Land surface deformation parameter estimation using persistent scatterer interferometry approach in an underground metal mining environment

Persistent scatterer interferometry (PSI) is a major advancement in radar interferometry for detecting and monitoring land deformation. PSI is the most advanced class of differential interferometric synthetic aperture radar (DInSAR) techniques. The technique conquers the main drawbacks of the conventional DInSAR technique by identifying radar targets having stable backscattering characteristics in time. These targets are termed as persistent scatterers (PSs). The higher the number of PSs for a study area the higher the accuracy of the results will be, which is most common for deformation analysis in urban areas. However, for non-urban or highly de-correlated areas, PSs density collapses significantly, which needs to increase for optimal results. For this purpose, partially coherent/distributed scatterers (DSs) are being exploited in addition to the PSs. The field surface of this study is one of the copper-rich mining belts in India, which consists of two major underground metal mines. Scatterer characterziation of the field surface under study suggests that most of the scatterers are DSs and very few scatterers under the influence of the mining zone are PSs. In addition to this, a preliminary investigation of deformation characteristics of the field surface under study reveals that the spatial extent of deformation is small/localized along with slow and non-linear deformation. Keeping in view scatterer and deformation characteristics of the field surface under study, in this research paper, a Quasi-Persistent Scatterer based PSI approach has been applied using high-resolution TerraSAR-X interferometric data stack (10 images) to generate deformation time series and deformation velocity. Furthermore, results obtained from the applied PSI approach and ground-based observations (using GNSS) have shown good agreement with each other, in the order of ?5.20?mm/year (LOS) and ?5.38?mm/year (subsiding), respectively.     

High-resolution ISAR imaging of fast rotating targets based on pattern-coupled Bayesian strategy for multiple measurement vectors

Very high resolution inverse synthetic aperture radar (ISAR) imaging of fast rotating targets is a complicated task. There may be insufficient pulses or may introduce migration through range cells (MTRC) during the coherent processing interval (CPI) when we use the conventional range Doppler (RD) ISAR technique. With compressed sensing (CS) technique, we can achieve the high-resolution ISAR imaging of a target with limited number of pulses. Sparse representation based method can achieve the super resolution ISAR imaging of a target with a short CPI, during which the target rotates only a small angle and the range migration of the scatterers is small. However, traditional CS-based ISAR imaging method generally faced with the problem of basis mismatch, which may degrade the ISAR image. To achieve the high resolution ISAR imaging of fast rotating targets, this paper proposed a pattern-coupled sparse Bayesian learning method for multiple measurement vectors, i.e. the PC-MSBL algorithm. A multi-channel pattern-coupled hierarchical Gaussian prior is proposed to model the pattern dependencies among neighboring range cells and correct the MTRC problem. The expectation-maximization (EM) algorithm is used to infer the maximum a posterior (MAP) estimate of the hyperparameters. Simulation results validate the effectiveness and superiority of the proposed algorithm.     

EFPI-FBG复合光纤传感器高温大应变试验研究

由于缺乏航空发动机/燃气轮机服役环境下叶片温度、应变有效性检测的技术与装置，所以工作叶片的温度环境、载荷环境和应变分布等关键数据的缺失是故障检修工作中的最大困难之一。采用非本征型法布里-珀罗(Extrinsic Farby Perot Interferometric,EFPI)与光纤光栅(Fiber Bragg Grating,FBG)传感技术，研制了一种基于单模光纤的EFPI FBG复合光纤传感器及其解调设备。通过搭建高温拉伸试验平台，开展了基于DZ125材料试件的复合光纤传感器高温、大应变测量的性能测试。试验结果表明：复合光纤传感器的工作温度范围为26 ℃~1 100 ℃，温度测量精度不超过全量程的5%，分辨率为0.066 ℃；F-P传感器的应变测量范围为0~19 468 με，在1 100 ℃下的相对误差为1.96%，分辨率为0.053 με。     

基于图像对比度的舰船目标成像算法

针对舰船目标ISAR成像时舰船随机摆动对于成像质量的影响,提出了一种同时基于多普勒中心估计和图像对比度准则的最优成像时间段选择方法。该方法根据海舰船回波的实际数据,估计各个回波的多普勒中心频率,并根据多普勒中心曲线选取舰船目标的线性成像段。然后,通过采用图像对比度准则,对该线性段进行处理。相比已有的方法,本文的成像效果更好。该方法易于实现且运算量较低,适用于实时应用。仿真数据的处理结果验证了本文所提方法的有效性。     

