To characterize the shielding effectiveness(SE) of materials against electromagnetic pulse(EMP) that cannot be adequately evaluated by traditional test methods,a transfer function model of SE is proposed.Using homemad...To characterize the shielding effectiveness(SE) of materials against electromagnetic pulse(EMP) that cannot be adequately evaluated by traditional test methods,a transfer function model of SE is proposed.Using homemade broadband coaxial fixture,the SE of a metal fabric material against square-pulse and electrostatic discharge(ESD) EMP is tested in the time domain.The peak SE calculated from the test results matches well with that obtained theoretically.Based on the system identification theory,we propose the transfer function model of SE,which takes the square pulse and human body model ESD EMP data obtained in the tests as training data and takes the machine model as verification data,as well as a second-order expression of the transfer function.Using the transfer function model,the waveforms of the shield-penetrated square-pulse EMP and the ESD EMP are actually predicted.From the perspective of system identification,this accurate prediction of the shielded waveform of EMP provides a reliable way for evaluating SE of materials against EMP.展开更多
Carbon microcoils were deposited onto Al2O3 substrates using C2H2/H2 as source gases and SF6 as an incorporated additive gas in a thermal chemical vapor deposition system. At as-grown state, the carbon coils (d-CCs) s...Carbon microcoils were deposited onto Al2O3 substrates using C2H2/H2 as source gases and SF6 as an incorporated additive gas in a thermal chemical vapor deposition system. At as-grown state, the carbon coils (d-CCs) show the diverse geometry. The geometry-controlled carbon microcoils (g-CMCs) could be obtained by manipulating the injection time of SF6 in C2H2 source gas. The d-CCs with polyurethane (PU) composite (d-CC@PU) and the g-CMCs with PU composite (g-CMC@PU) were obtained by dispersing d-CCs and g-CMCs in PU, respectively. The electromagnetic wave shielding properties of d-CC@PU and g-CMC@PU composites were investigated in the frequency range of 0.25 - 4.0 GHz. The shielding effectiveness (SE) of d-CC@PU and g-CMC@PU composites were measured and discussed according to the weight percent of d-CCs and g-CMCs in the composites with the thickness of the composites layers. On the whole frequency range in this work, the SE of g-CMC@PU composites was higher than those of d-CC@PU composites, irrespective of the weight percent of carbon coils in the composites and the layer thickness. Furthermore, we confirmed that the absorption mechanism, instead of the reflection mechanism, seemed to play the critical role to shield the EMI for not only the g-CMC@PU composites but also the d-CC@PU composites.展开更多
This article presents some new experimental data for study the shielding effect of electromagnetic wave. The frequencies of electromagnetic wave are mainly focused on emission of daily electrical equipments, which are...This article presents some new experimental data for study the shielding effect of electromagnetic wave. The frequencies of electromagnetic wave are mainly focused on emission of daily electrical equipments, which are normally called “low frequency electromagnetic waves”. In this work, a water pump with maximum magnetic field intensity of ca. 2300 mG was applied as emission source of the electromagnetic wave. Experimental measurements used various shielding materials with the major constituent iron (Fe) in the form of plate for studying shielding effect of electromagnetic wave. The studied parameters were different thicknesses and gaps of the plate. The results show that pure iron plate has the best effect for shielding the magnetic field and its transmission ratio of magnetic field is proportional to distance between the emission source and the shielding plate. Moreover, the shielding plate close to the emission source received better protection.展开更多
电子设备机箱由于散热及外接其他设备等原因需要开有各种孔缝,从而导致其电磁屏蔽效能降低。采用时域有限差分(Finite Difference Time Domain,FDTD)算法仿真分析了不同开孔形状、开孔尺寸、开孔数量及开孔间距的孔缝对电子设备机箱屏...电子设备机箱由于散热及外接其他设备等原因需要开有各种孔缝,从而导致其电磁屏蔽效能降低。采用时域有限差分(Finite Difference Time Domain,FDTD)算法仿真分析了不同开孔形状、开孔尺寸、开孔数量及开孔间距的孔缝对电子设备机箱屏蔽效能的影响,为电子设备机箱提高屏蔽效能工程设计提供依据,同时也为散热结构设计提供电磁兼容方面的参考。展开更多
To develop electromagnetic protection composites with integrated structure -function properties, the three-dimension (3D) braided nickel plated carbon fiber/epoxy resin (Ni-CF3D/EP) composites were prepared based on 3...To develop electromagnetic protection composites with integrated structure -function properties, the three-dimension (3D) braided nickel plated carbon fiber/epoxy resin (Ni-CF3D/EP) composites were prepared based on 3D five-directional braiding, unitary nickel plating and mold compression shaping. The electromagnetic protection properties of Ni-CF3D/EP composites including shielding effective- ness (SE) and reflection loss against plane electromagnetic wave, shielding properties against electromagnetic pulse (EMP) were investigated. The test results show that the novel composites have good electromagnetic protection properties in a wide frequency range of 14 kHz～18 GHz with SE of 42 dB～95 dB, the absorption bandwidth of –5 dB in 2 GHz～18 GHz can reach 10 GHz and the pulse peak SE against EMP is 43.7 dB which can reduce the electromagnetic energy greatly. Meanwhile, the mechanic properties were also investi- gated and the results indicate that the Ni-CF3D/EP composites can replace metal materials for loading-bearing structural applications because of their excellent mechanic properties.展开更多
基金Project supported by National Natural Science Foundation of China （51277181 51177174）
文摘To characterize the shielding effectiveness(SE) of materials against electromagnetic pulse(EMP) that cannot be adequately evaluated by traditional test methods,a transfer function model of SE is proposed.Using homemade broadband coaxial fixture,the SE of a metal fabric material against square-pulse and electrostatic discharge(ESD) EMP is tested in the time domain.The peak SE calculated from the test results matches well with that obtained theoretically.Based on the system identification theory,we propose the transfer function model of SE,which takes the square pulse and human body model ESD EMP data obtained in the tests as training data and takes the machine model as verification data,as well as a second-order expression of the transfer function.Using the transfer function model,the waveforms of the shield-penetrated square-pulse EMP and the ESD EMP are actually predicted.From the perspective of system identification,this accurate prediction of the shielded waveform of EMP provides a reliable way for evaluating SE of materials against EMP.
