|Publication number||USRE42266 E1|
|Application number||US 12/707,985|
|Publication date||Apr 5, 2011|
|Filing date||Feb 18, 2010|
|Priority date||Mar 28, 2005|
|Also published as||CA2603101A1, CA2603101C, CN100553037C, CN101176235A, EP1872440A2, EP1872440A4, EP1872440B1, EP2592631A1, US7332676, US20070037419, WO2006105166A2, WO2006105166A3|
|Publication number||12707985, 707985, US RE42266 E1, US RE42266E1, US-E1-RE42266, USRE42266 E1, USRE42266E1|
|Original Assignee||Leviton Manufacturing Co., Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (15), Referenced by (5), Classifications (5), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application claims priority benefit of provisional application Ser. No. 60/665,969 filed Mar. 28, 2005.
1. Field of the Invention
The present invention is generally related to cable for transmitting signals, and more particularly related to reduction of crosstalk experienced between the signals.
2. Description of the Related Art
A metal based signal cable for transmitting information across computer networks, generally have a plurality of wire pairs (such as pairs of copper wires) so that a plurality of signals, each signal using a separate wire pair, can be transmitted over the cable at any given time. Having many wire pairs in a cable can have advantages, such as increased data capacity, but as signal frequency used for the signals is increased to also increase data capacity, a disadvantage becomes more evident. As signal frequency increases, the individual signals tend to increasingly interfere with one another due to crosstalk due to the close proximity of the wire pairs. Twisting the two wires of each pair with each other helps considerably to reduce crosstalk, but is not sufficient as signal frequency increases.
Other conventional approaches can be also used to help reduce crosstalk such as using physical spacing within the cable to physically separate and isolate the individual twisted wire pairs from one another to a certain degree. Drawbacks from using additional physical spacing include increasing cable diameter and decreasing cable flexibility.
Another conventional approach is to shield the twisted pairs as represented by the shield twisted pair cable 10 depicted in
An external sheath 22 covers the conductive shield 16 and the drain wire 18. The conductive shield 16 is typically connected to a connector shell (not shown) on each cable end usually through use of the drain wire 18. Connecting the conductive shield 16 to the connector shell can be problematic due to additional complexity of installation, added cable stiffness, special connectors required, and the necessity for an electrical ground, available at both ends of the cable 10. Furthermore, improper connection of the conductive shield 16 can reduce or eliminate the effectiveness of the conductive shield and also can raise safely issues dye to improper grounding of the drain wire 18. In some improper installations, the conventional continuous shielding of a cable segment is not connected on one or both ends. Unconnected ends of conventional shielding can give rise to undesired resonances related to the un-terminated shield length which enhances undesired external interference and crosstalk at those resonant frequencies
Although conventional approaches have been adequate for reducing crosstalk for signals having lower frequencies, unfortunately, crosstalk remains a problem for signals having higher frequencies.
As discussed herein, implementations of a discontinuous cable shield system and method include a shield having a multitude of separated shield segments dispersed along a length of a cable to reduce crosstalk between signals being transmitted an twisted wire pairs of a cable. Implementations include a cable comprising a plurality of differential transmission lines extending along a longitudinal direction for a cable length, and a plurality of conductive shield segments, each shield segment extending longitudinally along a portion of the cable length, each shield segment being in electrical isolation from all other of the plurality of shield segments, and each shield segment at least partially extending about the plurality of the differential transmission lines.
A first implementation 100 of the discontinuous cable shield system is shown in
The separated shield segments 108 serve as an incomplete, patch-worked, discontinuous, ‘granulated’ or otherwise perforated shield that has effectiveness when applied as shielding within the near-field zone around differential transmission lines such as the twisted wire pairs 102. This shield ‘granulation’ may have advantage in safety over a long-continuous un-grounded conventional shield, since it would block a fault emanating from a distance along the cable.
Various shapes, overlapping and gaps of the separated shield segments 108 may have useful benefit, possibly coupling mode suppression or enhancement, fault interruption (fusing), and attractive patterns/logos. In some implementations, a dimensional limit of shielding usefulness may be related to the greater of twist rate pitch or differential pair spacing of the twisted wire pairs 102 since the shielding tends to average the positive and negative electrostatic near-field emissions from the twisted wire pairs. Magnetic emissions may be averaged in another manner; only partially blocked by eddy currents countering the emitted near field related to each of the twisted wire pairs 102.
