United States Patent (19)
`Mottine et al.
`
`US006037546A
`Patent Number:
`11
`(45) Date of Patent:
`
`6,037,546
`Mar. 14, 2000
`
`54 SINGLE-JACKETED PLENUM CABLE
`75 Inventors: John J. Mottine, Phoenix; Kenneth S.
`Koehler, Glendale; Sayed J.
`Mirkazemi, Peoria; William B.
`Dawson, Phoenix, all of Ariz.
`73 Assignee: Belden Communications Company,
`Phoenix, Ariz.
`
`21 Appl. No.: 09/113,949
`22 Filed:
`Jul. 10, 1998
`
`e - V's
`
`5,563,377 10/1996 Arpin et al. .
`5,600,097 2/1997 Bleich et al..
`5,670,748 9/1997 Gingue et al..
`5,770,820 6/1998 Nelson et al. .................. 174/121 AX
`5,814,768 9/1998 Wessels et al. ................... 174/110 FC
`OTHER PUBLICATIONS
`UL-444 Standard for Safety Communications Cables, Jun.
`1994.
`UL-910 Burn Test, Mar. 1991.
`TIA/EIA Standard, Commercial Building Telecommunica
`tions Cabling Standard, Oct. 1995.
`Primary Examiner Kristine Kincaid
`Related U.S. Application Data
`Assistant Examiner-Chau. N. Nguyen
`Attorney, Agent, or Firm Snell & Wilmer L.L.P.
`63 Continuation-in-part of application No. 08/857,018, May
`15, 1997, abandoned, which is a continuation-in-part of
`57
`ABSTRACT
`application No. 08640.262 Apr. 30, 1996.
`p
`A communications cable having Superior electrical charac
`(51) Int. Cl. ................................................. H01B 700
`teristics, and meeting the burn requirements for plenum
`52 U.S. Cl. ............................... 174/110 PM. 174/113 R;
`174/121. A applications has a core formed of one or more twisted wire
`58 Field of Search ...................... 174110 PM. 110 FC,
`pairs having primary insulation formed of a suitable
`174/110 F, 113 R, 120 R, 121 A material, Such as high density polyethylene. The core is
`s
`s
`s
`Surrounded by a single outer jacket formed from a material
`References Cited
`having excellent heat/flame resistance characteristics and
`acceptable electrical characteristics that are Substantially
`U.S. PATENT DOCUMENTS
`Stable at relatively high temperatures, Such as a foamed
`3,516,859 6/1970 Gerland et al..
`thermoplastic halogenated polymer, for example polyvi.
`3,692.924 9/1972 Nye.
`nylidene fluoride material. The electrical conductors utilized
`4,412,094 10/1983 Dougherty et al. .
`by the cable are oversized (relative to conventional 24 gauge
`4,605,818 8/1986 Arroyo et al..
`conductors) to enhance the electrical performance of the
`4,692,381
`9/1987 Pecsok.
`cable. An air gap formed between the conductor core and the
`4,781,433 11/1988 Arroyo et al..
`outer jacket further enhances the electrical performance of
`4,804,702 2/1989 Bartoszek.
`the cable. In addition, the cable employs twisted pairs
`4.881,794 11/1989 Bartoszek.
`having Specific twist lengths that enable the cable to exceed
`4,969,706 11/1990 Hardin et al..
`the electrical performance of conventional Category 5
`5,110,998 5/1992 Muschiatti ...................... 174/110 FX cables.
`5,173,960 12/1992 Dickinson.
`5,268,531 12/1993 Nguyen et al..
`5,276,759
`1/1994 Nguyen et al..
`
`56)
`
`
`
`8 Claims, 13 Drawing Sheets
`
`

`

`U.S. Patent
`
`Mar. 14, 2000
`
`Sheet 1 of 13
`
`6,037.546
`
`
`
`U.S. Patent
`
`Mar. 14, 2000
`
`Sheet 1 of 13
`
`6,037,546
`
`
`
`
`
`
`
`
`FIG.|
`
`
`
`Page 2
`
`
`
`CommsScope Exhibit 1049
`
`U.S. Patent
`
`Mar. 14, 2000
`
`Sheet 1 of 13
`
`6,037,546
`
`
`
`
`
`
`
`
`
`
`
`
`
`FIG.|
`
`

`

`U.S. Patent
`
`Mar. 14, 2000
`
`Sheet 2 of 13
`
`6,037.546
`
`
`
`FIG. A
`
`U.S. Patent
`
`Mar. 14, 2000
`
`Sheet 2 of 13
`
`6,037,546
`
`
`
`FIG. IA
`
`Page 3
`
`CommsScope Exhibit 1049
`
`U.S. Patent
`
`Mar. 14, 2000
`
`Sheet 2 of 13
`
`6,037,546
`
`
`
`FIG. IA
`
`

