基于DSP的正交锁相放大器研制及其红外气体检测应用

发布时间：2019-03-11 12:51

【摘要】：本工作来源于国家科技支撑计划：“煤矿用红外CO检测仪(传感器)研发”。煤炭的不充分燃烧会产生甲烷和CO气体，轻者使人中毒，重者造成火灾矿难，近年来，各地火灾矿难事件频发，严重威胁着人们的生命财产安全。随着半导体技术飞速发展，以它为基础的分布反馈式半导体激光器(DFB)也得到了广泛的应用，尤其是用于以朗伯比尔定律为基础的红外气体检测中。可调谐二极管激光吸收光谱技术（TDLAS）具有高灵敏度和高选择性，而其中的二次谐波具有与浓度相关信息，需经过锁相放大器才能提取，因此研究本课题具有重要意义。在红外气体检测中，基于可调谐二极管激光吸收光谱技术，本文设计了一种正交锁相放大器来提取谐波信号。首先，在MATLAB的Simulink软件仿真平台上，模拟了整个实验系统，旨在对它的功能进行仿真和验证。然后，将DSP(数字信号处理器)作为核心控制器，并搭建了谐波信号锁相放大器的真实硬件系统。最后，通过实验，验证硬件系统的各个功能的可行情况。首先采用标准的正弦信号作为待测信号，对输入输出信号幅值进行对比，测量最大误差小于4%，，线性拟合优度达到0.99994；其次，利用待测信号（ARM模拟经气体吸收后的差分信号）和参考信号（分别是同频及倍频方波）来提取谐波信号。一次谐波最大误差小于3.5%，由于微弱的二次谐波信号易受噪声的干扰，因此它的误差在5%以内。最后通过改变输入信号的浓度值，分别提取出相应的二次谐波信号。该系统的高稳定性和性价比，使得它具有广阔的应用前景。本文创新点：1、自主研发并实现了一种用于谐波信号提取的便携式正交锁相放大器，它无需参考信号与待测信号同频同相，省去了复杂的移相环节，简化了硬件系统设计的复杂度。2、该便携式仪器可用于基于TDLAS技术的任意气体检测中，例如甲烷，CO，水汽等。
[Abstract]:This work comes from the national science and technology support plan: research and development of infrared CO detector (sensor) for coal mine. Insufficient combustion of coal will produce methane and CO gas, light people poisoning, heavy ones cause fire mine disaster. In recent years, fire and mine accidents occur frequently all over the country, which seriously threaten the safety of people's life and property. With the rapid development of semiconductor technology, distributed feedback semiconductor laser (DFB) based on it has been widely used, especially in infrared gas detection based on Lambert's law. Tunable diode laser absorption spectroscopy (TDLAS) has high sensitivity and selectivity, and the second harmonic has concentration-related information, which requires phase-locked amplifier to be extracted. Therefore, it is of great significance to study this subject. In infrared gas detection, based on tunable diode laser absorption spectroscopy, an orthogonal phase-locked amplifier is designed to extract harmonic signals. Firstly, on the Simulink software simulation platform of MATLAB, the whole experiment system is simulated in order to simulate and verify its function. Then, the DSP (Digital signal processor) is used as the core controller, and the real hardware system of the harmonic signal PLL amplifier is built. Finally, through the experiment, the feasibility of each function of the hardware system is verified. Firstly, the standard sine signal is used as the signal to be measured, and the amplitude of the input and output signal is compared. The maximum error of measurement is less than 4%, and the linear goodness of fit is 0.99994. Secondly, the harmonic signal is extracted by using the signal to be measured (ARM simulates the differential signal absorbed by gas) and the reference signal (which is the same frequency and double frequency square wave respectively). The maximum error of the first harmonic is less than 3.5%. Because the weak second harmonic signal is easily disturbed by noise, its error is less than 5%. Finally, the second harmonic signal is extracted by changing the concentration value of the input signal. Because of its high stability and cost-performance, the system has a broad application prospect. The innovation of this paper is as follows: 1. A portable quadrature phase-locked amplifier for harmonic signal extraction is developed and implemented independently. It does not need the reference signal and the signal to be measured in the same frequency and phase, and saves the complicated phase-shift link. The design complexity of hardware system is simplified. 2. The portable instrument can be used in any gas detection based on TDLAS technology, such as methane, CO, water vapor and so on.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN722

【参考文献】