Research On Synchronous Adjustment Method Of Double Signals In Phase Locked Amplification Of Spectrometer

The near infrared spectrometer has been widely applied to various fields because of its advantages of rapid analysis,no pollution,simple preparation of sample,high measurement precision,and nondestructive measurement.In the portable Near-infrared(NIR)spectrometer self-developed,the phase-locked amplification technique is used to detect the weak signal.In phase locked amplification system,a reference signal which has the same frequency and same phase as the measured signal is required to be multiplicative in a phase sensitive detector.However,due to the spectral signal modulation and filtering amplification,there is frequency and phase difference between the double signals,which affects the accuracy of spectrometer demodulating the measured signal.Therefore,aiming at the relationship between the frequency and phase of the measured signal and the reference signal,the research on synchronous adjustment method of double signals in phase locked amplification of Near-infrared Spectrometer was studied.Based on the working principle and mechanical structure of the near infrared spectrometer,the influence of the relationship between double signals on the demodulation of spectral data by phase locked amplification was analyzed.The influence of the eccentricity of the modulator of the spectrometer on the frequency of the double signals and the location difference of the optical coupler on the difference between the double signals were experimentally studied.According to the analysis of the experimental results,a scheme to adjust the synchronization of the double signals was proposed.The steps were designed and the experimental platform was set up.Finally,the synchronous adjustment of the double signals was realized.The application experiments of frequency and phase four states of double signals in phase locked signal in amplification of spectrometer showed that the synchronization of double signals can improve the measured number and signal-to-noise-ratio(SNR)of the spectral data of the near infrared spectrometer.The application experiment showed that the frequency of the measured signal and the reference signal in the phase locked amplification of the spectrometer was 610.65±1.02 Hz and 610.65±1.06 Hz respectively.In the process of synchronous adjustment of double signals,the single point measurement and sample spectrum measurement are carried out for the four states of the spectrometer.The spectral numbers of the four states single point measurements are 54538,47960,49588 and 57498 respectively,and the SNR of the spectral data is 1915,280,498 and 2591,respectively.The SNR and the number of spectral data of the spectrometer could be improved by the synchronization of the double signals in phase locked amplification.