Receiver and method for blind adaptive thresholding using noise estimator

• US 7,447,276 B1
• Filed: 08/29/2007
• Issued: 11/04/2008
• Est. Priority Date: 08/29/2007
• Status: Expired due to Fees

• Current Assignee: North South Holdings Incorporated (Spherix Incorporated)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Beadle, Edward R.
• Primary Examiner(s): Bocure; Tesfaldet
• Application Number:
  US11/846,616
• Time in Patent Office: 433 Days
• Field of Search: 375/316, 375/346, 375/285, 375/347, 375/260, 455/132
• US Class Current: 375/316
• CPC Class Codes: H04B 1/70755 Setting of lock conditions, e.g. threshold
• CPC Class Codes: H04L 2025/03426 transmission using multiple-input and multiple-output channels
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/022 of frequency response
• CPC Class Codes: H04L 25/0238 using blind estimation
• CPC Class Codes: H04L 25/0248 Eigen-space methods
• CPC Class Codes: H04L 25/062 Setting decision thresholds using feedforward techniques only

Abstract

A receiver estimates noise power and establishes a false alarm detector threshold. The receiver includes an antenna array having a plurality of antenna subarrays on which multiple communications signals are received over a communications channel. At least one channelizer splits the communications signal into multiple frequency sub-bands per subarray, each having a channel output. At least one noise estimator and detector is operative at the channel outputs for estimating noise power and setting a detector threshold used in detecting false alarms by forming a temporal covariance matrix on each channel output, performing an eigenvalue decomposition on the temporal covariance matrix, selecting candidate channels using the eigenvalue spread per channel, computing a noise power estimate from the candidate channels and setting a detector threshold for detecting false alarms based on the noise power estimate.

Claims

1. A receiver for estimating noise power and establishing a false alarm detector threshold, comprising:

an antenna array comprising a plurality of antenna subarrays on which multiple communications signals are received over a communications channel;

at least one channelizer for splitting the communications signal into multiple frequency sub-bands per subarray, each having a channel output; and

at least one noise estimator and detector operative at said channel outputs for estimating noise power and setting a detector threshold used in detecting false alarms by forming a temporal covariance matrix on each channel output, performing an eigenvalue decomposition on the temporal covariance matrix, selecting candidate channels using the eigenvalue spread per channel, computing a noise power estimate from the candidate channels and setting a detector threshold for detecting false alarms based on the noise power estimate.

2. The receiver according to claim 1, wherein said at least one noise estimator and detector is operative for estimating noise on a 2×

2 per space-frequency-polarized channel.

3. The receiver according to claim 1, and further comprising a Constant False Alarm Rate (CFAR) detector that detects and filters false alarms based on the detector threshold.

4. The receiver according to claim 1, wherein one subarray is selected for estimating noise.

5. The receiver according to claim 1, wherein each channel output includes a noise estimator and detector.

6. The receiver according to claim 1, wherein at least one noise estimator and detector is distributed at each frequency sub-band.

7. The receiver according to claim 1, and further comprising a plurality of processing and detection layers having at least one noise estimator and detector for scaling a noise level by bandwidth ratios.

8. The receiver according to claim 1, wherein said at least one noise estimator and detector is operative for decomposing a correlation matrix without an eigenvalue computation using quadratic factoring results.

9. The receiver according to claim 1, wherein at least one noise estimator and detector is operative for pooling candidate channels.

10. A receiver for estimating noise power and establishing a false alarm detector threshold, comprising:

an antenna array comprising a plurality of antenna subarrays on which multiple communications signals are received over a communications channel;

at least one channelizer for splitting the communications signal into multiple frequency sub-bands per subarray, each having a channel output; and

at least one noise estimator and detector operative at said channel outputs for estimating noise power and setting a detector threshold used for detecting false alarms by forming a temporal covariance matrix on each channel output, performing an eigenvalue decomposition on the temporal covariance matrix, selecting candidate channels using the eigenvalue spread per channel, computing a noise power estimate from the candidate channels and setting a detector threshold for detecting false alarms based on the noise power estimate, and further comprising a circuit that updates the noise estimate based on dwell data.

11. The receiver according to claim 10, wherein said circuit for updating the noise estimate comprises a filter set to unity gain.

12. The receiver according to claim 10, wherein said at least one noise estimator and detector is operative for estimating noise on a 2×

2 per space-frequency-polarized channel.

13. The receiver according to claim 10, and further comprising a constant false alarm rate (CFAR) detector that detects and filters false alarms based on the detector threshold.

14. The receiver according to claim 10, wherein one subarray is selected for estimating noise.

15. The receiver according to claim 10, wherein each channel output includes a noise estimator and detector.

16. The receiver according to claim 10, wherein at least one noise estimator and detector is distributed at each frequency sub-band.

17. The receiver according to claim 10, and further comprising a plurality of processing and detection layers having at least one noise estimator and detector for scaling a noise level by bandwidth ratios.

18. The receiver according to claim 10, wherein said at least one noise estimator and detector is operative for decomposing a correlation matrix without an eigenvalue computation using quadratic factoring results.

19. The receiver according to claim 10, wherein at least one noise estimator and detector is operative for pooling candidate channels.

20. A method for estimating noise power and establishing a threshold for communications signals received over a communications channel, comprising:

receiving multiple communications signals within an antenna array comprising a plurality of antenna subarrays;

splitting the communications signals into multiple frequency sub-bands per subarray, each having a channel output; and

estimating noise power and setting a detector threshold used in detecting false alarms by forming a temporal covariance matrix on each channel output, performing an eigenvalue decomposition on the temporal covariance matrix, selecting candidate channels using the eigenvalue spread per channel, computing a noise power estimate from the candidate channels and setting a detector threshold for detecting false alarms based on the noise power estimate.

21. The method according to claim 20, which further comprises estimating the noise on a 2×

2 per space-frequency-polarized channel.

22. The method according to claim 20, which further comprises decomposing a correlation matrix without an eigenvalue computation using quadratic factoring results.