Analyses On The Shielding Properties Of Electromagnetic Seal Structure For Electronic Equipment

The structure analysis of electronic equipment is one of the most importantapproaches to reduce the leakage of electromagnetic, the way to enhance the shieldingeffectiveness of enclosures through structure analysis was called the sealing ofelectromagnetic. Sometimes, slots are inevitably present in those structures whichexisted for heat dissipation or split joints. Non-contact overlapped joint is a frequentlyused connection structure in enclosure of electronic equipment. However, slots inoverlapped joint would decline the sealing property of electromagnetic of the enclosureinevitably. Exactly, the slots were absolutely the major factors which gave rise to thedecrease of shielding effectiveness. Whereupon, it is necessary to assess the shieldingproperties of electromagnetic seal structure. With the aid of the transmission-line Matrix(TLM) method and waveguide theory, the shielding performance of several metallicenclosures with typical non-contact overlaps illuminated by plane-wave wereinvestigated in the paper. And the main works are summarized as follows:(1) Based on quantitative calculation and qualitative analysis, parameters ofoverlapped joint slots such as overlapped length, width, height, and number of segmentsdivided by screws were investigated. At the same time, combined with the rectangularwaveguide transmission theory, non-contact overlapped joint structures which canprovide high shielding effectiveness were proposed based on analysis and comparison.Moreover, by simulating the resonance of enclosure including its mechanism andresonance modes, some factors and rules which have impact on the resonant frequencywere obtained. The conclusions have been demonstrated to be helpful guidance forshielding enclosure design.(2) By studied several properties of conductive gasket that was installed in theoverlapped joint slots, its shielding mechanism and the impact on shieldingeffectiveness of enclosures were obtained. Not only that, but the geometrical such aswidth and thickness were simulated. And electrical parameters of conductive gasketsuch as the conductivity and relative permeability including several different installationmethods were simulated. Finally, combined with the equivalent impedance of slot theory we came to the rules which would make contribution for us to comprehend thechange rules between conductive gaskets and the shielding properties of enclosure.(3) The shielding effectiveness of several enclosures with metal finger reeds wereanalyzed. And shielding performance of three different metal finger reeds interfered byplan-wave were studied and compared. At the same time, parameters such as thickness,slots between fingers, width of the finger and height were studied. In the end, combinedwith the equivalent impedance of slot theory, parameters of the metal finger reed wereinvestigated to achieve the influences they have on the shielding effectiveness. And theconclusion have been demonstrated as helpful guidelines for the engineering practice.