CA2298313C - A semi-shielded cable - Google Patents
A semi-shielded cable Download PDFInfo
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- CA2298313C CA2298313C CA 2298313 CA2298313A CA2298313C CA 2298313 C CA2298313 C CA 2298313C CA 2298313 CA2298313 CA 2298313 CA 2298313 A CA2298313 A CA 2298313A CA 2298313 C CA2298313 C CA 2298313C
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Abstract
A semi-shielded twisted pair of wires is having at least one shield wire intertwined with the twisted pair of insulated wires. The at least one shield wire is preferably intertwined in the interstitial spaces between the twisted pair of insulated wires.
Description
A SEMI-SHIELDED CABLE
Background Of The Invention 1. Field of the Invention The present invention relates to twisted pair wires. More particularly, it relates to twisted pair wires including at least one shield wire intertwined with the twisted wire pair.
Background Of The Invention 1. Field of the Invention The present invention relates to twisted pair wires. More particularly, it relates to twisted pair wires including at least one shield wire intertwined with the twisted wire pair.
2. Related Art High speed data communications cables in current usage 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: TIABIA-568-A, published October 24, 1995; TIA/EIA 568-A-1 published September 25, 1997; and TIA/EIA 568-A-2, published August 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 is inversely proportional to the center-to-center distance between wires. 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.
A twisted pair can considered to be a chain of loops longitudinally staggered and alternating. If a twisted pair within a cable includes the same pattern for its chain of loops as does an adjacent pair, the two twisted pairs will become closely intertwined with each other and follow the same general path. The chain of loops in a twisted pair can be described using two parameters: the twist lay of the cable and the twist direction. In twisted pairs, the twist lay is the longitudinal distance between twists of the wire.
Likewise, the direction of the twist is known as the twist direction. If adjacent twisted pairs have the same twist lay and the opposite twist direction, the twisted pairs will tend to lie more closely together within a cable than if they have different twist lays and the same twist directions. Thus, compared to twisted pairs having different twist lays and the same twist directions, adjacent twisted pairs having the same twist lay and an opposite twist direction have a reduced center-to-center distance. In addition, because the two intertwined twisted pairs follow the same path, the intertwined twisted pairs can also have a longer parallel run. Therefore, the level of crosstalk tends to be higher between the twisted pairs having the same twist lay and the same twist direction when compared to other twisted pairs having different twist lays the same twist directions. To avoid the increased level of cross talk associated with other twisted pairs within a cable, the twisted pairs within a cable are sometimes given unique twist lays when compared to other adjacent twisted pairs within the cable. Thus, the unique twist lay serves to decrease the level of crosstalk between the adjacent twisted pairs within the cable.
Even if each adjacent twisted pairs in cable has a unique twist lay other problems may occur. In particular, during use, mechanical stress rnay interlink adjacent twisted pairs. Interlinking occurs when two adjacent 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 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: TIABIA-568-A, published October 24, 1995; TIA/EIA 568-A-1 published September 25, 1997; and TIA/EIA 568-A-2, published August 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 is inversely proportional to the center-to-center distance between wires. 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.
A twisted pair can considered to be a chain of loops longitudinally staggered and alternating. If a twisted pair within a cable includes the same pattern for its chain of loops as does an adjacent pair, the two twisted pairs will become closely intertwined with each other and follow the same general path. The chain of loops in a twisted pair can be described using two parameters: the twist lay of the cable and the twist direction. In twisted pairs, the twist lay is the longitudinal distance between twists of the wire.
Likewise, the direction of the twist is known as the twist direction. If adjacent twisted pairs have the same twist lay and the opposite twist direction, the twisted pairs will tend to lie more closely together within a cable than if they have different twist lays and the same twist directions. Thus, compared to twisted pairs having different twist lays and the same twist directions, adjacent twisted pairs having the same twist lay and an opposite twist direction have a reduced center-to-center distance. In addition, because the two intertwined twisted pairs follow the same path, the intertwined twisted pairs can also have a longer parallel run. Therefore, the level of crosstalk tends to be higher between the twisted pairs having the same twist lay and the same twist direction when compared to other twisted pairs having different twist lays the same twist directions. To avoid the increased level of cross talk associated with other twisted pairs within a cable, the twisted pairs within a cable are sometimes given unique twist lays when compared to other adjacent twisted pairs within the cable. Thus, the unique twist lay serves to decrease the level of crosstalk between the adjacent twisted pairs within the cable.
