Patent Publication Number: US-9418775-B2

Title: Separator tape for twisted pair in LAN cable

Description:
This application is a continuation-in-part of U.S. application Ser. No. 13/182,778 filed Jul. 14, 2011, which is a continuation of U.S. application Ser. No. 12/407,407 filed Mar. 19, 2009, now U.S. Pat. No. 7,999,184, which claims the benefit of U.S. Provisional Application No. 61/037,904, filed Mar. 19, 2008, the contents of each application are herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a twisted pair cable for communication of high speed signals, such as a local area network (LAN) cable. More particularly, the present invention relates to a twisted pair cable having a dielectric tape between first and second insulated conductors of a twisted pair. 
     2. Description of the Related Art 
     As shown in  FIGS. 1 and 2 , the Assignee&#39;s prior U.S. Pat. No. 6,506,976 shows a LAN cable  1  having a jacket J surrounding first through fourth twisted pairs A, B, C, D which are spaced from each other by a separator  3 . Each of the twisted pairs A, B, C, D includes a first insulated conductor  5 , a dielectric tape  7 , and a second insulated conductor  9 , wherein the first insulated conductor  5  is twisted with the second insulated conductor  9  with the dielectric tape  7  residing between the first insulated conductor  5  and the second insulated conductor  9 . 
     As best seen in the close-up cross sectional view of the twisted pair A in  FIG. 2 , the width of the dielectric tape  7 , which extends between opposing edges  11  and  13 , is set to extend beyond the first and second insulated conductors  5  and  9 . By this arrangement, the opposing edges  11  and  13  of the dielectric tape  7  circumscribe an area  15 , around the twisted pairs A, B, C, D. The area  15  creates a spacing between the twisted pairs A, B, C, D and the separator  3  and between the twisted pairs A, B, C, D and the jacket J. This spacing around the twisted pairs A, B, C, D can improve the electrical performance of the cable  1 , such as by reducing crosstalk. 
     In typical cables of the background art, the first insulated conductor  5  would be formed by a first conductor  17  of about twenty-three gauge size, surrounded by a layer of a first dielectric insulating material  19  having a radial thickness greater than seven mils, such as about tens mils or about eleven mils for a typical CAT  6  cable. Likewise, the second insulated conductor  9  would be formed by a second conductor  21  of about twenty-three gauge size, surrounded by a layer of a second dielectric insulating material  23  having a same or similar radial thickness. 
     SUMMARY OF THE INVENTION 
     Although the cable of the background art performs well, Applicants have appreciated some drawbacks. Applicants have invented a twisted pair cable with new structural features, the object of which is to enhance one or more performance characteristics of a LAN cable, such as reducing insertion loss, matching impedance, reducing propagation delay and/or balancing delay skew between twisted pairs, and/or to enhance one or more mechanical characteristics of a LAN cable, such as improving flexibility, reducing weight, reducing cable diameter and reducing smoke emitted in the event of a fire. 
     These and other objects are accomplished by a cable that includes a first insulated conductor, a first dielectric tape, and a second insulated conductor, wherein the first insulated conductor is twisted with the second insulated conductor with the first dielectric tape residing therebetween to form a first twisted pair. A jacket is formed around the first twisted pair. The cable may also include a third insulated conductor, a second dielectric tape, and a fourth insulated conductor, wherein the third insulated conductor is twisted with the fourth insulated conductor with the second dielectric tape residing therebetween to form a second twisted pair. If the second twisted pair is provided, the jacket is formed around both the first and second twisted pairs. 
     In a first alternative or supplemental objective of the invention, the first insulated conductor includes a first conductor surrounded by a layer of first dielectric insulating material having a radial thickness of about 7 mils or less. 
     In a second alternative or supplemental objective of the invention, the first dielectric tape is formed as a single unitary structure having a first width which extends approximately perpendicular to an extension length of the first twisted pair from a first edge of the first dielectric tape to a second edge of the first dielectric tape, wherein the first width is equal to or less than a diameter of the first insulated conductor plus a diameter of the second insulated conductor plus a thickness of the first dielectric tape. 
     In a third alternative or supplemental objective of the invention, the first dielectric tape has a cross sectional shape in a direction perpendicular to the extension length of the first twisted pair, which presents a first recessed portion for seating the first insulated conductor and a second recessed portion for seating the second insulated conductor. 
