【作者】 秦玉亮；

【导师】 黎湘；

【作者基本信息】 国防科学技术大学 ， 信息与通信工程， 2008， 博士

【摘要】 随着现代武器对高精度和复杂背景下自动目标选择能力的需求,将SAR应用于导弹平台进行主动二维成像制导日益受到重视。与机载和星载SAR相比较,弹载SAR需要解决由其应用任务和平台的不同而产生的一些特殊问题,论文围绕曲线弹道SAR成像、摆动目标成像、弹体定位、目标定位以及抗干扰等弹载SAR制导技术走向应用亟需解决的关键问题开展研究。论文首先介绍了目前主要的弹载SAR制导系统,综述了弹载SAR制导技术的发展现状,分析了需要解决的问题:横向机动或俯冲引起的曲线航迹成像、恶劣海情下摆动舰船成像、基于单特征点单次观测的导弹定位、基于距离-多普勒的目标定位和抗干扰等。针对导弹横向规避或俯冲等机动引起的孔径非直线问题,首先分析了机动引入的相位误差,给出了曲线弹道补偿的定量条件;然后分析了横向规避和俯冲弹道条件下弹载SAR回波信号的特点,在合理近似的基础上,提出了基于距离-多普勒算法的横向规避和俯冲航迹弹载SAR成像方法,与直线孔径下的距离-多普勒算法相比,仅仅是修改了部分相位因子,没有因为孔径的非直线而增加成像算法的复杂度。针对恶劣海情下摆动舰船的成像问题,采用钟摆作为舰船的运动模型建立了摆动目标的回波信号模型;分析了摆动对回波信号调制的特点,得出了散射点三次相位误差的主要来源是相对速度在视线方向上的投影、中心频率偏移大的分量存在明显的三次相位项的结论;基于此结论提出了基于分数阶傅立叶变换和三次相位误差补偿的成像方法,先进行子孔径分数阶傅立叶变换检测各散射点并估计中心频率和调频率,然后进行全孔径分数阶傅立叶变换并构造带通滤波器分离各散射点信号,再估计三次相位误差进行补偿,在补偿后根据子孔径分数阶傅立叶变换对调频率的估计进行成像。针对导弹定位中可用图像少、数据率低和定位信息不足的问题,提出了高度信息辅助的基于单特征点单次距离-多普勒观测的导弹位置估计方法。采用发射点惯性坐标系作为导航坐标系推导了远程导弹位置求解的解析表达式,给出了详细的定位流程;在不需要考虑地球自转影响时以地心直角坐标系为导航坐标系推导了导弹位置求解的简化表达式;定量分析了高度测量对定位误差的影响,提出了通过加装一部天线作为测高通道的INS/双天线SAR组合导弹定位思路,通过估计弹下点高程提高了导弹定位精度。针对利用距离-多普勒估计弹目相对位置的问题,分析了不同弹道下弹目相对位置的可观测性,得出了要估计弹目三维相对位置导弹必须进行不“瞄准”目标机动的结论,分别研究了利用两次观测和利用观测序列的弹目相对位置估计方法,通过计算弹目相对位置估计的克拉美-罗下限分析了观测时间长度、初始弹目距离、导弹沿航向速度、垂直航向速度、沿航向加速度和垂直航向加速度对估计精度的影响,提出了INS速度输出存在偏差时的估计方法,分析了导弹匀速飞行时对视线角和视线转率的可观测性,提出了将DBS二维寻的制导和传统的单脉冲前视跟踪进行复合完成全程末制导的寻的制导技术,既利用了DBS对目标的检测和识别能力,又降低了末段对导弹制导控制系统的要求。针对SAR导引头抗干扰问题,提出了利用被动导引头辐射源参数测量能力和INS对成像区域“锁定”能力的对抗有源欺骗干扰和场景散射干扰方法;针对INS/被动微波/SAR复合导引头的交接班问题,通过定量描述成功交接班需要满足的条件建立了交接班成功概率的数学模型,并给出了交接班参数的求解方法。最后,对论文工作和研究方向的发展趋势、应用前景进行了总结,指出了需要进一步研究和解决的问题。更多还原

