Research On Weak Signal Detection Technology Of FTIR Spectrometer

Fourier transform infrared spectrometer has many advantages such as high signal-to-noise ratio,high detection accuracy,large luminous flux,and multi-channel simultaneous measurement.It has been widely used in military,medical,and industrial and agricultural production fields,etc.Component identification plays an important role.Among them,the signal detection circuit is an important constituent module of the FTIR infrared spectrometer,and this module will directly affect the minimum measurable signal of the spectrometer,the signal to noise ratio of the instrument and other important performance parameters.Therefore,researching the signal detection module with low noise and high signal-to-noise ratio is one of the key issues in the development of the FTIR infrared spectrometer.This paper describes the composition and working principle of the FTIR infrared spectrometer,and analyzes the characteristics of the output signal of the interferometer,which lays a theoretical foundation for the subsequent circuit design and spectrum measurement.Secondly,the signal processing flow of the FTIR infrared spectrometer is analyzed.On this basis,the important role of the receiver signal reception and conversion is studied.After the above-mentioned theoretical research,the laboratory-developed FTIR infrared spectrometer was taken as the research object,and the operating characteristics and signal output of the spectrometer in the spectrometer were analyzed,which provided the initial conditions and index allocation for the subsequent circuit design.Based on the theoretical basis of the design,a weak signal detection circuit based on narrow-band filtering is proposed.The circuit design is developed from the weak signal detection method combined with the low noise circuit design,and the noise performance of the circuit is established by the equivalent noise model analysis circuit.The simulation of the circuit using MATLAB/Tina software shows that the circuit is in The band has a constant gain and group delay,which can realize the non-distorted amplification of the weak interference signal.For testing the performance of the detection module,the performance of the detection module is analyzed by an oscilloscope.The signal generator is used as a signal source.The noise and amplification performance of the detection module are observed through an oscilloscope,and compared with the actual calculation value.Finally,the designed circuit is applied to the Fourier transform spectroscopy detection system and tested at room temperature,and the test results are compared with the results obtained by the foreign detection module.Experimental results show that the detection circuit based on narrow-band filter design can theoretically have an adjustable gain of 60?120dB,which can effectively suppress the noise and detect the micro-variable AC signal of the order of 10-6A,which has certain reference significance.