     In a fourth alternative or supplemental objective of the invention, a first twist length of the first twisted pair is between approximately 0.22 inches and approximately 0.38 inches, and a second twist length of the second twisted pair is different from the first twist length and is between approximately 0.22 inches and approximately 0.38 inches. 
     In a fifth alternative or supplemental objective of the invention, the first dielectric tape is different in shape, size or material content as compared to the second dielectric tape. 
     In a sixth alternative or supplemental objective of the invention, the first, second, third and fourth insulated conductors are identical in appearance, and the first dielectric tape is different in appearance from the second dielectric tape. 
     In a seventh alternative or supplemental objective of the invention, the first dielectric tape has a hollow core possessing a gas or material with a lower dielectric constant than a material used to form the first dielectric tape. 
     In an eighth alternative or supplemental objective of the invention, the first dielectric tape has at least a first side facing to said first insulated conductor, which includes a plurality of ridges and valleys. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limits of the present invention, and wherein: 
         FIG. 1  is a cross sectional view of a twisted pair cable, in accordance with the prior art; 
         FIG. 2  is a close-up cross sectional view of a twisted pair in the cable of  FIG. 1 ; 
         FIG. 3  is a perspective view of a twisted pair cable, in accordance with a first embodiment of the present invention; 
         FIG. 4  is a cross sectional view of the twisted pair cable of  FIG. 3  taken along line IV-IV; 
         FIG. 5  is a close-up cross sectional view of a twisted pair from  FIG. 4 ; 
         FIG. 5A  is a close up cross sectional view of a twisted pair similar to  FIG. 5 , but illustrating that the dielectric tape may include a hollow air pocket; 
         FIG. 6  is a close-up cross sectional view of a twisted pair, having a dielectric tape with an alternative shape, in accordance with a second embodiment of the present invention; 
         FIG. 7  is a cross sectional view of a twisted pair cable employing twisted pairs in accordance with  FIG. 6 ; 
         FIG. 8  is a close-up cross sectional view of a twisted pair, having a dielectric tape with an alternative shape, in accordance with a third embodiment of the present invention; 
         FIG. 8A  is a close-up cross sectional view of a twisted pair, having a dielectric tape with an alternative shape, in accordance with a fourth embodiment of the present invention; 
         FIG. 8B  is a cross sectional view of a twisted pair cable employing twisted pairs in accordance with  FIG. 8A ; 
         FIG. 9  is a perspective view of a twisted pair cable, in accordance with a fifth embodiment of the present of the present invention; 
         FIG. 10  is a cross sectional view of the twisted pair cable of  FIG. 9  taken along line X-X; 
         FIG. 11  is a close-up cross sectional view of a twisted pair from  FIG. 10 ; 
         FIG. 12  is a close-up cross sectional view of a twisted pair, having a dielectric tape with an alternative shape, in accordance with a sixth embodiment of the present invention; 
         FIG. 13  is a close-up cross sectional view of a twisted pair, having a dielectric tape with an alternative shape, in accordance with a seventh embodiment of the present invention; 
         FIG. 14  is a cross sectional view of a twisted pair cable employing twisted pairs in accordance with  FIG. 13 ; 
         FIG. 15  is a close-up cross sectional view of a twisted pair, having a dielectric tape with an alternative shape, in accordance with a eighth embodiment of the present invention; 
         FIG. 16  is a close-up cross sectional view of a twisted pair, having a dielectric tape with an alternative shape, in accordance with a ninth embodiment of the present invention; 
         FIG. 17  is a close-up cross sectional view of a twisted pair, having a dielectric tape with an alternative shape, in accordance with a tenth embodiment of the present invention; 
         FIG. 18  is a close-up cross sectional view of a twisted pair, having a dielectric tape with an alternative shape, in accordance with am eleventh embodiment of the present invention; 
         FIG. 19  is a close-up cross sectional view of a twisted pair, having a dielectric tape with an alternative configuration, in accordance with a twelfth embodiment of the present invention; and 
         FIGS. 20 and 20A  are close-up cross sectional views of a twisted pair, having a dielectric tape with an alternative configuration, in accordance with a thirteenth embodiment of the present invention; and  FIG. 20B  is a perspective view of the twisted pair of  FIG. 20A , showing the interval of the closed-cell air pockets. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     The present invention now is described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
     Like numbers refer to like elements throughout. In the figures, the thickness of certain lines, layers, components, elements or features may be exaggerated for clarity. Broken lines illustrate optional features or operations unless specified otherwise. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and relevant art and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Well-known functions or constructions may not be described in detail for brevity and/or clarity. 
