EP1020875A2 - EMI - Filtrieren bei Mehrdrahtkabeln - Google Patents

EMI - Filtrieren bei Mehrdrahtkabeln Download PDF

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Publication number
EP1020875A2
EP1020875A2 EP99123557A EP99123557A EP1020875A2 EP 1020875 A2 EP1020875 A2 EP 1020875A2 EP 99123557 A EP99123557 A EP 99123557A EP 99123557 A EP99123557 A EP 99123557A EP 1020875 A2 EP1020875 A2 EP 1020875A2
Authority
EP
European Patent Office
Prior art keywords
cable
emi
length
noise signals
distributed
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.)
Withdrawn
Application number
EP99123557A
Other languages
English (en)
French (fr)
Other versions
EP1020875A3 (de
Inventor
Roger Neil Barker
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.)
Alcatel CIT SA
Alcatel Lucent SAS
Original Assignee
Alcatel CIT SA
Alcatel SA
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 Alcatel CIT SA, Alcatel SA filed Critical Alcatel CIT SA
Publication of EP1020875A2 publication Critical patent/EP1020875A2/de
Publication of EP1020875A3 publication Critical patent/EP1020875A3/de
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B11/00—Communication cables or conductors
    • H01B11/02—Cables with twisted pairs or quads
    • H01B11/06—Cables with twisted pairs or quads with means for reducing effects of electromagnetic or electrostatic disturbances, e.g. screens

Definitions

  • This invention relates to an arrangement for ameliorating the effects of electromagnetic interference (EMI), such as that generated by noisy equipment.
  • EMI electromagnetic interference
  • the invention is particularly applicable to multi-wire cables emerging from otherwise EMI sealed equipment housings. In such instances, EMI can escape from the housing and radiate from the cables or be fed into other equipment via the cables.
  • a known solution to this problem is to use a plurality of filters, one for each line, to prevent the EMI emerging form the housing.
  • low pass filters may be used.
  • This specification therefore discloses a method of reducing above band noise signals on a multi-wire cable, the method including applying a distributed EMI coupling means over at least part of the length of the cable, the length of the coupling means being sufficient to attenuate the noise signals below a pre-determined threshold.
  • the specification also discloses an arrangement for filtering above-band noise signals from a multi-wire cable, the arrangement including an earthed distributed EM coupling means distributed over at least a part of the length of the cable, the length of the coupling means being such that the coupling of the above-band noise signals to the distributed coupling is sufficient to attenuate the noise signals to below a predetermined threshold over the length of the distributed impedance.
  • Figure 1 shows first and second equipment housings interconnected by a cable, according to an embodiment of the invention.
  • Figure 2 is a graph representing noise attenuation against cable length.
  • Figure 1 represents a multiplexer 1, connected to a PABX 10 via a length of multi-pair cable containing over 100 pairs.
  • the multiplexer generates noise at frequencies above 30MHz.
  • the multiplexer is co-located with the PABX and the length of the cable would ordinarily be of the order of 5 to 10 meters.
  • the multiplexer 1 is shown schematically as containing signal processing equipment 2, and the noise generating source 3 which impose signals and EMI respectively on a multi pair cable 4.
  • the EMI is generated incidentally to the signal processing, e.g. in sampling the signals.
  • the housing of the multiplexer 1 is sealed against EMI, but the cable 4 exits via an aperture in the housing enabling EMI to escape from the housing 1 on the cable lines 6.
  • shielding 7 which forms an EMI seal with the housing of multiplexer 1.
  • the shielding 7 prevents the EMI on the lines 6 from radiating.
  • the PABX 10 feeds a plurality of telephone subsets, 20.... 30, which are connected to the PABX by unshielded telephone lines.
  • the noise will be radiated by the telephone lines.
  • the noise signal can be attenuated to a predetermined level, e.g. to a level set by standards for permissible noise at the frequency of interest.
  • Figure 2 illustrates the reduction in noise signal in relation to the length of shielded cable. As shown, a particular noise threshold can be achieved by providing a sufficient length of shielding.
  • Our invention takes advantage of this characteristic by providing an additional length of cable, shown schematically as loop 8, to ensure the EMI is sufficiently attenuated.
  • the housing of the multiplexer 1 and the shielding 7 effectively form a Faraday cage which prevents the escape of the target EMI frequencies.
  • the remote and of shielding 7 is grounded to the same potential as the housing 1.
  • the shielding acts as a distributed capacitance to which the EMI is coupled and attenuates the EMI.
  • the invention has the advantage that otherwise non-EMI compliant equipment can be made EMI compliant. This eases the design requirements for the internal circuits which do not need to implement specific EMI techniques. Equipment design is therefore more flexible because the hardware design criteria is less stringent.
  • a sufficient length of conductive braid or metal tape may be applied to shield unshielded cables to a length sufficient to attenuate the EMI, and, where necessary, an EMI sealed housing applied around the equipment if the existing housing is not EMI sealed.
  • the newly applied shielding is connected electrically to the EMI sealed housing to form a Faraday cage.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Communication Cables (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
  • Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
EP99123557A 1999-01-14 1999-11-26 EMI - Filtrieren bei Mehrdrahtkabeln Withdrawn EP1020875A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AUPP814899 1999-01-14
AUPP8148A AUPP814899A0 (en) 1999-01-14 1999-01-14 Emi filtering of multi-wire cables

