A Non-Traditional Approach to Analysis of Signal Structure Anomalies Observed in PRN 21

J. Little, J. York, A. Farris, D. Munton

Abstract:	The FAA's WAAS ground stations, distributed across the United States, continually monitor the GPS signals from all SVs for carrier phase anomalies. During 2008, WAAS detected a signi_cantly higher incidence of car- rier phase tracking anomalies from SVN45 (PRN21), and to a lesser extent from SVN34 (PRN04), than from the remainder of the constellation. Because theWAAS detected these anomalies simultaneously at multiple geographically diverse ground stations, the anomalies are believed to originate in the satellite. These carrier phase anomalies are a concern because WAAS ags the SV on which they are detected as unusable for several minutes after after the event. Understanding these anomalies should provide insight into issues with the GPS satellite signal path, as well as tracking loop behavior in GPS receivers. ARL:UT has employed an internally developed GPS correlation engine (the GNSS Complex Ambiguity Function - GCAF) to study the signals of PRN 21. The GCAF produces correlation sums at 512 correla- tion delays every 1.2 ms which allows the direct obser- vation of the these transient events. Several of these events were captured using both the GCAF and tradi- tional GPS receivers. The paper provides an overview of the GCAF and how it allows uniquely detailed ex- amination of the GPS signal. The events from PRN 21 and other SVs as observed with the GCAF are pre- sented and characterized. The impact of the observed events on the other GPS receivers is described.
Published in:	Proceedings of the 23rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2010) September 21 - 24, 2010 Oregon Convention Center, Portland, Oregon Portland, OR
Pages:	2190 - 2198
Cite this article:	Little, J., York, J., Farris, A., Munton, D., "A Non-Traditional Approach to Analysis of Signal Structure Anomalies Observed in PRN 21," Proceedings of the 23rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2010), Portland, OR, September 2010, pp. 2190-2198.
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