Fast acquisition of spread-spectrum signals by dynamically varying spacing of search bins
First Claim
1. A method of locating a received signal, the method comprising:
- using a search region of signal characteristics, the search region defined in terms of a plurality of bins;
varying a spacing of the bins; and
determining a signal characteristic associated with the received signal by locating the signal in one of the bins.
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Accused Products
Abstract
A Global Positioning System (GPS) receiver employs variable spacing of Doppler offset bins and code offset bins when acquiring a P(Y) code, to improve signal acquisition characteristics with respect to a search region having a plurality of Doppler offset bins and code offset bins. The receiver includes an acquisition module in which an input signal representative of a received P(Y) code is received and applied to a first programmable rate mixer. An output of the first programmable rate mixer is applied to a combiner, which selectively combines samples of the input signal based on a control input to dynamically determine the spacing of the code offset bins. An output of the combiner is normalized and applied to a correlation unit, which generates correlation measures of the received P(Y) code and a locally generated P(Y) code. A signal representative of the correlation measures is applied separately to each of a set of programmable rate mixers and mixed with separate mixing signals. The spacing of the Doppler offset bins is dynamically determined by controlling the rates of the mixing signals.
87 Citations
40 Claims
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1. A method of locating a received signal, the method comprising:
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using a search region of signal characteristics, the search region defined in terms of a plurality of bins;
varying a spacing of the bins; and
determining a signal characteristic associated with the received signal by locating the signal in one of the bins. - View Dependent Claims (2, 3, 4)
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5. A method of locating a signal in a search region defined in terms of a plurality of frequency offset bins, the method comprising:
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varying a spacing of the frequency offset bins; and
attempting to locate the signal in one of the frequency offset bins. - View Dependent Claims (6, 7, 8, 9)
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10. A method of locating a received signal in a search region defined in terms of a plurality of code offset bins, the method comprising:
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varying a spacing of the code offset bins; and
attempting to locate the signal in one of the code offset bins. - View Dependent Claims (11, 12, 13, 14)
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15. In a signal receiver, a method of locating a modulation code of a received signal, the method comprising the steps of:
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searching for a frequency of the modulation code based on a plurality of frequency offsets, the frequency offsets corresponding to offsets between a frequency of the modulation code and a frequency of a reference code;
searching for a code offset of the modulation code based on a plurality of code offsets, the code offsets corresponding to temporal offsets between the modulation code and the reference code, wherein the frequency offsets and the code offsets form a plurality of bins of a search region; and
automatically varying a spacing of the bins. - View Dependent Claims (16, 17, 18)
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19. A method of searching for a received signal within a search region, the search region characterized by a plurality of frequency offset bins and a plurality of code offset bins, the method comprising the steps of:
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sampling the received signal to generate a first plurality of samples;
determining a combining scheme based on a current signal environment, the combining scheme for determining a spacing of the code offset bins within the search region;
combining at least some of the first plurality of samples based on the combining scheme to generate a second plurality of samples;
correlating the second plurality of samples with a reference code to generate correlation measures;
determining a first frequency based on the current signal environment, the first frequency for determining a spacing of the frequency offset bins within the search region;
generating a first plurality of signals, each of the first plurality of signals having a frequency based on the first frequency;
mixing each of the first plurality of signals with a signal representing the correlation measures to generate a second plurality of signals; and
using the second plurality of signals to locate the received signal within the search region. - View Dependent Claims (20, 21, 22, 23, 24)
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25. A receiver for searching for a signal within a search region, the search region defined in terms of a plurality of bins, the receiver comprising:
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a sampler for sampling an input signal; and
a combiner coupled to the sampler stage, the combiner for combining at least some of the samples based on a first control input, such that a spacing of the bins is variable based on the first control input. - View Dependent Claims (26, 27, 28, 29)
a correlator coupled to the combiner, the correlator generating correlation measures associated with the samples and a second signal; and
a mixer coupled to receive a third signal representative of the correlation measures, the mixer mixing the third signal with a fourth signal, the fourth signal having a frequency based on a second control input, such that the spacing of the bins is further variable based on the second control input.
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28. A receiver according to claim 25, wherein the second signal represents a locally generated reference code, and wherein the correlation measures correspond to a correlation between the reference code and a code modulating the input signal.
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29. A receiver according to claim 25, further comprising a normalizer, the normalizer coupled to receive an output of the combiner including combined samples of the input signal, the normalizer normalizing the combined samples as a function of said combining.
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30. A signal receiver comprising:
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input means for receiving a signal from a remote transmission source, the signal being modulated by a modulation code; and
search means for locating the modulation code, the search means including;
means for searching for the signal within a search region, the search region defined in terms of a plurality of frequency offset bins; and
means for varying a spacing of the frequency offset bins. - View Dependent Claims (31, 32, 33, 34, 35, 39, 40)
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36. A positioning system receiver comprising:
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a sampling stage for inputting and sampling a received signal and for outputting samples of the received signal; and
a search stage coupled to the sampling stage for locating the received signal within a search region, the search stage including;
a combiner coupled to receive the samples, the combiner combining at least some of the samples based on a first control input;
a correlation stage coupled to receive a first signal representative of combined samples output by the combiner and coupled to receive a reference signal, the correlation stage generating a correlation signal representing correlation measures associated with the first signal and the reference signal; and
an accumulation stage including;
an oscillator coupled to receive a second control input, the oscillator outputting a second signal having an offset frequency based on the second control input; and
a plurality of mixers, each coupled to receive the correlation signal and a different one of a plurality of mixing signals, each of the plurality of mixing signals having a different frequency derived from the offset frequency, each of the mixers outputting a different mixed signal; and
a plurality of accumulators, each coupled to receive one of the mixed signals and to output accumulation measures thereof. - View Dependent Claims (37, 38)
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Specification