基于声光移频的激光侦测正交解调方法

针对激光侦测信号调制与传输特点,提出一种基于多普勒移频的激光侦测系统,研究声光多普勒移频效应理论,探讨相干光平衡探测与正交解调原理,从数值仿真和频域分析了系统抗噪性能及载频失配对信号恢复的影响,给出基于声光移频效应的相干平衡激光侦测的技术实现方法.实验结果表明,基于相干平衡探测与正交解调的激光侦测系统可有效抑制基底及过剩强度噪声对系统输出的影响,进一步提高接收信噪比,实现声波振动对界面产生微扰的非接触信号检测,为实际应用提供一种有效的技术途径.     

声光移频器对微多普勒效应探测的影响研究

为实现基于微多普勒效应的远距离目标探测和识别,研究了采用声光移频器的激光外差相干探测结构对目标微多普勒特征探测的影响。建立了声光移频器驱动功率与系统信噪比之间的数学模型,并进行了仿真计算,搭建了1550 nm激光外差/零差相干探测实验平台对所建模型进行了验证。研究结果表明:在移频器驱动电压限定范围内,驱动电压越高,对微多普勒效应探测的效果越好,得到的目标特征越明显,与理论分析一致。通过对比实验发现在同样条件下,外差探测得到的反映目标特征的时频分布曲线较零差的清晰,特征提取误差小,可读性更高,说明外差探测结构更有利于复杂的远距离目标探测。     

基于双声光移频器的外差式激光多普勒测振计

分析了单声光移频器构成的外差式激光多普勒测振计中声光移频器驱动信号的频率稳定性和信号功率对待测振动信号的影响.为了降低声光移频器驱动信号频率漂移的影响,提出双声光移频器构成的外差式激光多普勒测振计,并基于直接数字频率合成技术,以相位噪音低、初始相位可控的芯片AD9912为核心器件,完成了声光移频器驱动信号生成及处理模块的设计.开展了双声光移频器组成的外差式激光多普勒测振计的振动测量实验,结果表明,驱动信号生成装置可以驱动声光移频器正常工作,且测振计的本底噪音在0~10kHz频带范围内呈现平坦分布,0~1kHz频段内噪音得到明显抑制,较单声光移频器构成的外差式激光多普勒测振计有显著改善.     

基于双声光移频器的外差式激光多普勒测振计

分析了单声光移频器构成的外差式激光多普勒测振计中声光移频器驱动信号的频率稳定性和信号功率对待测振动信号的影响.为了降低声光移频器驱动信号频率漂移的影响,提出双声光移频器构成的外差式激光多普勒测振计,并基于直接数字频率合成技术,以相位噪音低、初始相位可控的芯片AD9912为核心器件,完成了声光移频器驱动信号生成及处理模块的设计.开展了双声光移频器组成的外差式激光多普勒测振计的振动测量实验,结果表明,驱动信号生成装置可以驱动声光移频器正常工作,且测振计的本底噪音在0~10kHz频带范围内呈现平坦分布,0~1kHz频段内噪音得到明显抑制,较单声光移频器构成的外差式激光多普勒测振计有显著改善.     

应用LiNbO_3声表面波驱动的全光纤声光频移器

介绍一种工作在10.7MHz的全光纤声光频移器.它由在LiNbO_3基片上制作的叉指电极换能器产生的声表面波驱动.当驱动电功率1.5W时,频移光转换效率达35％.     

法-珀干涉绝对距离测量中的声光移频器双通道配置方法

为在能量天平动圈位移测量中实现大范围纳米精度法-珀干涉绝对距离测量, 提出了声光移频器双通道配置, 实现了调谐范围为200 MHz的可调谐频差. 通过分析声光移频器调制带宽与衍射效率的平衡与入射光束聚焦透镜的关系, 确定透镜的最佳焦距范围; 利用零级光斑分布特点准确定位入射光束, 保证一级衍射光束质量. 声光移频器在调制带宽内的实验单通道和双通道峰值衍射效率分别为79.54%, 61.41%; 声光移频器双通道配置输出的一级衍射光束与入射本征光束的拍频范围为440-640 MHz, 是单通道调制带宽输出220-320 MHz的两倍, 信噪比好. 理论分析表明, 声光移频器双通道配置方法实现的可调谐频差可测量腔长变化范围约为53 mm的折叠法-珀腔.     

晶体与电极位置失配对声光移频器性能的影响研究

为了提高声光移频器的性能,对其内部声光晶体(AOC)和压电超声换能器(PZT)电极之间的位置失配特性进行研究,并深入分析AOC和PZT电极之间几类不同的几何装配错位关系.通过构造AOC与电极失配的三维有限元模型,在不同轴向装配错位的条件下对AOC中的超声波声场进行仿真分析.根据超声波的声场分布特性,可以发现几何装配错位...     

傅里叶望远镜中激光频移误差对成像质量影响的分析

傅里叶望远镜成像技术,综合了激光主动成像技术、光学合成孔径技术和相位闭合技术是一种新的高分辨率成像探测技术。激光频移的效果是影响傅里叶望远镜成像质量的重要因素,特别是使用大功率、宽光束和宽调制带宽激光的系统。构建了不同的误差模型,推导了频移误差在系统中的传递函数,利用仿真实验分析其对系统成像的影响,得到了对应的误差影响分析。结果表明,频移精度和稳定度严重影响到系统的成像效果,部分情况下含有误差的反演图像与理论反演图像的施特雷尔值已降到0.2,因此合理的设计和选择声光频移器是改善系统成像的一个关键因素。     

