共查询到18条相似文献,搜索用时 156 毫秒
1.
对具有涂覆层目标的太赫兹波段粗糙表面的散射特性进行了研究. 考虑到表面粗糙度的影响, 可先对反射系数进行修正, 再利用反射系数对等效电磁流进行修正, 得到粗糙涂覆表面的等效电磁流, 然后在物理光学方程的基础上得到粗糙表面涂覆目标的雷达散射截面; 最后进行图形电磁学可视化计算, 并采用Visual C++对模型进行OpenGL显示, 提取像素面元的有效信息对所得理论进行了仿真分析, 研究了不同入射角度、不同频率、不同介质、不同粗糙度和不同涂层厚度下的太赫兹波电磁散射特性, 得到了一些有参考价值的结论. 相似文献
2.
太赫兹频段下导体表面的细微结构、粗糙度等细节将对目标电磁散射行为产生影响。为衡量这一影响程度,以圆柱导体为例研究了太赫兹频段下目标表面不同结构特征的电磁散射现象及其在图像域的表现规律。利用高频电磁计算方法获得了表面分别为理想光滑、带刻痕和周期粗糙的三种圆柱多姿态角、多频点单站散射场;基于转台成像算法重建了小转角下目标的二维图像。从仿真结果可以看出:m量级的细节特征在太赫兹雷达图像上有着显著的表现,表明太赫兹雷达能够获取更加丰富和精细的目标信息,从而为目标探测识别提供新的特征和技术手段。 相似文献
3.
提出一种解析的随机泛函方法(SFA),计算导体Gauss粗糙面上三维导体目标的复合电磁散射.推导粗糙面的随机Green函数,用一种新的四路径模型描述面体复合散射机理,用SFA求解双站差场雷达散射截面.以导体球目标为算例,与其他数值计算方法比较后验证了SFA的有效性与准确性,同时讨论了粗糙度、体目标尺寸以及距离粗糙面高度等参量变化对结果的影响,给出复杂形状体目标的双站差场雷达散射截面的空间角分布.
关键词:
随机泛函方法
粗糙面随机Green函数
差场雷达散射截面
面体复合散射 相似文献
4.
研究了太赫兹波段纳米颗粒的表面增强拉曼散射,证明在太赫兹波段同样存在拉曼增强现象。通过研究表面增强拉曼散射的电磁增强原理,提出利用时域有限差分法仿真模拟纳米颗粒在太赫兹波照射下的表面增强拉曼散射,分析了太赫兹波的增强效果。仿真实验表明,时域有限差分法可以有效精确仿真太赫兹波段纳米颗粒的散射效果,结果使表面增强拉曼散射从可见光和红外波段扩展到太赫兹波段,为太赫兹波与表面增强拉曼散射的结合应用提供了依据。 相似文献
5.
提出了快速计算二维导体粗糙面与面上金属目标复合散射的广义稀疏矩阵平面迭代及规范网格法(G-SMFSIA/CAG).推导了二维导体粗糙面与面上目标相互作用的耦合积分方程,用稀疏矩阵平面迭代及规范网格法(SMFSIA/CAG)求解粗糙面部分的表面积分方程,而用基于RWG基函数的矩量法(MOM)计算目标部分的表面积分方程,并通过更新方程的激励项迭代求解目标与粗糙面的相互耦合作用.结合Monte-Carlo方法产生具有PM(Pierson-Moskowitz)海浪谱的随机海洋粗糙面,数值分析了海面上不同形状导体目
关键词:
复合散射
广义稀疏矩阵平面迭代及规范网格法
随机海洋粗糙面
双站散射系数 相似文献
6.
7.
8.
设计了一个可调谐的太赫兹超表面,由在随机反射超表面基底中嵌入可偏置的双层石墨烯构成,可以实现对太赫兹波散射特性的动态调控.全波仿真试验结果证实了所预期的超表面散射可调性能.通过增大偏置电压提升石墨烯的费米能级,使得该超表面的太赫兹波散射样式从漫反射逐渐向镜面反射过渡,从而实现散射特性的连续调控,且该超表面具有对电磁波极化角度不敏感的特点.这些特性使得该超表面能很好地融合到变化的环境中,在太赫兹隐身方面具有潜在的应用价值. 相似文献
9.
首先建立大尺度分层介质粗糙面散射的物理模型, 基于Stratton-Chu积分方程和Kirchhoff近似导出了粗糙面散射场的计算公式. 采用高斯随机粗糙面来模拟实际的分层介质粗糙面, 通过数值计算得到了正下视单站雷达接收到的后向散射回波. 理论推导了散射场强度与表面粗糙度之间的定量关系, 并从数值仿真的角度分析了表面和次表面的粗糙度对散射回波的影响, 给出了散射场随粗糙度变化的曲线. 最后考察了分层介质的电特性参数(介电常数和电导率)对分层粗糙面散射场的影响, 并对计算结果做出了分析. 相似文献
10.
11.
很多物质在太赫兹波段内的光谱参数具有指纹特征,这是太赫兹技术在安检等众多领域有所应用的基础.但是,目前常用的太赫兹时域光谱(THz-TDS)技术提取物质光学参数的Duvillaret算法,要求样品上下表面平行且充分光滑.然而在很多有潜力的实际应用场合中,尤其是对于固体样品,表面粗糙度不可避免,并且不能使用模具压片等实验... 相似文献
12.
13.
