Method and apparatus for computing signal correlation
First Claim
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1. A method for computing correlations of a digital signal with a pseudorandom reference code comprising:
- a) dividing a pseudorandom reference code into a plurality of code segments;
b) selecting a code segment;
c) forming an inner product between said selected code segment and a set of digital signal samples to produce a partial correlation;
d) repeating steps b) and c) to produce a plurality of partial correlations;
e) summing the plurality of partial correlations as each partial correlation is produced to form a plurality of correlations.
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Abstract
A method and apparatus for computing a convolution between an input GPS signal and a C/A code reference by generating the convolution result in real time without storing unprocessed signal samples. The apparatus comprises a vector multiplier running at high speed to achieve the same result as a vector multiplier sized to process an entire epoch.
3 Citations
22 Claims
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1. A method for computing correlations of a digital signal with a pseudorandom reference code comprising:
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a) dividing a pseudorandom reference code into a plurality of code segments;
b) selecting a code segment;
c) forming an inner product between said selected code segment and a set of digital signal samples to produce a partial correlation;
d) repeating steps b) and c) to produce a plurality of partial correlations;
e) summing the plurality of partial correlations as each partial correlation is produced to form a plurality of correlations. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A receiver of global positioning system (GPS) signals comprising:
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an RF/IF converter for filtering and frequency translating a received GPS signals to form an IF signal;
an analog to digital converter for digitizing the IF signal;
a tuner for removing Doppler shift from the digitized signal and producing an in-phase (I) signal and a quadrature (Q) signal;
a decimation circuit for subsampling the I and Q signals;
a convolution processor for producing I and Q partial correlations by multiplying selected segments of a C/A reference code with said subsampled I and Q signals;
a first accumulator for accumulating said I partial correlations to form a full correlation; and
a second accumulator for accumulating said Q partial correlations to form a full correlation - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 20, 21, 22)
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19. A receiver of global positioning system (GPS) signals comprising:
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an RF/IF converter for filtering and frequency translating a received GPS signals to form an IF signal;
an analog to digital converter for digitizing the IF signal;
a tuner for removing Doppler shift from the digitized signal and producing an in-phase (I) signal and a quadrature (Q) signal;
a decimation circuit for subsampling the I and Q signals;
a convolution processor for producing I and Q partial correlations by multiplying selected segments of a C/A reference code with said subsampled I and Q signal, and further comprising a code generator for producing each C/A reference code comprising a code look up circuit and a code extender, a first shift register for storing a segment of said subsampled I signal and a second shift register for storing a segment of said subsampled Q signal, a first vector multiplier for producing I partial correlations of said subsampled I signal and a second vector multiplier for producing Q partial correlations of said subsampled Q signal;
a first accumulator for accumulating said I partial correlations to form a full correlation; and
a second accumulator for accumulating said Q partial correlations to form a full correlation;
a signal normalizer for generating normalizer values representative of the magnitude or power of the I and Q signals;
magnitude accumulator for summing the normalizer values.
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Specification