【Abstract】 More and more importance is attached to the 2-D imaging guidance with missile-borne synthetic aperture radar (SAR), in order to enable modern weapons to obtain high precision and target selection capability in the complex environment. Missile-borne SAR, compared with air-borne and space-borne SAR, is faced with a few problems induced by its specific application and platform. The dissertation focuses on SAR imaging with non-linear aperture, imaging for swinging targets, missile geo-location, target location, SAR anti-jamming, and other key issues encountered in the application of SAR guidance.Current typical missile-borne SAR systems and the state of the art of missile-borne SAR guidance are first introduced. Then we present a few topics such as non-linear aperture SAR induced by its transversal or vertical motion components, missile geo-location based on a single prominent point and a single measurement, range-Doppler based target location, and the anti-jamming.For the non-linear aperture problem, the maneuver induced phase error the compensation condition for non-linear aperture are first analyzed, followed by the analysis of the characteristics of non-linear missile-borne SAR returns. A range-Doppler processing for missile-borne SAR maneuvering transversally and vertically, respectively, is presented with rational approximation performed, in which only a few phase factors are modified and no additional computation load is brought compared to the range-Doppler algorithm for the linear aperture.For the SAR imaging under atrocious sea conditions, the pendulum model is employed to model the echo of swinging targets. The characteristics of echo induced by the swinging are analyzed, with the conclusion that cubic phase error results mainly from the radial velocity, and is remarkable for large Doppler centroid. Thus an imaging algorithm is proposed based on fractal Fourier transform (FrFT) and cubic phase error compensation. Specifically, FrFT with sub-aperture data is performed for the detection and estimation of the Doppler rate and Doppler centroid for the scatters. In what follows, FrFT with full-aperture data is carried out and bandpass filters are designed to separate the echoes of different scatters. Cubic phase error is then compensated while the separated target is focused using its Doppler rate estimated by FrFT.For the problems of few applicable images, low dada rate, and insufficient information for location, a missile geo-location method is presented, which utilizes additional height data and a single measurement for range-Doppler of a single scatter. The close form of the missile position and the detailed location flowchart are given in the inertial launching-point coordinate frame. Simplified expressions for missile positions are derived, with the earth centered (second) equator frame as the navigation frame, when earth rotation induced effects are disregarded. Furthermore, effects of missile height measurements on the location are also quantificationally analyzed. In the end, an INS/dual-aperture-SAR combined geo-location method is presented, which requires an additional antenna. Missile geo-location precision is improved via the altitude estimation for the ground point under the missile.For the estimation of the missile-target relative position using range-Doppler information, we analyze the observability of the relative position for different trajectories, concluding that the missile must have the acceleration component not‘aimming at target’to obtain the 3-D relative position of the target. Additionally, the relative position estimation methods, using two measurements and measurement series, respectively, are presented. The computation of Crammer-Rao bound gives the effects on the relative position estimation induced by the series length, the initial missile-target range, the cross-range and radial velocity of the missile, and the cross-range and radial acceleration of the missile, respectively. The estimation method is also presented with INS error into account. The observability of the aspect angles and their rates are analyzed when the missile flies a linear path with constant velocity. Finally, a new homing guidance technique is proposed which combines (Doppler Beam Sharpening) DBS guidance and monopulse tracking in the terminal course. The technique would utilize DBS’s detection and recognition capabilities, and reduce the requirement for the guidance system.For the anti-jamming of SAR seekers, the techniques to anti deceptive-jamming and anti scattering-wave-jamming are presented, which employ the measurability of passive seekers for emitter parameters and the‘locking on’ability of (Inertial Navigation System) INS for imaged scenes. For the handover encountered by the INS/passive radar/SAR seeker, additionally, the model for successful handover is established by quantificationally representing the required constraints for successful handover, and the method for finding handover parameters is also discussed.Finally, related work and its developing trend as well as potential applications are summarized, while problems to be resolved in further are also given in the end.更多还原