Research On Signal Processing Algorithm And Data Acquisition System Of Phase Modulated Lidar

The phase modulated laser Doppler frequency shift measurement method can take the advantages of both direct detection and coherent detection,and has a good development prospect.However,due to the late appearance of phase modulation Doppler frequency shift measurement method,the research in some aspects is not perfect,especially its dynamic measurement range is low,which is difficult to meet the actual measurement needs.In addition,due to the lack of research on phase modulated Doppler lidar,there is no data acquisition system matching this method.Based on this,this paper mainly carried out the following two works: first,to improve the dynamic range of the phase modulation Doppler frequency shift measurement method,a new signal processing method was proposed,and the correctness of the method was verified;second,the corresponding data acquisition system was designed for this signal processing method,and the hardware part of the system was designed,which was verified by experiments The system can meet the design requirements.In this paper,the "star trace" vector method is proposed to measure the Doppler frequency shift of the phase modulated signal light.This method uses the changes of all the frequency discrimination parameters in the AC and DC components of the phase modulated signal in the two-dimensional or three-dimensional coordinate system to realize the frequency shift measurement.This method not only has the advantages of high accuracy of coherent detection,but also has the advantages of simple direct detection structure and strong environmental adaptability The advantage of this method is that it can increase the dynamic range of measurement by about 10 times,and the correctness and validity of this method are proved by experiments.In this paper,the data acquisition system of the back-end of the phase modulated Doppler lidar is also studied.The design and implementation of the system are mainly described from the aspects of overall scheme design,hardware selection,FPGA logic design and LabVIEW application development.FPGA is the core controller of the whole system.It uses ad device to complete the signal data acquisition,uses USB2.0 to realize the real-time transmission control between FPGA and upper computer,selectsthe type of each module device of the system,and uses the relevant design and development software to program.Through the hardware test and software simulation of each module,the whole system is finally coordinated and verified that the system conforms to the The requirements of data acquisition system of phase modulation Doppler lidar.