开孔腔体的近场屏蔽效能研究

发布时间：2018-11-13 18:52

【摘要】：随着电子技术向高频化和高集成化发展,几乎所有的设备都处于周围电磁场的潜在影响中,电磁兼容越来越受到重视。金属腔体具有良好的电磁屏蔽效果,是电磁兼容的重要手段。由于设备通风、散热以及外界观察的需要,腔体上不可避免的存在开孔,而开孔是影响腔体屏蔽效能的关键因素。由于设备共存于一个紧凑的空间中,使得敏感设备常常处于干扰源的近场区。在近场区,电磁场强度和波阻抗具有不均匀性,一些远场的结论不再适用,因此,研究开孔腔体的近场屏蔽效能具有十分重要的意义。本文基于时域有限差分法,分析了开孔腔体的近场屏蔽效能的影响因素及其规律。基于正交试验法,分析了各因素对开孔腔体的近场屏蔽效能影响的主次顺序,并对屏蔽效果进行了优化。论文主要从以下几方面展开:首先,介绍时域有限差分法的基本原理及差分格式,Courant稳定性条件。推导了自由空间与理想导体的边界条件,并据此得出了屏蔽腔体的设置方法。深入研究了 Gedney完全匹配层,通过编制程序对吸收效果进行了验证。对激励源的引入进行了分析和研究,介绍了常用的随时间变化的源和常用的激励源的设置方法。其次,建立了开孔腔体的屏蔽效能分析模型,引入平面波,编制程序得到屏蔽效能的数值解,与等效传输线法的结论吻合,证明了算法的有效性。引入了电偶极子源,研究了开孔大小、开孔形状、孔源距离、激励源和观察点偏移距离等不同因素对开孔腔体的近场屏蔽效能的影响。最后,设计了一套正交试验,通过直观分析和方差分析,得到了各因素对屏蔽效能影响的主次顺序,确定了影响因素的最优化水平组合,对屏蔽效能进行了优化。本文研究工作及成果为开孔腔体在近场环境中电磁兼容的设计提供了理论依据,对工程实践具有一定的指导意义。
[Abstract]:With the development of electronic technology towards high frequency and high integration, almost all equipments are affected by electromagnetic field, and EMC is paid more and more attention. Metal cavity has good electromagnetic shielding effect and is an important means of electromagnetic compatibility. Due to the need of ventilation, heat dissipation and external observation, there is an inevitable opening in the cavity, which is the key factor affecting the shielding effectiveness of the cavity. Because the devices coexist in a compact space, sensitive devices are often in the near field of the interference source. In the near field, the electric magnetic field intensity and wave impedance have inhomogeneity, and some far-field conclusions are no longer applicable. Therefore, it is of great significance to study the near-field shielding efficiency of the cavity. Based on the finite-difference time-domain method, the factors affecting the near-field shielding effectiveness of an open-hole cavity and its law are analyzed in this paper. Based on the orthogonal test, the primary and secondary order of the influence of various factors on the near-field shielding effectiveness of the cavity is analyzed, and the shielding effect is optimized. Firstly, the basic principle of FDTD method, the difference scheme and Courant stability condition are introduced. The boundary conditions of free space and ideal conductor are derived, and the method of setting shielding cavity is obtained. The perfectly matched layer of Gedney is studied in depth, and the absorption effect is verified by programming. The introduction of excitation sources is analyzed and studied, and the methods of setting up common sources with time and common excitation sources are introduced. Secondly, the shielding effectiveness analysis model of an open-hole cavity is established. The numerical solution of shielding effectiveness is obtained by introducing plane wave, which is in agreement with the conclusion of the equivalent transmission line method, and proves the validity of the algorithm. The influence of different factors, such as hole size, hole shape, hole source distance, excitation source and observation point offset, on the near-field shielding efficiency of an open-hole cavity is studied by introducing an electric dipole source. At last, a set of orthogonal experiment is designed. Through the analysis of visual analysis and variance, the primary and secondary order of the influence factors on shielding effectiveness is obtained, and the optimal level combination of the influencing factors is determined, and the shielding effectiveness is optimized. The research work and results in this paper provide a theoretical basis for the design of electromagnetic compatibility in the near-field environment of an open-hole cavity, and have a certain guiding significance for engineering practice.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN03

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