内置介质板的开孔箱体屏蔽效能电磁拓扑模型

针对内置介质板的开孔矩形金属箱体的特点,基于电磁拓扑(EMT)理论和BLT方程,建立任意平面波照射下箱体屏蔽效能的EMT模型,推导近似计算解析式,并分析介质板的厚度、材料和位置及平面波的极化角和入射角等因素对屏蔽效能的影响。结果表明:加装介质板可有效抑制箱体谐振,显著提高谐振点附近的屏蔽效能,但对远离谐振点频域的屏蔽效能影响不大;介质板厚度越大,屏蔽效能越高;不同谐振点处存在最佳电导率和最佳相对介电常数,使得谐振的抑制作用最强,屏蔽效能最高;介质板置于箱体前端比后端屏蔽效能高;不同谐振点处屏蔽效能的最大值在不同的介质板位置处取得;平面波的极化角越大,入射方位角越大,仰角越小,屏蔽效能越高。计算结果与仿真结果一致,证明了该文建立的EMT模型的有效性。该方法较等效传输线法(TLM)计算精度更高,尤其是在高频范围;较数值方法和全波仿真计算方法速度更快。该文工作对屏蔽箱体的设计具有指导意义。

Electromagnetic Topology Model for the Shielding Effectiveness of an Apertured Enclosure with a Lossy Dielectric Layer

An electromagnetic topology (EMT) model for the shielding effectiveness (SE) of an apertured rectangular metallic enclosure with a lossy dielectric layer against an oblique incident plane wave is established according to the EMT theory and BLT equation.The approximate analytical formulas of the SE are derived,and the effect of various factors including the thickness,the material and the position of the lossy dielectric layer,the polarization and incident angles of the plane wave on the SE is analyzed based on the EMT model.The results indicate that the lossy dielectric layer can suppress the resonance,leading to great improvement on the SE for frequencies near the resonance but alnost no effect on the SE for frequencies far away from the resonance.The larger the thickness of the lossy dielectric layer is,the higher the SE will be.There exist the optimum conductivity and relative permittivity for different resonant frequencies,which leads to the strongest suppression effect and the maximum values of the SE.The SE for the lossy dielectric layer in the front of the enclosure is higher than that when it is at the back of the enclosure.The maximum values of the SE are obtained at different positions of the lossy dielectric layer for different resonant frequencies.The larger the polarization angle and the azimuth angle are,and the smaller the elevation angle is,the higher the SE will be.The results are in good agreement with those of the simulation.The proposed EMT model is much faster than the transmission line method (TLM),especially in the high frequency range,and requires less time than numerical methods and CST in calculating the SE,which is helpful for guiding the design of shielding enclosures.