US2152706A - Shielding for electrical circuits - Google Patents

Shielding for electrical circuits Download PDF

Info

Publication number
US2152706A
US2152706A US122339A US12233937A US2152706A US 2152706 A US2152706 A US 2152706A US 122339 A US122339 A US 122339A US 12233937 A US12233937 A US 12233937A US 2152706 A US2152706 A US 2152706A
Authority
US
United States
Prior art keywords
shielding
strands
iron
copper
thickness
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.)
Expired - Lifetime
Application number
US122339A
Other languages
English (en)
Inventor
Wilbur E Mougey
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.)
AT&T Corp
Original Assignee
Bell Telephone Laboratories Inc
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
Priority to BE425981D priority Critical patent/BE425981A/xx
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US122339A priority patent/US2152706A/en
Priority to FR832641D priority patent/FR832641A/fr
Application granted granted Critical
Publication of US2152706A publication Critical patent/US2152706A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

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
    • H01B11/08—Screens specially adapted for reducing cross-talk

Definitions

  • This invention relates to shielding of electric circuits and particularly to shielding of circuits for transmission of high frequency signals such as telephone voice currents or higher frequency carrier currents.
  • the invention is particularly related to the shielding, of conductor units, such as pairs or quads, as they appear in multiconductor cables, and the shielding may be used to reduce mutual interference between such circuits or for protection of such circuits against interference from external sources.
  • Nyquist in his patents referred to above, laid down a criterion according to which a high degree of shielding could be obtained by a composite shield made up of a layer or" highly conducting metal such as copper and a layer oi high permeability metal such as iron, contiguous thereto, such layers to be repeated in alternations as high- 5 er degrees of shielding are desired.
  • the shielding required between mutually disturbing circuits is planned in such a way that duplication of shielding layers is reduced to a minimum thereby reducing the size and weight of the cable, and also its cost.
  • the two shields enclosing two mutually disturbing circuits are, in accordance with the invention, designedso that by their combined shielding eii'ects the disturbing field from one circuit is reduced to the desired degree at a point within the shield of the other circuit in stead of at a point on the outside of the shield of the first circuit, as in the prior art referred to.
  • FIG. 1 shows a theoretical shielding arrangement between two disturbing circuits for given requirements
  • Fig. 2 shows schematically how the shielding required in accordance with Fig. 1 may be placed to surround the two circuits
  • Fig. 3 shows a similardistribution of shields between two circuits where a higher degree of shielding is required
  • Fig. 4 shows a cross-section of two quads shielded in accordance with Fig. 2;
  • Fig. 5 shows a side elevation'of one of the quads in Fig. i in the state of application of the various shielding layers;
  • Fig. 6 shows schematically a cross-section of a multl-conductor cable with mutually shielded conductor groups and supplementary shielding of the entire'cable against external disturbances
  • Fig. '7 shows a set of curves, similar to those disclosed by Harris, for illustrating the behavior 01' copper and iron under different shielding conditions.
  • critical thickness as applied to a copper layer and the term characteristic thickness as applied to a magnetic layer, and as used in the appended claims, are intended to have the same meaning as that given to them by Harris in his Patent 1,933,261.
  • the critical thickness of copper will be different for different types of shields and will vary with the dimensions of the shield; but in general the critical thickness of a copper shield falls below a range at which its effectiveness per unit of thickness shows a marked decline as the thickness of thelayer increases.
  • characteristic thickness of the iron this also varies somewhat with the dimensions of the shield but in general it is approximately the minimum thickness of iron shield which must be inter posed between two copper layers to insure substantially the same shielding efl'ect of each copper layer as it would have if used alone.
  • the source A may be a group of conductors in a cable and the source B may be another similar group of conductors in the same cable, both subject to disturbance.
  • the source A may be a group of conductors in a cable and the source B may be another similar group of conductors in the same cable, both subject to disturbance.
