Research On The Acquisition Of BOC And Its Derived Signals In Interference And High Dynamic Environment

With the continuous development of Global Navigation Satellite Systems(GNSS),more and more satellite navigation systems have been developed,which makes the navigation frequency band become more and more crowded.In order to solve the problem,the Binary Offset Carrier(BOC)and its derived signal has been proposed because of its characteristics that can achieve spectrum sharing.But the actual communication environment is very complex,such as interference environment makes the signal waveform distorted,high dynamic environment makes the received signal have first or second order Doppler frequency,which brings difficulties to the acquisition of BOC and its derivative signal.Therefore,around these problems,the main work of the thesis is as follows:(1)Aiming at the problem of difficult acquisition of CBOC signal in Sinusoidal Frequency Modulation(SFM)interference environment,an acquisition algorithm based on Discrete Sinusoidal Frequency Modulation Transform(DSFMT)and sub correlation function is studied,the algorithm first suppresses SFM interference by DSFMT,then divides the locally constructed CBOC signal into N groups according to the multiple of the chip,then Correlate the N groups of sub-signals and the suppressed received signal to obtain N groups sub-correlation functions,finally,synthesizes a fuzzy-free acquisition function according to algebraic relations.Experiments show that this method can achieve unambiguous acquisition of CBOC signal under SFM interference,and the greater the number of groups,the higher the acquisition accuracy.(2)Aiming at the problem of difficult acquisition of BOC signal in SFM interference environment,an acquisition algorithm based on DSFMT and partial matched filter-all phase fast Fourier transform(PMF-ap FFT)is studied.Firstly,the algorithm estimates the modulation frequency of SFM interference through FFT,and carries out DSFMT based on the estimation of modulation frequency to realize interference suppression.Finally,PMF-ap FFT method is used to acquisition the BOC Signal after interference suppression.Experiment analysis and simulations show that this algorithm greatly simplifies the computational complexity of traditional DSFMT without affecting its performance.(3)Aiming at the problem of difficult acquisition of BOC signal in the high dynamic environment.An acquisition algorithm based on average processing and all-phase Fractional Fourier Transform(ap FRFT)is studied.Firstly,the processed received signal sequence and the local combined spread spectrum code sequence are processed by F point average processing.Then,the two sequences after average processing are correlated.Finally,by detecting the spectral peak output of the ap FRFT algorithm,the estimated code phase,Doppler frequency offset and Doppler rate of change can be obtained to complete the acquisition.Simulation experiment shows that,average processing greatly reduces computational complexity without consuming additional hardware resources.(4)Aiming at the problem of difficult acquisition of high-order DBOC signals in the conditions of SFM interference and high dynamic coexistence,An acquisition algorithm based on DSFMT combined with discrete polynomial phase transform(DPT)and linear frequency modulation Z transform(CZT)is studied.Firstly,SFM interference is suppressed by DSFMT,and then the algorithm determined how to process the signal according to the dynamic order obtained by the order operation.Finally,the CZT algorithm is used to accurately acquisition the processed signal.