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This paper aims to develop a Global Positioning System (GPS) Software-Defined Receiver (SDR) based on Vector Tracking Loop (VTL) for low earth orbit (LEO) satellites. Since GPS receiver onboard the LEO satellites experiences high receiver dynamics and results in large Doppler frequency variation around 40 kHz, conventional scalar tracking loop (STL) receiver suffers from frequent signal tracking interruption and significantly reduces navigation availability. To mitigate the impacts on STL receiver, VTL receivers integrate signal tracking with navigation solutions and enable information exchange between each channel, which brings better immunity of receiver dynamics and providing better signal tracking performance. The proposed VTL GPS receiver is validated through a high-fidelity GPS signal simulator with GPS L1 C/A signal. The results demonstrate that the proposed VTL based GPS receiver has average carrier phase tracking error of all channels less than 9 degrees and the position error lower than 5 meters under high dynamic scenarios.
Liao et al. (Wed,) studied this question.