  • a shield is required between th s which consists of two copper l" the critical thickness
  • IliOIl 01f tht ciiamcte efiect cbtaiilct shields is the in Fig. .1.
  • each iron layer Fe may be increased to its characteristic thickness and a copper layer of critical thickness interposed therebetween, for example, by applying a copper layer of half the critical thickness to each shield.
  • the shielding may be still further increased by applying two intermediate copper layers or sheaths, each of critical thickness and separated by a third iron layer at least of characteristic thickness in order that the full shielding effect of the copper layers may be secured.
  • the shielding may, in accordance with the invention, be divided into two halves by again dividing the central iron layer into two halves and placing an equal number of copper and iron layers about the two strands A and B as shown in Fig. 3. It is evident that the principles of the invention may be similarly applied to still more complex shields.
  • the copper layer may be formed of a copper ribbon app ied helically about the strand to form a continuous sheath; in this case-the length of layer and amount oi overlap would be such as to permit the usual bending of the cable.
  • the invention thus is particularly of advantage when applied to cables with at least three conductor units or circuits.
  • the shield on any one circuit will constitute a part of each of the several shieldings required between that circuit and all the others and is supplemented by the similar shields on the others tocomplete the several mutual shieldings.
  • shields may similarly be supplemented by a common shield against an external source of disturbance when necessary.
  • the copper layers should be of not more than the critical thickness and should in all cases be separated by iron layers of at least the characteristic thickness.
  • Each layer of copper or of iron may be divided into sub-layers or sheaths, as when made up of a plurality of wrappings of tape, and at the point of subdivision of the shielding the sub-layers of copper or iron, as the case may be, may be placed about two adjacent circuits.
  • Fig. 6 shows diagrammatically a cross-section of a multiconductor cable comprising seven strands of signaling conductors A, B, C, D, E, F and G, all enclosed within a lead sheath L.
  • Each of the strands or units of conductors is enclosed within a half-shield in accordance with the arrangement in Fig. 2 comprising an inner copper layer'Cu of not more than critical thickness and an outer iron layer Fe of at least half the characteristic thickness. If the individual half shields do not provide sufilcient protection against disturbances from sources external of the cable, all the individually shielded strands may furthermore be enclosed within a common shield S which may supplement the individual shields by having an outer copper layer Cu of critical thickness and an inner layer Fe of at least half the characteristic thickness thereby insuring the most eflicient use of the copper.
  • the strands of conductors are uniformly shielded, which is an advantage in the manufacture of the cable, and a complete shield is established between any two strands of conductors for a given desired shielding effect.
  • the individual half-shields-on all thestrands furthermore supplement the common shield S to eifectively reduce disturbing effects from a source outside the cable upon the circuits of the individual strands.
  • the cable shown in Fig. 6 is one of several designs to which the invention may be applied.
  • the strands of conductors may be pairs or quads or may each contain a larger number of conductors.
  • the conductors within the strand may be insulated from each other in any known manner, such as by wrapped paper strips or by spaced discs of insulating material.
  • the couplings between the strands A, B, C, D, E and F may be difierent from the coupling be-
  • the individual tween thesestrands and the strand G, for which purpose the strand G may have a shield differing from those of the other strands, for example, by having a heavier magnetic layer Fe.
  • the shielding effect of the lead sheath L may, of course, be taken into account.
  • the common shield S may also have an additional copper layer on the outside of that shown in Fig. 6 and separated therefrom by another iron layer.
  • shieldingefiect -need not be in metallic contact for the purposes of the invention but may be separated by coatings or by braidings or bindings without a departure from the invention.
