【作者】 平兰兰；

【导师】 何小祥；

【作者基本信息】 南京航空航天大学 ， 电子科学与技术， 2010， 硕士

【摘要】 本文将总场—散射场划分技术中的体激励法(VETSFD)应用到时域有限元方法(TDFEM)中,分析了二维目标的电磁散射特性。首先介绍了求解边值问题的TDFEM基本原理及其求解电磁问题的基本步骤。在电磁散射分析中,采用连接边界(CB)将整个计算区域划分为总场区和散射场区,并在总场区强加入射平面波,既可以减小入射波产生的误差,又可以同时得到总场和散射场的场值。采用Mur吸收边界条件(ABC)对整个计算区域进行截断。为了验证算法的有效性,首先对无目标时的计算区域进行分析,发现入射波泄露到散射场区的值只有-110dB,相对于惠更斯面元激励法-20dB的入射波泄露,VETSFD-TDFEM计算精度大为提高。进一步,利用等效原理,由输出边界(OB)上的电磁场各切向场分量外推得到远区场,从而求出了二维(2-D)目标的雷达散射截面(RCS)。本文在TE波激励下计算了金属目标、介质目标、介质涂覆目标和机翼模型等典型目标的双站雷达散射截面。并将所得数据结果与时域有限差分方法(FDTD)计算结果以及参考文献数据进行对比,数据曲线吻合很好,从而验证了该算法的有效性和精确性。在此基础上,分析了VETSFD-TDFEM算法的计算时间、内存消耗、算法稳定性以及计算精度等要素,为将时域有限元方法从二维模拟推广到三维分析奠定了基础。最后,应用VETSFD-TDFEM对一种特殊光子晶体—蓝蝴蝶翅膀有限周期性微结构的电磁散射特性进行了研究,主要对Morpho蝴蝶微结构所具有的光学散射带阻和角偏特性进行了深入地探讨。更多还原

【Abstract】 In this thesis, The Volumetric Excitation (VE) method in Total- and Scattered-Field Decomposition (VETSFD) techniques is applied to Time Domain Finite Element Method (TDFEM) for electromagnetic scattering analysis of some representative 2-D objects. Firstly, TDFEM is introduced, and the theory and the steps of electromagnetism analysis are given. Secondly, to mitigate dispersion error on the incident wave, while preserving a total-field region local to the objects of interest, the whole computational area is split into Total Field (TF) and Scattered Field (SF) with connecting boundary (CB), and the incident wave is impressed on the TF. The Mur absorbing boundary condition (ABC) is used to truncate the computational area. To validate the accuracy of the VETSFD-TDFEM, the leakage in the computational area in absence of objects is investigated firstly. The maximum leakage of backward scattering into the scattered-field region is about -110 dB, which is much more accurate than the traditional Huygens’surface excitation method (the associated wave leakage is as high as -20dB). Then the far filed can be obtained from the electromagnetic field distribution on output boundary (OB) lies between CB and AB according to the equivalent theory. Radar Cross Section (RCS) of some representative 2-D objects can be obtained.And then, the scattering of transverse electric (TE) field mode is investigated in this paper, The bistatic RCS of some metal objects, medium objects, dielectric coated metal and metal airfoil are computed and presented. The numerical results generated with VETSFD-TDFEM are compared with the results simulated with FDTD or reference results, which demonstrates that VETSFD-TDFEM is an effective method for electromagnetic scattering analysis of complex objects. Besides, computational time, memory consumption, stability of iteration and computational precision are also investigated in this paper.Finally, the electromagnetic scattering of a special photonic crystal-the finite periodicity micro-structure of Morpho butterfly’s wing is analyzed with VETSFD-TDFEM. The bandstop and angle-dependent characteristics of the micro-structure are investigated in detail in this paper.更多还原