基于等光频细分重采样的调频干涉测距方法

为了解决调频连续波(FMCW)激光器调制非线性导致的测量信号频谱展宽降低激光干涉测距精度的问题, 采用一种基于等光频细分重采样的调频干涉测距方法, 进行了理论分析和实验验证, 获得了双光路测距系统对不同位置目标信号等光频细分重采样后的波形数据, 并进行了频谱分析。结果表明, 通过等光频细分重采样的方法, 使用细分后的时钟信号点对距离大于辅助干涉光路光程差的目标测量信号进行重采样, 消除了激光器的调制非线性的影响, 并且避免了采样点数不足引起信号失真的问题; 在4.3m测量范围内, 等光频细分重采样测距系统与激光干涉仪相比最大残余误差不超过±18.46μm, 最大测量标准差为23.39μm; 该方法使用的辅助干涉光路光程差很短, 受环境的影响较小, 可以获得稳定的时钟信号, 并且可以减少双光路FMCW测距系统的体积与成本。该研究为长距离、高精度调频连续波测量提供了实用参考。     

面向智能调制识别的电磁信号灵巧诱骗方法

基于深度学习的调制识别技术以其在特征提取和识别性能方面的优势,在电磁频谱感知中逐渐得到融合应用。然而,由于智能频谱感知模型内在学习机制的脆弱性和局限性,通过在原始信号上添加难以感知的扰动,能够降低电磁信号调制识别系统的性能。本文针对智能电磁信号调制识别系统的脆弱性,开展了电磁信号诱骗方法研究。与传统的在信号上添加全局扰动不同,该方法通过优选原始电磁信号上的显著采样点,并在特定采样点上加入扰动,实现对电磁信号调制识别系统的灵巧诱骗。实验结果表明,该方法通过在原始信号上添加轻微的隐蔽扰动,在不影响接收机性能的前提下,即可使得智能调制识别系统产生机器幻觉,将对抗样本识别为指定的信号类型,定向扰乱电磁信号调制识别系统的识别结果,从而达到“隐真示假”的目的。      

平稳随机过程非均匀采样信号的数字谱研究

目前的随机信号分析多是基于作等时间间隔采样以描述信号特征,而实际应用中往往不能避免采样的非均匀性;传统的谱分析方法必然产生原理误差。本文引入平稳随机点过程的知识,建立了广义平稳随机信号的非均匀采样序列模型,推导了其数字频谱的一般公式,分析了具有典型分布函数的随机采样情况。     

新型多普勒成像激光雷达原理设计与仿真

采用相干多普勒测量手段获取目标面型变化信息具有明显的优势。基于激光多普勒效应,设计一套多普勒成像激光雷达实验系统,同时引入APFFT全相位测相处理思路对外差信号进行时频分析,抑制频谱泄露,减小噪声对测量结果的影响,获取高测量精度信号时频曲线。在MATLAB软件simulink交互式仿真集成环境中进行过程仿真,证明其可以实现对扫描空间高分辨率、高精度的成像。实验结果表明:该系统能够较好还原被测目标表面特性,为激光雷达实现对目标高分辨率与高灵敏度成像提出新的解决思路。     

基于相位拼接的调频连续波激光雷达跳模影响消除方法

为了消除激光跳模对调频连续波激光测距的影响,提出了一种基于重采样信号相位拼接的跳模影响消除方法.该方法利用重采样信号相位展开求导的结果来定位激光跳模发生的时间,并对重采样信号跳模处两端的峰值进行相位拼接来去除跳模段的重采样信号.通过对相位拼接后的重采样信号进行Chirp-Z变换可以得到不受激光跳模影响的目标距离谱.系统对光程约为21.16 m的延时光纤进行多次测量,实验效果证明此方法可以消除调频激光跳模对距离测量的影响,并实现了 12 μm的测距标准差.     