  • Two adjacent strands of high frequency signaling conductors, continuous shielding means for said strands comprising a plurality of layers alternately of highly conducting, substantially non-magnetic material such as copper or aluminum or not more than critical thickness and of high permeability magnetic material, such as iron, at least of characteristic thickness characterized in this, that said plurality of layers is divided into two shield structures, one of which is placed directly about one of said strands to form a unitary structure therewith and the other of which entirely encloses the other of said strands.
  • continuous shielding means for said strands comprising a composite shield placed close about one of said strands to form a unitary structure therewith and having an inner copper sheath of not more than critical thickness and an outer iron sheath, and a composite shield placed close about the other of said strands to form a unitary structure therewith and having an inner copper sheath of not more than critical thickness and an outer iron sheath, said iron sheaths being adjacent and their combined thickness being at least equal to the characteristic thickness.
  • said shielding means further comprises a composite shield common to both of said strands and having a copper sheath of not more than critical thickness and an iron sheath adjacent to said outer iron sheaths, the combined thickness of said last iron sheath and either of said outer iron sheaths being at least equal to the characteristic thickness.
  • shielding means for reducing mutual electrical disturbing eflfects between said strands, said shielding means comprising two sheaths, each of not more than the critical thickness of a highly conducting, substantially non-magnetic material such as copper or aluminum, said sheaths being separated by sheathing of magnetic material such as iron, of at least the characteristic thickness, one 01' said non-magnetic sheaths being placed to entirely surround one of said strands and exclude the other and the other of said non-magnetic sheaths being placed to entirely surround the other strand and exclude the said first strand.
  • two strands of conductors and continuous shielding means between said strands comprising a plurality of metallic layers alternately of copper and iron formed into two shields each enclosing one strand to the exclusion of the other respectively, said shields each having an inner layer of copper oi not more than critical thickness, and an outer layer of iron of at least half the characteristic thickness.
  • continuous shielding means placed close about one of said strands to form a unitary structure therewith and comprising an inner layer of copper and an outer layer of iron, other continuous shielding means entirely surrounding the other of said strands and comprising a layer of copper and contiguous thereto a layer of iron immediately adjacent to the first said layer of iron throughout their common length, the total thickness of said two layers of iron being at least equal to the characteristic thickness of the iron.
  • continuous shielding means for said strands comprising a composite shield placed close about one of said strands to forma unitary structure therewith and having a thin inner copper sheath and an outer iron sheath, and a composite shield placed close about the other of said strands to form a unitary structure therewith and having a thin inner copper sheath and an outer iron sheath, said iron sheaths being adjacent and their combined thickness being about equal to the characteristic thickness of the iron.
  • two strands of conductors and continuous shielding means between said strands comprising a plurality of thin metallic layers alternately of copper and iron formed into two shields each enclosing one strand to the exclusion of the other respectively, said shields each having an inner layer 0! copper and an outer layer of iron 0! about half the characteristic thickness.
  • Two adjacent strands 01' high frequency signaling conductors, continuous shielding means for said strands comprising a plurality oi layers alternately oi highly conducting, substantially non-magnetic material, such as copper or alumi mum, of not more than critical thickness as ne tel-mined at frequencies or the order oi! 45mm cycles per second, and oi high permeabili magnetic niatcriai, such as iron at lea oi teristic thickness characterized in till 1 t
  • Wei plurality oi layers is divided into i shield structures, one of which is placed directly about one of said strands to form a unitary structure therewith and the other of which entirely em closes the other of said strands.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Insulated Conductors (AREA)
  • Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
US122339A 1937-01-26 1937-01-26 Shielding for electrical circuits Expired - Lifetime US2152706A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
BE425981D BE425981A (enrdf_load_stackoverflow) 1937-01-26
US122339A US2152706A (en) 1937-01-26 1937-01-26 Shielding for electrical circuits
FR832641D FR832641A (fr) 1937-01-26 1938-01-25 écrans pour circuits électriques

