【作者】 吴亮；

【导师】 凌永顺； 黎湘；

【作者基本信息】 国防科学技术大学 ， 信息与通信工程， 2012， 博士

【摘要】 逆合成孔径雷达（Inverse Synthetic Aperture Radar, ISAR）成像可以获得反映目标大小、形状、结构及姿态等细节信息的二维及三维高分辨雷达图像，是解决目标识别问题的一种重要技术手段。本文针对复杂运动目标ISAR成像存在的问题，深入研究了一维距离成像中运动估计、ISAR成像时间选取和横向定标方法以及目标二维和三维ISAR成像算法。第一章阐述了论文的研究背景及其意义，全面介绍了ISAR成像理论及系统的发展概况，然后结合传统ISAR成像技术，对复杂运动目标ISAR成像研究现状进行概述和分析，最后介绍了论文的研究工作。第二章讨论了ISAR成像的基本原理，提出了基于多项式相位变换和图像对比度的调频步进信号高速目标的运动参数估计方法，从而消除径向运动造成的距离-多普勒耦合对合成距离像的影响，该方法抗噪性能好且运算量小，具有相当的工程应用价值；进一步总结了传统ISAR成像基本技术流程；最后，分析了各种复杂运动对ISAR成像的影响。第三章研究了复杂运动目标ISAR成像时间选择和横向定标。首先，针对复杂运动目标ISAR成像时间选择问题，提出了基于时频谱能量积累的ISAR成像时间选择算法。该算法克服了信杂比或信噪比低，即特显点单元不明显的影响，且具有运算量较小的优点。通过选择最佳成像时间（包括成像时刻和相干积累时间），保证在较长的相干积累时间内复杂运动近似为匀速转动，从而利用RD或RID算法进行有效成像；其次，针对复杂运动目标ISAR成像横向定标问题，建立了近似匀加速转台目标模型，推导了决定目标横向尺寸的展缩因子及平移因子，提出了基于多特显点的匀加速旋转目标ISAR像横向定标方法。该方法利用目标上散射强度较大的多数特显点回波，具有良好的抗噪性能，同时拓展了匀速旋转目标ISAR像横向定标的应用，从而获得距离-瞬时多普勒ISAR像横向定标结果。第四章研究了高阶DCFT及其在三维旋转目标ISAR成像中的应用。首先，把二阶chirp的DCFT概念推广到高阶chirp的DCFT，并证明了三阶及四阶DCFT的基本性质，从而利用DCFT估计高阶chirp的信号参数，由于DCFT本质上是一种匹配变换，将不存在多分量信号的交叉项影响，且借助于快速傅立叶变换更利于其实际应用；其次，分析了三阶修正DCFT和DCFT之间的关系，提出了基于三阶修正DCFT的三维旋转目标ISAR成像算法。该算法消除了目标三维旋转在方位向回波中产生的三阶相位项对ISAR横向聚焦的影响，和已有的借助Clean技术的TC-DechirpClean和PHMT成像方法相比，不受散射点个数的影响，具有小的运算量更利于其实际应用。第五章研究了快速旋转及进动目标二维及三维ISAR成像技术。首先，利用快速旋转目标的旋转运动特性，提出了基于距离-慢时间匹配滤波和复值反投影的快速旋转目标三维成像算法。该算法在目标散射点存在遮挡、散射系数变化及低信噪比的复杂情况下仍然有效；其次，根据目标进动特性建立了中段目标时变散射点模型，根据中段目标姿态角变化和暗室静态测量数据获得ISAR回波动态仿真以及推导了中段目标轨道运动及进动和姿态角及有效转角的关系，进一步获得了进动目标二维ISAR成像的约束条件及相应的三个结论；最后，根据时变散射中心模型，推导了目标ISAR回波信号的解析表达式，提出基于距离-慢时间匹配滤波及Clean技术的中段进动目标三维ISAR成像算法，其中，距离-慢时间二维匹配滤波降低了多参数搜索维度，而Clean算法则避免散射点信号之间相互干扰。第六章针对具有旋转微动部件目标的二维ISAR成像问题，提出了基于解正弦调频RWT的旋转微动部件二维ISAR成像算法。该算法综合利用回波幅度和相位信息对旋转散射点二维ISAR成像具有较高精度；同时，对距离-慢时间域旋转微动部件回波进行频域滤波，从而滤除目标旋转微动部件回波分量。基于RWT方法，对于剩余回波进行刚体回波重建，并采用传统的RD算法进行成像。最终获得聚焦良好的旋转微动部件和刚体目标ISAR像。论文最后总结了本文的研究成果，并指出了下一步需要开展的工作。更多还原

