An Improved GPS Sensor Technology - Fast Acquisition and Sub-meter Precision at High Dynamics

D.G. Powell, A.R. Pratt, and J.H. Merts

Abstract:	In 1999 a new type of GPS receiver was proposed for the Department of Defense funded Programme to meet the emerging needs of missile test and evaluation. This new hybrid receiver was required to have a cold start acquisition time of less than 3 seconds with no prior information (time, location, ephemeris) in the missile, and track in dynamics of at least 50 G. This paper will provide information on the architecture of the hybrid approach and discuss improvements made to the design over the life of the project. The final configuration reduced the downlink bandwidth from 114 kb/s to under 35 kb/s and added carrier phase measurements with accuracies of a few centimeters at velocities of over 2000 m/s while maneuvering at over 50 G. The GPS Sensor Unit (GSU) that resulted from this effort was realized through some novel processing approaches that included a hardware 64 point FFT and a custom ASIC controller that was able to test over 3,000,000 GPS potential solutions per second. A novel approach for solving for the millisecond ambiguity of rover local time on the ground was also developed. This tracking code has now been applied to the same GPS chip-set in a postage stamp sized format that is being integrated into miniature telemetry packages used in mortar fuze wells and miniature missiles. The GSU also operates in a full receiver mode and is capable of tracking through typical 50 G maneuvers. Results of GPS simulation testing as well as actual flight test data will be presented for both the sensor mode and the navigation mode of this new device.
Published in:	Proceedings of the 2006 National Technical Meeting of The Institute of Navigation January 18 - 20, 2006 Hyatt Regency Hotel Monterey, CA
Pages:	1048 - 1056
Cite this article:	Powell, D.G., Pratt, A.R., Merts, J.H., "An Improved GPS Sensor Technology - Fast Acquisition and Sub-meter Precision at High Dynamics," Proceedings of the 2006 National Technical Meeting of The Institute of Navigation, Monterey, CA, January 2006, pp. 1048-1056.
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