【作者】 雷杰；

【导师】 保铮；

【作者基本信息】 西安电子科技大学 ， 信号与信息处理， 2005， 硕士

【摘要】 ISAR是一种高分辨小旋转角成像技术，在距离方向，它通过发射大带宽信号获得高分辨；在方位方向，高分辨通过目标相对转动时回波间的相干积累取得。近二十年来，ISAR成像理论和技术有了很大发展，并逐步应用于实际系统。本文对宽带信号的ISAR成像与检测问题展开研究和讨论。 在舰船目标的ISAR成像中，由于受非线性策动力和阻尼力的作用，舰船目标在偏转、侧摆、俯仰三个维度同时存在姿态变化，其变化规律含有类似于钟摆周期性运动的特点。针对这一特点，本文提出一种基于钟摆模型的舰船目标转动模型和成像算法。分析证实，单纯作周期运动的散射点会在高分辨回波各距离单元的相位历程中包含反映目标横向散射点分布情况的线性调频信号。在一些条件下利用线性调频分量成像可以获得较好的结果。在钟摆模型的基础上，利用二阶相位误差估计算法以及降阶算法可以补偿实际目标转动过程中因颠簸和不完全符合钟摆转动模型而引起的三阶以及更高阶相位项，从而同时得到舰船目标的二维频率图像和调频率图像。实测数据处理结果表明，针对舰船目标的ISAR成像，由于频率分量和调频率分量的互补作用，本文的成像方法优于仅利用频率分量成像的方法，从而提高了成像概率。 假目标干扰背景下导弹目标的分类和识别是导弹防御系统中的一个突出问题，利用逆合成孔径技术对其成像是实现这一目的的快捷而有效的途径之一。实现对目标群中特定目标ISAR成像的关键在于对其进行运动补偿，由于成像域里多个目标间存在干涉效应，无法直接应用参考点补偿法。本文将Keystone变换应用于假目标干扰背景下的导弹目标线性距离走动校正，改进了基本的算法，得出了适于假目标干扰背景下的导弹目标成像方法。 宽带信号广泛应用于现代雷达设备中，用于获取精细的距离分辨力，此时目标将在距离上连续占据多个分辨单元而成为扩展目标。由于弱散射点的存在，与窄带信号相比，常用的扩展目标能量径向积累检测器会有很大的性能损失。由于目标散射点的位置在相邻的数十个脉冲内基本保持不变，本文利用判决的漏警概率估计散射点的相对幅度，并通过数值计算讨论了加权对能量径向积累检测器检测性能的改善作用。更多还原

【Abstract】 ISAR imaging is a high-resolution radar imaging technique with small segment of viewing angle. The resolution in range is obtained by large bandwidth waveforms, and in cross-range by coherent integration of the return signals. ISAR theory and technique have seen great developments in the last two decades, and, it is gradually applied to practical systems. We set off our discussion and research work to the problem in wideband ISAR imaging and detection.In the process of ISAR imaging of a ship, which is driven by nonlinear forces from ocean waves, the swing exists in three dimensions. The principle of the dominant swing of a ship is similar to that of a pendulum. To deal with problems arise from ship ISAR imaging, method based on pendulum module is proposed. It is demonstrated that the phase history in each range bin of the high range resolution echoes from periodic moving scatter approximates to linear frequency modulation signal, which represents cross-range location. In some cases, better images can be obtained from linear frequency modulation components. Based on pendulum model, the three and higher order phase errors, which are caused by nonlinear phase history, can be compensated with rank two phase estimator and the improved rank one auto focus algorithms. Both the images from frequency components and linear frequency components can be obtained simultaneously by adopting the proposed method. Processing of real data demonstrated that the method presented in this dissertation is better than a traditional one because two complementary images can be obtained form complementary components and thus have a higher imaging probability but a traditional method can only extract one image form frequency component.Missile classification and identification with fake target interference is and essential problem in missile defense systems. Target imaging with ISAR technique is an efficient approach to this problem. The key of missile imaging with fake target interference lies in fact that the proper motion compensation must be applied to the desired target. Because of the interference effect between targets, compensation method based on reference point cannot be applied directly. In this dissertation, a method based on the improved keystone transform is proposed for dealing with the problem of linear range alignment elimination of missile target with fake target interference.Wideband signal is widely used in modern radar systems to obtain more fine range resolution. With wideband signal adopted, target scatters take up severaladjacent range resolution bins and become range extended target. Because of the present of weak scatters, the detector based on range energy accumulation has a poor performance. To eliminate drawbacks, weights should be given to range compressed echo according to relative scatter amplitude, which can be estimated form the detected probability because the locations of scatters stay unchanged within the adjacent tens of pulses. The benefit for range extended target detection with estimated weights has been discussed by numerical calculation.更多还原