基于混和时频分析方法的ISAR成像研究

采用了一种混合时频算法来克服传统时频算法ISAR成像时交叉项干扰问题,提高成像分辨率;提出了"数据分割-时频分析与采样-数据拼接"成像加速方法提高ISAR成像处理效率.应用强散射回波点目标某飞机模型做仿真实验.对比传统ISAR时频分析方法和本文方法成像表明:本方法成像质量高,关键细节清晰可见,基本消除了无交叉项干扰,时频分辨率高:成像加速算法较传统成像算法缩短了一半以上的成像处理时间,成像实时性得到了显著提升。     

基于ISAR技术的太赫兹目标RCS测量

对目标RCS的研究主要包括电磁计算与基于成像的测量方法.由于受到计算机内存与运行时间的限制,电磁计算方法难以在太赫兹波段得到广泛应用.在基于图像的测量中常使用逆合成孔径雷达成像技术.后向散射算法(BP)常用于目标的反射图的重建.由于BP算法不能在图像中反映太赫兹波段目标显著的角闪烁现象,因此,使用子孔径成像技术对太赫兹目标RCS进行测量,并进行了仿真验证所提出算法的有效性.     

基于分布式压缩感知的全极化雷达超分辨成像

基于分布式压缩感知理论,提出了一种全极化逆合成孔径雷达超分辨成像算法,联合各极化通道进行超分辨处理.首先,建立全极化信号模型及超分辨字典,利用各极化通道信号的联合稀疏性将全极化超分辨成像建模为最小L2,1范数的优化问题,运用一种快速算法求解该优化问题.由于利用联合稀疏约束,多极化通道联合成像相比于单通道成像能够获得更好的超分辨性能和噪声抑制能力,最终有效提高图像极化融合的效果.同时,采用快速傅里叶变换操作提升了算法的运算效率.基于backhoe的仿真数据实验验证了该算法的优越性.     

基于Michelson 干涉仪的光纤分布式扰动传感器

提出并研究了基于Michelson 干涉仪的应用于检测时变扰动的光纤分布式传感器。所提出的光纤传感器由两个Michelson 干涉仪和一个光纤延迟环组成。扰动作用在传感光纤上,引起传输光波相位的调制作用,可以通过该传感器进行检测并得到扰动的位置信息。通过光电探测器对干涉信号进行接收。对接收到的信号进行隔直,并通过求取峰峰值的方法对隔直后的信号进行预处理。通过希尔伯特变换、相位去包裹和三角函数运算可以提取出预处理信号中包含的相位信息。最后,通过频谱分析和相应的数学运算可以实现扰动的定位。在20 km 的监测距离内通过实验验证了传感器的可行性。所提出的光纤传感器具有实时性好、抗偏振性、低成本的独特优势。     

带有力反馈控制的三明治式微机械干涉加速度计

设计了一种静电力反馈控制的三明治式微机械干涉加速度计,加速度计由敏感芯片、半导体激光器、光电二极管以及相应的驱动电路和反馈控制电路组成.敏感芯片为玻璃-硅-玻璃3层结构,通过硅-玻璃键合体硅工艺制成.硅质量块由铝梁支撑,底部玻璃基片上有金属光栅和电极,通过在质量块和底部玻璃基片上的电极之间施加电压可以调节质量块与玻璃基片间的间隙.入射激光照射到敏感芯片上的光栅上,产生衍射光束,其光强随质量块与下玻璃的间距而变化.反馈控制电路通过测量衍射光强的变化来改变质量块与底电极之间的电压,使得质量块与底部玻璃基片的距离保持为入射光波长1/8的奇数倍,从而提高输出线性度,改善灵敏度,增大量程.     

基于波形预先设计和相位对消技术的步进频信号ISAR成像研究

针对步进频雷达系统,分析了目标匀加速运动对回波相位的调制效应,提出基于波形预先设计和相位对消技术组合的ISAR成像方法,该方法通过对脉冲重复时间的设计消除目标速度带来的相位高次项,并通过相位对消技术消除由目标加速度带来的相位高次项.因此对于匀加速运动的目标,算法不需要估计速度和加速度,减少了计算量.仿真试验演示了算法的...