WMS温度测量中谐波信号锁相放大器的设计

在波长调制光谱技术(Wavelength Modulation Spectroscopy, WMS)温度测量中,传统的锁相放大器测量谐波信号的振幅必须对被测信号及参考信号的相位单独进行调整。针对这一问题,设计了一种基于高精度平衡调制器AD630进行同步相敏检测的谐波信号的双锁相放大器。与传统的锁相放大器相比,所提双锁相放大器利用正交双通道的平方和检测,可以避免被测信号与参考信号进行严格的相位匹配问题。利用Multisim软件构建仿真模型,包括前置高通滤波器、正交双通道的相敏检波器、低通滤波器等部分。理论计算和仿真结果表明,所提方法能够准确检测微弱一次、二次、四次谐波信号的幅度,检测误差小于5%,具有电路简单、运行速度快、线性度高等优点,能够满足WMS温度测量工程应用。     

锁相放大器在温度传感器校准系统中的应用

本文介绍了锁相放大器的原理和SR380锁相放大器在温度传感器校准系统中的应用。在瞬态温度测量中存在动态误差,需对温度传感器进行校准。温度传感器校准系统加入锁相放大器后,可将低温时的微弱信号检测出来,提高了校准系统的信噪比,拓宽了校准系统的温度下限。     

锁相放大器直流输出分析——输入占空比可调矩形波信号

锁相放大器在微弱信号检测中具有广泛的应用,为了更好地了解锁相放大器的工作特性,采用占空比可调的矩形波信号作为信号源输入,系统研究锁相放大器的直流输出与输入信号的相位及占空比的关系。实验结果表明:采用幅值相同、不同占空比的矩形波信号通过锁相放大器其直流输出值不同,输入不同占空比的矩形波的被测信号在锁相放大器直流输出与相位和占空比的关系图像为三角波形,当占空比为0.5时有最大输出值。     

用锁相放大器实现电池内阻在线测量

本文对传统的电池内阻测量方法进行了研究比较,提出了用锁相放大器测量电池内阻的新方法,详细阐述了锁相放大器的基本结构与工作原理以及用锁相放大器实现电池内阻测量的实际电路,通过对多种电池内阻的测量以及电池充放电过程中内阻的在线监测,有效地克服了噪声和干扰,快速获得稳定、精确的内阻测量数据,能实现完全的在线检测,并且简化了设计。     

一种应用于涡流检测的DDS正交信号源

介绍了采用单片DDS芯片AD9854设计的频率可连续调节的宽带正交信号源，给出了系统的硬件构成、软件流程及软件编程方法等。该正交信号源具有优良的频率准确度，两路输出信号正交性好，且频带范围宽，应用在智能涡流无损检测中较好地解决了激励信号源及正交锁相放大器检测电路中参考源的问题。     

锁相放大器校准方法研究

锁相放大器在微弱信号测量中已经得到了广泛的应用,本文通过对锁相放大器基本结构和工作原理的分析,总结出了锁相放大器一般参数的校准方法。     

激光火工品系统自动检测技术研究

在简要介绍激光火工品系统检测技术发展的基础上,综述了激光火工品系统检测中微弱光信号的探测原理与处理方法以及这些方法的应用;通过对锁相放大器频谱迁移法、谐波小波频域提取法、双路消噪声法以及放大与滤波电路法的比较和分析,得出锁相放大器频谱迁移法和放大与滤波电路法可用于激光火工品系统检测的结论．     

某型航空发动机篦齿盘裂纹的原位涡流检测

针对某型航空发动机篦齿盘上产生的裂纹缺陷,在不拆分发动机的前提下,提出采用涡流检测的方法对篦齿盘进行原位无损检测．设计完成了一套可用于篦齿盘裂纹原位检测的涡流无损检测系统．采用正交型锁相放大器对涡流检测信号进行处理,提高了信号检测精度同时达到了抑制干扰的作用．在标准检测试件和模拟试件上分别进行了试验,试验结果表明,该涡流检测系统可以实现航空发动机篦齿盘裂纹缺陷的原位检测,并且可以定性判断裂纹的深度．     

用微机提取俄歇电子信号的几个问题

将微机应用于表面分析的俄歇信号采集处理,以前曾作了简要介绍。尽管锁相放大器是一个从噪声中提取弱信号的仪器,但如果信号中噪声太强,将限制锁相放大器灵敏度的使用。图1是对GaAs(100)作俄歇谱分析的曲线,人们很难从中得到些什么信息。测量时锁相放大器的灵敏度     

锁相放大器测试J422焊条表面分形维数

使用锁相放大器测试了Ｊ４２２焊条表面分形维数，文中给出了测试原理、方法和结果。     

微波、毫米波相位噪声测试系统的研制

提出了首先对微波、毫米波信号进行下变频,再利用锁相环提取被测试信号相位噪声的相位噪声提取方法,采用现代谱分析技术对提取出的相位噪声信号在频率中进行分析,并利用"反卷积"技术实现测试系统的误差校正,研制实现了微波、毫米波相位噪声测试系统.实验测试结果表明该系统具有测试灵敏度高和被测信号频率范围广的优点,证明了它具有较大的应用价值.     

