【作者】 聂小春；

【导师】 葛德彪；

【作者基本信息】 西安电子科技大学 ， 电磁场与微波技术， 2000， 博士

【摘要】 复杂目标的电磁散射分析在许多军事及民用领域具有广泛应用，而混合算法是解决上述问题的一条有效途径。本文着重研究表面具有电小槽缝结构的电大目标散射及其相关问题，其中包括导电平面上的腔体及孔缝散射等。作者所做工作及主要研究成果如下：1、首次将广义网络原理应用于复杂电磁散射问题的混合算法分析中，并在 此基础上开发出IPO-MoM、IPO-FDTD及IPO-BIM等多种混合法计算 软件。本文方法的最大特点是使高频近似方法和低频数值方法的分析完 全独立，并且考虑了目标表面各部分间的主要耦合因素。利用所编制的 混合算法计算软件，首次系统地考察了电大目标各部件之间、电小槽缝 与电大目标之间以及电小槽缝各部分之间的互耦对目标散射特性的影 响，从而为复杂目标雷达截面的优化设计提供了依据。2、将广义网络原理应用于导电平面上的任意腔体的散射分析，给出了包括 具有复杂终端的腔体模型在内的多个算例。该方法的最大特点是在计算 中可对腔体进行任意拆解和组合，某些常用腔体段的导纳矩阵可保存下 来以重复调用，因此，该方法可做为一种腔体的计算机辅助设计工具服 务于工程应用。3、首次提出一种利用槽缝口径等效磁流提取其口径导纳矩阵的方法。对于 结构十分复杂的槽缝结构，本文提出在开口腔体的情况下首先提取槽缝 在各种激励条件下的口径等效磁流，然后通过广义网络方程变换的方式 建立槽缝的网络模型，有效解决了直接模拟时所遇到的难题。4、首次利用边界积分法及连接算法分析复杂的孔缝耦合问题。连接算法的 引入极大地缓解了计算机内存对孔缝尺寸的限制，提高了分析效率，还 使复杂孔缝的处理成为可能。该项研究成果可望应用于电磁兼容、微波 与光器件以及缝隙天线等多个电磁领域。5、分析了有限厚导电平板上二维孔缝的散射及传输特性，得到了一些在实 际工程应用中具有重要参考价值的结论。另外，该方法还可用位于厚度 极小的导电平板上的实际孔缝模型来模拟位于无限薄平板上的简化孔缝 模型，从而使二者的分析得到统一。更多还原

【Abstract】 Evaluation of electromagnetic scattering by complex objects may be of interest in many military and civil areas. In this dissertation, several kinds of hybrid techniques that combine some high-frequency techniques with low-frequency methods are proposed to deal with this problem. Main efforts are put on the computation of scattering by electrically large bodies with small cracks and cavities on their surfaces. Besides, some related problems such as scattering from cavities and slits in a conducting plane are also investigated. The hybrid techniques in this paper provide efficient and accurate means for the analysis of scattering problems that can be effectively treated neither by a high- frequency technique nor by a low-frequency method alone. The author抯 main contributions are as follows: 1. The generalized network formulation is employed to the analysis of scattering by complex objects for the first time. Based on this, several hybrid methods including LPO-MoM, IPO-BIM and IIPO-FDTD are developed. The high-frequency asymptotic method and the low-frequency numerical method are combined in such a manner that 1) it permits the two kinds of methods to be used separately and ii) it includes all significant interactions. General programs based on the hybrid techniques are developed and the coupling effects for a complex object on its scattering properties are investigated. These couplings include those between different parts of the large body itself, the large body and the small cavities and different parts of the small cavities. This work provides a basis for the optimization of the RCS of the complex targets. 2. The electromagnetic scattering by arbitrary cavities in a conducting plane is investigated by using the generalized network formulation and the connection scheme. Some examples including those containing complex terminations are presented, demonstrating the accuracy, efficiency, and capability of the technique. One significant advantage of this technique lays in the fact that the cavity can be split into sections using the connection scheme. The network representations of some common sections can be precomputed and stored for later use. So the scheme is well suited to serve as a computer-aided design tool for cavity scattering problems. 3. A new technique for extracting the admittance matrix of a crack or a cavity from its equivalent aperture magnetic currents is proposed. For a crack or a cavity with complex geometry, it seems feasible to use the FDTD method to compute its admittance matrix directly. However, this results in a slow-convergent and unstable solution due to 1/~~ the multiple reflections inside the cavity. In this dissertation, we first compute the equivalent aperture currents of the cavity under various excitations with the aperture opened and then the generalized network representation of the crack is obtained by using equation transformations. Thus the drawback of the former method is efficiently overcome. 4. A new technique that combines the generalized network formulation along with the boundary integral method and the connection algorithm is proposed to analyze the electromagnetic coupling through a complex three-dimensional slot in a conducting plane. This technique, in particular the usage of connection algorithm, can not only efficiently handle arbitrary slots regardless of their geometry and material properties but also greatly更多还原