Method and apparatus for a decimating digital PN correlator
First Claim
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1. In a PN receiver system, an apparatus for digital decimation of a signal returned from a target, said signal being converted by a down converter and being converted to digital form by an analog/digital converter, said apparatus for digital decimation of a signal comprising:
- a decimator coupled to said analog/digital converter, said decimator for producing a decimated signal from said signal returned from said target;
a digital correlator coupled to sid decimator, said digital correlator operating in response to said decimated signal to produce a sinusoidal signal having a frequency equal to a Doppler frequency of said target for correlated ranges and to produce a modulated signal centered at said Doppler frequency of said target for uncorrelated ranges; and
a modulator for transmitting to said target a continuous wave signal modulated by a PN sequence.
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Abstract
A decimating digital PN receiver (10) processes a target return signal. The target return signal is decimated (34) processed at a slower speed. The decimated target return signal is then digitally correlated (28). The correlated signal is digitally filtered (30) and a fast Fourier transform (32) is applied to produce the output (33).
21 Citations
22 Claims
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1. In a PN receiver system, an apparatus for digital decimation of a signal returned from a target, said signal being converted by a down converter and being converted to digital form by an analog/digital converter, said apparatus for digital decimation of a signal comprising:
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a decimator coupled to said analog/digital converter, said decimator for producing a decimated signal from said signal returned from said target; a digital correlator coupled to sid decimator, said digital correlator operating in response to said decimated signal to produce a sinusoidal signal having a frequency equal to a Doppler frequency of said target for correlated ranges and to produce a modulated signal centered at said Doppler frequency of said target for uncorrelated ranges; and a modulator for transmitting to said target a continuous wave signal modulated by a PN sequence. - View Dependent Claims (2, 3, 4, 5, 6, 15, 16, 17, 18, 19)
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7. In a PN receiver system, an apparatus for digital decimation of a signal returned from a target, said signal being converted by a down converter and being converted to digital form by an analog/digital converter, said apparatus for digital decimation of a signal comprising:
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a decimator coupled to said analog/digital converter, said decimator for producing a decimated signal from said signal returned from said target; a digital correlator coupled to said decimator, said digital correlator operating in response to said decimated signal to produce a sinusoidal signal having a frequency equal to a Doppler frequency of said target for correlated ranges and to produce a modulated signal centered at said Doppler frequency of said target for uncorrelated ranges; a first accumulator coupled to said digital correlator, said first accumulator for accumulating said sinusoidal signal and said modulated signal for one PN sequence period and providing a first accumulator output; and a magnitude function coupled to said first accumulator, said magnitude function providing a magnitude of said first accumulator output. - View Dependent Claims (8, 9, 10)
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11. In a PN receiver system, a method for digital decimation of a returned signal returned from a target, said returned signal being down converted and being converted to digital form, said method for digital decimation comprising the steps of:
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digitally decimating said returned signal in digital form to produce a decimated signal; digitally correlating said decimated signal to produce an indication signal of a first kind, if a Doppler frequency of the target is correlated and to produce an indication signal of a second kind, if the Doppler frequency of the target is uncorrelated; ditally attenuating said indication signal, except for said Doppler frequency of said target; and determining a range resolution Δ
R. - View Dependent Claims (12, 13, 14, 20, 21, 22)
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Specification