GNSS Receiver with Vector Based FLL-Assisted PLL Carrier Tracking Loop

Stefan Kiesel, Christian Ascher, Daniel Gramm, Gert F. Trommer

Abstract:	Recent research is conducted in the field of GNSS signal tracking algorithms. Basic tracking techniques like standard phase lock loop (PLL) and frequency lock loop (FLL) are replaced by vector based approaches, where a valid navigation solution (position, velocity, clock error, and clock drift) is used to close the tracking loops. This approach is called vector receiver or deep integration. The obvious advantage is that continuous tracking of all satellites even in weak signal conditions or under RF interference is possible. A receiver in vector mode avoids time consuming and processing power consuming re-acquisition after a signal outage. In this paper a vector receiver is chained with a FLL-assisted PLL for carrier phase tracking. The output of the VFLL receiver is used to replace the traditional FLL discriminator used in a FLL-assisted PLL. This combines the robustness of carrier tracking from a vector receiver with the carrier phase tracking ability of a PLL. Partial GPS satellite signal outages are bridged using the vector tracking capability with position and velocity information from remaining satellites. With instantaneous re-acquisition, carrier phase lock can be achieved. Even in degraded signal environment the vector based FLL-assisted PLL has an increased robustness regarding carrier phase tracking in comparison to traditional FLL- assisted PLL carrier tracking loops.
Published in:	Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008) September 16 - 19, 2008 Savannah International Convention Center Savannah, GA
Pages:	197 - 203
Cite this article:	Kiesel, Stefan, Ascher, Christian, Gramm, Daniel, Trommer, Gert F., "GNSS Receiver with Vector Based FLL-Assisted PLL Carrier Tracking Loop," Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008), Savannah, GA, September 2008, pp. 197-203.
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