宽带啁啾光纤光栅F-P腔磁场传感器研究

提出了一种结合反射光谱分析方法的全光纤微弱磁场传感器。利用两个啁啾光栅间隔一段距离构成一个全光纤的啁啾光栅F-P腔,将其粘贴在超磁致伸缩材料的表面构成一个磁换能器;采用条纹计数法对F-P腔的输出反射光谱进行解调,获得在外部磁场的作用下啁啾光栅F-P腔的腔长变化,从而实现对磁场的传感测量。实验结果表明:测量误差平均值为0. 43μT,方差为0. 3μT,系统的相位灵敏度为1. 62 rad/μT。提出的光纤微弱磁场传感器具有体积小、响应快、响应带宽大、可多点组网等优势,在未来微弱磁场的测量中有着巨大的应用价值。     

线双折射对光纤光栅磁场传感器性能影响的理论分析

本文介绍了基于偏振效应的光纤光栅磁场传感器的工作机理。利用光纤光栅的偏振效应测量磁场可以克服以前传统测量磁场使用磁致伸缩材料不适合测量瞬态磁场的缺点,而且在传感头的设计上能够更加灵活。在传感头设计中,由于光纤本身存在的线双折射会对测量结果带来影响,为了明确双折射对光纤光栅磁场性能的影响,提高测量系统的准确爱,文中利用琼斯矩阵对光纤固有线双折射对传感器的测量特性的影响进行了理论推导和仿真分析,分别对稳态磁场和瞬态磁场受双折射的影响进行了仿真分析,为基于偏振效应的光纤光栅磁场传感器下一步实验研究提供了理论参考。     

光纤水听器传感技术及应用

光纤水听器是在传统的水听器的基础上,从一个全新的光纤技术出发,实现传统的水声传感和声纳数据传输一体化,从而改善声纳系统的可靠性,并且降低其制造、使用和维护的总成本的新型水听器.文章简要介绍了光纤水听器的工作原理和结构,包括干涉型光纤水听器、强度型光纤水听器、光纤光栅水听器等三种.详细地对它们在国内外的发展以及应用方面进行了介绍.     

光纤干涉传感系统PTDC法相位检测研究

本文给出了Mach-Zehnder光纤干涉传感系统直流相位跟踪(PTDC)零差检测的理论分析和实验研究;描述、分析了作者设计建立的一套光纤干涉传感测量实验系统,在该系统上得到了1mrad的相位检测灵敏度;同时提供了系统的分析设计方法和框图。     

基于复合干涉原理的局部放电检测光纤传感器

针对基于传统干涉结构的局部放电检测光纤传感器存在参考光纤隔音处理难、不利于现场布设等问题,设计了Mach-Zehnder与Sagnac复合干涉结构的光纤传感器。本研究应用延迟光纤与直线型传感光纤结构解决了上述问题,采用3×3耦合器对光信号引入相移以增加系统的动态响应范围,并阐明了传感光纤以及延迟光纤长度对系统传感特性的影响规律。利用局部放电模拟装置进行性能测试的实验证明,所设计的局部放电检测光纤传感器具有良好的响应性能,测得局部放电信号的时域响应峰峰值为2.45 V,频率分布范围为10.62 kHz～57.73 kHz。研究表明该复合干涉结构可有效提升局部放电检测光纤传感器的检测性能,提高现场适应性。     

全光纤干涉振动信号测试系统的硬件解调系统的研究

本文介绍了一种应用于全光纤干涉振动传感系统的硬件信号相位解调系统。文中对全光纤干涉振动传感系统的信号解调原理进行了介绍和分析,对光电转换和放大过程中所造成的信号被消除直流分量进行了自动计算和补偿;设计并实现了解调光纤传感信号的硬件系统,经过测试硬件信号相位还原系统可以准确有效地还原出设计带宽内的信号,有效地消除了软件还原方法中由于引入量化噪声等导致对信号还原精度的影响。     

干涉型光纤传感器PTAC法相位检测研究

本文给出了光纤Math—Zehnder干涉传感系统交流相位跟踪(PTAC)零差检测的理论分析和实验研究；提出了PTAC相位检测法适宜的工作状态；描述并分析了作者设计，建立的一套完整的光纤Mach—Zehnder干涉仪及其PTAC相位检测实验系统．该系统得到了10^-4rad量级的相位检测灵敏度．     

光纤Bragg光栅在动态应变测量中的研究

为了将光纤光栅的传感特性应用于结构健康监测和高频应力作用下的材料力学性能测试中,对光纤光栅动态应变传感的测量进行了研究.设计了基于相位载波(PGC)零差法的非平衡Mach-Zender干涉解调系统,并对相位载波解调技术进行了分析.通过对比冲击实验和频谱分析,实验结果证明该检测方法有效可行,可以得到稳定的测量信号,系统在10 kHz的频率范围内有良好的频率响应.     

