System and method for detecting a narrowband signal
First Claim
1. A system for detecting target frequency within a signal, comprising:
- a first filter having a first center frequency and a first static transfer function, wherein said first center frequency is greater than said target frequency;
a second filter having a second center frequency and a second static transfer function, wherein said second center frequency is less than said target frequency and wherein the phases of said first and second transfer functions differ by 180 degrees about said target frequency; and
a running cross-correlator interconnected to said first and second filters for comparing the output of said first and second filters as said signal is filtered by both said first and second filters over time.
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Abstract
A system for the detection of narrowband signals in wideband noise that combines information across two frequency channels that straddle the frequency of the target signal. Two band pass filters having center frequencies that straddle the frequency of the target signal and that have phase transfer functions that differ by 180 degrees relative to each other at the frequency of the target signal. The presence of the target signal is detected by performing a running cross-correlation of the outputs of saturating, non-linearities that follow from the filters, and determining when the output of the running cross-correlator drops below a predetermined threshold due to the phase shift between the two filter responses caused by the presence of the target signal.
20 Citations
7 Claims
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1. A system for detecting target frequency within a signal, comprising:
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a first filter having a first center frequency and a first static transfer function, wherein said first center frequency is greater than said target frequency; a second filter having a second center frequency and a second static transfer function, wherein said second center frequency is less than said target frequency and wherein the phases of said first and second transfer functions differ by 180 degrees about said target frequency; and a running cross-correlator interconnected to said first and second filters for comparing the output of said first and second filters as said signal is filtered by both said first and second filters over time. - View Dependent Claims (2, 3, 4)
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5. A method for detecting a target frequency within a signal, comprising the steps of:
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(a) providing said signal to a first filter having a first center frequency and a first static transfer function, wherein the first center frequency is lower than said target frequency; (b) simultaneously providing said signal to a second filter having a second center frequency and a second static transfer function, wherein said second center frequency is higher than said target frequency and wherein the phases of said first and second transfer functions differ by 180 degrees about said target frequency; (c) processing the outputs of said first and second filters with a saturating non-linearity component; (d) performing a running cross-correlation of the saturating non-linear outputs of said first and second filters; and (e) determining said signal is present when said running cross-correlation drops below a predetermined threshold. - View Dependent Claims (6, 7)
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Specification