Research On Fast Synchronous Acquisition Techniques Of Beidou Signal Of Hypersonic Aircraft

BOC modulation signal has the advantages of friendly coexistence of spectrum,strong anti-interference ability,and good anti-multipath performance,so that it has developed rapidly in the field of satellite navigation and positioning system.With the popularization of satellite systems,higher requirements have been put forward on the acquisition performance of satellite navigation and positioning signals.Recently,rapid acquisition of satellite signals based on BOC modulation has been in-depth research.With the rapid development of high-speed vehicles such as cruise missiles,spaceship,deep space probes,spacecraft,and supersonic drones,the acquisition of BOC-modulated satellite signals in a high dynamic environment has attracted much attention from domestic and foreign scholars.The BOC modulation signal realizes the secondary modulation of the signal,so it has strong anti-interference and anti-multipath performance,but exhibits multimodality at the same time,which enhances the ambiguity of code synchronization.At the same time,the high dynamic environment will produce larger Doppler frequency shift and code phase shift,which will have a certain impact on the performance of the acquisition system.In order to achieve the purpose of high detection probability and low average acquisition time,this paper is based on the study of time-domain serial search,FFT-based parallel search in frequency domain,and least squares algorithm,proposed the fast acquisition optimized algorithm based on PMF-FFT and FFT-based across asynchronous symbol partial matched filtering method(FFT-PMFAAS),realizes accurate estimation of frequency offset and code offset,achieves the purpose of fast acquisition of BOC modulated satellite signals in a high dynamic environment.The main research content includes:1)Conduct research on the signal acquisition mechanism of BDS,explained the basic principles and signal characteristics of DSSS modulation signal and BOC modulation signal,analyzed the auto-correlation characteristics of the BOC modulated signal during the synchronization acquisition process and the main factors affecting the maximum correlation peak during the synchronization acquisition process.2)Explained the basic principles of time-domain serial search and FFT-based parallel search in frequency domain,and discusses its performance,analyzes the influencing factors of satellite signal acquisition accuracy,and explores the evaluation of acquisition performance standard.3)Aiming at the problem of Doppler frequency shift introduced in a high dynamic environment,used the least square algorithm cleverly,and proposed the fast acquisition optimization method based on PMF-FFT.Based on the performance of the PMF-FFT acquisition method,the rough estimation of Doppler frequency shift is effectively optimized.Given the theoretical framework and derivation of the acquisition algorithm,and analyzed the performance of the fast acquisition optimized algorithm based on PMF-FFT through simulation experiments.4)Aiming at the Doppler frequency shift problem introduced by the high dynamic environment,conduct research on the FFT-based across asynchronous symbols partial matching filtering fast synchronization method.Proposed the asynchronous symbol correlation accumulation method and used in the correlation matching process between the local copy signal and the received signal.Enhanced its autocorrelation value and further reduced the probability of false acquisition,thereby ensuring a greater probability of acquisition.Compared the performance and analyzed the pros and cons of the proposed algorithm.