基于光纤自适应耦合和自调谐的光纤光栅传感系统设计

针对光纤光栅传感系统应用中面临的应变弱和可靠性不稳定等问题,研究并设计了一种基于自适应耦合切换和自调谐光纤光栅传感系统;主要从事首先,基于光纤光栅的波长边化特点和多耦合特性设计了自适应耦合功能器件,并依据波长交叉点特性建立了长-短周期切换算法,然后考虑了波长对工作电压和耦合周期的影响特点,设计了支持自调谐功能的光纤光栅传感器及其调谐算法,最后给出了具有自适应多耦合切换和自调谐功能的光纤光栅传感系统;主要从事实验表明,在检测精度、抗干涉能力和应变能力等方面,所提方案表现出了明显优势.     

迈克尔逊干涉型光纤水听器研究与实现

设计了对偏振衰落不敏感的迈克尔逊干涉型光纤水听器,系统通过使用直接调制光源的相位载波零差检测方式实现了光纤水听器相位载波(PGC)解调,并给出了实验测试结果。由2个水听器组成水听器阵进行了水池实验,结果显示:该干涉型光纤水听器有明显的指向性,具有一定的潜在实际应用前景。     

干涉型光纤微弱直流电场传感器的设计

主要研究了基于Michelson干涉仪的光纤微弱电场传感器的原理,设计并实现了PLZT非线性电致伸缩材料为敏感元件的"工"字型微弱直流电场传感及其探测系统,该系统能较好解决1/f噪声问题.实验结果表明,系统对被测电场具有非常好的线性响应.     

基于加权联合导向矢量模型的InSAR干涉相位估计

基于干涉图的传统干涉相位估计方法,当由于图像配准误差而导致的干涉图质量较差时,就难以恢复出准确的真实干涉相位.本文提出了一种基于加权联合导向矢量模型的InSAR干涉相位估计方法.该方法构造最优联合观测矢量和加权联合导向矢量,同时利用相邻像素的相干信息,并采用波束形成技术,因此具有自适应图像配准和降低相位噪声的功能,因而可以在SAR图像配准精度很差(可以允许达到一个分辨单元)的条件下准确地估计相应像素间的干涉相位.仿真及实测数据的处理结果证明了此方法的有效性.     

Joint interferometric calibration based on block adjustment for an airborne dual-antenna InSAR system

Mapping large areas using airborne dual-antenna interferometric synthetic aperture radar (InSAR) usually requires processing and mosaicking of different scenes from multiple strips. The overlapping areas of these multiple strips should have consistent elevation values. Due to the unstable attitude of the plane, the interferometric parameters usually vary for each scene during mapping. Therefore, interferometric calibration technology for high-precision height retrieval is required for the correction of the interferometric errors. The traditional interferometric calibration methods for a single scene usually use ground control points (GCPs) to estimate the interferometric parameters – this method cannot guarantee a consistent height in the area of overlap. Besides, GCPs are difficult to deploy over rough terrain, making it impossible to use traditional calibration methods. In this article, a joint interferometric calibration method based on the block adjustment theory used in photogrammetry is proposed for airborne dual-antenna InSAR. This method considers the accurate digital elevation model (DEM) height reconstruction model and can be applied with sparse GCPs. The principle of the proposed method is to make the best use of the GCPs within all the scenes and the tie points (TPs) between the adjacent scenes to establish an error relationship model. First, the weighting values of all GCPs and TPs based on their retrieval elevation error caused by the interferometric phase error and the position distribution difference are introduced in the proposed method. Next, the interferometric parameters are weighted to reduce the condition number of the normal equation. Then, an alternative approximation approach combined with the sparse matrix decomposition technique LDL^T is utilized to solve the normal equation, and the corrected interferometric parameters for each scene are obtained. High-precision joint interferometric calibration results for airborne InSAR systems are achieved by the proposed method and validated by experiment. Using the proposed method, the average mean error (AME) and root mean square error (RMSE) are below 0.6037 and 0.9176 m, respectively. Meanwhile, the maximum AME and RMSE of the reconstructed DEM height difference for the validation TPs in the overlapped area of the adjacent scenes are reduced from 1.2909 and 1.7245 m to 0.8864 and 1.2087 m, respectively.     

绕环天线的干涉ISAR测高算法

提出了两副雷达天线在平面内绕环时的干涉逆合成孔径雷达(Inverse synthetic aperture radar, ISAR)成像算法.现有的干涉ISAR成像研究通常忽略了天线几何位置对成像影响,将天线设置为仅在高度上有差别的两副垂直天线.针对这一情况,本文推导了当两副雷达天线不垂直时、特别是在平面内圆周绕环时的干涉ISAR测高算法.研究结果表明,干涉ISAR高程测量不仅与基线长度有关,还与散射点横距坐标有关,于是需要对散射点横距进行估计.仿真结果验证了在此情况下干涉ISAR测高公式的正确性,并进一步分析了天线基线与有效基线之间夹角的变化对测高精度的影响.经统计,目标高度平均测量误差低于3%,几乎达到原两副天线垂直时的测高精度.     

