Multiple carrier adaptive notch filter

• US 6,718,166 B2
• Filed: 05/17/2002
• Issued: 04/06/2004
• Est. Priority Date: 05/17/2002
• Status: Expired due to Term

• Current Assignee: ISCO International Inc.
• Original Assignee: Illinois Superconductor Corporation
• Inventors: Nguyen, Tan D., Cordone, Sean S.
• Primary Examiner(s): Vo, Nguyen T.
• Assistant Examiner(s): Nguyen, Thuan T.
• Application Number:
  US10/151,648
• Publication Number:
  US 20030216122A1
• Time in Patent Office: 690 Days
• Field of Search: 455/306, 455/63.1, 455/213, 455/296, 455/501, 455/513, 455/67.11, 455/67.13, 455/114.2, 455/115.1, 455/115.3, 455/134, 455/135, 455/226.1, 455/226.2
• US Class Current: 455/306
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04B 1/1036 with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters H04B1/123 takes precedence; filter circuits H03H
• CPC Class Codes: H04B 1/123 using adaptive balancing or compensation means adaptive filter circuits and algorithms H03H
• CPC Class Codes: H04B 1/71 the interference being narrowband interference

Abstract

A multiple carrier adaptive notch filter (ANF) module selectively filters a received wideband communication signal to eliminate narrowband interference that lies within the frequency spectrum of the wideband communication signal. To determine the presence of narrowband interference, the multiple carrier ANF module scans various known narrowband channels that lie within the frequency spectrum of the wideband communication signal and determines signal strengths for each of the narrowband channels. The signal strengths from the narrowband channels are compared to a threshold that is derived from a statistical combination of the narrowband signal strengths. Narrowband channels having signal strengths that are greater than the threshold are determined to have interference.

Claims

1. A method of detecting narrowband interference in a first wideband communication signal having a frequency bandwidth with narrowband channels disposed therein, the method comprising:

scanning at least some of the narrowband channels to determine signal strengths in at least some of the narrowband channels;

weighting a signal strength of at least one of the narrowband channels by a first weight to get a first weighted signal strength;

determining a threshold based on a statistical combination of the signal strengths of more than one of the narrowband channels including the first weighted signal strength; and

identifying the narrowband channels having signal strengths exceeding the threshold.

2. A method as defined in claim 1, wherein weighting the signal strength comprises multiplying a signal strength of a first narrowband channel near a first edge of the first wideband communication signal by the first weight to get a first edge weighted signal strength.

3. A method as defined in claim 2, wherein weighting the signal strength further comprises multiplying a signal strength of a second narrowband channel near a second edge of the first wideband communication signal by a second weight to get a second edge weighted signal strength.

4. A method as defined in claim 3, wherein the first weight is equal to the second weight.

5. A method as defined in claim 3, wherein the first weight and the second weight has a value of eight.

6. A method as defined in claim 3, wherein the value of the first weight and the value of the second weight is determined based on signal strengths of at least some of the narrowband channels.

7. A method as defined in claim 3, wherein the value of the first weight and the value of the second weight is determined based on signal strength of the first wideband communication signal.

8. A method as defined in claim 3, wherein the threshold is determined by adding the first edge weighted signal strength, the second edge weighted signal strength, and a statistical combination the signal strengths of the narrowband channels disposed within the first wideband communication signal other than the first narrowband channel and the second narrowband channel, to get a first weighted sum of narrowband channel signal strengths, and dividing the first weighted sum of narrowband channel signal strengths by the first total number of narrowband channels disposed within the first wideband communication signal.

9. A method as defined in claim 1, wherein determining the threshold comprises adding an offset to the statistical combination of the signal strengths of more than one of the narrowband channels including the first weighted signal strength.

10. A method as defined in claim 1, wherein determining the threshold comprises omitting a first number of largest narrowband signal strengths in the statistical combination of the signal strengths of more than one of the narrowband channels.

11. A method as defined in claim 1, wherein the first wideband communication signal has one or more adjacent wideband communication signals.

12. A method as defined in claim 1, further comprising filtering the first wideband communication signal for at least one frequency corresponding to a narrowband channel having a signal strength exceeding the threshold.