     As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. As used herein, phrases such as “between X and Y” and “between about X and Y” should be interpreted to include X and Y. As used herein, phrases such as “between about X and Y” mean “between about X and about Y.” As used herein, phrases such as “from about X to Y” mean “from about X to about Y.” 
     It will be understood that when an element is referred to as being “on”, “attached” to, “connected” to, “coupled” with, “contacting”, etc., another element, it can be directly on, attached to, connected to, coupled with or contacting the other element or intervening elements may also be present. In contrast, when an element is referred to as being, for example, “directly on”, “directly attached” to, “directly connected” to, “directly coupled” with or “directly contacting” another element, there are no intervening elements present. It will also be appreciated by those of skill in the art that references to a structure or feature that is disposed “adjacent” another feature may have portions that overlap or underlie the adjacent feature. 
     Spatially relative terms, such as “under”, “below”, “lower”, “over”, “upper”, “lateral”, “left”, “right” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is inverted, elements described as “under” or “beneath” other elements or features would then be oriented “over” the other elements or features. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the descriptors of relative spatial relationships used herein interpreted accordingly. 
       FIG. 3  is a perspective view of a twisted pair cable  31 , in accordance with a first embodiment of the present invention.  FIG. 4  is a cross sectional view of the cable  31  taken along line IV-IV in  FIG. 3 . The cable  31  includes a jacket  32  formed around and surrounding first, second, third and fourth twisted pairs  33 ,  34 ,  35  and  36 , respectively. The jacket  32  may be formed of polyvinylchloride (PVC), low smoke zero halogen PVC, polyethylene (PE), fluorinated ethylene propylene (FEP), polyvinylidene fluoride (PVDF), ethylene chlorotrifluoroethylene (ECTFE), or other foamed or solid materials common to the cabling art. 
     A separator  37  within the jacket  32  resides between and separates the first and fourth twisted pairs  33  and  36  from the second and third twisted pairs  34  and  35 . In  FIGS. 3 and 4 , the separator  37  is formed by a thin strip of dielectric material, having a thickness of about twenty mils or less, more preferably eighteen mils or less, such as about fifteen mils. However, other sizes and shapes of separators  37  may be employed in combination with the present invention, such as plus-shaped or star-shaped separators, sometimes referred to as a flute, isolator, or cross-web. The separator  37  may be formed of any solid or foamed material common to the cabling art, such as a polyolefin or fluoropolymer, like fluorinated ethylene propylene (FEP) or polyvinylchloride (PVC). 
     As best seen in the cross sectional view of  FIG. 4 , the first twisted pair  33  includes a first insulated conductor  38 , a first dielectric tape  39 , and a second insulated conductor  40 . The first insulated conductor  38  is twisted with the second insulated conductor  40 , in a helical fashion, with the first dielectric tape  39  residing between the first insulated conductor  38  and the second insulated conductor  40 . 
     The second twisted pair  34  includes a third insulated conductor  41 , a second dielectric tape  42 , and a fourth insulated conductor  43 . The third insulated conductor  41  is twisted with the fourth insulated conductor  43 , in a helical fashion, with the second dielectric tape  42  residing between the third insulated conductor  41  and the fourth insulated conductor  43 . 
     The third twisted pair  35  includes a fifth insulated conductor  44 , a third dielectric tape  45 , and a sixth insulated conductor  46 . The fifth insulated conductor  44  is twisted with the sixth insulated conductor  46 , in a helical fashion, with the third dielectric tape  45  residing between the fifth insulated conductor  44  and the sixth insulated conductor  46 . 
     The fourth twisted pair  36  includes a seventh insulated conductor  47 , a fourth dielectric tape  48 , and an eighth insulated conductor  49 . The seventh insulated conductor  47  is twisted with the eighth insulated conductor  49 , in a helical fashion, with the fourth dielectric tape  48  residing between the seventh insulated conductor  47  and the eighth insulated conductor  49 . 
       FIG. 5  is a close-up view of the first twisted pair  33 , which is similarly constructed although not identically constructed (as will be detailed later in the specification) to the second, third and fourth twisted pairs  34 ,  35  and  36 . Each of the first through eighth insulated conductors  38 ,  40 ,  41 ,  43 ,  44 ,  46 ,  47 ,  49  is formed by a conductor K surrounded by a layer of dielectric insulating material R, such as a polymer or foamed polymer, common to the cabling art like fluorinated ethylene propylene (FEP), polyethylene (PE) or polypropylene (PP). Further, the insulating material R may be formed by an enamel coating, or another nonconductive coating from a diverse art like motor armature windings. The conductor K may be solid or stranded, and may be formed of a conductive metal or alloy, such as copper. In one embodiment, the conductor K is a solid, copper wire of about twenty three gauge size. 
