Time-Domain Spectrum of GPS SA

David W. Allan, Wayne P. Dewey

Abstract:	A new time-domain variance, TVAR, is used to characterize the spectrum of GPS SA signals from different Block H satellites. This variance is used as a vehicle to study the similiarities in spectrum of the different satellites. Once the spectrum is understood, optimum filters can be desgined which can improve GPS as a source for accurate time and frequency as well as for time transfer. Preliminary investigations show that the spectrum satisfies the SPS navigation and position determination statements. Timing degradation duo to SA is also consistent with official statements. The intent of this paper is to demonstrate the possibility of filtering a large amount of the SA from GPS signals as available using an optimized digital filter based on the spectrum, coupled to a very good clock (Ovenized Quatrz, Rubidium, Cesium) in an ideal receiver. The time-domain information presented is taken from actual SA data. The filter designs and predicted results are based on simulations. The experimental design is well in place. The actual experiments and implementation of the ideas demonstrated in the paper are yet to be done. The preliminary studies indicate that better than 10 ns timing and time transfer may be achieved. If the experiments validate the simulations, the approach demonstrated in the paper will have very important applications in telecommunications, power systems (control, fault detection and management), as well as within the time and frequency and the navigation communities.
Published in:	Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993) September 22 - 24, 1993 Salt Palace Convention Center Salt Lake City, UT
Pages:	129 - 136
Cite this article:	Allan, David W., Dewey, Wayne P., "Time-Domain Spectrum of GPS SA," Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993), Salt Lake City, UT, September 1993, pp. 129-136.
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