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1.
A system model and its corresponding inversion for synthetic aperture radar (SAR) imaging are presented. The system model incorporates the spherical nature of a radar's radiation pattern at far field. The inverse method based on this model performs a spatial Fourier transform (Doppler processing) on the recorded signals with respect to the available coordinates of a translational radar (SAR) or target (inverse SAR). It is shown that the transformed data provide samples of the spatial Fourier transform of the target's reflectivity function. The inverse method can be modified to incorporate deviations of the radar's motion from its prescribed straight line path. The effects of finite aperture on resolution, reconstruction, and sampling constraints for the imaging problem are discussed. 相似文献
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Theory of synthetic aperture radar imaging of a moving target 总被引:4,自引:0,他引:4
Jen King Jao 《Geoscience and Remote Sensing, IEEE Transactions on》2001,39(9):1984-1992
Two novel image processing techniques have been developed to refocus a moving target image from its smeared response in the synthetic aperture radar (SAR) image which is focused on the stationary ground. Both approaches may be implemented with efficient fast Fourier transform (FFT) routines to process the Fourier spatial spectrum of the image data. The first approach utilizes a matched target filter that is derived from the signal history along the range-Doppler migration path mapped onto the SAR image from the moving target trajectory in real space. The coherent spatial filter is specified by the apparent target range in the image and the magnitude of the relative target-to-radar velocity. The second approach eliminates the range-dependence by reconstructing the moving target image from a spectral function that is obtained from the SAR image data spectrum via a spatial frequency coordinate transformation 相似文献
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This paper presents a system model and inversion for airborne synthetic aperture acoustic (SAA) imaging. The system model accurately represents the intercation of the acoustic source and the target region at near range values. Moreover, the model incorporates the fact that the relative speed of the vehicle's (transmitter/receiver) with respect to the target region is comparable to the acoustic wave propagation speed. The inversion utilizes the principle of spectral decomposition of spherical phase functions to develop a wavefront reconstruction method from SAA data. Processing issues and selection of appropriate acoustic FM-CW sources are discussed. Results are provided that exhibit the superior accuracy of the proposed SAA system model and inversion over their synthetic aperture radar (SAR) counterpart in which the vehicle's speed is assumed to be much smaller than the wave propagation speed 相似文献
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《Electronics & Communication Engineering Journal》1993,5(1):3-12
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 相似文献
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This paper presents a method for detecting moving targets embedded in foliage from the monostatic and bistatic synthetic aperture radar (SAR) data obtained via two airborne radars. The two radars, which are mounted on the same aircraft, have different coordinates in the along track (cross-range) domain. However, unlike the interferometric SAR systems used for topographic mapping, the two radars possess a common range and altitude (i.e., slant range). The resultant monopulse SAR images are used to construct difference and interferometric images for moving target detection. It is shown that the signatures of the stationary targets are weakened in these images. Methods for estimating a moving target's motion parameters are discussed. Results for an ultrawideband UHF SAR system are presented. 相似文献
7.
Capabilities of Dual-Frequency Millimeter Wave SAR With Monopulse Processing for Ground Moving Target Indication 总被引:4,自引:0,他引:4
Maurice Ruegg Erich Meier Daniel Nuesch 《Geoscience and Remote Sensing, IEEE Transactions on》2007,45(3):539-553
Ground moving target indication (GMTI) for synthetic aperture radar (SAR) provides information on nonstatic objects in radar imagery of a static ground scene. An efficient approach for GMTI is the use of multichannel SAR systems for a space- and time-variant analysis of moving targets. This allows the indication, correction of position displacement, and estimation of radial velocity components of moving targets in a SAR image. All three steps are possible due to a determinable Doppler frequency shift in the radar signal caused by radial target movement. This paper focuses on the millimeter wave (mmW) SAR system MEMPHIS with multichannel amplitude-comparison monopulse data acquisition and the ability to use carrier frequencies of 35 and 94 GHz simultaneously, making it a dual-frequency SAR. This paper includes mmW-specific SAR GMTI considerations, an adaptive algorithm to collect velocity and position information on moving targets with mmW monopulse radar, and a discussion on GMTI blind speed elimination and target velocity ambiguity resolving by dual-frequency SAR. To determine the capabilities of both, system and algorithm, three large-scale experiments with MEMPHIS in different environments are presented 相似文献
8.