`

`U.S. Patent
`
`Mar. 14, 2000
`
`Sheet 3 of 13
`
`6,037.546
`
`
`
`U.S. Patent
`
`Mar. 14, 2000
`
`Sheet 3 of 13
`
`6,037,546
`
`SS
`
`DS LS
`
`Page 4
`
`
`
`CommsScope Exhibit 1049
`
`U.S. Patent
`
`Mar. 14, 2000
`
`Sheet 3 of 13
`
`6,037,546
`
`Y Z
`
`
`FIG. 3
`
`
`
`
`

`

`U.S. Patent
`
`Mar. 14, 2000
`
`Sheet 4 of 13
`
`6,037.546
`
`NEXT - dB
`
`NEXT - dB
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`0.1
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`0.1
`
`II, III
`|INIMIII
`IVIMI II
`IIMINI
`|| || "NIE I
`||||||INIII
`|| || || ||
`I I I II
`|| || || ||
`I I I II
`
`1
`Frequency (MHz)
`
`100
`
`1000
`
`67.2
`
`FIG. 4A
`
`
`
`
`
`III II
`INATIII
`IIM III
`IIMH || III
`I I I II
`|| || || ||
`I I I II
`
`1
`
`1OO
`10
`Frequency (MHz)
`
`1OOO
`
`FIG. 4B
`
`

`

`U.S. Patent
`
`Mar. 14, 2000
`
`Sheet 5 of 13
`
`6,037.546
`
`100
`
`NEXT - dB
`
`
`
`NEXT - dB 60
`50
`
`40
`
`30
`
`20
`10
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`O
`0.1
`
`I I I II
`UK III
`IIMKIII
`INIMII
`INMAI
`|| ||NF||
`II ||
`4
`||
`II III
`I I I II
`|| || || ||
`
`1
`
`100
`10
`Frequency (MHz)
`
`1000
`
`FIG. 4C
`
`I I I II
`II, III
`|INAIIII
`IIM III
`III
`|| ||N|| ||
`I I I
`II
`|| || || ||
`|| || || ||
`III II
`
`
`
`1000
`
`1
`
`10
`100
`Frequency (MHz)
`
`FIG. 4D
`
`

`

`U.S. Patent
`
`Mar. 14, 2000
`
`Sheet 6 of 13
`
`6,037.546
`
`NEXT - dB
`
`100
`90
`
`80
`70
`
`60
`50
`
`40
`30
`20
`10
`
`
`
`O
`0.1
`
`III III
`INAIIII
`I"NMINII
`IIM II
`||N INI
`IIII
`I I I
`II
`I I I II
`I I II
`|| || || ||
`
`1
`
`1000
`
`Frequency (MHz)
`FIG. 4E
`
`
`
`100
`
`NEXT - dB
`
`III I II
`IIM III
`|MAIIII
`INIMH ||
`|M||
`||||INII
`|| || || ||
`|| || || ||
`|| || || ||
`| || || ||
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`1
`
`100
`10
`Frequency (MHz)
`
`1OOO
`
`FIG. 4F
`
`

`

`U.S. Patent
`
`Mar. 14, 2000
`
`Sheet 7 of 13
`
`6,037.546
`
`
`
`
`
`
`
`
`
`SILNE WERITTSVEIN IXEN - 97 "5)||-||
`
`
`
`
`
`
`
`U.S. Patent
`
`Mar. 14, 2000
`
`Sheet 7 of 13
`
`6,037,546
`
`
`
`
`37.4
`
`2.5
`
`58.5
`
`2.0
`
`
`
`
`12.4
`
`13.0
`
`6.8
`
`8.3
`
`
`
`
`
`
`
`25.0
`
`20.7
`
`22.6
`
`20.0
`
`
`
`
`21.7
`
`18.6
`
`12.9
`
`14.0
`
`
`
`
`25.9
`
`24.9
`
`27.0
`
`27.1
`
`
`
`
`19.5
`
`21.1
`
`13.9
`
`11.9
`
`
`
`
`16.0
`
`29.8
`
`19.4
`
`23.1
`
`3.8
`
`10.0
`
`14.3
`
`13.8
`
`14.2
`
`15.9
`
`18.6
`
`13.4
`
`25.0
`
`25.8
`
`25.5
`
`24.0
`
`26.9
`
`(dB)
`MIN
`
`32
`
`35
`
`39
`
`41
`
`100
`
`62.5
`
`31.25
`
`25
`
`42
`
`20
`
`
`
`
`FIG. 4G - NEXT MEASUREMENTS
`
`18.3
`
`16.1
`
`19.2
`
`20.7
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`20.6
`
`25.7
`
`13.0
`
`15.9
`
`14.6
`
`21.8
`
`25.7
`
`19.1
`
`19.7
`
`10.2
`
`13.6
`
`20.4
`
`25.0
`
`
`
`
`
`
`
`24.3
`
`
`
`
`26.0
`
`20.8
`
`13.1
`
`16.7
`
`(Deviation in dB)
`PAIR #2/PAIR #4
`
`(Deviation in dB)
`PAIR #2/PAIR #3
`
`(Deviation in dB)
`PAIR #1/PAIR #4
`
` PAIR #3/PAIR #4
`(Deviation in dB)
`
`
`
`
`
`
`
`
`
`
`
`
`22.5
`
`24.4
`
`22.3
`
`23.7
`
`27.3
`
`18.8
`
`(Deviation in dB)
`PAIR #1/PAIR #2
`
`11.9
`
`29.0
`
`15.0
`
`12.0
`
`12.7
`
`13.8
`
`(Deviation in dB)
`PAIR #1/PAIR #3
`
`
`
`
`44
`
`47
`
`64
`
`CAT 5 MIN (dB)
`
`
`
`
`16
`
`10
`
`0.772
`
`f (MHz)
`
`

