合成孔径雷达平台角运动误差测试系统设计

分析了SAR(合成孔径雷达)天线指向误差对其成像质量的影响及某型机载SAR在商用载机成像飞行时的运动特性,在此基础上设计了针对此类机载SAR的天线稳定转动控制平台,并采用二维仿真转台模拟载机角运动,提出了对角运动误差的测试方案.借助现代虚拟仪器技术完成了对载机角运动误差的高性能测试.通过对所研制的实用样机系统合成孔径雷达天线转动模拟仿真平台的测试,证明采用该方案进行测量其角运动误差精度可达到3°‰.     

海面波合成孔径雷达成像仿真研究

目的：研究合成孔径雷达（SAR）对海面波成像的机理和海面波对雷波截面的调制机理。方法；选用速度聚束模型，采用不同参数仿真SAR对海面波成像的情况。结果：由于海面波的运动，使得SAR对海面波成像过程成为非线性，使SAR图像在方位向发生移位和模糊。结论：用这种仿真方法研究SAR对海面波成像是一种有效途径。     

混合采样机载MIMO雷达成像方法

针对传统合成孔径雷达(SAR)在进行机动目标成像时,极易造成SAR图像中出现散焦与模糊现象,本文通过融合MIMO雷达单次快拍与SAR合成孔径技术,提出了一种混合采样高分辨率机载MIMO雷达机动目标成像方法。该方法利用目标与载机的空间位置信息进行运动补偿,而无需估计目标多普勒信息,因此,能够有效避免传统SAR存在的机动目标多普勒参数估计难题。仿真实验证实了新方法实现机动目标聚焦成像的有效性。     

线性调频脉冲串制式合成孔径雷达实时成像算法和方案的设计和模拟

介绍了线性调频(LFM)脉冲串制式合成孔径雷达(SAR)提高距离向分辨率原理,并且提出线性调频SAR的信号处理算法和步骤,避免了为提高距离向分辨率而加大系统带宽的问题.通过模拟验证了算法的正确性,并分析了计算量.设计了相应的SAR实时成像处理器方案,满足了这种新体制SAR系统的大规模成像处理的要求.     

海面波合成孔径雷达成象仿真研究

目的研究合成孔径雷达(SAR)对海面波成象的机理和海面波对雷达截面的调制机理. 方法选用速度聚束模型, 采用不同参数仿真 SAR 对海面波成象的情况. 结果由于海面波的运动, 使得 SAR 对海面波成象过程成为非线性,使 SAR 图象在方位向发生移位和模糊. 结论用这种仿真方法研究 SAR 对海面波成象是一种有效途径.     

一种有效的机载合成孔径雷达动目标成像方法

为实现机载合成孔径雷达(Synthetic Aperture Radar,简称SAR)实际回波数据中的运动目标聚焦成像,本文在用前置滤波法检测出运动目标的基础上,提出了利用目标子图像匹配方法来估计动目标的方位向速度,得到相应的运动目标聚焦参考函数,然后对运动目标进行聚焦成像,并给出了利用该方法得到的运动目标聚焦图像．成像结果表明,目标子图像匹配方法对动目标成像是有效的,易于工程实现,有实际应用价值．     

合成孔径雷达多波速通道间相位误差研究

通过点目标成像方式,分析了合成孔径雷达（SAR）多波束通道间相位误差及其对合成孔径雷达成像性能的影响,给出了计算机仿真结果,指出各种通道间相位误差都将引起方位向压缩波形主瓣展宽、峰值下降,且方位向压缩波形主瓣两侧出现虚假目标;同时给出了在系统硬件方面以及成像处理中减小通道间相位误差的一些措施．     

提高分辨率的带宽外推SAR成像算法

分析了合成孔径雷达(SAR)的图像信号模型,阐述了应用数据外推方法提高分辨率的可行性.提出一种最小方差谱估计和最小加权范数约束结合的非参数类数据外推方法.该方法外推SAR相位历史域信号有效带宽可得到较好的成像效果.仿真和实测数据处理证明了此方法的有效性,并给出了定量比较与分析.     

