METHOD AND ATTENUATOR FOR DETECTION AND ITERATIVE ATTENUATION OF SPIKES IN COMPLEX SIGNALS

• US 20100113951A1
• Filed: 10/20/2009
• Published: 05/06/2010
• Est. Priority Date: 10/20/2008
• Status: Active Grant

• Current Assignee: Neurochip Corporation
• Original Assignee: Neurochip Corporation
• Inventors: Bardakjian, Berj L., Zalay, Osbert C.
• Granted Patent: US 8,868,162 B2
• Time in Patent Office: Days
• US Class Current: 600/509
• CPC Class Codes: G01D 3/032 affecting incoming signal, e.g. by averaging; gating undesired signals

Abstract

A method of attenuating spikes in a complex signal comprises examining the complex signal to detect spikes therein and for each detected spike, generating an estimate inverse signal and applying the estimate inverse signal to the complex signal to attenuate the spike associated with the estimate inverse signal.

Claims

1. A method of attenuating spikes in a complex signal comprising:

examining the complex signal to detect spikes therein; and

for each detected spike, generating an estimate inverse signal; and

applying the estimate inverse signal to the complex signal to attenuate the spike associated with the estimate inverse signal.

2. The method of claim 1 wherein said examining comprises comparing the amplitude of the complex signal with a threshold value to detect spikes in the complex signal.

3. The method of claim 2 wherein the threshold value is a function of the complex signal.

4. The method of claim 3 wherein said threshold value is equal to:

θ

=C√

{square root over ( [{tilde over (x)}(k)]²)}

where C≧

1 and the bar denotes the mean value.

5. The method of claim 1 further comprising, prior to said examining, digitally storing the values of said complex signal in an array and wherein said examining comprises, for each value of said complex signal, comparing the value to a plurality of preceding and subsequent values of said complex signal to determine if said value represents a peak and if so, comparing the value of the complex signal with a threshold value to determine if said value is a spike.

6. The method of claim 5 wherein the threshold value is a function of the complex signal.

7. The method of claim 6 wherein said threshold value is equal to:

θ

=C√

{square root over ( [{tilde over (x)}(k)]²)}

where C≧

1 and the bar denotes the mean value.

8. The method of claim 1 wherein during said generating, a scaled mirror image of the detected spike is generated and wherein said generating and applying are performed iteratively until the amplitude of the detected spike is sufficiently attenuated.

9. The method of claim 8 wherein for each detected spike, said generating and applying comprises:

examining a segment of the complex signal including the detected spike and generating the scaled mirror image;

applying the scaled mirror image to the complex signal segment;

comparing the amplitude of the resultant complex signal segment to a threshold value to determine if the detected spike is sufficiently attenuated; and

repeating the examining, applying and comparing until the detected spike is determined to be sufficiently attenuated.

10. The method of claim 9 wherein during segment examining, an envelope surrounding the detected spike is calculated.

11. The method of claim 10 wherein the calculated envelope is a sigmoidal envelope.

12. The method of claim 5 further comprising, prior to said complex signal examining, applying an offset to each value of said complex signal.

13. The method of claim 12 wherein said offset is a function of said complex signal and removes negative complex signal values.

14. The method of claim 12 further comprising, following said applying, removing the applied offset from the complex signal values.

15. The method of claim 1 further comprising, following said applying, filtering the attenuated complex signal.

16. The method of claim 15 wherein said filtering comprises wavelet or wavelet packet filtering the attenuated complex signal.

28. The method of claim 1 wherein said complex signal is a biological signal.

29. The method of claim 28 wherein said biological signal is one of a neural signal and a cardiac signal.

30. The method of claim 1 wherein said complex signal is one of a noisy and/or an artifact-contaminated communication signal, a mechanical measurement or sensing device signal, an electronic measurement or sensing device signal and an environmental signal.

