Method and apparatus for performing signal correlation
First Claim
1. A receiver of global positioning system (GPS) signals, comprising:
- an RF/IF converter for filtering and frequency translating received GPS signals having a repeating code to form an IF signal;
a tuner for producing an in-phase (I) signal and a quadrature (Q) signal;
a convolution processor for multiplying portions of a C/A reference code with portions of the repeating code of the I and Q signals to produce a plurality of I and Q inner products;
a first accumulator for accumulating the I inner products over a period less than a period of the repeating code to produce an I correlation;
a second accumulator for accumulating the Q inner products over a period less than a period of the repeating code to produce a Q correlation; and
a signal normalizer for generating normalizer values representative of magnitude or power or the I correlation and the Q correlation.
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Abstract
A method and apparatus for performing signal correlation is described. In one example, portions of a pseudorandom reference code are multiplied with portions of a repeating code of the digital signal to produce a plurality of inner products. The plurality of inner products are then integrated over a period less than a period of the repeating code to produce a correlation result with a broadened frequency response. In another example, the digital signal is correlated with a pseudorandom reference code to produce a first correlation. The digital signal is then correlated with the pseudorandom code reference code to produce a second correlation. The first and second correlations are then used to determine first and second signal delays. The frequency shift of the digital signal is computed using a difference between the first and second signal delays over time.
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Citations
16 Claims
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1. A receiver of global positioning system (GPS) signals, comprising:
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an RF/IF converter for filtering and frequency translating received GPS signals having a repeating code to form an IF signal; a tuner for producing an in-phase (I) signal and a quadrature (Q) signal; a convolution processor for multiplying portions of a C/A reference code with portions of the repeating code of the I and Q signals to produce a plurality of I and Q inner products; a first accumulator for accumulating the I inner products over a period less than a period of the repeating code to produce an I correlation; a second accumulator for accumulating the Q inner products over a period less than a period of the repeating code to produce a Q correlation; and a signal normalizer for generating normalizer values representative of magnitude or power or the I correlation and the Q correlation. - View Dependent Claims (2, 3, 4)
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5. A method of estimating a frequency shift in a digital signal having a repeating code, comprising:
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correlating the digital signal with less than an entire length of a pseudorandom reference code to produce a first correlation; correlating the digital signal with less than an entire length of a pseudorandom reference code to produce a second correlation; determining a first signal delay from the first correlation; determining a second signal delay from the second correlation; and computing the frequency shift using a difference between the first and second signal delays over time. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification