(12) United States Patent
`Blouin et al.
`
`USOO6365836B1
`(10) Patent No.:
`US 6,365,836 B1
`(45) Date of Patent:
`Apr. 2, 2002
`
`(54) CROSS WEB FOR DATA GRADE CABLES
`(75) Inventors: Denis Blouin, Montreal; Jacques
`Cornibert, Verdun; Jörg-Hein Walling,
`Beaconsfield, all of (CA)
`(73) Assignee: Nordx/CDT, Inc., Pointe-Claire (CA)
`
`5,920,672 A * 7/1999 White ........................ 385/110
`5.952615 A * 9/1999 Prudhon ................. 174/113 C
`
`OTHER PUBLICATIONS
`
`tly “Condensed Chemical Dictionary”, pp. 570-571,
`
`* ) Notice:
`Subject t
`disclai
`the t
`f thi
`(*) Notice R Neil TGI. s Wier
`U.S.C. 154(b) by 0 days.
`
`Images of Belden 1711 A Datatwist 300 4PR23 shielded
`cable, 1995.*
`
`(21) Appl. No.: 09/343,998
`(22) Filed:
`Jun. 30, 1999
`Related U.S. Application Data
`(63) Continuation-in-part of application No. 09/258,374, filed on
`Feb. 26, 1999, now abandoned.
`7
`
`* cited by examiner
`
`Primary Examiner-Chau N. Nguyen
`(74) Attorney, Agent, or Firm Wolf, Greenfield & Sacks,
`P.C.
`(57)
`
`ABSTRACT
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`- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - light.
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`AcroSS web core in a high performance data cable maintains
`
`(5
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`(58) Field o Start A385/105,110
`s
`s
`s
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`Fi la f s- - - - - - - -h - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 174/113 C 113 R
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`114; 264/1 S.
`s
`174
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`s
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`(56)
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`References Cited
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`U.S. PATENT DOCUMENTS
`1940,917 A * 12/1933 Okazaki ................. 174/113 C
`
`
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`geometric Stability between plural twisted pair transmission
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`media and between each twisted pair and the cable jacket.
`The cross web core may further isolate twisted pairs from
`each other by including conductive or magnetically perme
`able materials. By So doing, loss, impedance and crosstalk
`performance are improved.
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`8 Claims, 4 Drawing Sheets
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`FIG. 1
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`1
`CROSS WEB FOR DATA GRADE CABLES
`
`This application is a continuation-in-part of prior U.S.
`patent application Ser. No. 09/258,374, filed Feb. 26, 1999,
`now abandoned.
`
`BACKGROUND
`1. Field of the Invention
`The present invention relates to high performance data
`cables employing twisted pairs of insulated conductors as
`the transmission medium. More particularly, the present
`invention relates to Such cables having improved crosstalk
`performance by use of techniques to Separate the twisted
`pairs from each other and from the cable jacket.
`2. Related Art
`High performance data cable using twisted pair transmis
`Sion media have become extremely popular. Such cable
`constructions are comparatively easy to handle, install,
`terminate and use. They also are capable of meeting high
`performance Standards.
`One common type of conventional cable for high-Speed
`data communications includes multiple twisted pairs. In
`each pair, the wires are twisted together in a helical fashion
`forming a balanced transmission line. When twisted pairs
`are placed in close proximity, Such as in a cable, electrical
`energy may be transferred from one pair of the cable to
`another. Such energy transfer between pairs is undesirable
`and is referred to as crosstalk. Crosstalk causes interference
`to the information being transmitted through the twisted pair
`and can reduce the data transmission rate and can cause an
`increase in the bit error rate. The Telecommunications
`Industry ASSociation (TIA) and Electronics Industry ASSO
`ciation (EIA) have defined Standards for crosstalk in a data
`communications cable including: TIA/EIA-568-A, pub
`lished Oct. 24, 1995; TIA/EIA568-A-1 published Sep. 25,
`1997; and TIA/EIA-568-A-2, published Aug. 14, 1998. The
`International Electrotechnical Commission (IEC) has also
`defined Standards for data communications cable crosstalk,
`including ISO/IEC 11801 that is the international equivalent
`to TIA/EIA-568-A. One high performance standard for data
`communications cable is ISO/IEC 11801, Category 5.
`Crosstalk is primarily capacitively coupled or inductively
`coupled energy passing between adjacent twisted pairs
`within a cable. Among the factors that determine the amount
`of energy coupled between the wires in adjacent twisted
`pairs, the center-to-center distance between the wires in the
`adjacent twisted pairs is very important. The center-to-center
`distance is defined herein to be the distance between the
`center of one wire of a twisted pair to the center of another
`wire in an adjacent twisted pair. The magnitude of both
`capacitively coupled and inductively coupled crosstalk Var
`ies inversely with the center-to-center distance between
`wires, approximately following an inverse Square law.
