多极化SAR图像的降斑研究

对于多极化SAR图像,可以利用其同极化和交叉极化图像的相关性来进行降斑处理.本文对常用的几种基于多极化SAR图像的降斑方法进行了分析,重点研究了最优加权法(the optimal weighting algorithm),在其基础上改进提出了分块加权法,取得了明显的降斑效果,并较大地减少了运算量.最后利用实测的SAR数据进行了验证.     

Multipolarization SAR Data for Surface Feature Delineation and Forest Vegetation Characterization

This paper presents the utility of multipolarization Synthetic Aperture Radar (SAR) data for surface feature delineation and forest vegetation characterization. Three channels of ratioed data (VV/HH, VH/HH, and VH/VV) are generated from the HH, VV, and VH polarization data (V = vertical, H = horizontal). The ratioed data are linearly stretched to yield a digital number within a range of 0 to 255. The techniques for reducing SAR speckle noise and for measuring the degree of separation are discussed. For surface feature delineation, the results indicate that cross polarization as well as cross polarization ratioed data better delineate those surface features that are difficult to separate by like polarization data. The results suggest using a median value filtering technique to reduce within-plot data fluctuation to increase the separability measure. For forest vegetation characterization, the results indicate that multipolarization SAR data may be used to estimate forest properties such as total-tree biomass, basal area, and tree height.     

高分辨率多极化SAR图像目标分类误差分析

讨论了多极化SAR系统的极化误差及其对多极化SAR图像极化匹配目标分类性能的影响,并给出了计算结果。分析表明,多极化SAR系统的极化通道幅度不平衡误差对目标极化匹配结果的影响最大,交叉极化干扰项对此也有较大的影响。     

大斜视SAR的多普勒参数估计

提出了一种适于大斜视SAR的数据域多普勒参数估计方法。该方法可在雷达运动参数未知的情况下,利用距离多普勒域信号的统计特性,实现距离徙动校正,提高传统自聚焦方法的精度,进而实现解多普勒模糊。对于低对比度场景,该方法还可直接用于多普勒调频率的估计。仿真及理论分析表明,该方法对场景对比度有良好的稳健性。星载SAR数据的实验结果证明了该方法的有效性。     

星载SAR多普勒质心估计的改进方法

本文基于星载合成孔径雷达（SAR）多普勒质心估计的原理，提出估计多普勒质心的能量均衡逼近法，它改进了杂波锁定法的算法结构，减小了估计的运算量；同时还提出距离向加权拟合法，有效地改善了估计精度；最后利用星载SEASAT－ASAR原始数据，证明了这两种新方法的优越性。     

Multipolarization Radar Images for Geologic Mapping and Vegetation Discrimination

The NASA/JPL airborne synthetic aperture radar system produces radar image data simultaneously in four linear polarizations (HH, VV, VH, HV) at 24.6-cm wavelength (L-band), with 10-m resolution, across a swath width of approximately 10 km. The signal data are recorded optically and digitally and annotated in each of the channels to facilitate a completely automated digital correlation. Both standard amplitude, and also phase difference images are produced in the correlation process. Individual polarization and range-dependent gain functions improve the effective dynamic range, but as yet do not permit absolute quantitative measurements of the scattering coefficients. However, comparison of the relative intensities of the different polarizations in individual black-and-white and color composite images provides discriminatory mapping information. In the Death Valley, California, area, rough surfaces of young alluvial deposits produce strong responses at all polarizations. Smoother surfaces of older alluvial deposits show significantly lower responses. Evaporite deposits of different types and moisture contents have distinct polarization signatures. In the Wind River Basin, Wyoming, sedimentary rock units show polarization responses that relate to differences in weathering. Local intensity variations in like-polarization images result from topographic effects; strong cross-polarization responses denote the effects of vegetation cover and, in some cases, possible scattering from the subsurface. In the Savannah River Plant, South Carolina, forest cover characteristics are discriminated by polarization responses that reflect the density and structure of the canopy, and the presence or absence of standing water beneath the canopy.     

伽利略搜救信号FOA估计算法

在GALILEO/SAR系统中,FOA参数的估计精度直接决定着系统的定位精度。对GALILEO/SAR信号的特点进行了分析,在对FFT方法进行阐述的基础上,对Rife和相位差校正法2种频率估计算法进行了分析和仿真,并在此基础上提出了一种综合频率估计算法。该算法结合了上述2种算法的优点,在接收到达信号各频率区间和不同信噪比条件下,都可以满足到达信号频率检测的精度要求。     

匹配傅里叶变换的SAR多普勒参数估计

讨论了SAR的基本信号模型,针对这一模型提出了应用匹配傅里叶变换估计SAR多普勒参数的新方法。文中给出了理论分析和仿真,并用机载SAR回波实际数据进行了多普勒参数估计,根据估计的多普勒参数给出了成像结果,表明了该方法可对SAR数据进行盲处理估计出多普勒参数,且精度高。     

星载合成孔径雷达多普勒调频率估计精度分析

该文分析了星载合成孔径雷达成像处理中多普勒调频率估计与系统参数及图像特性的关系,给 出了利用轨道数据或回波信号数据估计多普勒调频率的精度与图像分辨率、雷达系统参数、轨道数据精度和 地物散射特性之间的关系。这些结论对系统的设计,以及数据处理方法的选择具有重要的参考价值。     

Estimation of the Minimum Number of Tracks for SAR Tomography

Synthetic aperture radar tomography (SARTom) is the natural extension of SAR interferometry to solve for multiple phase centers within a resolution cell and obtain the 3-D representation of a scene. This paper deals with the determination of the minimum number of tracks required to perform SARTom. Through the prolate spheroidal wave functions, the number of equivalent targets of a volumetric source is derived, and from it, the minimum number of observations required to apply subspace superresolution methods is computed. The minimum tomographic aperture length is also investigated. The results are validated on real data acquired in L-band by the experimental SAR system of the German Aerospace Center.      

