Method and apparatus for computing signal correlation at multiple resolutions
First Claim
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1. A method for computing correlations of a digital signal with a pseudorandom reference code comprising:
- a) selecting a sample spacing from a plurality of sample spacings;
b) sampling the digital signal to produce a first set of digital signal samples having a first sample spacing;
c) dividing a pseudorandom reference code into a plurality of code segments;
d) selecting a code segment;
e) forming an inner product between said selected code segment and the first set of digital signal samples to produce a partial correlation;
f) repeating steps d) and e) to produce a plurality of partial correlations;
g) summing the plurality of partial correlations as each partial correlation is produced to form a plurality of first 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 method and apparatus is capable of operating in multiple modes of resolution so as to enhance the sensitivity of the convolution processing.
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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) selecting a sample spacing from a plurality of sample spacings;
b) sampling the digital signal to produce a first set of digital signal samples having a first sample spacing;
c) dividing a pseudorandom reference code into a plurality of code segments;
d) selecting a code segment;
e) forming an inner product between said selected code segment and the first set of digital signal samples to produce a partial correlation;
f) repeating steps d) and e) to produce a plurality of partial correlations;
g) summing the plurality of partial correlations as each partial correlation is produced to form a plurality of first correlations. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. 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 signal to form an IF signal;
an analog to digital converter for digitizing said IF signal;
a tuner for removing Doppler shift from said digitized signal and producing an in-phase (I) and a quadrature (Q) signal;
a decimation circuit for subsampling said I and Q signals, said subsampled I and Q signals having either a first sample spacing or a second sample spacing;
a mode selection processor for selecting either said first sample spacing or said second sample spacing; and
a convolution processor for performing convolution operations between a C/A reference code and said subsampled I and Q signals. - View Dependent Claims (11, 12, 13, 14, 16, 17, 18, 19, 20, 21, 22)
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15. Apparatus for computing correlations of a digital signal with a pseudorandom reference code comprising:
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a) means for selecting a sample spacing from a plurality of sample spacings;
b) means for sampling the digital signal to produce a first set of digital signal samples having a first sample spacing;
c) means for dividing a pseudorandom reference code into a plurality of code segments;
d) means for selecting code segments;
e) means for forming inner products between each of said selected code segments and the first set of digital signal samples to produce plurality of partial correlations;
f) means for summing the plurality of partial correlations as each partial correlation is produced to form a plurality of first correlations.
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Specification