开孔矩形腔体电磁泄漏特性的解析研究

Analytical formulation for electromagnetic leakage from an apertured rectangular cavity

本文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.本文计算分析了相关因素对电磁屏蔽效能的影响规律,并给出了物理解释.结果表明近场屏蔽效能小于远场屏蔽效能,且近场区电场屏蔽效能与磁场屏蔽效能并不相同.

An analytical formulation has been developed for the electromagnetic leakage from an apertured rectangular cavity excited internally by an electric dipole. The leakage fields are represented by the equivalent electric and magnetic dipoles located at the aperture center with their dipole moments related to the ＂closed cavity＂ field within the framework of the Bethe＇s small aperture coupling theory. The ＂closed cavity＂ field is obtained by using the mode-expansion method.In this formulation, the leakage field can be expressed as a function of the frequency, the source point, the field point,and the position of the aperture. The formulation then is employed to analyze the influences of the above factors on the shielding effectiveness and the corresponding physical mechanisms are also illuminated. Comparison with the full wave simulation software CST has verified the formulation over a very broad frequency range. It is shown that the near-field shielding effectiveness is smaller than the far-field one, and the electric shielding effectiveness is different from the magnetic one in the near-field zone.