Research And Implementation Of Boc Signal Capture Technology

With the development of satellite navigation systems and the construction of newnavigation systems, the interference between navigation signals becomes more andmore seriously, wheras, the original modulation method has been unable to meet therequirements for higher positioning accuracy and better anti-interference performance.The BOC modulation method, as a new modulation, has begun to be applied in thenew generation of satellite navigation systems. BOC modulation signal has asignificant splitting spectrum feature, which is compatible with the original BPSKmodulation system. Besides, it has higher tracking accuracy and resistance tomultipath interference performance. BOC modulation has been applied widely, and itssynchronization technology has attracted the attention of the majority of the scholars inthe world.This paper first introduces the overview of the development of global navigationsatellite system and BOC modulation, discusses the current research status and makes adescription of the purpose and significance of this study.Then a multi-carrier model for splitting spectrum features of the BOC signal isproposed. The model could make the splitted spectrum superimposed on the basebandwhen downconversion, which could produce a new signal with only one autocorrelationpeak. The doppler frequency and code phase search of the new signal is same with theBPSK modulation signal. Parallel code acquisition is introduced to reduce thecomputational complexity, and a segmented FFT algorithm is proposed to adapt to thesituation that DSP could handle by using limited points of FFT. In order to improve theSNR(signal to noise ratio), we introduced an ingenious differentially coherentintegration method.At last, a DSP-based BOC signal acquisition scheme is designed. According to theselected DSP features, the scheme designed a FFT processor which is different to thetraditional FFT algorithm. We also designed three correlators based on parallel codeacquisition principle and segmented FFT algorithm. In the end of the paper, the schemeis tested on the DSP, and the result shows that the scheme is feasible, and has high detection probability and needs short acquisition time.