Tracking Loop Dynamics and Synchronous AGC for GPS

Jonathan Hill

Abstract:	This paper considers the dynamics of the carrier phase and code phase tracking loops in a GPS receiver for various received signal energy levels. In a GPS receiver it is the processor gain afforded by the action of despreading that reveals the navigation message and replica code phase for a satellite. Starting at the antenna and continuing up to despreading, a desired GPS signal is buried completely in noise. A conventional narrow band receiver relies on automatic gain control (AGC) to moderate the received signal envelope and hence regulate the loop gain in synchronous detection. However in being dominated by noise, that approach is not possible in GPS. As an example, the correlator output of a GPS receiver based on the Plessy GP1020 chip may have its despread signal vary by nearly 20dB. This paper incorporates a synchronous AGC mechanism to control the dynamics of the tracking loops in a GPS receiver.
Published in:	Proceedings of the 2004 National Technical Meeting of The Institute of Navigation January 26 - 28, 2004 The Catamaran Resort Hotel San Diego, CA
Pages:	352 - 361
Cite this article:	Hill, Jonathan, "Tracking Loop Dynamics and Synchronous AGC for GPS," Proceedings of the 2004 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2004, pp. 352-361.
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