Research And Implement On Precise Code Acquisition Technology In BD-2 System

As the second generation precise navigation satellite timing and ranging system, BD-2 (Beidou-2) system is developed independently by China. Satellite navigation and positioning industry develops rapidly in recent years. Researching on BD-2 system plays an important role in the development of the Chinese satellite navigation and positioning industry.Fast acquisition of precise code is a crucial technology in BD-2 system. To some extent, the acquisition performance determines the positioning precision of BD-2 system directly. There has been much extensive and in-depth research in this area up to now. Because both the doppler shift of the carrier frequency and the phase of the PseudoNoise (PN) code need to be captured, the whole acquisition process is a two-dimensional search process. In BD-2 system, precise code (P code) has high code rate and long sequence period, which results in the difficulty in the acquirement of P code. Consequently, direct acquisition of P code is a very important and useful technology. A joint P code acquisition method which combines time-domain averaging and frequency-domain average periodogram is proposed in the thesis. On the basis of the CCPAZP-FFT (Circular Correlation by Partition And Zero Padding) scheme, the proposed method introduces both the time-domain averaging algorithm and the improved frequency-domain average periodogram, and therefore converts the two-dimensional acquisition process into a parallel one-dimensional process, as a result of which, problems including huge computation complexity, low system processing gain and scallop loss are solved. The structure and the performance of the proposed acquisition method are investigated thoroughly in the thesis. Simulation and analysis results show that the proposed method can efficiently complete the acquisition process of the precise code.In addition, in this thesis, the digital circuit board of the BD-2 satellite receiver is designed and implemented. Each circuit module is designed concretely and tested successfully. The receiver provides a hardware platform for direct acquisition of the precise code. Finally, the P code acquisition is implemented on this BD-2 receiver platform. The implementation result verifies that the proposed joint acquisition algorithm is applicable in the capture of the precise code.