Abstract: Fourier transform infrared spectroscopy due to large flux, wide spectral range, high resolution and many other advantages in the field of atmospheric environment monitoring has been widely used.Based on the weak infrared interference optical signal characteristic of Fourier transform infrared spectrometer and the mercury detector based on the tellurium cadmium mercury photoconductive type infrared detector, the characteristics of the interference optical signal of the Fourier transform spectrometer based on the Michelson interference method are analyzed. Narrowband filter method as the core weak signal detection circuit, the equivalent noise model is established to analyze the noise performance of the circuit. The designed circuit was applied to the Fourier transform spectrometer, and the atmospheric mid-infrared band spectrum of 400-7000cm-1 was obtained at room temperature, almost covering the common absorption peak of atmospheric pollutants in the mid-infrared band, which could be better Achieve the resolution of different concentrations of pollutants and measurement.

Key words: photodetector, weak signal;preamplifier circuit, band pass filter;