Multiple frequency parametric sonar

Patent metadata

Field	Value
Publication number	US-9523770-B1
Application number	US-201514867177-A
Country	US
Kind code	B1
Filing date	Sep 28, 2015
Priority date	Sep 28, 2015
Publication date	Dec 20, 2016
Grant date	Dec 20, 2016

Abstract

A method of use for parametric sonar is provided that utilizes an acoustic beam formed at a difference frequency generated by non-linear interaction of acoustic energy of primary frequencies. At least three primary frequencies are transmitted from a frequency source by amplifiers and acoustic projectors of the sonar. The non-linear interaction of the primary frequencies produces at least three difference frequencies. The difference frequencies are received by a receiver array. Increased interaction increases efficiency linearly with the number of primary frequencies used. The increased bandwidth resulting from the use of multiple center frequencies can also produce signal processing gains and signal-to-signal ratio is also improved, especially at the lower difference frequencies.

First claim

What is claimed is:

1. A method for producing multiple frequency transmissions with a parametric sonar, said method comprising the steps of:
transmitting at least three distinct primary frequencies from at least one source;
generating a non-linear interaction of acoustic energy at each combination of the distinct primary frequencies;
forming subsequent to said generating step, at least three acoustic beams, each at a difference frequency by the non-linear interaction of acoustic energy; and
receiving the acoustic beams with a receiver array;
wherein six difference frequencies are generated when four primary frequencies are transmitted.

2. A method for producing multiple frequency transmissions with a parametric sonar, said method comprising the steps of:
transmitting at least three distinct primary frequencies from at least one source;
generating a non-linear interaction of acoustic energy at each combination of the distinct primary frequencies;
forming subsequent to said generating step, at least three acoustic beams, each at a difference frequency by the non-linear interaction of acoustic energy; and
receiving the acoustic beams with a receiver array;
wherein ten difference frequencies are generated when five primary frequencies are transmitted.

3. A method for producing multiple frequency transmissions with a parametric sonar, said method comprising the steps of:
transmitting at least three distinct primary frequencies from at least one source;
generating a non-linear interaction of acoustic energy at each combination of the distinct primary frequencies;
forming subsequent to said generating step, at least three acoustic beams, each at a difference frequency by the non-linear interaction of acoustic energy; and
receiving the acoustic beams with a receiver array;
wherein said generating step is performed by at least one amplifier and at least one acoustic projector;
wherein element spacing on the receiver array is λ/ 2 in order to avoid aliasing, where λ=c/f is the wavelength, c is the speed of sound in water and f is the highest difference frequency.

4. The method in accordance with claim 3 wherein the receiver array includes hydrophones evenly spaced along the array such that the receiver array can accommodate multiple frequencies without aliasing.

5. The method in accordance with claim 3 wherein the receiver array includes hydrophones with increasing increments of spacing along the array such that the receiver array can accommodate multiple frequencies without aliasing.

6. The method in accordance with claim 3 wherein the receiver array includes hydrophones with random increments of spacing along the array such that the receiver array can accommodate multiple frequencies without aliasing.

7. A method for producing multiple frequency transmissions with a parametric sonar, said method comprising the steps of:
transmitting at least three distinct primary frequencies from at least one source;
generating a non-linear interaction of acoustic energy at each combination of the distinct primary frequencies;
forming subsequent to said generating step, at least three acoustic beams, each at a difference frequency by the non-linear interaction of acoustic energy; and
receiving the acoustic beams with a receiver array;
wherein said generating step is performed by at least one amplifier and at least one acoustic projector;
wherein element spacing on the receiver array is less than λ/ 2 in order to avoid aliasing, where λ=c/f is the wavelength, c is the speed of sound in water and f is the highest difference frequency;
wherein the receiver array includes hydrophones with increasing increments of spacing along the array such that the receiver array can accommodate multiple frequencies without aliasing.

8. A method for producing multiple frequency transmissions with a parametric sonar, said method comprising the steps of:
transmitting at least three distinct primary frequencies from at least one source;
generating a non-linear interaction of acoustic energy at each combination of the distinct primary frequencies;
forming subsequent to said generating step, at least three acoustic beams, each at a difference frequency by the non-linear interaction of acoustic energy; and
receiving the acoustic beams with a receiver array;
wherein said generating step is performed by at least one amplifier and at least one acoustic projector;
wherein element spacing on the receiver array is less than λ/ 2 in order to avoid aliasing, where λ=c/f is the wavelength, c is the speed of sound in water and f is the highest difference frequency;
wherein the receiver array includes hydrophones with random increments of spacing along the array such that the receiver array can accommodate multiple frequencies without aliasing.

Assignees

• Ruffa Anthony A
• Us Navy

Inventors

• Ruffa Anthony A

Classifications

• G01S15/02 Primary

  using reflection of acoustic waves (G01S15/66 takes precedence) · CPC title

• G01S15/88 Primary

  Sonar systems specially adapted for specific applications (seismic or acoustic prospecting or detecting G01V1/00) · CPC title

• G01S7/527

  Extracting wanted echo signals {(Doppler systems G01S15/50)} · CPC title

• G01S7/536

  Extracting wanted echo signals · CPC title

• G01S7/52003

  Techniques for enhancing spatial resolution of targets (G01S7/52046 takes precedence) · CPC title