`

`U.S. Patent
`
`NEXT - PS
`
`(dB)
`
`100
`90
`
`80
`70
`
`60
`50
`
`40
`
`30
`
`20
`
`10
`
`
`
`
`
`
`
`
`
`
`
`Mar. 14, 2000
`Sheet 8 of 13
`6,037.546
`|| || || ||
`III || ||
`NAIIII
`INNMII
`II" EMII
`|| ||NIM||
`|| || 4
`||
`|| ||
`||
`||
`I I IIH ||
`I I I II
`
`O
`O. 1
`
`1
`
`1OO
`10
`Frequency (MHz)
`FIG. 5A
`
`NEXT - PS
`
`(dB)
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`I I I II
`IIII
`IMAIIII
`INXIII
`|M||
`|| ||N|M||
`I I I
`II
`III II
`|| || ||
`||
`|| || || ||
`
`
`
`0.1
`
`1
`
`1000
`
`100
`10
`Frequency (MHz)
`FIG. 5B
`
`

`

`U.S. Patent
`
`Mar. 14, 2000
`
`Sheet 9 of 13
`
`6,037.546
`
`100
`
`
`
`
`
`
`
`
`
`
`
`NEXT - PS
`
`(dB)
`
`IIII
`III || ||
`IANAIIII
`IWWII
`||||WII
`|| ||NMI
`I I I
`II
`I I I II
`II II
`|
`I I I II
`
`1
`
`1
`
`1OO
`10
`Frequency (MHz)
`FIG. 5C
`
`1000
`
`NEXT - PS
`
`(dB)
`
`100
`90
`
`80
`
`70
`
`60
`50
`
`40
`30
`
`20
`
`10
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`III II
`UIII
`IVIII
`INMIII
`III"NMI
`|| ||NMI
`I I I
`II
`I I I II
`I I I II
`I I I II
`
`0.1
`
`1
`
`1000
`
`100
`10
`Frequency (MHz)
`FIG. 5D
`
`

`

`U.S. Patent
`
`6,037.546
`
`
`
`
`
`
`
`SLNEMINERITTSVEIN INTIS NEINWOd IXEN – EIG "SDI
`
`
`
`
`
`U.S. Patent
`
`Mar. 14, 2000
`
`Sheet 10 of 13
`
`6,037,546
`
`
`
`
`2.0
`
`22.0
`
`2.1
`
`
`
`
`7.0
`
`5.4
`
`6.2
`
`
`
`
`
`
`
`2.0
`
`6.5
`
`| 12.6
`
`10.8
`
`13.6
`
`| 10.2
`
`16.5
`
`9.8
`
`| (MHz)
`
`32
`
`35
`
`39
`
`'
`
`MIN
`
`100
`
`31.25 | 62.5
`
`A1
`
`25
`
`42
`
`20
`
`44
`
`16
`
`| 15.7
`
`12.2
`
`| 13.4
`
`| 10.0
`
`20.1
`
`13.4
`
`
`
`
`
`
`
`11.7 | 17.5
`
`| 20.6 |
`
`| 10.7 |
`
`11.1
`
`12.8 |
`
`| 12.7
`
`| 18.0
`
`| 14.9
`
`
`
`
`8.9
`
`
`
`
`
`
`
`
`
`
`FIG. 5E - NEXT POWER SUM MEASUREMENTS
`
`
`
`
`
`
`
`| 12.3
`
`| 10.2
`
`| 12.0
`
`16.9
`
`17.1
`
`14.9 |
`
`ern
`PAIR #4
`
`
`
`
`
`
`
`| 12.9
`
`12.6
`
`| 11.9
`
`| 15.0
`
`16.2
`
`7.8
`
`9.9
`
`9.0
`
`10.3
`
`| 10.9
`
`11.5
`
`
`
`
`
`
`
`
`
`
`(Deviation in dB)
`
`(Deviation in dB)
`
`ges
`PAIR #3
`
`(Deviation in dB)
`
`cut
`PAIR #2
`
`
`
`
`
`
`
`
`
`
`11.3
`
`10.9 |}
`
`| 11.2
`
`12.3
`
`11.1
`
`(Deviation in dB)
`
`PAIR #1
`
`47
` (dB)
`
`48
`
`53
`
`62
`
`64
`
`|
`
`CAT5MIN (dB)
`
`
`
`
`
`
`10
`
`8
`
`4
`
`1
`
`0.772
`
`f (MHz)
`
`

