Electricity: conductors and insulators – Conduits – cables or conductors – Insulated
Reexamination Certificate
2000-08-29
2001-10-16
Nguyen, Chau N. (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Insulated
C174S1130AS, C174S115000
Reexamination Certificate
active
06303867
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to high-speed data communications cables containing a plurality of transmission media. More particularly it relates to cables having a cable jacket in which each of the plurality of transmission media is separated from the other transmission media, by a plurality of channels, where adjacent channels are offset from one another to increase the distance between the respective transmission media within the adjacent channels, thereby reducing the level of coupling of cross-talk signal interference between the transmission media within the cable jacket.
2. Related Art
High speed data communications cables in current use include pairs of wire twisted together forming a balanced transmission line. Such pairs of wire are referred to as twisted pairs.
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 Association (EIA) have defined standards for crosstalk in a data communications cable including: TIA/EIA-568-A, published Oct. 24, 1995; TIA/EIA 568-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.
In twisted pairs, the length of a complete twist between the twisted pairs is known as the twist lay. The direction of the twist is known as the twist direction. If adjacent twisted pairs have the same twist lay and/or twist direction, they will tend to lie more closely together within a cable than if they have different twist lays and/or twist directions. Thus, compared to twisted pairs having different twist lays and/or twist directions, adjacent twisted pairs having the same twist lay and twist direction have a reduced center-to-center distance, and longer parallel run. Therefore, the level of crosstalk tends to be higher between the twisted pairs having the same twist lay and/or twist direction when compared to other twisted pairs having different twist lays and/or twist directions. Therefore, twisted pairs within a cable are sometimes given unique twist lays and twist directions when compared to other adjacent twisted pairs within the cable. The unique twist lay and twist direction serve to decrease the level of crosstalk between the adjacent twisted pairs within the cable.
Shielded cable, although exhibiting better crosstalk isolation, is more difficult and time consuming to install and terminate and is therefore more expensive per installation. Shielded conductors are generally terminated using special tools, devices and techniques adapted for the job.
One popular cable type is Unshielded Twisted Pair (UTP) cable. Because it does not include shielded conductors, UTP cable is preferred by installers and plant managers, as it is easily installed and terminated. However, UTP cable typically fails to achieve the level crosstalk isolation required by state of the art transmission systems, even when varying pair lays and twist directions are used.
Another crosstalk requirement known as “alien crosstalk” is the amount of signal coupling or interference between adjacent or stacked cables. In particular, when the cable are adjacently disposed or disposed one on top of another, there is typically crosstalk between the twisted pairs in each cable. For example, in adjacently disposed cables having a substantially flat configuration, the twisted pairs disposed at one end of each adjacently disposed cable will be in close proximity and will tend to have alien crosstalk that may not be acceptable for state of the art transmission systems.
What is needed therefore is a high-speed data communications cable having a reduced level of cross-talk interference between adjacent twisted pairs within the cable and having a reduced level of alien crosstalk between the twisted pairs in adjacent or stacked cables.
SUMMARY OF THE INVENTION
The present invention provides a data cable having a lower value of cross-talk between adjacent twisted pairs within a cable and a higher level of isolation when compared to conventional cables. In addition, the cable has a lower value of alien crosstalk between similar adjacently disposed or stacked cables of the invention. These and other advantages are accomplished by the disclosed cable arrangements.
According to one embodiment, a data communications cable includes a cable jacket having a plurality of inwardly extending projections defining three longitudinal channels within the cable extending along a length of the telecommunications cable. Each longitudinal channel contains at least one transmission medium. Two of the longitudinal channels are disposed at approximately a same point with respect to a reference line that transverses the cable, the second longitudinal channel is spaced apart from the references line by one of the plurality of inwardly extending projections, thus, increasing a center-to-center distance between the transmission media in adjacent longitudinal channels.
The inwardly extending projection may also be tacked together to seal each of the longitudinal channels. Alternatively, some of the plurality of inwardly extending projections may be tacked together to isolate some of the channels.
The telecommunications cable may also be formed with a desired form factor ratio of a width of the cable to a height of the cable over a range between 1.25 and 2.5. Preferably, the telecommunications cable has a form factor ratio in the range of 1.5 to 2.0.
The cable jacket may also be formed with a number of different arrangements to increase a center-to-center distance of stacked cables. In one embodiment, the jacket may be formed with different thicknesses on different portions of the cable jacket. In an alternative embodiment, the cable jacket may be formed with outwardly extending protrusions.
Another embodiment of the telecommunications cable includes a cable jacket formed having a plurality of inwardly extending projections defining a first and second plurality of substantially parallel longitudinal channels within the cable. Each longitudinal channel contains at least one transmission medium. The first plurality of substantially parallel longitudinal channels are at approximately the same point with respect to a reference line that transverses the cable. The second plurality of substantially parallel longitudinal channels are spaced apart from the reference line by some of the inwardly extending projections. Thus, the corresponding transmission media within the first plurality of channels is spaced apart from the corresponding transmission media in the second plurality of channels.
A method for manufacturing a cable corresponding to the invention includes providing a cable jacket having inwardly extending projections, extending from an inner surface of the cable jacket and having inner ends that define a plurality of substantially parallel longitudinal channels within the cable jacket, with adjacent longitudinal channels being offset from one another. Passing a plurality of twisted pairs of insulated conductors through a die which aligns the plurality of twisted pairs of insulated conductors in a predetermined spatial relationship. Inserting each of the plurality of twisted pairs of insulated conductors within a corresponding one of the p
Clark William
Consalvo Kenneth
Dellagala Joseph
Cable Design Technologies, Inc.
Nguyen Chau N.
Wolfe, Greenfield & Sacks, P.C.
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