WMS温度测量中谐波信号锁相放大器的设计

Design of Harmonic Signal Lock-In Amplifier in WMS Temperature Measurement

在波长调制光谱技术(Wavelength Modulation Spectroscopy,WMS)温度测量中,传统的锁相放大器测量谐波信号的振幅必须对被测信号及参考信号的相位单独进行调整。针对这一问题,设计了一种基于高精度平衡调制器AD630进行同步相敏检测的谐波信号的双锁相放大器。与传统的锁相放大器相比,所提双锁相放大器利用正交双通道的平方和检测,可以避免被测信号与参考信号进行严格的相位匹配问题。利用Multisim软件构建仿真模型,包括前置高通滤波器、正交双通道的相敏检波器、低通滤波器等部分。理论计算和仿真结果表明,所提方法能够准确检测微弱一次、二次、四次谐波信号的幅度,检测误差小于5%,具有电路简单、运行速度快、线性度高等优点,能够满足WMS温度测量工程应用。

When measuring the temperature by wavelength modulation spectroscopy(WMS),the traditional lock-in amplifier must adjust the phase of the measured signal and the reference signal separately when measuring the amplitude of the harmonic signal.Therefore,this paper designs a dual-lock-in amplifier based on a high-precision balanced modulator AD630 for synchronous phase-sensitive detection of harmonic signals.Compared with conventional,the proposed dual-lock-in amplifiers can avoid strict phase matching between the measured signal and the reference signal by quadrature dual-channel sum-of-squares detection.Multisim software is used to build the simulation model,including pre-high-pass filter,quadrature dual-channel phase-sensitive detector,low-pass filter and so on.Theoretical calculation and simulation results show that the proposed method can accurately detect the amplitude of weak first,second and fourth harmonic signals,and the detection error is less than 5%.It has the advantages of simple circuit,fast running speed and high linearity,and it can meet the engineering application of WMS temperature measurement.