开孔矩形腔体电磁泄漏特性的研究

发布时间：2018-03-16 20:42

  本文选题：电磁泄漏　切入点：电磁屏蔽　出处：《华北电力大学》2015年硕士论文　论文类型：学位论文

【摘要】：电磁屏蔽是通过场耦合途径抑制电磁干扰的主要技术。它的实现可通过使用一个金属外壳包围干扰源,以降低其场泄漏,或减少外部磁场强度来筛选敏感对象。虽然一个封闭的金属外壳对于电磁波具有非常高的屏蔽效能SE,但是因为一些实际功能,外壳上不可避免的会出现小孔,小孔的存在会导致SE显著减少。通常,在用于SE测量的标准方法中,一个屏蔽外壳的SE被定义为没有外壳时给定点的场强与外壳存在时该点的场强之比。其中,要求场源被放置在外壳外部。换句话说,场的观察点是在外壳内部,其优点是减少了其他不必要的干扰源对所接收场强的潜在影响。所以,在许多文献中对于SE的评价都是对于外部场源。然而,相反的情况下,源在外壳内部也具有实际意义,值得予以关注。原则上,这两种情况可根据互易原理相互转化。然而,由于对“外部源”实例尚未进行全面和深入的研究,我们不能为每个“内部源”实例找到合适的“对偶问题”。例如,对于后者,在近场区域中的场分布是主要考虑的问题,但是对于前者,激励源(通常假设是平面波)在远场区定位明显。本文首先基于模式展开方法得到的解析公式,计算了电偶极子天线激励下矩形屏蔽体的电磁场分布,获得了屏蔽体内壁和内部的电场和磁场分布特性。接着,提出了一种用于计算开孔矩形腔体电磁泄漏场的解析理论模型。该理论模型先基于模式展开法求解封闭腔场,进而依据Bethe小孔耦合理论将泄漏场与封闭腔场用等效偶极子关联。该模型可以考虑波频率、场源位置、开孔位置及场强观测点位置等因素的影响,计算结果与全波仿真结果一致。最后,提出了一种用于计算封堵孔矩形腔体电磁泄漏的解析理论模型。该模型同样先基于模式展开法求解封闭腔场,进而用平面波垂直入射无限大导体的边界条件近似计算出透射场的切向分量,最后通过面磁流在空间产生的电场求解出封堵孔的泄漏场分布。
[Abstract]:Electromagnetic shielding is the main technology to suppress electromagnetic interference through field coupling. It can be realized by using a metal shell to surround the interference source to reduce its field leakage. Or reduce the external magnetic field intensity to screen sensitive objects. Although a closed metal shell has a very high shielding efficiency for electromagnetic waves, because of some practical functions, there are inevitable small holes in the shell. The presence of small holes can result in a significant decrease in SE. Generally, in standard methods for SE measurement, SE of a shielded shell is defined as the ratio of the field strength given to a given point in the absence of a shell to the field strength of the point at which the shell exists. The field source is required to be placed outside the shell. In other words, the field's observation point is inside the shell, which has the advantage of reducing the potential impact of other unnecessary interference sources on the received field strength. In many literatures, the evaluation of SE is for external field sources. However, on the contrary, the source also has practical meaning inside the shell and deserves attention. In principle, the two cases can be converted to each other according to the reciprocity principle. Since there has not been a comprehensive and in-depth study of "external source" instances, we cannot find an appropriate "dual problem" for each "internal source" instance. For the latter, for example, the field distribution in the near-field region is the main consideration. But for the former, the excitation source (usually assumed to be a plane wave) is obviously located in the far field. Firstly, based on the analytical formula obtained by the mode expansion method, the electromagnetic field distribution of the rectangular shielding body excited by the electric dipole antenna is calculated. The distribution characteristics of electric field and magnetic field in the shielding wall and inside are obtained. Then, an analytical theoretical model for calculating electromagnetic leakage field of rectangular cavity with open hole is proposed. The theoretical model is based on the mode expansion method to solve the closed cavity field. Furthermore, the leakage field and the closed cavity field are correlated by equivalent dipole according to the Bethe small-hole coupling theory. The model can consider the influence of the wave frequency, the location of the field source, the location of the opening hole and the position of the observation point of the field strength, and so on. The calculated results are consistent with the full wave simulation results. Finally, an analytical theoretical model for calculating electromagnetic leakage of a rectangular cavity is proposed. The model is also based on the mode expansion method to solve the closed cavity field. Then the tangential component of the transmission field is approximately calculated by the boundary condition of the infinite conductor vertically incident by plane wave. Finally, the leakage field distribution of the sealing hole is solved by the electric field generated by the surface magnetic flow in the space.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN03

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