METHOD AND DEVICE FOR FAST CORRELATION CALCULATION
First Claim
1. A method for calculating correlations between a first sequence and a second sequence, said first sequence and said second sequence each having a duration DCode, the first sequence being extracted from a digital signal comprising a code, said code comprising elementary time divisions, called chips, of a duration Dchip, said chips being sampled on pulses delivered by an NCO oscillator at the mean frequency 2/Dchip, the second sequence resulting from a sampling at a frequency Fe of an analog signal, the frequency Fe being greater than 2/Dchip, said method comprising a step of aggregating the samples of the second sequence, over consecutive integration intervals of duration equal on average to Dchip/2, starting at each pulse of the NCO oscillator, so as to determine results of elementary aggregates, the results of elementary aggregates being employed to determine results of calculations of correlations between a first sequence and second sequences, the second sequences being deduced from one another by a time shift of duration Dchip/2, comprising the following steps:
- of summing two results of consecutive elementary aggregates to obtain double elementary aggregate results;
of weighting each result of double elementary aggregate of the second sequence by the value of the code of the first sequence to obtain results of weighted double aggregates; and
of accumulating the results of weighted double aggregates.
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Abstract
The field of the invention is that of the reception of a radionavigation signal originating from a satellite positioning system such as the GPS system. The present invention concerns a method for calculating correlations between a first sequence and a second sequence, said first sequence and said second sequence having a duration DCode, the first sequence being extracted from a digital signal comprising a code, said code comprising elementary time divisions, called chips, of mean duration Dchip, said chips being synchronized with pulses delivered by an NCO oscillator at the mean frequency 2/Dchip, the second sequence resulting from a sampling at a frequency Fe of an analog signal, the frequency Fe being greater than 2/Dchip. According to the invention, the method comprises a step of aggregating samples of the second sequence, over consecutive integration intervals of duration equal on average to Dchip/2, starting at each pulse of the NCO oscillator, so as to determine results of elementary aggregates.
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Citations
6 Claims
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1. A method for calculating correlations between a first sequence and a second sequence, said first sequence and said second sequence each having a duration DCode, the first sequence being extracted from a digital signal comprising a code, said code comprising elementary time divisions, called chips, of a duration Dchip, said chips being sampled on pulses delivered by an NCO oscillator at the mean frequency 2/Dchip, the second sequence resulting from a sampling at a frequency Fe of an analog signal, the frequency Fe being greater than 2/Dchip, said method comprising a step of aggregating the samples of the second sequence, over consecutive integration intervals of duration equal on average to Dchip/2, starting at each pulse of the NCO oscillator, so as to determine results of elementary aggregates, the results of elementary aggregates being employed to determine results of calculations of correlations between a first sequence and second sequences, the second sequences being deduced from one another by a time shift of duration Dchip/2, comprising the following steps:
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of summing two results of consecutive elementary aggregates to obtain double elementary aggregate results; of weighting each result of double elementary aggregate of the second sequence by the value of the code of the first sequence to obtain results of weighted double aggregates; and of accumulating the results of weighted double aggregates. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification