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WO1997017767A1 - Suppression des perturbations diaphoniques dans des paires torsadees - Google Patents

Suppression des perturbations diaphoniques dans des paires torsadees Download PDF

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Publication number
WO1997017767A1
WO1997017767A1 PCT/CA1996/000734 CA9600734W WO9717767A1 WO 1997017767 A1 WO1997017767 A1 WO 1997017767A1 CA 9600734 W CA9600734 W CA 9600734W WO 9717767 A1 WO9717767 A1 WO 9717767A1
Authority
WO
WIPO (PCT)
Prior art keywords
signal
common mode
mode signal
differential amplifier
signals
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/CA1996/000734
Other languages
English (en)
Inventor
John Barsellotti
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
WEST END SYSTEMS CORP
Original Assignee
WEST END SYSTEMS CORP
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by WEST END SYSTEMS CORP filed Critical WEST END SYSTEMS CORP
Priority to EP96934284A priority Critical patent/EP0860056A1/fr
Priority to AU72751/96A priority patent/AU7275196A/en
Publication of WO1997017767A1 publication Critical patent/WO1997017767A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/30—Reducing interference caused by unbalanced currents in a normally balanced line
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/32—Reducing cross-talk, e.g. by compensating

Definitions

  • This invention relates to a method and apparatus for suppressing noise caused by foreign signals induced in transmission lines, such as twisted pair lines.
  • Cable companies with their higher bandwidth coaxial cables installed direct to the home are rushing to offer telephony and data communications and other services in competition with the telephone companies.
  • the telephone companies in turn wish to compete by offering switched entertainment and higher bandwidth data and video services.
  • the rejection of induced foreign signals (ingress) into unshielded twisted pair transmission lines depends on the pair balance. At frequencies at which twisted pair is normally used (typically ⁇ 20 kHz), this balance may be better than 60 dB. This means that the differential component ofthe common mode ingress will be attenuated by 60 dB. The common mode component is rejected at the receiver input while the differential component is admitted. Twisted pair balance becomes much worse at very high frequencies (up to 100
  • An object ofthe invention is to provide a method and circuit for suppressing noise under these conditions.
  • a method of suppressing noise in a transmission line comprising the steps of receiving incoming signals at the inputs of a differential amplifier, extracting a common mode signal from said input signals, integrating the output of said differential amplifier that is correlated with said common mode signal over a large number of cycles, and adjusting the balance in said line on the basis of said integration.
  • the integrated signal will be minimized over time to keep the line in optimum balance.
  • the differential component should be smaller than the common mode component (as it normally would be).
  • the differential component In the case ofthe wanted signal, the differential component must be greater than the common mode component (as it normally would be).
  • the unwanted signal can be extracted from the composite using correlation techniques.
  • the pair balance may then be adjusted, at the receiver input, until this unwanted signal is cancelled. If the pair balance is different at different frequencies then multiple cancellers may be used, each operating in a different band.
  • This canceller not only compensates for imperfect balance in the twisted pair, it also compensates for imperfect balance within the receiver.
  • the invention also provides a noise cancellation circuit characterized in that it comprises a differential amplifier for receiving incoming signals on a transmission line, means for a extracting a common mode signal from the incoming signals, means for integrating an output of said differential amplifier that is correlated with said common mode signals, and means for adjusting the signal balance in said transmission line on the basis of said integration.
  • FIG. 1 is a block diagram of an echo canceller circuit in accordance with the invention.
  • Figure 2 shows the result of simulating a circuit in accordance with Figure 1 ; and Figure 3 shows the first 15 micro-seconds of simulation where the composite signal can be seen to be dominated by the ingress:
  • Figure 4 shows the last 15 micro-seconds of simulation where only the wanted signal can be seen.
  • one component o a twisted pair line 1 is connected to the non-inverting input of a receiver amplifier 2 and the other component is connected to the inverting input through balance adjustment unit 1 1 for restoring line balance.
  • this can be a variable gain amplifier.
  • the line 1 is also connected to the two non-inverting inputs of common mode amplifier 3, which detects common mode signals (cm), and respective non-inverting and inverting inputs of amplifier 4, which produces a difference signal dif.
  • the common mode output signal from amplifier 3 is applied to the non- inverting inputs of comparators 5. 6.
  • the inverting input of comparator 5 is connected to ground.
  • the differential output of amplifier 4 is connected through full wave rectifier 7 to inverting input of comparator 6.
  • the outputs of comparator 5 and 6 are fed through AND gate 8 to control switch 9.
  • comparator 5 will turn on switch 9 via AND gate 8 when the signal cm is positive, i.e. during positive half-cycles of the waveform.
  • switch 9 connects the output of receiver 2 to the input of an integrator 10. Since the unwanted component ofthe difference signal is correlated with the common mode, this will be positive at the same time, whereas the uncorrelated wanted signal will be randomly positive and negative. Over a long period of time (typically tens of thousands times the signal period), the unwanted signal at the output of receiver 2 will therefore accumulate at the integrator output. The output of integrator 10 restores the twisted pair balance at the input of the receiver 2 through balance adjustment unit 1 1 thereby to suppress the noise.
  • amplifier 4 detects the differential signal dif.
  • Full wave rectifier 7 derives the absolute value of this signal, which is always positve.
  • the comparator 6 serves to stop integration from occurring at the integrator 10 while the absolute value of the signal dif is higher than the signal cm since the AND gate 8 causes switch 9 to open. The net result is that integration will only take place while the dif signal (and its cm component) is passing through zero. As a result these signals are ignored by the integrator.
  • the wanted signal is 4Vpp with a cm component of 0.8Vpp.
  • the cm ingress is 160Vpp with a dif component of 40Vpp.
  • the ingress signal is a composite of 967kHz, 1.57MHz and 1.93MHz. The first 0.015 seconds of convergence is simulated.
  • Figure 3 shows the first 15 micro-seconds of simulation where the composite signal can be seen to be dominated by the ingress.
  • Figure 4 shows the last 15 micro ⁇ seconds of simulation where only the wanted signal can be seen.
  • circuit has been described as an analog circuit, but those skilled in the art will recognize that it can also be implemented in the digital domain using digital signal processors. It may also be used with duplex systems adopting a ping-pong approach, where signals are alternately sent in opposite directions. It can be used with systems employing frequency or time division multiplexing.
  • the above circuit may destroy the wanted signal. For this reason, it may be desirable to include a noise detector and a device for de ⁇ activating the circuit when the noise drops below a certain threshold level.
  • the described circuit shows great promise in suppressing uncorrelated single frequency interference and impulse noise.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Noise Elimination (AREA)

