The Design Of Recuperate And Obtain Circuit Of The Photo-elastic Modulation Interference Signal

With the advancement of science and technology and its rapid development,spectroscopy measurement technique has been widely used in military fields, aerospacedetection, security, environmental protection, etc high-tech fields. In order to meet the needsof the spectroscopy, different structure spectrometers have been developed by the scientist.Among them, with its high modulation frequency, high sensitivity, wide spectral range andshock resistance and other advantages, the photo-elastic modulation Fourier transformspectrometer (PEM-FTS) has obvious advantages in the transient spectral detection field. Theinterference signal of the PEM-FTS not only has high modulation frequency, and the electricsignal from the detector is very weak. The amplification and extraction of the electric signal iscrucial for the development of the PEM-FTS. Wherefore, how to realize reasonableamplification, filtering, and acquisition, high-speed storage of the electric signal are theimportant science problems need to be solved.Based on the working principle of the photo-elastic modulation Fourier transformspectrometer, the paper analyses the generation principle of the interference signal and itscharacteristics, makes research to conditioning and access technology of the interferencesignal of the PEM-FTS. A kind of circuit for conditioning and accessing the interferencesignal is designed.First, according to the frequency characteristic of the interference signal and itsamplitude characteristic, a reasonable broadband amplifier and low pass filter circuit isdesigned for conditioning the interference signal. This circuit can ensure the interferencesignal in a certain frequency range to obtain a stable amplification and output waveforms, inorder to facilitate subsequent processing the interference signal.Second, in order to achieve the interference signal restoring spectral wavelengthcalibration, the reference design of the present paper laser interference signal countingzero-crossing comparator circuit to determine the transient maximum optical path difference,thereby completing the wavelength calibration.Finally, according to the interference signal data volume per second can reach tens ofthousands of the characteristics of the interference pattern, on the basis of the interference signal conditioning circuit design FPGA-based high-speed AD acquisition and SDRAM memory circuit tocomplete the acquisition circuit of the interference signal. This circuit makes a foundation for theresearch and practical application of the PEM-FTS.