Acoustical detection and tracking system
First Claim
1. An acoustical detection system for detecting targets which generate acoustical signals comprising:
- at least one pair of acoustical transducer means for receiving acoustical signals from said targets and transducing said acoustical signals to electrical signals having a plurality of frequency bins, said transducer means being spaced from each other,means for converting said electrical signals from analog signals to digital signals,means for processing said digital signals to generate phase difference signals in accordance with the phase differences between each of the frequency bins of the signals received by said pair of transducer means,means for dividing each of said phase difference signals by a signal in accordance with the frequency of the frequency bin associated therewith to generate phase difference slope signals for each of said frequency bins,means for grouping together signals representing common phase difference slopes, the signals in each such grouping representing signals emanating from a common target, andmeans for processing each of the groupings of signals to determine the direction and identity of each of the targets.
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Accused Products
Abstract
A plurality of acoustical transducers such as microphones are placed in appropriate array so that they are capable of detecting sonic energy emanating from an acoustical source such as an aircraft or a ground vehicle. The outputs of the transducers are sequentially sampled and multiplexed together, the time multiplexed signals then being converted from analog to digital form in an analog/digital converter. The output of the analog/digital converter is fed to a fast Fourier transformer (FFT), which transforms these signals to Fourier transform coefficients represented as real and imaginary (cosine and sine) components. The output of the fast Fourier transformer is fed to a digital processor. In this processor, the power and phase of each frequency bin for each microphone output is determined and the phase differences between signals received by pairs of microphones for each frequency bin of interest are determined. Each of these phase difference signals is divided by the frequency of their associated bin to provide a "phase difference slope" for each frequency bin and for each microphone pair. Signals received by any pair of microphones from the same target (regardless of frequency) have a common phase difference slope. The processor groups all common phase difference slopes together, these individual phase difference slopes each identifying a separate target. The phase difference slopes for each target are used to compute the direction of that target. By using two pairs of microphones in a mutually orthogonal array, target direction in both azimuth and elevation can be computed.
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Citations
13 Claims
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1. An acoustical detection system for detecting targets which generate acoustical signals comprising:
- at least one pair of acoustical transducer means for receiving acoustical signals from said targets and transducing said acoustical signals to electrical signals having a plurality of frequency bins, said transducer means being spaced from each other,
means for converting said electrical signals from analog signals to digital signals, means for processing said digital signals to generate phase difference signals in accordance with the phase differences between each of the frequency bins of the signals received by said pair of transducer means, means for dividing each of said phase difference signals by a signal in accordance with the frequency of the frequency bin associated therewith to generate phase difference slope signals for each of said frequency bins, means for grouping together signals representing common phase difference slopes, the signals in each such grouping representing signals emanating from a common target, and means for processing each of the groupings of signals to determine the direction and identity of each of the targets. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
- at least one pair of acoustical transducer means for receiving acoustical signals from said targets and transducing said acoustical signals to electrical signals having a plurality of frequency bins, said transducer means being spaced from each other,
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11. A method for detecting targets which generate acoustical signals comprising the steps of:
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receiving said acoustical signals with a pair of microphones spaced a predetermined distance from each other, from the outputs of said microphones, computing signals in accordance with the phase for each frequency bin of the signals received by said microphones, computing the phase differences between the signals in accordance with phase from the pair of microphones for each frequency bin, dividing each of said computed phase differences by a signal in accordance with the frequency of the associated frequency bin to provide phase difference slope signals, grouping together phase difference slope signals having common values, whereby each of the grouped signals represents signals emanating from a common target, and processing each of the grouped signals to compute target direction from the value of the phase difference slope and target identity from the frequency composition of the grouped signals. - View Dependent Claims (12, 13)
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Specification