Research And Design Of GPS Receiver Baseband Processing

Global Positioning System is considered as the most important position navigation and timing development. The key of GPS application is the receive device– baseband processing unit, including two parts: acquisition and tracking loop. The research focus on real time baseband signal processing algorithms and hardware realization.This paper realized the GPS software receiver on Matlab platform. The acquisition of GPS signal individually employs time domain serial search and frequency domain parallel search by FFT algorithm. Analysis result shows that frequency domain acquisition by FFT algorithm has a much less computation load. Non-correlated DLL and PLL are used in the GPS signal tracking.By comparing the speed and hardware complexity, this design using the following scheme:1) The acquisition uses frequency domain parallel search by FFT algorithm, average sampled scheme and novel peak search circuit.2) The arctan phase detector based CORDIC algorithm is used in carrier tracking loop and a simple logic to replace the complex loop-up table to achieve carrier DCO.3) Code tracking loop is based on block adjustment strategy when local generated code is not match input signal, by adjusting the input signal to better match the local code.To verify the design, source datas are generated in Matlab using the GPS modulation way. The design is implemented on Xilinx Virtex-4 FPGA and the result shows the design is correct.