Frequency domain reflectometry system for baselining and mapping of wires and cables

• US 6,937,944 B2
• Filed: 07/05/2002
• Issued: 08/30/2005
• Est. Priority Date: 07/07/2001
• Status: Expired due to Term

• Current Assignee: Kkb Technologies LLC
• Original Assignee: Cynthia M. Furse, Kenneth G. Blemel
• Inventors: Blemel, Kenneth G., Furse, Cynthia M.
• Primary Examiner(s): Hoff, Marc S.
• Assistant Examiner(s): O MALLEY, MARY CATHERINE
• Application Number:
  US10/190,311
• Publication Number:
  US 20040073395A1
• Time in Patent Office: 1,152 Days
• Field of Search: 702 57- 59, 702 65- 66, 702/71, 702 75- 77, 702/108, 702/117, 702/124, 702183-185, 702189-190, 324533-534, 324/539, 324/541, 324543-544, 439/912
• US Class Current: 702/58
• CPC Class Codes: G01R 27/04 in circuits having distributed constants , e.g. having very long conductors or involving high frequencies
• CPC Class Codes: G01R 31/008 on air- or spacecraft, railway rolling stock or sea-going vessels
• CPC Class Codes: G01R 31/11 using pulse reflection methods
• CPC Class Codes: G01R 31/58 Testing of lines, cables or conductors testing of electric windings G01R31/72

Abstract

A system that utilizes the principles of frequency domain reflectometry to perform baselining and mapping of single and mutliple wires and cables, the baselining to be used as a comparison when the wires are tested at a later date to determine if the wires or cables have been damaged, wherein a first waveform is generated from a baseline FDR measurement of a cable, a second waveform is generated from a new FDR measurement of the cable, and a comparison of the first and second waveforms is performed to determine if the integrity of the cable has changed, and wherein the mapping is performed in order to determine the present configuration of a network or tree of wires or cables.

Claims

1. A method for creating Baseline FDR measurements to be used for determining integrity of a cable under test utilizing a frequency domain reflectometry (FDR) cable testing system, said method comprising the steps of:

(1) coupling the FDR cable testing system to a connecting end of the cable under test, wherein it is assumed that the integrity of the cable under test is not compromised;

(2) generating signals from the FDR cable testing system in order to obtain a baseline FDR measurement for the cable under test, comprising the steps of;

(a) transmitting at least one input signal from the FDR cable testing system to the cable under test, and to a mixer;

(b) receiving a reflected input signal from the cable under test;

(c) mixing the at least one input signal and the reflected input signal in the mixer to thereby generate a DC signal; and

(3) storing the baseline FDR measurement for the cable under test.

2. The method as defined in claim 1 wherein the method further comprises the steps of:

(1) coupling the FDR cable testing system to the connecting end of the cable under test after obtaining the baseline FDR measurement for the cable under test;

(2) obtaining a new FDR measurement for the cable under test by generating signals from the FDR cable testing system;

(3) comparing the baseline FDR measurement against the new FDR measurement to thereby determine if there has been a detectable change in FDR measurements of the cable under test; and

(4) determining that the integrity of the cable under test may be compromised if there is a detectable change in FDR measurements, and determining that the integrity of the cable under test is not compromised if there is no detectable change in FDR measurements.

3. The method as defined in claim 2 wherein the step of storing the baseline measurement further comprises the step of storing the baseline measurement in a computer readable storage medium.

4. The method as defined in claim 3 wherein the steps of obtaining the baseline FDR measurement and the new FDR measurement further comprises the steps of:

(1) generating a first waveform representing the baseline FDR measurement; and

(2) generating a second waveform representing the new FDR measurement.

5. The method as defined in claim 3 wherein the step of comparing the baseline FDR measurement against the new FDR measurement further comprises the steps of:

(1) overlapping the first waveform representing the baseline FDR measurement over the second waveform representing the new FDR measurement; and

(2) making a visual comparison of the first waveform and the second waveform to determine if they appear identical.

6. The method as defined in claim 5 wherein the step of comparing the baseline FDR measurement against the new FDR measurement further comprises the step of performing a comparison of a first waveform representing the baseline FDR measurement against a second waveform representing the new FDR measurement by utilizing a computer algorithm to make the comparison.

7. The method as defined in claim 6 wherein the method further comprises the steps of:

(1) obtaining a plurality of baseline FDR measurements for a plurality of cables under test; and

(2) storing the plurality of baseline FDR measurements for the plurality of cables under test in a database, wherein each of the plurality of cables under test has associated therewith a corresponding one of the plurality of baseline FDR measurements.

