Coherent signal power detector using higher-order statistics

• US 5,515,300 A
• Filed: 09/30/1993
• Issued: 05/07/1996
• Est. Priority Date: 09/30/1993
• Status: Expired due to Fees

• Current Assignee: The Government Of The United States As Represented By The Secretary Of The Navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Pierce, Robert D.
• Primary Examiner(s): Cosimano, Edward R.
• Application Number:
  US08/129,500
• Time in Patent Office: 950 Days
• Field of Search: 364/554, 364/574, 364/724.06, 364/522, 364/524, 342/192, 342/116, 342/160, 342/196, 375/55, 375/94, 324/76.19, 324/76.21, 324/76.38
• US Class Current: 702/190
• CPC Class Codes: G01H 3/08 Analysing frequencies present in complex vibrations, e.g. comparing harmonics present acoustic presence detection G01V1/001
• CPC Class Codes: G01S 7/5273 using digital techniques
• CPC Class Codes: G01V 1/288 Event detection in seismic signals, e.g. microseismics G01V1/36 takes precedence

Abstract

A signal detection system divides a data sampling run into blocks and perms a fast Fourier transform on each block, sorting results by frequency. Combinations of results of the fast Fourier transform corresponding to each frequency are processed to derive a test statistic which is unbiased by Gaussian noise while including such combinations of results of the fast Fourier transform which would be redundant over other combinations. Information concerning the frequency behavior of the signal derived in the course of detection, is accomplished with increased sensitivity.

Claims

1. In a method for detection of a signal in a noisy environment including computation of a test statistic from a list of combinations of values in blocks of signals sampled from said noisy environment, the steps of:

dividing a run of the sampled signals into said blocks, performing a fast Fourier transform on each of said blocks, sorting results of said fast Fourier transform by frequency, eliminating combinations of said results which are redundant, excluding from said list combinations of the results derived from the sampled signals in which noise is present, and determining said detection of the signal based on the test statistic computed only from the combinations of said results remaining after said steps of eliminating and excluding the combinations of the results which are redundant and/or in which the noise is present.

2. A method as recited in claim 1 wherein said sampled signals are returned to a receiver by reflection.

3. A method as recited in claim 1, including the further step of

obtaining said run of the sampled signals by dividing a longer run of the sampled signals.

4. A method as recited in claim 3, including the further step of

reducing spectral resolution of said fast Fourier transform.

5. The method as defined in claim 1 wherein the signal detected is propagated from an unknown source through a medium within which said noisy environment is established.

6. The method as defined in claim 5 wherein said medium is water.

7. In a signal detection method including computation of test statistics from combinations of values in blocks of signals which remain after combinations which are redundant are eliminated and combinations of signals in which noise is present are excluded, the improvement residing in:

sampling signals propagated from targets to be detected through a noisy environment to include information on frequency behavior of the signals characterizing said targets;

sorting the blocks of the sampled signals according to frequency thereof; and

limiting said computation of the test statistics to the frequency sorted blocks of the sampled signals from which the information on the frequency behavior of the signals propagated from the targets is extracted.

8. The method as defined in claim 7 wherein said noisy environment is seawater within which the targets are located, and said step of sampling the signals is performed within a seagoing vessel.

9. The method as defined in claim 7 including the further step of performing a fast Fourier transform on said blocks of the sampled signals before said step of sorting.

10. The method as defined in claim 9 wherein said noisy environment is seawater within which the targets are located.

11. The method as defined in claim 10 wherein the signals propagated through the seawater are acoustic sounds.

12. The method as defined in claim 11 wherein said step of sampling the signals is performed within a seagoing vessel.