Field Test Results of Clock Stability and Code Carrier Coherency of Dual Frequency Navigation Transponders

M.S. Grewal, L. Cheung, R. Lucy and W. Brown

Abstract:	The various Satellite-Based Augmentation Systems (SBASs) currently under development utilize Geostationary Earth Orbit (GEO) satellites to provide ranging signals to the end user that also contain integrity data on GPS, GLONASS, and Galileo satellites. This signal is generated on the ground and provided via C-band (or K-band) uplink to the GEO, whose navigation transponder frequency translates it to L1 and C-band (or K-band) downlink frequencies, then broadcasts the signals throughout the GEO’s coverage footprint. An important aspect of the navigation transponder is its frequency stability. To maintain code carrier coherency, the frequency of the propagated is controlled via the uplink signal. This is accomplished using closed loop algorithms which are capable of maintaining the code chipping rate and carrier frequency of the received signal in a constant ratio of 1:1540, as well as maintaining the correct doppler and ionospheric divergence as observed by the user. This paper describes and shows the field results for code carrier coherency and clock stability obtained at GEO Uplink Subsystems (GUSs), Clarksburg, MD; Santa Paula, CA; and Brewster, WA for the AOR-W and POR satellites. In these tests, the GUS is integrated with the remainder of WAAS in a closed system via the Type 9 navigation message from the Corrections and Verification (C&V) function of the Wide-Area Master Station (WMS) as compared to earlier prototype stand-alone tests. These results meet the specifications for short term and long term code carrier coherency and for clock stability over 1- 10 sec, just like GPS signals [1,2].
Published in:	Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT
Pages:	277 - 283
Cite this article:	Grewal, M.S., Cheung, L., Lucy, R., Brown, W., "Field Test Results of Clock Stability and Code Carrier Coherency of Dual Frequency Navigation Transponders," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 277-283.
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