Communications – electrical: acoustic wave systems and devices – Distance or direction finding – With beam steering – scanning – or focussing
Patent
1994-08-29
1995-10-10
Eldred, J. Woodrow
Communications, electrical: acoustic wave systems and devices
Distance or direction finding
With beam steering, scanning, or focussing
367121, 367124, 367129, 367153, G01S 1500
Patent
active
054576628
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a process and a device making it possible to locate one or more noise emitters using signals gathered by an antenna of unknown geometry consisting of passive acoustic buoys.
Passive acoustic buoys are used, for example, by aircraft for detecting, locating and classifying underwater vehicles. The signal processing methods currently employed for the signals gathered on board the aircraft are essentially non-coherent: that is to say each buoy provides, after detection, measurements of frequency or measurements of frequency and of azimuth; the locating of the targets is performed subsequently using these measurements.
Given the reduction in the noise levels radiated by underwater vehicles, the individual performance of passive buoys, in detection, becomes low and will become even lower with regard to the very quiet underwater vehicles of the future. This is why the development and study of antenna processing methods applicable to an array of buoys (whose positions are poorly known) is important.
Various methods of processing an antenna of hydrophones whose positions are poorly known or even unknown have been proposed over the last fifteen years or so.
A first series of methods uses auxiliary sources whose positions are known. By way of example, such methods are described in the following articles: Dorny, IEEE-AES, November, 1978, pp. 977-991. et al.; IEEE-AES, November, 1980, pp. 902-904.
A second series of methods uses auxiliary sources whose positions are unknown. By way of example, such methods are described in the following articles: Y. Rockah and P. M. Schultheiss, IEEE-ASSP, March, 1987, pp. 286-299 Y. Rockah and P.M. Schultheiss, IEEE-ASSP, June 1987, pp. 724-735.
The auxiliary sources can be, for example, active, that is to say transmitting, buoys. These sources serve to determine the geometry of the antenna and the signals which they transmit must be separated in time or in frequency. Having carried out the calibration of the antenna, the locating of the noise emitters can be carried out by any antenna processing method. The calibration of the antenna can be carried out by triangulation.
The requirement for auxiliary sources in the aforesaid processing methods is constraining in practice and a method making it possible to dispense therewith has been developed. This method applies solely in the case of wide-band signals and its implementation requires the presence of at least three noise emitters. These noise emitters are existing sources of noise, such as ships. This method is described in the following articles: inconnue" ("The locating of point sources with an antenna of unknown geometry") by P. Nicolas and G. Vezzosi, GRETZI 85, pp. 331-337 IEEE-ASSP, June 1986, pp. 405-422 Vezzosi and P. Nicolas, 25th Conf. on Decision and Control", pp. 949-952.
Finally, an antenna processing method dubbed ESPRIT has been developed in the particular case of an array of unknown geometry consisting of two sub-arrays, one of which is the translated version of the other, the translation vector making it possible to transfer from one sub-array to the other being known.
This method is described in the following documents: Paulraj, R. Roy and T. Kailath "Proc of the IEEE "Proc of the IEEE" July 1986, pp. 1044-1045 techniques" by R. Roy and T. Kailath, IEEE-ASSP, July 1989, pp. 984-995
and the U.S. Pat. No. 4,750,147.
However, the implementation of this method requires recourse to servomechanisms in order to perform orientation operations on the various component elements of the antenna.
The invention aims to alleviate the drawbacks just alluded to of the prior art.
It makes it possible to locate several narrowband sources with the aid of an antenna of unknown geometry consisting of buoys using directional hydrophones without any restrictive assumption about the minimum number of noise emitters and about the geometry of the antenna. Neither does it require the addition of auxiliary sources, nor the need for recourse to servomechanisms in order to orient the elements of the antenna. In a pref
REFERENCES:
patent: 5070484 (1991-12-01), Mantel
patent: 5216640 (1993-06-01), Donald et al.
patent: 5339281 (1994-08-01), Narendra et al.
patent: 5357484 (1994-10-01), Bates et al.
patent: 5377162 (1994-12-01), Jestin et al.
"Thomson-CSF"
Eldred J. Woodrow
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