Research And Realization On Unambiguity Tracking And Acquisition Technology Of Bei Dou BOC Signal

With the completion of the comprehensive network of Bei Dou third-generation satellites,the development of the Global Navigation Satellite System(GNSS)has become the focus of extensive attention.However,with the increase of the number of satellites,satellite signal channels become increasingly congested,and the mutual interference between signals has become the main factor that restrains the development of GNSS,and it has also become an urgent problem to be solved in the development of GNSS at present.In this regard,Binary Offset Carrier(BOC)system is adopted as the new modulation method of satellite navigation signal for Beidou third-generation signals.On the one hand,BOC signals have the characteristics of spectrum separation,which can make better use of frequency band resources between different satellite navigation systems.At the same time,BOC signal has two independent modulation parameters,and the design of different parameters weakens the mutual interference between signals.On the other hand,the autocorrelation function of BOC signal contains multiple correlative edge peaks.In the process of receiver synchronization,it is very easy to lock mistakenly on the coherent edge peak,which leads to error location.In view of the above background,this dissertation carries out the research and implementation of the non-ambiguity acquisition and tracking technology of the Beidou new system BOC signal.The main research contents of this dissertation are as follows:First,the modulation technology of navigation signal is introduced,including the traditional BPSK modulation and the new BOC modulation,as well as the modulation principle and waveform transformation of the two modulation modes.At the same time,due to the particularity of BOC signal,a series of different modulation systems are derived,such as MBOC and Alt BOC modulation.The spectral function and correlation function of BPSK and BOC modulation are compared through the simulation results,which provides a theoretical basis for the main research content of this dissertation.Second,starting with the introduction of capture principles and capture methods,this dissertation systematically describes the capture process of traditional navigation signals.Based on the principle block diagram and the capture results,three peak elimination algorithms,BPSK-like,SCPC and ASPe CT are introduced,which are suitable for BOC signals.Aiming at the problem of incomplete peak elimination of typical algorithms,a new acquisition algorithm is proposed.The new algorithm is based on dividing the local BOC(n,n)signal into four segments within a subcarrier period using a time domain controller,and then generating a branch correlation function after being correlated with the received signal.The branch correlation function undergoes a series of reconstruction processes,so as to completely eliminate the influence of the side peaks.The proposed algorithm can completely eliminate the edge peak interference under different phase sub-carrier modulation,and the generated signal only retains the narrow correlation peak.Third,with the introduction of tracking principle and tracking loop as the guide,the tracking process of traditional navigation signal is discussed.Furthermore,the concept of subcross-correlation function is proposed,and the shifting cross-correlation function is used as an auxiliary signal to eliminate the tracking ambiguity of BOC(kn,n)signals.This method can effectively alleviate the multimodal problem of BOC signals,and retain narrow correlation peaks,and at the same time show more excellent phase discrimination and anti-multipath performance.In addition,a new edge peak elimination method for sin-BOC with different modulation orders is proposed.Compared with the typical methods,the proposed method has a certain degree of improvement in the efficiency of edge peak elimination,detection probability and peak-to-average ratio.Finally,on the GNSS receiver hardware platform,the main logic modules in the receiving circuit are designed,including the intermediate frequency carrier removal module,the local signal generation module,the correlation accumulation module and the maximum value decision module.At the same time,the signal processing flow and logic unit module are described in detail,and the logic module is verified by simulation whether it conforms to the design.