全数字PGC解调的载波相位超前技术

分析相位载波(PGC)解调中载波相位延迟产生的影响,表明载波相位延迟引起解调输出幅值衰减,严重时导致解调输出恒为零.提出采用载波相位超前技术消除其不利影响.在全数字PGC 解调系统中,采用余弦查找表(LUT)方式生成载波数字波形,通过在LUT 的地址输入端引入固定偏置,生成相位超前的载波,补偿解调系统中固有的延迟,达到消除不利影响的目的.固定偏置可以通过对解调系统进行分析和测试获得.实验结果表明,载波相位超前技术是有效的.     

基于STFT的振动信号解调方法及其在轴承故障检测中的应用

从信号滤波角度,对基于STFT的振动信号解调方法的原理和影响其解调性能的各种因素进行了严格的理论分析,指出该解调方法实质是基于复解析带通滤波的Hilbert变换解调法.严格证明了在利用Hilbert变换进行包络解调分析时,只要带通滤波器通带范围包括调制信号的部分频率成分,就可解调出被调制信号的周期成分.为了避免对所有的解调信号序列进行包络谱分析,提出按峭度值最大化准则选择一组含有丰富故障信息的解调信号序列进行包络幅值谱分析.基于以上讨论,给出了实用的基于STFT的振动信号解调算法.为了验证提出的解调算法的有效性,用该算法对仿真和实际轴承故障信号进行了解调分析,分析结果表明,利用该算法能有效地检测轴承故障.     

The detection of an external acoustic impact on an optical fiber using a scattered-light interferometer

The results of a study of a scattered-light interferometer for detecting external acoustic impacts on optical fiber are presented. A method of scattered field demodulation using the phase diversity technique is proposed. The demodulated signal is shown to contain regions of fading, the causes of which are analyzed.     

A novel differential synchronous demodulator for AC signals

We describe a new analog differential synchronous demodulator for AC signals where (i) the signal is synchronously demodulated using the floating-capacitor technique after being amplified, if necessary, by an AC amplifier with differential input and differential output, thus yielding a very high CMRR; and (ii) the differential-to-single-ended signal conversion is performed after demodulation, that is, on a low-frequency signal that can be amplified by low-cost, high-performance circuits. The possible signal-to-noise ratio degradation because of synchronous sampling is prevented by using bandpass differential filters     

采用包络检波去除SISAR直达波干扰的新方法

为了去除直达波干扰，从强的直达波干扰背景中有效提取SISAR侧影成像的目标全息信号，提出了对接收的含有目标全息信号和强直达波的混合信号直接进行包络检波，然后通过对检波后的输出进行时域的正交分解，恢复目标的全息信号的新方法．仿真结果验证了理论分析的正确性。     

广义解调时频分析方法在调制信号处理中的应用

介绍了一种新的信号处理方法-基于广义解调的时频分析方法,并将这种方法应用于调制信号的处理。广义解调时频分析方法采用广义解调将时频分布是曲线的信号变换为时频分布是平行于时间坐标轴的直线的信号,然后采用最大重叠离散小波包变换（Maximal overlap discrete wavelet packet transform,简称MODWPT）对广义解调后的信号进行分解,得到若干个瞬时频率和瞬时幅值都具有物理意义的单分量信号,再对各个单分量信号进行逆广义解调,进一步求出瞬时频率和瞬时幅值,从而得到原始信号完整的时频分布。采用广义解调时频分析方法对调幅-调频信号进行了分析,结果表明该方法能有效地提取调幅-调频信号的调制信息。     

基于谐波小波变换的共振解调法

在滚动轴承的振动故障诊断中，广泛使用解调方法分析诊断故障。利用软件方法实现共振解调时，必须首先构造窄带高频带通滤波器，提取高频共振信息，然后利用Hilbert变换进行解调分析。通过分析谐波小波变换的实现过程，发现信号经谐波小波变换的实质是将信号带通滤波后，进行Hilbert解调。另外，共振解调中要求带通滤波器是窄带高频带通滤波器，广义谐波小波突破了传统二进小波在低频分辨率高，而在高频分辨率低的限制，能够实现超窄带高分辨率检波，满足共振解调的要求。在此基础上，提出了基于谐波小波变换的共振解调算法，为软件实现共振解调提供了一种新的途径。     