Even if each adjacent twisted pairs in cable has a unique twist lay other problems may occur. In particular, during use, mechanical stress rnay interlink adjacent twisted pairs. Interlinking occurs when two adjacent 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.
Shielded twisted pair cable, although exhibiting better crosstalk isolation, is more difficult and time consuming to install and terminate. Shielded conductors are generally terminated using special tools, devices and techniques adapted for the job.
Although not as effective as shielded twisted pair cable, one popular cable type meeting the above specifications 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 modern state of the art transmission systems require UTP cables to meet very stringent requirements. UTP cables are produced today with a very high degree of balance and impedance regularity. In order to achieve this balance and regularity, the manufacturing process of UTP cables includes twisters that have internal take-ups and give-ups that allow a back torsion to be created on each wire prior to entering the twister. Therefore, UTP cable has very high impedance regularities due to the randomization of eventual eccentricities in a twisted wire pair during manufacturing.
What is needed therefore is a cable exceeding the capabilities of UTP cables and able to prevent the interlinking of two or more twisted pairs without the difficulties and expenses associated with shielded twisted pair cable.
Summary Of The Invention The present invention is embodied in a semi-shielded twisted wire pair for reducing crosstalk within a UTP cable that overcomes the above and other drawbacks of conventional UTP cables.
According to one aspect, the semi-shielded cable includes a pair of twisted insulated conductors having at least one shield wire intertwined with the pair of insulated conductors at substantially the same helicoidal pitch as the conductors.
In one embodiment, the pair of insulated conductors forming the twisted pair have a plurality of interstitial spaces defined between them. In this embodiment, the shield wire is intertwined with the twisted pair within the plurality of interstitial spaces.
In another embodiment, first and second shield wires are intertwined with the twisted pair within the plurality of interstitial spaces.
In another embodiment, the two shield wires are uninsulated conductors and are in periodic physical contact and are electrically connected together.
Although not as effective as shielded twisted pair cable, one popular cable type meeting the above specifications 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 modern state of the art transmission systems require UTP cables to meet very stringent requirements. UTP cables are produced today with a very high degree of balance and impedance regularity. In order to achieve this balance and regularity, the manufacturing process of UTP cables includes twisters that have internal take-ups and give-ups that allow a back torsion to be created on each wire prior to entering the twister. Therefore, UTP cable has very high impedance regularities due to the randomization of eventual eccentricities in a twisted wire pair during manufacturing.
What is needed therefore is a cable exceeding the capabilities of UTP cables and able to prevent the interlinking of two or more twisted pairs without the difficulties and expenses associated with shielded twisted pair cable.
Summary Of The Invention The present invention is embodied in a semi-shielded twisted wire pair for reducing crosstalk within a UTP cable that overcomes the above and other drawbacks of conventional UTP cables.
According to one aspect, the semi-shielded cable includes a pair of twisted insulated conductors having at least one shield wire intertwined with the pair of insulated conductors at substantially the same helicoidal pitch as the conductors.
In one embodiment, the pair of insulated conductors forming the twisted pair have a plurality of interstitial spaces defined between them. In this embodiment, the shield wire is intertwined with the twisted pair within the plurality of interstitial spaces.
In another embodiment, first and second shield wires are intertwined with the twisted pair within the plurality of interstitial spaces.
In another embodiment, the two shield wires are uninsulated conductors and are in periodic physical contact and are electrically connected together.
In another embodiment, the semi-shielded cable includes a pair of insulated conductors twisted together having a first helicoidal pitch, and two shield wires being intertwined with the pair of insulated conductors at substantially the same helicoidal pitch. In another embodiment, the two shielded wires are intertwined with the pair of insulated conductors being placed substantially diametrically opposed to one another.
