The Research And Implementation Of Spaceborne ADS-B IF Receiver Separation Algorithm

ADS-B(Automatic Dependent Surveilance-Broadcast,ADS-B)technology through the external broadcasting aircraft location,identity,speed and other information,to achieve information sharing and air traffic monitoring.The current ADS-B monitoring system is dominated by terrestrial base stations.Due to the small coverage and high deployment cost of the ground receiving stations,the ADS-B monitoring system can only monitor some of the key areas.With the development of the aviation industry and social progress,people have put forward higher requirements for air traffic control,ground monitoring system is difficult to meet the current needs.The low-orbit satellite system relies on the high degree of satellite advantage,wide coverage,low overall deployment cost,can cover the whole world,compared with the ground ADS-B monitoring system has a greater advantage.However,the satellite ADS-B system is also facing a huge technical problems,the satellite orbit from the aircraft far away,the signal transmission loss;satellite antenna coverage,signal density,there are signal overlap and other issues.In this thesis,we discuss the problem of overlapping signal processing in space ADS-B system.The signal transference probability and the aircraft capacity of the signal are analyzed.The waveform distortion of the overlapped signal is studied.The overlapping signal is separated and processed by the re-trigger technique and the FastICA algorithm,and the detection of the overlapping signal under different conditions is obtained.Finally,an ADS-B 1090 ES overlapping signal separation method based on interference cancellation is proposed and implemented in hardware.Because there is a difference between the 1090 ES signals,the signal is not a simple baseband pulse superposition at the time of overlap,and there is a case where waveform cancellation can occur.In particular,in the case of waveform cancellation,the overlapping signal is seriously disturbed and it is difficult to discern the pulses,resulting in the overlapping signal being unable to be effectively detected.For the overlap problem of the 1090 ES signal,the RTCA DO-260 B recommends a re-trigger technique.Re-triggering technology by picking up high-power signal,discard the low-power signal,can be achieved in a certain power ratio of overlapping signals in the high-power signal detection.The independent component analysis using the independence of the source signal,by solving the solution matrix,you can achieve the separation of the signal overlap.In this thesis,two kinds of overlapping processing techniques are simulated and the detection probability of overlapping signals is obtained under the corresponding conditions.Because of the poor performance of the re-triggering technology and the complexity of the independent component analysis algorithm,this thesis proposes an algorithm of overlapping signal processing based on interference cancellation,which is not only in the high-power signal is successfully detected under the premise of high-power signal Pulse position and waveform and other parameters to estimate,according to these parameters and signal bit information for signal reconstruction.Then,the reconstructed signal is removed from the overlapping signal,resulting in a low power signal.Considering the signal detection performance,algorithm complexity and stability of the three methods,the space IF ADS-B receiver with two overlapping signals can be designed and implemented by using the interference cancellation method.