US 5,923,617 AGranted

Frequency-steered acoustic beam forming system and process

AssigneeThe United States of America as represented by the Secretary of the Navy

InventorsR. Lee Thompson, W. J. Zehner

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Abstract

A sonar system includes a pulse generator that produces an electrical signal having a plurality of frequencies. An acoustic radiator formed as a first blazed acoustic array is arranged to be driven by the electrical signal from the pulse generator. The blazed acoustic array includes a plurality of acoustic elements rotated away from the general plane of the array. The acoustic elements are arranged to be driven by the electrical signal from the pulse generator so that they radiate a sonic field that includes a plurality of sonic frequencies with each frequency being radiated at a characteristic angle. An acoustic receiver formed as a second blazed acoustic array is arranged such that components of the acoustic field reflected from the target toward the acoustic receiver produce acoustic waves having frequencies that correspond to the angles of incidence of the reflected acoustic field components. The signals indicative of the reflected frequencies are processed to form an image of the target. The invention may be embodied including phase delay, time delay, or synthetic aperture beamforming means.

Claims10

Dependent claims

A sonar system for detecting a target, comprising:

a pulse generator for producing an electrical signal having a plurality of frequencies f.sub.o, f.sub.l, . . . f.sub.n ;
an acoustic radiator formed as a first blazed acoustic away having a first plurality of acoustic elements arranged in a first stepped array with adjacent acoustic elements being displaced from one another along an axis by a distance .lambda..sub.o that is one acoustic wavelength corresponding to the frequency f.sub.o, the first plurality of acoustic elements being arranged to be driven by the electrical signal from the pulse generator to radiate an acoustic field that includes a plurality of sonic frequencies with each frequency being radiated at a characteristic angle toward the target to be reflected therefrom;
an acoustic receiver formed as a second blazed acoustic array having a second plurality of acoustic elements arranged in a second stepped array with adjacent acoustic elements being displaced from one another along an axis by a distance .lambda..sub.o that is one acoustic wavelength corresponding to the frequency f.sub.o such that components of the acoustic field reflected from the target toward the acoustic receiver produce acoustic waves therein having frequencies that correspond to the angles of incidence of the reflected acoustic field components;
and
means for processing signals indicative of the reflected frequencies to form an image of the target.

2 more elements

The process of frequency steered acoustic beamforming comprising the steps of:

Step 1:
producing a pulsed electrical signal having a plurality of frequencies f.sub.o, f.sub.l, . . . f.sub.n appropriately amplified, filtered, and delayed;
Step 2:
converting said pulsed electrical signal into a frequency-dispersed radiated acoustic field having appropriate directional and delay characteristics and transmitting said acoustic field into an ambient medium containing a target by means of an acoustic radiator formed as a first blazed acoustic away having a first plurality of acoustic elements arranged in a first stepped array with adjacent acoustic elements being displaced from one another along an axis by a distance .lambda..sub.o that is one acoustic wavelength corresponding to the frequency f.sub.o, the first plurality of acoustic elements being arranged to be driven by the electrical signal from the pulse generator to radiate an acoustic field that includes a plurality of sonic frequencies with each frequency being radiated at a characteristic angle toward the target to be reflected therefrom;
Step 3:
receiving a reflected acoustic field from said target and ambient medium by means of an acoustic receiver formed as a second blazed acoustic array having a second plurality of acoustic elements arranged in a second stepped array with adjacent acoustic elements being displaced from one another along an axis by a distance .lambda..sub.o that is one acoustic wavelength corresponding to the frequency f.sub.o such that components of the acoustic field reflected from the target toward the acoustic receiver produce acoustic waves therein having frequencies that correspond to the angles of incidence of the reflected acoustic field components and converting said reflections to electrical signals having appropriate directional and delay characteristics;
and
Step 4:
processing said electrical signals to yield target image data.

6 more elements

Dependencies are inferred from the claim text.