【作者】 杨凌霞；

【导师】 葛德彪；

【作者基本信息】 西安电子科技大学 ， 无线电物理， 2003， 硕士

【摘要】 电大尺寸复杂目标 RCS 的分析预估长期以来一直是电磁场理论研究的一个重要课题 各种频域高频方法已经成为计算电大尺寸目标 RCS 有效途径 随着时域电磁学的发展 近十年来提出了许多时域高频技术 例如时域物理光学方法 时域几何绕射理论 时域一致性几何绕射理论 时域等效边缘电磁流方法等 本文着重研究时域等效边缘电磁流方法及其在电磁散射中的应用 本文首先概述了频域等效边缘电流(EEC)方法的基本概念及其发展概况,分析了等效边缘电磁流方法在计算电大尺寸复杂目标 RCS 的基本思路 在此基础上通过对频域等效边缘电磁流表达式进行傅立叶逆变换 得到了时域等效边缘电磁流 (TD-EEC) 方法 它通过对入射脉冲和绕射系数沿着目标边缘路径积分得到远区散射场 其结果在焦散区保持有效 并且时域绕射系数和频域绕射系数表达式相同 本文将其应用于矩形板 梯形板 圆盘和方柱的瞬态散射场及 RCS 的分析所得结果与 FDTD 结果比较 在一次绕射起主要作用时两者符合较好 另外 由TD-EEC 方法求得的时域绕射场经傅立叶变换后 一次计算可得到宽频带的 RCS弥补了频域 EEC 方法只能计算单频 RCS 的缺陷 此外 根据 TD-EEC 方法中时域绕射系数和频域绕射系数的表达式相同的特点 我们将赵维江等提出的 EEC 绕射系数边缘分量应用到 TD-EEC 方法中 得到了时域等效边缘电磁流方法中绕射系数边缘分量的改进形式 与文献中采用Michaeli 绕射系数边缘分量所得结果相比较 表明新的绕射系数边缘分量有更高的精度更多还原

【Abstract】 Analysis and prediction of RCS by large complex objects is of importance inelectromagnetic scattering and related areas. Several kinds of high-frequency techniqueshave been proposed to deal with this problem. As the development of time-domainelectromagnetics, some time-domain high-frequency techniques such as time-domainPhysical Optics (TD-PO), time-domain geometric theory of diffraction (TD-GTD),time-domain uniform theory of diffraction (TD-UTD) and time-domain equivalent edgecurrent method (TD-EEC) were developed in the past ten years. In this paper, mainefforts are put on time-domain equivalent edge current method and its application toelectromagnetic scattering. Starting from basic concepts and development of the frequency domain equivalentedge current method, we analyze the process of evaluation of RCS for large complexobjects by EEC method. Based on the Fourier inversion transformation of frequencydomain equivalent edge current expression, time-domain equivalent edge currentmethod is developed. The time-domain diffraction field is expressed in terms of acontour integral along diffracting edges for arbitrary incident field with proper delaysand diffracted coefficient similar to the expression in the frequency domain, yieldingfinite results at the caustics of diffracted rays. The results for a perfectly conductingrectangular and trapezoidal flat plate, a disk and a cube computed by TD-EEC arecompared with FDTD results. The results are in good agreement while the multiplediffractions between edges are not included. The multiple diffractions evaluated byTD-EEC will be the future work. In addition, wide band RCS can be obtained throughthe Fourier transformation of time-domain scattering field. In TD-EEC method, diffraction coefficient is similar to the expression in thefrequency domain, which may be decomposed into two parts: physical optics (PO)component and fringe component. Michaeli’s expression for fringe component isapplied to TD-EEC in Reference [14]. By applying the fringe component of diffractioncoefficient in [42], we obtain an improved expression for fringe component ofdiffraction coefficient implementing to TD-EEC method. An example of diffraction byperfectly conducting plate is used to illustrate our scheme. Comparing with the FDTDresults we observe that the improved expression for fringe component is more accuratethan that of Michaeli’s formulation.更多还原