Hybrid method for investigation of electromagnetic scattering from conducting target above the randomly rough surface 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A current based hybrid method (HM) is proposed which combines the method
of moment (MOM) with the Kirchhoff approximation (KA) for the analysis
of scattering interaction between a two-dimensional (2D) infinitely
long conducting target with arbitrary cross section and a
one-dimensional (1D) Gaussian rough surface. The electromagnetic
scattering region in the HM is split into KA region and MOM region.
The electric field integral equation (EFIE) in MOM region (target)
is derived, the computational time of the HM depends mainly on the
number of unknowns of the target. The bistatic scattering
coefficient for the infinitely long cylinder above the rough surface
with Gaussian roughness spectrum is calculated, and the numerical
results are compared and verified with those obtained by the
conventional MOM, which shows the high efficiency of the HM.
Finally, the influence of the size, location of the target, the rms
height and correlation length of the rough surface on the bistatic
scattering coefficient with different polarizations is discussed in
detail. 相似文献
14.
Zhihui Wang 《Optik》2014
In this paper, a theoretical study of the influence of surface roughness on conductor is proposed at terahertz frequencies. By using the analytic small perturbation method, the effects of a random rough surface on the absorption by a metallic surface at terahertz frequencies are analyzed. And the effect of rough surface on reflectivity and power spectral density are also demonstrated. The numerical results are very useful for the development of terahertz devices and terahertz material. 相似文献
15.
Bogdan F. Apostol 《Central European Journal of Physics》2013,11(8):1036-1044
The classical theory of scattering of longitudinal waves (sound) by small inhomogeneities (scatterers) in an ideal fluid is generalized to a distribution of scatterers and such as to include the effect of the inhomogeneities on the elastic properties of the fluid. The results are obtained by a new method of solving the wave equation with spatial restrictions (caused by the presence of the scatterers), which can also be applied to other types of inhomogeneities (like surface roughness, for instance). A coherent forward scattering is identified for a uniform distribution of scatterers (practically equivalent with a mean-field approach), which is due to the fact that our treatment does not include multiple scattering. The reflected wave is obtained for a half-space (semi-infinite fluid) of uniformly distributed scatterers, as well as the field diffracted by a perfect lattice of scatterers. The same method is applied to a (inhomogeneous) rough surface of a semi-infinite ideal fluid. A perturbation-theoretical scheme is devised, with the roughness function as a perturbation parameter, for computing the waves scattered by the surface roughness. The waves scattered by the rough surface are both waves localized (and propagating only) on the surface (two-dimensional waves) and waves reflected back in the fluid. They exhibit directional effects, slowness, attenuation or resonance phenomena, depending on the spatial characteristics of the roughness function. The reflection coefficients and the energy carried on by these waves are calculated both for fixed and free surfaces. In some cases, the surface roughness may generate waves confined to the surface (damped, rough-surface waves). 相似文献
16.
V. L. Malevich G. V. Sinitsyn G. B. Sochilin N. N. Rosanov 《Optics and Spectroscopy》2018,124(6):889-894
The scattering of broadband terahertz pulses on a rough surface of a semi-infinite medium has been analyzed by a modified Monte Carlo method, which takes into account the radiation phase. The results have been compared with a simplified analytic expression that allows generalization in the case of layered media and the presence of volumetric scattering. These results allow a simple way to exclude or reduce the scattering influence on the recovery of the media characteristics in the method of pulse terahertz spectroscopy to be suggested. 相似文献
17.
采用分子动力学模拟方法研究了气体分子Ar在光滑和粗糙Pt表面上的散射规律.提出了一种速度抽样方法,计算了不同温度条件下气体分子对光滑和粗糙表面的切向动量适应系数和吸附概率.结果显示:光滑表面条件下,气体分子的切向动量系数和吸附概率都随着温度的升高而降低;粗糙度对气体分子切向动量与表面的适应具有极大的促进作用,当粗糙度足够大时,切向动量适应系数的大小趋近于1.0,对温度的敏感性也逐渐降低.采用粒子束方法对气体分子在光滑和粗糙表面上的散射规律进行了定量分析.总结了散射过程中气体分子的典型轨迹和动量变化规律,将气体分子在光滑表面的散射分为两种类型:单次碰撞后散射和多次碰撞后散射.单次碰撞后散射的气体分子平均切向动量有所减小,而经过多次碰撞后散射的气体分子则倾向于保持原有的平均切向动量.对于粗糙表面,粗糙度的存在使气体分子与表面间的动量和能量适应更加充分,导致气体分子在较粗糙表面上散射后的平均切向动量大幅减小并接近于0,且气体分子在表面上经历的碰撞次数越多,其散射后的能量损失越严重. 相似文献
18.
运用微扰法研究了平面波入射分层介质粗糙面的电磁散射,推出了不同极化状态下的双站散射系数公式.采用二维fBm分形粗糙面来模拟实际的分层介质粗糙面,结合二维fBm分形粗糙面的功率谱导出了平面波入射二维fBm分形分层介质粗糙面的散射系数计算公式.通过数值计算得到了HH极化下双站散射系数随散射角的变化曲线,讨论了分维、底层介质介电常数、中间介质介电常数和厚度及入射波频率对双站散射系数的影响,得到了二维fBm分形分层介质粗糙面散射系数的分维特征、基本特征、分区特征和随频率变化的特征.
关键词:
电磁散射
二维fBm分形粗糙面
分层介质
微扰法 相似文献