文摘Carbon microcoils were deposited onto Al2O3 substrates using C2H2/H2 as source gases and SF6 as an incorporated additive gas in a thermal chemical vapor deposition system. At as-grown state, the carbon coils (d-CCs) show the diverse geometry. The geometry-controlled carbon microcoils (g-CMCs) could be obtained by manipulating the injection time of SF6 in C2H2 source gas. The d-CCs with polyurethane (PU) composite (d-CC@PU) and the g-CMCs with PU composite (g-CMC@PU) were obtained by dispersing d-CCs and g-CMCs in PU, respectively. The electromagnetic wave shielding properties of d-CC@PU and g-CMC@PU composites were investigated in the frequency range of 0.25 - 4.0 GHz. The shielding effectiveness (SE) of d-CC@PU and g-CMC@PU composites were measured and discussed according to the weight percent of d-CCs and g-CMCs in the composites with the thickness of the composites layers. On the whole frequency range in this work, the SE of g-CMC@PU composites was higher than those of d-CC@PU composites, irrespective of the weight percent of carbon coils in the composites and the layer thickness. Furthermore, we confirmed that the absorption mechanism, instead of the reflection mechanism, seemed to play the critical role to shield the EMI for not only the g-CMC@PU composites but also the d-CC@PU composites.
文摘This article presents some new experimental data for study the shielding effect of electromagnetic wave. The frequencies of electromagnetic wave are mainly focused on emission of daily electrical equipments, which are normally called “low frequency electromagnetic waves”. In this work, a water pump with maximum magnetic field intensity of ca. 2300 mG was applied as emission source of the electromagnetic wave. Experimental measurements used various shielding materials with the major constituent iron (Fe) in the form of plate for studying shielding effect of electromagnetic wave. The studied parameters were different thicknesses and gaps of the plate. The results show that pure iron plate has the best effect for shielding the magnetic field and its transmission ratio of magnetic field is proportional to distance between the emission source and the shielding plate. Moreover, the shielding plate close to the emission source received better protection.
文摘电子设备机箱由于散热及外接其他设备等原因需要开有各种孔缝,从而导致其电磁屏蔽效能降低。采用时域有限差分(Finite Difference Time Domain,FDTD)算法仿真分析了不同开孔形状、开孔尺寸、开孔数量及开孔间距的孔缝对电子设备机箱屏蔽效能的影响,为电子设备机箱提高屏蔽效能工程设计提供依据,同时也为散热结构设计提供电磁兼容方面的参考。
基金Project supported by Equipment Pre-research Foundation of China (9140A31030110JB3403)
文摘To develop electromagnetic protection composites with integrated structure -function properties, the three-dimension (3D) braided nickel plated carbon fiber/epoxy resin (Ni-CF3D/EP) composites were prepared based on 3D five-directional braiding, unitary nickel plating and mold compression shaping. The electromagnetic protection properties of Ni-CF3D/EP composites including shielding effective- ness (SE) and reflection loss against plane electromagnetic wave, shielding properties against electromagnetic pulse (EMP) were investigated. The test results show that the novel composites have good electromagnetic protection properties in a wide frequency range of 14 kHz～18 GHz with SE of 42 dB～95 dB, the absorption bandwidth of –5 dB in 2 GHz～18 GHz can reach 10 GHz and the pulse peak SE against EMP is 43.7 dB which can reduce the electromagnetic energy greatly. Meanwhile, the mechanic properties were also investi- gated and the results indicate that the Ni-CF3D/EP composites can replace metal materials for loading-bearing structural applications because of their excellent mechanic properties.
