CA1096453A - Multiscreen communication cable - Google Patents
Multiscreen communication cableInfo
- Publication number
- CA1096453A CA1096453A CA283,383A CA283383A CA1096453A CA 1096453 A CA1096453 A CA 1096453A CA 283383 A CA283383 A CA 283383A CA 1096453 A CA1096453 A CA 1096453A
- Authority
- CA
- Canada
- Prior art keywords
- cable
- group
- groups
- electrical conductors
- surrounding
- 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
Links
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
- H01B11/085—Screens specially adapted for reducing cross-talk composed of longitudinal tape conductors
Abstract
ABSTRACT OF THE DISCLOSURE:
A multiscreen communication cable particularly for use in the transmission of pulse code modulation signals is disclosed.
The cable comprises a cable core having first and second groups of insulated electrical conductors for transmission of communication signals in both directions, with a metal screen surrounding the first group and a second metal screen surrounding the second group for attenuating crosstalk between the first and the second groups of insulated electrical conductors, each screen being applied lon-gitudinally with an unsealed overlap, an insulating core wrap sur-rounding the cable core, a metal shield surrounding the insulating core wrap, and a plastic jacket surrounding the metal shield.
A multiscreen communication cable particularly for use in the transmission of pulse code modulation signals is disclosed.
The cable comprises a cable core having first and second groups of insulated electrical conductors for transmission of communication signals in both directions, with a metal screen surrounding the first group and a second metal screen surrounding the second group for attenuating crosstalk between the first and the second groups of insulated electrical conductors, each screen being applied lon-gitudinally with an unsealed overlap, an insulating core wrap sur-rounding the cable core, a metal shield surrounding the insulating core wrap, and a plastic jacket surrounding the metal shield.
Description
S~
This inven-t:ion relates to conm~llnication cables, more particularly cables usecl in pulse code modulation systems.
Telephone cable manufacturers strive continually -to meet the demanding requiremen-ts of a growing te]ephone technoloyy. One of the more recent modulation schemes is the utiliz~tion of pulse code modulation (PCM) on balanced cable pairs. This digital base-band system, commonly referred to as a Tl carrier system has seve ral advantages over conventional analog systems. Recently an up~
graded version of the T1 known as a Tl-C carrier system has been introduced. However, this new system places more strinqent demands on cable performance.
It is therefore the object of the present invention to reduce the undesirable near end crosstalk coupling to a greater extent than the prior art devices in an effective and economical manner.
Indeed, due to practical limitations in construction o balanced pair cables, some degree of electrical coupling exists from any given conductor pair to any other conductor pair within the cable. This manifests itself as an undesired electrical dis-turbance referred to as crosstalk~
The electrical coupling from one cable pair to anotherresults ~rom electro-magnetic propayation across the separating distance. To impede this coupling mechanism, screen tapes have been placed in the core in the path of the wave propagation. This results in attenuation of the wave through reflections at the die-lectric-metallic interEaces and eddy current losses in the metal-~ lic screen.
`; The existing art in screened cables is typically a cahle comprising Z, T, S, or D type screens. The æ, ~ or S types are single screen designs which divide the core into two or more groupswhere electrical separation between any two groups ls in the form of a single screen extending parallel to the cable axls along the - 1 '~
i3 length oE -the cable. rrhe D screen design is such that the cable is divided into two conductor groups wi-th one group being comple-tely surrounded by -the screen material.
The cable, in accordance with the invention, comprises a cable core having firs-t and second groups of insula-ted elec-tri-cal conductors for transmission of communica-tion signals in a first and second direction respectively, a first me-tal screen surrounding the first group of insulated electrical conductors and a second metal screen surrounding the second group of insula-ted electrical conductors for attenuating crosstalk between thefirst and second groups of insulated electrical conductors, each screen being applied longitudinally with an unsealed overlap, and a suitable protective covering overall. The interstices of the cable core are filled with a grease-like material to inhibit the migration of water in the cable core.
The metal screen is preferably applied longitudinally by folding so as to completely enclose the pair group and to overlap ; at the seam without sealing. Thescreen may be constructed of an aluminum tape or other suitable conducting material coated prefera-bly on both sides with an insulating plastic material.
The protective covering preferably consists of an insula-ting core wrap surrounding the cable core, a metal shield applied over the core wrap and a plastic jacket surrounding the overall shield, although other types of covering are also envisaged.
