Sonar system having multiple pulse sequences

• US 20060056273A1
• Filed: 09/14/2004
• Published: 03/16/2006
• Est. Priority Date: 09/14/2004
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Scoca, Anthony L., Huber, James G., Klein, Jerry G.
• Granted Patent: US 7,492,666 B2
• Time in Patent Office: Days
• US Class Current: 367/99
• CPC Class Codes: G01S 15/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurement G01S15/32
• CPC Class Codes: G01S 15/101 Particularities of the measurement of distance G01S15/12, G01S15/14, and G01S15/18 take precedence

Abstract

A sonar system comprises a transmitter adapted to provide pulse sequences, wherein each of the pulse sequences includes pulses that reflect off an object, a receiver adapted to receive the reflected pulses, and a processor. The processor is configured to transmit a first pulse sequence via the transmitter to obtain a first distance to the object in a first distance range and to transmit a second pulse sequence via the transmitter to obtain a second distance to the object in a second distance range. The processor is configured to transmit the second pulse sequence in response to being unable to obtain the first distance to the object in the first distance range.

Claims

1. A sonar system, comprising:

a transmitter adapted to provide pulse sequences, wherein each of the pulse sequences includes pulses that reflect off an object;

a receiver adapted to receive the reflected pulses; and

a processor configured to transmit a first pulse sequence via the transmitter to obtain a first distance to the object in a first distance range and to transmit a second pulse sequence via the transmitter to obtain a second distance to the object in a second distance range, wherein the processor is configured to transmit the second pulse sequence in response to being unable to obtain the first distance to the object in the first distance range.

2. The sonar system of claim 1, wherein the processor is configured to transmit a third pulse sequence via the transmitter to obtain a third distance to the object in a third distance range, wherein the processor is configured to transmit the third pulse sequence in response to being unable to obtain at least one of the first distance to the object in the first distance range and the second distance to the object in the second distance range.

3. The sonar system of claim 1, wherein at least one characteristic of the first pulse sequence transmitted by the processor is different than the at least one characteristic of the second pulse sequence transmitted by the processor.

4. The sonar system of claim 3, wherein the at least one characteristic includes at least one of pulse spacing, pulse width, pulse power, and pulse number.

5. The sonar system of claim 1, wherein the processor is configured to open a first receive window following the last pulse in the first pulse sequence and a second receive window following the last pulse in the second pulse sequence.

6. The sonar system of claim 5, wherein a first time between opening the first receive window and the last pulse in the first pulse sequence is different than a second time between opening the second receive window and the last pulse in the second pulse sequence.

7. The sonar system of claim 1, wherein the first pulse sequence comprises a first series of 3 to 10 pulses and the second pulse sequence comprises a second series of 3 to 10 pulses.

8. The sonar system of claim 1, wherein the pulses in the first pulse sequence and the pulses in the second pulse sequence are directed downward to reflect off the ocean bottom.

9. The sonar system of claim 1, wherein the processor is configured to determine the first distance and the second distance based on the time between transmitting pulses via-the transmitter and receiving reflected pulses via the receiver.

10. The sonar system of claim 9, wherein the processor is configured to obtain samples of the received reflected pulses, to digitize the samples of the received reflected pulses, and for selected samples to calculate amplitude correlations of groups of received reflected pulses to calculate a correlation product value.

11. The sonar system of claim 10, wherein the processor is configured to determine a maximum correlation product value for the selected samples, to compare the maximum correlation product value to a correlation product threshold, and if the maximum correlation product value exceeds the correlation product threshold obtain one of the first distance and the second distance based on the selected samples used to calculate the maximum correlation product value.

12. A sonar system, comprising:

a transmitter adapted to provide pulse sequences, wherein each of the pulse sequences includes pulses to reflect off an object;

a receiver adapted to receive the reflected pulses; and

a processor configured to transmit a first pulse sequence via the transmitter and open a first receive window following the last pulse in the first pulse sequence to receive reflected pulses from the first pulse sequence via the receiver and obtain a first distance to the object in a first depth range, and to transmit a second pulse sequence via the transmitter and open a second receive window following the last pulse in the second pulse sequence to receive reflected pulses from the second pulse sequence via the receiver and obtain a second distance to the object in a second distance range.

13. The sonar system of claim 12, wherein pulses in the second pulse sequence are higher energy pulses than pulses in the first pulse sequence, and pulses in the second pulse sequence are spaced further apart than pulses in the first pulse sequence.

