GPS SIGNAL TRACKING USING MAXIMUM-LIKELIHOOD PARAMETER ESTIMATION

Donald E. Gustafson

Peer Reviewed

Abstract:	This paper considers the problem of GPS carrier tracking in the presence of spurious modulation components in amplitude and phase caused by rotating antenna elements in a reentry body. The commonly used phaselock loop approach is not adequate since the disturbances are not specifically modeled. This is a nonlinear estimation problem that is attacked here as a linear estimation problem with an unknown modulation parameter. The modulation parameter is estimated using a maximum-likelihood method in an architecture that uses two Kalman filters of similar structure, one for parameter estimation and one for state estimation. This architecture uncouples the state and parameter estimation processes and reduces the tendency to build up incorrect correlations in the estimator. The performance of the estimator is studied using a Monte Carlo simulation. Maximum-likelihood results are found to be superior to those obtained using a second-order phaselock loop and a nonadaptive fourth-order Kalman filter.
Published in:	NAVIGATION: Journal of the Institute of Navigation, Volume 45, Number 4
Pages:	287 - 296
Cite this article:	Gustafson, Donald E., "GPS SIGNAL TRACKING USING MAXIMUM-LIKELIHOOD PARAMETER ESTIMATION", NAVIGATION: Journal of The Institute of Navigation, Vol. 45, No. 4, Winter 1998-1999, pp. 287-296.
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