13. A method as defined in claim 12, wherein filtering the first wideband communication signal comprises filtering only a first set of narrowband channels having highest signal strengths among all the narrowband channels having signal strengths exceeding the threshold.

14. A method as defined in claim 12, wherein filtering the first wideband communication signal comprises filtering only a second set of narrowband channels selected based on a difference in signal strength between the signal strengths of the first wideband communication signal and the signal strength of the narrowband channel.

15. A method as defined in claim 12, wherein the narrowband channel having a signal strength exceeding the threshold is filtered for a first bandwidth of the narrowband channel.

16. A method as defined in claim 12, wherein the narrowband channel is filtered only if the narrowband channel is identified as having a signal strength exceeding the threshold for at least a first time duration.

17. A method as defined in claim 12, wherein the narrowband channel is filtered only if the narrowband channel is identified as having a signal strength exceeding the threshold for a first number of occurrences.

18. A method as defined in claim 12, wherein the first wideband communication signal is a CDMA carrier signal.

19. A method as defined in claim 15, wherein the first bandwidth of the narrowband channel comprises a variable bandwidth.

20. A method as defined in claim 16, wherein the first time duration comprises a variable time duration.

21. A method as defined in claim 17, wherein the first number of occurrences comprises a variable number of occurrences.

22. A system adapted to detect narrowband interference in a first wideband communication signal having a frequency bandwidth with narrowband channels disposed therein, the system comprising:

a scanner adapted to scan at least some of the narrowband channels to determine signal strengths in at least some of the narrowband channels;

a controller coupled to the scanner, and adapted to control the scanner to scan at least some of the narrowband channels to determine signal strengths in at least some of the narrowband channels, to weight signal strength of at least one of the narrowband channels by a first weight to get a first weighted signal strength, to determine a threshold based on a statistical combination of the signal strengths of more than one of the narrowband channels including the first weighted signal strength, and to identify the narrowband channels having signal strengths exceeding the threshold.

23. The system of claim 22, further comprising a notch module coupled to the controller module and adapted to receive the first wideband communication signal and to selectively filter at least one frequency corresponding to a narrowband channel having a signal strength exceeding the threshold.

24. The system of claim 22, wherein the controller is further adapted to multiply a signal strength of a first narrowband channel near a first edge of the first wideband communication signal by the first weight to get a first edge weighted signal strength.

25. The system of claim 22, wherein the controller determines the threshold by adding an offset to the statistical combination of the signal strengths of more than one of the narrowband channels including the first weighted signal strength.

26. The system of claim 22, wherein the controller omits a first number of largest narrowband signal strengths in the statistical combination of the signal strengths of more than one of the narrowband channels.

27. The system of claim 22, wherein the controller is adapted to have one or more wideband communication signals adjacent to the first wideband communication signal.

28. The system of claim 24, wherein the controller is further adapted to multiply a signal strength of a second narrowband channel near a second edge of the first wideband communication signal by a second weight to get a second edge weighted signal strength.

29. The system of claim 28, wherein the first weight is equal to the second weight.

30. The system of claim 28, wherein the first, weight and the second weight has a value of eight.

31. The system of claim 28, wherein the value of the first weight and the value of the second weight is determined based on signal strengths of at least some of the narrowband channels.

32. The system of claim 28, wherein the value of the first weight and the value of the second weight is determined based on signal strength of the first wideband communication signal.

33. The system of claim 28, wherein the threshold is determined by adding the first edge weighted signal strength, the second edge weighted signal strength, and a statistical combination the signal strengths of the narrowband channels disposed within the first wideband communication signal other than the first narrowband channel and the second narrowband channel, to get a first weighted sum of narrowband channel signal strengths, and dividing the first weighted sum of narrowband channel signal strengths by the first total number of narrowband channels disposed within the first wideband communication signal.

34. The system of claim 23, wherein the notch module filters only a first set of narrowband channels having highest signal strength among all the narrowband channels having a signal strengths exceeding the threshold.

35. The system of claim 23, wherein the notch module filters only a second set of narrowband channels selected based on a difference in signal strength between the signal strength of the first wideband communication signal and the signal strength of the narrowband channel.

36. The system of claim 23, wherein the notch module filters a frequency corresponding to a narrowband channel having a signal strength exceeding the threshold for a first bandwidth of the narrowband channel.