基于GB-SAR的地面军事目标伪装性能检测及评估方法

为有效评估地面目标的伪装性能,提出了一种采用地基合成孔径雷达(Ground Based-Synthetic ApertureRadar,GB-SAR)模拟观测获取目标SAR信息的试验和伪装性能评估方法。该方法在分析伪装目标的SAR成像特性的基础上,采用地基机动平台上的SAR系统对地面伪装目标进行模拟卫星SAR观测几何的数据获取,在此基础上通过目标散射特性分析等实现伪装性能评估。首先分析了地基SAR系统模拟星载SAR侦察的必要性;其次,介绍了适用于模拟星载SAR观测的典型地基SAR系统组成。针对伪装性能评估,介绍了如何从目标特性的角度分析伪装效果的方法;并指出了该方法适用于多种雷达伪装设备的评估。     

基于分割区域的SAR图像配准方法研究

合成孔径雷达(Synthetic Aperture Radar,简称SAR)图像受到斑点噪声影响以及成像条件的变化,使得同一场景的两幅SAR图像之间存在很大差异,利用基于边缘特征或灰度信息进行SAR图像配准,难以达到预期效果.基于此,本文提出一种基于分割区域的SAR图像配准方法,该方法首先利用主动轮廓方法对去噪后的SA...     

Modeling of waves generated by a moving submerged body. Applications to underwater landslides

In this work, a boundary element model of an underwater landslide is developed. Careful gridding and time stepping techniques are demonstrated that produce highly accurate simulation results based on conservation of volume. A sensitivity analysis shows how to optimize simulation accuracy. The general techniques demonstrated herein are applicable to arbitrary moving submerged bodies.     

Effects of ocean waves on airborne lidar imaging

The effects of ocean waves on lidar imaging of submerged objects are investigated. Two significant consequences of wave focusing or defocusing are quantified: (a) intensification of near-surface backscatter in which the mean return is increased relative to that for a flat interface, and (b) spatial-temporal modulations of the backscattered return. For the former, mean returns can be as much as 50% larger than flat surface returns at shallow depth. For the latter, the strong modulations induced by wave motion present a dominant clutter field that significantly affects the imaging of shallow objects. Both effects are compensated at greater depths by beam spreading caused by multiple scattering, which diminishes the intensity of the wave focusing.     

Efficient Strip-Mode SAR Raw-Data Simulator of Extended Scenes Included Moving Targets Based on Reversion of Series

The Synthetic Aperture Radar (SAR) raw data generator is required to the evaluation of focusing algorithms, moving target analysis, and hardware design. The time-domain SAR simulator can generate the accurate raw data but it needs much time. The frequency-domain simulator not only increases the efficiency but also considers the trajectory deviations of the radar. In addition, the raw signal of the extended scene included static and moving targets can be generated by some frequency-domain simulators. However, the existing simulators concentrate on the raw signal simulation of the static extended scene and moving targets at uniform speed mostly. As for the issue, the two-dimensional signal spectrum of moving targets with constant acceleration can be derived accurately based on the geometric model of a side-looking SAR and reversion of series. And a frequency-domain algorithm for SAR echo signal simulation is presented based on the two-dimensional signal spectrum. The raw data generated with proposed method is verified by several simulation experiments. In addition to reveal the efficiency of the presented frequency-domain SAR scene simulator, the computational complexity of the proposed method is compared with the time-domain approach using the complex multiplication. Numerical results demonstrate that the present method can reduce the computational time significantly without accuracy loss while simulating SAR raw data.     