8. The method as defined in claim 7 wherein the method further comprises the step of determining integrity of the cable under test only by making a comparison of the baseline FDR measurement and the new FDR measurement, and without having to interpret the baseline FDR measurement or the new FDR measurement.

9. The method as defined in claim 8 wherein the step of generating signals from the FDR cable testing system in order to obtain the baseline FDR measurement for the cable under test further comprises the steps of:

(1) transmitting at least one input signal from the FDR cable testing system to the cable under test;

(2) receiving a reflected input signal from the cable under test;

(3) mixing the at least one input signal and the reflected input signal to generate a DC signal; and

(4) processing the DC signal to thereby obtain data that is represented by the first waveform of the cable under test.

10. The method as defined in claim 9 wherein the step of generating signals from the FDR cable testing system in order to obtain the new FDR measurement for the cable under test further comprises the steps of:

(1) transmitting at least one input signal from the FDR cable testing system to the cable under test;

(2) receiving a reflected input signal from the cable under test;

(3) mixing the at least one input signal and the reflected input signal to generate a DC signal; and

(4) processing the DC signal to thereby obtain data that is represented by the second waveform of the cable under test.

11. The method as defined in claim 10 wherein the method further comprises the steps of:

(1) generating a sum of the at least one input signal and the reflected input signal;

(2) generating the difference of the at least one input signal and the reflected input signal; and

(3) generating the at least one input signal, wherein the three components form the mixed signal.

12. The method as defined in claim 11 wherein the method further comprises the step of filtering out high frequency components from the mixed signal.

13. The method as defined in claim 12 wherein the method further comprises the steps of:

(1) dropping the sum of the at least one input signal and the reflected input signal;

(2) dropping the at least one input signal; and

(3) converting the difference of the at least one input signal and the reflected input signal which is an analog direct current (DC) voltage signal to a digital signal.

14. The method as defined in claim 13 wherein the method further comprises the steps of:

(1) generating a plurality of input signals, wherein the plurality of input signals are utilized to generate a plurality of digital signals;

(2) storing the plurality of digital signals in an array, wherein a frequency of each of the plurality of input signals is associated with a corresponding digital signal that is generated thereby; and

(3) performing a Fast Fourier Transform (FFT) on each of the plurality of digital signals to thereby generate a plurality of Fourier signals, one for each of the plurality of digital signals, and wherein each of the plurality of Fourier signals has a given magnitude.

15. The method as defined in claim 14 wherein the step of transmitting the at least one input signal from the FDR cable testing system to the cable under test further comprises the steps of:

(1) providing a personal computer, wherein the personal computer generates a command signal containing a predetermined frequency for a sine wave; and

(2) providing a voltage controlled oscillator (VCO), wherein the VCO receives the command signal and generates the sine wave of the predetermined frequency value to thereby produce the input signal.

16. The method as defined in claim 15 wherein the method further comprises the steps of:

(1) providing a power divider, wherein the power divider splits the input signal;

(2) providing a mixer, wherein the mixer receives the input signal that is split by the power divider; and

(3) providing the cable under test, wherein the cable under test also receives the input signal that is split by the power divider.

17. The method as defined in claim 16 wherein the method further comprises the steps of:

(1) transmitting the reflected input signal from the point of termination of the cable under test to a directional coupler;

(2) transmitting the reflected input signal from the directional coupler to an amplifier; and

(3) amplifying the reflected input signal to thereby have a magnitude that is approximately the same as the input signal that was transmitted to the mixer.

18. The method as defined in claim 17 wherein the method further comprises the steps of:

(1) mixing the input signal received from the power divider and the reflected and amplified input signal received from the amplifier; and

(2) generating the mixed signal as defined in claim 11.

19. The method as defined in claim 18 wherein the method further comprises the steps of:

(1) filtering high frequency components from the mixed signal;

(2) digitizing the analog mixed signal; and

(3) transmitting the digitized signal to the personal computer for storage in the array of claim 14.

20. The method as defined in claim 19 wherein the method further comprises the steps of:

(1) generating the command signal that contains the first frequency for the VCO to generate;

(2) receiving the digital signal from the A/D converter;

(3) adding a stepped input frequency to a previous frequency transmitted to the VCO to generate a new frequency for the VCO to generate;

(4) transmitting the new frequency to the VCO in a new command signal; and

(5) repeating steps (2) through (4) until the new frequency is equal to or greater than a predetermined stop frequency.

21. The method as defined in claim 20 wherein the step of performing a transformation further comprises selecting the transformation from the group of transformations comprised of Discrete Fourier Transform, Two Equations—

Two Unknowns method, N-Equations N-Unknowns, Interpolation and FFT, Interspersing Zero Points and Low Pass Filtering, Acceleration of Data Signal, Zero Crossing of Signals, and Mathematical Modeling.