`Increasing the distance between twisted pairs will thus
`reduce the level of crosstalk interference. Another important
`factor relating to the level of croSStalk is the distance over
`which the wires run parallel to each other. Twisted pairs that
`have longer parallel runs will have higher levels of crosstalk
`occurring between them.
`In twisted pairs, the twist lay is the longitudinal distance
`between twists of the wire. The direction of the twist is
`known as the twist direction. If adjacent twisted pairs have
`the same twist lay, then the coupling is longitudinally
`additive. If twisted pairs have opposite twist directions, then
`they interlace, and their center lines will lie more closely
`together than they would within a cable in which all pairs
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`have the same twist direction. Thus due to the reduced center
`to center distance twisted pairs having opposite twist direc
`tions will have reduced crosstalk performance. In other
`words, the crosstalk tends to be higher between pairs having
`Substantially the same twist lay and opposite twist direction.
`Therefore, adjacent twisted pairs within a cable are given
`unique twist layS and the same twist directions. The use of
`unique twist layS Serves to decrease the level of crosstalk
`between adjacent twisted pairs.
`Sometimes, it would be advantageous to also use twisted
`pairs with opposing twist directions. However, as outlined
`above, the interlacing between twisted pairs having essen
`tially the same or Similar twist lay lengths will increase, thus
`reducing the croSStalk performance.
`Even if each adjacent twisted pairs in cable has a unique
`twist lay and/or twist direction, other problems may occur.
`In particular, during use mechanical StreSS may interlink
`adjacent twisted pairs. Interlinking occurs when two adja
`cent twisted pairs are pressed together filling any interstitial
`Spaces between the wires comprising the twisted pairs.
`Interlinking will cause a decrease in the center-to-center
`distance between the wires in adjacent twisted pairs and can
`cause a periodic coupling of two or more twisted pairs. This
`can lead to an increase in crosstalk among the wires in
`adjacent twisted pairs within the cable.
`One popular cable type meeting the above Specifications
`is foil shielded twisted pair (FTP) cable. FTP cable is
`popular for local area network (LAN) applications because
`it has good noise immunity and a low level of radiated
`emissions.
`Another popular cable type meeting the above Specifica
`tions is unshielded twisted pair (UTP) cable. Because it does
`not include shield conductors, UTP cable is preferred by
`installers and plant managers as it is easily installed and
`terminated. The requirements for modem State of the art
`transmission systems require both FTP and UTP cables to
`meet very stringent requirements. Thus, FTP and UTP cables
`produced today have a very high degree of balance and
`impedance regularity. In order to achieve this balance and
`regularity, the manufacturing process of FTP and UTP
`cables may include twisters that apply a back torsion to each
`wire prior to the twisting operation. Therefore, FTP and UTP
`cables have very high impedance regularities due to the
`randomization of eventual eccentricities in a twisted wire
`pair during manufacturing.
`In order to obtain yet better crosstalk performance in FTP
`and UTP cables, for example to meet future performance
`Standards, Such as proposed category 6 Standards, Some have
`introduced a Star or croSS-shaped interior Support for the data
`cable, such as disclosed by Gaeris et al. in U.S. Pat. No.
`5,789,711, issued Aug. 4, 1998.
`In conventional cables, the loSS factor or loSS tangent of
`the jacketing material has a Substantial impact upon the
`attenuation figure of data grade cables. Attenuation increases
`with proximity of the transmission media to the jacket. For
`this reason, data cables not having an interior Support Such
`as disclosed by Gaeris et al. generally have loose fitting
`jackets. The looseness of the jacket reduces the attenuation
`figure of the cable, but introduces other disadvantages. For
`example, the loose fitting jacket permits the geometric
`relationship between the individual twisted pairs to vary,
`thus varying impedance and croSStalk performance.
`In FTP cable, the effect of the loss tangent of the jacketing
`material is substantially mitigated by the shield. The shield
`ing characteristics of the foil Surrounding the twisted pairs
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`US 6,365,836 B1
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`3
`determine the effect upon different frequencies. This shield
`ing characteristic is best described by the transfer imped
`ance. However, measurement of the transfer impedance is
`difficult, especially at higher frequencies.
`The performance of shielded cable can be substantially
`improved by individually shielding the twisted pairs.
