共查询到19条相似文献,搜索用时 93 毫秒
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基于一种改进的Z变换-时域有限差分(Z-Finite-Difference Time-Domain,Z-FDTD)方法,即将双各向异性色散介质的频域本构方程先转化到Z域中,再利用Z变换的性质将其转换到时域,得到离散时域的FDTD迭代式,分析了双各向异性色散介质电磁波传播特性.由于Omega媒质是一种典型的双各向异性色散介质,以此为例编程计算了垂直入射在Omega介质板情形下产生的同极化和交叉极化电磁波的反射和透射情况,并通过算例和解析解对比验证了算法的正确性,最后对其电磁散射特性进行了分析. 相似文献
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基于各向异性介质中的时域有限差分(Finite-Difference Time-Domain,FDTD)方法及近似完全匹配层(Nearly Perfect Match Layer,NPML)原理,提出一种截断各向异性介质的修正的NPML吸收边界条件.通过对Maxwell旋度方程中的空间偏导数进行坐标拉伸并结合空间插值方法,推导出易于在FDTD方法中实现的吸收边界公式.计算了电偶极子辐射场的反射误差,验证了这种吸收边界截断二维各向异性介质的有效性.三维算例中数值模拟了时谐场的相位分布,以及不同网格NPML吸收层随时间变化的反射误差.数值结果表明NPML吸收边界能有效吸收各向异性介质中的电磁波. 相似文献
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由双负介质本够关系出发,将其相对磁导系数表示为以jω为自变量的Padé近似形式,利用时频转换关系jω→(δ)/(δ)t,引入离散时域移位算子代替时间微分算子,推导出FDTD计算双负介质的递推表达式.针对双负介质的电磁特性问题,用基于移位算子的FDTD方法研究了电磁波与各种双负介质的相互作用:会聚效应、相位补偿、高指定向性、减小金属后向散射,探讨双负介质在平板成像、谐振腔、天线、隐身方面的应用前景. 相似文献
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由异向介质的本构关系出发,给出了描述异向介质场与流的微分方程组,将其离散得到用于FDTD计算的一维递推表达式。最后,计算了异向介质板的反射系数。计算表明:由于模拟的异向介质是匹配介质,其吸波性能要明显的优于等离子体的,适当选取异向介质参数,可以使异向介质板有效地减小目标的雷达回波。 相似文献
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Maoyan Wang Debiao Ge Jun Xu Jian Wu 《Journal of Infrared, Millimeter and Terahertz Waves》2007,28(2):199-206
The shift operator method in finite-difference time-domain method for anisotropic double-negative (DNG) metamaterials is derived. The problem which incorporates both anisotropy and frequency dispersion at the same time is solved for the electromagnetic wave propagation in DNG media. By comparing with the mie series solution, the numerical verification of the method and program are confirmed by computing the back scattering of isotropic unmagnetized plasma sphere. The back scattering of conducting sphere coated with DNG media with different parameters is computed by using the shift operator method. One finds that the degree of DNG media’s match and isotropy plays important parts in the decrease of the back scattering of the conducting sphere. 相似文献
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Lijun Xu Naichang Yuan 《Microwave and Wireless Components Letters, IEEE》2005,15(12):892-894
The JE convolution finite-difference-time-domain (JEC-FDTD) method is extended to the anisotropic magnetized plasma which incorporates both anisotropy and frequency dispersion at the same time, enabling the transient solution of the electromagnetic wave propagation in anisotropic magnetized plasmas. Two-dimensional JEC-FDTD formulations for magnetized plasma are derived. The back scattering radar cross section (RCS) of a perfectly conducting cylinder coated by a layer of magnetized plasmas is calculated. 相似文献
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利用有限元-快速多极子算法(FEM-FMM)分析了三维复杂目标涂有不同吸波涂层的雷达散射截面(RCS).以圆锥体为例,详细计算分析了涂敷有耗各向同性、正单轴各向异性、负单轴各向异性和纳米吸波材料4种典型吸波材料对目标电磁散射特性的影响,并首次讨论了每种吸波材料随不同涂层厚度对RCS的影响,得到了最佳隐身效果的吸波材料和涂层厚度的组合.结果表明,涂敷最佳吸波材料目标的后向RCS比目标没有吸波涂层时可以降低16.6dB. 相似文献
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Minghua Han Naichang Yuan Chi Hu 《Journal of Infrared, Millimeter and Terahertz Waves》1998,19(7):1017-1025
The scattering phenomenology of the plate and the dihedral corner are investigated using the time-frequency processing of simulated data. The FDTD method is applied to carry out the simulated data. The simulated data are next analyzed in joint time-frequency plane by using the STFT (short time Fourier transformation) technology to provide further insight into the scattering phenomenology. In addition, the time-frequency distribution series, which improves the resolution of the STFT while overcoming the cross-term interference problem of the Wigner-Ville distribution, is applied to better identify back scattering returns that are difficult to resolve in the joint time-frequency plane. 相似文献
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Ionized-impurity scattering is an anisotropic process showing a high preference for small scattering angles. In a Monte Carlo simulation of a semiconductor device many small angle scattering events have to be processed, although the contribution of these events to carrier momentum relaxation is small. A new method is presented which reduces the amount of small-angle scattering very effectively. In the simulation an isotropic process is used which yields the same momentum relaxation time as the anisotropic process. A theoretical analysis based on the Boltzmann equation is carried out. Monte Carlo calculations are performed over a wide range of doping concentrations, lattice temperatures and electric fields. No systematic difference is found in the results from the anisotropic and the isotropic scattering models. For a given accuracy, the reduction of needed scattering events and free flights can be more than one order of magnitude at low and medium doping concentrations 相似文献
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为了研究厄米-高斯波束在各向异性媒质中的散射特性,采用了将各向异性圆柱的散射场和内部场用圆柱矢量波函数展开,应用电磁场边界条件和投影法,提出了一种分析单轴各向异性圆柱对厄米-高斯波束散射特性研究的精确半解析方法; 获得了厄米-高斯波束通过单轴各向异性圆柱的内场以及近场的归一化强度分布图; 对两种不同的厄米高斯波束入射情形做出了分析和对比。结果表明,两种波束在通过圆柱后都有入射波和反射波叠加而成的驻波现象,而TEM10(x′)模式厄米-高斯波束入射后近场强度增强,且有明显的折射现象。该研究结果对厄米-高斯波束的应用具有一定的参考价值。 相似文献
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通过对不同角度子孔径相干累加,多角度观测SAR可以提供高分辨率影像及多角度散射特征.然而,现有的累加成像方法存在非各向同性散射中心混叠问题.混叠将造成极化特征参数估计无法反映实际的目标物理特征,从而难以支撑分类及变化检测应用.为了去除不同散射中心间的相互干扰并利用不同类型的信息,该文提出了一种多角度极化SAR图像中的非各向同性散射估计与消除方法.该方法给出了基于两类目标假设的最大似然比检验统计量,分析了相干斑影响以及非各向同性散射消除机理,证明了恒虚警判决函数的单调性.通过机载P波段极化SAR进行了360观测试验,分析了非各向同性散射消除前后极化熵的变化,验证了算法的有效性并揭示出在目标特征提取方面的应用潜力. 相似文献