`

`U.S. Patent
`
`Mar. 14, 2000
`
`Sheet 11 of 13
`
`6,037.546
`
`SRL
`(dB)
`
`SRL
`(dB)
`
`
`
`
`
`
`
`
`
`
`
`I I I II
`III III
`III II
`III ||
`II. HI
`IWWII WMM II
`IHEII
`II i II
`I I I II
`
`O. 1
`
`1
`
`10
`Frequency (MHz)
`F.G. 6A
`
`1000
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`I I I II
`I I I II
`|| || || ||
`IIII
`IAIIII
`IWYMMWW II
`IHII
`I I H II
`I I I II
`
`0.1
`
`1
`
`1000
`
`100
`10
`Frequency (MHz)
`FIG. 6B
`
`

`

`U.S. Patent
`
`Mar. 14, 2000
`
`Sheet 12 of 13
`
`6,037.546
`
`SRL
`(dB)
`
`SRL
`(dB)
`
`
`
`
`
`
`
`
`
`
`
`
`
`|| || || ||
`|| ||
`|| ||
`|| || || ||
`IIII
`IWWII
`NW "I'M II
`IHII
`|| || |H| ||
`III II
`
`O. 1
`
`1
`
`1000
`
`100
`10
`Frequency (MHz)
`FIG. 6C
`
`
`
`
`
`
`
`
`
`
`
`I I I II
`I I I II
`I I I II
`IIII
`IIIHIII
`||NYMMM|||
`IIHIII
`|| || iH ||
`I I I II
`
`0.1
`
`1
`
`1000
`
`100
`10
`Frequency (MHz)
`FIG. 6D
`
`

`

`U.S. Patent
`
`Mar. 14, 2000
`
`Sheet 13 of 13
`
`6,037.546
`
`
`
`e
`
`co
`
`w
`
`e
`
`an
`C
`sa'
`
`va
`SS
`O.
`C
`n
`
`?n
`S.
`CN
`SS
`.
`C
`n
`
`U.S. Patent
`
`Mar. 14, 2000
`
`Sheet 13 of 13
`
`6,037,546
`
`- ATTENUATION MEASUREMENTS
`
`FIG. 7
`
`
`
`
`20.7
`
`16.0
`
`21.1
`
`16.3
`
`21.7
`
`16.8
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`1.5
`
`1.5
`
`PAIR #4 (dB)
`
`PAIR #3 (dB)
`
`1.6
`
`PAIR #2 (dB)
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`10.9
`
`9.6
`
`11.1
`
`9.9
`
`8.5
`
`7.5
`
`8.7
`
`7.7
`
`5.8
`
`6.0
`
`11.5
`
`10.2
`
`9.0
`
`8.0
`
`6.2
`
`
`
`
`21.3
`
`16.6
`
`11.3
`
`10.1
`
`8.9
`
`7.9
`
`6.1
`
`1.6
`
`PAIR #1 (dB)
`
`
`
`
`22.0
`
`17.0
`
`11.7
`
`10.4
`
`9.3
`
`8.2
`
`6.5
`
`1.8
`
`CAT 5 MAX (dB) |
`
`
`
`
`100
`
`62.5
`
`31.25
`
`25
`
`20
`
`16
`
`10
`
`0.772
`
`f (MHz)
`
`
`
`
`