伽利略搜救信号关键参数估计的克拉美—罗界

本文考虑信息位宽的不确定度,研究了伽利略搜救信号信息位宽、到达频率(FOA)和到达时间(TOA)估计的克拉美—罗界(CRB).首先推导了计算Fisher信息矩阵各元素的通用公式,然后推导得到了伽利略搜救信号Fisher 信息矩阵各元素的计算表达式.具体计算时,利用单位冲激函数的性质和Parseval定理,将单位冲激函数...     

基于运动参数估计的SAR成像

运动补偿是SAR成像,特别是高分辨成像的关键步骤.运动参数可由载机的导航仪器测得.也可通过实测数据估计得到,通常将两者结合.虽然基于数据的运动参数估计已有很多研究,并提出许多估计和补偿方法.但如何结合实际选用适合的方法仍然是个问题.本文针对实际雷达和运动情况,对运动参数作了精确估计和补偿,并提出了新的补偿和成像方法,可在减小运算量的同时获得好的成像效果.     

穿墙SAR成像中的墙体参数误差分析和估计

穿墙合成孔径雷达(SAR)成像中,图像的质量和可靠性由墙体参数决定。墙体参数估计误差会造成图像散焦和目标位置的偏移。分析了墙体参数估计误差对成像的影响,提出采用乘积型高阶模糊度函数(Product High-order Ambiguity Function, PHAF)算法来估计墙体参数的新方法。仿真结果表明,该方法能获得聚焦的SAR图像和较准确的墙体参数估计值。     

基于Radon变换的SAR成像多普勒模糊估计

文中主要分析合成孔径雷达(SAR)成像的多普勒模糊及其估计.首先推导了SAR斜视角和距离-多普勒(RD)域线性距离徙动斜率间的关系,通过在RD域而不是在距离-脉冲时域(RA域)来估计回波轨迹.讨论了基于Radon变换的RD域估计多普勒模糊数的方法.仿真实验和星载RADARSAT实测数据验证了估计算法的正确性与合理性.     

基于方向小波变换的SAR图像目标方位角估计

在合成孔径雷达(SAR)自动目标识别中,目标成像的方位信息是一个非常重要的特征。文中针对SAR图像特点,提出了一种基于方向小波变换的SAR图像目标方位角估计方法,给出了方向小波角度-能量谱公式,利用能量最大准则实现方位角估计。采用MSTAR SAR实测数据进行的实验表明本文方法是有效的,方向小波变换更能反映出目标图像的方位特征。     

多角度极化SAR图像中的非各向同性散射估计与消除方法研究

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.      

Through-the-Wall SAR Attributed Scattering Center Feature Estimation

We consider characterization of building interior structure from two-pass interferometric circular synthetic aperture radar data. We model returns from complex building structures as the sum of the responses from scattering primitives-plates, dihedrals, and trihedrals-observed through transfer functions that characterize both the transmission through and reflection from dielectric surfaces. Maximum-likelihood estimates for the location of primitive features and wall propagation/reflection parameters are obtained through a two-stage detection-and-estimation algorithm. We employ a sparse reconstruction algorithm to detect primitive signatures in the presence of wall effects and refine our estimates using a nonlinear minimization of local cost functions. We show that using simplified wall and primitive models, we can extract geometrically relevant features which can be combined to reveal 3-D floorplan estimates of buildings. Examples illustrate the effectiveness of the feature extraction approach.     

两种星载高分辨宽测绘带SAR系统通道相位误差估计方法

 本文针对星载方位多通道高分辨宽测绘带(HRWS)合成孔径雷达(SAR)系统,提出了两种通道相位误差估计方法:信号子空间比较法和天线方向图法.信号子空间比较法基于信号特征向量张成的空间(即信号子空间)与真实导向矢量张成的空间相同这一特性,得到各通道间的相对相位误差,该方法适用范围广,估计精度高,对系统要求低,且运算量小.天线方向图法结合天线方向图,直接估计通道相位误差,无须特征分解,无须矩阵求逆,运算量小,主要适用于均匀分布的场景.最后利用实测地基数据验证了两种方法的有效性.     

星载合成孔径雷达多普勒参数估计

本文给出了一种综合的星载合成孔径ＳＡＲ雷达多普勒参数估计方法，该方法可以从雷达回波数据本身提取多普勒进行成像处理，甚至可以不依赖卫星历数据和姿态数据作为初始估计。该方法是基于对多普勒参数及其误差的性质的研究而提出的。最后，利用ＳＥＡＳＡＴ－Ａ海洋卫星的ＳＡＲ原始数据的多普勒参数估计结果和采用该参数进行成像处理的结果，验证了该方法的可行性和有效性。     

利用自适应算法的快速估计参数进行图像纹理分割

本文提出使用Ｗｉｄｒｏｗ－ＨｏｆｆＬＭＳ自适应算法对二维随机场ＳＡＲ模型参数进行快速估计并报导了使用ＳＡＲ模型的自适应估计参数进行有监督纹理分类及纹理分割的实验结果，实验结果表明，ＳＡＲ模型的自适应快速估计参数能够比较有效地进行纹理识别。