【Abstract】 Inverse synthetic aperture radar is used to produce high resolution two-dimensional(2D) and three-dimensional (3D) images of non-cooperative targets, which can providethe valuable target information of shape, size, structure and attitude. At present, ISARimaging has been an important technique for target recognition. In order to resolve theproblems of ISAR imaging for targets with complex motion, several special researchesare made in this dissertation, including the motion estimation for one-dimensional rangeprofile, ISAR imaging time selection, cross-range scaling and algorithms of2D and3DISAR imaging.In chapter1, the research background and significance are introduced, and thedevelopment of theory and system for ISAR imaging is reviewed. Then the currenetsignal processing technology in ISAR imaging is summerized and analyzed in detail,followed by the introduction of main content in this dissertation.In chapter2, the basic principle of ISAR imaging is analyzed; In order to avoid theeffect of range-Doppler couple on synthetic range profile of stepped-frequency chirpsignal, a method to estimate motion parameters of high moving targets based on thepolynomial phase transform and image contrast is proposed, and the well anti-noise,efficient and real-time performance of which can be obtained; After summarizing thebasic procedure of conventional ISAR imaging techniques, the effect of complexmotion on ISAR imaging is analyzed theoretically.In chapter3, the imaging time selection and cross-range scaling for targets withcomplex motion are inverstigated. Firstly, such an algorithm of ISAR imaging timeselection based on energy accumulation of time-frequency spectrum is presented. Thisalgorithm avoids the effect of low signal noise ratio (SNR) or signal clutter ratio (SCR)and have low computation cost. By choosing the optimal imaging time (i.e. the initialand coherent processing time), the complex motion can be approximated to the uniformrotation, and ISAR image of targets will be obtained by range-Doppler (RD) orrange-instanteous-Doppler (RID) algorithms; Secondly, for cross-range scaling oftargets with complex motion, the model of non-uniformly rotating platform targets withconstant acceleration is established, the exentsional and translational factors associatedwith the azimuth size of target are deduced, and then the cross-range scaling for ISARimage of non-uniformly rotation targets with constant acceleration based on prominentscatters is proposed, which uses echoes of most of prominent scatters with highback-scattering coefficients to obtain well anti-noise performance and develops thecross-range scaling for uniform rotation targets to obtain the rescaled RID images.In chapter4, the research of discrete chirp Fourier transform (DCFT) forhigh-order chirps and its application to ISAR imaging for targets with3D rotating motion is carried out. Firstly, DCFT for high-order chirps is generalized from that forquadratic chirps and its properties are verified theoretically, then DCFT for cubic andquartic chirps can be used for high-order chirp rate estimation, which is free from thecross-term effects between different components of multi-component signals and can beimplemented via the fast Fourier transform (FFT). After analyzing the relation betweenthe original and modified DCFT for cubic chirps, ISAR imaging algorithm of targetswith3D rotating motion based on modified DCFT for cubic chirps is proposed, which isable to avoid the effect of the azimuth echo cubic chirps caused by3D rotation on ISARcross-range imaging, and does not associate with the number of scatters so as to haslower comutation cost than ISAR imaging methods of time-chirp distribution andDechirpClean (TC-DechirpClean) and product high-order matched-phase transform(PHMT).In chapter5,2D and3D ISAR imaging for targets with rapadily spinning motionand precession are inverstigated. By using the spinning characteristics of targets,3DISAR imaging algorithm for rapidly spinning targets based on range–slow-timematched-filter and complex-valued back projention is proposed firstily, which is stillavalid in the case of shadowing, varying backscattering coefficients and low SNR;According to the precession characteristics of mid-course targets, the time-varyingscattering center model (SCM) is established, and the static data measured in darkroomis combined with the dynamic attitude angle to synthesize the dynamic ISARrange-slow-time echoes, and then three constraints on the the radar and targetparameters and three corresponding conclusions for ISAR imaging are deduced, basedon the derivaration of the analytical expression of the attitude angle and effectiverotating angle associated with the trajectory motion and precession. In the end, fromtime-varying SCM, the analytical expression of ISAR echo signals is derived and3DISAR imaging algorithm for mid-course precession targets based on therange–slow-time matched-filter and Clean technique is presented, which reduces thenumber of parameter searching dimensions and avoid the interfere between twodifferent signal components via2D matched-filter and Clean technique, repectively.In chapter6, to resolve the problem of2D ISAR imaging of moving targets withrotating parts, the sine-frequency demodulation Radon Wigner-Vill transfom (RWT)based imaging algorithm for rotating parts is proposed, which can obtain high accuracyof ISAR imaging for rotating scatters by synthesizing the amplitude and phaseinformation of echoes; meanwhile, the echoes of rotating part scatters are removed bythe filtering in frequency domain, then based on RWT, the echo signals of rigid parts areconstructed from the remained echoes and used to produce2D ISAR image by RDalgorithm.Charpter7summerizes this dissertation and discusses the future work.更多还原