一种自适应EPF算法及其在光纤水听器中的应用

基于椭圆拟合的相位生成载波(Phase Generated Carrier,PGC)解调方法是消除非线性因素对光纤水听器PGC解调结果影响的一种有效手段,椭圆曲线参数的最优估计问题是实现该方法的关键。扩展卡尔曼粒子滤波(Extended Kalman Particle Filter,EPF)是解决此类非线性估计问题的一种常用的最优估计算法。但传统的EPF算法在用于常参数过程方程的参数或状态估计问题时,过程噪声的方差通常设置为一个常量,这使得算法难以兼顾收敛速度和估计精度,一定程度上限制了算法的整体性能。为了解决这个问题,文章对现有的EPF进行了改进,提出了一种自适应扩展卡尔曼粒子滤波(Adaptive Extended Kalman Particle Filter,AEPF)算法。模拟仿真和实验结果表明,文中所提出的AEPF算法能根据基于椭圆拟合的PGC解调方法有效地解调出待测声信号,相比EKF算法和EPF算法,AEPF算法的收敛速度和估计精度都得到了提升。此外,文章所提出的AEPF算法也适用于其他具有常参数过程方程的参数或状态估计问题,具有一定的通用性。     

Optical signal processing in dual-wavelength optoelectronic drop analyzer

Dual-wavelength optical signals are injected into the liquid drop through optical fibers in order to study the light intensity variation during the drop growth. Modulation and demodulation are used to reduce the influence of ambient light on the valuable optical signals. HA17555 chip composes the oscillating circuit for light modulation, with different high oscillating frequency for different light source. The light signal collected by a fiber detector after propagation inside the drop is changed into electric signal through the OPA2111 photoelectric circuit. The second-order band-pass filter composed of MAX275 chip is used for signal-separation. The high-pass filter is used to prevent the low frequency signal of ambient light. The valuable signal related to the drop is demodulated by a linear demodulation circuit including a half-wave rectifier, full-wave composition and low-pass filter.     

基于长信号谱自相关的光纤光栅传感解调方法

针对光纤光栅传感领域波长高精度探测和传感复用光栅数量增多的需要,提出一种基于长信号相关谱的新型光纤光栅数字解调技术.该技术在可调谐滤波法的基础上,通过传感光栅与调制光栅反射谱卷积后的信号,即光电探测器的光强时间信号,进行自相关分析以实现对波长漂移的测量以及对传感光栅反射谱形状的识别,增强系统的复用能力,提高了性价比.模拟仿真表明,光纤光栅长信号相关数字解调方法可以准确测量光纤光栅波长的漂移,能更好实现传感复用.等强度悬臂梁实验验证该解调方法能实现光栅应变的高精度测量,优于传统的应变片测试.     

往复机械特征频段信号的解调分解及其应用

提出了往复机械特征频段加速度信号的调幅调频模型,并基于此模型用标准解调法Ｈｉｌｅｒｔ变换法推导出了特征频段加速度信号的解调分解公式。分析和解调测试说明,提出的解调分解方法可成功地实现对特征频段加速度信号的解调分解。在往复机械诊断中的运用实例说明,特征频段信号经解调分解获得的新参量对往复机械的故障诊断是有意义的。     

光学法复现水声声压中的过零点解调系统设计

激光外差干涉是新一代水声声压基准的主要技术,光学干涉系统中的信号解调算法直接影响质点振速和声压量值。为准确得到测量结果,详细介绍了如何从多普勒信号中得到水质点振速的过零点解调算法,并建立了一套在线解调系统。该系统利用信号源产生两路相互正交的多普勒信号模拟光电二极管的输出,再经差分放大电路后进入示波器进行数据采集,最后由主机软件在线读取数据并完成质点振速解调。实验结果有效验证了过零点算法和解调系统的正确性和稳定性,所设计的过零点解调系统可直接应用于激光外差干涉法复现水声声压。     

基于锁相环的解调技术研究

介绍了调相信号的锁相解调技术基本原理以及利用集成锁相环NE564实现对信号的锁相解调。为了解调出不失真的波形,利用集成锁相环NE564和LM725CN芯片设计PM调制解调系统,可以直接实现信号的调制解调功能,利用相位能稳定跟踪的特点避免了频率失锁的缺陷,提高了测量精度。该系统具有操作简单、稳定性强的优点,并在激光外差干涉信号的解调中具有较强的实用性。     

调相信号的数字化解调

通过单周期正弦波曲线模型的滑动拟合法,获得正弦序列的瞬时频率信息,使用对瞬时频率的积分运算,实现了正弦载波相位调制信号波形的精确解调.在调制信号是方波的情况下,给出了相位解调的仿真结果和其它参数的波动情况;在1个实测调相曲线波形上进行的解调分析,给出了相位调制波形的解调结果;在调制信号也是正弦波的情况下,给出了解调失真的计算方法和结果.本方法用于评价载波为正弦波的调相信号时,具有准确度高、分辨力高的特点,可用于调相信号源及其解调设备的指标评价和计量测试.     