快速区域互相关InSAR图像配准方法

在分析复图像干涉相位对快速互相关算法配准精度影响的基础上,提出了一种快速区域互相关InSAR图像配准方法。该方法对图像的幅度谱进行区域相关操作,获得干涉相位空间角频率的粗估计,并对主图像进行干涉相位补偿。该算法通过上述步骤消除干涉相位变化对算法的影响实现了高精度配准。在仿真实验和实测实验中,通过与传统的快速区域互相关算法及最大频谱法进行对比,验证了本文算法的稳健性与有效性。     

Effects of residual motion compensation errors on the performance of airborne along-track interferometric SAR

Two approximations, center-beam approximation and reference digital elevation model (DEM) approximation, are used in synthetic aperture radar (SAR) motion compensation procedures. They usually introduce residual motion compensation errors for airborne single-antenna SAR imaging and SAR interferometry. In this paper, we investigate the effects of residual uncompensated motion errors, which are caused by the above two approximations, on the performance of airborne along-track interferometric SAR (ATI-SAR). The residual uncompensated errors caused by center-beam approximation in the absence and in the presence of elevation errors are derived, respectively. Airborne simulation parameters are used to verify the correctness of the analysis and to show the impacts of residual uncompensated errors on the interferometric phase errors for ATI-SAR. It is shown that the interferometric phase errors caused by the center-beam approximation with an accurate DEM could be neglected, while the interferometric phase errors caused by the center-beam approximation with an inaccurate DEM cannot be neglected when the elevation errors exceed a threshold. This research provides theoretical bases for the error source analysis and signal processing of airborne ATI-SAR.     

基于改进粒子群优化的无线传感器网络定位算法

无线电干涉定位系统获取的干涉距离是4个传感器节点间距离的线性组合值.针对以两个节点间距离作为输入的传统定位算法无法直接利用上述干涉距离进行定位的问题,提出一种基于改进粒子群优化的定位方法.利用干涉距离的实验数据,分析比较了遗传算法和改进粒子群优化在无线传感器网络节点定位问题中的性能.结果表明,基于改进粒子群优化的定位方法的平均耗费时间远远小于基于遗传算法的定位方法,具有更高的优化效率.     

The influence of input parameters on SAR interferometric processing and its implication on the calibration of SAR interferometric data

Synthetic Aperture Radar (SAR) interferometry is a field of rapid development. The processing of SAR interferometric data is complex and influenced, in particular, by the input parameters. A sensitivity study of these input parameters and issues relating to the calibration of SAR interferometric data is presented. The pulse repetition frequency has been identified as a critical parameter during the SAR interferometric processing which, in case of inconsistencies in the CEOS standard data format, leads to erroneous results.     

电波传播对L波段地球同步轨道圆迹SAR重轨干涉性能的影响

不同于常规星载SAR,L波段地球同步轨道圆迹SAR(GEOCSAR)轨道高度高、合成孔径时间长、观测面积大,对流层折射率和电离层电子含量的时空变化将严重影响GEOCSAR重轨干涉性能。基于大气介质时空变化及GEOCSAR干涉信号的特点,从对流层和电离层相位延迟误差、电离层水平变化引起的图像方位向偏移、对流层折射率周日变化和电离层时空随机起伏引起的方位向聚焦性能下降、以及法拉第旋转效应几个方面分析了对流层和电离层对GEOCSAR重轨干涉相干系数、干涉相位的影响,并进行了仿真实验验证。分析以及实验结果表明,对流层和电离层均会对GEOCSAR干涉性能造成不可忽略的影响,其中电离层的周日时间变化和电离层起伏会导致图像散焦,进而严重降低干涉相干性。     

Optimal estimation of interferometric phase for measuring surface deformation

In recent times, time-series interferometric synthetic aperture radar (InSAR) methods are developed to retrieve the deformation signal in non-urban areas from distributed scatterers (DS). Phase triangulation algorithm (PTA), an important step in these methods for filtering decorrelation noise from DS, aims at optimal estimation of the filtered wrapped interferometric phase values using InSAR data stack. The uniqueness of this research work lies in the incorporation of one such PTA only to provide an optimal set of wrapped interferometric phase values before phase unwrapping in the open source StaMPS processing environment. The proposed methodology, when adapted to measure surface deformation in Tehri reservoir rim region, Uttarakhand, India using Environmental Satellite (Envisat) C-band advanced synthetic aperture radar images, works efficiently and has enhanced the spatial coverage of measurement pixels compared to standalone PS-InSAR processing. It is also revealed from the one-dimension-line of sight velocity map that resulted velocity estimates are congruent with standalone PS-InSAR processing.