Research And Implementation Of Weak GPS/Compass Baseband Signal Acquisition

The compatibility and interoperability of Compass Navigation Satellite System with GPS ishelpful of developing the localized satellite navigation products. Satellite navigation receiver’sperformance directly affects the service of satellite navigation systems. As a result, the study ofdual-mode GPS-Compass satellite navigation receiver, especially the study of dual-modesatellite baseband signal processing algorithm is the current research focus.Weak GPS-Compass satellite signal acquisition algorithm is studied in this paper. At first, aGPS-Compass dual-mode digital intermediate frequency signal source is designed. Differentparameters can be set to simulate the satellite signal under different environments. Based on thestudy of traditional acquisition algorithm and analysis of the influence in weak satellite signalacquisition, an improved GPS-Comapass dual-mode weak signal acquisition algorithm, whichincludes the improvements of alternate half-hits method, circular shift doppler search,strong-weak signal discrimination, accurate frequency acquisition and differential combining, isproposed. High sensitivity, fast acquisition and low computation are the advantages of theproposed algorithm. Finally, an improved GPS-Compass dual-mode weak signal acquisitionsystem is realized on FPGA with Verilog HDL.It is faster than software satellite receiver.The proposed algorithm is simulated and analysed by GPS-Compass dual-mode digitalintermediate frequency signal source and actual acquired signal. Experiment result shows that-40dB GPS and Compass signal can be acquired by the proposed algorithm. Acquisition ofstrong signal is10times faster than before. GPS and Compass signal can be acquired by theproposed FPGA acquisition module as well. This module is practical and can be easily realizedon ASIC.