A fully nonlinear implicit model for wave interactions with submerged structures in forced or free motion

The purpose of this work is to develop advanced numerical tools for modeling two-way fully nonlinear interactions of ocean surface waves (irregular waves in the general situation) with submerged structures undergoing large amplitude motion, that could represent Wave Energy Converters (WECs). In our modeling approach, an existing two-dimensional Numerical Wave Tank (NWT), based on potential flow theory, is extended to include a submerged horizontal cylinder of arbitrary cross-section. The mathematical problem and related numerical solution are first introduced. Then, conservation of volume and conservation of energy are checked, respectively, in the case of a circular cylinder in a prescribed large amplitude motion and in the case of a circular cylinder in a free motion. Interactions between waves and a submerged circular cylinder computed by the model are then compared to mathematical solutions for two situations: a cylinder in prescribed motion and a freely moving cylinder.     

水下小目标合成孔径声呐层析成像技术研究

水下小目标精细成像对于正确识别水下目标具有重要意义。目前,多波束成像声呐和条带合成孔径声呐是获取水下小目标图像的主要手段。水下目标的判别主要利用了目标图像的亮点特征,即使是同一目标从不同方位观测时得到的结果也可能差异较大,这给快速识别确认目标带来了困难。为解决该问题,提出了利用圆周合成孔径声呐对水下小目标进行水声层析成像信号处理方法,提高了声呐的多角度融合观测能力。仿真及试验数据处理结果表明,合成孔径声呐层析成像方法能够获得目标外形轮廓精细特征,有利于水下小目标的正确识别。     

双球并联入水空化及运动特性实验研究

物体入水问题近年来受到广泛关注,但关于运动体并联入水的研究较少。相对于单运动体入水,多运动体并联入水在军事中也有很强的应用背景,例如水上多枚鱼雷空投、超空泡射弹齐射入水等,这种多层次饱和打击能够大幅提高对水下运动目标的毁伤效果。为了探索双运动体并联入水的流体动力特点,开展了不同横向间距下的双球同步入水实验,分析了入水后双空泡演化过程与运动特性。结果表明,并联入水后由于双球内侧流场和压力发生变化,水-汽-壁三相接触线倾斜在球体表面,且倾斜角度随双球间距增大而减小;双球的空泡形态和三相接触线具有良好的彼此对称性。当双球以较小的横向间距(≤2.5D)并联入水时,空泡尾部内侧壁面会发生融合,形成"臼齿形"空泡,且其溃灭首先发生在壁面融合处,溃灭尾迹交织呈云团形;当间距增加至3.5D时,空泡溃灭尾迹向内侧偏、交汇呈马蹄形;当间距进一步增加到5.5D和7.5D时,双球空泡尾迹相互干扰很弱,与单球空泡尾迹形态比较接近。当双球横向间距小于3.5D时空泡表面闭合诱导产生的水柱顶部发生分离并两侧抛洒,随着横向间距的不断增加,空泡发展受相邻运动体的影响逐渐减弱,但均呈现出良好的对称性,其长度、直径与溅起水花等现象都趋近于单球入水情况。     

Approach for single channel SAR ground moving target imaging and motion parameter estimation

In recent years, ground moving target imaging in synthetic aperture radar (SAR) has attracted the attention of many researchers all over the world. A novel approach is proposed for the ground moving target imaging and motion parameter estimation using single channel SAR. First, a second-order generalised keystone formatting method is used to compensate for the range curvature. Secondly, the estimated slope of the target echo's envelope is used for the range walk compensation. Thirdly, Doppler parameters of moving targets obtained via spectral analysis are used for the imaging and positioning of ground moving targets. Finally, motion parameters of moving targets can be estimated on the basis of the relationship between Doppler and motion parameters. Both numerical and experimental results are provided to demonstrate the performance of the proposed approach     

星载SAR对舰船高分辨成像研究

研究了星载SAR对舰船高分辨成像的难度和方法。在星载SAR舰船数据获取模型的基础上，着重分析了舰船航行以及船体在特定海情时三维转动对星载SAR成像的影响，研究了星载SAR舰船数据的ISAR成像方法，并给出成像算法流程，仿真结果验证了该方法的有效性。