齿轮故障振动信号检波解调分析中的混频效应

在齿轮故障诊断中,振动信号解调分析是一种很有效的方法。本文在分析调幅调相信号检波解调分析原理的基础上,讨论了该类算法软件实现过程中产生的混频效应,指出信号在检波解调过程中经过非线性变换后将包含高频成分,有可能发生明显的混频,导致得出错误的解调信号。通过合理地选择采样频率及分析算法中低通滤波器的截止频率或采用较高的采样频率能有效地消除这种混频效应对解调的影响,最后以仿真数据及实验论证了这些结论。     

Intrinsic fiber-optic ultrasonic sensor array using multiplexed two-wave mixing interferometry

An intrinsic multiplexed laser interferometer is presented that allows for the simultaneous detection of acoustic waves by an array of fiber-optic sensors. The phase-modulated signals from each sensor are demodulated by use of an adaptive two-wave mixing setup. The light from each sensing fiber in the array is mixed with a reference beam in a single photorefractive crystal (PRC), and the output beams from the PRC are imaged onto separate photodetectors to create a multiplexed two-wave mixing (MTWM) system. The sensing fibers are embedded in graphite-epoxy composite panels, and detection of both acoustic emission and ultrasonic signals in these materials is demonstrated. The intrinsic MTWM system is an effective tool for the simultaneous demodulation of signals from a large fiber sensor array. Also, the adaptive nature of the MTWM setup obviates the need for active stabilization against ambient noise.     

Y波导残余强度调制对IFOG性能的影响

本文首先通过正弦波调制下干涉信号光强分析解调出光纤陀螺的输出信号,进而得出残余强度调制存在的情况下陀螺输出信号的变化情况,同时,通过分析陀螺信号的变化说明残余强度调制对光纤陀螺性能的影响与陀螺精度要求有关,精度越高,其影响越明显.其次,具体分析了数字闭环光纤陀螺受残余强度调制影响的情况下,其解调输出电压变化引起的数字阶梯高度变化,并通过残余强度调制系数与数字阶梯高度的关系式,说明了残余强度调制对光纤陀螺零偏和标度因数的影响.最后,对所得出的残余强度调制系数与光纤陀螺标度因数稳定性的关系进行了Matlab仿真,通过仿真结果,更进一步说明残余强度调制对数字闭环光纤陀螺标度因数稳定性的影响.     

Expansion of linear range of Pound-Drever-Hall signal

We propose new solutions for expanding the linear signal range between the laser frequency deviation (or mirror position) and the voltage signal derived by the Pound-Drever-Hall (PDH) method for optical Fabry-Perot cavity resonance control. One solution is to perform not in-phase demodulation but near-Q-phase demodulation. Another solution is to take a suitable combination of signals demodulated by odd-harmonic modulation frequencies in the in phase. Although the PDH signal sensitivity will be diminished, the PDH signal linear range can be extended. From a practical standpoint, it is desirable that a sideband frequency for the PDH method is near the FP cavity resonance.     

Analysis of interferograms with a spatial radial carrier or closed fringes and its holographic analogy

It is well known that an interferogram can be demodulated to find the wave-front shape if a linear carrier is introduced. We show that it can also be demodulated if it has many closed fringes or a circular carrier appears. A basic assumption is that the carrier fringes are of a bandwidth adequate to contain the wave-front distortion. This phase determination, called here demodulation, is made in the space domain, as opposed to demodulation in Fourier space, but the low-pass filter characteristics must be properly chosen. For academic purposes a holographic analogy of this demodulation process is also presented, which shows that the common technique of multiplying by a sine function and a cosine function is equivalent to holographically reconstructing with a tilted-flat wave front. Alternatively, a defocused (spherical) wave front can be used as a reference to perform the reconstruction or demodulation of some closed-fringe interferograms.     

广义解调算法中能量因子的引入与配置原理的研究

广义解调算法在振动信号时频谱应用中效果显著,而在分析解调频谱时对频率的初始值非常敏感。提出了能量因子可调的广义解调算法,将其应用到轴承振动信号的处理中并进行有效性评估。为获得轴承信号的相位函数,使用峰值搜索算法在包络信号中检测瞬时故障特征频率,估计拟合函数;引入了能量因子的概念,根据拟合函数配置能量因子,按照提出方法对原始信号进行重构;参考能量因子对重构信号的相位函数进行估计;对重构信号进行解调,得到关于能量因子的解调信号。根据特征频率的解调值与通过测得转速计算的理论值进行对比,评价能量因子配置的合理性。仿真和实测信号的处理,证明了算法的有效性。