Technique Of Coherent Doppler Wind Lidar Based On Pulse Coding Modulation

As a fundamental parameter of meteorology and aerodynamics,atmospheric wind field is closely related to people’s daily life and industrial development.Accurate atmospheric wind field detection plays an important role in scientific research and engineering applications.Due to the high spatial and temporal resolution,high retrieval accuracy,and long detection distance,coherent Doppler wind lidar has become widely verified in atmospheric detection applications.However,capturing small-scale complex flows in the flow field remains a huge challenge,and there is an urgent need for meterlevel range resolution wind lidars.For single-pulse coherent wind lidar systems,it is necessary to improve spatial resolution by shortening the pulse width.As the pulse width is short,the degradation of carrier-to-noise ratio caused by limited peak power in fiber lasers makes it difficult to further improve the spatial resolution of traditional coherent doppler wind lidar.In this paper,a coherent Doppler wind lidar based on pulse coding with high spatial resolution by increasing the pulse repetition rate.modulation is developed to improve the wind field measurement accuracy.The article is mainly divided into three chapters.The first chapter is an introduction.This chapter introduces several main measurement methods of atmospheric wind field.The history and corresponding research progress of coherent Doppler wind lidar and pulse coding technology at home and abroad are reviewed.Chapter 2 is the basic principle of pulse coding coherent Doppler wind lidar.It is divided into two parts,the basic theory of coherent Doppler wind measurement and the theory of pulse coding technology.The former includes the basic theory of Doppler wind lidar,a carrier to noise ratio formula for coherent Doppler wind lidar is given based on the principle of coherent heterodyne detection and lidar equations,.The latter is based on the autocorrelation characteristics of complementary correlation coding.Through theoretical derivation and simulation,the feasibility of coherent Doppler wind lidar based on pulse coding technology is verified.Based on the simulation results,two important factors are proposed that currently affect the performance of pulse coding coherent Doppler wind lidars,frequency domain crosstalk and pulse non-uniformity.Then the corresponding preliminary solutions are given.Chapter 3 is the research on key technologies of pulse coding coherent Doppler wind lidar.The first part is an introduction to the basic pulse coding coherent Doppler wind lidar system.According to the simulation parameters,a pulse coding coherent Doppler wind lidar system is built through experiments,and then compared with a single pulse coherent wind lidar.The second part we optimizes the frequency domain crosstalk problem and proposes an active field of view adjustment technique based on deformable mirror adaptive optics.In the third part,technique based on M-sequence coding is proposed to optimize the system for the non-uniformity of amplified pulses.Through experiments and research on two key technologies,the system error and method error of pulse coding coherent Doppler wind lidar are suppressed,and the practicality and reliability of the system is verified.