Detection of bridge taps by frequency domain reflectometry-based signal processing with precursor signal conditioning

• US 6,744,854 B2
• Filed: 01/09/2002
• Issued: 06/01/2004
• Est. Priority Date: 12/09/1999
• Status: Expired due to Term

• Current Assignee: Fluke Corporation (Fortive Corp.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Berrier, Travis Lee, Wong, Wayne Kwok-Wai, Soto, Roy Lujan
• Primary Examiner(s): TRAN, QUOC DUC
• Application Number:
  US10/042,769
• Publication Number:
  US 20020090059A1
• Time in Patent Office: 874 Days
• Field of Search: 379/1.01, 379/1.03, 379/1.04, 379/14.01, 379/10.01, 379/10.02, 379/10.03, 379/15.05, 379/21, 379/22, 379/22.01, 379/22.02, 379/22.03, 379/27.07, 379/22.08, 379/24, 379/27.01, 379/27.02, 379/27.03, 379/27.04, 379/29.01
• US Class Current: 379/22.03
• CPC Class Codes: H04B 3/46 Monitoring; Testing
• CPC Class Codes: H04M 2203/057 distortion monitoring QoS monitoring H04M3/2227; quality of speech transmission monitoring H04M3/2236
• CPC Class Codes: H04M 3/08 Indicating faults in circuits or apparatus
• CPC Class Codes: H04M 3/26 with means for applying test signals or for measuring

Abstract

A frequency domain reflectometry-based bridged tap detection system for a telecommunication wireline employs a prescribed filtering operator, such as a ‘best-fit’ curve filter or a piecewise high pass filter bank, upstream of a Fourier processing operator, to improve the signal-to-noise ratio of the digitized amplitude array of the swept frequency band. To fit the response tones within the dynamic range of the analog-to-digital converter that digitizes the response tones detected from the wireline, a signal conditioning circuit, comprised of a comb filter bank, envelope detector and compander, is installed between the test head and the input to the analog-to-digital converter.

Claims

1. A method of automatically identifying the position of each of at least one energy reflection location along a wireline telecommunication link comprising the steps of:

(a) coupling a varying frequency waveform to a first location of said wireline telecommunication link;

(b) measuring a variation in signal level at said first location of said wireline telecommunication link in response to said varying frequency waveform;

(c) filtering said variation in signal level measured in step (b) to increase the signal-to-noise ratio of high frequency components of said measured variation in signal level; and

(d) performing frequency domain reflectometry processing of the filtered variation in signal level produced in step (c) to determine the distance between said first location and said position of said at least one energy reflection location along said wireline telecommunication link.

2. The method according to claim 1, wherein step (d) includes performing Fourier transform processing of said filtered variation in signal level produced in step (c).

3. The method according to claim 2, wherein said Fourier transform processing comprises Fourier transform processing said filtered variation in signal level in accordance with one of a Fast Fourier Transform and an inverse Fast Fourier Transform.

4. The method according to claim 1, wherein step (c) comprises filtering said variation in signal level measured in step (b) in accordance with a best fit curve-based precursor response filter whose amplitude vs. frequency profile is a best fit shape to the envelope of said variation in signal level.

5. The method according to claim 4, wherein said best fit curve-based precursor response filter comprises a least mean-squared error curve-based signal processing function.

6. The method according to claim 1, wherein step (c) comprises filtering said variation in signal level measured in step (b) in accordance with a plurality of high pass filters having respectively different transfer characteristics, and whose outputs are combined to obtain a composite filter characteristic that is effective to emphasize response components of said variation in signal level measured in step (b).

7. The method according to claim 1, wherein step (b) comprises conditioning said variation in signal level to produce a conditioned signal that accommodates digitizing parameters of an analog-to-digital converter, and digitizing said conditioned signal by means of said analog-to-digital converter.

8. The method according to claim 7, wherein step (b) comprises comb-filtering said variation in signal level, detecting the envelope produced by said comb-filtering, and companding said envelope, to produce said conditioned signal.

9. A frequency domain reflectometry-based bridged tap detection system for a telecommunication wireline comprising a precursor filter, installed upstream of a frequency domain reflectometry processor containing a Fast Fourier Transform operator, said precursor filter being configured to increase the signal-to-noise ratio of digitized amplitudes, produced by an analog-to-digital converter, of the response signal of said wireline as detected by a test head to the application to said wireline of a swept frequency band signal thereto, and further including a signal conditioning circuit, comprised of a comb filter bank, envelope detector and compander, installed between said test head and said analog-to-digital converter.

10. The frequency domain reflectometry-based bridged tap detection system according to claim 9, wherein said precursor filter comprises a plurality of high pass filters having respectively different transfer characteristics, and whose outputs are combined to obtain a composite filter characteristic that is effective to emphasize components of said response signal.

11. A system for automatically identifying energy reflection discontinuities along a wireline telecommunication link comprising a test signal generator that is operative to couple a varying frequency waveform to a measurement location of said wireline telecommunications link, in response to which said wireline propagates said varying frequency waveform to said energy reflection discontinuities, said energy reflection discontinuities reflecting energy back to said measurement location, a line monitoring receiver coupled to said measurement location of said wireline telecommunications link, a precursor filter that is operative to filter the response signal output of said line monitoring receiver, so as to increase the signal-to-noise ratio of high frequency components of said response signal output, and a response signal processor which is operative to execute a frequency domain reflectometry (FDR) algorithm to analyze the filtered response signal output of said precursor filter, and generate an output representative of locations of said energy reflection discontinuities.

12. The system according to claim 11, wherein said test signal generator is operative to generate a sinusoidal waveform that is varied between a minimum frequency and a maximum frequency.

13. The system according to claim 11, wherein said response processor is operative to execute a Fourier transform which decomposes the composite line signal response received by said line monitoring receiver and filtered by said precursor filter into frequency bins associated with frequency fluctuations of individual ones of said energy reflection discontinuities.

14. The system according to claim 13, wherein said Fourier transform comprises one of a Fast Fourier Transform and an inverse Fast Fourier Transform.

15. The system according to claim 12, wherein said precursor filter comprises a best fit curve-based precursor response filter whose amplitude vs. frequency profile is a best fit shape to the envelope of said response signal.

16. The system according to claim 15, wherein said best fit curve-based precursor response filter comprises a least mean-squared error curve-based signal processing function.

17. The system according to claim 12, wherein said precursor filter comprises a plurality of high pass filters having respectively different transfer characteristics, and whose outputs are combined to obtain a composite filter characteristic that is effective to emphasize components of said response signal.

18. The system according to claim 12, wherein said line monitoring receiver includes a digitizer that is operative to digitize the amplitude of the measured signal response of said line in association with the variation of the frequency of said sinusoidal waveform.

19. The system according to claim 18, wherein said line monitoring receiver includes a signal conditioning circuit that is configured to condition said line response signal, so as to produce a conditioned line response signal that accommodates digitizing parameters of said digitizer.

20. The system according to claim 19, wherein said signal conditioning circuit comprises a cascaded arrangement of a comb-filter, an envelope detector, and a compander.