基于相敏检波技术的锁定放大器

Lock-in Amplifier Based on Phase Sensitive Detection

介绍一种由信号通道、参考信道和相敏检波三部分组成的锁定放大器,用于实现强噪声干扰下μV级信号幅值的有效检测。其中信号通道由纯电阻分压网络、加法器、交流放大器和带通滤波器组成;参考通道包括移相器和触发整形电路;相敏检波是该锁定放大器的核心元件,检波后经过低通滤波器输出一个直流信号,经MSP430进行AD采样并根据理论推导进行计算,在LCD1602上显示出特定频率的微弱信号的幅值。实验证明在误差范围内,该锁定放大器能在10μV^1m V微弱正弦信号的十倍噪声干扰下检测出被测信号的幅值。

This paper introduces a lock-in amplifier used to detect the amplitude of μV signal under strong noise interference,which is composed of three parts：signal channel,reference channel and phase sensitive detector.The signal channel is composed of divider resistance,adder,AC amplifier,and band-pass filter.The reference channel is composed of phase shifter and trigger shaping circuit.Phase sensitive detector is the core element. After that,the low pass filter outputs a DC signal.MSP430 disposes this signal by AD sampling and calculate based on theoretical derivation.