Spread spectrum receiver with multi-bit correlator
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Accused Products
Abstract
A terrestrial C/A code GPS receiver system digitally samples, filters and stores a segment of 11 half chips of the received composite as a binary number and multiplexes this number for parallel correlation with each of a series of multibit code replicas for the satellites to be tracked. Each of the time delay specific correlation products are accumulated in a cell of a memory matrix so that at least twenty two delays for each satellite may be evaluated each code period providing fast reacquisition, even within a city intersection, as well as correction of multipath tracking and multipath interference. All cells of the memory matrix may be used for an acquisition of a single satellite in about 4 ms. Two satellite tracking, in addition to altitude hold, uses cross track hold alternating with clock hold to update the cross track estimate. Single satellite tracking uses cross track and clock hold together. Navigation data is updated with detected changes in motion including turns.
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Citations
43 Claims
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1-20. -20 (canceled)
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21. A method for global positioning system (GPS) navigation, the method comprising:
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tracking at least one GPS signal from a GPS satellite, including performing a series of early correlation, a series of prompt correlations, and a series of late correlations to define a capture window for maintaining synchronization of the at least one GPS signal with a generated replica signal; and
reacquiring the at least one GPS signal, including performing a plurality of additional early correlations and a plurality of additional late correlations so as to create an expanded capture window for maintaining the synchronization. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28)
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29. An apparatus for global positioning system (GPS) navigation, the apparatus comprising:
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a satellite receiver configured to receive GPS satellite signals;
a plurality of satellite tracking channels coupled to the satellite receiver, wherein each of the plurality of satellite tracking channels is configured to, track at least one GPS signal from a GPS satellite, including performing a series of early correlation, a series of prompt correlations, and a series of late correlations to define a capture window for maintaining synchronization of the at least one GPS signal with a generated replica signal; and
reacquire the at least one GPS signal, including performing a plurality of additional early correlations and a plurality of additional late correlations so as to create an expanded capture window for maintaining the synchronization; and
a satellite processor coupled to receive outputs from the plurality of satellite tracking channels. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36)
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37. A computer readable medium having instructions stored thereon, which when executed control a global positioning system (GPS) navigation system, wherein controlling includes:
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tracking at least one GPS signal from a GPS satellite, including performing a series of early correlation, a series of prompt correlations, and a series of late correlations to define a capture window for maintaining synchronization of the at least one GPS signal with a generated replica signal; and
reacquiring the at least one GPS signal, including performing a plurality of additional early correlations and a plurality of additional late correlations so as to create an expanded capture window for maintaining the synchronization. - View Dependent Claims (38, 39, 40, 41, 42, 43)
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38-1. The method of claim 37 wherein performing the plurality of additional early correlations and the plurality of additional late correlations comprises:
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generating a plurality of code samples that are correlated with the at least one GPS signal; and
delaying each of the plurality of code samples by a multiple of a fraction of a chip to generate a plurality of early code samples, and a plurality of late code samples, wherein adjoining code samples are offset by a multiple of the fraction of a chip.
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Specification