Research On The Key Technologies Of Signal Acquisition For Beidou Satellite

The Beidou satellite navigation system is currently one of the world’s four largest navigation system, it can realize the full coverage in all day time. The Beidou II passive positioning navigation system is an important step in the development of a national strategy compared with the Beidou I system.The Beidou System become development from Asia Pacific region as a center gradually for global coverage of the full time position and navigation system. The system can provide good location navigation and timing services in the development of China’s military, industry, agriculture, fishery, transportation and other industries. Up to now has been one of the global navigation system, keep pace with the GPS system and the United States, Europe and Russia’s GLONASS system. According to the design plan, It can provide all-weather positioning for users from all over the world by 2020.The advantages of satellite navigation system’s are obvious, mainly include: navigation and positioning is not restrictions by geographical location, the receiver can complete the positioning as long as the user can receive satellite signal; due to the adoption of passive mode, the quantity of user is not limited, the system can provide tens of thousands of users to simultaneously complete the positioning and navigation services; but satellite navigation also put forward new requirements for signal acceptance, whether the receiver could received signal and the successful complete the subsequent processing is critical, so it is necessary to further study and improve the signal receiving and processing process.The research focuses mainly on the baseband processing of IF signal, which mainly includes the fast acquisition of the signal, the stable tracking of the signal and the accurate calculation of the position information. The signal acquisition as a primary stage of the baseband signal processing whose result will directly affect the performance of the receiver. Therefore, carry out in-depth study of signal acquisition and enhanced signal acquisition module performance is particularly important.In this dissertation, based on the research project of the Beidou navigation receiver, the signal acquisition process of the receiver is studied. Firstly, the Beidou satellite navigation and positioning system is introduced. Secondly, introduces the basic theory of satellite navigation. Again, make an detailed description focuses on the secondary code in the Beidou signal, together with the performance analysis the related losses. Puts forward several different acquisition algorithms overcome the problems of secondary code. A new algorithm which is based on combining serial and parallel search was presented to extended the coherent integration time so as to achieve acquisition of the weak signal. Firstly,obtain the code phrase of the primary code by serial search within a period of PRN code,and then get the secondary code phase and Doppler shift by parallel search on the entire secondary code,thereby extending the coherent integration time to achieve weak Compass signal acquisition. In addition to, We propose a new algorithm which combine with hierarchical structure of main code of secondary coding BD adopts.To be first,it proceeds parallel capture in the main code level and then achieves the secondary acquisition over The entire secondary code to wipe off the effect of the secondary code on the integration time. So this algorithm can extend the integration time, accordingly improve the sensitivity of receiver. Finally through sampling IF signal in a real environment, achieve a software receiver. Experimental results show the effectiveness of the design of the algorithm compared with the traditional algorithm.