共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
Cheng-Nan Chiu Chun Hsiung Chen 《Electromagnetic Compatibility, IEEE Transactions on》1995,37(1):109-113
The plane-wave shielding properties of advanced composite cylindrical shells are analyzed. Based on a rigorous theory that clearly displays the propagating nature of the electromagnetic field in an anisotropic, multi-layered, and lossy cylindrical shell structure. In this study, numerical results are presented for graphite/epoxg fiber-reinforced composite shells. In particular, the parameters that influence the shielding effectiveness, such as material properties, cylinder configuration, fiber orientation, and incident wave polarization, are investigated in detail. For design purposes, an empirical formula is also proposed to estimate the shielding effectiveness in the lower frequency range. Finally, a sharp reduction of shielding performance due to resonance is also examined 相似文献
3.
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
4.
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
5.
针对电子设备的结构特点,依据某型(ATR)加固机箱结构设计的电磁兼容性原理和电磁兼容要求,阐述了缝隙、孔、洞在机箱上对电磁屏蔽效果的影响。提出在结构工艺上保证机箱的电磁屏蔽和抑制电磁干扰的具体方法,有效的解决了机箱的电磁兼容超标问题。并由此对机箱电磁兼容特性进行了结果的验证,证明了采用屏蔽措施后对机箱屏蔽效果有了较高的提升。 相似文献
6.
7.
Olyslager F. Laermans E. De Zutter D. Criel S. De Smedt R. Lietaert N. De Clercq A. 《Electromagnetic Compatibility, IEEE Transactions on》1999,41(3):202-213
This paper presents a detailed study of the shielding effectivity properties of metal enclosures. Measurements in anechoic chambers are compared to full-wave electromagnetic simulations. The study is not limited to the frequency range below the first resonance frequency. Different aspects are investigated such as the influence of the size, position and number of apertures, and the effect of the presence of metal plates and of absorbing materials. Where possible, the specific behavior of the shielding effectivity is explained theoretically and existing simple design rules are assessed 相似文献
8.
9.
Min Li Nuebel J. Drewniak J.L. DuBroff R.E. Hubing T.H. Van Doren T.P. 《Electromagnetic Compatibility, IEEE Transactions on》2000,42(3):265-275
Aperture arrays designed to provide airflow through shielding enclosures can provide part of the coupling path from interior sources to external electromagnetic interference (EMI). In this work, radiation through aperture arrays is investigated numerically and experimentally. FDTD modeling is compared with measurements on aperture arrays in a test enclosure. The method of moments (MoM) is also utilized to study radiation from apertures and to investigate the mutual coupling between apertures in an infinite conducting plane. A simple design equation for the relation between aperture size and number and shielding effectiveness is proposed 相似文献
10.
Cooling of electronics is normally achieved using air passing through apertures in the enclosure; as a result the shielding effectiveness of the shielded enclosure is reduced. In this paper, the design of a new cooling structure and its evaluation in a wind tunnel is presented. The developed design presented here is a double heat sink in extruded aluminum. Into one side of the heat sink, the printed circuit boards (PCBs) are inserted and enclosed by a complementary shielding surface. The other side of the heat sink is cooled by forced ventilation. The heat transport between these parts is completely inside the same body, without any heat flow interruptions. Tests carried out on a prototype have shown that the performance of the cooling structure is satisfactory for electronic cooling. An additional electromagnetic compatibility (EMC)-test has also elucidated the satisfactory shielding effectiveness of the structure. The cooling structure is scaleable and can accommodate for both future smaller printed circuit boards (PCBs) and those of today. The entire enclosure is furthermore based on near-standard items, which allows it to be inexpensive in high volume production. 相似文献
11.
Efficient EMC Simulation of enclosures with apertures residing in an electrically large platform using the MM-UTD method 总被引:2,自引:0,他引:2
The moment method coupled with the uniform theory of diffraction is employed in this paper to simulate the electromagnetic shielding performance of an enclosure with apertures residing in a very large platform, in which the moment method is used to accurately model the enclosure with apertures, and the influence of the large platform is efficiently calculated by using the uniform theory of diffraction. These two methods are coupled through the tangential electromagnetic fields on the apertures of the enclosure. In this paper, the accuracy of this coupled method developed is validated, and we apply this method for simulating the shielding effectiveness with the sources inside/outside the enclosure. The simulation results show that this coupled technique is able to simultaneously model the effects of the smaller structures and the large platform on the total electromagnetic property. It further demonstrates that this coupled method is a very flexible and powerful technique for analysis of the electromagnetic compatibility problems with smaller objects mounted on a larger platform. 相似文献
12.
