基于自动频率跟踪的虚拟数字锁相放大器

为避免传统设计中待测信号与参考信号之间的道间干扰，以及信号传输过程中引入的噪声,设计了一种基于LabVIEW开发平台的虚拟数字锁相放大器（DLIA：Digital Lock-In Amplifer）。通过引入自动频率跟踪模块，大大降低了待测信号与参考信号频率的失配程度。同时，在经典的正交相敏检波算法基础上，通过对输出信号进行优化处理，得到了良好的输出波形。实验结果显示，待测信号的信噪比R_SNR可小于-20 dB，可检测的最小幅值达10 μV，自动频率跟踪模块的锁频误差小于0.02%，信号幅值的测量误差小于0.05%。该设计的自动频率跟踪能力的虚拟DLIA具有良好的测量稳定性。

Virtual Digital Lock-in Amplifier Based on Automatic Frequency Tracking

In order to avoid the crosstalk between the measured signal and the reference signal,and the noise introduced during the tr ansmission of the signal in traditional design,a virtual(DLIA:Digital Lock-In Amplifier) based on LabVIEW p latform is designed.An automatic frequency tracking module is used in this des ign,and the mismatch between the frequencies of the measured signal and the ref erence signal is greatly reduced.By optimizing the output sign al,an excellent waveform was observed,based on the traditional quadrature phase sensitive detection algorithm.The experimental results show that the SNR(Signal to Noise Ratio) of the measured signal is less than-20 dB,the minimum detec t able amplitude is up to 10 μV,and the relative error of the frequency-locking by the automatic frequency tracking module and that of the measured signal’s amp litude are less than 0.02% and 0.05%,respectively.That there is good measuring stability of the designed virtual DLIA with automatic frequency trac king module.