Research On Protection Effectiveness Of Vehicle Electromagnetic Shielding Techniques In HEMP Environment

HEMP (high altitude nuclear electromagnetic pulse) with super electromagnetic energycan interfere with or destroy electronic systems within the coverage. With theimprovement of vehicle electronic informatization, the integrated electronic systems aremore inside vehicle, which leads to HEMP interference and affects vehicle mobility andsafety. The main way of introducing external electromagnetic interference includeswindows, equipment apertures and cables for vehicle electronic equipment, which is themain part of electromagnetic protection design. Research on shielding technology andprotection effectiveness of windows, equipment apertures and cables is the premise andbasis for HEMP protection design and engineering implementation, and has importantlytheory and application value.Metal mesh is a technology of shielding window. The shielding effectiveness (SE)of metal cavity with a single hole and uniform holes is calculated by transmissionline method to determine the effect of mesh shape, wire diameter and mesh size. Thenon-uniform metal mesh instead of uniform metal mesh to shield windows so that driversight is not affected and have better SE, and the non-uniform metal validity is verified byexperiment and CST simulation. CST model of two kinds of metal mesh shieldingwindows is established. The vehicle model is simplified to cab model. The electric fieldintensity and SE of the location of dashboard, radio, center, driver are analyzed in theHEMP environment to verify shielding effect of non-uniform metal.External cavity and metal waveguide are used to shield vents of electronic equipment.The influence of external cavity length and waveguide thickness, size, length on SE iscalculated. Establishing CST simulation model of electronic equipment with metalwaveguide and external cavity is used to contrast their SE. Designing waveguide structureand establishing simulation model of metal waveguide shielding car shell vents to analyzethe SE at the position of engine, ECU, radiators. For the bare shielding cable, Interference voltage of shielding cable with different barelength is researched under HEMP radiation by experiment and simulation. In CSTsimulation modeling, the shield transfer impedance calculated is imported into thesimulation model to obtain shielding layer characteristic. The influence of shielding layergrounding, the total length of shielded cable, wire radius on the bare end of interferencevoltage is analyzed in HEMP environment.Establishing engine compartment model and analyzing the interference voltage ofthrottle sensor cable before and after protection. Calculating the characteristic impedanceof shielding cable is used to analyze interference voltage and SE of cable with differentimpedances (including the characteristic impedance).The main work and innovations are as follows:(1) The non-uniform metal mesh instead of uniform metal mesh to shield windows. Thelarger mesh is installed in the place of affecting driver sight, and the smaller mesh isinstalled in the place which does not affect driver sight. The vehicle model is simplified tocab model, simulation data show that Non-uniform metal mesh with better SE does notaffect driver sight.(2) Designing honeycomb waveguide to shield car shell vents, and simplifying car shellstructure to build engine compartment model, and analyzing the SE at the position ofengine, ECU, radiators in HEMP environment.(3) The interference voltage is analyzed for length of bare shield, the shield layergrounding and so on. Shielding layer characteristic of protected throttle sensor cable withactual size is calculated, and combining with the actual car structure to analysis of cableSE. In order to improve cable protection capacity, it is recommended to avoid bare cable,and ensure to grounding at both ends of shielding layer if bare cable is not avoided.Electromagnetic interference is reduced further by designing shielding layer parameters forfull shielding cables.The above work researches on protection effectiveness of vehicle electromagneticshielding techniques, which provides a reference solution for shielding technologyselection, design and implementation, and has the very good practical value.