机动目标ISAR成像关键技术研究

发布时间：2018-10-24 06:32

【摘要】：逆合成孔径雷达(Inverse Synthetic Aperture Radar,ISAR)能够对空间、空中和海面运动目标进行全天时、全天候成像,在国家安全和国民经济领域拥有重大的应用价值。但是,对机动目标回波进行成像处理时仍然存在一些问题。机动运动状态下,雷达回波信号运动补偿后,仍然包含加速度等引入的高阶相位项,导致重建二维图像在方位向发生散焦,成像质量下降。此外,步进频率体制下,雷达回波信号会受到机动目标运动径向速度和加速度影响,直接进行成像处理后重建一维距离像出现散焦和移位现象。针对上述问题,本文对机动运动目标的ISAR成像处理和一维距离像重建进行研究并提出解决方案。首先,本文介绍了ISAR成像的基本原理,包括ISAR转台成像模型和线性调频信号,并且概述了成像基本技术脉冲压缩和运动补偿的方法。另外,通过实验仿真飞机目标回波和RD成像算法,为后续的机动目标ISAR成像奠定了理论基础。其次,详细分析了强机动目标回波的特征,建立强机动目标立方相位信号(Cubic Phase Signal,CPS)模型。针对CPS中调频率和二次调频率导致的图像方位向散焦问题,提出相位差分-调频傅立叶变换算法。先估计出CPS的所有参数后重构目标回波信号,再运用RD算法进行成像,就可以获得高分辨率的ISAR像。MATLAB仿真验证本章算法能够获得较好的成像结果。然后,研究了目标机动运动对步进频率脉冲回波信号一维距离像的影响。对机动运动引入的加速度和速度如何影响距离向成像进行了详细分析,提出基于求和立方相位函数(Integrated Cubic Phase Function,ICPF)的参数估计方法,对目标运动参数进行精确估计。然后通过Dechirp技术完成运动补偿,经逆快速傅立叶变换后获取高分辨率的一维距离像。同时,对步进频率脉冲信号高分辨率成像进行了仿真,验证了该方法的有效性。最后,对本文全部工作进行总结,并对未来需要继续研究的问题进行了展望。
[Abstract]:Inverse synthetic Aperture Radar (Inverse Synthetic Aperture Radar,ISAR) has great application value in the field of national security and national economy. However, there are still some problems in imaging maneuvering target echo. In the state of maneuvering motion, after the radar echo signal motion compensation, it still contains the high-order phase term, such as acceleration, which leads to the defocusing of the reconstructed two-dimensional image in the azimuth direction and the degradation of the imaging quality. In addition, the radar echo signal will be affected by the radial velocity and acceleration of maneuvering target under the stepwise frequency system. In order to solve the above problems, the ISAR imaging processing and one dimensional range image reconstruction of maneuvering targets are studied and solutions are proposed. Firstly, this paper introduces the basic principle of ISAR imaging, including the imaging model of ISAR turntable and LFM signal, and summarizes the methods of pulse compression and motion compensation. In addition, the experimental simulation of aircraft target echo and RD imaging algorithm provides a theoretical basis for the subsequent maneuvering target ISAR imaging. Secondly, the echo characteristics of strong maneuvering target are analyzed in detail, and the cubic phase signal (Cubic Phase Signal,CPS model of strong maneuvering target is established. Aiming at the problem of azimuth defocusing caused by frequency modulation and quadratic frequency modulation in CPS, a phase difference divide-FM Fourier transform algorithm is proposed. First, all the parameters of CPS are estimated, then the target echo signal is reconstructed, then the high resolution ISAR image can be obtained by using the RD algorithm. The simulation results of MATLAB show that the algorithm can obtain better imaging results. Then, the influence of target maneuvering on one-dimensional range profile of step frequency pulse echo signal is studied. The influence of acceleration and velocity on range imaging is analyzed in detail. A parameter estimation method based on summation cubic phase function (Integrated Cubic Phase Function,ICPF) is proposed to estimate the target motion parameters accurately. Then the motion compensation is accomplished by Dechirp technique, and the high resolution range profile is obtained by inverse fast Fourier transform. At the same time, the high resolution imaging of step frequency pulse signal is simulated, and the effectiveness of the method is verified. Finally, the paper summarizes all the work and looks forward to the problems that need to be studied in the future.
【学位授予单位】：南京邮电大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN957.52

【参考文献】