Direct Broadcast Satellite Signal Interference Type Recognition Technologies

Direct Broadcasting Satellite monitoring system is a Satellite signal monitoringsystem which developed for the protection of the security and stability of the nationalradio and television services.The system has the functions such as satellite signalfull-band scanning,signal analysis and measurement,interference signals alarm andrecognition.At home and abroad,the majority of the satellite signal systems are madefor the interference alarm at present,but there’re less systems made for theidentification of the interference signals when they exist effectively.Access to the typeof the interference signals have great significance for the satellite monitoring stationstaff to locate the source of the interference and eliminate them rapidly and timely.In order to make the system performance more perfect,the thesis analyses thedefects and potential problems of the Direct Broadcasting Satellite monitoring systemand expands some functions on the basis of the original system.The thesis firstoptimize the alarm process of the Direct Broadcasting Satellite monitoring system,thealarm function of the Direct Broadcasting Satellite monitoring system is realized byspectrum scanning module,the scanning module of the system captures the defaultnumber of frames to calculate the average value in the case of signal withoutinterference,then the average value adds or subtracts the threshold to generate thestandard signal up and down template.The real signals compare with the standardtemplate of the signal to distinguish the alarm type when there are interference signalsand then the monitoring system upload the alarm type to the Monitoring Center.But thealarm process of the system has less alarm types and the system is easy to miss ordistinguish error types,in order to solve the problems the thesis optimizes the processof the system detailed;Secondly,according to the carrier frequency estimationalgorithm-the zero-crossing method,the frequency estimation method which is basedon linear fitting,the frequency estimation method which is based on linear phasetransient analysis and the carrier frequency estimation method which is based on powerspectrum proposed by this thesis,this thesis also do actual simulation comparison and error analysis with the carrier frequency estimation algorithmand select the mostsuitable algorithm for the monitor system.Once again this thesis bases on theparameters of the Direct Broadcasting Satellite signal and characteristics of theinterference signals to model the signals and do MATLAB simulation，part of theinterference signals’s mathematical expression are given,at the same time the thesismixes the interference signals and the Direct Broadcasting Satellite signal to test thechange of the time domain signal level for the QPSK modulation signal andfrequency-domain power spectrum、constellation diagram、Vector error EVM toprovide the basis for the identification of the type of signal-to-interference;at last,thethesis designs the broadcast satellite signal interference identification processes whichis based on the characteristic parameters of the interference signal and proposes thealgorithm to identify the type of the interference.Then the thesis do the actualalgorithm validation bases on the Monitor for Electromagnetic environment System toverify the feasibility of the algorithm.The system has been put into use in a monitoring station in Beijing in the engineroom,the project needs monitoring, signal analysis and real-time monitoring,as well asthe identification of the type of interference, the system runs stable,alarms accurate andhas small error signal parameters.