Vector Tracking Based GPS Software-Defined Receiver for LEO Satellites

This study aimed to develop a Global Positioning System (GPS) Software-Defined Receiver (SDR) based on vector tracking loop (VTL) for low-Earth-orbit (LEO) satellites. Because GPS receivers onboard LEO satellites experience high receiver dynamics, which result in large Doppler frequency variations around 40 kHz, conventional scalar tracking loop (STL) receivers exhibit frequent signal tracking interruption, which considerably reduces navigation availability. To mitigate such interruption, VTL receivers integrate signal tracking with navigation solutions and enable information exchange among all channels, resulting in increased resistance to receiver dynamics and thus enhanced signal tracking performance. A VTL-based GPS receiver was developed in this study, and the developed receiver was validated using GPS L1 C/A signals by employing a high-fidelity GPS signal simulator. The results of this study indicated that under high-dynamic scenarios, the developed VTL-based GPS receiver had an average carrier phase tracking error of all channels less than 9°and a position error of less than 5 m.