22. A cable testing system that utilizes principles of frequency domain reflectometry (FDR) to thereby determine characteristics of a cable under test (CUT) that can be used to determine changes in the CUT, said cable testing system comprising:

a voltage controlled oscillator (VCO) for generating an input signal;

a power divider for receiving the input signal from the VCO and dividing the input signal into at least two signals;

a mixer for receiving the divided input signal from the power divider;

wherein the CUT also receives the divided input signal from the power divider, and generates a reflected input signal, and wherein the mixer receives the divided input signal from the power divider and the reflected input signal from the CUT to thereby generate a mixed signal having at least two components;

an analog to digital (A/D) converter for receiving the mixed signal and filtering out high frequency components therefrom, and for generating a digital signal, wherein the digital signal contains a signal that is dependent upon a frequency of the input signal, a length of the CUT, and of a point of termination of the CUT; and

a processor for utilizing the digital signal to thereby generate a baseline FDR measurement if the CUT is being measured a first time, or to generate a new FDR measurement if the CUT is being tested against a previously obtained baseline FDR measurement.

23. The cable testing system as defined in claim 22 wherein the cable testing system further comprises a computer, wherein the computer controls the VCO and performs calculations to thereby determine the characteristics of the cable under test.

24. The cable testing system as defined in claim 23 wherein the cable testing system further comprises:

a directional coupler for receiving the reflected input signal from the CUT; and

an amplifier for receiving the reflected input signal from the directional coupler and amplifying the reflected input signal, wherein the amplifier transmits the reflected input signal to the mixer.

25. A method for determining characteristics of a cable under test utilizing a cable testing system that uses principles of frequency domain reflectometry (FDR), said method comprising the steps of:

(1) providing a signal generator for generating a sine wave, a power divider coupled to the signal generator at an input, and to a mixer and the cable under test at two outputs, wherein the mixer is also coupled at another input to the cable under test (CUT) for receiving a reflected sine wave therefrom, and at an output to an input of an analog to digital (A/D) converter, wherein the A/D converter is coupled at an output to a processor;

(2) transmitting a sine wave from the signal generator to the cable under test and to the mixer via the power divider;

(3) receiving a reflected sine wave from the cable under test at the mixer;

(4) mixing the sine wave and the reflected sine wave to generate a DC signal from the mixer;

(5) processing the DC signal to thereby obtain data regarding impedance and length of the cable under test;

(6) changing a frequency of the sine wave;

(7) performing steps (2) through (6) a predetermined number of times to thereby generated a plurality of DC signals; and

(8) generating a baseline FDR measurement if the CUT is being measured a first time, or generating a new FDR measurement if the CUT is being tested against a previously obtained baseline FDR measurement.

26. The method as defined in claim 25 wherein the method further comprises the step of mixing the sine wave and the reflected sine wave to thereby generate a mixed signal having at least two components.

27. The method as defined in claim 26 wherein the method further comprises the steps of:

(1) generating the sum of the sine wave and the reflected sine wave;

(2) generating the difference of the sine wave and the reflected sine wave; and

(3) generating the sine wave, wherein the sum, different and original sine wave for three components of the mixed signal.

28. The method as defined in claim 27 wherein the method further comprises the step of filtering out high frequency components from the mixed signal.

29. The method as defined in claim 28 wherein the method further comprises the steps of:

(1) dropping the sum of the sine wave and the reflected sine wave;

(2) dropping the at least one input signal; and

(3) converting the difference of the sine wave and the reflected sine wave, which is an analog direct current

(DC) voltage signal, to a digital signal, wherein a plurality of digital signals are generated by the plurality of sine waves.

30. The method as defined in claim 29 wherein the method further comprises the steps of:

(1) storing the plurality of digital signals in an array, wherein a frequency of each of the plurality of sine waves is associated with a corresponding digital signal that is generated thereby; and

(2) performing a Fast Fourier Transform (FFT) on each of the plurality of digital signals to thereby generate a plurality of Fourier signals, one for each of the plurality of digital signals, and wherein each of the plurality of Fourier signals has a given magnitude.

31. The method as defined in claim 30 wherein the method further comprises the steps of:

(1) providing a personal computer, wherein the personal computer generates a command signal containing a predetermined frequency for the sine wave; and

(2) providing a voltage controlled oscillator (VCO) as the signal generator, wherein the VCO receives the command signal and generates the sine wave of the predetermined frequency value.

32. The method as defined in claim 31 wherein the method further comprises the step of utilizing the personal computer to analyze the array after no more sine waves are being generated in order to compare the baseline FDR measurement and the new FDR measurement to thereby determine if there has been a change in integrity of the CUT.