基于BLT方程的双层腔体屏蔽效能计算方法

基于波导理论,将BLT方程进一步拓展,提出一种可快速、准确地计算双层腔体内任意点屏蔽效能的方法。首先将腔体壁孔所在面等效为二端口网络,腔体等效为两端短路的波导,建立信号流图。引入孔阻抗计算二端口网络散射参数,依据信号流图构建广义BLT方程,得到内层腔体中心线上点的屏蔽效能;然后根据波导理论的场分布特性,推导出腔体内任意点电场与腔体中心线上电场的关系,最终得到内层腔体内任意点的屏蔽效能。将计算结果与等效电路法及CST数值仿真结果对比,三者吻合良好,计算结果在较大频率范围内比等效电路法精度更高。该方法可以准确预测双层腔体在0~2.5GHz范围内所有谐振点,有助于分析腔体谐振现象,且计算效率较高,占用资源大幅减少。

BLT equation-based approach for calculating shielding effectiveness of double layer rectangular enclosures with apertures

In this paper, the BLT equation is extended to calculate the shielding effectiveness (SE) of arbitrary observation points located in a double layer rectangular enclosure with an aperture on the basis of waveguide theory. Firstly, the surface containing an aperture of enclosure is equivalent to a two-port network, and the enclosure is equivalent to a rectangular waveguide shorted at each end. The signal flow graph can be built according to the equivalent model above. The aperture impedance is employed to calculate the scatter parameters of the two-port network, and the general BLT equation for SE of observation point on center line can be established. Then, the SE of arbitrary observation point can be obtained by using the waveguide theory. Finally, the results from our method are compared with that from CST simulation. The SE from our method reaches a good agreement with CST, and all the resonance frequencies are correctly predicted under 2.5 GHz. Our method takes less time and computer resource compared to CST, and it is helpful for analysis of resonance phenomenon and can easily get the influence of enclosure parameters.