基于协方差矩阵特征分解的多通道SAR-GMTI方法及性能分析

该文提出了一种基于协方差矩阵特征分解的多通道运动目标检测和测速定位方法,该方法依据多通道SAR数据协方差矩阵特征分解后小特征值和的幅度变化来检测运动目标。在检测出运动目标后,先利用两幅复图像的干涉相位对目标径向速度进行粗略估计,再通过搜索动目标空域导向矢量的方法对径向速度进行精确估计,克服了干涉相位对杂波和噪声的敏感性。仿真数据和实测数据验证了该方法的有效性。     

Signal subspace fusion of uncalibrated sensors with application inSAR and diagnostic medicine

Addresses the problem of fusing the information content of two uncalibrated sensors. This problem arises in registering images of a scene when it is viewed via two different sensory systems, or detecting change in a scene when it is viewed at two different time points by a sensory system, or via two different sensory systems or observation channels. We are concerned with sensory systems which have not only a relative shift, scaling and rotational calibration error, but also an unknown point spread function (that is time varying for a single sensor, or different for two sensors). By modeling one image in terms of an unknown linear combination of the other image, its powers and their spatially transformed (shift, rotation and scaling) versions, a signal subspace processing is developed for fusing uncalibrated sensors. The proposed method is shown to be applicable in moving target detection (MTD) using monopulse synthetic aperture radar (SAR) with uncalibrated radars. Results are shown for video, magnetic resonance images of a human brain, moving target detector monopulse SAR, and registration of SAR images of a target obtained via two different radars or at different coordinates by the same radar for automatic target recognition (ATR).     

基于稀疏表示和道路辅助的单幅SAR图像运动目标检测方法

本文提出一种利用单幅SAR(Synthetic Aperture Radar)图像实现运动目标检测的方法.首先提出一种基于压缩感知的SAR图像道路检测算法:根据SAR图像中道路的特点,使用模糊C均值方法将图像进行模糊分类,获得大致的道路区域,然后利用Hough变换域的稀疏性,用压缩感知精确定位图像中的道路信息.其次利用图像稀疏表示的方法对运动目标进行检测:不同速度运动目标的散焦量和距离单元跨越不同,由此生成样本图像,继而构造超完备字典.将待测图像分块,并计算子图像在字典下的稀疏系数,检测并匹配出运动目标的速度参数.最后,结合已检测出的道路辅助信息,消除多普勒模糊影响,剔除虚假的运动目标,并对运动目标速度参数进行校正.实验结果证明了所提方法的有效性.     

Imaging and MTI processing based on dual-frequencies dual-apertures spaceborne SAR

Based on dual-frequencies dual-apertures spaceborne SAR (Synthetic Aperture Radar), a new SAR system with four receiving channels and two operation modes is presented in this paper. SAR imaging and Moving Target Indication (MTI) are studied in this system. High resolution imaging with wide swath is implemented by the Mode I, and MTI is completed by the Mode II. High azimuth resolution is achieved by the Displaced Phase Center (DPC) multibeam technique. And the Coherent Accumulation (CA) method, which combines dual channels data of different carrier frequency, is used to enhance the range resolution. For the data of different carrier frequency, the two aperture interferometric processing is executed to implement clutter cancellation, respectively. And the couple of clutter suppressed data are employed to implement Dual Carrier Frequency Conjugate Processing (DCFCP), then both slow and fast moving targets detection can be completed, followed by moving target imaging. The simulation results show the validity of the signal processing method of this new SAR system.     

Resolving revolutions: imaging and mapping by modern radar

High-performance synthetic aperture radars (SARs) for mapping demand massive digital signal processing powers. The fall in the cost of computing devices has recently passed the point at which such processors can be afforded and SARs are now being used in a range of applications. The analogous inverse synthetic aperture radar (ISAR), which enables moving targets to be imaged by stationary or moving radars, is also becoming widely used. The unifying principle underlying SARs and ISARs is presented and the common parameters defining the performances of both types of radar are derived. A novel technique is described which enables the radar to measure the random angular spin of a ship at sea, thereby permitting it to be imaged deterministically by ISAR. Results are presented from a representative selection of ISARs and SARs ranging from the imaging of model targets by ISARs operating at scaled-up frequencies through to the mapping of the surface of Venus by a satellite SAR. The paper concludes with a review of likely future developments of these types of radar and suggests that further major advances are possible     

Improving Coherence of Complex Image Pairs Obtained by Along-Track Bistatic SARs Using Range–Azimuth Prefiltering

An along-track interferometric synthetic aperture radar (SAR) can be used for ground moving target indication (GMTI) by comparing two SAR images obtained at different observation times. Different geometries of the two observations bring the decorrelation noise, which will degrade the detection performance. For bistatic SARs, the decorrelation theory is quite different from that for monostatic ones. This paper deals with the coherence between two complex SAR images formed by two along-track bistatic SARs with different baseline lengths. Using the single scattering model, the coherence between the two echoes collected by the two receivers is investigated, and the full-coherence conditions are derived. Then, a new method based on range-azimuth prefiltering is proposed to improve the coherence of complex image pairs. As the precise prefiltering is complicated, its three approximate implementations are given. The effects of prefiltering on SAR images are also analyzed. Finally, simulation results validate the effectiveness of the proposed method.     

