星载微波ERS-1和多通道SSM/I观测冰雪的相关性和多层随机介质的数值模拟

该文研究了星载微波ERS－1散射计和多通道SSM／I辐射计在格陵兰岛、西伯利亚和阿尔卑斯山等地观测到的后向散射和热辐射数据，论证了同一地区同一时间段内ERS主动散射计和SSM／I被动辐射计观测数据的相关性。用冰雪覆盖区域的主被动遥感数据的比较，阐述了主被动联合多通道分析方法有利于监视和分析复杂地表在时间和空间尺度上的变化。该文用多层强起伏随机介质的后向散射模拟ERS数据，用多层密集散射粒子介质的辐射传输模拟SSM／I数据。讨论了后向散射与热辐射数值模拟结果的相关性，以及与星载微波遥感器实际观测结果的比较。     

星载微波ERS—1和多通道SSM／I观测冰雪的相关性和多层随机介质的 …

该文研究了星载微波ＥＲＳ－１散射计和多通道ＳＳＭ／Ｉ辐射计在格陵兰岛、西伯利亚和阿尔卑斯山等地观测到的后向散射和热辐射数据，论证了同一地区同一时间内ＥＲＳ主动散射计和ＳＳＭ／Ｉ波动辐射计观测数据的相关性。用冰雪覆盖区域的主被动遥感数据的比较，阐述了主被动联合多通道分析方法有利于监视和分析复杂地表在时间和空间尺度上的变化。该文用多层强起伏随机介质的后向散射模拟ＥＲＳ数据，用多层密集散射粒子介质的辐射     

三维非均匀散射层与其中异常目标的辐射传输

讨论了三维非均匀散射层与其中有异常目标的矢量辐射传输高阶散射与辐射的求解与数值模拟.将三维非均匀散射介质在垂直方位z轴方向划分成许多薄层,再在水平(x,y)方位上划分成方格,用分割形成的各薄盒的零阶热辐射和一阶Mueller矩阵解,推导多阶辐射传输的迭代方法,获得整个散射介质三维VRT方程的高阶散射与辐射解.模拟了微波频段在各空间分辨率的辐射计观测下非均匀植被层和地面上有异常目标的极化辐射亮度温度的观测图像.     

双基地前向散射雷达杂波分析与模拟方法北大核心CSCD

雷达杂波的统计特性研究与仿真模拟对雷达系统的设计、仿真、开发有重要意义。文中通过对前向散射雷达地表植被杂波实测数据的处理,观察到前向散射雷达杂波的幅度分布特性可根据风速和动态范围的不同分别采用K分布和对数正态分布拟合;同时杂波数据的谱分析结果表明可以采用全极点模型对前向散射雷达杂波建模。基于对杂波统计特性的分析,文中给出了一种SIRP法和ZMNL法相结合的前向散射雷达杂波模拟方法,模拟得到的杂波与实测杂波数据在统计特性上相一致,证实了模拟方法的有效性。     

植被电磁散射中后向散射增强的研究

本文应用直接求散射体散射场的方法，运用Ｍｏｎｔｅ－Ｃａｒｌｏ模拟技术研究了植被电磁散射中由植被层的体散射和地面层的面散射相互作用引起的后向散射增强。计算得到了不同高度的植被层的散射特性，给出了人们感兴趣的后向增强角宽度的量级。结果表明，在植被层较矮即地面影响较强时后向散射增强较大，由体－面相互作用散射引起的后向散射增强的角宽度较宽，约在１０￣４０度之间。     

自然地表红外图像的模拟

自然界的地表是非常复杂的,影响其温度分布和红外辐射特性的因素很多,如地表的起伏、土壤类型、植被类型、土壤湿度和气象条件等.要精确计算自然地表的温度和红外辐射特性,生成红外图像,必须建立考虑各种影响因素的三维传热传质模型.这种方法要花费大量的计算时间,是不实用的.文中利用一维模型的计算结果并结合随机模拟方法,针对具体自然地表(不同植被、裸露地表等)的实际红外辐射强度的相关长度、均方根误差以及相邻像素点的空间距离,模拟生成了自然地表的红外图像.探测器的视场和视角对观察到的图像影响是很大的,对同一地面区域,使用不同视场的探测器观察,得到的图像不同,即使使用同一探测器,如果用不同的视角观察同一区域,得到的图像也是不同的.因此文中根据不同的红外探测器视场以及同一探测器的不同的视角,将该图像转换成了红外探测器视场内的图像,分析了对应不同视场和视角的自然地表红外图像的特征.     

植被散射的蒙特卡罗模拟及其在低掠角散射中应用

本文提出利用蒙特卡罗算法研究植被散射及其低掠角散射特性.根据双层植被的散射模型,考虑到植被层内各散射体场的相干和多径效应,利用蒙特卡罗算法模拟随机分布和簇规则分布植被的低掠角散射系数,适当解释植被散射的后向增强和掠射特性.     

