共查询到19条相似文献,搜索用时 595 毫秒
1.
海面成像模拟是对海作战导弹弹载合成孔径雷达(SAR)成像制导全过程动态仿真的重要组成部分,对于系统的性能分析和优化设计具有重要意义。研究了弹载情况下SAR对海成像模拟问题,提出了基于三维海面波动模型及弹载SAR工作过程的成像模拟方案。出于逼真性及运算速度的考虑,仿真时动态海面选用基于海浪谱的双尺度模型,海面散射模型选用双尺度散射模型。结合一组典型弹载SAR系统参数,分别在正侧视和斜视模式下对三种典型海况的动态海面进行了成像模拟,并利用实际海面SAR图像的统计特性验证了模拟结果的有效性。 相似文献
2.
3.
4.
5.
针对弹载景象匹配SAR应用中的弹体定位问题,提出了基于INS/双天线SAR的组合弹体定位技术,通过加装一部向下照射的天线系统,在对典型地物成像的同时实现了对弹体离地面高度的测量.首先介绍了其定位原理,然后推导了利用相对距离、多普勒和弹体高度的定位模型,给出了导弹高度测量误差对定位误差影响的关系式,针对不同的地形起伏,分别提出了基于迭代和地形匹配的弹下点高程误差消除方法,最后分析了双天线定位方法对雷达系统的要求.对典型场景的仿真表明,该定位方法相比利用INS高度通道数据和气压高度计进行定位误差明显减小. 相似文献
6.
本文基于多相位屏理论,研究了电离层闪烁对GEO SAR成像的影响。首先针对电离层各向异性的特点,修正了各向异性电子密度起伏的功率谱,并重新推导了斜入射条件下随机介质中的电磁波传播方程,改进了传统的基于垂直入射和各向同性电离层条件下的多相屏仿真方法,然后结合典型GEO SAR参数,分析了电离层闪烁对GEO SAR成像的影响。最后,通过Monte Carlo仿真,给出了不同电离层电子密度起伏条件下GEO SAR进行合成孔径处理的最优积累时间。分析结果表明,相同GEO SAR系统配置下,电离层闪烁的起伏越大,合成时间越长,GEO SAR成像质量越差,甚至会出现无法聚焦的情况。 相似文献
7.
8.
9.
10.
11.
Mingquan Bao Bruning C. Alpers W. 《Geoscience and Remote Sensing, IEEE Transactions on》1997,35(3):618-631
A two-dimensional (2D) model for describing the imaging of ocean waves by an along-track interferometric synthetic aperture radar (AT-INSAR) is derived. It includes the modulation of the normalized radar cross section by the long waves, velocity bunching, and azimuthal image smear due to orbital acceleration associated with long waves and due to the orbital velocity spread within the AT-INSAR resolution cell (parameterized by the scene coherence time). By applying the Monte-Carlo method, AT-INSAR amplitude and phase image spectra are calculated for different sea states and radar configurations. The Monte-Carlo simulations show that velocity bunching affects the AT-INSAR imaging mechanism of ocean waves, and that a unimodal ocean wave spectrum may be mapped into a bimodal AT-INSAR phase image spectrum due to an interference between the velocity term and the velocity bunching term in the AT-INSAR imaging model. It is shown that the AT-INSAR imaging mechanism of ocean waves depends on the ratio of the scene coherence time and the time separation between the observations by the two antennas. If this ratio is larger than one, the AT-INSAR phase image spectra are distorted. Furthermore, the simulations show that the AT-INSAR phase image spectrum is quite insensitive to the ocean wave-radar modulation transfer function. Comparing AT-INSAR with conventional SAR imaging of ocean waves, the authors find that the azimuthal cut-off in AT-INSAR phase image spectra is shifted toward higher wavenumbers than in conventional SAR image spectra. This implies that AT-INSAR can resolve shorter azimuthal wavenumbers than conventional SAR. Thus the authors conclude that AT-INSAR phase images are better suited for measuring ocean waves spectra than conventional SAR images 相似文献
12.
When deriving a directional ocean wave spectrum from a synthetic-aperture radar (SAR) image of the ocean surface, spectral analysis of the image data is a key step. In this paper, a quantitative comparison of spectral analysis techniques for analysis of multilook SAR image data of ocean waves is presented. Performance is rated using a spectral SNR, defined as the ratio of the desired spectral signature to the speckle noise as it appears in the SAR image spectrum. Spectral techniques considered cover all of those now in use (including SAR processor focus adjustment) as well as new experimental methods. It is shown that the spectral-phase-shift technique, introduced in this paper, is the best approach: it maximizes the spectral SNR, it allows resolution of the 180° directional ambiguity, and it applies simultaneously to all wave components present in the scene 相似文献
13.
