基于电磁拓扑的多腔体屏蔽效能快速算法

Electromagnetic topology based fast algorithm for shielding effectiveness estimation of multiple enclosures with apertures

提出基于电磁拓扑理论计算开孔多腔体屏蔽效能的快速方法.首先给出双腔体等效电路和电磁拓扑信号流图,并推导孔缝节点处的散射矩阵,给出拓扑网络的散射矩阵方程和传输矩阵方程,获得双腔体的广义Baum-Liu-Tesche(BLT)方程.在此基础上研究了开孔三腔体,包括串型级联三腔体和串并型混合级联三腔体的广义BLT方程.对于串型级联三腔体,其电磁拓扑网络和广义BLT方程在双腔体基础上直接扩展即可获得.而对于串并型混合级联三腔体,通过将位于三腔体公共面上的孔缝等效为三端口网络节点,并根据三端口网络散射参数定义推导获得该节点的散射矩阵,最终得到串并型混合级联三腔体的广义BLT方程.本文方法对双腔体的计算结果与文献结果和实验结果相符合,对3组不同类型和尺寸开孔腔的屏蔽效能的计算结果与时域有限差分法计算结果符合较好.该算法不仅效率高,通过对所有计算结果和实验结果的误差统计分析,表明该算法具有较高的计算准确度.

Shielding effectiveness（SE） estimation for an enclosure with apertures has been an attractive issue in electromagnetic compatibility（EMC） research area. Though many fast algorithms are developed for SE calculation, they mainly focus on the case of single cavity. Moreover, most of these methods neglect the wave coupling through apertures from enclosure to outside. A fast algorithm based on electromagnetic topology is proposed for calculating the SE of cascading multiple enclosures with apertures. In this algorithm, the wave coupling through apertures in both directions is taken into consideration. Firstly, the equivalent circuital model of cascading double enclosures and its signal flow graph of electromagnetic topology are given, followed by the derivation of scattering matrix of apertures node. Then propagation relationships at tube level and reflection relationships at node level are derived. As a result, the general BLT（Baum-LiuTesche） equation for voltage calculation at each node is established. Two major categories of cascading three enclosures with apertures are investigated. For serially cascading three enclosures, the general BLT equations are extended on the basis of BLT equations for cascading double enclosures, since the structures are a simple extension of them. For hybrid serially-parallelly cascading three enclosures, the common walls between the main enclosure and two sub-enclosures are considered as a topological node represented by a three-port network, whose scattering matrix is derived according to the definition of scattering parameters. Consequently, the general BLT equations for hybrid serially-parallelly cascading three enclosures are developed. Compared to the algorithms presented in the relevant literature, the topology-based algorithm proposed in this paper can not only calculate the shielding effectiveness for cascading multiple enclosures, but also lead to more accurate results in that the impedance of apertures is obtained through using diaphragms model. In order to validate the proposed method, a cascading double enclosures from a literature is chosen as an example. Calculated SE results are in good agreement with those in the literature. Then, three enclosures with different configurations and dimensions are also designed to validate the proposed method. Results from the proposed method are compared with those from the finite difference time domain（FDTD） method, and they are found to be in good agreement with each other. Experimental results also demonstrate the validation of the proposed method. Especially, the proposed method takes far less time to calculate SE than for FDTD method.