Design And Realization Of GPS And Pseudolite Software Receiver

GPS provides accurate location, speed and time information to global users, so it is applied widely to aviation, marine, land and some other fields, especially in military field. GPS's high precision, reliability and integrality depend on the number of available satellites and their geometrical distribution. Furthermore, GPS has still not been used in some areas currently, such as mines, tunnels, indoor or underground. Pseudolites positioning technique is an effective tool to solve these problems..This thesis researchs the technical GPS and Pseudolites, and design GPS and Pseudolites of software receiver. In the course of GPS receiver designing, there are several difficult with modulation processing, including phase noise, mixer and amplifier, fake signal injection inter-modulation, product frequency tuning , thermal noise, intra noise and local oscillator and so on. And pseudo-code spread spectrum communications are analyzed in detail. The composition and characteristics of M sequence, the composition of Pseudolites C/A code, and the format of navigation message are analyzed. Moreover, researching the structure of GPS and Pseudolites software receiver system, and designing the hardware circuit of the GPS and Pseudolites software receiver, which include the RF circuit, baseband circuit, USB circuit, FLASH circuit, SDRAM circuit and S3C2410 circuit. Then the software designate of GPS and Pseudolites software system is researched, which include the systematic program and application program. About Pseudolites research, GPS Pseudolites transmitter is designed based on systemic research and analysis. Navigation messages (D codes) is generated by single chip and C language, C/A codes is accomplished by VHDL language and CPLD chip, at the same time, then, the resultant bit-trains are modulated on the L1 carriers by BPSK mode, the whole function of Pseudolites is realized. In order to validate Pseudolites transmitter, spectrum analyzer, oscillograph and GPS receiver are used to test its signal. The results show that the Pseudolites hardware and software are correct and effective.