Method for enhancing signal-to-noise ratio and resolution of amplitude stable signals

• US 5,886,951 A
• Filed: 08/27/1997
• Issued: 03/23/1999
• Est. Priority Date: 08/27/1997
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: The United States of America As Represented By The Secretary of Agriculture
• Inventors: Wagstaff, Ronald A., Gardner, Susan D.
• Primary Examiner(s): Pihulic, Daniel T.
• Application Number:
  US08/917,964
• Time in Patent Office: 573 Days
• Field of Search: 367/135, 367/136, 367/103, 367/105, 367/119, 367/121, 367/123, 367/124, 367/125, 367/129, 367/901, 364/724.06, 364/724.08, 364/726.01, 364/726.02, 364/726.03, 364/574
• US Class Current: 367/135
• CPC Class Codes: G01S 3/8006 Multi-channel systems specially adapted for direction-finding, i.e. having a single aerial system capable of giving simultaneous indications of the directions of different signals
• CPC Class Codes: Y10S 367/901 Noise or unwanted signal reduction in nonseismic receiving system

Abstract

A method for enhancing signal-to-noise ratio and resolution of amplitude stable signals wherein underwater acoustic data is first collected with an array of hydrophones, and then the data is digitally sampled. After producing spectra of sequential time snapshots of the digitally-sampled data, the spectra are beamformed for a single frequency. Next the low resolution beamformer response is deconvolved from the data by use of a calculated beam response pattern for the hydrophone array, so that many high-resolution estimates are created for each time snapshot. Finally, the resulting high resolution estimates are reduced to a single estimate for each spatial bin across all of the time snapshots, and the high resolution, high gain results are displayed.

Claims

1. A method for enhancing signal-to-noise ratio and resolution of amplitude stable signals, comprising the steps of:

(a) collecting underwater acoustic data with an array of hydrophones;

(b) digitally sampling the data;

(c) producing spectra of sequential time snapshots of the digitally-sampled data;

(d) beamforming the spectra for a single frequency;

(e) deconvolving the low resolution beamformer response from the data by use of a calculated beam response pattern for the hydrophone array, so that many high-resolution estimates are created for each time snapshot;

(f) reducing the resulting high resolution estimates to a single estimate for each spatial bin across all of the time snapshots; and

(g) displaying the high resolution, high gain results.

2. The method of claim 1 wherein step(e) includes the steps of:

estimating the power spectral density for each spatial bin from sequential time snapshots.

3. The method of claim 2 wherein step (e) includes the step of:

calculating the beam response pattern of the hydrophone array with fine spatial sampling.

4. The method of claim 3 wherein step (e) includes the step of:

inverting and elevating the beam response pattern for each power spatial density estimate from all time snapshots,

whereby multiple high resolution spatial density estimates are created for each original beam and time snapshot.

5. The method of claim 1 wherein step (f) is accomplished with a WISPR filter.

6. The method of claim 5, wherein the equation for the WISPR Filter power, W(x), ##EQU6## Where N is the total number of data points in an input data set, and X_i represents the ith realization of the power.

7. The method of claim 1 wherein step (g) is accomplished with an AWSUM filter.

8. The method of claim 7, wherein the equation for the AWSUM Filter power, A(x), is:

##EQU7## where N is the total number of data points in an input data set, x_i represents the ith realization of the power, and a, the order of the sum, is a real number greater than zero.

9. The method of claim 1 wherein step (d) is accomplished with a double fast Fourier transform beamformer.

10. The method of claim 1 wherein step (c) is accomplished with a spectrum analyzer.