A method is also provided for manufacturing a semi-shielded cable. In one aspect , the method provides for supplying a pair of individually insulated conductors and a shield wire, applying the pair of individually insulated conductors and the first shield wire to a die for orienting the pair of individually insulated conductors in a predetermined orientation, and twisting the pair of individually insulated conductors and the shield wire together at a predetermined twist lay and in a predetermined twist direction. In one embodiment during the twisting operation, back torsion is applied to the pair of individually insulated conductors. In another embodiment, a second shield wire is used, and can be disposed diametrically opposed to the first shield wire.
In another aspect the method of manufacturing a semi-shielded wire can include supplying a pair of insulated parallel conductors, wherein the insulation surrounding each of the conductors is joined at the centerline between the conductors.
Twisting the joined, parallel insulated conductors in a helical manner, and providing a shield wire and laying up the shield wire into the interstices between the twisted joined insulated conductors. In one embodiment a second shield wire may be used and in another embodiment, the twisting the joined parallel insulated conductors includes twisting them together with a predetermined distance between twists.
Brief Description Of The Drawings In the drawings in which like reference numerals designate like elements, Fig. 1 is a perspective view of a semi-shielded cable according to one embodiment of the invention;
Fig. 2 is a transverse cross-sectional view of the semi-shielded cable according to the embodiment of Fig. 1; and Fig. 3 is a flow chart of one embodiment of a process for manufacturing a semi-shielded cable.
A method is also provided for manufacturing a semi-shielded cable. In one aspect , the method provides for supplying a pair of individually insulated conductors and a shield wire, applying the pair of individually insulated conductors and the first shield wire to a die for orienting the pair of individually insulated conductors in a predetermined orientation, and twisting the pair of individually insulated conductors and the shield wire together at a predetermined twist lay and in a predetermined twist direction. In one embodiment during the twisting operation, back torsion is applied to the pair of individually insulated conductors. In another embodiment, a second shield wire is used, and can be disposed diametrically opposed to the first shield wire.
In another aspect the method of manufacturing a semi-shielded wire can include supplying a pair of insulated parallel conductors, wherein the insulation surrounding each of the conductors is joined at the centerline between the conductors.
Twisting the joined, parallel insulated conductors in a helical manner, and providing a shield wire and laying up the shield wire into the interstices between the twisted joined insulated conductors. In one embodiment a second shield wire may be used and in another embodiment, the twisting the joined parallel insulated conductors includes twisting them together with a predetermined distance between twists.
Brief Description Of The Drawings In the drawings in which like reference numerals designate like elements, Fig. 1 is a perspective view of a semi-shielded cable according to one embodiment of the invention;
Fig. 2 is a transverse cross-sectional view of the semi-shielded cable according to the embodiment of Fig. 1; and Fig. 3 is a flow chart of one embodiment of a process for manufacturing a semi-shielded cable.
Detailed Description Generally, the illustrative embodiment of the present invention includes a cable having twisted pairs of individually insulated conductors, hereinafter referred to as "twisted pairs," with reduced levels of crosstalk when compared to conventional twisted pairs. The reduction of crosstalk is achieved by the use of at least one shield wire intertwined with each twisted pair. The at least one shield wire has shielding properties that reduce the level of inductive coupling between adjacent pairs. In addition, the intertwining of the at least one shield wire with the twisted pair increases the distance between the center of adjacent wires in adjacent twisted pairs, reduces the electric field coupling.
Fig. 1 is a perspective view of one embodiment of a semi-shielded cable 100. A
pair of insulated conductors 102 and 104 are arranged such that they are helically twisted about one another. The two insulated conductors 102 and 104 thus form a twisted pair having a twist lay as described above. As shown in Fig. 2, insulated conductors 102 and 104 include an inner conductor 112 and 116 respectively surrounded by an insulating cable jacket 110 and 114 respectively. Referring back to Fig. l, a pair of shield wires 106 and 108, are intertwined with the twisted pair of insulated conductors 102, 104 at substantially the same twist lay. In one embodiment of the present invention, the twisted pair of insulated conductors, 102 and 104, form interstitial spaces 118 between them.
The shield wires, 106 and 108 are then intertwined within these interstitial spaces 118.
