Research On Fast Acquisition Algorithm And Tracking Algorithm For Satellite Communication System In High Dynamic Environment

With the rapid development of national defense thchnology,our country will soon launch the first synchronous orbit communications satellite based on the IS-95 standard.It means our country will own the satellite mobile communication system that can provide mobile communication service for military and local completely and autonomously.In the increasingly complex electromagnetic environment,the satellite communications systems are affected by various disturbances inevitably,especially narrowband interference.Due to the time-varying characteristics of interference signal,It has important practical significance and social value to study the detection and suppression technology applicable to the inter-satellite /satellite-ground communicationfor narrowband interference.The stringent needs for communication on-the-move promote the development of high dynamic carrier receiver technology.In high dynamic environment,the doppler effect caused by the carrier relatively high speed and acceleration motion makes signal acquisition and tracking a challenge.The dissertation researches three kinds of technology under the background of satellite communication systems,including narrowband interference detection,fast acquisition and tracking technology.The whole work contains the following three aspects:(1)A novel interference detection algorithm based on adaptive threshold was proposed,in which the MLT data were used to perform interference detection processing based on double thresholds.The results show that proposed algorithm has better performance of interference detection processing,especially at high SNRs,than the other two algorithms,adaptive threshold algorithm and the double-threshold algorithm in frequency domain.The proposed algorithm can reduce the false detection probability without interference and the detection probability of small interference at high SNRs while ensuring the detection probability of interference at low SNRs.The algorithm shows good performance of interference detection at a wide range of SNRs,which has a wider application perspect.(2)A fast acquisition method of applying PMF-FFT is researched in this dissertation.To simplify the control mechanism and improve resource reuse rate,this dissertation study a “segment correlation+FFT” based Multi-Channel Search Architecture for PMF-FFT algorithm.Aiming at the issue of FFT's low resolution,the performance of six kinds of frequency estimation algorithm is compared.Then,an improved frequency estimation algorithm which integrates Rife algorithm and Quinn algorithm is proposed.The theoretical analysis and simulation results show that it can have better frequency estimation accuracy by combining the improved algorithm with the internal algorithm that joint amplitude and phase.(3)To tracking the signal in high dynamic environment,this dissertation investigates a carrier tracking policy based on second-order FLL auxiliary third-order PLL.On the basis of analysising loop error,the optimal loop noise bandwidth is obtained.Then an adaptive noise bandwidth adjustment carrier tracking methods is introduced.Focused on the weakness of the introduced methods,some inproving advice is given.Finally,a more suitable carrier tracking scheme for system model is designed,which uses channel estimation method and FFT to tracking the signal carrier.Studies show that this method can effectively complete the carrier peel and has a easier implement.