Research On FPGA-based TDLAS Signal Processing System

The signal processing of tunable diode laser absorption spectroscopy(TDLAS)is limited by the limitations of the software platform,and in some cases its processing speed and accuracy cannot meet the requirements of use.Therefore,based on the basic knowledge of spectroscopy,this thesis deeply studies Lambert Beer's law,combined with wavelength modulation technology and harmonic detection technology,and proposes a TDLAS signal processing scheme based on field programmable gate array(FPGA).In order to realize the signal processing in TDLAS,it mainly starts from two aspects: one is signal modulation,that is,the modulation wave generation circuit is built based on FPGA,and the modulated wave is sent to the voltage-controlled constant current source after a series of processing,thereby performing laser on the laser.On the other hand,the signal is demodulated,that is,the signal demodulation circuit is constructed based on the FPGA,and the demodulation circuit quickly finds the signal containing the gas concentration information from the signal superimposed with a large amount of noise,and obtains the gas concentration therefrom.After completing the system as a whole,test the driver part and the demodulation part.In terms of current drive,the drive current can reach up to 224.67 mA,and the linearity is good in the normal working range of 15-210 mA.The average accuracy error is 0.32 mA,and the stability ? is 0.017%,which satisfies the driving requirements and demodulates the signal.On the other hand,the average relative error of the harmonic amplitude is 3.14%,which can realize the detection of harmonics more quickly and accurately.