17. A method of attenuating spikes in a complex signal comprising:

subjecting the complex signal to thresholding to detect spikes in the complex signal having amplitudes greater than a first threshold value; and

subjecting each detected spike to an iterative inverse signal application procedure to attenuate each detected spike so that the amplitude thereof is reduced at least to a second threshold value.

18. The method of claim 17 further comprising, prior to said thresholding, digitally storing the values of said complex signal in an array and wherein said thresholding comprises, for each value of said complex signal, comparing the value to a plurality of preceding and subsequent values of said complex signal to determine if said value represents a peak and if so, comparing the value of the complex signal with the first threshold value to determine if said value is a spike.

19. The method of claim 18 wherein the threshold value is a function of the complex signal.

20. The method of claim 18 wherein said iterative inverse signal application procedure comprises:

examining a segment of the complex signal including the detected spike and generating a scaled mirror image;

applying the scaled mirror image to the complex signal segment;

comparing the amplitude of the resultant complex signal segment to the second threshold value to determine if the detected spike is sufficiently attenuated; and

repeating the examining, applying and comparing until the detected spike is determined to be sufficiently attenuated.

21. The method of claim 20 wherein during segment examining, an envelope surrounding the detected spike is calculated.

22. The method of claim 21 wherein the calculated envelope is a sigmoidal envelope.

23. The method of claim 18 further comprising, prior to said thresholding, applying an offset to each value of said complex signal.

24. The method of claim 23 wherein said offset is a function of said complex signal and removes negative complex signal values.

25. The method of claim 23 further comprising, following said applying, removing the applied offset from the complex signal values.

26. The method of claim 17 further comprising, following said applying, filtering the attenuated complex signal.

27. The method of claim 26 wherein said filtering comprises wavelet or wavelet packet filtering the attenuated complex signal.

31. A computer readable medium embodying a computer program for attenuating spikes in a complex signal, said computer program comprising:

program code for examining the complex signal to detect spikes therein;

program code for generating an estimate inverse signal for each detected spike; and

program code for applying the estimate inverse signal to the complex signal to attenuate the spike associated with the estimate inverse signal.

32. A computer readable medium embodying a computer program for attenuating spikes in a complex signal, said computer program comprising:

program code for subjecting the complex signal to thresholding to detect spikes in the complex signal having amplitudes greater than a first threshold value; and

program code for subjecting each detected spike to an iterative inverse signal application procedure to attenuate each detected spike so that the amplitude thereof is reduced at least to a second threshold value.

33. An attenuator for attenuating spikes in a complex signal comprising:

a spike detector for detecting spikes in the complex signal; and

a spike attenuator for attenuating each detected spike, said spike attenuator generating, for each detected spike, an estimate inverse signal and applying the estimate inverse signal to the complex signal thereby to attenuate the spike associated with the estimate inverse signal.

34. The attenuator of claim 33 wherein said spike detector compares the amplitude of the complex signal with a threshold value to detect spikes in the complex signal.

35. The attenuator of claim 34 wherein the threshold value is a function of the complex signal.

36. The attenuator of claim 33 further comprising a memory array digitally storing the values of said complex signal, said spike detector, for each value of said complex signal, comparing the value to a plurality of preceding and subsequent values of said complex signal to determine if said value represents a peak and if so, comparing the value of the complex signal with a threshold value to determine if said value is a spike.

37. The attenuator of claim 36 wherein the threshold value is a function of the complex signal.

38. The attenuator of claim 33 wherein said spike attenuator generates, for each detected spike, a scaled mirror image and applies the scaled mirror image iteratively to the complex signal until the amplitude of the detected spike is sufficiently attenuated.

39. The attenuator of claim 33 wherein said complex signal is a biological signal.

40. The attenuator of claim 39 wherein said biological signal is one of a neural signal and a cardiac signal.

41. An attenuator for attenuating spikes in a complex signal comprising:

a threshold detector for detecting spikes in the complex signal that have amplitudes greater than a first threshold value; and

an attenuating loop for subjecting each detected spike to an iterative inverse signal application procedure to attenuate each spike to reduce the amplitude thereof to at least a second threshold value.