激光多普勒信号探测与数据处理方法研究

发布时间：2018-06-30 20:49

本文选题：多普勒效应 + 光电探测器　；参考：《西安工业大学》2017年硕士论文

【摘要】：在工程领域中,速度测量广泛用来测量物体的动态特性,基于多普勒效应的测速技术是一种重要的检测手段。本文为了解决通信波段高速光电探测器设计技术和高速多普勒信号采集与处理技术作为光纤激光多普勒测量的主要核心技术,但国内研究并不多且尚未有好的解决方案的问题,重点研究了光电探测器设计方案和多普勒信号处理算法,对全光纤激光多普勒测量光路进行了分析和设计,搭建了实验测量装置,分别对光路、探测器和解算算法进行了实验验证和精度分析,以保证激光多普勒测量技术实际应用中的稳定性。主要研究内容如下:1.比较了四种零差检测光路,解决了全光纤激光速度干涉仪存在的信号光功率损耗大、多普勒信号对比度低等问题。分析了反射光耦合方式、参考光产生的方式;计算了光路的损耗以及多普勒信号的对比度;设计了四种光路的对比性实验,分别测量了光损耗以及多普勒信号的对比度;根据实验分析的结果,确定了最优光路。2.介绍了高速光电探测器的工作原理;针对探测器多普勒信号信噪比低的问题,分析了信噪比的影响因素,选择铟钾砷(InGaAs)PIN型光电二极管作为光电转换器件,光电二极管工作在光伏模式(零偏置);设计了光电探测器的前置放大电路和主放大电路;针对高速电路和提高信噪比,介绍了探测器PCB设计的注意事项。3.分析了三种多普勒信号处理算法:基于时频分布的瞬时频率估计方法、Tikhonov正则化数值微分算法和正弦函数拟合算法。根据综合分析选用基于时频分析的瞬时频率估计方法,选择升余弦加权去噪算法作为信号数字去噪算法。4.设计了激光多普勒测量系统的全光纤光路系统和信号处理电路板。光路系统采用1550nm波长激光器、光纤耦合器、隔离器等光纤无源器件;电路板采用FPGA作为核心处理器,高速AD和以太网作为数据采集和传输器件,搭建了实验装置。再分别用喇叭和音圈电机作为测试对象对光纤光路、光电探测器和信号解调算法进行了验证,结果表明探测器以及光路和电路设计可行,信号处理算法满足精度要求,系统测量相对误差小于1%。实验验证了测量系统的可靠性和精度。
[Abstract]:In the field of engineering, velocity measurement is widely used to measure the dynamic characteristics of objects, and velocity measurement based on Doppler effect is an important method. In order to solve the problem that the design technology of high speed photodetector in communication band and the acquisition and processing technology of high speed Doppler signal are the main core technologies of optical fiber laser Doppler measurement, there are few domestic researches and no good solutions. The design scheme of photodetector and the algorithm of Doppler signal processing are studied emphatically. The optical path of all-fiber laser Doppler measurement is analyzed and designed. In order to ensure the stability of laser Doppler measurement technology, the detector and calculation method is verified by experiments and precision analysis. The main research contents are as follows: 1. Four homodyne detection methods are compared to solve the problems of high power loss of signal and low contrast of Doppler signal in all fiber laser velocity interferometer. The coupling mode of reflected light and the way of producing reference light are analyzed, the loss of optical path and the contrast of Doppler signal are calculated, the contrast experiments of four kinds of optical path are designed, the optical loss and contrast of Doppler signal are measured, respectively. According to the results of experimental analysis, the optimal light path. 2. This paper introduces the working principle of high speed photodetector, analyzes the influence factors of signal-to-noise ratio, and selects InGaAs PIN photodiode as photoelectric conversion device, aiming at the problem of low signal-to-noise ratio of detector Doppler signal. The photodiode works in photovoltaic mode (zero bias), the preamplifier circuit and main amplifier circuit of photodetector are designed, and the attention of PCB design of detector is introduced for high speed circuit and improving signal-to-noise ratio (SNR). Three Doppler signal processing algorithms are analyzed: Tikhonov regularization numerical differential algorithm and sinusoidal function fitting algorithm based on time-frequency distribution. According to the comprehensive analysis, the instantaneous frequency estimation method based on time-frequency analysis is selected, and the lifting cosine weighted de-noising algorithm is chosen as the signal digital denoising algorithm .4. The all-fiber optical circuit system and signal processing circuit board of laser Doppler measurement system are designed. 1550nm wavelength laser, fiber coupler, isolator and other passive optical fiber devices are used in the optical circuit system, and the circuit board is used as the core processor, and high-speed AD and Ethernet are used as data acquisition and transmission devices. The optical fiber optical circuit, photoelectric detector and signal demodulation algorithm are verified by using horn and voice coil motor as test objects respectively. The results show that the detector, optical circuit and circuit design are feasible, and the signal processing algorithm can meet the precision requirements. The relative error of system measurement is less than 1. The reliability and accuracy of the measurement system are verified by experiments.
【学位授予单位】：西安工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN15

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