一种单通道SAR地面运动目标成像和运动参数估计方法

根据单通道高分辨SAR(Synthetic Aperture Radar)运动目标的回波包络和多普勒频谱的特性,本文提出一种利用二阶Keystone变换校正回波数据的距离弯曲,然后估计回波包络的斜率进行走动校正,再对运动目标的多普勒频谱进行分析得到运动目标的多普勒参数,进而对地面运动目标进行成像,同时完成对运动目标的定位,使运动目标在SAR图像中的正确位置上显示.另外,根据地面运动目标的多普勒参数和运动参数的关系,可以估计出运动目标的关键运动参数.结合仿真和实测数据的处理结果表明该方法可有效地对地面运动目标成像和运动参数估计.     

一种针对多通道GMTI的SAR复图像精确配准方法

提出了一种针对多通道GMTI的SAR复图像精确配准算法。首先,系统分析了配准误差对干涉相位的影响,推导出了对应配准误差的干涉相位Cramer-Rao界,并利用Monte Carlo仿真数据对配准误差的影响进行了量化。在此基础上,通过对待配准图像进行二维精确插值处理,生成模板图像库和相应的相关系数库,以适合多通道GMTI的复图像的相位相关为准则,找出模板图像库和相关系数库中与参考图像具有最大相位相关值的图像作为配准图像,从而实现多通道SAR复图像之间的精确配准。对基于所提算法的实测三通道SAR复图像进行慢动目标检测实验,结果表明所提算法能够提供多通道GMTI所需要的配准精度,证明了该算法的有效性和实用性。      

星载干涉SAR中的基线问题

基线在星载干涉SAR的系统设计和数据处理中起着非常重要的作用.本文比较全面地阐述了空间基线在星载干涉SAR中的作用.特别分析了星载干涉SAR中空间基线对SAR图像相关性、地距分辨率以及干涉SAR数据处理中的距离向平地效应和多视平均处理的影响.讨论了星载干涉SAR空间基线的设计问题,推导了空间最优基线的确定公式.最后进行了计算机仿真,仿真结果表明分析正确.     

一种新的双孔径天线干涉SAR动目标检测方法

提出了一种基于双孔径天线沿航迹向干涉SAR进行动目标检测、测速及定位的新方法.该方法在分析杂波对消必要性的基础上,给出了进行地杂波对消、动目标检测、径向速度分量估计及定位的原理和实现方法.在恒虚警处理后,通过比较杂波对消后的残差图像与原始图像中运动目标和静止目标对消幅度的差异,检测出运动目标.同时,可以利用残差图象中杂波的对消特性进行运动目标径向速度的估算以及目标的定位.这种检测方法具有良好的杂波对消性能,能够完成被地面背景杂波掩盖的运动目标的检测、测速及定位.计算机仿真结果验证了其有效性.     

基于ATI的双通道UWB SAR运动目标检测和距离向速度估计

本文对基于ATI的双通道UWB SAR运动目标检测和距离向速度估计算法进行了研究.针对运动目标易在UWB SAR图像上散焦的特点,本文对运动目标在双通道UWB SAR图像上散焦像轨迹之间的位置关系及干涉相位进行了分析;针对ATI算法运动目标检测中的盲速现象和距离向速度估计时的距离向速度模糊现象,本文根据UWB SAR大相对带宽的特点,提出了一种多频子带ATI方法消除盲速区、解除距离向速度模糊,该方法只需两部接收天线,相比多基线方法可大大节省硬件成本.基于半实测数据的实验证明了本文所提理论正确性和算法的有效性.     

基于样本加权的三通道SAR-GMTI机载 数据处理及性能分析

 针对机载三通道雷达系统的杂波抑制问题,提出基于样本加权估计杂波相关矩阵的三通道联合动目标检测方法.基于广义内积值对像素矢量样本加权,三通道联合杂波抑制后检测出动目标位置,局部两两干涉实现动目标重定位和测速,最后进行了性能分析.所提方法无需设置样本选取门限,对图像配准精度仅要求在1个像素以内,样本加权后改善因子提高明显;3幅图像联合处理的性能优于2幅图像处理.机载实测数据处理结果验证了方法的有效性和稳健性.     

