Gps Receiver Baseband Signal Processing Technology Research

With the influence of U.S.GPS technology in many aspects of social influence, and the consummation of China’s second generation beidou navigation satellite system, the military paid close attention to precision weapons. Guided artillery shells not only fired by the artillery as shells, but also were able to accurately capture the target as missiles. It made the GPS technology have more great strategic significance.Based on the analysis of the GPS principle and the related theory in the background, the24channels of12roads correlator was designed by the serial sliding related algorithm. Each module of the correlator was designed by VerilogHDL, includes Carrier NCO module, code NCO module, C/A code, the complex variable frequency, phase rotation points related to reset the device, frame synchronization, time base generator and serial transceiver module. Use Altera Corporation QuartusII software that comes with waveform emulators and embedded logic analyzer, verify the correctness of each module of the correlator.The processing of the baseband signal was realized by designed the DSP software. The designs includes the forecast of the GPS visible star, the initialization of each channel according to the height angle of the visible stars and the distribution of the satellite number, the gain of the FPGA input code of related accumulated value, the differences contrast between threshold and the related value, the carrier NCO and FPGA code control word of the NCO was changed according to the size and direction of the differences.The intermediate frequency data was acquired by the USB Blaster, then the date was simulated by matlab, the view of the related peak of the captured and not captured satellite through the simulation. The performance of the receiver static was tested by the external antenna, the captured position performance of the receiver in different dynamic trajectories by the indoor simulator.