舰船的混合SAR—ISAR成像研究 总被引:1,自引:0,他引:1
运动机载雷达对海面运动舰船目标成像时,由于相对运动的复杂性,直接成像难以达到理想效果。因此必须事先估计两者相对运动变化,对数据段有选择地成像。本文基于图像投影平面原理,分析了机载雷达和舰船目标各自的运动特点,提出了采用子图像多普勒展宽估计雷达与目标相对运动的变化过程,并以此为依据,合理选择观测数据段成像,从而降低了成像难度,提高了成像质量。 相似文献
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《Signal Processing Magazine, IEEE》1995,12(4):21-40
The author addresses the problem of detecting and identifying stationary and moving targets with foliage penetrating UHF synthetic aperture radar (SAR). The role of a target's coherent SAR signature, which varies with the radar's frequency and aspect angle, in forming the Fourier space of the SAR signal is analyzed. The resultant relationship is the basis of an algorithm which, after extracting (digital spotlighting) the target's coherent SAR signature in the reconstruction domain, could be used to differentiate man-made structures from foliage. Methods for blind-velocity moving target indication are discussed. The main tool of the work is a signal theory based analysis of SAR signal via Fourier transform. However, the theory is at most as good as the collected SAR data 相似文献
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An inversion method is presented for bistatic synthetic aperture radar imaging. The method is based on a Fourier analysis (Doppler processing) of the bistatic synthesized array's data followed by a phase modulation analysis of the Doppler data. The approach incorporates the phase information of the wavefront curvature in the transmitted waves as well as the resultant echoed signals. The Doppler data are shown to provide samples of the reflectivity function's spatial Fourier transform within a band that depends upon the bistatic angles and ranges. Associated resolution, reconstruction, and sampling constraints for the imaging problem are discussed. The bistatic SAR inversion is also utilized to formulate an inversion for multistatic measurements made along a physical linear array due to a single transmission to image a dynamic object 相似文献
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介绍了基于运动补偿的运动目标ISAR成像方法,将雷达成像的概念引入到低信噪比运动目标探测的过程中,在成像的同时获取目标的径向和横向运动速度,采用多基线图像干涉处理的方法完成运动目标的定位和横向尺寸估计.建立了运动目标成像几何模型,给出了多天线时分复用接收机的通道间信号补偿方法,以及多基线相位解缠实现不模糊干涉测角定位的方法,分析了信噪比对图像干涉定位精度的影响.利用仿真数据和实际数据验证了本方法的有效性. 相似文献
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Qun Zhang Tat Soon Yeo 《Geoscience and Remote Sensing, IEEE Transactions on》2004,42(9):1818-1828
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. 相似文献
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基于雷达散射特性的高分辨率SAR图像自动目标识别 总被引:4,自引:4,他引:0
高分辨率SAR的迅速发展为自动目标识别提供了可能,为了克服存储海量模板带来的计算复杂性,发展基于模型的目标识别现已成为新的国际研究热点.先由目标的真实三维模型依据电磁波散射理论计算雷达散射截面(RCS),利用宽带合成孔径技术得出目标散射特性的空间分辨率图像,进而基于模拟图像实现目标的CFAR检测.最后利用我国机载高分辨率SAR图像对该方法进行实验,验证了本文提出的基于雷达散射特性目标识别的有效性. 相似文献
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在对复杂运动目标进行逆合成孔径雷达成像时,由于转动矢量随时间而变化,回波信号中会引入一个与散射点位置有关的相位误差,无法用通常的相位补偿方法进行校正,应用距离-多普勒算法获得的ISAR(Inverse Synthetic Aperture Radar)像会变得模糊.本文分析了目标转动矢量变化使得ISAR像模糊的内在原因,给出了目标三维转动状态下的ISAR信号形式,并基于散射点信号的特点提出了一种复杂运动目标的ISAR成像算法.该算法不仅适用于转动矢量方向不变的非均匀转动目标,而且对于转动矢量方向缓慢变化的目标,算法仍然能够有效地提高ISAR成像的质量.仿真试验结果表明了该算法的有效性. 相似文献
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干涉式逆合成孔径雷达(InISAR)成像是一种将干涉技术与逆合成孔径分辨相结合的高分辨雷达三维成像方法,能够实现对远距离运动目标全天候、全天时的三维成像,在军事和民用领域都呈现出广泛的应用前景和实用价值。其基本思想是利用位置分布不同的多个天线获取成一定视角差的多幅逆合成孔径雷达(ISAR)复图像,实现目标散射中心的二维分辨,然后通过干涉相位处理,恢复出目标散射中心的真实三维分布。本文综述了InISAR三维成像的理论框架,回顾了InISAR成像技术的发展历程,着重对图像配准、相位解缠绕、运动补偿、斜视、基线配置等关键技术难点进行了分析和评估,明确了研究中存在的问题,阐述了有待进一步研究的方向,最后对InISAR的发展现状和趋势进行了总结和展望。 相似文献
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合成孔径雷达成像应用于观察包含运动目标的地面场景,特别是在对运动目标观察时间长的情况下,图像会产生由于距离徙动和多普勒频谱展宽引起的运动目标偏移。为了消除这些影响,本文提出一种适应于星载高低轨平台协作模式下对动目标进行检测成像的算法。距离徙动包括运动范围内的距离走动和距离弯曲可以通过广义keystone变换校正。然后,通过估计和补偿相位误差和折叠因子项,可以提高运动目标的分辨率。针对地面场景中的杂波,我们通过子孔径对消的方法进行抑制。该算法的有效性通过仿真结果进行验证。通过将广义keystone方法与子孔径对消方法结合,可以有效地对消静止目标杂波,从而更好的对动目标进行检测成像。 相似文献
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针对调频连续波(FMCW)交通监测雷达车辆目标速度测量和长度估计问题,建立了基于逆合成孔径雷达( ISAR)原理的雷达回波数学模型,分析了待测量目标运动速度与多普勒参数的内在关系,采用基于最大对比度算法(MCA)的多普勒调频斜率的估计方法,能有效提高雷达的车辆监测效能,仿真数据分析以及实测数据的结果均验证了算法的有效性.实验结果表明,最大对比度算法可以准确地估计出移动目标的移动速度并能提供车辆长度信息,为交通监控提供了新的途径和方法. 相似文献