37. The system of claim 23, wherein the notch module filters a frequency corresponding to a narrowband channel if the narrowband is identified as having a signal strength exceeding the threshold for at least a first time duration.

38. The system of claim 23, wherein the first time duration comprises a variable time duration.

39. The system of claim 23, wherein the notch module filters a frequency corresponding to a narrowband channel only if the narrowband channel is identified as having a signal strength exceeding the threshold for a first number of occurrences.

40. The system of claim 23, wherein the notch module is a first notch module and the filtered wideband communication signal is a first filtered wideband communication signal, the system further comprising a second notch module adapted to receive the first filtered wideband communication signal from the first notch module and to selectively filter the first filtered wideband communication signal at a frequency corresponding to a narrowband channel having a signal strength that exceeds the threshold to produce a second filtered wideband communication signal.

41. The system of claim 23, wherein the first wideband communication signal is a CDMA carrier signal.

42. The system of claim 33, wherein the first bandwidth of the narrowband channel comprises a variable bandwidth.

43. The system of claim 34, wherein the first number of occurrences comprises a variable number or occurrences.

44. A method for detecting narrowband interference in a multicarrier communication signal including a plurality of carriers, wherein each carrier has a plurality of narrowband channels disposed therein, the method comprising:

scanning a number of narrowband channels associated with a selected carrier of the plurality of carriers to determine signal strengths for the number of scanned narrowband channels within the selected carrier;

identifying a number of narrowband channels having the largest signal strengths within a bandwidth of the multicarrier communication signal;

determining a number of narrowband channels identified as having the largest signal strengths within the bandwidth of the multicarrier communication signal that lie within a bandwidth of the selected carrier;

determining a weighted sum of the signal strengths of the narrowband channels associated with the selected carrier, the weighted sum not including the signal strengths of the number of narrowband channels having the largest signal strengths that lie with the bandwidth of the selected carrier;

determining a threshold for the selected carrier by dividing the weighted sum by a difference between the number of narrowband channels scanned within the selected carrier and the number of narrowband channels having the largest signal strengths that lie within the bandwidth of the selected carrier and adding an offset thereto;

comparing to the threshold the signal strengths for each narrowband channel scanned within the selected carrier; and

indicating that narrowband channels having signal strengths exceeding the threshold include interference.

45. A method as defined in claim 44, further comprising filtering the multicarrier communication signal for at least one frequency corresponding to the narrowband channel having a signal strength exceeding the threshold.

46. A method as defined in claim 44, wherein determining the weighted sum comprises multiplying the signal strengths of the narrowband channels near the edge of the selected carrier by a first weight and multiplying the signal strengths of the narrowband channels not near the edge of the selected carrier by a second weight.

47. A method as defined in claim 46, wherein the first weight is higher than the second weight.

48. A method as defined in claim 46, wherein the first weight is equal to eight.

49. A method for detecting narrowband interference in a multicarrier communication signal including a plurality of carriers, wherein each carrier has a plurality of narrowband channels disposed therein, the method comprising:

scanning a number of narrowband channels associated with a selected carrier of the plurality of carriers to determine signal strengths for the number of scanned narrowband channels associated with the selected carrier;

identifying a number of narrowband channels having the largest signal strengths within a bandwidth of the selected carrier;

determining a weighted sum of the signal strengths of the number of narrowband channels associated with the selected carrier;

determining a threshold for the selected carrier by dividing the weighted sum by the difference between the number of narrowband channels associated with the selected carrier signal and the number of narrowband channels having the largest signal strength within a bandwidth of the selected carrier;

comparing to the threshold the signal strengths for the number of narrowband channel scanned within the selected carrier; and

indicating that narrowband channels having signal strengths exceeding the threshold include interference.

50. A method as defined in claim 49, further comprising filtering the multicarrier communication signal for at least one frequency corresponding to the narrowband channel having a signal strength exceeding the threshold.

51. A method as defined in claim 49, wherein determining the weighted sum comprises multiplying the signal strengths of the narrowband channels near the edge of the selected carrier by a first weight and multiplying the signal strengths of the narrowband channels not near the edge of the selected carrier by a second weight.

52. A method as defined in claim 51, wherein the first weight is higher than the second weight.

53. A method as defined in claim 51, wherein the first weight is equal to eight.