Importance

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Abstract

Method and apparatus providing enhanced sensitivity for GPS receivers by allowing coherent integration of a correlation over several code periods of a GPS signal in one embodiment, and by performing a time to frequency domain conversion to the output from a correlation processor in a second embodiment. In the case in which coherent integration is performed over several code periods, advantage is taken of the fact that CDMA cellular telephone base stations transmit information that allows the receiver to determine GPS time before beginning a GPS signal acquisition process. The integration can be expanded to include code periods from more than one bit period, if the GPS receiver takes advantage of the fact that known bit patterns are transmitted at particular times within the transmission from a GPS satellite. If no base station is within range, then the output from a correlator that integrates a correlation over one code period is used to generate values that are input to in a discrete time domain to frequency domain transform. The output from the transform will indicate the presence of a signal from a particular satellite and the offset between locally generated signal and the received GPS signal.

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First Claim