`

`1
`SINGLE-JACKETED PLENUM CABLE
`
`RELATED APPLICATIONS
`This application is a Continuation-In-Part of U.S. patent
`application Ser. No. 08/857,018, filed May 15, 1997 now
`abandoned, which is a Continuation-In-Part of U.S. patent
`application Ser. No. 08/640,262, filed Apr. 30, 1996.
`
`FIELD OF THE INVENTION
`
`This invention relates to a communications cable Suitable
`for plenum, riser, and other applications in building Struc
`tures. More particularly, the present invention relates to an
`improved construction for a high-frequency communica
`tions cable that is capable of meeting rigorous burn require
`ments and is electrically stable during operation at Substan
`tially higher temperatures than prior art cables.
`
`15
`
`BACKGROUND OF THE INVENTION
`It is common practice to route communication cables and
`the like for computers, data devices, and alarm Systems
`through plenums in building constructions. If a fire occurs in
`a building which includes plenums or risers, however, the
`non-fire retardant plenum construction would enable the fire
`to spread very rapidly throughout the entire building. Fire
`could travel along cables installed in the plenum, and Smoke
`originating in the plenum could be conveyed to adjacent
`areas of the building.
`A non-plenum rated cable sheath System, which encloses
`a core of insulated copper conductors, and which utilizes
`only a conventional plastic jacket, may not exhibit accept
`able flame spread and Smoke generation properties. AS the
`temperature in Such a cable rises due to a fire, charring of the
`jacket material may occur. If the jacket ruptures, the interior
`of the jacket and the insulation are exposed to elevated
`temperatures. Flammable gases can be generated, propagat
`ing flame and generating Smoke.
`Generally, the National Electrical Code requires that
`power-limited cables in plenums be enclosed in metal con
`duits. This is obviously a very expensive construction due to
`the cost of materials and labor involved in running conduit
`or the like through plenums. The National Electrical Code
`does, however, permit certain exceptions to the requirements
`So long as Such cables for plenum use are tested and
`approved by an independent testing laboratory, Such as the
`Underwriters Laboratory (UL), as having suitably low flame
`Spread and Smoke-producing characteristics. The flame
`Spread and Smoke production characteristics of plenum
`cable are tested and measured per the UL-910 plenum burn
`Standard.
`With plenum cables, in addition to concerns about flam
`mability and Smoke production, the cables must also, of
`course, have Suitable electrical characteristics for the Signals
`intended to be carried by the cables. There are various
`categories of cable, Such as Category 3, Category 4, Cat
`egory 5, etc., with increasing numbers referring to enhanced
`or higher frequency electrical transmission capabilities.
`With Category 5, for example, extremely good electrical
`parameters are required, including low attenuation, Struc
`tural return loSS, and cross-talk values for frequencies up to
`100 MHz. Unfortunately, cable materials which generally
`have the requisite resistance to flammability and Smoke
`production also result in electrical parameters for the cable
`generally not Suitable for the higher transmission rates, Such
`as a Category 5 cable. Specifically, Category 5 plenum
`cables must: (1) pass the UL-910 plenum burn test; (2) pass
`
`25
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`6,037.546
`
`2
`physical property testing Set forth in the UL-444 Standard
`relating to communications cables; and (3) meet the Cat
`egory 5 electrical requirements Such as provided in Elec
`tronic Industries Association specification TIA/EIA-568A.
`Currently, a cable construction which is available and
`which meets these requirements is provided in a configura
`tion which includes fluorinated ethylene propylene (FEP) as
`insulation, with a low-smoke polyvinyl chloride (PVC)
`jacket. Such a cable construction meets the 100 MHz
`frequency operation requirements, and it has been demon
`Strated that Such a cable construction can be Suitable for
`asynchronous transfer mode (ATM) applications.
`Unfortunately, FEP at times may be in short supply. Given
`the manufacturing capacity of FEP producers, only enough
`FEP is currently produced to meet approximately 80 percent
`of the demand for the volume of material required to
`construct high-category cables. Although it could be
`expected that the Supply of FEP will continue to increase, it
`is apparent that the available quantity of FEP may not meet
`the demand for the material for use in plenum cables as the
`domestic market is projected to increase at a rate of approxi
`mately 20 percent per year in the near future, and the
`potential use of Such Category 5 plenum cables in European
`and Scandinavian markets may further increase the demand
`for FEP.
`One current riser cable utilizes a foam/skin insulation.
`The insulation material construction is a foamed, high
`density polyethylene and PVC skin composite. A jacketed
`and Shielded cable of this insulation core can be designed to
`meet the Category 3 electrical and the plenum burn require
`ments. However, developing a Category 5 plenum cable is
`very difficult due to the extreme electrical parameters
`necessary, e.g., attenuation, structural return loss, and cross
`talk values to 100 MHz. Furthermore, this core must pass
`elevated temperature attenuation requirements at 40 C. and
`60° C. The above-mentioned insulation composite with a
`PVC skin will not pass the elevated temperature attenuation
`requirements because the dielectric constant of PVC
`increases with temperature.
`SUMMARY OF THE INVENTION
`It is an advantage of this invention to provide a cable
`construction Suitable for high frequency electrical applica
`tions while at the same time being resistant to burning.
`A more specific advantage of this invention to provide a
`cable design that meets Category 5 or higher electrical
`parameters, including elevated temperature attenuation
`requirements, while at the Same time Satisfying the burn
`rating Standards for plenum cable.
`It is an additional advantage of this invention to provide
`a cable construction which meets the electrical and burn
`rating requirements and additionally meets various physical
`requirements Such as cold bend, room temperature and aged
`tensile Strength, elongation, and the like, required for ple
`num cables.
`It is another advantage of this invention to provide Such
`a cable construction meeting the above requirements, which
`does not utilize FEP, and which is Suitable for 100 MHz
`applications.
`A further advantage of the present invention is that it
`provides a cable construction having an Outer jacket con
`Struction that exhibits electrically stable characteristics at
`Substantially high temperatures, relative to the temperature
`requirements of currently available plenum cables.
`The above and other advantages of the present invention
`may be carried out in one form by an improved communi
`
`

