Doppler corrected spread spectrum matched filter
First Claim
1. A system for processing communication data from a code signal input, the system comprising:
- a signal sampler operable to receive signal data;
a Doppler shift system operable to provide a Doppler shift correction value;
a storage circuit configured to receive and store the signal data;
a time domain signal processor comprising a complex mixer, coupled to the storage circuit and Doppler shift system, for mixing at least a portion of the signal data with the Doppler shift correction value, where the complex mixer is corrected for pure frequency shift independently from the signal sampler being corrected for both carrier and code Doppler shift;
a complex product generation circuit, coupled to the complex mixer and the code signal input, for computing a complex product of the mixed portion of the signal data with a current code phase of a code signal received a the code signal input;
a summing circuit coupled to the complex product generation circuit for summing the computed complex products as a current complex integration value;
a square root circuit, coupled to the summing circuit, for computing a square root value of the sum of the squares of the current complex integration values, each square root value having a magnitude and an associated code phase; and
an output processing circuit coupled to the square root circuit for processing a plurality of computed square root values, where the time domain signal processor is in signal communication with the signal sampler, the Doppler shift system and code signal input, the time domain signal processor operable to shift the signal data by the Doppler shift correction value and to determine a correlation between the shifted signal data and the code signal input where the code phase and the magnitude of the computed square root value having the largest magnitude indicates that correlation between the shifted signal data and the code signal and wherein the time domain processor is a matched filter processor.
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Accused Products
Abstract
A method and apparatus for a spread spectrum matched filter with Doppler correction suitable for using in a radio frequency receiver. The system includes a signal sampler operable to receive signal data and a Doppler shift system operable to provide a Doppler shift correction value. The system also includes a time domain signal processor in signal communication with the signal sampler, the Doppler shift system and the code signal input, the time domain signal processor operable to shift the signal data by the Doppler shift correction value and to determine a correlation between the shifted signal data and the code signal input. The system reduces a waveform representing Doppler correction values into a Boolean combination that may selectively represent the waveform and be implemented by the processing of a matched filter.
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Citations
26 Claims
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1. A system for processing communication data from a code signal input, the system comprising:
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a signal sampler operable to receive signal data; a Doppler shift system operable to provide a Doppler shift correction value; a storage circuit configured to receive and store the signal data; a time domain signal processor comprising a complex mixer, coupled to the storage circuit and Doppler shift system, for mixing at least a portion of the signal data with the Doppler shift correction value, where the complex mixer is corrected for pure frequency shift independently from the signal sampler being corrected for both carrier and code Doppler shift; a complex product generation circuit, coupled to the complex mixer and the code signal input, for computing a complex product of the mixed portion of the signal data with a current code phase of a code signal received a the code signal input; a summing circuit coupled to the complex product generation circuit for summing the computed complex products as a current complex integration value; a square root circuit, coupled to the summing circuit, for computing a square root value of the sum of the squares of the current complex integration values, each square root value having a magnitude and an associated code phase; and an output processing circuit coupled to the square root circuit for processing a plurality of computed square root values, where the time domain signal processor is in signal communication with the signal sampler, the Doppler shift system and code signal input, the time domain signal processor operable to shift the signal data by the Doppler shift correction value and to determine a correlation between the shifted signal data and the code signal input where the code phase and the magnitude of the computed square root value having the largest magnitude indicates that correlation between the shifted signal data and the code signal and wherein the time domain processor is a matched filter processor. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for processing communication data comprising:
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receiving signal data; applying a Doppler shift correction value to the signal data that includes complex mixing at least a portion of the signal data with the Doppler shift correction value and results in Doppler shifted signal data; receiving a code signal; and determining a correlation between the Doppler shifted signal data and the code signal in a time domain with a matched filter processor where the correction for pure frequency shift is independent of Doppler shift to both carrier and code, that further includes, (a) computing complex products for the mixed portion of the signal data with current code phase of the code signal, (b) summing the computed complex products as a current complex integration value, (c) computing a square root value of the sum of the squares of the current complex integration value, each square root value having a magnitude and an associated code phase, (d) shifting the code signal to a next current code phase, (e) repeating (a) through (d) for the current code phase of the code signal, and outputting the code phase and magnitude of the computed square root value having the largest magnitude as an indication of the correlation between the Doppler shifter signal data and the code signal. - View Dependent Claims (8, 9)
