毕业设计--锁相放大器的LabVIEW实现

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1、锁相放大器的 LabVIEW 实现 - I - 锁相放大器的锁相放大器的 LabVIEWLabVIEW 实现实现 Function realization of lock-in amplifier by LabVIEW programming 摘 要 锁相放大器 （Lock-in Amplifier,LIA） 是一种根据相关检测原理设计的同步相干检测 仪，能够准确检测提取出淹没在强噪声背景中的周期性有用信号，是微弱信号检测 （Weak Signal Detection） 领域中最重要和最有效的精密仪器之一， 广泛地应用与基础科 学研究、国防科技、生物医学信号、物理探伤等领域。 相敏检波器（Ph

2、ase Sensitive Detector, PSD）是锁相放大器的核心器件，能够实现对 待测信号和参考信号进行相关运算；而低通滤波器的通频带宽决定了相敏检波器输出信 号的谐波成分，进而对锁相放大器的精度产生影响。因此，本文着重研究了相敏检波器 和低通滤波器的设计环节，并在参考信道设置了两路正交的参考信号以避免了输出结果 对相位差的依赖。 本文通过分析锁相放大器的工作原理，利用虚拟仪器技术，基于 LabVIEW 软件开发 平台实现了双锁相放大器的设计方案。经测试证明，本文设计的正交矢量型数字锁相放 大器具有较好的抑噪性能，能够大幅度提高输出信号的信噪比。 关键词：锁相放大器；虚拟仪器锁相放大

3、器；虚拟仪器；相敏检波器相敏检波器 锁相放大器的 LabVIEW 实现 - II - Function realization of lock-in amplifier by LabVIEW programming Abstract Lock-in Amplifier (LIA),based on the principle of correlation-detecting, is one of the most effective meansin weak signal detections and prove to be able to detect and measure periodi

4、cal signals, the magnitude of which are usually so weak against the surrounding noise, widely used in the fields of scientific research, national defense science and technology, biomedical engineering, physical detection, and so on. Phase sensitive detector(PSD) is the core of the lock-in amplifier

5、and can identify the measured signals whose frequency is the same as the reference signal; and its output is determined by the pass band-width of frequency of the LPF, which also affects the precision of the lock-in amplifier. Thus, this paper studies the realization of the PSD and the LPF, and set

6、up two orthogonal reference signal channels to avoid the dependence on the phase difference. The paper analyses the realization of the lock-in amplifier, and use LabVIEW to realize the dual-phase lock-in amplifier. And, it proves to be effective through the simulations, shows a good performance in the detection of weak signals, and greatly improves the SNR of the output signals. Key Words：Lock-in Amplifier；Virtual Instrument；Phase Sensitive Detector 锁相放大器的 LabVIEW 实现 - III - 目 录 摘要 . I