Research And Applications Of Signal Acquisition And Trackingin GPS Softwar Ereceiver

With the rapid development of the Global Positioning System (GPS), the algorithm research of GPS signal receiver is paid more and more attention in the industry.GPS Software Receiver base on software radio, which has many excellent features such as its programmable, easy to modify, modularity, the algorithm adaptability and scalability, became a research hotspot in the field of satellite navigation recently. Acquisition, tracking and PVT solver algorithms, which are the key technologies of software receiver, play a vital role to the performance of the software receiver. The research of these key algorithms can provide references for our own developed Beidou navigation receivers.This paper focuses on the correlation algorithm study of capture and track in GPS receiver. Firstly, this paper introduces the components of GPS satellite positioning system and the basic positioning principle, describes the composition of the satellite signal and modulation. Achieve a GPS signal source with controllable parameters in matlab/simulink platform for modeling and simulation, using this source to test and verify the algorithm of acquisition and tracking. Then the paper introduces software and hardware receivers, and analysis the basic working principle of the receiver. Secondly, the principles of GPS signal acquisition and tracking are analyzed in detail. Time domain and frequency dual parallel acquisition algorithm are put forward. The algorithm using a parallel search method in the frequency to search the Doppler frequency shift for a one-time and using multiple-correlator to search C/A code phase shift for multi-point in the time domain. According to double-parallel manner by reducing the search the number of units, thereby increasing search speed capture. Meanwhile, the capture search strategies of variable length-fixed length joint detection method are put forward. The search strategy based on variable length detection method and supplemented by fixed-length. This strategy is a good method which effective saving search time while avoiding search into the loop effectively saving search time capture special circumstances; Then achieve modeling and simulation in matlab/simulink platform. Finally, the algorithm is extended to the GPS software receiver. A software receiver is implemented using the C++language and combined with object-oriented thinking.