Research On The Key Technology Of Space-borned ADS-B

ADS-B system has become one of the hotspots in the field of aviation surveillance in recent years because of its huge civil value and potential military value.With the vigorous development and maturity of space technology,especially micro-satellite technology,satellite-borne ADS-B system based on micro-satellite platform provides the possibility for large-scale,all-weather,all-time aviation monitoring tasks,and has the obvious advantages of low cost,rapid assembly,testing,launching,application and easy maintenance and upgrading.Compared with the traditional ground ADS-B system,the satellite-borne ADS-B system has the characteristics of wide coverage,but it also has the problems of serious multi-signal conflict and low signal-to-noise ratio when receiving ADS-B,which seriously restricts the performance of the system.Aiming at the above problems,the characteristics of receiving ADS-B signals on satellite are analyzed in detail in this paper.Based on "Tiantuo 3" satellite-borne ADS-B load,how to improve the receiving performance of the system is emphatically studied.The main works of the paper are as follows:Firstly,the characteristics of satellite-borne ADS-B system are studied,the detection probability model of the system is established,and the on-orbit reception of the ADS-B payload on Tiantuo-3 satellite is analyzed briefly.Based on the related technical standards of ADS-B system,the attenuation and fading of ADS-B signals in the atmosphere,Doppler shift and signal link budget are analyzed.Based on Aloha protocol,a signal collision model for single-beam and multi-beam reception is established.The problem of channel co-channel interference is analyzed.The relationship between detection probability and user requirements is given.This paper analyzes the work of Tiantuo-3 satellite-borne ADS-B in orbit for three years,and points out the direction for improving the receiving performance of the system.Secondly,the key technologies to improve the performance of satellite-borne ADS-B detection are studied from three aspects: receiving antenna and beam design,phased array receiving and efficient demodulation algorithm,and aliasing signal separation.(1)Antenna design and beamforming technology for Spaceborne ADS-B receiver are studied.Starting from the global aircraft surveillance mission in 2020,the requirements of receiving antenna and beam number for Spaceborne ADS-B system are analyzed.An adaptive multi beam forming algorithm based on global aircraft density distribution is proposed.This method optimizes the coverage of multi-beam by analyzing the global aircraft density,and then controls the amplitude and phase of each array element in the phased array antenna to form a specific direction and size of the beam,which improves the probability and level of clockwise detection,while maintaining the wide coverage of the spaceborne ADS-B system.(2)Research on Spaceborne ADS-B receiver technology.Aiming at the serious attenuation and low SNR of satellite-borne ADS-B signal,a high sensitivity satellite-borne ADS-B receiver scheme is proposed,with emphasis on the demodulation algorithm.The receiver hardware uses high reliability and low power devices,using three-stage low noise front-end amplification,custom narrow-band IF filter and low noise local oscillator to reduce the receiver noise coefficient.In the demodulation algorithm,the frame matching filtering algorithm with joint data bits is used to improve the accuracy of signal detection and bit timing.Bit decision method based on multi-point amplitude sampling method and data error correction method based on confidence are used to further reduce the requirement for signal-to-noise ratio.(3)The blind separation method of spaceborne ADS-B overlapped signals is studied.Aiming at the problem of unavoidable signal collision,a blind signal separation method based on array antenna and single antenna is studied.Firstly,the feasibility of space-borne ADS-B collision signal sorting based on array antenna is analyzed,as well as the requirements of collision signal power and direction.Secondly,considering the limitation of the number and size of receiving antennas on micro-satellite platform,a blind separation method based on power difference sorting and reconstruction cancellation sorting is proposed to separate two conflicting signals,and the effectiveness of this method is verified by simulation analysis.