Design And Realization Of GPS Pseudolites

GPS can provide us location,speed and time with high precision. Nowadays, it has been widely used in many fields; especially in military field, and it has become a kind of main navigation method. But, its high precision, reliability and integrality depend on the number of visible satellites and their geometrical distribution. GPS satellites may become unuseful when signals are obstructed. In worse conditions, such as mine areas, tunnels and some places indoors or underground, GPS receiver can hardly receive the signals from the satellites. The signals are too weak to be used for positioning. In this case, pseudolites can solve this problem.This paper investigated the technology of GPS pseudolites system. Firstly, it summarized the development, the present state and the existing problems of satellite navigation system. And then it presented the research and development of GPS pseudolites. During the description of GPS pseudolites system, the basic function of pseudolites emitter was also introduced. And the paper gave us a detailed account of the transmission link.A kind of pseudolites emitter was designed on the basis of theory study and analysis. The system linked RS232 with the central computer, and it used the advanced SOPC technology. In addition, it used FPGA platform. C language and hardware describe language were used to control signals generator and IF modulation. The signal's frequency band were moved to GPS RF. At last, signals were emitted by the antenna.