Signal processing circuit
First Claim
1. A signal processing circuit particularly adapted for use in the detection of a selected signal against background noise, comprising:
- separate inputs which comprise at least first, second and third inputs which provide respectively the selected signal plus a first noise signal, the selected signal plus a second noise signal, and the selected signal plus a third noise signal, the three noise signals being uncorrelated;
first combining means arranged to produce from the first and second inputs a fourth signal from which the selected signal has been eliminated and which comprises the difference between the first and second noise signals;
second combining means arranged to produce from the second and third inputs a fifth signal from which the selected signal has been eliminated and which comprises the difference between the second and third noise signals;
means arranged to compare the fourth and fifth signals, and when said signals are of the same polarity to select the signal which has an instantaneous value closer to zero, and to present that signal as an instantaneous intermediate output;
means arranged to compare the fourth and fifth signals, and when the two signals are of opposite polarity, to present zero as the said instantaneous intermediate output; and
third combining means by which a selected one of the said inputs is combined with the said intermediate output in a manner tending to eliminate the noise component therein, the output of the third combining means containing the selected signal with a higher signal-to-noise ratio than any of the incoming signals.
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Abstract
In sound target detection equipment, at least three microphones are used in a broadside array manner to ascertain the presence of a selected sound source. The outputs of the three microphones all include the sought signal S and respectively contain noise components X, U and Y. These outputs are combined to provide X-U and X-Y. These two signals are then applied as separate inputs to a discriminator which applies the rules:
(a) when the input signals are both of the same polarity, the discriminator selects the input closer to zero and presents it as the output;
(b) when the input signals are of opposite polarity, the device presents zero as the output.
The output from the discriminator is then subtracted from one of the original microphone outputs in a manner tending to cancel out the noise contents, and the resulting signal examined for the presence of the sought signal S. The invention is applicable also to non-aural signal detection equipment.
15 Citations
12 Claims
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1. A signal processing circuit particularly adapted for use in the detection of a selected signal against background noise, comprising:
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separate inputs which comprise at least first, second and third inputs which provide respectively the selected signal plus a first noise signal, the selected signal plus a second noise signal, and the selected signal plus a third noise signal, the three noise signals being uncorrelated; first combining means arranged to produce from the first and second inputs a fourth signal from which the selected signal has been eliminated and which comprises the difference between the first and second noise signals; second combining means arranged to produce from the second and third inputs a fifth signal from which the selected signal has been eliminated and which comprises the difference between the second and third noise signals; means arranged to compare the fourth and fifth signals, and when said signals are of the same polarity to select the signal which has an instantaneous value closer to zero, and to present that signal as an instantaneous intermediate output; means arranged to compare the fourth and fifth signals, and when the two signals are of opposite polarity, to present zero as the said instantaneous intermediate output; and third combining means by which a selected one of the said inputs is combined with the said intermediate output in a manner tending to eliminate the noise component therein, the output of the third combining means containing the selected signal with a higher signal-to-noise ratio than any of the incoming signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A signal processing circuit particularly adapted for use in the detection of a selected signal against background noise, comprising:
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more than three separate inputs each of which provides the selected signal plus a noise signal, the noise signals of the various inputs being uncorrelated; a plurality of combining means arranged severally to serve different pairs of said inputs and to produce respectively noise difference signals from which the said selected signal is absent; means for combining different pairs of these noise difference signals in discriminators each of which includes means arranged to compare the pair of signals, and when the signals are of the same polarity to select the noise signal which has an instantaneous value closer to zero, and to present that signal as the instantaneous output, and means arranged to compare the pair of signals, and when the signals are of opposite polarity, to present zero as the instantaneous output; and further combining means by which is selected one of the said inputs is combined with an intermediate output derived from the outputs of the discriminators in such a manner as to tend to eliminate the noise component therein, the final signal containing the selected signal with a higher signal-to-noise ratio than any of the incoming signals.
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Specification