High-speed measurement of three-dimensional surface profiles up to 10 μm using two-wavelength phase-shifting interferometry utilizing an injection locking technique

High-speed two-wavelength phase-shifting interferometry is presented. The technique is aimed at high-speed in-line inspection of spacers in liquid crystal display panels or wafer bumps where the measuring range is well determined and high-speed measurements are essential. With our test setup, the measuring range is extended to 10 μm by using two injection locked frequency scanning lasers that offer fast and equidistant phase shifting of interference fringes. A technique to determine the unwrapped phase map in a frequency scanning phase-shifting interferometry without the ordinary phase-unwrapping process is proposed.     

Power scaling of a fiber master oscillator power amplifier system using a coherent polarization beam combination

A new coherent polarization beam combination (CPBC) architecture was employed to combine four amplified beams and produce over 25 W of coherent output with 94% efficiency and nearly diffraction-limited beam quality. The individual beams were produced by a fiber master oscillator power amplifier system and their phases were controlled and locked using servo-controlled phase modulators. The CPBC approach relies on a coherent superposition of orthogonal polarization states and allows the combination of an arbitrary number of beams with arbitrary power ratios.     

基于数字锁相环的科氏质量流量计信号处理方法

针对科里奥利质量流量计信号处理中存在的问题 ,即信号频率在小范围内变化和信号易受谐波干扰 ,采用基于数字锁相环的方法处理科氏质量流量计的信息 ,跟踪信号频率的变化 ,计算相位差。对美国专利提出的方法进行了改进 ,做了仿真。仿真结果表明 ,在有谐波干扰的情况下 ,数字锁相环方法可以准确地跟踪信号频率的变化和计算相位差。本文还对计算误差进行了分析     

Two-dimensional Phase Locked Loop Demodulation of Interferograms

Abstract

A new technique for continuous phase determination of an interferogram based on a digital phase locked loop is presented. The main advantage of this method, with respect to well established techniques such as Fourier or phase stepping demodulation, is that the traditional approach to phase unwrapping processes by removal of discontinuities is not required. The phase is determined continuously as the phase locked loop scans the two-dimensional interferogram. Because of the sequential nature of the algorithm proposed, this can be implemented using a special purpose video processor for phase determination at video rates. The above mentioned properties makes the presented technique a fast algorithm for phase determination of carrier frequency interferograms modulated by a two-dimensional smooth phase function.     

Method for measuring the losses and loading of a quartz crystal microbalance

A novel, experimentally simple, and highly sensitive method for measuring the loading of a quartz crystal resonator was developed. The method is based on the use of double-sideband suppressed-carrier modulated high-frequency signal, which is swept through the resonance range of the resonator. Induced current in the resonator is passed through a capacitor, and the voltage over the capacitor is demodulated on an analog multiplier. The phase and amplitude information is carried to the frequency-doubled modulation signal and measured on a conventional low-frequency two-phase lock-in amplifier. A complex dimensionless loading parameter is obtained from the experimental data by nonlinear model fitting. The real and complex parts of this loading parameter have a simple relationship with other parameters commonly used for characterizing the resonator loading. The performance of the method was demonstrated by measuring a series of different glycerol-water mixtures ranging from 0 up to 100% glycerol. The results were close to the shear acoustic impedance of these mixtures measured and calculated from their viscosities and densities.     

Distributed Brillouin sensor system based on offset locking of two distributed feedback lasers

An offset locking technique, which uses an external optical delay line to tune the distributed feedback (DFB) laser frequency and a proportional-integral-derivative (PID) controller to lock the tuned frequency, is proposed for the first time, to the best of our knowledge, in the distributed Brillouin sensor system. This method provides large tuning range (greater than 1 GHz), high tuning speed (less than 100 mus per frequency step), and frequency tuning is independent of the laser frequency and power. The two DFB lasers are phase locked at the Brillouin frequency using a hardware PID controller. Using this offset locking with optical delay line, we demonstrated a high signal-to-noise ratio of 32 dB, which allows 1 m spatial resolution and better than 0.6 MHz frequency measurement accuracy (equivalent to 0.5 degrees C temperature resolution or 8 microepsilon strain resolution) over kilometers sensing length. The bias of the electro-optic modulator is controlled by a lock-in amplifier to provide high temperature or strain measurement accuracy.     

Theory of Passive Mode Locking of a Laser Having Two Laser Amplifiers of Unequal Relaxation Time with a Slow Saturable Absorber

This paper presents a closed-form solution for the pulses of a laser having two homogeneously broadened laser amplifiers of unequal relaxation time mode locked by a ‘slow’ saturable absorber. The pulse shape is found to be secant-hyperbolic. It is found that the gains of both amplifiers participate in time-modulating the pulse and that the pulses are bandwidth-limited by the amplifier with a relaxation time longer than the cavity round-trip time. We have also shown that the model of a ‘slow’ saturable absorber and an amplifier of relaxation time longer than the cavity round-trip time does not give self-starting, mode-locking solutions.     

Stabilization of electro-optic modulator bias voltage drift using a lock-in amplifier and a proportional-integral-derivative controller in a distributed Brillouin sensor system

In a distributed Brillouin sensor system, it is crucial to keep the pulse energy uniform for a constant signal-to-noise ratio. This means that the variable dc leakage (pulse base) for the electro-optic modulator (EOM) must be locked. We examine two different methods of locking the EOM bias voltage and look at the advantages and disadvantages of each locking method. It is found that the two locking methods, one based on a lock-in amplifier and the other using proportional-integral-derivative control, both have applications in which they excel at locking the pulse base.