Sonar system and process

• US 7,330,399 B2
• Filed: 09/01/2006
• Issued: 02/12/2008
• Est. Priority Date: 09/29/2003
• Status: Expired due to Fees

• Current Assignee: Electric Boat Corporation (General Dynamics Corporation)
• Original Assignee: AC Capital Management, Inc.
• Inventors: Freeman, Larry, Green, John, Lerro, Donald, Ashworth, David
• Primary Examiner(s): PIHULIC, DANIEL T
• Application Number:
  US11/514,872
• Publication Number:
  US 20070058488A1
• Time in Patent Office: 529 Days
• Field of Search: 367/99, 367/100, 367/101, 367/102
• US Class Current: 367/99
• CPC Class Codes: G01S 15/003 Bistatic sonar systems; Multistatic sonar systems
• CPC Class Codes: G01S 15/32 using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated

Abstract

A sonar system and method of use capable of discriminating a direct acoustic signal present at 60 dB or more above the acoustic echo signal.

Claims

1. An active sonar system for detecting object(s) in water comprising:

a transmitter capable of continuously transmitting an acoustic signal, comprising a transmit spatial null steering beamforming array, said transmit spatial null steering array forming a transmit spatial null in the direction of said receiver;

a receiver comprising an array of hydrophones having beam forming capability to suppress signals in the direction of the said transmitter, and capable of receiving a reflected acoustic echo of said acoustic signal from said object(s), and a direct acoustic signal from said transmitter;

wherein said receiver is capable of discriminating between said direct acoustic signal and said acoustic echo signal it receives from said object while said transmitter is transmitting; and

whereby said direct acoustic path signal from said transmitter to said receiver is attenuated by both said transmit spatial null and said receive array.

3. The active sonar system of claim 1 wherein said transmitter is transmitting a frequency modulated signal.

4. The active sonar system of claim 3 wherein said transmitter is transmitting a swept frequency modulated signal.

5. The active sonar system of claim 3 wherein said transmitter is transmitting a linear swept frequency modulated signal.

6. The active sonar system of claim 3 wherein said transmitter is transmitting a swept frequency modulated signal wherein the transmitted sweep is amplitude tapered at the beginning and end of each sweep.

7. The active sonar system of claim 3 wherein the frequency modulated signal is amplitude tapered.

8. The active sonar system of claim 3 wherein said transmitter is transmitting a frequency modulated signal which is frequency shift keyed.

9. The active sonar system of claim 3 wherein said transmitter is transmitting a hyperbolic swept frequency modulated signal.

10. The active sonar system of claim 9 wherein said frequency modulated signal is amplitude tapered.

11. The active sonar system of claim 1 wherein said transmitter is transmitting a single frequency continuous wave.

12. The active sonar system of claim 1 wherein said receiver comprises a vector sensor or array of vector sensors.

13. The active sonar system of claim 1 wherein said receiver has a dynamic range greater than about 80 dB.

14. The active sonar system of claim 1 wherein said discrimination capability is achieved, in part, by temporal frequency filtering.

15. The active sonar system of claim 1, wherein said system is capable of detecting an object beneath an ocean floor.

16. The active sonar system according to claim 1, wherein said acoustic signals comprise multi-frequency acoustic tone.

17. The active sonar system according to claim 1, wherein said discriminating between said acoustic signals includes bearing, range and/or frequency domains.

2. The active sonar system of claim wherein said transmitter is continuously transmitting said acoustic signal.

18. A method for detecting sonar signals comprising:

transmitting an acoustic signal utilizing a transmit spatial null steering beamforming array;

receiving, utilizing an array of hydrophones having beam forming capability to suppress signals in the direction of the said transmitter during said transmission of said acoustic signal, a reflected acoustic echo of said acoustic signal from object(s), as well as directly receiving said acoustic signal;

processing a signal of said acoustic echo and said direct acoustic signal in a manner to discriminate between said acoustic echo signal and said direct signal x hen said direct acoustic signal is present at 60 dB or more above the acoustic echo signal.

19. The method according to claim 18, wherein said transmitting is accomplished by emitting a single frequency continuous wave.

20. The method according to claim 18, wherein said receiving is accomplished by using a vector sensor or an array of vector sensors.

21. The method according to claim 18, wherein said discriminating is accomplished, in part, by performing temporal frequency filtering.

22. A method for detecting sonar signals comprising:

generating an acoustic waveform;

performing waveform shaping;

transmitting said waveform acoustically;

directly receiving said acoustic waveform and reflected echoes of said acoustic waveform;

performing temporal frequency rejection on said received acoustic waveforms;

attenuating said directly received acoustic waveform by both an array of hydrophones having beam forming capability to suppress signals in the direction of the said transmitter and a transmit spatial null in the direction of said receive spatial null steering beamforming array.

23. The method according to claim 22, wherein said shaping is accomplished by performing amplitude tapering.