Communications – electrical: acoustic wave systems and devices – Distance or direction finding – With beam steering – scanning – or focussing
Patent
1986-06-30
1999-12-14
Tarcza, Thomas H.
Communications, electrical: acoustic wave systems and devices
Distance or direction finding
With beam steering, scanning, or focussing
367126, 367127, G01S 380
Patent
active
060026456
ABSTRACT:
A method for determining the positions of the N array elements of a random rray to an accuracy sufficient to accomplish beam forming is provided where the initial positions of the array elements are known to an accuracy of .lambda..sub.min/2, and where .lambda..sub.min is the wavelength of the highest frequency of any of the M cohering sources which are in the field of the array and where the relative directions are unknown. The method includes the steps of: identifying M cohering sources in the field of the array, each of which emits at least one narrowband frequency, each frequency differing from the adjacent frequency by 1/T, where T is the time period of the measurements; a device for measuring the true bearing of one of the M sources; receiving the M cohering signals at the N array elements; performing a Fast Fourier Transform (FFT) on each of the N element signals; examining the spectrum of each of the N received signals; and from the N spectra, selecting M (M>3) lowest angular frequencies, .omega..sub.p with the strongest signals.
The method also includes at each .omega..sub.p forming the cross coherence matrix using the formula ##EQU1## where A.sub.pn is the complex Fourier coefficient from element n, the symbol pair indicating time average for each of the M Frequencies, .omega..sub.p ; obtaining the equation
REFERENCES:
patent: 4559605 (1985-12-01), Norsworthy
Fendelman Harvey
Kagan Michael A.
Pihulic Daniel T.
Stan John
Tarcza Thomas H.
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