`However, such cables commonly designated as STP
`(Individually Shielded Twisted Pairs) wires are impractical,
`as they require a Substantial amount of time and Specialized
`equipment or tools for termination. Additionally, the cables
`themselves are relatively large in diameter due to the added
`bulk of the Shield, which is a Severe disadvantage, primarily
`with respect to causing poor flammability performance, but
`also with respect to Space requirements in ducts and on croSS
`COnnectS.
`Conventional interior Supports have the basic croSS form
`with parallel sides, Such as shown in FIG. 1 or a simple Star
`shape, Such as shown in FIG. 2. These shapes have a number
`of disadvantages, discussed below.
`The conventional cable configuration of FIG. 1 includes
`an interior support 101, a plurality of twisted pairs 102 of
`insulated conductors 103. Interior support 101 has arms 104
`with Straight, parallel Sides. The entire assembly is Sur
`rounded by a jacket (not shown) and possibly by a shield
`(optional, not shown).
`During the Stranding operation, in which twisted pairs 102
`and the interior support 101 are brought together and twisted
`into a cable form, the interior Support is oriented to the
`twisted pairs 102 so they can be laid up into the required
`positions. Then the interior Support 101 and twisted pairs
`102 are stranded, together. The helical deformation of the
`interior Support 101 Stretches the outer, peripheral parts of
`the Support more than the inner parts of the Support. This is
`indicated in FIG. 1 by the dashed lines 105. As the outer
`peripheral parts of the interior Support are Stretched and thus
`thinned, the space in which each individual twisted pair 102
`can move is increased. The twisted pairs 102 can move
`either tangentially to the circumference of the cable or
`radially, away from the center of the cable. This movement
`is undesirable, as it causes crosstalk and attenuation varia
`tion. Due to the latter, impedance also varies, exhibiting
`Some roughness. Crosstalk is mainly influenced by tangen
`tial displacements of the twisted pairs, assuming each pair
`has a unique lay length to reduce croSStalk. The tangential
`displacement varies the Spacing between pairs. Radial dis
`placement predominantly affects attenuation. Variation in
`radial displacement cause attenuation variation, also called
`attenuation roughness, as the distance from the center of
`each twisted pair to the jacket varies. Both of these varia
`tions also incidentally have an impact upon impedance
`roughness.
`The cable shown in FIG. 2 is that disclosed by Gaeris et
`al. This configuration has an interior Support 201 having a
`plurality of arms 202 with angled sides, giving the interior
`support an overall star shape. The arms 202 of interior
`support 201 separate a plurality of twisted pairs 203 of
`insulated conductors 204. The assembly is shielded by a foil
`shield 205, and protected by a jacket 206.
`SUMMARY OF THE INVENTION
`The present invention provides an improved high perfor
`mance data cable including a generally cross-shaped core.
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`According to one aspect of the invention, a high perfor
`mance data cable includes a plurality of twisted pairs of
`insulated conductors, a generally cross-shaped core having
`arms with flanged ends extending Sufficiently far around
`each twisted pair of insulated conductors to retain each
`twisted pair of insulated conductors, and a jacket generally
`Surrounding the plurality of twisted pairs of insulated con
`ductors and the core; whereby the plurality of twisted pairs
`of insulated conductors are held in Stable positions apart
`from each other and from the jacket. In Some embodiments
`of the cable, adjacent arms define a Substantially circular
`Void in which a twisted pair of insulated conductors is
`retained. In other embodiments of the invention, adjacent
`arms define a Substantially polygonal Void in which a
`twisted pair of insulated conductorS is retained.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`In the drawings, in which like reference designations
`indicate like elements,
`FIG. 1 is a croSS-Section of a prior art cable including an
`interior Support,
`FIG. 2 is a cross-section of the cable disclosed by Gaeris
`et al.,
`FIG. 3 is a croSS-Section of a cable according to one
`embodiment of the invention; and
`FIG. 4 is a cross-section of a cable according to another
`embodiment of the invention.
`
`DETAILED DESCRIPTION
`The present invention will be better understood upon
`reading the following detailed description in connection
`with the figures.
`FIG.3 shows a cross-section of a cable core 301 and four
`twisted pairs 302 of insulated conductors 303 according to
`one embodiment of the invention. The core includes four
`radially disposed arms 304, each having flanged distal ends
`305. Each adjacent pair of arms 304 and flanges 305 form a
`substantially circular void 306 or groove parallel to the
`central axis 307 of the core 301. The flanges 305 extend part
`way around the grooves 306, but leave an opening through
`which the twisted pairs 302 of insulated conductors 303 can
`be inserted during cable manufacture.