基于混合编程的高精度激光多普勒信号处理技术

针对激光多普勒信号中存在较大噪声干扰的实际情况,为了抑制这些噪声干扰,提高激光多普勒测速仪的测量精度,提出了对激光多普勒信号进行最小均方差(LMS)自适应滤波后作快速傅里叶变换(FFT),基于混合编程思想对所得到的频谱,先进行频谱细化,再进行频谱校正的信号处理方法,并对理想正弦信号和实测多普勒信号分别进行仿真计算和实验研究。仿真和实验结果表明：LMS自适应滤波技术可以有效抑制激光多普勒测量中的多频率噪声的干扰,此技术能够适应于很宽的信噪比范围,大大提高多普勒信号的信噪比;频谱细化技术可以提高激光多普勒信号的频谱分辨率,频谱校正技术可以准确地校正多普勒频率,使校正后的频率更加接近于真实值;信号处理精度比直接进行FFT提高2~3倍。     

基于随机采样法的光生混沌雷达信号周期性减弱研究

激光器产生混沌信号时,由于腔长原因使产生的信号具有周期性,若将该信号应用于雷达系统,易被识别与攻破。针对上述问题,文中提出采用随机采样法对原始混沌序列进行不等间隔随机采样,讨论分析了采样前后混沌的自相关和功率谱性能,结果显示采样后混沌信号自相关及功率谱的周期性均明显减弱并逐步消除。搭建基于光生混沌的调频雷达信号模型,理论推导分析了信号的频谱和模糊函数。结果表明,混沌自相关的旁瓣较原始混沌序列明显降低,功率谱也更加平坦,可获得sinc函数频谱和图钉状的模糊函数,该信号可以应用于雷达探测系统。     

光子辅助的射频信号频谱分析

射频光子技术利用光子技术的高带宽、低损耗和低功耗等优点,在电子战系统的高性能电磁信号处理方面发挥着重要作用。将射频光子技术引入到宽带接收系统的射频信号频谱分析中,重点介绍了3种光子辅助的射频信号频谱分析技术:基于光子辅助的射频瞬时单频点测量、压缩采样稀疏多频点测量以及信道化多频测量技术,并对其优缺点进行了分析对比。通过光子辅助的射频信号频谱分析技术可实现传统方法难以完成的宽带微波信号频率的处理与高精度测量。     

频谱泄漏对正弦相位调制干涉测量精度的影响

在正弦相位调制(SPM)干涉仪中,若调制频率或者采样频率发生变化将使干涉信号出现频谱泄漏,减小了谐波分量的幅值,在测量结果中引入了误差。对频谱泄漏的产生及其对测量精度的影响进行了理论分析,获得了频谱泄漏引入测量误差的计算方法。实验测得频率漂移量在-0.3~0.3Hz内,得到的频谱泄漏引入的误差为0.3~7.9nm,当超出这个范围时,频谱泄漏误差将迅速增长。实验结果与模拟分析结果一致。     

基于EMD算法的双外腔激光自混合微振动测量

基于激光自混合理论,提出了一种双外腔激光自混合干涉信号分离的方法,以实现两路微振动的同时测量。用EMD算法对不同频率的两路激光自混合信号进行分离。以原始信号和各IMF分量的互相关系数作为判断依据,选择出高频一路所需的IMF分量。根据两路自混合信号具有线性叠加的性质,原始信号减去高频一路信号即得低频一路信号。对分离出的每一路信号进行频谱分析,利用主频阶次判定法实现振幅重构。结果表明,仿真和实验信号均能有效被分离。     

基于小波变换和快速傅立叶变换的电网谐波分析

谐波分析是谐波治理和研究谐波问题的基础。文中介绍了一种将小波变换和快速傅立叶变换结合起来的谐波分析方法,给出了电能质量信号突变点的确定公式,并对三相全控桥式整流电路产生的谐波电流进行仿真分析,得出了采用这种方法能够分别检测出扰动信号的起止时刻,也能够分析各次谐波的幅值和相角的结论。     

一种基于重频恒定脉冲分选的反侦察技术

传统脉冲雷达为了提高改善因子,一般要求重频固定,即使是重频参差雷达也是在若干固定参数中变化,易于被侦察接收机识别出来,文中提出一种包含有用信号与扰乱信号的复杂脉冲串反侦察技术,脉间重复周期在一定范围内随机变化,使得侦察机几乎不能通过重频来正确分选。为了消除扰乱信号对自身有用信号处理的影响,二者之间采用正交波形,在此基础上,只需进行传统的雷达信号产生与处理即可。文中基于直方图进行了理论分析,并由此给出了简单可行的扰乱脉冲实现方法,通过仿真表明,具有良好的反侦察性能。     

位标器动平衡测试系统中相位测量的实现

提出了一种新的相位测量方法,该方法准确检测了从位标器陀螺仪输出的钟形光电脉冲信号峰值点的位置,并以其为时间基准点进行相位测量,同时判断被测两信号之间的时间间隔以及超前、滞后关系,同时针对在现场中的干扰因素,提出了相应的解决措施.试验证明该方法电路简单,测量速度快,精度高,可靠性好.     

