Study On The System Design And Data Processing Algorithm For Coherent Doppler Wind Lidar

With high accuracy of clear air detection, high detection sensitivity, highspatio-temporal resolution, coherent Doppler Lidar has obvious advantages in measurementof atmospheric wind field. As an important means of global wind profilers detection,spaceborne coherent Doppler lidar become worldwide concerned. However, because ofhigh precision requirement in instrument design, high cost and difficulty in the instrumentdevelopment, there has not been a successful launch equipment. Although the domesticreserch institution has carried out some research in coherent lidar, but in general there is alarge gap with foreign countries, especially in spaceborne coherent lidar design anddevelopment. Supported by the pre-research project, this thesis studies on the keytechnology of spaceborne coherent Doppler Lidar and the ground-based verificationsystem.Thesis is mainly divided into two parts. One is for the system design, optimizing, anderror tracing studies, the design scheme of coherent Doppler Lidar system is provied, whichhas important theoretical significance and practical value both for the development ofspaceborne and ground-based coherent Doppler Lidar. The other part is the signalsimulation and data processing studies. The end to end time domain signal generationalgorithm model is established based on the optimization key parameters of ground-basedverification system, and the data processing is carried out based on the data of simulationfrom the signal generation algorithm and the real from all fiber coherent Doppler Lidar.The main innovate research works in thesis are as follows.1) The spaceborne coherent Doppler Lidar system modeling and desgin of the overallindex are compeleted. According to the system structure of coherent Lidar, the calculationmodels of atmospheric transmisson, laser system, transmitter and receiver optical systems,optical detection and data acquisition systems are estabished. The key parameters ofcoherent Doppler Lidar-local oscillator optical power, and the telescope aperture andoptimum truncation factor are analyzed.2) A universal horizontal wind speed and direction error calculation modeling isestablished for spaceborne coherent Doppler Lidar. Based on the total differential and statistical theory, and uing Cramer-Rao lower bound instead of Frehlich’s empiricalformula, a universal horizontal wind speed and direction error calculation modeling isestablished for spaceborne coherent Doppler Lidar. The caculation model is integratedbased on MATLAB and a set of interactive spaceborne and ground coherent Lidar systemperformance optimization and error tracing simulation software is developed. For2μm laserwavelength, a set of system paremeter is designed for spaceborne coherent Doppler Lidarand ground-based verification system.3) The end to end time domain signal generation algorithm model is established.Combined with the feuilleté model and random noise generation algorithm, the timedomain signal is generated, and the reliability is verified under the linear wind shear andturbulence velocity conditions. In the case of linear velocity, the velocity probabilitydistribution function is estabilished to reduce the influence of speckle effects. For thestochastic turbulence velocity, an improved real correlation random wind field algorithm isproposed for real random processes. The validation algorithm flow of the turbulence energydissipation rate is presented. The effect of laser pulse shape on the turbulence recognitionalgorithm is analyzed.4) The data processing algorithm is researched using the real data aquired by all fibercoherent Doppler Lidar system. The expression of signal and noise current for coherentDoppler Lidar with Dual-balanced detector is theoretical analyzed and experimentallyverified. Maximum likelihood algorithm for all-optical coherent Lidar system has beenstudied, the results show that the maximum likelihood algorithm has a higher precision toidentify weak signals than the fast Fourier transform algorithm; In order to suppress thefluctuation, a novel noise modeling by the trend of each range gate has been developed,which using the polynomial PLS to fit the noise floor. According to the real data collected,the comparition to the noise modeling of the tail is analyzed.