共查询到20条相似文献,搜索用时 78 毫秒
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《Electromagnetic Compatibility, IEEE Transactions on》2008,50(4):928-939
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WANG Liu-ping 《中国邮电高校学报(英文版)》2008,15(4):81-85
New shielding material has become an alternative to traditional metal to shield boxes from electromagnetic interferences. This article introduces the theory of transmission line method to study the shield boxes made of a new sort of material, and then expands the fundamental formulas to deal with the cases of multiple holes and polarization with arbitrary angle. By means of genetic algorithms with the aid of a three dimensional simulation tool, the damping of electromagnetic resonances in enclosures is researched. The computation indicates that under resonant frequency, electromagnetic resonance results in low, even negative shielding coefficient; whereas, for the same areas, shielding effectiveness of a single hole is worse than that of multiple holes. Shielding coefficient varies when polarization angle increases, and the coupled field through the rectangular aperture with the long side parallel to the thin wire is much weaker than that with the long side vertical to the thin wire. By using the metallic-loss dielectric layer of optimized calculation on the internal surface of the cavity, the best result of resonance suppression has been realized with the same thickness of coating. Finally, according to the calculation result, suggestions for shielding are proposed. 相似文献
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An EMI estimate for shielding-enclosure evaluation 总被引:7,自引:0,他引:7
Min Li Drewniak J.L. Radu S. Nuebel J. Hubing T.H. DuBroff R.E. van Doren T.P. 《Electromagnetic Compatibility, IEEE Transactions on》2001,43(3):295-304
A relatively simple, closed-form expression has been developed to estimate the EMI from shielding enclosures due to coupling from interior sources through slots and apertures at the enclosure cavity modes. A power-balance method, Bethe's (1944) small-hole theory, and empirically developed formulas for the relation between radiation, and slot length and number of slots, were employed to estimate an upper bound on the radiated EMI from shielding enclosures. Comparisons between measurements and estimated field strengths suitably agree within engineering accuracy 相似文献
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屏蔽材料对电场波,磁场波和电磁波提供的屏蔽效能是从理论上获得的.但是,实际情况下,由于屏蔽机箱,机柜,房间或运载器并不是完全封闭的,都有这种或那种必要的穿孔或孔洞,造成完整性损失,故常常达不到这种屏蔽效能.本文讨论屏蔽完整性损失,屏蔽完整性保证措施及如何恢复屏蔽完整性的实际应用. 相似文献
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The physics of shielding by a metallic enclosure is discussed. Simple engineering formulas in the frequency and time domains are deduced from a rigorous formulation to calculate the cavity fields for certain canonical enclosure shapes. These simple formulas are generalized so as to be applicable to enclosures of arbitrary shape. The great difference in shielding effectiveness between enclosures and planar slabs is pointed out. 相似文献
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A hybrid FD-MoM technique for predicting shielding effectiveness of metallic enclosures with apertures 总被引:1,自引:0,他引:1
In this paper, a hybrid technique combining the finite-difference (FD) method and the method of moments (MoM) in the frequency domain is proposed to predict the shielding effectiveness of rectangular conducting enclosures with apertures under external illumination. The interior and exterior regions of the enclosure are analyzed separately by employing the field equivalence principle. Internal electromagnetic fields are discretized using the (FD) method, while external fields are formulated by the MoM. Enforcement of continuity of the tangential magnetic field over the aperture surface gives the desired equation to solve for electromagnetic fields everywhere. Numerical results for the shielding effectiveness of a rectangular cavity with apertures calculated by the new hybrid technique are presented and validated by comparing with experimental data. 相似文献
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电子设备屏蔽效能的好坏直接影响着电路系统的电磁兼容性能,而其金属壳体上的孔缝造成的电磁泄漏是一个不容忽视的问题。以内置电路板的开缝屏蔽壳体为研究对象,应用FEM(有限元法)分析了不同的孔缝尺寸、电路板尺寸、电路板位置对壳体屏蔽效能的影响。并进一步研究了电路板上金属微带线受电磁干扰信号影响而产生感应电流的变化规律:走线越长,离缝隙越近,感应电流数值越大,其峰值出现在腔体的谐振频率处。根据计算结果,提出了优化设计屏蔽腔及其腔内电子设备的建议。本文研究对于更为有效地利用金属壳体防御电磁干扰,提高系统电磁兼容性具有指导意义。 相似文献
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The effect of single welding flaws on the electromagnetic (EM) effectiveness of welded steel enclosures has been assessed. The possibility of resonant reradiation by these flaws has been examined, using resonance calculations and direct EM measurements. Using these results, a method was developed for assessing shielding quality of hardened military structures, such as SAFEGUARD sites, and EM shielded enclosures. The effect of four formns of incomplete welds on the shielding effectiveness of welded steel enclosures was determined for single flaws. Electromagnetic shielding effectiveness tests (from 10 kHz to 10 GHz) were made on various test specimens of 11-gauge steel plate. These test specimens included butted plates with incomplete welds and plates with single holes and slots cut into them. Tests simulated the worst cases of cracks, lack of fusion, and porosity. Shielding effectiveness as a function of flaw size was determined for each defect, and a critical or transition flaw size was determined for each of three frequency bands and at the 100-dB shielding level for each type defect. The measured results were compared to a calculated resonance response by modeling the flaws as slot antennas. 相似文献
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《Electromagnetic Compatibility, IEEE Transactions on》2009,51(2):284-292
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5G通信技术的迅速发展和产业化进程给电子设备的电磁屏蔽设计带来了严峻挑战。5G通信中24 GHz以上的电磁波极易通过电子设备屏蔽外壳上的各种孔缝耦合进入电子设备内部,影响设备的正常工作。针对常规散热孔设计难于适应5G通信发展需求,提出了一种介质开孔型频率选择表面(FSS)结构。该结构在不影响设备通风散热的条件下,实现对28 GHz频段信号的电磁屏蔽。经过全波分析方法仿真,所设计的FSS结构在28 GHz频段电磁屏蔽效能(SE)达30 dB以上,带宽大于2 GHz。无论是TE还是TM极化电磁波,在0°~60°入射范围内具有良好的电磁屏蔽稳定性。 相似文献