`

`3
`cations cable for use in plenum applications. The cable may
`include a plurality of conductors, each being individually
`enclosed by a Substantially pure high density polyethylene
`(HDPE) insulating material, a polyvinylidene fluoride
`(PVDF) outerjacket surrounding the plurality of conductors,
`and an air gap formed between the conductors and the outer
`jacket. The conductors, the insulation material, the air gap,
`and the outer jacket are cooperatively configured Such that
`the cable passes the UL-910 plenum burn test and such that
`the cable meets the Category 5 electrical requirements Set
`forth in the TIA/EIA 568A Standard.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`A more complete understanding of the present invention
`may be derived by referring to the detailed description and
`claims when considered in connection with the Figures,
`where like reference numbers refer to Similar elements
`throughout the Figures, and:
`FIG. 1 is an elevation of a cable construction in accor
`dance with the present invention with a portion of the outer
`jacket broken away for illustrative purposes,
`FIG. 1A is a croSS Sectional view of a cable arrangement
`in accordance with the present invention;
`FIG. 2 is a croSS Sectional view of a cable construction in
`accordance with the present invention in which a plurality of
`cable cores are enclosed as a composite in an Outer jacket;
`FIG. 3 is a cross-section of one of the conductors in a
`twisted wire pair of the cable shown in FIG. 2;
`FIGS. 4A-4F are graphs of experimental near end
`crosstalk (NEXT) test results for a cable configured in
`accordance with the present invention;
`FIG. 4G is a table of experimental test data points taken
`from the graphs of FIGS. 4A-4F;
`FIGS. 5A-5D are graphs of experimental NEXT power
`Sum test results for a cable configured in accordance with the
`present invention;
`FIG. 5E is a table of experimental test data points taken
`from the graphs of FIGS. 5A-5D;
`FIGS. 6A-6D are graphs of experimental structural return
`loss (SRL) test results for a cable configured in accordance
`with the present invention; and
`FIG. 7 is a table of experimental attenuation test results
`for a cable configured in accordance with the present inven
`tion.
`
`DETAILED DESCRIPTION OF PREFERRED
`EXEMPLARY EMBODIMENTS
`As noted, FEP insulation with a low-smoke PVC jacket
`meets Category 5 electrical requirements and the applicable
`physical and burn property tests for plenum rated cable. The
`TIA/EIA 568-A standard sets forth the electrical require
`ments for Category 5 cable. In addition to other criteria,
`Category 5 cable must meet or exceed certain attenuation,
`return loSS, and croSStalk requirements. For example, Cat
`egory 5 cable must be configured Such that any given
`conductor pair has an attenuation, in dB per 100 meters,
`measured at or corrected to a temperature of 20° C., within
`a frequency range of f=0.772 MHz to f=100 MHz, deter
`mined by the formula:
`ATTN(f)s 1.967sqrt (f)+0.023f-0.050/sqrt(f).
`In addition, Category 5 cable must be configured Such that
`any given conductor pair has a structural return loss (SRL)
`in decibels, for a length of 100 meters or longer, within a
`
`15
`
`25
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`6,037.546
`
`4
`frequency range of f=20 MHz to f=100 MHz, determined
`by the formula:
`SRL(f)223-10 log(f/20).
`For frequencies between 0.772 and 20 MHz, the SRL must
`be at least 23 dB. If the cable does not meet these (and other)
`performance criteria, then it may not be properly classified
`as Category 5 cable. The entire content of the TIA/EIA
`568-A standard is incorporated by reference herein.
`While the electrical and physical property requirements
`for Category 5 and higher cable could be met with other
`plastics Such as polyolefins or modified polyolefins, the
`plenum burn requirements, such as the UL-910 plenum burn
`test, could not be met Since polyolefins burn readily. If a
`polyolefin material was Smoke Suppressed and flame
`retarded, the ingredients necessary for flame protection
`would detract from the necessary electrical values of the
`polyolefin material, and would also detract from the physical
`property attributes of the material.
`The CMP or plenum burn test is a severe test. The test
`takes place in a closed horizontal fixture or tunnel, with the
`ignition flame source being a 300,000 BTU/hour methane
`flame with a high heat flux, and a 240 foot/minute air draft.
`The test lasts 20 minutes, and the cable is stretched side to
`Side acroSS a 12 inch wide, 25 foot long wire mesh rack in
`the tunnel. To pass this test, flame spread must not exceed
`5.0 feet after the initial 4.5 foot flame source; Smoke
`generation must not exceed a peak optical density of 0.5
`(33% light transmission); and the average optical density
`must not exceed 0.15 (70% light transmission). The purpose
`of this optical Smoke density parameter is to allow a perSon
`trapped in a fire the ability to see exit Signs as well as
`visually discern a route or means of escape. The entire
`content of the UL-910 standard is incorporated by reference
`herein.
`FIG. 1 shows an elevation of a cable 5 in accordance with
`a preferred embodiment of the present invention. Cable 5
`meets Category 5 electrical requirements and the applicable
`burn, Smoke generation, and physical property requirements
`for plenum-rated cable without the use of FEP Referring
`now to FIG. 1, there is shown cable 5, which is Suitable for
`use in building plenums and the like. In the Specific example
`shown in FIG. 1, the cable 5 is illustrated as having four
`twisted pairs of transmission media, referred to as twisted
`pairs and indicated by reference numerals 6, 7, 8 and 9,
`forming what is generally referred to as the cable core. In
`accordance with this embodiment of the invention, the
`twisted pairs 6-9 have a polyolefin primary insulation,
`which has good electrical characteristics even though it
`readily burns. In a specific embodiment of the present
`invention, a foam/skin high density polyethylene (HDPE) is
`used for the primary insulation, which has the requisite
`electrical characteristics for high frequency cable applica
`tions.
`In order to provide the required resistance to burning, the
`cable 5 is provided with an outer jacket 11 which is highly
`resistant to burning. Thermoplastic halogenated polymers
`have been found to be Suitable materials, particularly ther
`moplastic fluorocarbon polymers. In a specific embodiment
`of the invention, polyvinylidene fluoride (PVDF) has been
`found to be quite Suitable in terms of providing adequate
`flame and burn resistance to meet the applicable Standards.
`A cable construction consisting of only the core of twisted
`pairs with polyolefin insulation Surrounded by ajacket of
`conventionally extruded thermoplastic fluorocarbon poly
`mer (such as solid PVDF) meets the applicable burn
`Standards, but does not meet the high frequency electrical
`
`

