共查询到17条相似文献,搜索用时 171 毫秒
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应用二维时域有限差分方法分析层状介质中的目标散射时,在总场-散射场边界斜入射平面波源用常规方法难以引入,因为在总场-散射场边界处设置的入射波实际上包含了入射脉冲以及各分层界面的反射和多次反射.为解决这个问题,提出了斜入射平面波的混合引入方式,即对总场-散射场的四个边界面采取不同的处理方式.对于总场-散射场的纵向侧边界,用含有斜入射角度的修正一维时域有限差分方法,只要在自由空间位置加入入射脉冲就会自行产生由各分层界面形成的反射波,包括多次反射.同时,把纵向总场-散射场侧边界向下延伸,使得总场-散射场下边界位于完全匹配层内,这样透射波和散射波均为外向行波而被吸收.对于总场-散射场的上边界,由于完全位于自由空间中,边界上各点的入射波将是总场-散射场纵向边界角点处入射波的带有时间延迟的复制.数值模拟结果表明了本文所提出方法的正确性和有效性.
关键词:
时域有限差分
层状介质
斜入射平面波
修正一维麦克斯韦方程 相似文献
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基于等效原理和互易性定理研究了两个相邻目标的电磁散射问题,给出了这一复合电磁散射模型的二阶散射结果. 通常平面入射波的一阶散射结果容易求解,但由于耦合效应的复杂性,很难给出二阶散射结果的解析形式. 应用互易性定理给出了求解任意相邻导体/介质目标二阶电磁散射场的公式,并利用等效原理将求解散射场公式中的体积分简化为面积分的形式,从而降低了求解难度. 同时还推导了两个目标的二次散射场之间的关系. 最后应用给出的公式,求解了两相邻球形目标的复合散射场,对双站散射结果进行了讨论,同时与应用时域积分方程法求得的结果进行了比较.
关键词:
等效原理
互易性定理
电磁散射
相邻圆球 相似文献
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应用等效原理,通过引入口面上等效磁流将含腔导电目标电磁散射简化为腔内、外两个等效 问题. 腔内问题分段求解并应用级联法获得口面等效导纳矩阵;腔内外的耦合关系应用近似 边界元方法描述并由此获得口面等效磁流;最后,这一具有混合源的腔体内外一体化散射问 题则应用所提出的广义混合场积分方程方法建立电磁模型,并用多层快速多极子方法实现高 效数值求解. 实例计算结果与测试结果具有很好的一致性.
关键词:
含腔目标
电磁散射
混合场积分方程
数值分析 相似文献
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研究了半空间内复杂导体目标棱边散射的高频求解方法.分析半空间电磁波的传播规律和复杂目标棱边的电磁散射特性,将半空间并矢格林函数引入等效电磁流方法中,给出了基于等效电磁流法和物理绕射理论的半空间棱边散射场计算式,同时结合图形电磁学,对半空间复杂目标进行消隐处理,判断目标的棱边像素及获得棱边参数,与半空间目标的面元散射场相叠加,快速有效地计算了半空间复杂目标的雷达散射截面.数值结果证明了方法的有效性和准确性.
关键词:
半空间等效电磁流方法
半空间并矢格林函数
图形电磁学
雷达散射截面 相似文献
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为解决探测水下目标的电磁散射问题,提出大比例变换的总场-散射场源时域有限差分(FDTD)方法.该方法包含两次FDTD计算:第一次计算采用细网格得到激励源周围的近场值;第二次计算采用粗网格得到远距离的电磁场值.两次FDTD计算通过总场-散射场边界建立联系.实现细粗网格的大比例变换,例如变换比例N=10,大大节省了计算时间,降低了计算内存的消耗,提高了计算效率.通过算例验证该方法的正确性和有效性.最后,计算水下岩层中存在异常体时的电磁响应,指出当岩层中异常体电导率不同时,接收点处电磁场的幅值和相位均不相同. 相似文献
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本文将有限元/边界积分方法(FE/BIM)结合区域分解方法引入到粗糙海面及其上方目标 的电磁散射问题的研究中. 由于积分边界可以以任意形状设置在距模型表面任意远的距离处, 故本文采用共形人工边界结合区域分解建模方法截断模型的开放计算区域以减少求解未知量, 在截断区域内部采用有限元方法求解, 而计算区域的边界条件通过边界积分方程方法得到. 通过与矩量法获得的数值计算结果进行比较, 证明了该混合算法及模型处理方法的正确性, 进而研究了海面上方弹体目标的电磁散射特性, 并讨论了其双站散射系数随电磁波入射角度、目标高度、海面风速以及弹体尺寸的电磁散射特性变化情况. 本文结果可用于反演复杂背景下的目标信息及目标探测等领域.
