Analysis of GPS-SPS Inter-PRN Pseudorange Biases due to Receiver Front-End Components

Sanjeev Gunawardena, Frank van Graas

Abstract:	Users of high-precision, single-frequency local area differential GNSS systems mitigate common-mode error sources by applying pseudorange corrections that are received from a nearby ground reference station. The remaining significant error sources for such systems include ionosphere gradients, multipath, and errors caused by natural GNSS signal deformations. Signal deformation errors occur when slight variations in a GNSS signal’s nominal chip shape produce corresponding variations in the receiver’s computed correlation function. The receiver’s timing estimate of chip transition zero crossings, which is a component of the pseudorange measurement, is performed using its code discriminator function that is based on the correlation function. This interaction of how natural signal deformations ultimately affect the pseudorange measurement is also dependent on the receiver’s pre-correlation bandwidth, code discriminator type and early-late correlator spacing. Ground and airborne receivers may have different receiver designs that give rise to errors that are not mitigated using differential corrections. Furthermore, receiver front-end passband group delay variations causes the line spectra of GNSS signals to be delayed by different amounts leading to inter-PRN biases. These are in addition to the biases caused by natural satellite signal deformations. The error budget allocated to signal deformation in safety-critical local area differential GPS-SPS systems is on the order of 10 cm. Hence, it is important to understand the impact of inter-PRN biases due to the receiver front-end so that this component of the error can be appropriately bounded. This paper presents the results of GPS-SPS inter PRN biases measured for typical filter components used in GNSS receivers. These include RF cavity resonator, ceramic resonator, block acoustic wave filters, and IF surface acoustic wave and discrete LC filters. Inter-PRN biases were measured by passing simulated GPS-SPS signals though a finite impulse response model representing the device under test. The filter model was derived from the component’s scattering parameters that were measured using a vector network analyzer. The results reported in this paper can be used to validate receiver requirements for ground-based and satellite-based GPS-SPS augmentation systems. The results are also significant for precise ionosphere measurements and time transfer applications.
Published in:	Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014) September 8 - 12, 2014 Tampa Convention Center Tampa, Florida
Pages:	2611 - 2624
Cite this article:	Gunawardena, Sanjeev, van Graas, Frank, "Analysis of GPS-SPS Inter-PRN Pseudorange Biases due to Receiver Front-End Components," Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014), Tampa, Florida, September 2014, pp. 2611-2624.
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