The insulating core wrap may be applied either longitu-dinally or helically with sufficient overlap so as to comple-tely enclose the cable core and provide adequate insulation from the overall shield as well as an adequate heat barrier for -the appli-cation of the surrounding plastic jac]cet.
The overall metal shield which may be made of aluminum, may be applied longitudinally with an overlap.
The invention will now be disclosed, by way of example, with reference to the accompanying drawings in which:
This inven-t:ion relates to conm~llnication cables, more particularly cables usecl in pulse code modulation systems.
Telephone cable manufacturers strive continually -to meet the demanding requiremen-ts of a growing te]ephone technoloyy. One of the more recent modulation schemes is the utiliz~tion of pulse code modulation (PCM) on balanced cable pairs. This digital base-band system, commonly referred to as a Tl carrier system has seve ral advantages over conventional analog systems. Recently an up~
graded version of the T1 known as a Tl-C carrier system has been introduced. However, this new system places more strinqent demands on cable performance.
It is therefore the object of the present invention to reduce the undesirable near end crosstalk coupling to a greater extent than the prior art devices in an effective and economical manner.
Indeed, due to practical limitations in construction o balanced pair cables, some degree of electrical coupling exists from any given conductor pair to any other conductor pair within the cable. This manifests itself as an undesired electrical dis-turbance referred to as crosstalk~
The electrical coupling from one cable pair to anotherresults ~rom electro-magnetic propayation across the separating distance. To impede this coupling mechanism, screen tapes have been placed in the core in the path of the wave propagation. This results in attenuation of the wave through reflections at the die-lectric-metallic interEaces and eddy current losses in the metal-~ lic screen.
`; The existing art in screened cables is typically a cahle comprising Z, T, S, or D type screens. The æ, ~ or S types are single screen designs which divide the core into two or more groupswhere electrical separation between any two groups ls in the form of a single screen extending parallel to the cable axls along the - 1 '~
i3 length oE -the cable. rrhe D screen design is such that the cable is divided into two conductor groups wi-th one group being comple-tely surrounded by -the screen material.
The cable, in accordance with the invention, comprises a cable core having firs-t and second groups of insula-ted elec-tri-cal conductors for transmission of communica-tion signals in a first and second direction respectively, a first me-tal screen surrounding the first group of insulated electrical conductors and a second metal screen surrounding the second group of insula-ted electrical conductors for attenuating crosstalk between thefirst and second groups of insulated electrical conductors, each screen being applied longitudinally with an unsealed overlap, and a suitable protective covering overall. The interstices of the cable core are filled with a grease-like material to inhibit the migration of water in the cable core.
The metal screen is preferably applied longitudinally by folding so as to completely enclose the pair group and to overlap ; at the seam without sealing. Thescreen may be constructed of an aluminum tape or other suitable conducting material coated prefera-bly on both sides with an insulating plastic material.
The protective covering preferably consists of an insula-ting core wrap surrounding the cable core, a metal shield applied over the core wrap and a plastic jacket surrounding the overall shield, although other types of covering are also envisaged.
The insulating core wrap may be applied either longitu-dinally or helically with sufficient overlap so as to comple-tely enclose the cable core and provide adequate insulation from the overall shield as well as an adequate heat barrier for -the appli-cation of the surrounding plastic jac]cet.
The overall metal shield which may be made of aluminum, may be applied longitudinally with an overlap.
The invention will now be disclosed, by way of example, with reference to the accompanying drawings in which:
- 2 -i45i~
Figure l illustrates an embodiment oE a communicatlon cable in accordance with the invention shown in cross-section; and Figure 2 illustrates a perEormance comparison of the com-munication cable in accordance wlth the invention and a cable in accorclance w.ith the bes-t prior ar-t.
Referring to Figure l, there is shown an embodiment of a co~munication ca~le in accordance with the invention. ~he cable comprises of a plurality of pairs of conductors lO ~usually colour coded) insulated with solid or cellular polyethelene and divided in two groups, one group including all the conductors carrying si-gnals going in one direction (normally called "go" conductors) and the other group including all the conductors carrying signals in the other direction (normally called ~Ireturn~ conductors). The number of conductors in the "go" group is normally the same as the number of conductors in the "return" group, but the number of con-ductors in one of the groups could conceivably be greater than in the other. In addition, a cable could contain additional compo-nents such as pairs of coaxes which are not part of the PCM system in one or both groups or outside of the groups entirely.
Bach group is individually enclosed with its own comple-tely surrounding screen 12. The screens are applied longitudinally ~`
by folding so as to completely enclose the conductor group and to overlap at the seam. The overlap is not sealed. Each screen is then held in place by a binder (not shown) which may be colour co-ded For purposes of identification.