`During manufacture, the twisted pairs 302 of insulated
`conductors 303 are laid up into the voids 306 in the cable
`core 301. The assembly is then stranded, i.e., twisted to form
`a cable assembly. Stranding deforms the arms 304 and
`flanges 305, as indicated by the dashed lines 308. The
`deformation is more pronounced towards the distal end of
`the arms 304 and flanges 305. However, this deformation is
`far leSS pronounced than that present in prior art designs,
`Such as shown in FIGS. 1 and 2.
`To correct this deformation, the flanges may be made a bit
`thicker, in order to compensate for the deformation that
`occurs during the Stranding operation.
`According to one embodiment, the croSS web core should
`be formed of a material having a low loSS tangent. Thus, the
`attenuation of the completed cable can be minimized. Suit
`able materials include, but are not limited to polyolefins or
`any other low dielectric loss fluoropolymer. To reduce the
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`S
`dielectric loSS yet further, or allow use of higher loSS
`materials, the croSS web core may be a foamed material.
`Foamed materials can further improve overall attenuation
`and both attenuation and impedance roughness because air
`or other foaming gasses generally have lower dielectric loSS
`than the unfoamed material.
`A second embodiment of the invention is now described
`in connection with FIG. 4. This embodiment is more eco
`nomical from the Standpoint of the quantity of material used
`to construct the core. In this embodiment, the voids formed
`by the flanged arms are Substantially polygonal. Moreover,
`unnecessary material at the ends of the arms has been
`omitted.
`In this embodiment of the invention, the elements of the
`cable core 401 have substantially straight sides. Arms 402
`has Straight parallel Sides, ending at the distal end in flanges
`403. Flanges 403 also have straight sides. Flanges 403 and
`arms 402 are arranged to leave a void 404 at the end thereof.
`Adjacent arms 402 and flanges 403 form grooves or chan
`nels 405, which receive the twisted pairs 406 of insulated
`conductors 407, as described above in connection with
`grooves or channels 306 shown in FIG. 3.
`The cable formed using the embodiment of either FIG. 3
`or FIG. 4 is completed by applying a jacket 310 to the
`exterior thereof. The arms and flanges maintain the jacket at
`a fixed distance away from the twisted pairs of insulated
`conductors.
`In each embodiment of the invention, the cable core
`Separates and Stabilizes the relative positions of the twisted
`pairs of insulated conductors. The arms of the core Separate
`the twisted pairs, while the arms and flanges cooperate to
`retain the twisted pairs in fixed relative positions. This
`improves the crosstalk performance of the new cable.
`Moreover, the flanges Space the jacket away from the twisted
`pairs of insulated conductors, reducing the attenuation due
`to the loSS tangent of the jacket material. Therefore, the
`jacket can be more tightly applied, further Stabilizing the
`mechanical and electrical characteristics of the resulting
`cable.
`AS explained above, important electrical characteristics of
`finished cable include, but are not limited to, attenuation,
`attenuation roughness, impedance and impedance rough
`neSS. The overall geometry of a cable and the consistency
`with which the cable components maintain that geometry
`Substantially affects the noted characteristics.
`Embodiments of the invention improve the noted cable
`characteristics by establishing and maintaining over the
`length of the cable a beneficial geometric relationship
`between and among twisted pairs and the cable jacket. The
`arms and flanges of embodiments of the invention may just
`barely maintain the jacket away from the twisted pairs or
`may Substantially maintain the jacket away from the twisted
`pairs, provided the geometry remains constant over the
`length of the cable.
`The following embodiments of the present invention push
`the performance of FTP cable close to that of STP cable.
`This can be accomplished by using a croSS web core as
`described above, whose surface or body has been rendered
`conductive, for example, by depositing a metallic Shielding
`material onto the plastic.
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`Metallic depositions can be made on the croSS web core
`either electrolytically or using a current leSS process. Suit
`able materials are, for instance, nickel, iron and copper. The
`first two materials having the added advantage of Superior
`Shielding effectiveness for a given coating thickneSS due to
`the relatively high permeability of those materials.
`Hence, if the cross web core is covered with or formed of
`an electrically conductive material, preferably a material
`also having a high permeability, then an improvement of the
`Shielding effectiveness can be obtained. The conductive
`Surfaces of the croSS web core should be longitudinally in
`contact with the Surrounding foil shield. In this way the croSS
`web core and the foil shield combine to form shielded
`Sectored compartments for each twisted pair. In fact, if the
`Shielding material on or forming the croSS web core has a
`Sufficient thickness to provide Shielding equivalent to the
`Shielding effectiveness of the Surrounding foil shield, then
`performance close to STP cable can be attained. Thus, cables
`can be designed which have geometric characteristics simi
`lar or identical to high performance FTP cable while having
`substantially the electric performance of STP cable.
