Communications – electrical: acoustic wave systems and devices – Distance or direction finding – By combining or comparing signals
Patent
1977-11-21
1982-06-01
Farley, Richard A.
Communications, electrical: acoustic wave systems and devices
Distance or direction finding
By combining or comparing signals
367122, G01S 380
Patent
active
043331700
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.
REFERENCES:
patent: 3383651 (1968-05-01), Koblick
patent: 3723960 (1973-03-01), Harris
patent: 3864666 (1975-02-01), Douglas
patent: 4017859 (1977-04-01), Medwin
Armstrong Paul R.
Lohman Charles A.
Mathews Lemuel P.
Farley Richard A.
Northrop Corporation
Sokolski Edward A.
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