Design Technique for Precise GNSS Receiver Post-Correlation Noise Floor Measurements with Usage Design Examples by the Search and Tracking Processes

Phillip W. Ward

Abstract:	GNSS receiver baseband search and tracking processes require precise measurements of the baseband noise floor. The presence of in-band radio frequency interference (RFI) or jamming can cause radical changes of the baseband noise floor. This paper addresses a postcorrelation noise measurement design technique that provides accurate baseband noise measurements even when the noise floor changes radically under in-band RFI or jamming conditions. Previous papers [1] and [2] by this author on the jammer-to-noise power ratio (J/N) meter addressed pre-correlation noise measurement design techniques that precisely measure the change in the GNSS receiver front-end noise floor in the presence of in-band RFI or jamming. As is the case with the J/N meter design, the most cost-effective design of precise post-correlation noise measurements must be implemented as part of the original receiver architecture and not as an afterthought. A design example is presented to help prevent this oversight in future GNSS receiver architectures. The design example illustrates that the ideal implementation impacts the GNSS receiver’s replica code phase shifter design as well as related downstream correlators and integrators required to complete the noise measurement process. Assuming the availability of precise baseband noise measurements, additional design examples are presented for its use in both the receiver search and tracking processes. In the search process, a search detector design is presented that includes the design of the detection threshold that depends on a precise noise measurement. In the tracking process, a precise baseband carrier-to-noise power ratio (C/N0) meter design is presented that depends on a precise noise measurement.
Published in:	Proceedings of the 2010 International Technical Meeting of The Institute of Navigation January 25 - 27, 2010 Catamaran Resort Hotel San Diego, CA
Pages:	607 - 617
Cite this article:	Ward, Phillip W., "Design Technique for Precise GNSS Receiver Post-Correlation Noise Floor Measurements with Usage Design Examples by the Search and Tracking Processes," Proceedings of the 2010 International Technical Meeting of The Institute of Navigation, San Diego, CA, January 2010, pp. 607-617.
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