     In one embodiment, the insulating material R may have a radial thickness of about seven mils or less, more preferably about five mils or less. This radial thickness of the insulating layer R is at least 20% less than the standard insulation layer thickness of a conductor in a typical equivalent twisted pair wire, more preferably at least 25% to 30% less. Typically, such a thin insulation layer R would not be possible due to the incorrect impedance obtained when the conductors K of the first and second insulated conductors  38  and  40  become so closely spaced during the twisting operation due to the thinner insulating layers R. Typically, such thin insulation layers were not practiced in the background art, because there was no appreciation of a solution to the mechanical and performance problems. By the present invention, the interposed first dielectric tape  39  eases the mechanical stresses during twisting so that the thinner insulating layer R is undamaged and also spaces the conductors K apart so that a proper impedance may be obtained, e.g., one hundred ohms. 
     As best seen in  FIG. 5 , the first dielectric tape  39  has a first width which extends approximately perpendicular to an extension length of the first dielectric tape  39  from a first edge  51  of the first dielectric tape  39  to an opposing second edge  53  of the first dielectric tape  39 . The first width is less than a diameter of the first insulated conductor  38  plus a diameter of the second insulated conductor  40  plus a thickness of the first dielectric tape  39 , wherein the thickness is measured by the spacing created between the first and second insulated conductors  38  and  40 . A typical spacing might be between four to twelve mils, such as about eight mils or about ten mils. By this arrangement, the twists of the first twisted pair  33  occupy a space within the dashed line  55 , which is circumscribed by the helical twisting of the first and second insulated conductors  38  and  40 . In this arrangement, the first through eighth insulated conductors  38 ,  40 ,  41 ,  43 ,  44 ,  46 ,  47  and  49  may contact each other if adjacent and also may contact the inner wall of the jacket  32 . 
     In  FIG. 5 , the dielectric tape  39  is formed as a single unitary structure (e.g., the dielectric tape does not include multiple pieces attached together or layered).  FIG. 5A  illustrates that the solid dielectric tape  39  of  FIG. 5  may be replaced with a dielectric tape  39 A having a hollow core filled with a gas, like air (with a dielectric constant of 1.0) or a foamed insulation material (with a dielectric constant approaching 1.0). By filling the hollow core with a gas or material with a lower dielectric constant than a material used to form said first dielectric tape  39  or  39 A, the overall dielectric constant of the first dielectric tape  39 A may be reduced. The hollow core may extend the entire length of the dielectric tape  39 A, resulting in a “straw-like” structure. Alternatively, support structures may be formed at intervals along the length of the dielectric tape  39 A to form closed-cell air pockets, each having a short length, such as ½ inch, one inch, two inches, etc. Alternatively, one or more support structures may be formed within the hollow core, which extend along the length of the dielectric tape  39 A and connect between the lateral walls of the hollow core to resist crushing of the hollow core during the twisting of the first twisted pair  33 A. Although the other embodiments of the dielectric tapes of the present invention are illustrated with solid cores, hollow cores, as described in connection with  FIG. 5A , may be employed in any or all of the other dielectric tapes. The first twisted pair  33 A depicted in  FIG. 5A  may be substituted into the place of the first twisted pair  33  depicted in  FIG. 4 . 
     The first through fourth twisted pairs  33 ,  34 ,  35  and  36  may be stranded together in the direction  57  (see the arrow in  FIG. 3 ) to form a stranded core. In one embodiment, the core strand direction  57  is opposite to the pair twist directions of the first through fourth twisted pairs  33 ,  34 ,  35  and  36 . However, this is not a necessary feature, as in a preferred embodiment, the strand direction  57  is the same as the pair twist directions. 
     In preferred embodiments, the strand length of the core strand is about five inches or less, more preferably about three inches or less. In a more preferred embodiment, the core strand length is purposefully varied, or modulates, from an average strand length along a length of the cable  31 . Core strand modulation can assist in the reduction of alien crosstalk. For example, the core strand length could modulate between two inches and four inches along the length of the cable  31 , with an average value of three inches. 