Publications (2)

Publication Number Publication Date
EP1020875A2 true EP1020875A2 (de) 2000-07-19
EP1020875A3 EP1020875A3 (de) 2001-04-18

Family

ID=3812353

Family Applications (1)

Application Number Title Priority Date Filing Date
EP99123557A Withdrawn EP1020875A3 (de) 1999-01-14 1999-11-26 EMI - Filtrieren bei Mehrdrahtkabeln

Country Status (3)

Country Link
EP (1) EP1020875A3 (de)
JP (1) JP2000232396A (de)
AU (1) AUPP814899A0 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7138896B2 (en) 2004-06-29 2006-11-21 International Business Machines Corporation Ferrite core, and flexible assembly of ferrite cores for suppressing electromagnetic interference
RU2609151C2 (ru) * 2015-06-30 2017-01-30 Федеральное Государственное Унитарное Предприятие Ордена Трудового Красного Знамени Научно-Исследовательский Институт Радио (Фгуп Ниир) Способ снижения уровня напряжений, наводимых на согласованных нагрузках коаксиального кабеля узкополосной радиочастотной помехой

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5209964A (en) * 1990-11-20 1993-05-11 Kitagawa Industries Co., Ltd. Conductive sheet for shielding electromagnetic waves
EP0584658A2 (de) * 1992-08-22 1994-03-02 Alcatel SEL Aktiengesellschaft Verteiler für EMV abgeschirmte Schränke
EP0597324A1 (de) * 1992-11-02 1994-05-18 Sumitomo Wiring Systems, Ltd. Kabelbaum
DE19909569A1 (de) * 1998-03-06 1999-09-16 Murata Manufacturing Co Zusammengesetzes Magnetband zur Sperrung von Strahlungsrauschen und Komponente zur Sperrung von Strahlungsrauschen

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5209964A (en) * 1990-11-20 1993-05-11 Kitagawa Industries Co., Ltd. Conductive sheet for shielding electromagnetic waves
EP0584658A2 (de) * 1992-08-22 1994-03-02 Alcatel SEL Aktiengesellschaft Verteiler für EMV abgeschirmte Schränke
EP0597324A1 (de) * 1992-11-02 1994-05-18 Sumitomo Wiring Systems, Ltd. Kabelbaum
DE19909569A1 (de) * 1998-03-06 1999-09-16 Murata Manufacturing Co Zusammengesetzes Magnetband zur Sperrung von Strahlungsrauschen und Komponente zur Sperrung von Strahlungsrauschen

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7138896B2 (en) 2004-06-29 2006-11-21 International Business Machines Corporation Ferrite core, and flexible assembly of ferrite cores for suppressing electromagnetic interference
US7489224B2 (en) 2004-06-29 2009-02-10 International Business Machines Corporation Ferrite core, and flexible assembly of ferrite cores for suppressing electromagnetic interference
RU2609151C2 (ru) * 2015-06-30 2017-01-30 Федеральное Государственное Унитарное Предприятие Ордена Трудового Красного Знамени Научно-Исследовательский Институт Радио (Фгуп Ниир) Способ снижения уровня напряжений, наводимых на согласованных нагрузках коаксиального кабеля узкополосной радиочастотной помехой

Also Published As

Publication number Publication date
JP2000232396A (ja) 2000-08-22
EP1020875A3 (de) 2001-04-18
AUPP814899A0 (en) 1999-02-04

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