Subspace-based signal analysis using singular value decomposition

A unified approach is presented to the related problems of recovering signal parameters from noisy observations and identifying linear system model parameters from observed input/output signals, both using singular value decomposition (SVD) techniques. Both known and new SVD-based identification methods are classified in a subspace-oriented scheme. The SVD of a matrix constructed from the observed signal data provides the key step in a robust discrimination between desired signals and disturbing signals in terms of signal and noise subspaces. The methods that are presented are distinguished by the way in which the subspaces are determined and how the signal or system model parameters are extracted from these subspaces. Typical examples, such as the direction-of-arrival problem and system identification from input/output measurements, are elaborated upon, and some extensions to time-varying systems are given     

具有抗扰动的全光纤干涉系统及应用

为了消除不良扰动对全光纤干涉系统的影响,提出了一种抵抗时变扰动的新方法。采用两路具有恒定相位差的干涉信号,经过简单的信号调理和数学运算,消除单路信号中有用信号与噪声的比值容易受到光路偏置相位角和调制相位差大小影响的问题,同时改善了信号质量。结果表明,该系统能有效消除扰动噪声,对耦合器的分光比无严格要求,更具实用性。     

Statistical properties of timing jitter due to data echo in digitalmodem receivers

Consideration is given to the influence of the noise and data sequences present in the received data signal on a nondecision-aided timing recovery scheme in digital modem receivers, It is known that white noise is not particularly disturbing for timing recovery, whereas data signals such as local echo (or residual echo) introduce a bias, called jitter, into the sampling recovered phase. It is shown that when the disturbing data signal has power P less than the power S of the useful signal (whose timing must be recovered), the jitter is sinusoidal with amplitude proportional to the ratio P/S. In the opposite situation, the bias increases indefinitely with time     

An improved method to estimate the impact on digital radio receiverperformance of radiated electromagnetic disturbances

Present emission standards are developed with respect to analog communication services. Therefore, knowledge of how relating present standards to the impact on digital radio receivers must be available for system design purposes. For a digital radio receiver, the bit error probability (BEP) is often used to show the impact of the receiver performance from a disturbing signal. A simple, previously proposed method relates present emission standards to the BEP for broad-band (BE) disturbance. This method has to be modified for use on narrow-band (NB) disturbance such as the NB spectral components from periodic signals. A method based on a modification of the earlier method is presented for this NB disturbance. This represents typical disturbance from information technology equipment working with periodic signals. The conclusion is that the method presented delivers a useful value of the BEP, which can be used when radiated emission requirements are to be chosen on electronic equipment co-located to digital radio systems     

Presence of residual echo and impulsive noise

A general analysis is presented for the jitter performance of a common type of symbol timing recovery (STR) system employed in a digital subscriber loop (DSL) transceiver for high-speed digital data transmission over twisted copper pair cables in the presence of residual echo and impulsive noise (IN). Numerical results, obtained for an experimental study of a timing recovery system, show that the presence of these disturbing signals can substantially degrade the STR performance     

Data compression and perceived quality

Discusses image compression and the block compression algorithm (BCA). The power spectrum, Bode diagram, or modulation transfer function (MTF) for the transmitted, reconstructed signal are the usual measures of system resolution. Any one of these resolution measures is often nearly identical for the ordinary signal and that for which the BCA is used. Yet, observers of that same transmitted signals perceive a much more profound difference than indicated by the resolution measure. At high compression, they say it is choppy and disturbing for the dynamic features. The author discusses how one can describe a measure of the effect of the BCA on the observation     

Symbol timing recovery in digital subscribers loops in the presenceof residual echo and crosstalk

A general analysis is presented for the jitter performance of a common symbol timing recovery (STR) system used in a digital subscriber loop (DSL) transceiver that uses adaptive echo cancellation for high-speed digital communications. Exact analytical expressions for the mean and variance of the timing wave and for the RMS phase jitter are derived as a function of the bandwidth of the postfilter for a given set of input parameters representing a particular digital subscriber loop and its noise environment, including such effects as residual echo and crosstalk. Numerical results show that the presence of these disturbing signals can substantially degrade the STR performance. The effect of the excess bandwidth factor of the prefilter on this degradation is investigated