Low loss data cable

Details Low loss data cable Low loss data cable

1999-08-06

2001-04-03

Kincaid, Kristine (Department: 2831)

Electricity: conductors and insulators

Conduits, cables or conductors

Insulated

C174S1130AS

Reexamination Certificate

active

06211467

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to data cables which comprise braided conductor groups that are discretely configured with respect to one another.
BACKGROUND OF THE INVENTION
For the past decade, the popularity of IEEE 802.3 (Ethernet) networking technology and its technique for transmitting data signals over unshielded twisted pair wiring (UTP) has been the key driver defining cable performance parameters. This technology, however, was originally designed to allow transmission rates of 10 Megabits per second. During the early 1990s, the Ethernet networking technology was expanded to speeds of 100 Megabits per second over UTP.
Today, with the popularity of Internet and more powerful application software, users are demanding more bandwidth from their local area network (LAN). In order to meet such demands, a networking platform for 1000 Megabits per second transmission has been developed.
However, because the same basic principals that were proposed for operation at 10 Mbps were followed for production of the 1000 Mbps platform, this new design has become extremely complex and expensive. The new design has also become highly sensitive to cable parameters such as return loss, attenuation, crosstalk, ACR, delay skew, far end crosstalk and impedance.
To overcome these problems, new networking platforms and standards are being developed to be backwards-compatible with existing Ethernet systems. Systems incorporating these new standards employ a new transmission technology making them more robust while using less complex circuitry, yielding a more economical solution. The transmission technology used by these new systems is Pseudo Emitter Coupled Logic (PECL).
One system that utilizes the above-mentioned PECL transmission technology employs a high impedance output load along with PECL to produce a low power signal that makes the system virtually immune to near-end crosstalk or far-end crosstalk. However, because the system employs a low power input signal, it is extremely sensitive to attenuation and input impedance smoothness. The system also uses a low level encoding scheme, making it necessary for the nyquist (carrier) frequency to exceed 100 MHz. The actual nyquist frequency in the WideBand 1 Gb per second system is 167 MHz.
In light of the deficiencies of systems described above, along with their associated wiring technology, it is desirable to provide a simple and relatively inexpensive low loss data cable. It is also desirable to provide a low loss data cable that can be used in data networking systems, the data cable being less sensitive to cable parameters such as return loss, attenuation, crosstalk, ACR, delay skew, far end crosstalk and impedance, relative to the existing data cables.
Cabling standards organizations and developers seem to focus on developing products to enhance Ethernet and do not appear to be concerned about open architecture. Thus, it is desirable to incorporate a design of true open architecture, thereby providing maximum available bandwidth for all systems operations. This is necessary, given the fact that Ethernet technology was originally designed based on transmission rates of 10 Mbps and has already been pushed upward by a factor of 100 times. As a result, it is only a matter of time before a new high speed networking technology platform will have to be established to achieve improved data rates and effectively network high speed terabit operating equipment.
SUMMARY OF THE INVENTION
A low loss data cable of the present invention includes a plurality of conductor pairs combined to form a core. Each conductor pair is defined as coupled braided conductors where each conductor encircles its coupled conductor. Each conductor encircling is defined as a pair lay length. A first insulating material layer separately insulates each of the conductors. A second insulating material layer surrounds a core which includes the conductor pairs in a twist formation where each of the conductor pairs encircles a center gap separating all of the conductor pairs. When each conductor pair encircling is defined as a core lay length, the pair lay length of each of said conductor pairs is no greater than about one third of the core lay length. In a preferred embodiment of the invention, the pair lay length of each of the conductor pairs is less than about one fourth of the core lay length.
Each of the conductors is at least respectively about 92% centered in the first insulating material. Furthermore, the core is at least about 92% centered in the second insulating material.
The first insulating material has a dielectric constant of less than about 2.5, and less than about 2.3 in a preferred embodiment. The first insulating material includes pure fluorinated perfluoethylene polypropylene, and polyethylene having a minimal amount of copper added thereto, which is sufficient to provide a stabilizing effect. The first insulating material also has a loss tangent of less than about 0.009, and may alternatively comprises at least one of polyfluoroalkoxy, TFE/perfluoromethylvinylether, and polytetrafluoroethylene. The second insulating material has a dielectric constant no greater than 3.5, and less than about 3.2 in a preferred embodiment.
Also, in a preferred embodiment of the invention the center gap consists of air. Alternatively, the center gap can include a filler made of a foam or solid material, having a dielectric constant no greater than the dielectric constant of the first or second insulating material. The filler can include at least one of polypropylene, polyethylene, fluorinated ethylene-propylene, polyfouoroalkoxy TFE/perfluoromethylvinylether, ethylene chlorotrifluoro-ethylene, polyvinyl chloride, low smoke zero halogen, and thermoplastic elastomer.
Each of the conductors in the present invention has a maximum size of 22 AWG. Furthermore, the cable has an outer diameter no greater than 0.25 inches.
A method of manufacturing a low loss data cable according to the present invention includes the following steps. First, insulating a first conductor within a first dielectric material so the conductor is at least about 92% centered in the first dielectric material. Second, a predetermined amount of balanced tension is applied on the conductor and on a second conductor insulated as described above, while braiding the first and second conductors to encircle each other as a first pair, where each encircling is defined as a pair lay length. Third, a predetermined amount of balanced tension is applied on the first pair of conductors and on a second, third, and fourth pair of conductors provided according to above steps, while braiding the first, second, third, and fourth pairs to encircle a center gap. The center gap separates all of the pairs from each other, each pair encircling being defined as a core lay length. Fourth, the first, second, third, and fourth pairs are insulated together as a core within a second dielectric material so that the core is at least about 92% centered in the second dielectric material. The pair lay length of each of the pairs is no greater than about one third of the core lay length.
As explained above, in a preferred embodiment of the invention the pair lay length of each of the pairs is less than about one fourth of the core lay length.
The step of insulating a conductor should be performed while ensuring moisture removal and maintaining dryness in order to prevent formation of pores in the conductor and/or the insulating material.


REFERENCES:
patent: 3737557 (1973-06-01), Verne et al.
patent: 5574250 (1996-11-01), Hardie et al.
patent: 5600097 (1997-02-01), Bleich et al.
patent: 5952607 (1999-09-01), Friesen et al.

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