一种弹载侧视SAR大场景成像算法 总被引:8,自引:5,他引:3
导弹的俯冲加速运动所带来的较大距离徙动使得SAR成像难度较大。该文根据弹载SAR平台的运动特点,使用高阶逼近模型建立了SAR的回波信号模型。考虑到大场景下的距离空变问题,对目标斜距随时间的变化进行了详细的分析。结合级数反演法,得到了弹载SAR回波信号的2维频域的精确表达式。基于此式,提出了一种适用于弹载SAR俯冲加速运动下的大场景成像算法。理论分析和实验结果表明,该算法对较大场景取得了较好的成像效果,距离向和方位向分辨率都达到了理论分辨率。 相似文献
14.
On the Relative Importance of Motion-Related Contributions to the SAR Imaging Mechanism of Ocean Surface Waves 总被引:1,自引:0,他引:1
The relative importance of the various motion-related contributions to the SAR imaging mechanism of ocean surface waves is studied by using two-dimensional Monte Carlo simulation techniques. It is shown that for wind waves the often-observed stretching of the peak wavelength and the rotation of the spectral peak toward the range direction is caused by both the degradation in azimuthal resolution and the nonlinearity of the velocity bunching mechanism. The distortion of the SAR image spectrum relative to the ocean wave spectrum due to the degradation in azimuthal resolution is mainly caused by the spread of the radial facet velocities within a SAR resolution cell. The effect of the radial orbital acceleration arising from the long waves of scales larger than a SAR resolution cell on the nonlinearity of the SAR imaging mechanism is small. It is argued that the effect of the wave motions on the SAR imaging mechanism cannot always be reduced to a linear azimuthal low-pass filter acting on the ocean slope spectrum. In those cases where the imaging is nonlinear, the ocean wave spectrum cannot be retrieved from the SAR image spectrum by applying linear inversion techniques. For swell imaging, the nonlinearities are usually less strong because swell spectra have a narrower width than wind spectra. Computer simulations of SAR imaging of fully developed wind seas with different peak wavelengths and propagation directions are presented. 相似文献
15.
16.
Alpers W. Bruening C. Richter K. 《Geoscience and Remote Sensing, IEEE Transactions on》1986,(4):559-566
During the SIR-B mission over the North Sea, two successful synthetic aperture radar (SAR) data takes with simultaneous buoy measurements of ocean wave spectra have been obtained on October 6 and 8, 1984. On October 6, the SAR imaging of ocean waves was predicted as strongly nonlinear and on October 8 as almost linear. The SIR-B experiment confirmed the theoretical predictions. By applying the SAR imaging model based on velocity bunching theory the SAR image spectra are calculated from the measured ocean wave spectra. These calculated SAR image spectra are compared with the SIR-B derived SAR image spectra and it is shown that both agree quite well. This is considered as a further experimental confirmation for the velocity bunching model that has been proposed for describing SAR imaging of ocean surface waves. 相似文献
17.
SAR图像港口区域舰船检测新方法 总被引:1,自引:0,他引:1
SAR图像港口内舰船检测是SAR图像海洋应用研究的重要方面。快速、准确地检测港口内舰船将大大提高SAR图像的自动解译能力。该文通过分析港口内舰船停靠特点,提出了一种新的SAR图像港口内舰船检测方法。首先基于港口岸线获取港口沿岸区域SAR图像,然后详细分析了港口沿岸区域SAR图像的杂波统计特性,进而采用基于G0分布的CFAR(Constant False Alarm Rate)检测算法完成了港口内舰船检测。实验结果表明,新方法能有效地将不同形状的港口区域的舰船与绝大部分陆地分开,具有港口内舰船检测率高、虚警率低等特点。 相似文献
18.
19.
Cross spectra of individual-look synthetic aperture radar (SAR) images of the ocean surface are used to retrieve ocean wave spectra. A quasilinear transform is derived that relates ocean wave spectra to SAR image cross spectra. Furthermore, Monte Carlo simulations are also carried out for those cases where quasilinear imaging does not apply. It is shown that, as the time separation between the individual-look SAR images increases (within a limit determined by the Doppler bandwidth of the original single-look complex SAR image), the spectral energy density of the imaginary part of the SAR image cross spectra increases, while the spectral energy density of the real part decreases. The integration time has a small effect on the SAR image cross spectra as long as the integration time is large compared to the scene coherence time. In order to retrieve ocean wave spectra from SAR data by using cross-spectral analysis techniques, the authors suggest calculating two SAR image cross spectra: one with a short time separation and one with a large one between the individual-look SAR images. The real part of the SAR image cross spectra calculated from individual-look SAR images with the short time separation is used for retrieving ocean wave spectra, which have a 180° ambiguity in wave propagation direction. The imaginary part of the SAR image cross spectra calculated from individual-look SAR images with the long time separation is used for removing this 180° ambiguity 相似文献