Detecting and measuring interference contained within a digital carrier

• US 7,639,761 B2
• Filed: 02/26/2003
• Issued: 12/29/2009
• Est. Priority Date: 03/04/2002
• Status: Active Grant

• Current Assignee: Glowlink Communications Technology, Inc. (Singapore Technologies Engineering Limited)
• Original Assignee: Glowlink Communications Technology, Inc. (Singapore Technologies Engineering Limited)
• Inventors: Downey, Michael L., Chu, Jeffrey C.
• Primary Examiner(s): Bocure; Tesfaldet
• Assistant Examiner(s): Panwalkar; Vineeta S
• Application Number:
  US10/375,221
• Publication Number:
  US 20030165205A1
• Time in Patent Office: 2,498 Days
• Field of Search: 375/346, 375/316, 375/229, 375/230, 375/232, 375/233, 375/148, 375/147, 375/144, 375/141, 375/140, 333/18, 333/28.R, 708/323, 329/318, 329/319, 329/320, 329/349, 329/63.1, 329/296, 455/63.1, 455/296
• US Class Current: 375/346
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04B 17/345 Interference values signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR] H04B17/336
• CPC Class Codes: H04L 1/20 using signal quality detector

Abstract

A method and system for measuring noise and or interference in a communications signal without taking the signal out of service. In the present invention the communications signal is converted from an RF signal into an IF signal. The IF signal is then digitized and stored. The stored signal is processed to determine the interference signal. The interference signal is calculated from an error vector produced by a blind equalizer demodulator. The interference signal is extracted and presented to a user.

Claims

1. A method of detecting in-band interference in a carrier signal in a communication system comprising the steps of:

acquiring a digital signal comprising the carrier signal and an in-band interference signal having a source that is independent from that of the carrier signal, said acquiring including receiving the signal at a receiver, filtering the signal and digitizing the signal;

formatting the digital signal including filtering the digital signal, and performing decimation and re-sampling of the digitized signal; and

extracting the interference signal without interrupting the carrier signal by performing blind equalization and demodulation using a blind equalizer demodulator thereby forming an error vector that is representative of the in-band interference signal.

2. The method according to claim 1, wherein the step of formatting the digital signal is performed without knowledge of the carriers RF or modulation parameters.

3. The method according to claim 1, wherein the step of formatting the digital signal is performed with knowledge of the carriers RF or modulation parameters.

4. The method according to claim 1, further comprising extracting noise from the digital signal.

5. The method according to claim 1, wherein the communication system performs as a wireless communication system.

6. The method according to claim 1, wherein the communication system performs as a satellite communication system.

7. The method according to claim 1, wherein the carrier comprises an RF signal.

8. The method according to claim 1, wherein acquiring the digital signal includes converting the carrier signal into an IF signal, wherein the IF signal is representative of the carrier signal.

9. The method according to claim 1, wherein filtering the digital signal includes filtering the carrier signal to limit the bandwidth to a signal of interest.

10. The method according to claim 1, wherein acquiring a digital signal includes storing a digitized filtered signal into memory.

11. The method according to claim 1, wherein formatting the digital signal includes calculating a center frequency and a bandwidth of the carrier signal.

12. The method according to claim 1, wherein filtering the digital signal includes down-converting the digital signal to the baseband of the carrier signal.

13. The method according to claim 1, wherein the re-sampling of the digital signal occurs at twice the frequency of interest.

14. The method according to claim 1, including removing M initial samples of the error vector, wherein the M initial samples occur while the blind equalization and demodulation is still converging.

15. The method according to claim 1, including removing a DC bias from the error vector.

17. The system according to claim 13, wherein the signal processor is without knowledge of the carriers RF or modulation parameters.

32. The method according to claim 1, further comprising processing the error vector to obtain one or more spectral properties of the interference signal.

33. The method according to claim 32, wherein the spectral properties are selected from a group consisting of a power spectrum of the interference signal and a detected energy of the interference signal.

34. The method according to claim 32, wherein the spectral properties are selected from a group consisting of a center frequency of the interference signal and a bandwidth of the interfering signal.

35. The method according to claim 32, further comprising displaying the one or more spectral properties.

16. A system for detecting in-band interference in a carrier signal in a communication system comprising:

a receiver for acquiring a digital signal, the digital signal including a carrier signal and an in-band interference signal having a source that is independent from that of the carrier signal, a signal processor for conditioning the digital signal and a blind equalizer demodulator for extracting the in-band interference signal without interrupting the carrier signal by forming an error vector that is representative of the in-band interference signal included in the digital signal and wherein the signal processor is further configured to process the interference signal to obtain one or more spectral properties of the interference signal.

18. The system according to claim 16, wherein the signal processor knows of the carriers RF or modulation parameters.

19. The system according to claim 16, wherein the digital signal further comprises noise.

20. The system according to claim 16, wherein the communication system performs as a wireless communication system.

21. The system according to claim 16, wherein the communication system performs as a satellite communication system.

22. The system according to claim 16, wherein the carrier comprises an RF signal.

23. The system according to claim 16, wherein the receiver is further configured to convert the carrier signal into an IF signal, wherein the IF signal is representative of the carrier signal.

24. The system according to claim 16, wherein the receiver is further configured to filter the carrier signal to limit the bandwidth to a signal of interest.

25. The system according to claim 16, wherein the receiver is further configured to stores a digitized filtered signal in memory.

26. The system according to claim 16, wherein the signal processor is further configured to calculates a center frequency and a bandwidth of the carrier signal.

27. The system according to claim 16, wherein the signal processor is further configured to down convert the digital signal to the baseband of the carrier signal.

28. The system according to claim 16, wherein the signal processor is further configured to decimate the digital signal at twice the symbol rate.

29. The system according to claim 16, wherein the signal processor is further configured to remove M initial samples of the error vector, wherein the M initial samples occur while the blind equalization and demodulation is still converging.

30. The system according to claim 16, wherein the signal processor is further configured to remove a DC bias from the error vector.

31. The system according to claim 16, wherein the receiver is further configured to receive the signal, filter the signal and digitize the filtered signal.

36. The system according to claim 16, wherein the spectral properties are selected from a group consisting of a power spectrum of the interference signal and a detected energy of the interference signal.

37. The system according to claim 16, wherein the spectral properties are selected from a group consisting of a center frequency of the interference signal and a bandwidth of the interference signal.

38. The system according to claim 16, further comprising a display that displays the one or more spectral properties.