatibility (EMC) design of airborne equipment in HIRF environments.