锁定放大微弱信号检测仿真与设计研究

为解决商用锁定放大器不便于特定应用背景下微弱信号检测系统的灵活扩展与剪裁,该文分析了正交锁定放大的基本原理,建立了正交锁定放大的MATLAB/SIMULINK数学模型,展示了锁定放大所能达到的性能以及数字信号处理对锁定放大性能的改善效果。给出了正交锁定放大检测装置的硬件设计过程,包括前端信号调理电路、移相电路、相敏检测电路、低通滤波电路、均方值电路及数字显示电路等。仿真表明,在高斯噪声影响下,微弱信号检测可以达到较高的检测精度,且通过滑动平均值滤波算法可以有效提高检测的精度。实验研究表明,在噪声信号峰峰值为10 V情况下,可以将50 m V的有用信号提取出来,且在50 m V以上可以拟合出较好的输入输出线性关系,便于检测装置的标定。

Study on the simulation and design of weak signal detection based on lock-in amplifier

In order to solve the flexible expansion and clipping of weak signal detection system, the paper analyzes the basic principle of the orthogonal lock-in amplifier, and establishes the MATLAB/SIM-ULINK mathematical model of the orthogonal lock-in amplifier. The hardware design of the orthogonal lock-in amplifier is presented, including the front circuit for signal turning, phase shift circuits, phase sensitive detection circuit, low-pass filter circuit, mean square value circuits and digital display circuit. The simulation shows that the weak signal detection can achieve higher detection accuracy under the in-fluence of Gauss noise and the accuracy of the detection can be effectively improved by using the sliding average filtering algorithm. Actual experimental studies show the useful signal of 50 mV can be extracted from the noise signal of 10 V P-P value with linear relationship which can be use to calibration of the detection device.