In one embodiment, the shield wires 106 and 108 are uninsulated conductors that are in physical and electrical contact with each other. The shielding effectiveness depends upon how closely the helical twist lay of the shield wires 106, 108 is matched to the helical twist lay of the twisted pairs of insulated conductors 102, 104. As will be explained in more detail below, the closer the helical twist lay is matched, the greater the shielding effect will be.
Crosstalk interference within a cable having multiple twisted pairs can be primarily from two sources. The first source of crosstalk interference can be from adjacent twisted pairs within the cable. This is referred to as internal crosstalk or inner cable crosstalk. The second source of crosstalk interference is from other adjacent cables or other electrical noise sources external to the cable. This is referred to as external crosstalk or alien crosstalk.
Fig. 1 is a perspective view of one embodiment of a semi-shielded cable 100. A
pair of insulated conductors 102 and 104 are arranged such that they are helically twisted about one another. The two insulated conductors 102 and 104 thus form a twisted pair having a twist lay as described above. As shown in Fig. 2, insulated conductors 102 and 104 include an inner conductor 112 and 116 respectively surrounded by an insulating cable jacket 110 and 114 respectively. Referring back to Fig. l, a pair of shield wires 106 and 108, are intertwined with the twisted pair of insulated conductors 102, 104 at substantially the same twist lay. In one embodiment of the present invention, the twisted pair of insulated conductors, 102 and 104, form interstitial spaces 118 between them.
The shield wires, 106 and 108 are then intertwined within these interstitial spaces 118.
In one embodiment, the shield wires 106 and 108 are uninsulated conductors that are in physical and electrical contact with each other. The shielding effectiveness depends upon how closely the helical twist lay of the shield wires 106, 108 is matched to the helical twist lay of the twisted pairs of insulated conductors 102, 104. As will be explained in more detail below, the closer the helical twist lay is matched, the greater the shielding effect will be.
Crosstalk interference within a cable having multiple twisted pairs can be primarily from two sources. The first source of crosstalk interference can be from adjacent twisted pairs within the cable. This is referred to as internal crosstalk or inner cable crosstalk. The second source of crosstalk interference is from other adjacent cables or other electrical noise sources external to the cable. This is referred to as external crosstalk or alien crosstalk.
In one embodiment, both inner cable and alien crosstalk can be reduced due to two different mechanisms. First, the shield wires themselves act as a magnetic shield, reducing the level of inductively coupled crosstalk. This reduction in inductively coupled crosstalk will reduce both inner-cable crosstalk and alien crosstalk.
In addition, although the transverse view shown in Fig. 2 resembles a quad-cable, the shield wires are preferably common mode terminated during use. Preferably, the wire pair 102, 104 is driven in differential mode, and the shield wires should be connected to the center tap of the balanced transformer in the differential driver. If the twisted pair is driven by a pair of amplifiers forming a differential amplifier then shield wires can be electrically connected at the neutral point between the two amplifiers. This will ensure a highly balanced transmission mode and achieve a high shielding effect as well. A
highly balanced transmission line is desirable in order to reduce common mode signals. A
highly balanced transmission line driven differentially will provide two sets of signals to the differential output amplifier at the end of the transmission line. The first is the differential data signal. The second is the common mode signals, that is, signals having substantially equivalent interference levels at each wire. These signals are attenuated by the common mode rejection ratio of the differential amplifier. The more highly balanced the twisted pair, the more equivalent the interference levels on each wire are. Therefore, the more highly balanced the twisted pair is, the greater the attenuation of interference will be at the output differential amplifier.
The shield wires 106, 108 also will prevent adjacent pairs within the cable from interlinking thus increasing the center-to-center distance between the twisted pairs. As explained above, interlinking occurs in conventional twisted pair cables when adjacent twisted pairs become intertwined within the interstitial spaces between the insulated conductors. In one embodiment, the present invention prevents interlinking between twisted pairs from occurring because the shield wires 106, 108 are intertwined within the interstitial spaces between the insulated conductors 102 and 104. This will fill in the interstitial spaces between the insulated conductors 102 and 104, and has the effect of increasing the center-to-center distance between the pairs within the cable because the cables are prevented from interlinking. This can reduce the level of crosstalk between adjacent twisted pairs when compared to a standard cable. In general, the shield wires of an individual twisted pair are not in physical or electrical contact. However, in a cable containing multiple twisted pairs, each having two shield wires, the shield wires of each twisted pair will be in physical contact at a plurality of locations with other shield wires, and therefore are in electrical contact with each other as well. Thus, only one shield wire need be connected to an external reference mode.