散射辐射组合系统对造波水面的观测研究

介绍了新研制的Ｘ波段散射计组合系统。利用这一组系统进行了同时同地相继观测，得到ｖｗ，ｈｈ，ｈｖ多极化的后向散射系数σ＾０ＰＱ（ｐ，ｑ－ｖ，ｈ），ｖ和ｈ极化的辐射亮温度ＴＢＰ（ｐ＝ｖ，ｈ）。为模拟海面风场驱动起伏海面，利用室内人工造波池，在机械驱动下产生给定波谱的随机性或周期性起伏水面。用该散射计地组合系统观测多角度与多种起伏高度时的σ＾０ｐｑ－ＴＢｐ。并用双尺度随机粗糙面散射辐射理论模，烽值地模拟     

GPSAR浅地表目标电磁特性分析

利用机载或车载地表穿透合成孔径雷达可以实现远距离大区域地表目标快速探测.为了降低虚警,需要根据目标的电磁特征设计检测器来区分目标和杂波.提出运用时域有限差分方法结合傅里叶变换进行地表穿透合成孔径雷达浅地表目标电磁特征计算的方法.首先根据复杂背景媒质的散射特性获取目标的激励场,然后分析复杂背景下目标的电磁特性.利用该方法模拟了平坦地面下的金属地雷的散射特性,并与矩量法的计算结果进行了比较,结果基本一致.我们模拟了高斯起伏地面下的M6A1金属地雷,理论数值计算结果与实测数据结果基本吻合.模拟结果显示浅地表金属地雷图像具有双峰特征,它将有效地提高地雷检测性能.     

地表后向散射测量实验及其等效介电常数和粗糙度参数的反演

由于地物类型繁多且分布不均匀,地表粗糙度的测量存在不准确性,且地表分层、体散射机理较难准确界定.针对上述问题,将裸土和水泥路面在入射角小于66°的散射模型等效为面散射模型,联合中国电波传播研究所X波段裸土和Ku波段水泥路面的后向散射实测数据,采用遗传算法同时反演了地表的等效介电常数和等效粗糙度参数,并采用剩余实测数据对反演结果进行了验证,吻合良好.该等效面散射模型在保证裸土和水泥路面后向散射预测精度的同时,降低了模型复杂度,仅需反演面散射模型的3个等效参数(等效均方根高度、等效相关长度和等效介电常数)即可实现对复杂地表后向散射特性的快速、准确预测,具有重要的工程应用价值.     

尾流气泡激光散射的测量

采用收发分置的光学结构实现了尾流气泡对532 nm激光在散射角5°～175°内的散射测量,同时测量了水的激光散射。散射角度的改变是通过发射系统不动而转动接收系统来实现的。解决了散射信号大动态范围的压缩问题,讨论了接收视场内散射体积随散射角的变化。分析了气泡散射的信号特征,并提出了气泡散射信号的功率谱密度处理法。将实验结果与米氏理论结果进行了对比,发现尾流气泡的激光散射强度及其随散射角的变化趋势与米氏理论结果吻合得很好,与水的散射相差近一个数量级。研究结果表明利用激光可以将气泡和水的散射区别开,即利用激光探测尾流气泡的存在具有可行性。     

Wave propagation and scattering in random media and rough surfaces

The author presents a comprehensive review highlighting historical as well as new developments in the area of random media. Both discrete and continuous media are considered as well as rough surfaces. The author discusses wave propagation in turbulence and in a random continuum where the refractive index is a random function of space and time. Examples are optical propagation in the atmosphere, microwaves in the troposphere, ionosphere, planetary atmosphere, and solar wind, and acoustic scattering in ocean turbulence. The author describes multiple scattering by random distributions of discrete scatterers. Examples are optical and microwave scattering by rain, fog, smog, snow, ice particles, and vegetation, optical and ultrasound scattering by tissues and blood, optical and acoustic scattering in the ocean, and scattering in composite materials. Scattering by rough surfaces and interfaces is discussed. Examples are acoustic scattering by ocean surfaces, microwave and optical scattering by vegetation, terrain, and snow cover, and ultrasound scattering by rough interfaces in biological media     

散射对量子阱隧穿电流的影响

本文从单带双谷模型出发研究了电子在量子阱内遭到散射时电子状态及隧穿几率的变化。弹性散射使用δ散射势来计算,非弹性散射则用虚散射势来描述。前者使隧穿电流峰向高电压端移动,后者减弱了电流峰的谐振强度。分别讨论了位于势阱和势垒层中的散射中心的不同散射作用。隧穿电流的变化趋势同中子辐照实验数据相吻合。     

Scattering of a dipole field by a moving plasma column

The problem of scattering of a dipole field by a plasma column moving uniformly in the axial direction is treated. In order to know the effect of the motion of the plasma on the scattering pattern, first the scattering properties of the dipole field by a stationary plasma with the aid of numerical examples are discussed. In this case two kinds of scattering patterns are illustrated: one in a cross section of the column and the other in the longitudinal section of the column. Then the scattering pattern of the dipole field by the moving plasma is investigated. From the numerical examples for the stationary plasma it is found that the scattering patterns are well-classified into three typical patterns by investigating the ratio of the backward scattering to the forward scattering with respect to the parameters which govern the scattering properties. In the case of moving plasma, it is shown that the scattering pattern in the longitudinal section will have a characteristic directional pattern, which does not appear in the case of stationary plasma, at a frequency lower than the plasma frequency.     

