SONAR SYSTEM

• US 3,613,069 A
• Filed: 09/22/1969
• Issued: 10/12/1971
• Est. Priority Date: 09/22/1969
• Status: Expired due to Term

• Current Assignee: Boyd B. Cary Jr, Francis H. Fenlon
• Original Assignee: Boyd B. Cary Jr, Francis H. Fenlon
• Inventors: Cary, Boyd B. Jr., Fenlon, Francis H.
• Primary Examiner(s): Farley, Richard A.
• Application Number:
  US04/859,675
• Time in Patent Office: 750 Days
• Field of Search: 340/3,5,6,1 181/.5A,.5R
• US Class Current: 367/92
• CPC Class Codes: G01S 15/02 using reflection of acoustic waves G01S15/66 takes precedence
• CPC Class Codes: G01S 15/102 using transmission of pulses having some particular characteristics

Abstract

A sonar system is described which operates by parametrically interacting two ultrasonic waves of different frequency, at least one of which is of finite amplitude. The resulting wave due to the intermodulation component overrides the signal level of the primary waves at long ranges from the sources thereon and has high directivity.

Claims

1. A sonar system which comprises:

a. a pair of sources of acoustic energy of different frequency, at least one of which has a sound pressure level greater than the threshold where underwater nonlinear effects are significant, and b. said sources being disposed along a common axis for launching energy to their respective frequencies in like along a common path along which parameteric interaction of the energy from both sources is produced thereby launching a wave resulting from said interaction having greater energy in the far field distant from said sources than the energy from said sources themselves in said far field, and c. receiving means for deriving an output resulting from the parametric interaction of the acoustic energy from said sources.

2. The invention as set forth in claim 1, wherein the Goldberg number G for the wave produced by said one source at the location thereof is greater than 1.

3. The invention as set forth in claim 2, wherein said Goldberg number is at least 30.

4. The invention as set forth in claim 2, wherein said Goldberg number is in the range of 100.

5. The invention as set forth in claim 1, wherein said one source of said pair of sources produces a pump wave of ultrasonic frequency f1 and the other of said pair of sources generates a mixer wave of frequency f2 wherein:

0.5 n 1 such that the wave resulting from the intermodulation of said pump and mixer wave and equal to the difference frequency thereof has a greater amplitude than said pump and mixer waves in the far field.

6. The invention as set forth in claim 5, wherein said pump wave has a greater sound pressure level than said mixer wave.

7. The invention as set forth in claim 6, wherein said pump wave has a sound pressure level at said pump source of at least 100 db.

8. The invention as set forth in claim 7, wherein said pump wave has a sound level pressure of between 130 db. and 150 db. and said difference frequency is greater than 10 kHz.

9. The invention as set forth in claim 5 wherein said pump source and said mixer source are cylinders with their axes parallel to and disposed along the said common axis and spaced apart so that a highly directive beam at said difference frequency is produced along said common axis.

10. The invention as set forth in claim 1 wherein said pump and mixer sources are separate ultrasonic transducers, a hydrophone disposed along said axis, and signal responsive means coupled to said hydrophone and responsive to the difference frequency wave resulting from said parametric interaction in the far field.

11. The invention as set forth in claim 10, including means for generating electrical signals at said pump wave frequency and at said mixer wave frequency, means for alternately connecting said generating means to said pump and mixer transducers nd said hydrophone to said signal responsive means.

12. The invention as set forth in claim 10, including means for rotating said mixer transducer and said hydrophone about said pump transducer so that said axis revolves about said pump transducer with the center of rotation at said pump transducer.

13. The invention as set forth in claim 1, wherein said pump and mixer sources are separate transducers spaced from each other along said common axis, means for generating electrical signals at said pump wave and mixer wave frequencies, signal responsive means responsive to said difference wave frequency signals, and means for alternately connecting said signal generator to both said transducers and said signal responsive means to said signal transducer.

14. The invention as set forth in claim 13, including means for rotating said signal transducer about said pump transducer.

15. The invention as set forth in claim 13, wherein said transducers are spherical.

16. The invention as set forth in claim 13, wherein said transducers are cylindrical with the axes thereof parallel to each other.