The screens are electrically insulated from one another and from the other conductors and shield in the cable. They are normally constructed of an aluminum tape or any other suitable con-ducting material coated on both sides with an insulating plastic.
The plastic may extend beyond the edges of the metal thereby insu-ring the high voltage integrity of the cable core.
The screened groups are then brought together to form a ii,3 cable core 1~l which h.ls a circular shape as viewe(l ln cross-scc-tion. The screened ~roups may bc cahled (e.~. twisted) to~ether, or else the groups could be laid up -together ln a truly parallel fashion wi-th no twist. A suitable insulating core wrap 16 is then applied either lon~ltudlnally or helically with sufficlent overlap so as to completely enclose the cable core~ A binder (not shown) may be applled over the core wrap so as to hold the core wrap ln position. A metal shleld 18, such as a corrosion proof alumlnum tape, is then applled longitudinally over the core wrap 16 with a seam overlap and a plastic jacket 20 applied overall.
The insulating core wrap provides a heat barrier for the subsequent application of the overall jacket and also insulates the cable core from the overall shield to lnsure hlgh voltage protec-tion. The interstices of the cable core may be filled with a sui-table material such as petroleum jelly to inhibit the migration of water into the cable core.
The screens of the above disclosed cable core ef-Eective-ly divide the cable core into two groups of cable conductors which are electrically insulated from one another and tend to behave electrically as independent cables. The new design presents two double attenuation~reflection screens between the distrubing pairs of conductors and the disturbed pairs. The resulting increase in near end crosstalk (NEXT~ loss obtained, as shown in figure 2,over the prior art screen designs is in the orderor 13 to 20 dBdepending on the number of pairs in a group. It can be shown that merely doubling the thickness of a single screen design will result ln an improvement in cross-talk performance of about 3 dB, which is much less than the 13 to 20 dB improvement obtained with the twin screen design in accordance with the invention. The superior per-formance of the cable in accordance with the invention is due tothe two additional dielectric screen interfaces produced by divi-ding -the screen material into two distinct insulating screens and ,53 subsequently enclosing each pair grouE) separately by these screens.
Al-though the invention has been disclosed wi-th regard -to a preferrecl embodiment, it is to be understood that the invention is not restricted to such embodimen-t and that various modi~ications may be made thereto within the scope and spirit of the following claims.
.
Figure l illustrates an embodiment oE a communicatlon cable in accordance with the invention shown in cross-section; and Figure 2 illustrates a perEormance comparison of the com-munication cable in accordance wlth the invention and a cable in accorclance w.ith the bes-t prior ar-t.
Referring to Figure l, there is shown an embodiment of a co~munication ca~le in accordance with the invention. ~he cable comprises of a plurality of pairs of conductors lO ~usually colour coded) insulated with solid or cellular polyethelene and divided in two groups, one group including all the conductors carrying si-gnals going in one direction (normally called "go" conductors) and the other group including all the conductors carrying signals in the other direction (normally called ~Ireturn~ conductors). The number of conductors in the "go" group is normally the same as the number of conductors in the "return" group, but the number of con-ductors in one of the groups could conceivably be greater than in the other. In addition, a cable could contain additional compo-nents such as pairs of coaxes which are not part of the PCM system in one or both groups or outside of the groups entirely.
Bach group is individually enclosed with its own comple-tely surrounding screen 12. The screens are applied longitudinally ~`
by folding so as to completely enclose the conductor group and to overlap at the seam. The overlap is not sealed. Each screen is then held in place by a binder (not shown) which may be colour co-ded For purposes of identification.
The screens are electrically insulated from one another and from the other conductors and shield in the cable. They are normally constructed of an aluminum tape or any other suitable con-ducting material coated on both sides with an insulating plastic.
The plastic may extend beyond the edges of the metal thereby insu-ring the high voltage integrity of the cable core.
The screened groups are then brought together to form a ii,3 cable core 1~l which h.ls a circular shape as viewe(l ln cross-scc-tion. The screened ~roups may bc cahled (e.~. twisted) to~ether, or else the groups could be laid up -together ln a truly parallel fashion wi-th no twist. A suitable insulating core wrap 16 is then applied either lon~ltudlnally or helically with sufficlent overlap so as to completely enclose the cable core~ A binder (not shown) may be applled over the core wrap so as to hold the core wrap ln position. A metal shleld 18, such as a corrosion proof alumlnum tape, is then applled longitudinally over the core wrap 16 with a seam overlap and a plastic jacket 20 applied overall.
