【作者】 魏青；

【导师】 杨绍全；

【作者基本信息】 西安电子科技大学 ， 通信与信息系统， 2007， 博士

【摘要】 合成孔径雷达是一种能够全天候、全天时、远距离提供高分辨率雷达图像的成像雷达,它的出现扩展了原始的雷达概念,它具有对区域目标进行成像和识别的能力,在军用和民用领域都具有非常重要的价值。由于合成孔径雷达具有卓越的性能以及广泛的军事用途,对合成孔径雷达干扰方法的研究也十分紧迫,该研究对国防技术现代化发展具有重大的意义。为了研究对合成孔径雷达的干扰方法,必须掌握合成孔径雷达的工作原理及其成像算法,从而为对合成孔径雷达干扰方法的研究提供平台,本论文就是围绕合成孔径雷达成像方法与对合成孔径雷达的干扰方法展开研究。论文主要涉及下面几个方面的研究内容:合成孔径雷达的距离向和方位向成像原理、条带式SAR与聚束式SAR的成像处理方法研究、合成孔径雷达的成像算法及其改进算法研究、对合成孔径雷达的干扰方法研究、对合成孔径雷达的干扰效果评估方法研究。主要工作概括如下:1.研究了合成孔径雷达的距离向成像原理和方位向成像原理。从距离向和方位向两个一维信号处理入手进行研究,为后面章节合成孔径雷达的二维成像方法研究打下基础。研究了距离向成像所涉及的处理方法,其中包括距离向匹配滤波重建处理方法和距离向解线频调(dechirp)处理方法,并比较了两者的异同点。针对不同的处理方法,研究了距离向信号处理的采样率选择问题,从而达到降低距离向采样率的目的。从距离向点扩展函数的角度出发,对距离向分辨率进行了分析。给出了距离向图像重建的步骤。研究了方位向成像所涉及的处理方法,其中包括方位向匹配滤波重建处理方法和方位向dechirp处理方法,研究表明方位向dechirp处理在聚束式SAR系统中是降低PRF的信号处理工具,也是SAR系统通过数字聚焦方法完成指定场景成像的信号处理工具。研究了不同条件下方位向信号处理的采样率选择问题,从而达到降低方位向采样率的目的。从方位向点扩展函数的角度出发,对方位向分辨率进行了分析。给出了方位向图像重建的步骤。2.针对条带式合成孔径雷达与聚束式合成孔径雷达的特点,研究了两者成像处理方法的区别与内在联系。研究了合成孔径雷达成像的空间频率插值算法,分析了该算法对于条带式SAR与聚束式SAR成像处理的相同点和不同点,在此基础上实现了条带式SAR与聚束式SAR成像算法的统一。在各个方面对条带式SAR与聚束式SAR进行了分析比较,其中包括频谱结构分析、分辨率分析、回波信号带宽及其采样率分析、聚束式SAR的方位向dechirp处理分析以及部分波束成像处理方法分析,并说明了各种处理方法对SAR成像处理的优缺点。提出了在斜视条件下将条带式SAR数据分块,进行聚束式处理的方法,并对聚束式成像区域参数的选择进行了分析,此方法一方面减小了信号处理的运算量,另一方面对单一模式的SAR提供了数据处理上的灵活性。3.提出了一种合成孔径雷达成像的改进算法—子孔径参考信号相位对齐算法,该算法可以增大合成孔径雷达的方位向成像范围。该算法的本质是将各个子孔径参考信号的相位调整为同相(也就是使相位对齐),使用相位对齐的参考信号对子孔径场景回波信号进行解调,进而构造新的聚焦窗函数进行SAR成像。理论分析表明,在相同的数据采样点条件下,相对于子孔径数字聚焦处理方法,参考信号相位对齐算法使得方位向成像范围明显增大。4.研究了几种合成孔径雷达的成像算法,其中包括距离徙动算法和Range stacking算法,对算法中所涉及到的关键处理方法进行了理论分析。从研究距离徙动算法入手,对合成孔径雷达成像中所涉及的dechirp处理技术进行了全面、细致的理论分析,其中包括距离向dechirp处理、方位向dechirp处理、二维dechirp处理中运动补偿到点和运动补偿到线的分析、距离去斜处理加剩余视频相位(RVP)校正的理论分析。比较了距离徙动算法与空间频率插值算法的异同点,在此基础上提出了空间频率插值算法的改进方法,即将空间频率插值算法的距离向压缩方式从快时间域匹配滤波处理替换为距离徙动算法中的距离向dechirp处理加RVP校正,该处理方法可以降低距离向的采样率,为超宽带雷达的数字信号处理带来很大的好处。5.针对合成孔径雷达具有相当高的信号处理增益的特点,提出了几种对合成孔径雷达的相干干扰方法,并对各种干扰方法所涉及到的关键参数进行了细致的理论分析。采用相干干扰方法可以利用SAR的全部或部分信号处理增益,其相对于传统的非相干干扰方法可以提高干扰功率的利用率。提出了针对合成孔径雷达采用数字图像合成(DIS)完成欺骗干扰的方法,通过理论分析确定了对SAR欺骗干扰信号的幅度调制量和相位调制量,并给出了采用DIS方法对SAR进行欺骗干扰的实现框图和步骤,该方法可以获得和SAR回波信号相同的处理增益。提出了对合成孔径雷达的移频干扰方法,其中包括对SAR的距离向移频干扰方法和方位向移频干扰方法,从而推广到对SAR的二维移频干扰方法,对其模型及其参数选择进行了理论分析。理论分析表明,对SAR的移频干扰方法可以获得SAR的部分处理增益。提出了对合成孔径雷达的调频预加重干扰方法,其中包括正弦调频预加重干扰方法、锯齿调频预加重干扰方法、噪声调频预加重干扰方法,对各种调频预加重干扰方法关键参数的选择进行了细致的理论分析,并提出了二维调频预加重干扰方法以及将调频预加重干扰与移频干扰相结合的二维干扰方法。理论分析表明,对合成孔径雷达的调频预加重干扰可以看作多个移频干扰的线性组合,因而可以获得SAR的部分处理增益。6.研究了对合成孔径雷达的干扰效果评估方法,由于合成孔径雷达是二维成像雷达,其探测目标是面目标,其信号处理所得结果是图像,对SAR的干扰效果评估是以雷达成像区域受到干扰的效果来评价的。研究了合成孔径雷达接收到的各种信号模型以及对合成孔径雷达阻塞干扰的判决准则,该准则是以干扰前SAR的杂波-噪声功率比与干扰后SAR的杂波-干扰功率比的变化为基础建立的。以对合成孔径雷达阻塞干扰的判决准则为基础,从战术应用角度出发,通过干扰机阻止雷达侦察信息的范围(即干扰区)来度量对SAR的阻塞干扰效果。利用等轮廓曲线图得到对SAR的方位向干扰范围,从而提出了对SAR分布式干扰布站的方法。从图像质量评估的角度研究了对合成孔径雷达阻塞式干扰和欺骗式干扰的干扰效果评估方法。更多还原

【Abstract】 Synthetic aperture radar is a kind of imaging radar with characteristics of all-weather, day/night and long range, which could provide high-resolution image. The advent of SAR expands the original concept of radar. It has the capability of imaging and recognizing the territorial targets, which is of great importance in either military or civilian fields. Since synthetic aperture radar has prominent performances and wide military applications, it is urgent to study jamming methods against SAR, the work is important to technical modernization of national defence.In order to study jamming methods against SAR, we should understand principle and imaging algorithms of synthetic aperture radar, which provide the foundation for study of jamming methods against SAR. Aim of the dissertation is to study imaging and