| Human health and production activities are closely related to the earth’s atmospheric environment,and the aerosol present in the atmosphere can break the relative balance of the geo-gas system,which has a great impact on people’s lives and production.Obtaining the physical and optical characteristics of atmospheric aerosols using lidar technology has become a research hotspot in the field of atmospheric monitoring.However,due to its fixed emission wavelength and large detection blind zone,the observation of low-level aerosol characteristics with multi-wavelength is restricted.Therefore,this thesis studies the LED light source radar with rich wavelengths and small detection blind zone.First,in order to study the performance of white LED light source radar system in detecting low-level atmospheric aerosols,further analysis and experimental observation studies were carried out on the system.In the system structure,the use of high-power white LED as the detection light source improved the performance of the light source;at the same time,so as to study the optical efficiency of the four-channel detection system,the efficiency analysis of the four-channel spectroscopic system was carried out;a four-channel synchronous acquisition system was designed to achieve synchronous real-time acquisition of four echo signals.In data processing,for the multi-channel echo signals,the design of multi-wavelength extinction coefficient inversion algorithm was completed by using the Fernald forward integration method.For obtain more information about the size distribution of aerosols,based on the regularization and averaging method,a particle spectrum inversion algorithm was designed.Observation experiments under different weather condition were carried out in Xi’an area,real-time echoes of multi-wavelength aerosols in the lower atmosphere were obtained,and data processing algorithms were used to retrieve the aerosol extinction coefficient,effective radius of particles and volume concentration with the detection height.The inversion results are consistent with the actual weather condition,which verifies the feasibility of the radar system to detect aerosols in the lower atmosphere.Secondly,for reduce the size of the radar system and realize the portable observation of low-level aerosols,this thesis proposed a new portable LED radar system.Based on the principle of radar detection,a coaxial transmission and reception system was designed,and the distribution characteristics of geometric overlap factor at different distances were analyzed;to clarify the situation of the utilization rate of light energy and the divergence angle of the outgoing beam affecting the detection capability of the radar,the structure of the radar optical system was simulated using ZEMAX software;its maximum detection capability was analyzed by calculating the signal-to-noise ratio of the system.Based on the above simulation results,an optical path system was built,the actual diameter of exit spot and divergence angle were measured,and the furthest detection distance was further evaluated.On this basis,the construction of the integrated radar system was completed,the preliminary test experiment of the radar system was carried out,and finally the reflection echo curve of the building at a distance of 300m from the radar system was obtained.Preliminary results show that this portable radar system can effectively receive echo signals carrying distance information. |
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