Unsupervised classification of scattering behavior using radarpolarimetry data

The use of an imaging radar polarimeter data for unsupervised classification of scattering behavior is described by comparing the polarization properties of each pixel in an image to that of simple classes of scattering such as even number of reflections, odd number of reflections, and diffuse scattering. For example, when this algorithm is applied to data acquired over the San Francisco Bay area in California, it classifies scattering by the ocean as being similar to that predicted by the class of odd number of reflections, scattering by the urban area as being similar to that predicted by the class of even number of reflections, and scattering by the Golden Gate Park as being similar to that predicted by the diffuse scattering class. It also classifies the scattering by a lighthouse in the ocean and boats on the ocean surface as being similar to that predicted by the even number of reflections class, making it easy to identify these objects against the background of the surrounding ocean     

Effects of a Rough Boundary Surface on Polarization of the Scattered Field from an Inhomogeneous Medium

The effect of surface roughness on the polarization of the scattered field is studied by combining the standard Kirchhoff method for rough surface scattering with the radiative transfer method for volume scattering using the Rayleigh phase function. Corresponding cases of pure surface scattering from a homogeneous layer and volume scattering from a plane inhomogeneous layer are also computed to serve as points of reference. In each case the degree of polarization DP, polarization ratio PR, locations on the Poincaré sphere of copolarization nulls CN, and cross-polarization nulls XN are computed. It is found that for pure surface scattering PR between 0-20° incidence angles is quite sensitive to change in surface roughness. However, when both surface and volume scattering are present, CN by colatitude or DP between 0-15° incidence angles and CN or XN by longitude at large incidence angles (>60°) are better indicators of change in surface roughness. Since XN changes insignificantly in pure surface scattering, it appears that a significant change in it can serve as an indicator for the presence of volume scattering. Also, in pure surface or volume scattering, the variations of DP and CN by colatitude are monotone with the incidence angle, while in the combined surface and volume scattering DP has a minimum and CN by colatitude has a maximum. This character offers the possibility of separating combined surface and volume scattering from pure surface or volume scattering.     

The effect of topography on radar scattering from vegetated areas

The ways in which radar scattering from vegetated areas is affected by the topography of the surface underneath the vegetation are discussed. It is shown, using a discrete scatterer model, that the dominant scattering mechanism may change drastically when the ground surface is tilted relative to the horizontal. For a horizontal ground surface, for example, the total scattering may be dominated by scattering off the tree trunks, followed by a reflection off the ground surface. For a relatively small tilt in the ground surface, the ground-trunk interaction term may be replaced by scattering from the branches alone as the dominant scattering mechanism. The effect of the topography is more pronounced for scattering by longer wavelengths, and the implications on algorithms designed to infer forest woody biomass and soil and vegetation moisture using polarimetric SAR data are discussed. The effect of the topography on the scattering behavior from forested areas is illustrated with images acquired by the NASA/JPL three-frequency polarimetric SAR over the Black Forest in Germany     

散射效应对FSO-OFDM系统的影响研究与仿真

为了研究了大气散射效应对光信号的影响,以雨粒子为例,从其物理特性出发,应用Mie散射理论和Joss雨滴谱分布,计算了雨粒子对光波传输的衰减,在此基础上分析了光散射效应对自由空间光通信-正交频分复用系统性能的影响。结果表明,在散射信道中,自由空间光通信-正交频分复用系统的性能主要取决于散射造成的光强度起伏方差,其次为散射造成的光强度衰减系数。     

相控阵天线系统散射分析

该文采用S参数分析了有源相控阵天线单元馈电系统模型的接收机负载反射系数.将该反射系数代入阵列天线散射场基础理论公式分析了有源相控阵天线的散射场,将有源相控阵天线的天线模式项散射场分为天线模式反射散射场和天线模式相控散射场进行分析.最后通过一维线阵验证了理论分析结果.该分析方法和分析结果为相控阵天线RCS计算和控制提供了理论指导.     

Multiple scattering and depolarization by a randomly rough Kirchhoff surface

A matrix approach has been developed to compute bistatic scattering coefficients which include shadowing and multiple scattering effects for a randomly rough Kirchhoff surface. The method permits the computation of these coefficients in terms of the existing single-scatter bistatic scattering coefficients. Thus the effects of multiple scattering are readily recognized from the expressions obtained. The bistatic scattering coefficients are shown to satisfy energy conservation to at least two significant figures. It is observed that while polarized backscattering is dominated by the single-scattering process, the depolarized backscattering is due to multiple scattering. Unlike depolarization by slightly rough surfaces or volume scattering, the angular behavior of the depolarized backscattering is similar to that of the polarized backscattering. The transitional behavior of the relative dominance between single and multiple scattering for the polarized and depolarized scattering coefficient as a function of the azimuth angle is illustrated.