基于地球同步轨道合成孔径雷达的双基地探测系统: 概念及潜力

低空小目标容易被地物杂波和噪声淹没,影响雷达的探测性能,对国土防空具有较大威胁。星载双基地雷达因其覆盖范围广、相参积累时间长、不受地形遮挡影响等优点,在低空小目标探测方面具有独特优势。本文提出了一种基于地球同步轨道合成孔径雷达（GEO SAR）的双基地雷达探测系统;在GEO SAR卫星照射、地面（或飞艇）接收的系统配置下,研究了接收机作用距离与双基地角和接收天线面积的关系;并就长时间相参积累、多路径干扰抑制、时间同步与相位同步以及波束扫描与波束管理等关键技术进行了讨论,给出了初步的解决方案。      

车载毫米波SAR对近海域的成像及监测

针对近海域监测的应用背景,介绍了一种用于近海监测的车载毫米波SAR系统,该系统灵活机动、费用低廉,结合了毫米波和SAR的特点,能够实砚对近岸静止扣活动目标的高分辨成像及监测。在此对某次实验获得的SAR数据进行了成像处理,由于在系统要求的作用距离范围内,距离单元数不是很多,可对每个距离单元都构造一个方位匹配函数,保证方位向的高分辨率不受损失,为海面舰船目标的检测研究提供高分辨SAR图像。     

Three-dimensional SAR imaging of a ground moving target using the InISAR technique

In this paper, a three-dimensional (3-D) interferometric synthetic aperture radar (ISAR) imaging method for moving targets is presented. This imaging method is based on the ISAR principle and the simple observation that all scatterers on a moving target move in tandem. The angular motion parameters in the cross-range directions could be estimated using the overall range profile of the moving target. Registration of the respective complex images at the two (or more) interferometric antennas can then be achieved via compensating the respective echoes at the raw data level, thus avoiding phase-unwrapping processing and image-resampling processing as required by conventional methods. Finally, a 3-D image of the moving target can then be reconstructed from the 3-D spatial coordinates of these scatterers. Furthermore, the method works well even for a target moving in heavily cluttered environments.     

基于DPCA和干涉技术的SAR动目标检测

通过分析相位中心偏置天线(DPCA)技术和干涉处理的优点和缺点,该文提出了一种用三孔径合成孔径雷达(SAR)对地面运动目标进行检测的新方法。该方法不仅能够检测出动目标,还能够精确估计动目标参数,即确定出动目标的真实位置和运动速度,然后对动目标聚焦成像。该文方法简单,运算量小,通过计算机仿真数据验证了该文算法的正确性和有效性。     

用聚束SAR对慢速运动目标进行轨迹跟踪和参数估计的方法

针对聚束式合成孔径雷达(SAR)动目标检测的问题,把回波信号进行连续重叠地时域分组,每组信号可以看成是来自一个时域子孔径, 然后在每个子孔径内分别成像。地面固定目标在每幅图像上的成像情况是相同的, 通过彼此相减就可以消去,达到了抑制杂波的目的,而运动目标由于每个时刻的位置都在变化,在每幅图像上的位置是不同的, 从而在相减后剩余下运动目标的图像,把这些图像拼接起来就再现了运动目标的运动轨迹,根据运动轨迹就可以对其运动参数进行估计。该文给出了这个方法的原理推导和具体的检测过程。仿真结果证明了该方法的有效性。     

A time-domain raw signal Simulator for interferometric SAR

In this paper, we present a time-domain (TD) raw signal simulator for an interferometric synthetic aperture radar (SAR). We consider the case of a spaceborne SAR operating in stripmap, spotlight, and hybrid modes, but the case of an airborne SAR can be considered as well. The spaceborne platform is considered as traveling on its nominal (Keplerian) orbit, and the targets are located on an ellipsoidal earth. We describe an accurate TD simulator, highlighting its usefulness in studying the effects on the SAR impulse response and on images from targets with limited extension due to operational conditions different from the nominal one.     

改进混合积累的单通道机载SAR高径向速度目标检测方法

高径向速度目标会产生严重的距离走动并伴随方位失配,方位压缩会使其散焦并弥散在SAR图像中,不易被检测。该文针对高径向速度目标的检测问题,提出一种基于单通道机载SAR的检测方法。该方法通过抽取等效双通道,利用相干对消抑制杂波,并去除动目标的频谱分裂,再运用Dechirp处理和Hough变换积累目标在距离单元内和距离单元间的能量,以获得更大的积累增益。与传统的混合积累方法相比,该方法在抑制杂波的基础上,更好地积累高径向速度目标的能量,从而有效提高该类目标的检测性能。仿真数据和实测数据均验证了该方法的有效性和优越性。     

三通道TOPSAR-GMTI技术研究

多通道宽带雷达不仅要求能够对大场景进行高分辨成像,而且要求具有动目标检测的能力。该文提出一种三通道TOPSAR模式下对地面动目标检测与定位(GMTI)的方法。首先建立三通道TOPSAR-GMTI系统几何模型,并对三通道回波数据进行全孔径成像,然后采用相位中心偏置天线(DPCA)和双门限单元平均恒虚警(CFAR)检测方法完成动目标的检测,最后推导出TOPSAR-GMTI模式下动目标干涉相位与速度的关系,完成对动目标的速度估计并在SAR图像中对其进行重新精确定位。仿真数据处理结果验证了该算法的有效性。