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US122339A US2152706A (en) 1937-01-26 1937-01-26 Shielding for electrical circuits

Publications (1)

Publication Number Publication Date
US2152706A true US2152706A (en) 1939-04-04

Family

ID=22402135

Family Applications (1)

Application Number Title Priority Date Filing Date
US122339A Expired - Lifetime US2152706A (en) 1937-01-26 1937-01-26 Shielding for electrical circuits

Country Status (3)

Country Link
US (1) US2152706A (enrdf_load_stackoverflow)
BE (1) BE425981A (enrdf_load_stackoverflow)
FR (1) FR832641A (enrdf_load_stackoverflow)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2526942A (en) * 1946-04-15 1950-10-24 Telecommunications Sa Process for reducing the far-end crosstalk between concentric pairs due to tertiary circuits
US4510346A (en) * 1983-09-30 1985-04-09 At&T Bell Laboratories Shielded cable
FR2665809A1 (fr) * 1990-08-10 1992-02-14 Schnitzler Charles Dispositif d'amelioration de la qualite de signaux electriques, electro-acoustiques et/ou video.
EP1761935A4 (en) * 2004-06-30 2008-08-20 Hitachi Cable DIFFERENTIAL SIGNAL TRANSMISSION CABLE
US20150310960A1 (en) * 2014-04-24 2015-10-29 Essex Group, Inc. Continously Transposed Conductor
US20170103830A1 (en) * 2014-04-25 2017-04-13 Leoni Kabel Gmbh Data cable

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3636234A (en) * 1969-12-04 1972-01-18 United States Steel Corp Communication cable

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2526942A (en) * 1946-04-15 1950-10-24 Telecommunications Sa Process for reducing the far-end crosstalk between concentric pairs due to tertiary circuits
US4510346A (en) * 1983-09-30 1985-04-09 At&T Bell Laboratories Shielded cable
FR2665809A1 (fr) * 1990-08-10 1992-02-14 Schnitzler Charles Dispositif d'amelioration de la qualite de signaux electriques, electro-acoustiques et/ou video.
EP1761935A4 (en) * 2004-06-30 2008-08-20 Hitachi Cable DIFFERENTIAL SIGNAL TRANSMISSION CABLE
US20150310960A1 (en) * 2014-04-24 2015-10-29 Essex Group, Inc. Continously Transposed Conductor
US9773583B2 (en) * 2014-04-24 2017-09-26 Essex Group, Inc. Continously transposed conductor
US20170103830A1 (en) * 2014-04-25 2017-04-13 Leoni Kabel Gmbh Data cable
US10438724B2 (en) * 2014-04-25 2019-10-08 Leoni Kabel Gmbh Data cable

Also Published As

Publication number Publication date
BE425981A (enrdf_load_stackoverflow)
FR832641A (fr) 1938-09-29

Similar Documents

Publication Publication Date Title
US2325549A (en) Ignition cable
US1606165A (en) Electrical conductor
US2125869A (en) Electrical conductor
KR101976338B1 (ko) 복합 케이블
US2109334A (en) Communication cable comprising one or more screened core groups
US2386753A (en) Insulated electrical conductor and cable
US2319744A (en) Shielding for communication circuits
US2152706A (en) Shielding for electrical circuits
US3163836A (en) Coaxial conductor having parallel connected stranded layers of different pitch for equalizing inductance and current distribution
US2663752A (en) Shielded electrical conductor with grounding strand
US2212927A (en) Lead covered multiconductor electric telephone cable
US2034033A (en) Shielded stranded pair
US2066525A (en) Conductor
US2792442A (en) Multiple channel carrier current telephone cable
US2036045A (en) Shielding
US2034047A (en) Coaxial circuit with stranded inner conductor
US2107177A (en) Stranded conductor
CN203812632U (zh) 复合电缆
RU162751U1 (ru) Высокочастотный симметричный герметизированный кабель
US1933261A (en) Shielding
US1880764A (en) Submarine signaling cable
US2153174A (en) Electric cable
US1923859A (en) Electric cord and cable
US1861851A (en) Submarine signaling cable
US1705913A (en) High-frequency submarine cable