14. The sonar system of claim 13, wherein the higher energy pulses are higher power pulses than pulses in the first pulse sequence, and the higher energy pulses are about the same width as pulses in the first pulse sequence.

15. The sonar system of claim 13, wherein a first time from the last pulse in the first pulse sequence to opening the first receive window is shorter than a second time from the last pulse in the second pulse sequence to opening the second receive window.

16. The sonar system of claim 12, wherein pulses in the first pulse sequence are spaced apart in at least two unequal first spacing times, and pulses in the second pulse sequence are spaced apart in at least two unequal second spacing times.

17. The sonar system of claim 12, wherein the processor is configured to transmit a third pulse sequence via the transmitter and open a third receive window following the last pulse in the third pulse sequence to receive reflected pulses from the third pulse sequence via the receiver and obtain a third distance to the object in a third depth range.

18. The sonar system of claim 17, wherein pulses in the third pulse sequence are lower energy pulses than pulses in the first pulse sequence, and pulses in the third pulse sequence are spaced closer together than pulses in the first pulse sequence.

19. The sonar system of claim 18, wherein a third time from the last pulse in the third pulse sequence to opening the third receive window is shorter than a first time from the last pulse in the first pulse sequence to opening the first receive window.

20. A depth detection system, comprising:

a transmitter adapted to provide sonar pulses in sonar pulse sequences;

a receiver adapted to receive reflected sonar pulse signals; and

a processor configured to provide the sonar pulse sequences and process the received reflected sonar pulse signals to obtain a depth candidate, wherein the processor provides an initial sonar pulse sequence to obtain the depth candidate in a first depth range and if unsuccessful in obtaining the depth candidate in the first depth range the processor provides a second sonar pulse sequence to obtain the depth candidate in a second depth range and if unsuccessful in obtaining the depth candidate in the second depth range the processor provides special processing to obtain the depth candidate.

21. The depth detection system of claim 20, wherein the processor provides the initial sonar pulse sequence to obtain the depth candidate in a moderate depth range and the second sonar pulse sequence to obtain the depth candidate in a deep depth range, wherein the moderate depth range is shallower than the deep depth range.

22. The depth detection system of claim 20, wherein the special processing provided by the processor includes sonar pulse sequences adapted to obtain the depth candidate in a moderate depth range, a shallow depth range, and a deep depth range.

23. The depth detection system of claim 20, wherein the special processing provided by the processor protects against obtaining false depth candidates obtained from sonar pulse transmission reverberations.

24. The depth detection system of claim 20, wherein the special processing provided by the processor protects against obtaining false depth candidates from double bounce reflected sonar pulses.

25. The depth detection system of claim 20, wherein the processor is configured to test one or more amplitude levels of the received reflected sonar pulse signals to protect against obtaining false depth candidates.

26. The depth detection system of claim 20, wherein the processor is configured to provide look back processing of the received reflected sonar pulse signals to obtain the depth.

27. The depth detection system of claim 20, wherein the processor is configured to provide a reduced correlation product depth candidate if the processor is unsuccessful in obtaining the depth candidate with the initial pulse sequence, second pulse sequence and special processing.

28. A method for detecting depth, comprising:

transmitting first pulses in a first pulse sequence to search for a first depth candidate in a first depth range; and

transmitting second pulses in a second pulse sequence to search for a second depth candidate in a second depth range if unsuccessful in obtaining the first depth candidate in the first depth range.

29. The method of claim 28, comprising:

correlating amplitudes in reflected first pulse signals to obtain the first depth candidate; and

correlating amplitudes in reflected second pulse signals to obtain the second depth candidate.

30. The method of claim 28, comprising:

transmitting third pulses in a third pulse sequence to search for a third depth candidate in a third depth range if unsuccessful in obtaining the first depth candidate in the first depth range and the second depth candidate in the second depth range.

31. The method of claim 30, comprising:

correlating amplitudes in reflected third pulse signals to obtain the third depth candidate.

32. The method of claim 28, wherein at least one characteristic of the first pulse sequence is different than the at least one characteristic of the second pulse sequence and the at least one characteristic includes at least one of pulse spacing, pulse width, pulse power, and pulse number.

33. The method of claim 28, comprising:

opening a first receive window following the last first pulse in the first pulse sequence; and

opening a second receive window following the last second pulse in the second pulse sequence.

34. The method of claim 33, where a first time from the last first pulse in the first pulse sequence to opening the first receive window is different than a second time from the last second pulse in the second pulse sequence to opening the second receive window.