jamming methods of SAR, which include following aspects: imaging principle of SAR in range and azimuth dimension, imaging processing of stripmap SAR and spotlight SAR, imaging algorithms and improved algorithms of SAR, jamming methods against SAR, evaluation of jamming effectiveness of SAR. Primary work of the dissertation is summarized as follows:1. The dissertation studies imaging principle of SAR in range and azimuth dimension, which is basis of two-dimensional SAR imaging methods. The processing methods concerned with range imaging are presented, which include matched filtering and dechirp processing in range dimension. The problem of choosing range sampling rate is studied in order to reduce the range sampling rate. From viewpoint of range point spread function, range resolution is analyzed. The steps of range imaging are given. The processing methods concerned with azimuth imaging are presented in detail, which include matched filtering and dechirp processing in azimuth dimension. Dechirp processing in azimuth dimension is a processing tool which could reduce PRF in spotlight SAR and digital spotlight the desired target area. The dissertation studies the problem of choosing azimuth sampling rate under different conditions in order to reduce the azimuth sampling rate. From viewpoint of azimuth point spread function, azimuth resolution is analyzed. The steps of azimuth imaging are given.2. The dissertation studies difference and relationship between stripmap SAR and spotlight SAR. Spatial frequency interpolation algorithm is discussed, which could adopted to either stripmap SAR or spotlight SAR. The difference on the algorithm between stripmap SAR and spotlight SAR is analyzed, based on which imaging algorithm of both stripmap SAR and spotlight SAR is unified. The dissertation compares stripmap SAR and spotlight SAR in various aspects, which include spectrum structure, bandwidth of echo, resolution, sampling rate, azimuth dechirp processing of spotlight SAR, imaging processing with data of partial beam. The dissertation brings forward a method which adopts spotlight processing of stripmap SAR data under squint condition and analyzes how to choose parameters of the spotlight imaging area. The method could decrease amount of computation and provide flexibility of data processing of SAR.3. The dissertation puts forward an improved imaging algorithm of SAR named as phase alignment algorithm of subaperture reference signal. The algorithm adjusts phases of respective subaperture reference signals in ordre to make them be in phase and adopts the inphase reference signal to demodulate subaperture echo signal of the target area, then constructs a new spotlighting window function for SAR imaging. Theoretical analysis shows that under condition of the same sample data, the improved algorithm could increase SAR scene area in azimuth dimension relative to subaperture digital spotlighting algorithm.4. The dissertation studies serval imaging algorithms of SAR, which include range migration algorithm (RMA) and range stacking algorithm. Key processing methods of the two algorithms are analyzed. Starting from analysis of RMA, the dissertation investigates dechirp processing of SAR imaging thoroughly, which includes range dechirp processing, azimuth dechirp processing, two-dimensional dechirp processing consisting of motion compensation to point and motion compensation to line, range deskew processing plus RVP calibration. The