【摘要】 EMC暗室是最常用的电磁兼容测试场地,常受限于低频性能。为了在建造EMC暗室之前,对其低频性能作准确的预测分析,利用平面分层等效模型来模拟暗室中的角锥吸波体,研究了暗室的不同墙面铺设不同吸波材料时其性能的变化情况。仿真结果表明,适当增加钝口吸波体的高度能够显著改善暗室性能;在暗室4个墙位置中,处于第一菲涅尔区的侧墙(与电波传播方向平行)位置的吸波材料更加关键。实测数据的验证,表明上述方法分析暗室低频性能时准确可靠。更多还原

【Abstract】 An accurate method was introduced to simulate and analyze normalized site attenuation(NSA)of anechoic chambers(AC)in the low frequency range(30～100 MHz)with the finite element method(FEM).The practical pyramid absorbers were modeled by way of effective permittivity and planar layers,in order to reduce the mesh size of simulation.Since FEM was good at analyzing high loss,frequency-dependent and anisotropic media,the FEM was adopted to simulate NSA of ACs,because NSA is a very important criterion for measuring the performance of a semi-AC.The principle,details of simulation,as well as programming flow chart was provided.The reflectivity of two heights of pyramid absorbers was also provided for convenience.Next the effects of different heights of absorbers lined in different side walls of an AC were studied with this method in order to find the right configuration of absorbers before constructing an AC.The simulation results show that NSA of ACs can be improved by lengthening pyramid absorbers.The absorbers in the first Fresnel zone are key to ACs;thus its performance can be improved just by optimize the absorbers in this zone.Finally,the simulation results are verified by practical measurement data.In short,the performance of an AC at low frequency can be simulated with this method in a personal computer.更多还原