`The foregoing cable employing a conductively coated
`croSS web core is advantageous in another, unexpected way.
`By shielding the twisted pairs from the material of the cross
`web core, the inventive construction of this embodiment
`renders the loSS tangent of the croSS web core material
`unimportant. Therefore, the material of the croSS web core
`may be chosen without regard for its loSS tangent, but rather
`with regard to Such considerations as cost, flammability,
`smoke production and flame spread.
`Conductive croSS web cores including Suitable Shielding
`materials can be produced a variety of ways. The Surface of
`a non-conductive polymeric croSS web can be rendered
`conductive by using conductive coatings, which could also
`be polymeric. Another possibility is to use a Sufficiently
`conductive polymer to construct the croSS web core.
`One process which can produce a Suitable coating is
`electrolytic metalization. However, the penetration of the
`coating into the grooves or channels of the croSS web core
`during production is a bit more difficult. This process tends
`to produce an accumulation of deposited metal at the tips of
`the croSS web core arms or flanges. Another possibility
`would be to deposit the metal in a current leSS process. The
`most common metals used for these processes are nickel and
`copper. Alternatively, the croSS web cores could be metal
`ized by vapor deposition.
`AS mentioned above, conductivity can be achieved by use
`of conductive materials for the croSS web core material.
`Moreover, other coatings can be combined with a croSS web
`core of a ferrite-loaded polymer, in order to decrease pair
`to-pair coupling. Such a croSS web core material provides
`magnetic properties which improve the croSS talk isolation.
`Moreover, if such a cross web core is additionally metalized
`at the Surface, then the metal coating can be Substantially
`Smaller than in the previously described designs.
`The present invention has now been described in connec
`tion with a number of specific embodiments thereof
`However, numerous modifications which are contemplated
`as falling within the Scope of the present invention should
`now be apparent to those skilled in the art. Therefore, it is
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`intended that the Scope of the present invention be limited
`only by the Scope of the claims appended hereto.
`What is claimed is:
`1. A high performance data cable comprising:
`a plurality of twisted pairs of insulated conductors,
`a generally cross-shaped core having arms with flanged
`ends extending Sufficiently far around each twisted pair
`of insulated conductors to retain each twisted pair of
`insulated conductors in Stable positions apart from each
`other, thereby controlling cross-talk between adjacent
`twisted pairs whose distance apart does not vary during
`cable installation and use; and
`a jacket generally Surrounding the plurality of twisted
`pairs of insulated conductors and the core and held at
`a Substantially constant distance away from each
`twisted pair of insulated conductors by the arms of the
`cross-shaped core, thereby controlling attenuation
`variation due to a loSS tangent of the jacket;
`wherein two adjacent arms of the cross-shaped core define
`a Substantially polygonal Void in which one of the
`twisted pairs of insulated conductorS is retained.
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`2. The high performance data cable of claim 1, wherein
`two adjacent arms of the cross-shaped core maintain the
`jacket at a fixed distance away from the twisted pairs of
`insulated conductors.
`3. The high performance data cable of claim 1, wherein
`the generally cross-shaped core comprises:
`a conductive material.
`4. The high performance data cable of claim 3, wherein
`the conductive material is a Surface coating on the generally
`cross-shaped core.
`5. The high performance data cable of claim 3, wherein
`the conductive material defines the croSS-shaped core.
`6. The high performance data cable of claim 3, wherein
`the cross-shaped core further comprises:
`a material having high permeability.
`7. The high performance data cable of claim 4, wherein
`the conductive material also has high permeability.
`8. The high performance data cable of claim 5, wherein
`the conductive material also has high permeability.
`
`k
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`UNITED STATES PATENT AND TRADEMARK OFFICE
`CERTIFICATE OF CORRECTION
`
`PATENT NO. : 6,365,836 B1
`DATED
`: April 2, 2002
`INVENTOR(S) : Blouin, Denis, Cornibert, Jaques and Walling, Jörg-Hein
`
`Page 1 of 1
`
`It is certified that error appears in the above-identified patent and that said Letters Patent is
`hereby corrected as shown below:
`
`Column 2.
`Line 35, please replace “modem” with -- modern --.
`
`Signed and Sealed this
`
`Eleventh Day of June, 2002
`
`Attest.
`
`Attesting Officer
`
`JAMES E ROGAN
`Director of the United States Patent and Trademark Office
`
`