Fig. 3 is a method for manufacturing a semi-shielded cable according to one aspect of the present invention. In step 302, a pair of individually insulated conductors and are provided and in step 304 are applied to a die to be properly oriented.
In one embodiment, a back torsion is applied to the pair of properly oriented insulated conductors, step 306, in order to provide for a high degree of impedance regularity between the pair of insulated conductors. A pair of shield wires is provided, step 308, and the pair of insulated conductors and shield wires are twisted together forming a semi-shielded cable, step 310. The shield wires themselves preferably do not need any kind of back torsioning and therefore may be paid off the regular give-ups.
The tensions applied to the shielding wires 106, 108 preferably are smaller than the insulated conductors 102, 104. Because the shield wires have a substantially lower tension than the insulated conductors, the shield wires are substantially filling only the interstices between the insulated conductors 102, 104 of the twisted pairs. This ensures that the formation of pair 102, 104 and, in particular the longitudinal contact line between the pair 102 and 104 is maintained. Preferably, this longitudinal contact line between the pair 102, 104 forms substantially a straight line between the two wires. Due to the lower tension applied to the shield wires 106, 108 during the twisting stage, the shield wires 106, 108 fill in the interstices between the pair 102, 104. Thus, shield wires 106, 108 will have a longitudinal contact line with each of the wires of pair 102, 104 that forms substantially a helix.
In another embodiment, the pair of insulated conductors could also have a web of insulation disposed between them, connecting the two wires together prior to the twisting process. This can be produced by surrounding the two parallel conductors with insulation that is joined at the centerline of the conductors. Advantageously this arrangement provides for a consistent center-to-center distance. The wires are then generally twisted and provide good impedance stability and attenuation regularity. The shield wires may be laid up during the twisting of the insulated conductors and then added directly to the interstitial spaces between the insulated conductors without applying a back torsion to them. In this way, the shield wires are not likely to split the twisted pair apart by separating the web of insulation disposed between the insulated _g_ conductors. Advantageously, the produces twisted pairs less subject to tension variations of the shield wires and insulated conductors.
Having now described an embodiment of the invention, it should be apparent to those skilled in the art that the foregoing is merely illustrative and not limiting, having been presented by way of example only. Numerous modifications and other embodiments are within the scope of one of ordinary skill in the art. These and other modifications are contemplated as falling within the scope of the invention as defined by the appended claims and equivalents thereto.
What is claimed is:
In addition, although the transverse view shown in Fig. 2 resembles a quad-cable, the shield wires are preferably common mode terminated during use. Preferably, the wire pair 102, 104 is driven in differential mode, and the shield wires should be connected to the center tap of the balanced transformer in the differential driver. If the twisted pair is driven by a pair of amplifiers forming a differential amplifier then shield wires can be electrically connected at the neutral point between the two amplifiers. This will ensure a highly balanced transmission mode and achieve a high shielding effect as well. A
highly balanced transmission line is desirable in order to reduce common mode signals. A
highly balanced transmission line driven differentially will provide two sets of signals to the differential output amplifier at the end of the transmission line. The first is the differential data signal. The second is the common mode signals, that is, signals having substantially equivalent interference levels at each wire. These signals are attenuated by the common mode rejection ratio of the differential amplifier. The more highly balanced the twisted pair, the more equivalent the interference levels on each wire are. Therefore, the more highly balanced the twisted pair is, the greater the attenuation of interference will be at the output differential amplifier.
