Research On Shielding Effectiveness Of Multilayer Shielding Topology

The electromagnetic environment becomes more and more severe.When the single-layer shielding structure cannot meet the shielding requirements in some specific cases,people turn to the research on multilayer shielding to ensure the normal operation of the electronic equipment.In engineering practice,multilayer shielding topology has been widely used compared with single-layer shielding structures for its ultra-high shielding performance.Therefore,the research on the shielding effectiveness of multilayer shielding topology has important engineering significance.For two kinds of multilayer shielding topologies commonly used in engineering,this paper studies the shielding effectiveness and influencing factors of electromagnetic leakage caused by holes and slots on the shielding enclosure.For the ultra-high shielding performance of multilayer shielding topology and the limitation of the dynamic range of the general shielding effectiveness testing system,the relationship between multilayer shielding topology and single-layer shielding structures is studied.An experiment is set to verify the correctness of the results.Finally,for the electromagnetic leakage caused by interconnect cables in the practical use of multilayer shielding topology,the electromagnetic leakage process is analyzed and the influence of cables on shielding effectiveness is explored.The corresponding rules are summarized.Through the above research,it provides ideas and guidelines for the design and application of the practical multilayer shielding enclosure.The main work of this paper is as follows:(1)Study on the shielding effectiveness of multilayer shielding enclosure with holes.For the tandem multilayer shielding enclosure,an analytical model is established,and the Bethe's small aperture coupling theory based on the dyadic Green's function is used to analyze its shielding effectiveness and influencing factors.For the nested multilayer shielding enclosure,the effects of relative position,shape and array of holes on the shielding effectiveness are analyzed by numerical simulation method,and some suggestions for multilayer shielding enclosure design are given.(2)Explore the relationship between single-layer shielding enclosure and multilayer shielding enclosure.For the problem of using the sum of shielding effectiveness values of each layer shielding enclosure to estimate the shielding effectiveness of multilayer shielding enclosure,Bethe's small aperture coupling theory and electromagnetic field radiation theory are used to derive the correction method between the shielding effectiveness of multilayer shielding enclosure and the sum of the shielding effectiveness of each shielding enclosure at low-frequency,resonant-frequency,and high-frequency respectively.In addition,it is tested and verified in the high frequency band.The maximum error between the theoretical correction value and the actual test value was 7.87 d B,showing a good consistency.(3)Study on the shielding effectiveness of multilayer shields with cables.The electromagnetic leakage model of interconnection cables in multilayer shielding enclosure is established,and the electromagnetic leakage process is analyzed.The numerical simulation method is used to investigate the influence of the polarization direction of the interference source and the length of the cable outside the enclosure on the shielding effectiveness.Corresponding rules are summarized,and suggestions are put forward for the practical use of multilayer shielding enclosure.