`

`S
`Standards for Category 5 cable. Specifically, the less than
`optimal electrical characteristics of a conventionally manu
`factured fluorocarbon polymer jacket, and its proximity to
`the twisted pairs, degrade the cable's electrical characteris
`tics.
`In accordance with one embodiment of the present
`invention, a single outer foamed PVDF jacket 11 may be
`employed by cable 5 without any intermediate material
`between the cable core and the outer PVDF jacket 11. As
`shown in FIG. 1A, the inner Surface of outer jacket 11 is
`adjacent and proximate to conductor core 15 and the outer
`Surface of Outer jacket 11 is exposed. The particular foam
`construction of the outer PVDF jacket 11 Suitably enhances
`the electrical characteristics of the PVDF material, which
`typically exhibits very poor dielectric constant and dissipa
`tion factor values in a Substantially Solid or unfoamed State.
`Although not shown in FIG. 1, cable 5 may include a
`shield located within outer jacket 11. Preferably, such a
`Shield Substantially Surrounds the cable core and is config
`ured to enhance the electrical performance of the cable core.
`For example, the Shield may be configured to protect the
`cable core from extraneous RF or electromagnetic fields and
`signals. The shield may be formed from a metallic foil, such
`as aluminum or copper, and may be constructed according to
`any number of conventional methodologies. Such shields
`are known to those skilled in the art, and need not be
`described in detail herein.
`FIG. 1A is a cross sectional view of cable 5 configured in
`accordance with a particularly preferred aspect of the
`present invention. The individual conductors 14 that form
`twisted pairs 6-9 are shown in a typical core arrangement
`proximate the center of cable 5. In accordance with the
`present invention, the composition and dimensions of the
`various materials are configured to enable cable 5 (and/or
`the individual twisted pairs) to pass the UL-910 plenum burn
`test, to meet the UL-444 physical requirements, and to meet
`the electrical specification for Category 5 cable. Prior art
`cables utilizing an HDPE primary insulation material and a
`PVDF outer jacket material do not meet each of these
`requirements.
`A conductor core 15 (depicted in dashed lines) includes
`conductors 14, which are preferably arranged as four twisted
`pairs 6-9. In turn, the four twisted pairs 6-9 are twisted
`together into conductor core 15. In the preferred exemplary
`embodiment, conductor core 15 has a twist length of
`approximately six inches, i.e., the four twisted pairs 6-9 are
`twisted 360 degrees over a length of six inches. For the sake
`of convenience, conductor core 15 is depicted as having a
`circular periphery; it should be appreciated that conductor
`core 15 may be alternately configured in any Suitable shape
`according to the Specific application and/or according to the
`particular manufacturing technique. Indeed, in alternate
`embodiments, a core wrap material (not shown) may be
`utilized to physically bind or wrap conductors 14 together.
`Furthermore, although the twisted pairs 6-9 are shown
`Spaced apart in FIG. 1A, a practical implementation of cable
`5 may have conductorS 14 arranged in a more compact
`manner. Cable 5 preferably includes an air gap 16 located
`between conductor core 15 and outer jacket 11. In the
`preferred embodiment, air gap 16 is formed during extrusion
`of outer jacket 11 (described in more detail below). The
`presence of air gap 16 enables the twisted pairs 6-9 (and,
`consequently, cable 5) to pass the strict Category 5 electrical
`requirements even though outer jacket 11 is formed from
`PVDF, which has very poor electrical characteristics.
`The inventors have discovered that the use of air gap 16
`enhances the electrical performance of cable 5 Such that
`
`15
`
`25
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`6,037.546
`
`6
`foaming of outer PVDF jacket 11 is not always necessary. In
`other words, a Suitable Category 5 plenum cable may
`employ a solid PVDF outer jacket 11, air gap 16, and the
`foam/skin HDPE primary insulation. Such an arrangement
`need not employ an innerjacket or any intermediate material
`between outer jacket 11 and conductor core 15. Of course,
`the use of a foamed PVDF outer jacket 11 may be desirable
