【作者】 彭岁阳；

【导师】 沈振康；

【作者基本信息】 国防科学技术大学 ， 信息与通信工程， 2011， 博士

【摘要】 新一代精确制导武器不仅要求能快速突防并精确识别和打击高价值军事目标,还必须具备全天候、全天时和远距离作战能力。因此,将合成孔径雷达应用于弹载平台以进行二维成像制导的模式日益受到重视。与机载和星载平台相比较,弹载平台具备高速度、大斜视和非匀直的特性,弹载SAR需解决一系列关键技术问题,主要包括大斜视角SAR成像方法和非匀直弹道SAR成像方法等。同时,弹载新体制SAR也是未来精确制导武器发展的重要内容,其中合成带宽SAR体制和双基地SAR体制是最具前途的发展方向。一方面,需要解决弹载SAR中的普遍性关键技术;另一方面,需要研究新体制SAR的特殊性关键问题。针对上述两个方面的四个具体问题,本文围绕弹载SAR成像技术开展了以下研究工作:1、研究了弹载大斜视角SAR成像方法。首先分析了瞬时斜距方程与二维频谱的泰勒展开近似公式,从中得到耦合相位校正的关系,并由此导出了弹载条件下的Range Doppler算法和Chirp Scaling算法。然后,提出了基于时域距离走动校正的CS算法。并为适应更大斜视角下的成像,提出了冗余设计的策略,并对该算法作了三次距离偏移相位校正的改进。最后,为获取更精确的成像参数,改进了基于分数阶傅里叶变换的参数估计方法,并利用仿真实验验证了其有效性。2、研究了弹载非匀直弹道SAR成像方法。首先通过分析非匀速直线运动弹道,建立了距离向和方位向的速度分解模型。阐述了从非均匀数据重构虚拟均匀数据的角度来解决变速直线运动SAR成像的原理,从这一思想出发,研究了弹载平台变速直线运动时基于内插阵列变换SAR成像方法。阐述了将变速运动等间隔时间采样的回波数据等效为匀速运动中非等间隔时间采样数据的原理,并由此导出了基于非均匀傅里叶变换的变速直线运动SAR算法。其次分析了俯冲向运动和横向规避运动在距离向的运动偏移方程,得出了其运动补偿函数。构建了非匀速直线运动SAR成像的方案——距离向进行运动补偿,方位向采用非均匀方法处理。然后,考虑到工程实践中测量误差的因素,阐述了基于弹道拟合方法获取弹道参数的原理,并通过仿真实验验证了弹道拟合方法和非匀直SAR方案的有效性。最后,讨论了末制导寻的阶段基于PFA算法的聚束SAR成像方法。3、研究了基于合成带宽技术的成像方法。首先,提出了基于多频段子脉冲信号合成带宽技术的SAR成像方法。为实现不同参数条件下的合成带宽,构建了合成信号的非均匀采样模型,并通过SINC插值完成信号重建。讨论了带宽合成技术在成像前处理和后处理的问题,认为前处理方式适合各子脉冲间参数不同的情况,并给出了重新处理后的参数和成像流程。然后,研究了末制导跟踪段高重频随机频率步进雷达成像的方法,解决了高重频条件下的频率匹配和运动补偿问题。提出了利用相邻良好距离像间具有强相关系数的特性判定回波是否正确混频的方法,并设计了基于收缩式频率匹配搜索策略的算法流程。4、研究了弹载双基地SAR成像方法。首先从弹载平台运动特点和作战样式的可适应性出发,讨论双基地SAR各种组合模式和几何构形在弹载平台应用的可行性,并研究平飞、一基固定一基飞行和双基斜飞等几何场景下的双基地SAR成像算法。重点构建了斜飞双基地SAR的理论模型,分析了其中存在的距离向空变误差,并为此设计了一阶近似法和模型近似法两种运动补偿的的方法。然后深入分析了收发平台非匀速平飞模式下的非同步双基地SAR成像问题。该方法将非匀速平飞双基地模型等效成单基地变速运动模型,并采用非均匀傅立叶变换处理变速运动引起的非均匀采样的问题。最后概括了本文的研究工作,对课题研究方向的发展趋势、应用前景作了总结与展望,并指出了需要进一步研究和解决的问题。更多还原

