The Research And Process About Baseband Signal Of GPS/BDS Dual-mode Software Receiver

GNNS means a global navigation satellite system.GNSS combined with the satellite technology,communications technology,subject of geophysics in the field of navigation.It’s appearance has brought great convenience and intelligence experience to our modern society.It can provide full-time for the user to any area of the global high-precision navigation and positioning services,The current mainstream of various navigation systems’ s development is in conjunction with GPS as far as possible.The BDS is an independent research and development GNNS system operationed by China.Multimode receiving terminal has obvious advantages than single-mode terminal:it can forma compatible and complementary system that combine several positioning systems,increased the number of the visibled satellites to improved the positioning accuracy and positioning performance.Due to the software receiver can programming and update easily and greatly reducing the cost and resources,this study focused GPS/BDS dual-mode signal and proposed a research about realizing the dual-mode software receiver on the Matlab platform.Firstly,this paper describes the status of development of a global satellite positioning system, and elaborates the signal format of BDS/GPS satellite navigation data.Then,it gives a brief description of the receiving terminal and the basic working principle of spread spectrum communication and the algorithm of Baseband acquisition and tracking about the GPS/BDS dual mode receiver.In the signal acquisition process,we use parallel code phase acquisition algorithm based on FFT;In the tracking process,by combinating DLL and PLL to get the output of GPS/BDS signals tracking.After that,this paper introduces principles of navigation message demodulation and using UKF method to solve location.Finally,using the above method to proposal the actual acquisition of dual-mode signal on the Matlab platform,according to the simulation analysis and discussion we come to an conclusion:the GPS/BDS dual-mode software receiving terminal has smaller deviation and higher accuracy on the result of positioning than the single ode receiving terminal.