Research On Acquisition Algorithm Of MBOC And Dynamic DBOC Signals

In the limited frequency band resources,as the number of satellite launches increases,interference between different navigation systems will inevitably occur.The proposal of Binary Offset Carrier(BOC)signal and its derived signals provide an effective solution to avoid frequency band congestion.At present,these signals have been used in different navigation systems.However,in the actual communication environment,there are often many interference factors,which increase the difficulty of signal acquisition.Therefore,the research on signal acquisition in the interference environment has been paid much attention by scholars at home and abroad.In this thesis,based on the signal characteristic analysis of BOC and its derived signals,the acquisition methods of Time Multiplexed Binary Offset Carrier(TMBOC)with residual frequency offset,Composite Binary Offset Carrier(CBOC)signal under narrowband interference and Double Binary Offset Carrier(DBOC)signal in high dynamic environment are studied.The work of the thesis mainly includes the following aspects:(1)Aiming at the problem of TMBOC signal acquisition in the residual frequency offset environment,this thesis study an acquisition method that based on Partial Matched Filter-all phase Fast Fourier Transform(PMF-ap FFT)combined with all-phase ratio correction.Firstly,the method performs correlation operations between the received signal and the local combined pseudocode through the PMF process.Then,the pseudo code is captured through the ap FFT process.Finally,combined with the method of all-phase ratio correction to improve the Doppler frequency estimation accuracy.Research shows that the method proposed in this thesis can effectively improve the capture performance.(2)Aiming at the problem of CBOC signal acquisition in a narrowband interference environment,this thesis study an acquisition method that based on all-phase FIR(all-phase Finite Impulse Response,ap FIR)notch filter combined with constructing fuzzy correlation function.Firstly,the method notches the narrow-band interference through the ap FIR notch filter.Then,a set of shape code vectors is constructed in the time domain,and cross-correlation operation is made between the received signal after filtering narrowband interference and the local reference signal formed by the shape code vector.Finally,the non-fuzzy function expression is constructed to eliminate the multi-peak characteristic of CBOC signal autocorrelation.The research shows that the method proposed in this thesis can effectively filter out narrowband interference and construct a single-peak autocorrelation function.(3)Aiming at the problem that DBOC signal is not easy to capture in a high dynamic environment,this thesis study an acquisition method that based on Discrete Polynomial-Phase Transform(DPT)combined with PMF and Fractional Fourier Transform(FRFT).Firstly,the method uses DPT to determine the dynamic order of the received signal.If the received signal contains a second-order Doppler rate of change,it is necessary to use a transient moment to reduce the order of the received signal and then use the PMF-FRFT method to capture.If the received signal contains only the first-order Doppler rate of change,it can be directly captured by the PMF-FRFT method.The research shows that the method proposed in this thesis can effectively realize the signal acquisition under high dynamic environment.