Design and Implementation of an RTK-based Vector Phase Locked loop in a GNSS Software Receiver

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GNSS carrier phase tracking is very demanding and challenging. The focus of this thesis is to develop and test an innovative tracking loop with potentially better performance than existing loops in harsh environments. The proposed Double-Difference VPLL (Vector-based Phase Locked Loop) is assisted with base station observations to estimate carrier phase and carrier Doppler measurements at the rover station using information from a stationary base station. The double differencing operation eliminates or substantially reduces spatially and temporally correlated errors between base and rover receivers, leading to increased robustness. A backup layer operating in parallel that provides reference satellite measurements and enhances receiver sensitivity in also introduced. It is shown that the two tracking loop parts have complementary performance in the sense that the backup layer has a lower tracking jitter at high C/N0 values whereas the VPLL has superior functionality at low C/N0 values. Comprehensive mathematical derivations and analyses are described to quantify operations and advantages. The theoretical models are supported by a number of simulation scenarios. The proposed method is also assessed with GPS L1C/A IF samples obtained through hardware-in-the-loop simulations. The proposed method is compared with two other tracking methods, namely the scalar-based and VFLL assisted PLL loops in terms of tracking sensitivity and the probability of an integer ambiguity fixed solution for carrier phase positioning. It is shown through extensive simulations and real data that this algorithm results in better carrier phase availability in degraded environments.
Engineering--Electronics and Electrical, Geotechnology
Shafaati, A. (2017). Design and Implementation of an RTK-based Vector Phase Locked loop in a GNSS Software Receiver (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from doi:10.11575/PRISM/25569