`for enhanced applications that require electrical perfor
`mance above and beyond the minimum requirements of
`Category 5 cable.
`Although the “wall' thickness of air gap 16 may vary
`from application to application, it is preferably between
`about 5 mils and 15 mils thick. In one preferred Category 5
`plenum cable embodiment, air gap 16 is approximately 10
`mils (0.010") thick. The preferred thickness of air gap 16
`strikes a balance by enabling cable 5 to meet both the
`Category 5 electrical requirements and the UL-444 physical
`requirements. For example, the Structural integrity of cable
`5 may Suffer if air gap 16 is too large, while the dimension
`of air gap 16 must be appropriately sized Such that conductor
`core 15 remains in place within outer jacket 11.
`Furthermore, the maximum thickness of air gap 16 is limited
`for practical Category 5 cables, which must have an overall
`outer diameter of less than 0.25". On the other hand, the
`minimum thickness of air gap 16 is limited for practical
`Category 5 cables because as the thickness of air gap 16
`decreases, the electrical characteristics of cable 5 degrade.
`Consequently, if the thickness of air gap 16 is too Small, then
`cable 5 may not meet the requisite Category 5 electrical
`performance criteria.
`Although air gap 16 is preferably formed during the
`extrusion of outer jacket 11 around conductor core 15, any
`Suitable technique may be employed. In contrast to conven
`tional communications cables in which the Outer and/or
`intermediate jacket is Snugly drawn down to Surround the
`conductor core, air gap 16 is intentionally formed in cable 5
`between outer jacket 11 and conductor core 15. Drawing
`down of intermediate or outer jackets is generally performed
`during the manufacture of prior art cables to ensure that the
`conductors remain in place and are adequately insulated;
`drawing down of extruded jackets is a relatively easy Step
`that naturally occurs during the extrusion and quenching
`proceSSeS.
`As described above, the preferred embodiment only
`includes conductor core 15, air gap 16, and outer jacket 11
`(foamed or unfoamed PVDF). In accordance with one
`preferred embodiment, the wall thickness of outer jacket 11
`is approximately 22 mils. This preferred thickness, along
`with air gap 16, enables cable 5 to be within the current
`maximum outer diameter for Category 5 cable (0.25"). The
`particular configuration of conductors 14, air gap 16, and
`outer jacket 11 (i.e., the specific composition of insulation
`and jacket materials and the Specific dimensions of the cable
`components) enables cable 5 to meet the Category 5 elec
`trical criteria while passing the UL-444 physical tests and
`the UL-910 plenum burn test.
`Referring now to FIG. 2, there is shown a construction of
`a cable 10 in accordance with this invention, Suitable for use
`in building plenums, and the like, e.g., indoor/outdoor rated
`cable, in which a plurality of cable cores are enclosed within
`a single foamed PVDF outer jacket. In FIG. 2, the cable 10
`comprises one or more wrapped cables 20, each of which
`may include a core 22. The core 22 may be one which is
`Suitable for use in data, computer, alarm, and other Signaling
`networks as well as communications. The core 22 is the
`transmission medium and is shown in FIG. 2 as comprising
`one or more twisted wire pairs, the pairs of which are
`
`

`

`7
`referred to in FIG. 2 by reference numerals 24, 26, 28 and
`30. Cables which are used in plenums may include 25 or
`more conductor pairs, although Some cables include as few
`as Six, four, two or even a Single conductor pair Such as
`shown in FIG. 1. In the exemplary embodiment shown in
`FIG. 2, each of the cores 22 comprise four twisted conductor
`pairs, identified in FIG. 2 with reference numerals 24, 26, 28
`and 30.
`As shown in FIG. 2, each of the cables 20 preferably
`utilizes a foamed PVDF innerjacket configured identified by
`reference numeral23. The innerjacket 23 may be configured
`as described more fully hereafter. Those skilled in the art
`will appreciate that the inner jacket 23 is not a requirement
`of the present invention, and that any Suitable wrapping
`element known to those skilled in the art may be employed
`by cable 10. Furthermore, the particular material utilized as
`the i