Abstract

Procédé de suppression du bruit dans une ligne de transmission (1) consistant à extraire un signal de mode commun depuis des signaux d'arrivée. La sortie de l'amplificateur différentiel (2) mis en corrélation avec le signal de mode commun est intégrée (10) et l'équilibre du signal dans la ligne de transmission est réglé sur la base de l'intégration.
PCT/CA1996/000734 1995-11-07 1996-11-07 Suppression des perturbations diaphoniques dans des paires torsadees Ceased WO1997017767A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP96934284A EP0860056A1 (fr) 1995-11-07 1996-11-07 Suppression des perturbations diaphoniques dans des paires torsadees
AU72751/96A AU7275196A (en) 1995-11-07 1996-11-07 Cross talk interference cancellation in twisted pairs

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9522737.7A GB9522737D0 (en) 1995-11-07 1995-11-07 Noise cancellation in twisted pairs
GB9522737.7 1995-11-07

Publications (1)

Publication Number Publication Date
WO1997017767A1 true WO1997017767A1 (fr) 1997-05-15

Family

ID=10783475

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CA1996/000734 Ceased WO1997017767A1 (fr) 1995-11-07 1996-11-07 Suppression des perturbations diaphoniques dans des paires torsadees

Country Status (5)

Country Link
EP (1) EP0860056A1 (fr)
AU (1) AU7275196A (fr)
CA (1) CA2236852A1 (fr)
GB (1) GB9522737D0 (fr)
WO (1) WO1997017767A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999063675A1 (fr) * 1998-06-04 1999-12-09 Bell Canada Suppression de rfi et de bruit impulsif dans des canaux de transmission
US7933196B2 (en) * 2007-10-16 2011-04-26 Realtek Semiconductor Corp. Method and apparatus for canceling channel interference
GB2525458A (en) * 2014-03-31 2015-10-28 British Telecomm Communications network

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4527261A (en) * 1981-10-07 1985-07-02 Amf Incorporated Hiline interference eliminator
US4896120A (en) * 1986-03-24 1990-01-23 Zvi Kamil Instrumentation amplifier arrangement
US4910768A (en) * 1988-08-02 1990-03-20 The Inteleplex Corporation Automatic balancing circuit for longitudinal transmission system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4527261A (en) * 1981-10-07 1985-07-02 Amf Incorporated Hiline interference eliminator
US4896120A (en) * 1986-03-24 1990-01-23 Zvi Kamil Instrumentation amplifier arrangement
US4910768A (en) * 1988-08-02 1990-03-20 The Inteleplex Corporation Automatic balancing circuit for longitudinal transmission system

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999063675A1 (fr) * 1998-06-04 1999-12-09 Bell Canada Suppression de rfi et de bruit impulsif dans des canaux de transmission
US6546057B1 (en) 1998-06-04 2003-04-08 Bell Canada Suppression of radio frequency interference and impulse noise in communications channels
AU762950B2 (en) * 1998-06-04 2003-07-10 Bell Canada Suppression of RFI and impulse noise in communications channels
US7933196B2 (en) * 2007-10-16 2011-04-26 Realtek Semiconductor Corp. Method and apparatus for canceling channel interference
GB2525458A (en) * 2014-03-31 2015-10-28 British Telecomm Communications network

Also Published As

Publication number Publication date
AU7275196A (en) 1997-05-29
GB9522737D0 (en) 1996-01-10
EP0860056A1 (fr) 1998-08-26
CA2236852A1 (fr) 1997-05-15

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