频移反馈Nd∶YLF激光软阈值实验与模拟计算

实验和模拟计算均表明：在无注入种子激光的频移反馈Ｎｄ∶ＹＬＦ激光系统中，不存在软阈值，而当注入种子激光时，出现软阈值特性，实验还发现：随着种子激光功率增大，软阈值变得更加明显。     

A simplified adaptive feedback active noise control system

In the adaptive feedback active noise control system based on the internal model control (IMC) structure, the reference signal is regenerated by synthesizing the error signal and the secondary signal filtered with the estimation of the secondary path, hence more computation load and extra programming are required. Motivated by the engineering truth that the primary noise cannot be completely cancelled in most practical active noise control applications and the error signal still contains some portions of the primary noise, a simplified adaptive feedback active noise control system is proposed in this paper, which adopts the error signal directly as the reference signal in an adaptive feedforward control system and utilizes the leaky filtered-x LMS algorithm to update the controller. The convergence properties of the proposed system are investigated and its advantages are discussed by comparing with other feedback control systems as well as the weakness. Finally, simulations and experiments are carried out to demonstrate the effectiveness of the proposed system.     

利用振幅调制器进行光电负反馈抑制激光强度噪声

采用振幅调制器作为抑制激光强度噪声的元件,首先对光电负反馈回路进行了简要的理论分析,然后利用该光电负反馈进行抑制激光二极管抽运全固化单频环形Nd:YVO4红外激光器强度噪声的实验。结果表明,在0－1MHz的低频段,强度噪声大幅度降低,最大降低约15dB。     

Intensity noise suppression of light field by optoelectronic feedback

An optoelectronic feedback loop intended to suppress intensity noise of a light field is introduced in this paper. A maximum intensity noise reduction of 10 dB is experimentally achieved between frequency of 0?140 kHz on a 1064 nm DPSS continuous wave single-frequency solid-state laser. After optimization and miniaturization, this system is expected to be widely used as a simple ?Noise-Eater?.     

控制强度对Bragg光学双稳系统混沌控制的影响

对Bragg光学双稳系统的混沌态提出位相延时反馈的控制方法 ,用数值方法研究了该系统的混沌态在控制强度调制下的动力学行为。结果表明 ,控制强度的取值不同可以使受控系统的状态呈现多种演化模式 ,调节控制强度值不断增加 ,能够有效地将受控系统稳定在所需的周期态和不动点上     

Controlling and synchronizing spatiotemporal chaos of the coupled Bragg acousto-optical bistable map system using nonlinear feedback

In this paper we present the control and synchronization of a coupled Bragg acousto-optic bistable map system using nonlinear feedback technology. This nonlinear feedback technology is useful to control a temporally chaotic system as well as a spatiotemporally chaotic system. It can be extended to synchronize the spatiotemporal chaos. It can work in a wide range of the controlled and synchronized signals, so it can decrease the sensitivity down to a noise level. The synchronization can be obtained by the analysis of the largest conditional Lyapunov exponent spectrum, and easily implemented in practical systems just by adjusting the coupled strength without any pre-knowledge of the dynamic system required.     

束晕-混沌的非线性反馈离散控制

 基于非线性控制方法,提出了一种特殊的非线性反馈函数, 即小波反馈函数,用于离散控制强流质子束的束晕 混沌。控制后质子束的束晕强度因子很快趋于零,束均方根半径、束横向平均发射度等都减至控制前的三分之一稍多, 证明该控制方法切实有效,在工业上具有实用价值。     

Passive and active interior noise control of box structures using the structural intensity method

This paper presents passive and active vibro-acoustic noise control methods for attenuating the interior noise level in box structures which can be an analogy of cabins of vehicle and aircraft. The structural intensity (SI) approach is adopted to identify the predominant vibration panels and interior noise sources for box structures. In the study, the finite element method is used to determine the structural vibration and structural intensity in the box surfaces. According to structural intensity vectors plot and structural intensity stream lines presentation, the possible effective control positions where the dampers may be attached and the active control forces may act to reduce vibration and interior noise, are identified. From the study, it can be demonstrated that the structural intensity approach and stream line presentation are possible methods for identifying the vibro-acoustic interior noise source and predominant panels which may be modified to reduce the interior noise level. The structural intensity methodology, passive and active noise control results can be extended to the further study of the vibration and interior noise control of actual cabins of vehicles and aircraft.     

束晕-混沌的非线性反馈离散控制

基于非线性控制方法,提出了一种特殊的非线性反馈函数, 即小波反馈函数,用于离散控制强流质子束的束晕 混沌。控制后质子束的束晕强度因子很快趋于零,束均方根半径、束横向平均发射度等都减至控制前的三分之一稍多, 证明该控制方法切实有效,在工业上具有实用价值。     

一类新混沌系统的线性状态反馈控制

研究了一类新混沌系统的控制问题.利用Routh-Hurwitz准则对受控系统进行了稳定性分析，结合线性状态反馈方法理论上严格证明了达到控制目标反馈系数的选择原则.数值研究证明了该方法能够有效地控制混沌系统到失稳的平衡点或周期解，同时控制效果在弱噪声干扰下具有很强的鲁棒性. 关键词： 新混沌系统 线性状态反馈控制 Routh-Hurwitz准则 噪声     

Generalised synchronisation of spatiotemporal chaos using feedback control method and phase compression

Coupled map lattices are taken as examples to study the synchronisation of spatiotemporal chaotic systems. First, a generalised synchronisation of two coupled map lattices is realised through selecting an appropriate feedback function and appropriate range of feedback parameter. Based on this method we use the phase compression method to extend the range of the parameter. So, we integrate the feedback control method with the phase compression method to implement the generalised synchronisation and obtain an exact range of feedback parameter. This technique is simple to implement in practice. Numerical simulations show the effectiveness and the feasibility of the proposed program.