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An Efficient MoM Formulation for the Evaluation of the Shielding Effectiveness of Rectangular Enclosures With Thin and Thick Apertures 总被引:2,自引:0,他引:2
A detailed analysis of the effects of finite-thickness apertures on the shielding properties of a rectangular metallic box is carried out through an efficient full-wave code based on the method of moments in the spatial domain. An incident plane wave having arbitrary polarization and incidence angle is assumed as a field source. The evaluation of the cavity Green function is accelerated by an application of the Ewald sum technique with a novel Ewald splitting parameter valid for high frequencies, and a recently proposed integral-equation-based approximate model of the aperture thickness is also applied. Numerical results are validated by comparisons with those obtained by means of commercial codes based on different numerical approaches and show rigorously that the effects of a finite thickness can usually be neglected (at least, at sufficiently low frequencies), with the noticeable exception of long slots. The effects of common limiting assumptions adopted in the study of enclosures with zero-thickness apertures are also investigated. 相似文献
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《Electromagnetic Compatibility, IEEE Transactions on》2008,50(4):770-782
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Validation of modal/MoM in shielding effectiveness studies of rectangular enclosures with apertures 总被引:1,自引:0,他引:1
Rajamani V. Bunting C.F. Deshpande M.D. Khan Z.A. 《Electromagnetic Compatibility, IEEE Transactions on》2006,48(2):348-353
This paper discusses the validation of Modal/method of moments (MoM) including cases when the apertures are made as big as the wall of the enclosure (equivalent to having one side of the cavity open). The validation is done using field computations involving bodies of arbitrary shape (FEKO), a commercially available code. The results show that Modal/MoM predicts the results close to the analytical results of Robinson et al. Electron. Lett., 32 (17), 1996; Robinson et al., IEEE Trans. Electromagn. Compat., 40 (3), 240-247, 1998 for single-aperture cases and for most double-aperture cases. Also, for the cases of considering oblique incident plane waves, through validation, it has been found that Modal/MoM can predict the shielding effectiveness close to measured results for smaller angles and not for larger angles of incidence due to the edge effects. In this work, the shielding effectiveness is calculated at only one point, the center of the cavity assuming it to be the worst case. This work discovers the limitation of Modal/MoM for certain applications. 相似文献
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《Electromagnetic Compatibility, IEEE Transactions on》2009,51(2):293-300
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小孔矩形腔体屏蔽特性的研究 总被引:3,自引:0,他引:3
本文提出了有孔腔体远、近场电磁屏蔽效能的计算方法,体研究了矩形腔体的屏蔽特性,讨论了各类孔对屏蔽能的影响程度。数值结果表明,理论计算与实验数据吻合较好。 相似文献
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Robinson M.P. Turner J.D. Thomas D.W.P. Dawson J.F. Ganley M.D. Marvin A.C. Porter S.J. Benson T.M. Christopoulos C. 《Electronics letters》1996,32(17):1559-1560
An analysis is presented of the shielding effectiveness (SE) of a rectangular enclosure with an aperture in one face. The enclosure is treated as a length of rectangular waveguide and the aperture as a length of coplanar strip transmission line. Theoretical values of SE agree with measurements for a range of enclosures, apertures and frequencies. The variation of SE with position in the enclosure is also correctly predicted 相似文献
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Shielding Theory of Enclosures with Apertures 总被引:9,自引:0,他引:9
This paper develops the theory of EM radiation from metallic enclosures with apertures, excited by an internal source at frequencies below the fundamental resonance of the enclosure. The enclosure with an aperture is analyzed from two different points of view: as a cavity with a small aperture in a wall, and as a waveguide section short-circuited at one end and open at the other. Rectangular geometries are used throughout, since these are by far the most commonly encountered in practical enclosures and cabinets. Using the corresponding dyadic Green's functions, the fields generated inside the enclosure by some simple sources are determined. The fields radiated through small apertures in a cavity are determined using Bethe's theory of diffraction by small holes. The radiation from an open waveguide is calculated with the help of field-equivalence theorems, with assumptions applicable to the case of evanescent waves. The final step is to derive expressions for the " insertion loss" of the shield, defined as the ratio of the field strength at a point external to the shield, before and after the insertion of the enclosure. To do so, the effect of the shield upon the input impedance of the antenna is analyzed, and expressions obtained for the applicable cases. The resulting insertion-loss expressions are numerically evaluated for some representative cases, and graphically compared with a series of measurements performed to obtain experimental confirmation. Very good agreement is obtained in all cases, establishing the validity of the analysis. 相似文献
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HIRF penetration through apertures: FDTD versus measurements 总被引:8,自引:0,他引:8
Georgakopoulos S.V. Birtcher C.R. Balanis C.A. 《Electromagnetic Compatibility, IEEE Transactions on》2001,43(3):282-294
The penetration of high-intensity radiated fields (HIRF) into conducting enclosures via apertures is an EMI issue that is relevant to all aviation. The stories are numerous, of disrupted communications, disabled navigation equipment, etc., due to the effects of EM sources external to the aircraft. Here, the FDTD method is used to predict the shielding effectiveness of conducting enclosures with apertures, and the numerical results are compared with measurements. Several issues related to the FDTD analysis of highly resonant and high-quality factor (high-Q) structures, such as windowing and acceleration techniques, are examined and discussed 相似文献