Cable detection apparatus and method

• US 20040189322A1
• Filed: 03/31/2003
• Published: 09/30/2004
• Est. Priority Date: 03/31/2003
• Status: Active Grant

• Current Assignee: Radiodetection Limited
• Original Assignee: Radiodetection Limited
• Inventors: King, James Ian, Pearson, Richard D.
• Granted Patent: US 6,977,508 B2
• Time in Patent Office: Days
• US Class Current: 324/542
• CPC Class Codes: G01V 15/00 Tags attached to, or associated with, an object, in order to enable detection of the object record carriers for use with machines having a detectable tag or marker G06K19/00
• CPC Class Codes: G01V 3/081 the magnetic field is produced by the objects or geological structures characterised by the method of magnetic field measurement G01R33/00

Abstract

A cable detection apparatus is disclosed having a filter, the filter transmitting components of a signal detected substantially at certain harmonics of a first frequency. The filter may also attenuate the signal at certain even harmonics thereof. A method of detecting and/or locating cables in the same manner is also disclosed.

Claims

1. A cable detection apparatus, comprising:

a detector to detect an electromagnetic field;

a filter system to receive signals from the detector and output a filtered signal, the filter system comprising a first filter having a higher transmittance at a plurality of harmonics of a first frequency than at least one non-harmonic frequency between two of said harmonics of the first frequency; and

an indicator to indicate the detection of a cable based on the filtered signal.

2. A cable detection apparatus according to claim 1, wherein the first filter has higher attenuation at least one even harmonic of the first frequency than at said plurality of harmonics.

3. A cable detection apparatus according to claim 1, further comprising a second filter arranged in series with the first filter having higher transmittance at least one harmonic of the first frequency than at least one non-harmonic frequency of the first frequency.

4. A cable detection apparatus according to claim 1, wherein the first frequency is the frequency of an alternating current carried by a cable to be detected.

5. A cable detection apparatus according to claim 3, further comprising at least one further filter arranged in series with the first filter, the further filter having higher transmittance at least one harmonic of the first frequency than at least one non-harmonic frequency of the first frequency.

6. A cable detection apparatus according to claim 3, further comprising at least one further filter arranged in series with the second filter, the further filter having higher transmittance at at least one odd harmonic of the first frequency than at at least one non-harmonic frequency, and higher attenuation at at least one even harmonic of the first frequency than at said plurality of harmonics.

7. A cable detection apparatus according to claim 3, wherein at least one of the first and second filters comprises a comb filter.

8. A cable detection apparatus according to claim 1, wherein the first filter has higher transmittance at the first frequency than at least one a non-harmonic frequency of the first frequency.

9. A cable detection apparatus, comprising:

a first filter having lower attenuation at a plurality of harmonics of a first frequency than at least one non-harmonic frequency between two of said harmonics of the first frequency, said at least one non-harmonic frequency having higher attenuation than at said plurality of harmonics;

a multiplier to multiply a filtered signal from the filter; and

an oscillator, the oscillator adapted to oscillate at a further predetermined frequency to drive the multiplier to output a frequency shifted signal, wherein frequencies of the filtered signal corresponding to at least one lower attenuation frequency of the filter are frequency shifted to coincide with at least one higher attenuation frequency of the filter.

10. A cable detection apparatus according to claim 9, wherein the filter system further has higher attenuation at at least one even harmonic of the first frequency than at said plurality of harmonics.

11. A cable detection apparatus according to claim 9, further comprising a speaker connected to the output of the multiplier to be driven by the multiplier output signal.

12. A cable detection apparatus according to claim 9, further comprising an emitter to emit electromagnetic radiation substantially at least one frequency corresponding to higher attenuation frequencies of the filter.

13. A cable detection apparatus according to claim 9, wherein the first frequency is the frequency of an alternating current carried by a cable to be detected.

14. A cable detection apparatus according to claim 9, further comprising a second filter arranged in series with the first filter, the second filter having lower attenuation at at least one harmonic of the first frequency than at at least one non-harmonic frequency of the first frequency.

15. A cable detection apparatus according to claim 14, further comprising a further filter arranged in series with the second filter, the further filter having lower attenuation at at least one odd harmonic of the first frequency than at at least one non-harmonic frequency of the first frequency, and higher attenuation at at least one even harmonic thereof than at said plurality of harmonics.

16. A cable detection apparatus according to claim 15, wherein at least one of the filters comprises a comb filter.

17. A method of noise reduction in a cable detection apparatus, the method comprising:

filtering a cable detection input signal to increase the relative strength of signal components at a plurality of harmonics of a first frequency to at least one non-harmonic frequency between two of said harmonics of the first frequency.

18. A method according to claim 17, the filtering further comprising reducing the relative strength of signal components at even harmonics of the first frequency to the strength at the plurality of harmonics of first frequency.

