Weak Signal Detection Method Based on Lock-In Amplifier
Nie Yaqi · Chuangan jishu xuebao · 2013
A digital lock-in amplifier is designed based on correlation detection principle,it focused on the relation between sample frequency and correlation operation result. It is find that there exists inherent error in correlation operation when reference signal is square wave and the signal frequency has a relationship with sample frequency.To reduce the error,it introduced a dynamic sample to design digital lock-in amplifier at the first time,the result showed that the more the number of sample frequencies,the less the singularity error. Simulation and test to the designed detecting system were got based on LabVIEW software,the result showed that the digital lock-in amplifier can detect the signal which frequency is under 500 kHz effectively when signal amplitude is 5 V,standard deviation of the noise is less than 50( SNR =-34. 04 dB),and the proportional error between system test result and theoretical value are mainly under 2%.