Design And Implementation Of Non-line-of-sight Laser Communication Receiving System

At present,the mainstream communication technology has developed very mature,but in some complex electromagnetic environment and some emergency communication occasions,due to its own shortcomings,the application of mainstream communication technology is limited by different,non-line-of-sight laser communication can be used as a useful supplement.Non-line-of-sight laser communication is a way to realize communication by Michaelis scattering or Rayleigh scattering between laser signal and aerosol particles and atmospheric molecules in atmospheric channel.Because of the characteristics of non-line-of-sight communication,non-line-of-sight laser communication can add a possible means of communication for emergency communication and rescue communication in complex environment,and it has broad application prospects.The purpose of this thesis is to design the receiving system of non-line-of-sight laser communication and realize the communication function in the hardware circuit.The specific work is as follows:Firstly,the atmospheric composition and the absorption and scattering of laser in atmospheric channel are introduced.The two scattering principles,Mie scattering and Rayleigh scattering,are described and analyzed.Michaelis scattering is taken as the theoretical basis of non-line-of-sight laser communication.The transmission link model of non-line-of-sight laser communication is established based on single scattering theory.The scattering phase function,asymmetric factor,scattering effective volume and visibility are introduced and analyzed.The formula of the receiving power of non line of sight laser communication system is derived and simplified by introducing ellipsoidal coordinate system.Secondly,according to the deduction formula of the link model,the factors which affect the receiving power,such as the divergence angle of the transmitting beam,the receiving field of view,the transmitting receiving pitch angle and so on,are simulated and analyzed.The feasible scheme and the system performance parameters of the non-line-of-sight laser communication system are determined,and the receiving system is designed.A large aperture and wide field of view antenna is used to receive the scattered signal.The field of view is designed as a sector to reduce the accuracy of pointing in the air.The background light noise is filtered by a narrow band filter.Complete the receiving circuit schematic design and PCB design,using signal threshold and noise threshold dual channel mode of operation,one way to extract laser echo signal,one way to control the power of the detector according to false alarm situation,with high sensitivity avalanche photoelectric detector,suppress noise and improve the detection ability of the receiving system.Design and complete the schematic design of information decoding circuit,introduce the coding and coding technology of information transmission and complete the software programming.Finally,a test platform is built to test the capability of the laser communication receiving system.The communication is stable at a distance of 500 meters and the scattering angle is 54 degrees,with the error rate of less than 1%.The system parameters meet the design requirements and verify the correctness of the non-line-of-sight laser receiving system.