【Abstract】 New generation of precision guided weapons not only demanded to identify and destroy the high-value military targets quickly and accurately, but also demanded to work in all-weather, all-time and long-range conditions. Therefore, the pattern that synthetic aperture radar used in missile platform for two-dimensional imaging guidance has received increasing attention. Compared with airborne and space-borne platforms, missile-borne platforms have the characteristics of high-speed, high squint and non-uniform straight. Missile-borne SAR needs to resolve a series of key technical issues, including mainly high squint SAR imaging methods and non-uniform direct trajectory SAR Imaging methods. Meanwhile, the new missile-borne SAR systems are also an important part of the future development of precision guided weapons, among those, synthetic bandwidth SAR system and the biostatic SAR system are the most promising directions. On the one hand, universality of the key technologies on missile-borne SAR need to be resolved , on the other hand, particularity of the key issues on new SAR system need to be studied. In response to these the four specific issues of two aspects, the following researches focusing on Missile-borne SAR imaging technology are carried out in this paper.1. High squint missile-borne SAR imaging methods are studied. At first, taylor approximation formulas of instantaneous slant range equation and two-dimensional spectrum are analyzed. And the relationship of the coupling phase correction is obtained. From this, Range Doppler algorithm and Chirp Scaling algorithm on missile-borne SAR are derived. Then, The Chirp Scaling algorithm based on range walk correction in time domain is presented. To adapt for higher squint imaging, redundant design strategies are proposed, and the algorithm with third-order phase correction from the offset is improved. At last, parameter estimation method based on fractional fourier transform is improved to obtain the more accurate imaging parameters, and the simulation experiments show its effectiveness.2. Missile borne SAR imaging method of non-uniform direct trajectory is studied. At first, through analysis of non-uniform linear trajectory, the velocity decomposition model in range and azimuth direction is constructed. The principle of restructure method from non-uniform sampling data to virtual uniform sampling data to resolve the SAR imaging with variable motion is expounded. And proceeding from this idea, missile-borne SAR imaging for variable motion based on interpolated array transformation is studied. The principle of equivalent method from the uniform sampling data with variable motion to the non-uniform sampling data with uniform motion is expounded, and from this, the SAR imaging for variable motion based on non-uniform discrete fourier transform is studied. Second, Movement offset equations in range direction with diving motion and yaw motion is analyzed, and the motion compensation function is obtained. Non-uniform motion SAR imaging program is constructed—motion compensation in range direction and non-uniform treatment in azimuth direction. Then, Taking into account the measurement error factors in engineering practice, the method for ballistic parameters method based on trajectory fitting is expounded, and simulation results verify the effectiveness of the method for trajectory fitting and the SAR imaging program for non-uniform linear motion. At last, the spotlight SAR imaging method based on PFA algorithm in the stage of homing terminal guidance is discussed.3. The imaging method based on synthetic bandwidth technology is studied. At first, the SAR imaging method with synthetic bandwidth technology based on multi-band sub-pulse signal is presented. To resolve the synthetic bandwidth under different parameters, synthesized signal model of non-uniform sampling are constructed, and the SINC interpolation is used to complete the signal reconstruction. The problem about bandwidth synthesis processing before and after imaging is discussed. Pre-treatment is considered to suit for the circumstances under sub-pulse of different parameters, and the re-treatment parameters and imaging process are proposed. Then, the imaging method of random stepped frequency radar in the terminal guidance tracking segment is studied, moreover, the problems about frequency matching and motion compensation are resolved under the high repetition frequency condition. The determination method whether the echo is mixed correctly is presented, which uses the properties that the good adjacent range profiles have strong coefficient correlation, and the Algorithm process based on contraction-type frequency matching search strategy is designed.4. The missile-borne bistatic SAR method is studied. At first, starting from the use of motion feature and combat style of missile platform, the feasibility of various bistatic SAR combinations of patterns and geometrical on missile platform is discussed, and the imaging algorithm on geometric scenes of parallel mode, one fixed platform mode, and slanting flight mode is studied. Slanting flight bistatic SAR model is especially built up, the air variable error in the range direction is analyzed, and the motion compensation methods of first order approximation method and the model approximation are designed. An equivalent method from asynchronous bistatic model to monostatic variable velocity motion model is proposed, and with the non-uniform discrete Fourier transform, it resolves the non-uniform sample problems raised by variable velocity motion.Finally, the research is summarized in this paper. The summary and outlook about development tendency and application prospects in the subject research direction are given, and the problems about further study and solution are pointed out.更多还原