19. A method according to claim 17, further comprising frequency shifting the filtered signal to frequency shift the high relative strength frequencies of the filter to coincide with reduced relative strength frequencies of the filtered signal.

20. A method according to claim 19, further comprising outputting a sound signal corresponding to the frequency shifted signal.

21. A method according to claim 19, further comprising emitting electromagnetic radiation substantially at at least one frequency corresponding to reduced strength frequencies of the filtered signal.

22. A method according to claim 17, further comprising repeating at least one of the filtering steps.

23. A cable detection apparatus comprising:

detecting means for detecting an electromagnetic field;

first filter means for receiving signals from the detecting means, transmitting components of the signal substantially at a plurality of harmonics of a first frequency at a higher strength than components at at least one non-harmonic frequency between two of said harmonics of the first frequency, and outputting a filtered signal; and

indicating means for indicating the detection of a cable based on the filtered signal.

24. A cable detection apparatus according to claim 23, wherein the filter means is also for attenuating the signal at at least one even harmonic of the first frequency.

25. A cable detection apparatus according to claim 24, further comprising second filter means for transmitting components of a signal substantially at at least one harmonic of the first frequency and attenuating other frequencies.

26. A cable detection apparatus according to claim 24, wherein the first frequency is the frequency of an alternating current carried by a cable to be detected.

27. A cable detection apparatus according to claim 25, further comprising further filter means for transmitting components of the signal substantially at at least one harmonic of the first frequency at a higher strength than components at at least one non-harmonic frequency of the first frequency.

28. A cable detection apparatus according to claim 25, further comprising further filter means for transmitting components of the signal substantially at at least one odd harmonic of the first frequency and attenuating the signal at at least one even harmonic of the first frequency.

29. A cable detection apparatus according to claim 25, wherein at least one of the first and second filter means comprises a comb filter.

30. A cable detection apparatus according to claim 23, wherein the first filter means is for transmitting signal components at the first frequency at a higher strength than components at at least one a non-harmonic frequency of the first frequency.

31. A cable detection apparatus comprising:

filter means, the filter means comprising first filter means for transmitting components of the signal substantially at a plurality of harmonics of the first frequency and attenuating the signal at at least one non-harmonic frequency between two of said harmonics;

multiplying means for multiplying a filtered signal from the filter means; and

oscillator means for driving the multiplier and frequency shifting the high transmittance frequencies of the filter means to coincide with at least one high attenuation frequency of the filtered signal.

32. A cable detection apparatus according to claim 31, wherein the filter means further attenuates the signal substantially at least one even harmonic of the first frequency.

33. A cable detection apparatus according to claim 31, further comprising a sound output means for outputting a sound signal corresponding to the frequency shifted signal.

34. A cable detection apparatus according to claim 31, further comprising emitting means for emitting electromagnetic radiation substantially at at least one frequency corresponding to a high attenuation frequency of the first filter means.

35. A cable detection apparatus according to claim 31, wherein the first frequency is the frequency of an alternating current carried by a cable to be detected.

36. A cable detection apparatus according to claim 32, further comprising further filter means for transmitting components of the signal substantially at at least one harmonic of the first frequency and attenuating other frequencies.

37. A cable detection apparatus according to claim 32, further comprising further filter means for transmitting components of the signal substantially at at least one odd harmonic of the first frequency and attenuating the signal at at least one even harmonic of the first frequency.

38. A processing system for noise reduction in a cable detection apparatus, the processing system comprising:

a program memory storing instructions for controlling a processor; and

a processor for reading and implementing the instructions stored in the program memory;

wherein the program instructions stored in the program memory comprise instructions for controlling the processor to filter a cable detection input signal to increase the relative strength of signal components at a plurality of harmonics of a first frequency to at least one non-harmonic frequency between two of said of harmonics.

39. A processing system for noise reduction in a cable detection apparatus, the processing system comprising:

a program memory storing instructions for controlling a processor; and

a processor for reading and implementing the instructions stored in the program memory;

wherein the program instructions stored in the program memory comprise instructions for controlling the processor to filter a cable detection input signal to increase the relative strength of signal components at a plurality of odd harmonics of a first frequency to non-harmonic frequencies between two of said odd harmonics and to reduce the relative strength of signal components at at least one even harmonic of the first frequency to the strength at the plurality of odd harmonics.

40. A carrier medium carrying processor readable code for controlling a processor to filter a cable detection input signal to increase the relative strength of signal components at a plurality of harmonics of a first frequency to at least one non-harmonic frequency thereof between two of said harmonics.

41. A carrier medium carrying processor readable code for controlling a processor to filter a cable detection input signal to increase the relative strength of signal components at a plurality of odd harmonics of a first frequency to non-harmonics frequencies thereof between two of said odd harmonics and to reduce the relative strength of signal components at least one even harmonic of the first frequency to the strength at said plurality of odd harmonics.