Broadband sonar method and apparatus for use with conventional sonar sensor arrays

• US 5,822,276 A
• Filed: 05/02/1997
• Issued: 10/13/1998
• Est. Priority Date: 07/31/1995
• Status: Expired due to Term

• Current Assignee: Leidos, Inc. (Leidos Holdings, Inc.)
• Original Assignee: Arete Engineering Technologies Corporation
• Inventors: Miklovic, Donald W.
• Primary Examiner(s): Lobo, Ian J.
• Application Number:
  US08/850,072
• Time in Patent Office: 529 Days
• Field of Search: 367/103, 367/119, 367/901
• US Class Current: 367/103
• CPC Class Codes: G01S 15/8927 using simultaneously or sequentially two or more subarrays or subapertures
• CPC Class Codes: G01S 3/8083 determining direction of source
• CPC Class Codes: G10K 11/346 using phase variation
• CPC Class Codes: Y10S 367/901 Noise or unwanted signal reduction in nonseismic receiving system

Abstract

A broadband sonar system is configured to be coupled to a narrow band sonar sensor array having a plurality of sensor groups configured in subarrays. Each of the sensor groups within a subarray is spaced equidistantly from adjacent sensor groups within the same subarray. The sonar system includes a plurality of signal compensation filters, each being coupled to a respective one of the sensor groups for receiving signals from the respective sensor group and weighting the signals to generate respective output signals. The weighting of the signal from a first sensor group having a first SNR is greater than the weighting for the signal from a second sensor group that has a second SNR when the first SNR is greater than the second SNR, so as to maximize the SNR of the array. At least one broadband beamformer is coupled to the signal compensation filters for combining the output signals for determining ranges to targets.

Claims

1. A broadband sonar system, configured to be coupled to a narrow band sonar sensor array having a plurality of sensor groups configured in subarrays, each of the sensor groups within a subarray being spaced equidistantly from adjacent sensor groups within the same subarray, including:

a plurality of signal compensation filters each being coupled to a respective one of the sensor groups for receiving signals from the respective sensor group and weighting the signals to generate respective output signals, the weighting of the signal from a first sensor group having a first signal to noise ratio being greater than the weighting for the signal from a second sensor group having, a second signal to noise ratio when the second signal to noise ratio is less than the first signal to noise ratio so as to maximize the signal to noise ratio of the array; and

at least one broadband beamformer coupled to the signal compensation filters for combining the output signals for determining ranges to targets.

2. A broadband sonar system configured to be coupled to a narrow band sonar sensor array having a plurality of sensor groups configured in subarrays characterized by at least one design frequency, each of the sensor groups within a subarray being spaced equidistantly from adjacent sensor groups within the same subarray, the system defining a broadside direction, the system comprising:

a plurality of filters each being coupled to a respective one of the sensor groups and each having a transfer function that is dependent on beam angle relative to broadside, and frequency of signals received from the respective sensor group to compensate for varying attenuation of signals received by the sensor groups at beam angles off broadside at frequencies above the design frequency so as to maximize the signal to noise ratio of the array;

at least one broadband beamformer coupled to the signal compensation filters for combining the output signals for use in determining ranges to targets.

3. The system of claim 2, wherein each of the filters has a transfer function of (1/N_G) times the sum from n=1 to N_G of Σ

e^-i2π

(f/c)sinθ

(x(n)-x), where N_G is the number of sensors in each sensor group, f is frequency in Hertz, c is the speed of sound within a medium surrounding the system, θ

is the bearing of the beam angle relative to a broadside, x(n) is a position of an n^th sensor with the sensor group, x is the acoustic center of the group, and wherein a positive θ

beam is in the direction of increasing x, and positive Fourier transform convention is used.

4. A broadband sonar system, including:

a narrow band sonar sensor array including;

a plurality of sensor groups configured in subarrays, each of the sensor groups within a subarray being spaced equidistantly from adjacent sensor groups within the same subarray;

a plurality of signal compensation filters each being coupled to a respective one of the sensor groups for receiving signals from the respective sensor group and generating respective output signals compensating for effects of the respective sensor group such that signals from sensor groups having relatively high signal to noise ratios are weighted more than signals from sensor groups having relatively low signal to noise ratios; and

at least one broadband beamformer coupled to the signal compensation filters for combining, the output signals for determining ranges to targets.

5. A method for combining broadband signals received from a plurality of sensors arranged to form subarrays defining a broadside direction to determine a range to at least one target, including the step 3 of:

receiving broadband signals from the sensors;

applying the received signals to at least a first filter having a first output to establish a first weight when the received signals are from a beam direction relatively close to broadside;

applying the received signals to at least a second filter having a second output to establish a second weight when the received signals are from a beam direction relatively far from broadside, the first weight being greater than the second weight; and

combining the first and second outputs to maximize the signal to noise ratio of the array to generate an output signal representative of range to at least one target.