Design And Implementation Of Baseband Signal Processing Of Beidou System Receiver

BeiDou satellite navigation and positioning system developed by China is satellite navigation and positioning system with two-way communication, real-time navigation and precision timing characteristics. It has been widely used in national defense, communications, construction and other economic areas.This system is based on direct sequence spread spectrum(DSSS)technique. In DSSS system,if the synchronization of Pseudo Noise Code is very bad,exact information do not received. So, it affects the performance of the whole system, because this technology is not only the precondition of working well, but also the key of precise positioning。In this paper,we based on the process of research and development of BD navigation receiver. First of all,we introduced the spread spectrum and m-code,and especially do research of DSSS.Then the composition, trait, and signal structure of BD system is analyzed. We especially discussed the baseband signal processing of BD system. According to the characteristics of BD satellite and modulation mode and navigation message protocol request, we choose the sliding related law(with a fixed threshold) to realize the PN code capture, Code tracking loop adopt double jitter loop, Doppler tracking using carrier Costas loop.The paper proposed the design scheme of base band module adopt bulky resources of FPGA.We use the software of Quartus II to make the design of capturing and tracking. The test result indicates that the design can satisfy the BD system design wants and proves the validity and feasibility of the project.