Design Of Pseudolite System And Multi-channel GPS IF Data Acquisition Based On FPGA

The pseudolite is a very effective augmentation method, when some position system can not satisfy the positioning requirement. It can not only enlarge the coverage area of the satellite positioning system in complex circumstance, but also enhance the whole system's stability and precision.In this thesis, a 4-channel GPS pseudolite system and a synchronous acquisition system are designed to apply the theory of pseudolite in practice and solve the problem of synchronous acquisition of multi-channel GPS data at the same time without increasing the cost, on the base of theoritical analysis and research. In the first system, the C/A code is generated by FPGA. After code conversion, it is modulated on the L1 carriers by QPSK mode and the pseudolite is finished. In the second one, three-channel asynchronous GPS intermediate frequency data is adjusted to be synchronous by justification, then the data is multiplexed. The multiplexed data is saved into the PC by USB data acquisition and processed to fetch the useful message data with digital demultiplexing. In order to test the pseudolite system, we use the spectrum analyzer, oscillograph and GPS receiver. The result shows that this system is feasible under some circumstance and the design is correct and effective. In the synchronous acquisition system, after the data multiplexed and acquired, we process the data with Matlab. Theory and practical processing results shows that the method has high precision, and it can process digital multiplexing and demultiplexing effectively.