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
13.
14.
Coupling studies and shielding techniques for electromagnetic penetration through apertures on complex cavities and vehicular platforms 总被引:11,自引:0,他引:11
Eng Swee Siah Sertel K. Volakis J.L. Liepa V.V. Wiese R. 《Electromagnetic Compatibility, IEEE Transactions on》2003,45(2):245-257
The multilevel fast multipole moment method is employed to compute the electromagnetic coupling and shielding of various aperture-coupled metallic enclosures. A phenomenological study of electromagnetic coupling, due to various slot shapes and sizes, with or without the presence of wire penetration is conducted. These slots are situated on over-moded cavities and two methods are proposed to mitigate slot coupling into the cavity's interior. As part of this work, we also investigate the coupling through similar slots and apertures within a complex platform such as an automobile. The proposed methods have shown to increase shielding by as much as 5-35 dB within the frequency range of interest. 相似文献
15.
Leviatan Y. Harrington R. Mautz J. 《Antennas and Propagation, IEEE Transactions on》1982,30(6):1153-1165
The problem of electromagnetic coupling from one region to another through an aperture-to-cavity-to-aperture system is specialized to the case of electrically small circular apertures on the axis of a cylindrical cavity of circular cross section for the transverse electromagnetic (TEM) and transverse electric (TE) cases. A simple equivalent circuit for the coupling system is developed. It is found that for certain cavity depths an exceptionally large amount of electromagnetic energy can be transmitted, and that for identical apertures the transmission cross section of the system is independent of the common radius of the apertures as well as the radius of the cavity. 相似文献
16.
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
17.
Martin T. Backstrom M. Loren J. 《Electromagnetic Compatibility, IEEE Transactions on》2003,45(2):229-237
A novel method to include models of complex apertures into the finite-difference time-domain (FDTD) method is presented. Instead of resolving the geometrical details of the aperture, the aperture is treated as a magnetic dipole. The properties of the magnetic dipole moment are determined using the measured transmission cross section of the aperture. This semi-empirical model permits inclusion of complex apertures in FDTD simulations where the smallest dimension of the aperture is only a fraction of the FDTD cell size. Two types of complex apertures positioned in the top panel of a realistic enclosure have been modeled using the semi-empirical model in FDTD. Comparisons between simulated and measured shielding effectiveness of the enclosure are presented, and the results show that complex apertures can indeed be represented by simple magnetic dipoles in shielding effectiveness simulations. 相似文献
18.
为控制电子设备工作温度,设备机箱上一般设计有用于通风散热的孔阵.孔阵的存在造成了电磁能量的泄漏,导致设备内外电磁信号的相互干扰.当辐射源与屏蔽体间距及相邻屏蔽设备间距满足近场条件时,必需进行近场屏效分析.本文基于电磁场理论,阐述了孔阵屏蔽效能的有限元计算原理,对比分析了近场数值计算屏效和基于平面波理论计算屏效两种方法,研究了相关参数对近场屏效的影响规律,提出了提高近场屏效的设计方法,并在此基础上对不同形状孔阵进行了屏效数值计算.理论分析和仿真计算结果表明,基于平面波理论的孔阵屏效计算方法不能用于近场屏效计算,数值法是近场屏效计算的有效方法;数值仿真表明,在保证孔阵面积不变的条件下,通过减小孔规格与辐射源波长的比值、增加孔数可以提高近场屏效,但工程中常用的三种形状的孔阵近场屏效基本相同. 相似文献
19.
为研究任意入射角度平面波对多面开孔腔体的孔缝耦合效应,根据矢量分析和矩形波导内场强分布对等效传输线法进行了改进,计算了多面开孔腔体内任意位置的屏蔽效能。将改进等效传输线法计算结果与CST仿真结果、实验测量结果进行比较,验证了改进等效传输线法的正确性,相比数值计算方法,改进等效传输线法所需计算时间和内存更少。采用改进等效传输线法对相同体积不同尺寸的多面开孔腔体的屏蔽效能进行了研究,结果表明:在相同体积下,腔体为正方体时的屏蔽效能和其他尺寸腔体的屏蔽效能基本一致,但是正方形的屏蔽效能极小值点大大减少,从而减少了电子设备受电磁干扰的几率。 相似文献