Implementations serve to avoid or reduce external field interference with inner-cable circuits, channels, or transmission lines. Reciprocity can apply to emissions avoidance as well. Implementations allow for installation without having to consider a shield when terminating differential cable pairs. Safety standards usually require safe grounding or insulation of such large conductive parts, however this is often ignored in actuality so the implementations may have a practical safety benefit. Implementations may also help to avoid negative effects of ground loops, such as associated with spark gaps in conventional cable shields for purpose of isolating all but transients.
Implementations involve differential transmissions lines, such as the twisted wire pairs 102. The twisted wire pairs 102 can be typically balanced having an equal and opposite signal on each wire. Use of twisted (balanced) pairs of wires mitigates loss of geometric co-axiality that results in radiation, particularly near-field radiation. Implementations serve to lessen crosstalk, such as unwanted communications and other interference by electrostatic, magnetic or electromagnetic means between closely routed pairs. Crosstalk can include alien crosstalk between separately sheathed wires.
Some implementations address requirements under TIA/EIA Commercial Building Telecommunications Cabling Standards such as those applied to balanced twisted pair cable including Category 5, 5e, 6 and augmented 6. Other implementations address other standards or requirements. Some implementations can serve to modify unshielded twisted pair cable having an outer insulating jacket covering usually four pairs of unshielded twisted wire pairs. Modifications can include converting to a form of shielded twisted pair cable having a single shield encompassing all four pairs under an outer insulating sheath. Some effects involved with implementations involve near field that is typically at less than sub-wavelength measurement radii where the angular radiation pattern from a source significantly varies from that at infinite radius.
Crosstalk between the various twisted wire pairs 102 and other interference originating from outside of the cable can be reduced to various degrees based upon size and shape of the separated shield segments 108. For instance, a more irregular pattern for the segmentation gaps 110 can assist in reduction of alien crosstalk and other interference whereas a more regular and aligned patterns for the segmentation gaps may be less effective in reducing alien crosstalk.
Use of the separated shield segments 108 can help to protect from crosstalk and other interference originating both internally and externally to the cable. This electromagnetic based crosstalk and other interference can be further reduced by use of irregular patterns for the segmentation gaps 110 so that the separated shield segments 108 are sized differently and consequently do not interact the same way with the same electromagnetic frequencies. Varying how the separated shield segments 108 interact with various electromagnetic frequencies helps to avoid having a particular electromagnetic frequency that somehow resonates with a majority of the separated shield segments to cause crosstalk associated with the resonant electromagnetic frequency.
The separated shield segments 108 can also be sized so that any potential resonant frequency is far higher than the operational frequencies used for signals being transmitted by the twisted wire pairs 132. Additionally a combination of small size or randomized size and irregular shape for the separated shield segments 108 could further offset tendencies for resonant frequencies or at least offset a tendency for a predominant resonant frequency to cause crosstalk. Some of the separated shield segments 108 could also be made of various compositions of conductive and resistive materials to vary how the separated shield segments interact with potentially interfering electromagnetic waves.
Short lengths of the separated shield segments 108 can move related resonances to higher frequencies, above the highest frequency of interest as used for cable data signaling. Selection of optimal length, shape and material loss factors related to the separated shield segments 108 and possible materials in the insulation 106 or otherwise between the separated shield segments in the segmented gaps 110 can serve to eliminate need for termination of a shielding and can provide enhanced shielding aspects. Consequential interruption of ground loops, such as undesired shield currents and noise caused by differences in potential at conventional grounding points at the ends of the cable can avoid introduction of interference onto the twisted wire pairs 102 that would otherwise be emanating from noise induced by conventional shield ground loop current. As mentioned elsewhere, higher resonances can be mitigated, softened, dulled, and de-Q'ed by shaping the separated shield segments 108 and in some implementations by adding electrically lossy medium surrounding or within the separated shield segments.
For instance, a resistive lossy component could be added to the segmentation gaps 110 to dissipate energy that would otherwise cause crosstalk. Further variations to the separated shield segments 108 could include incorporating slits into the separated shield segments. Also, the separated shield segments 108 could vary in thickness amongst one another or individual separated shield segments could have irregular thickness to further help offset tendencies for frequency resonance and resultant crosstalk.
Further implementations can position between layers of the insulation 106 other layers of various shapes of the separated shield segments 108. In these layered implementations, portions of some of the separated shield segments 108 could be positioned on top of portions of other of the separated shield segments to vary in another dimension how the separated shield segments are effectively shaped and sized.
The separated shield segments 108 can also allow for enhanced cable flexibility depending in part on how the segmentation gaps 110 are shaped. Furthermore, the implementations need not include a drain wire so can also avoid associated issues with such. Some implementations can further include use of conventional separators to physically separate each of the twist wire pairs 102 from one another as discussed above in addition to using the separated shield segments 108. Other variations can include having the separated shield segments 108 positioned directly upon the twisted wire pairs 102 or on the outer cable sheath 112.
The separated shield segments 108 can be formed by various methods including use of adhesive on foil, foil applied to a heated plastic sheath such as immediately after extrusion of the plastic sheath, molten metalized spray upon masking elements, molten metalized spray on irregular surfaces whereupon excessive metal in raised areas are subsequently removed, use of conductive ink deposited by controlled jet or by pad transfer process.
A second implementation 120 of the discontinuous cable shield system is shown in
A third implementation 130 of the discontinuous cable shield system is shown in
A fourth implementation 140 of the discontinuous cable shield system is shown in
A fifth implementation 150 of the discontinuous cable shield system is shown in FIG. 8 and
A sixth implementation 160 of the discontinuous cable shield system is shown in FIG. 10 and
A seventh implementation 170 of the discontinuous cable shield system is shown in
An eighth implementation 180 of the discontinuous cable shield system is shown in
A ninth implementation 190 of the discontinuous cable shield system is shown in
A tenth implementation 200 of the discontinuous cable shield system is shown in
A eleventh implementation 210 of the discontinuous cable shield system is shown in
A twelfth implementation 220 of the discontinuous cable shield system is shown in
A thirteenth implementation 230 of the discontinuous cable shield system is shown in
A fourteenth implementation 240 of the discontinuous cable shield system is shown in
A fifteenth implementation 250 of the discontinuous cable shield system is shown in
A sixteenth implementation 260 of the discontinuous cable shield system is shown in
A seventeenth implementation 270 of the discontinuous cable shield system is shown in FIG. 22 and
A eighteenth implementation 280 of the discontinuous cable shield system is shown in
A nineteenth implementation 290 of the discontinuous cable shield system is shown in
A twentieth implementation 300 of the discontinuous cable shield system is shown in
A twenty-first implementation 310 of the discontinuous cable shield system is shown in FIG. 27 and in
A twenty-second implementation 320 of the discontinuous cable shield system is shown in FIG. 29 and
A twenty-third implementation 330 of the discontinuous cable shield system is shown in FIG. 31 and
A twenty-fourth implementation 340 of the discontinuous cable shield system is shown in
A twenty-fifth implementation 350 of the discontinuous cable shield system is shown in
A twenty-sixth implementation 360 of the discontinuous cable shield system is shown in
A twenty-seventh implementation 370 of the discontinuous cable shield system is shown in
A twenty-eighth implementation 380 of the discontinuous cable shield system is shown in
A twenty-ninth implementation 390 of the discontinuous cable shield system is shown in
A thirtieth implementation 400 of the discontinuous cable shield system is shown in
A thirty-first implementation 410 of the discontinuous cable shield system is shown in
A thirty-second implementation 420 of the discontinuous cable shield system is shown in
A thirty-third implementation 430 of the discontinuous cable shield system is shown in
A thirty-fourth implementation 440 of the discontinuous cable shield system is shown in
From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.
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|U.S. Classification||174/102.00R, 174/102.0SP|
|Jul 21, 2011||FPAY||Fee payment|
Year of fee payment: 4
|Jul 28, 2015||FPAY||Fee payment|
Year of fee payment: 8