The shield wires 106, 108 also will prevent adjacent pairs within the cable from interlinking thus increasing the center-to-center distance between the twisted pairs. As explained above, interlinking occurs in conventional twisted pair cables when adjacent twisted pairs become intertwined within the interstitial spaces between the insulated conductors. In one embodiment, the present invention prevents interlinking between twisted pairs from occurring because the shield wires 106, 108 are intertwined within the interstitial spaces between the insulated conductors 102 and 104. This will fill in the interstitial spaces between the insulated conductors 102 and 104, and has the effect of increasing the center-to-center distance between the pairs within the cable because the cables are prevented from interlinking. This can reduce the level of crosstalk between adjacent twisted pairs when compared to a standard cable. In general, the shield wires of an individual twisted pair are not in physical or electrical contact. However, in a cable containing multiple twisted pairs, each having two shield wires, the shield wires of each twisted pair will be in physical contact at a plurality of locations with other shield wires, and therefore are in electrical contact with each other as well. Thus, only one shield wire need be connected to an external reference mode.
Fig. 3 is a method for manufacturing a semi-shielded cable according to one aspect of the present invention. In step 302, a pair of individually insulated conductors and are provided and in step 304 are applied to a die to be properly oriented.
In one embodiment, a back torsion is applied to the pair of properly oriented insulated conductors, step 306, in order to provide for a high degree of impedance regularity between the pair of insulated conductors. A pair of shield wires is provided, step 308, and the pair of insulated conductors and shield wires are twisted together forming a semi-shielded cable, step 310. The shield wires themselves preferably do not need any kind of back torsioning and therefore may be paid off the regular give-ups.
The tensions applied to the shielding wires 106, 108 preferably are smaller than the insulated conductors 102, 104. Because the shield wires have a substantially lower tension than the insulated conductors, the shield wires are substantially filling only the interstices between the insulated conductors 102, 104 of the twisted pairs. This ensures that the formation of pair 102, 104 and, in particular the longitudinal contact line between the pair 102 and 104 is maintained. Preferably, this longitudinal contact line between the pair 102, 104 forms substantially a straight line between the two wires. Due to the lower tension applied to the shield wires 106, 108 during the twisting stage, the shield wires 106, 108 fill in the interstices between the pair 102, 104. Thus, shield wires 106, 108 will have a longitudinal contact line with each of the wires of pair 102, 104 that forms substantially a helix.
In another embodiment, the pair of insulated conductors could also have a web of insulation disposed between them, connecting the two wires together prior to the twisting process. This can be produced by surrounding the two parallel conductors with insulation that is joined at the centerline of the conductors. Advantageously this arrangement provides for a consistent center-to-center distance. The wires are then generally twisted and provide good impedance stability and attenuation regularity. The shield wires may be laid up during the twisting of the insulated conductors and then added directly to the interstitial spaces between the insulated conductors without applying a back torsion to them. In this way, the shield wires are not likely to split the twisted pair apart by separating the web of insulation disposed between the insulated _g_ conductors. Advantageously, the produces twisted pairs less subject to tension variations of the shield wires and insulated conductors.
Having now described an embodiment of the invention, it should be apparent to those skilled in the art that the foregoing is merely illustrative and not limiting, having been presented by way of example only. Numerous modifications and other embodiments are within the scope of one of ordinary skill in the art. These and other modifications are contemplated as falling within the scope of the invention as defined by the appended claims and equivalents thereto.
What is claimed is:
Claims (19)
1. A semi-shielded cable comprising:
a pair of insulated conductors twisted together forming a twisted pair, said twisted pair having a first helicoidal twist lay, at least one shield wire intertwined with the twisted pair, the shield wire being intertwined with the twisted pair of at substantially the first helicoidal pitch.
a pair of insulated conductors twisted together forming a twisted pair, said twisted pair having a first helicoidal twist lay, at least one shield wire intertwined with the twisted pair, the shield wire being intertwined with the twisted pair of at substantially the first helicoidal pitch.
2. The semi-shielded cable as in claim 1 further comprising:
a second shield wire intertwined with the twisted pair and the at least one shield wire, being substantially diametrically opposed and at substantially the first helicoidal pitch.
a second shield wire intertwined with the twisted pair and the at least one shield wire, being substantially diametrically opposed and at substantially the first helicoidal pitch.
