弹载SAR大斜视角成像算法研究

发布时间：2018-04-09 22:34

  本文选题：弹载合成孔径雷达　切入点：大斜视角成像　出处：《电子科技大学》2014年硕士论文

【摘要】：众所周知,合成孔径雷达(Synthetic Aperture Radar,SAR)能够进行距离向和方位向的二维成像,其成像模式是利用电磁波进行主动成像,因此可以不受外界天气环境的影响获取高分辨率雷达图像,目前SAR成像已经很成熟的应用在星载和机载平台上,但是在弹载平台上应用还不太成熟。SAR成像获取的是距离向和方位向的二维信号,与传统的红外成像、激光成像和一维距离成像相比,其具有得天独厚的优势。具体表现在以下几点:其一,可以不受日光辐射、云雾遮挡和其他恶劣天气条件的影响而进行全天候全天时成像;其二,具有一定的穿透能力,选择合适的频段,SAR可以穿透一些天然植被、人工伪装,从而可以探测到伪装的装甲车、坦克和导弹发射井等目标;其三,由于SAR导引头具有方位向信息,因此其能够提供丰富的目标电磁信息,得到散射点的强度和幅度等电磁散射信息,而一维距离成像无法实现这样的目的。鉴于此,本文对弹载合成孔径雷达的斜视成像算法进行了研究,研究的主要内容如下:1.通过对机载SAR正侧视成像算法进行推广,研究了弹载SAR平飞阶段大斜视成像算法,斜视角最大可以达到50°。该算法首先对瞬时斜距方程进行研究分析,利用驻定相位原理推导出这种模式条件下的二维频域表达式,结合时域距离走动校正方法,给出了改进的距离多普勒算法,并用MATLAB对此算法进行了验证仿真,证明算法的有效性。2.研究了弹载SAR俯冲下降阶段(方位向和垂直向存在速度和加速度)和曲线规避阶段(方位向、距离向和垂直向存在速度和加速度)正侧视及斜视成像算法。算法首先对弹载模式下的瞬时斜距进行分析,然后利用泰勒级数展开和级数反演的方法推导了出两种条件下的二维频域表达式,最后在二维频域对信号进行相应的处理,并用MATLAB对该算法进行了仿真验证,证明了算法的可行性。3.设计了一套SAR成像仿真软件。利用Matcom软件将Visual C++和MATLAB进行相关级联,实现联合编程。该成像仿真软件很好地利用了Visual C++的可视化编程能力和MATLAB比较强大的计算能力,并且在成像的时候能够摆脱对MATLAB环境的依赖,具有很好的移植性。最后概括了本文的研究内容以及完成的内容,指出研究课题过程中存在一些不足、需要改进的地方和需要解决的问题。
[Abstract]:It is well known that synthetic Aperture radar (SAR) can perform two dimensional imaging in the range and azimuth directions. Its imaging mode is to use electromagnetic waves for active imaging, so that high resolution radar images can be obtained without the influence of the external weather environment.At present, SAR imaging has been used in spaceborne and airborne platforms, but it is not very mature in missile-borne platform. What we can get is the two-dimensional signal in range and azimuth direction, and the traditional infrared imaging.Compared with one-dimensional range imaging, laser imaging has unique advantages.It is shown in the following aspects: first, all-weather all-weather imaging can be carried out without the influence of solar radiation, fog and clouds, and other adverse weather conditions; and second, it has a certain penetration capability.Selecting the appropriate frequency band can penetrate some natural vegetation and artificially camouflage, so as to detect camouflaged armored vehicles, tanks and missile silos, etc. Third, because the SAR seeker has azimuth information,Therefore, it can provide abundant electromagnetic information of the target and obtain the electromagnetic scattering information such as the intensity and amplitude of the scattering point, which can not be achieved by one-dimensional range imaging.In view of this, the strabismus imaging algorithm of missile-borne synthetic aperture radar (SAR) is studied in this paper. The main contents of the research are as follows: 1.By popularizing the forward side imaging algorithm of airborne SAR, a large squint imaging algorithm for projectile-borne SAR is studied. The maximum oblique angle can reach 50 掳.Firstly, the instantaneous slant distance equation is studied and analyzed, and the expression of two-dimensional frequency domain under this mode is derived by using the stationary phase principle. The improved range Doppler algorithm is presented in combination with the time domain range walk correction method.The algorithm is verified by MATLAB, and the validity of the algorithm is proved. 2. 2.In this paper, the forward and squint imaging algorithms for projectile borne SAR subduction and descent stages (azimuth and vertical velocity and acceleration) and curve evading (azimuth, range and vertical velocity and acceleration) are studied.The algorithm firstly analyzes the instantaneous oblique distance in the projectile mode, and then derives the expression of the two-dimensional frequency domain under two conditions by using Taylor series expansion and series inversion method. Finally, the signal is processed in the two-dimensional frequency domain.The algorithm is verified by MATLAB, and the feasibility of the algorithm is proved. 3. 3.A set of SAR imaging simulation software is designed.Visual C and MATLAB are concatenated by Matcom software to realize joint programming.The imaging simulation software makes good use of the visual programming ability of Visual C and the powerful computing power of MATLAB, and can get rid of the dependence on MATLAB environment when imaging, so it has good portability.Finally, this paper summarizes the research content and the finished content, points out that there are some shortcomings in the course of the research, the place that needs to be improved and the problems that need to be solved.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN957.52
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本文编号：1728492