The insulating core wrap provides a heat barrier for the subsequent application of the overall jacket and also insulates the cable core from the overall shield to lnsure hlgh voltage protec-tion. The interstices of the cable core may be filled with a sui-table material such as petroleum jelly to inhibit the migration of water into the cable core.
The screens of the above disclosed cable core ef-Eective-ly divide the cable core into two groups of cable conductors which are electrically insulated from one another and tend to behave electrically as independent cables. The new design presents two double attenuation~reflection screens between the distrubing pairs of conductors and the disturbed pairs. The resulting increase in near end crosstalk (NEXT~ loss obtained, as shown in figure 2,over the prior art screen designs is in the orderor 13 to 20 dBdepending on the number of pairs in a group. It can be shown that merely doubling the thickness of a single screen design will result ln an improvement in cross-talk performance of about 3 dB, which is much less than the 13 to 20 dB improvement obtained with the twin screen design in accordance with the invention. The superior per-formance of the cable in accordance with the invention is due tothe two additional dielectric screen interfaces produced by divi-ding -the screen material into two distinct insulating screens and ,53 subsequently enclosing each pair grouE) separately by these screens.
Al-though the invention has been disclosed wi-th regard -to a preferrecl embodiment, it is to be understood that the invention is not restricted to such embodimen-t and that various modi~ications may be made thereto within the scope and spirit of the following claims.
.
Claims (4)
1. A communication cable comprising:
a) a cable core having two groups of insulated electrical conductors, a first group for transmission of communication signals in a first direction and a second group for transmission of communication signals in the opposite direction;
b) a grease-like material filling up the interstices of the cable core to inhibit the migration of water in the cable core;
c) an individual metal screen surrounding the first group of insulated electrical conductors and a second individual metal screen surrounding the second group of insulated electrical conductors for attenuating cross-talk between the first and second groups of insulated electrical conductors, each screen being applied longitudinally with an unsealed overlap; and d) a protective covering applied overall.
a) a cable core having two groups of insulated electrical conductors, a first group for transmission of communication signals in a first direction and a second group for transmission of communication signals in the opposite direction;
b) a grease-like material filling up the interstices of the cable core to inhibit the migration of water in the cable core;
c) an individual metal screen surrounding the first group of insulated electrical conductors and a second individual metal screen surrounding the second group of insulated electrical conductors for attenuating cross-talk between the first and second groups of insulated electrical conductors, each screen being applied longitudinally with an unsealed overlap; and d) a protective covering applied overall.
2. A communication cable as defined in claim 1, where-in the metal screen is made of an aluminum tape coated on both sides with an insulating material.
3. A communication cable as defined in claim 2, wherein the individual conductors are insulated with solid polyethelene.
4. A communication cable as defined in claim 2, where-in the individual conductors are insulated with cellular polyethelene.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA283,383A CA1096453A (en) | 1977-07-22 | 1977-07-22 | Multiscreen communication cable |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA283,383A CA1096453A (en) | 1977-07-22 | 1977-07-22 | Multiscreen communication cable |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1096453A true CA1096453A (en) | 1981-02-24 |
Family
ID=4109200
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA283,383A Expired CA1096453A (en) | 1977-07-22 | 1977-07-22 | Multiscreen communication cable |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1096453A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0169987A1 (en) * | 1984-07-30 | 1986-02-05 | QUANTUM CHEMICAL CORPORATION (a Virginia corp.) | Communications cables |
| WO1993016478A1 (en) * | 1992-02-06 | 1993-08-19 | Telefonaktiebolaget Lm Ericsson | An electric cable |
-
1977
- 1977-07-22 CA CA283,383A patent/CA1096453A/en not_active Expired
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0169987A1 (en) * | 1984-07-30 | 1986-02-05 | QUANTUM CHEMICAL CORPORATION (a Virginia corp.) | Communications cables |
| US4675471A (en) * | 1984-07-30 | 1987-06-23 | Norchem, Inc. | Electrical cables |
| WO1993016478A1 (en) * | 1992-02-06 | 1993-08-19 | Telefonaktiebolaget Lm Ericsson | An electric cable |
| EP0558463A1 (en) * | 1992-02-06 | 1993-09-01 | Telefonaktiebolaget Lm Ericsson | An electric cable |
| US5391836A (en) * | 1992-02-06 | 1995-02-21 | Telefonaktiebolaget L M Ericsson | Electric cable |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |