GPS-SPS Inter-PRN Pseudorange Biases Compared for Transversal SAW and LC Filters Using Live Sky Data and ChipShape Software Receiver Processing

Sanjeev Gunawardena, Frank van Graas

Abstract:	Unique characteristics of navigation signal generation and transmission hardware in GPS satellites are known to cause nominal signal deformations. These natural deformations in turn induce pseudorange errors that are a function of receiver code discriminator correlator spacing and bandwidth. These pseudorange biases are on the order of tens of centimeters for GPS-SPS signals, and hence must be accounted for in high-accuracy, high-integrity differential systems that employ dissimilar receivers. Previous research has shown that components used in the design of receiver front-ends can have a significant impact on measured natural biases. In particular, the use of transversal SAW IF filters can impress additional and somewhat peculiar signal deformations that also vary as a function of PRN code. This paper evaluates the impact of these SAW filter-induced deformations by comparing with an LC filter of similar spectral characteristics. This comparison is performed using live sky data and an experimental setup that keeps everything other than the filters the same. This paper also introduces an improved method to compute pseudorange natural biases that is based on ChipShape processing. The new method is invariant to the number of positive and negative chip transitions present in a PRN code and hence eliminates the need to perform the so called ‘thin, medium, and thick’ correlation function compensation typically implemented in high-accuracy GPS-SPS receivers. The results of this paper are significant for validating receiver requirements for GBAS and SBAS, and are also relevant for precise ionosphere measurements and time transfer applications.
Published in:	Proceedings of the 2015 International Technical Meeting of The Institute of Navigation January 26 - 28, 2015 Laguna Cliffs Marriott Dana Point, California
Pages:	393 - 403
Cite this article:	Gunawardena, Sanjeev, van Graas, Frank, "GPS-SPS Inter-PRN Pseudorange Biases Compared for Transversal SAW and LC Filters Using Live Sky Data and ChipShape Software Receiver Processing," Proceedings of the 2015 International Technical Meeting of The Institute of Navigation, Dana Point, California, January 2015, pp. 393-403.
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