Design of dual-phase lock-in amplifier used for weak signal detection

In this paper, preamplifier circuit, filter circuit and bias circuit with protection were designed. With the help of DSP and LabVIEW, the algorithm implementation of dual-phase lock-in amplifier, data processing, data display and the serial communication between DSP and LabVIEW were achieved. A complete digital dual-phase lock-in amplifier system based on DSP and LabVIEW was designed. It can extract the weak sinusoidal signals submerged by noise. This design has the advantages of high accuracy, low cost and portability, and its update and transplantation are easy. Experiment results show that when the rate of weak sinusoidal signal's additional noise is 100%, the relative error of amplitude detection is less than 2%, and the absolute error of phase measurement is less than 3°. It fully satisfies the requirements of detecting weak signals submerged by noise in general application. It can also serve as a high cost performance platform in the intensive study of weak signal detection.