3. The semi-shielded cable as in claim 2, wherein the at least one and second shield wires are substantially diametrically opposed.
4. The semi-shielded cable as in claim 2, wherein the at least one and the second shield wire are uninsulated conductors.
5. The semi-shielded cable as in claim 4, wherein the at least one and the second shield wires are not in physical contact with each other.
6. A semi-shielded cable as in claim 1, wherein the insulated conductors maintain a longitudinal contact line therebetween.
7. A semi-shielded cable as in claim 6, wherein the longitudinal contact line is a substantially straight line.
8. A semi-shielded cable as in claim 1, wherein the at least one shield wire maintains a contact line with said twisted pair.
9. A semi-shielded cable as in claim 1, wherein said twisted pair have a plurality of interstitial spaces defined between the insulated conductors thereof; the at least one shield wire being intertwined with the twisted pair within the plurality of interstitial spaces.
10. A semi-shielded cable as in claim 5, wherein the contact line is substantially helical.
11. The semi-shielded cable as in claim 1, wherein the at least one shield wire is insulated.
12. A method for manufacturing a semi-shielded cable comprising steps of:
providing a pair of individually insulated conductors and a shield wire;
applying the pair of individually insulated conductors and the said first shield wire to a die for orienting the pair of individually insulated conductors in a predetermined orientation;
providing a second shield wire;
twisting the pair of individually insulated conductors and the second shield wire together at a predetermined twist lay and in a predetermined twist direction.
providing a pair of individually insulated conductors and a shield wire;
applying the pair of individually insulated conductors and the said first shield wire to a die for orienting the pair of individually insulated conductors in a predetermined orientation;
providing a second shield wire;
twisting the pair of individually insulated conductors and the second shield wire together at a predetermined twist lay and in a predetermined twist direction.
13. The method of claim 12, further including prior to the step of twisting, applying a back torsion to the pair of individually insulated conductors.
14. The method of claim 7, wherein the step of providing includes providing a second shield wire.
15. The method of claim 7, further comprising the step of twisting the pair of individually insulated conductors and the first and second shield wires together at a predetermined twist lay and in a predetermined twist direction.
16. The method of claim 15, further including prior to the step of twisting, applying a back torsion to the pair of individually insulated conductors.
17. A method for manufacturing a semi-shielded cable comprising the steps of:
providing a pair of insulated parallel conductors, wherein the insulation surrounding each of the conductors are joined at the centerline between the conductors;
twisting the joined, parallel insulated conductors in a helical manner;
providing a shield wire;
laying up the shield wire into the interstices between the twisted joined insulated conductors.
providing a pair of insulated parallel conductors, wherein the insulation surrounding each of the conductors are joined at the centerline between the conductors;
twisting the joined, parallel insulated conductors in a helical manner;
providing a shield wire;
laying up the shield wire into the interstices between the twisted joined insulated conductors.
18. The method as in claim 17, wherein the step of providing a shield wire includes providing a pair of shield wires.
19. The method as in claim 17, wherein the step of twisting the joined parallel insulated conductors includes twisting them with a predetermined distance between twists.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US26341499A | 1999-03-05 | 1999-03-05 | |
| US09/263,414 | 1999-03-05 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2298313A1 CA2298313A1 (en) | 2000-09-05 |
| CA2298313C true CA2298313C (en) | 2001-08-14 |
Family
ID=23001685
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2298313 Expired - Fee Related CA2298313C (en) | 1999-03-05 | 2000-02-10 | A semi-shielded cable |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2298313C (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106384629B (en) * | 2016-11-30 | 2018-08-28 | 山东希尔电缆有限公司 | A kind of high-transmission charge bearing detecting cable |
| CN112271014A (en) * | 2020-09-23 | 2021-01-26 | 上海天诚通信技术股份有限公司 | Foaming type one-to-one Ethernet twisted pair |
| CN112271015A (en) * | 2020-09-23 | 2021-01-26 | 上海天诚通信技术股份有限公司 | Enhanced one-to-one Ethernet twisted pair |
-
2000
- 2000-02-10 CA CA 2298313 patent/CA2298313C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2298313A1 (en) | 2000-09-05 |
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| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |