Research On Optical Mechanical Structure Design Of Laser Communication System For UAVs

With the development of unmanned aerial vehicle(UAV)and wireless laser communication technology and the continuous maturity of related devices,UAV laser communication is widely used in the fields of mapping,reconnaissance,event broadcasting and disaster area communication recovery due to its advantages of high rate,high capacity,good confidentiality,simple deployment and flexibility.However,the effects of factors such as atmospheric absorption,atmospheric turbulence and pointing errors can have a significant impact on the performance of UAV laser communication systems.This paper first analyses the composition,working principle and key technologies of the UAV laser communication system,while the influence of the atmospheric channel on the laser transmission is investigated and the effect of atmospheric turbulence effects on the system performance is further discussed.Secondly,the laser communication optical system is designed,and the key indicators of the optical system,such as wavelength,aperture,beam divergence angle and field of view,are analyzed,and the design of the optical system of the laser transmitting branch,tracking and capturing branch and communication receiving branch is completed,and the optical system is analyzed for stray light using optical simulation software.Thirdly,the overall structure of the laser communication terminal was designed and researched.Considering the factors such as the volume,weight and power consumption of the terminal,the structure of the terminal is selected as the oscillating mirror type structure,and the method of using perforated mirrors instead of beam splitters is proposed to optimize the overall structure of the terminal.According to the structural characteristics of the oscillating mirror type terminal,the beam pointing characteristics are analyzed,the Hoyt distribution pointing error model is established and the probability density function expression for the joint channel is derived.Finally,the pointing characteristics and tracking performance of the UAV laser communication terminal were tested.The analysis of the experimental results shows that the UAV azimuth and pitch pointing error angles conform to a normal distribution,their mean values are 0,the standard deviations are 0.4° and 0.05°respectively,and the overall pointing error angles conform to a Hoyt distribution.The experimental results match well with the simulation results and prove the correctness of the pointing error model.At the same time,it is measured that the tracking error of the system is125 μrad can meet the requirements of communication.This paper has optimized the design of the UAV laser communication terminal so that it can be adapted to the UAV platform on board,and establishes a pointing error model that is more in line with the actual UAV platform,providing a theoretical and experimental basis for the design of the UAV laser communication system and the suppression of pointing errors,which is of great practical guidance.