dissertation compares RMA with spatial frequency interpolation algorithm. Based on the theoretical analysis, the dissertation proposes an improved method which modifies spatial frequency interpolation algorithm, with substitution of range dechirp processing plus RVP calibration of RMA for fast-time matched filtering of spatial frequency interpolation algorithm. This method can reduce range sampling rate obviously, which brings great benefit to ultra-bandwidth radar signal processing.5. Since synthetic aperture radar has advantage of high signal processing gain, the dissertation proposes several coherent jamming methods against SAR, key parameters of which are analyzed. Coherent jamming methods could obtain whole or partial processing gain of SAR, which enhances efficiency of jamming power relative to classical incoherent jamming methods. The dissertation proposes a deception jamming method against SAR, which adopts digital image synthesis and obtains the same processing gain as echo of SAR. The quantities of phase and amplitude modulation of the deception jamming method are determined through theoretical analysis. Steps of the deception jamming method are given. The dissertation presents shift-frequency jamming methods against SAR, which include shift-frequency jamming method in range dimension, shift-frequency jamming method in azimuth dimension and two-dimensional shift-frequency jamming method. Model and parameters of the shift-frequency jamming method are developed theoretically. Theoretical analysis shows that the shift-frequency jamming method could obtain partial processing gain of SAR. The dissertation brings forward weighted frequency modulated jamming methods against SAR, which include weighted sine frequency modulated jamming method, weighted sawtooth frequency modulated jamming method and weighted noise frequency modulated jamming method. How to choose key parameters of weighted frequency modulated jamming methods is analyzed. The dissertation puts forward two-dimensional weighted frequency modulated jamming method and a method which combines weighted frequency modulated jamming and shift-frequency jamming in two dimensions in order to jam SAR in two-dimensional domain. Theoretical analysis shows that the weighted frequency modulated jamming against SAR could be regarded as linear combination of multiple shift-frequency jamming and could obtain partial processing gain of SAR.6. The dissertation studies evaluation of jamming effectiveness against SAR. Since SAR is a kind of two-dimensional imaging radar, target of which is extended and result of which is a image, it is necessary to evaluate jamming effectiveness against SAR based on the image. The dissertation discusses mathematical models of different received SAR signals and judging criterion of barrage jamming against SAR. The criterion is established on the basis of variation of ratio of clutter power to noise power and ratio of clutter power to jamming power. From the viewpiont of tactical application, the dissertation discusses a concept called jammed region, which could evaluate barrage jamming effectiveness against SAR. The dissertation proposes a method of distributed jamming system against SAR based on contour curve chart, which could measure jammed scope of SAR in azimuth dimension. From the viewpiont of image qulity evaluation, the dissertation studies evaluation of barrage jamming effectiveness and deception jamming effectiveness against SAR.更多还原