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10. A system for processing radio frequency data comprising:
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a signal sample receiver operable to receive signal data; a Doppler shift corrector operable to provide a Doppler shift correction value; a code signal receiver operable to receive a code signal; a processor coupled to the signal sample receiver, the Doppler shift corrector, and the code signal receiver, the processor operable to apply the Doppler shift correction value to the signal data and to determine a correlation between the Doppler shifter signal data and the code signal processor further includes, a complex mixer coupled to the signal sample receiver, the complex mixer operable to mix at least a portion of the signal data with a Doppler shift correction value, where the complex mixer is corrected for pure frequency shift independently from the signal sampler receiver being corrected for both carrier and code Doppler shift, a complex product processor coupled to the complex mixer, the complex product processor operable to compute a complex product of the mixed portion of the signal data and a current code phase of a code signal, a summer coupled to the complex product processor, the summer operable to compute the complex products as a current complex value, a square root processor coupled to the summer, the square root processor operable to compute the value of the sum of the squares of the current complex integration value, each square root value having a magnitude and an associate code phase, and a controller operable to determine the code phase and magnitude of the computed square root value having the largest magnitude as an indication of correlation between the Doppler shifted input signal and the code signal; and a signal processor coupled to the signal sample receiver, the signal processor operable to process the signal data to extract encoded data. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A system for processing communication data from a code signal input, the system comprising:
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means for receiving signal data; means for providing a Doppler shift correction value; and a time domain signal processor coupled to the receiving means, providing means and the code signal input, the time domain signal processor operable to shift the signal data by the Doppler shift correction value to correct Doppler shift and to determine a correlation between the shifter signal data and the code signal input wherein the time domain signal processor is a matched filter processor where the correction for pure frequency shift is independent from the correction of both carrier and code Doppler shift, and includes, means for storing configured to receive and store the signal data, means for complex mixing coupled to the storing means and providing means for mixing at least a portion of the signal data with the Doppler shift correction value, means for complex product generation, coupled to the complex mixing means and the code signal input, for computing a complex product of the mixed portion of the signal data with a current code phase of the code signal, means for summing, coupled to the complex product generation means, for summing the computed complex products as a current complex integration value, means for generating an envelope, coupled to the summing means, for computing a square root value of the sum of the squares of the current complex integration values, each square root value having a magnitude and an associated code phase, and an output processing circuit, coupled to the generating an envelope means, for processing a plurality of computed square root values, wherein the code phase and magnitude of the computed square root value having the largest magnitude indicates the correlation between the shifted signal data and the code signal. - View Dependent Claims (17, 18, 19, 20, 21)
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22. A computer readable medium having software for processing communication data, the computer readable medium comprising:
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means for receiving signal data; means for applying a Doppler shift correction value to correct Doppler shift to the signal data that results in a Doppler shifter signal data; means for determining a correlation between the Doppler shifter signal data and the code signal in time domain where the correction for pure frequency shift is independent from the correction for both carrier and code Doppler shift that includes, means for computing complex products for the mixed portion of the signal data with a current code signal, means for summing the computed complex products as a current complex integration value, means for computing the square root value of the sum of the squares of the current complex integration value, each square root value having a magnitude and an associated code phase, means for shifting the code signal to a next current code phase, and means for outputting the code phase and magnitude of the computed square root value having the largest magnitude as an indication of the correlation between the Doppler shifter signal data and the code signal. - View Dependent Claims (23, 24, 25, 26)
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Specification