Pseudo-noise correlator for GPS spread-spectrum receiver
First Claim
1. A system for operating a GPS C/A code receiver comprising:
- a plurality of channel means, each comprising, means for forming x multibit digital segment values per C/A code period, each multibit digital segment value representing a sequential code segment of a received composite of satellite signals; and
a plurality of correlating means for correlating each digital segment value with n satellite specific sets of in differently time delayed segments of C/A code modulation to form at least n times in time delay specific correction values, wherein x, m, and n are each prime factors of a number of code chips per C/A code period.
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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
19 Claims
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1. A system for operating a GPS C/A code receiver comprising:
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a plurality of channel means, each comprising, means for forming x multibit digital segment values per C/A code period, each multibit digital segment value representing a sequential code segment of a received composite of satellite signals; and
a plurality of correlating means for correlating each digital segment value with n satellite specific sets of in differently time delayed segments of C/A code modulation to form at least n times in time delay specific correction values, wherein x, m, and n are each prime factors of a number of code chips per C/A code period. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
acquire a satellite by selecting the satellite specific sets to represent the same satellite; and
repeat the correlation for the same satellite with a different set of time delayed segments.
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12. The system of claim 1 further comprising means for forming series of m/2 differently time delayed segments by sequentially changing one bit of a previous segment to faint the next segment.
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13. The system of claim 1 wherein the forming means comprises:
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means for sampling the received composite at a first bit rate; and
means for digitally filtering the first composite to form the digital segment values at a bit rate substantially lower than the first bit rate.
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14. The system of claim 1 further comprising means for interrupting the correlating means for a series of code periods to reduce receiver energy consumption.
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15. A system for tracking the movement of an object, said system comprising:
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a multi-channel GPS C/A code receiver associated with the object, wherein each of a plurality of channels is adapted to, form x multibit digital segment values per C/A code period, each multibit digital segment value representing a sequential code segment of a received composite of satellite signals; and
correlate each digital segment value with a satellite specific sets of in differently time delayed segments of C/A code modulation to form at least n times m time delay specific correlation values, wherein x, m, and n are each prime factors of a number of code chips per C/A code period; and
means for determining navigation information from the correlation values. - View Dependent Claims (16, 17, 18)
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19. A method of operating a GPS C/A code receiver comprising, in each of a plurality of receiver channels:
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forming x multibit digital segment values per C/A code period, each multibit digital segment value representing a sequential code segment of a received composite of satellite signals;
correlating each digital segment value with n satellite specific sets of m differently time delayed segments of C/A code modulation to form at least n times m time delay specific correlation values, wherein x, m, and n are each prime factors of a number of code chips per C/A code period; and
accumulating the correlation values in a n times m matrix.
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Specification