Spread spectrum receiver with multi-bit correlator
First Claim
1. A method of processing signals received by a spread spectrum receiver from at least one of a plurality of transmitting sources each having an associated code, said method comprising:
- correlating each sequential segment of a spread spectrum signal with at least one series of differentially time delayed code replicas to generate a plurality of correlation results using a single multi-bit digital correlator; and
accumulating the plurality of correlation results in a matrix of correlation magnitudes as a function of time delay.
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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
20 Claims
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1. A method of processing signals received by a spread spectrum receiver from at least one of a plurality of transmitting sources each having an associated code, said method comprising:
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correlating each sequential segment of a spread spectrum signal with at least one series of differentially time delayed code replicas to generate a plurality of correlation results using a single multi-bit digital correlator; and
accumulating the plurality of correlation results in a matrix of correlation magnitudes as a function of time delay. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
forming a plurality of sets of differently time delayed correlation products for each segment for the same code; and
selecting a code specific delay for the associated code when at least one of the correlation products for that code achieves a predetermined threshold.
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8. The method of claim 1 further comprising:
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forming sets of differently time delayed correlation products for each sequential segment for each of a plurality of different codes; and
selecting a code specific delay for each code when at least one of the correlation products for that code achieves a predetermined threshold.
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9. The method of claim 1 wherein accumulating the plurality of correlation results comprises accumulating the power or amplitude of each correlation.
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10. The method of claim 1 further comprising:
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sampling the spread spectrum signal to form partial chip width samples; and
collecting a sequential series of the partial chip samples to form each sequential segment.
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11. The method of claim 1 further comprising providing a series of satellite specific, time delayed multi-chip segments of a replica of each code for correlation with each of the sequential segments.
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12. The method of claim 1 wherein correlating each sequential segment comprises:
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synchronizing a series of satellite specific, time delayed multi-chip replicas for correlation with each of the sequential segments;
synchronizing the local clock with a clock associated with a source of the code being received; and
synchronizing the local clock with a clock associated with a source of the code being received after being temporarily obscured.
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13. The method of claim 1 further comprising:
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tracking a prompt delay from a source of the code; and
monitoring correlation products representing lesser time delays than the prompt delay to detect the inaccurate tracking of a multipath signal from the course of the code.
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14. The method of claim 1 further comprising selecting a time delay not equal to one of the time delays of the replicas as a prompt delay.
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15. The method of claim 1 further comprising:
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forming digitized samples of signals received from code sources at a first rate;
forming the sequential segments from the digitized samples at a second rate substantially slower than the first rate.
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16. The method of claim 1 further comprising:
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selectively configuring the matrix to form either a) n different code specific sets of m different time delayed correlation products, or b) n times m different time delayed correlation products for one code.
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17. A spread spectrum receiver for processing signals from at least one of a plurality of transmitting sources each having an associated code, said receiver comprising:
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a single multi-bit digital correlator for correlating each sequential segment of a spread spectrum signal with at least one series of differentially time delayed code replicas to generate a plurality of correlation results; and
matrix means responsive to the correlator for accumulating the plurality of correlation results in a matrix of correlation magnitudes as a function of time delay. - View Dependent Claims (18, 19)
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20. A system for tracking the movement of an object, said system comprising:
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a spread spectrum receiver associated with the object and adapted to correlate each sequential segment of a spread spectrum signal with at least one series of differentially time delayed code replicas to generate a plurality of correlation results using a single multi-bit digital correlator; and
accumulate the plurality of correlation results in a matrix of correlation magnitudes as a function of time delay; and
means for determining navigation information for the object from the correlation results.
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Specification