关键词:
电磁散射
粗糙海面
目标
有限元/边界积分方法 相似文献
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《Waves in Random and Complex Media》2013,23(4):476-484
AbstractThe implementation of total-field/scattered-field (TF/SF) boundary for the unconditionally stable five-step locally one-dimensional finite-difference time-domain (LOD5-FDTD) method is proposed in this paper. There are 12 cases to be considered for each sub step, among them 8 cases for electric field grid points, based on the computational formulations and the particular location of grid points at the TF/SF face. Numerical results show that the plane wave can be successfully introduced into the TF region and maintains unconditional stabilization. Finally, the radar cross section (RCS) of a metal plate is computed, which further verifies the effectiveness of the proposed TF/SF connecting boundary. 相似文献
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A. N. Bogolubov G. V. Belokopytov Z. O. Dombrovskaya 《Moscow University Physics Bulletin》2013,68(5):344-350
A numerical algorithm is designed and implemented based on the joint application of the finite-difference time-domain (FDTD) method with absorbing boundary conditions (a combination of the perfectly matched layer (PML) and Mur first-order conditions) and the total-field/scattered-field technique (TF/SF). A complete formulation of the algorithm is given. The results of computing the spectral characteristics of the 2D photonic crystal with defects in the form of waveguides are presented. They demonstrate that it is possible to conduct calculations in a wide range of frequencies. 相似文献
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An efficient locally one-dimensional finite-difference time-domain method based on the conformal scheme 下载免费PDF全文
《中国物理 B》2015,(7)
An efficient conformal locally one-dimensional finite-difference time-domain(LOD-CFDTD) method is presented for solving two-dimensional(2D) electromagnetic(EM) scattering problems. The formulation for the 2D transverse-electric(TE) case is presented and its stability property and numerical dispersion relationship are theoretically investigated. It is shown that the introduction of irregular grids will not damage the numerical stability. Instead of the staircasing approximation, the conformal scheme is only employed to model the curve boundaries, whereas the standard Yee grids are used for the remaining regions. As the irregular grids account for a very small percentage of the total space grids, the conformal scheme has little effect on the numerical dispersion. Moreover, the proposed method, which requires fewer arithmetic operations than the alternating-direction-implicit(ADI) CFDTD method, leads to a further reduction of the CPU time. With the total-field/scattered-field(TF/SF) boundary and the perfectly matched layer(PML), the radar cross section(RCS) of two2 D structures is calculated. The numerical examples verify the accuracy and efficiency of the proposed method. 相似文献
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Perfect plane-wave source for a high-order symplectic finite-difference time-domain scheme 下载免费PDF全文
The method of splitting a plane-wave finite-difference time-domain (SP-FDTD) algorithm is presented for the initiation of plane-wave source in the total-field / scattered-field (TF/SF) formulation of high-order symplectic finite-difference time-domain (SFDTD) scheme for the first time. By splitting the fields on one-dimensional grid and using the nature of numerical plane-wave in finite-difference time-domain (FDTD), the identical dispersion relation can be obtained and proved between the one-dimensional and three-dimensional grids. An efficient plane-wave source is simulated on one-dimensional grid and a perfect match can be achieved for a plane-wave propagating at any angle forming an integer grid cell ratio. Numerical simulations show that the method is valid for SFDTD and the residual field in SF region is shrinked down to -300 dB. 相似文献
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Dikshitulu K. Kalluri Joo Hwa Lee Monzurul M. Ehsan 《International Journal of Infrared and Millimeter Waves》2003,24(3):349-365
This paper deals with the Finite Difference Time Domain (FDTD) simulation of interaction of an electromagnetic wave with a switched plasma slab. In formulating the simulation the well-known concepts of (a) total-field/scattered-field formulation (b) and PML lattice truncation are adapted to suit the simulation under consideration.FDTD is particularly well suited to handle the switched (time-varying) medium (including sudden switching) since the time varying parameters of the medium can be easily interpreted in the algorithm. The technique is applied to the difficult problem of interaction of an electromagnetic pulse source wave of frequency 0 and a gaussian envelope with a newly created plasma slab of time-varying and space varying electron density profile. The creation of a pulse of Wiggler magnetic field in the slab is illustrated. 相似文献
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利用MOM研究了不同土壤类型的一维有耗介质粗糙地面与其下方二维埋藏目标的复合电磁散射问题,在数值计算中,引入了锥形入射波以减少粗糙面模拟中由于人为截断所引起的计算误差.当给定入射波频率、土壤成分及土壤温度和土壤湿度后,可以根据相关模型计算出土壤的相对介电常数.数值结果以二维无限长导体圆柱为例,利用 Monte Carlo方法统计计算了双站复合散射截面随土壤类型、土壤湿度、入射波频率及均方根高度等的变化情况,并做了详细分析及讨论.该研究结果对于探地雷达在民用、军事、工业等多领域的应用具有一定的理论指导价值.
关键词:
粗糙地面
土壤类型
相对介电常数
四成分模型 相似文献