     The first twist length w (See  FIG. 3 ) of the first twisted pair  33  is preferably set to a short length, such as between approximately 0.22 inches and approximately 0.38 inches. The second twist length x of the second twisted pair  34  is different from the first twist length w and is between approximately 0.22 inches and approximately 0.38 inches. For example, the first twist length w may be set to approximately 0.26 inches and the second twist length x may be set to approximately 0.33 inches. 
     In one embodiment, the first twist length w purposefully modulates from a first average value, such as 0.26 inches. For example, the first twist length could purposefully vary between 0.24 and 0.28 inches along the length of the cable. Likewise, the second twist length could purposefully modulate from a second average value, such as 0.33 inches. For example, the second twist length could purposefully vary between 0.31 and 0.35 inches along the length of the cable. 
     The third twisted pair  35  would have a third twist length y and the fourth twisted pair  36  would have a fourth twist length of z. In one embodiment, the third twist length y is different from the first, second and fourth twist lengths w, x and z, while the fourth twist length z is different from the first, second and third twist lengths w, x and y. Of course, the third and fourth twisted pairs  35  and  36  could employ a similar twist length modulation, as described in conjunction with the first and second twisted pairs  33  and  34 . 
       FIG. 6  is a close-up cross sectional view of a twisted pair  60 , having a dielectric tape  61  with an alternative shape, in accordance with a second embodiment of the present invention. The dielectric tape  61  has a width which extends approximately perpendicular to an extension length of the twisted pair  60  from a first edge  62  of the dielectric tape  61  to an opposing second edge  63  of the dielectric tape  61 . The width, in the embodiment of  FIG. 6 , is equal to or less than the diameter of the first insulated conductor  38 . Less material is used to form the dielectric tape  61  in the embodiment of  FIG. 6 . This presents advantages in reducing the amount of consumable material in the case of a fire, and in reducing the amount of smoke emitted from the cable  31  in the case of a fire. This structure may also reduce the weight and outer diameter of the cable and improve the flexibility of the cable. 
     As seen in  FIG. 6 , the dielectric tape  61  has a cross sectional shape in a direction perpendicular to an extension length of the twisted pair  60 , which presents a first recessed portion  64  for seating the first insulated conductor  38  and a second recessed portion  65  for seating the second insulated conductor  40 . 
     The cross sectional shapes of the dielectric tapes  39  and  61  in  FIGS. 5 and 6  are mirror symmetrical. However, it is not necessary that the shape be mirror symmetrical in order to achieve many of the advantages of the present invention. Further, the first and second recessed portions  64  and  65  of the dielectric tape  61  in  FIG. 6  are semi-circular in shape. However, it is not necessary that the first and second recessed portions  64  and  65  be semi-circular. In fact, the recesses in the dielectric tape  39  of  FIG. 5  for receiving the first and second insulated conductors  38  and  40  are not semi-circular in shape. Also, the first and second recessed portions  64  and  65  may include serrations to create pockets of air adjacent to the seated portions of the first and second insulated conductors  38  and  40 . 
       FIG. 7  is a cross sectional view of a twisted pair cable  66  employing the first twisted pair  60  of  FIG. 6 . The twisted pair cable  66  also includes similarly configured second, third and fourth twisted pairs  67 ,  68  and  69 . The twists of the first, second, third and fourth twisted pairs  60 ,  67 ,  68  and  69  occupy respective spaces within the dashed lines  55  (See  FIG. 6 ). In this arrangement, the first through eighth insulated conductors  38 ,  40 ,  41 ,  43 ,  44 ,  46 ,  47  and  49  may contact each other and also may contact the inner wall of the jacket  32 . 
       FIG. 8  is a close-up cross sectional view of a twisted pair  70 , having a dielectric tape  71  with an alternative shape, in accordance with a third embodiment of the present invention. The dielectric tape  71  has a width which extends approximately perpendicular to an extension length of the twisted pair  70  from a first edge  72  of the dielectric tape  71  to an opposing second edge  73  of the dielectric tape  71 . The width, in the embodiment of  FIG. 8 , is equal to or less than the diameter of the first insulated conductor  38 . 
     The embodiment of  FIG. 8  illustrates that the dielectric tape  71  need not have recessed portions  64  and  65  (as shown in  FIGS. 5 and 6 ) to seat the insulated conductors  38  and  40 . Rather, the dielectric tape  71  may be formed as a generally flat member. The dielectric tape  71  will remain between the first and second insulated conductors  38  and  40  due to the frictional forces created during the twisting operation, when the twisted pair  70  is formed. 
       FIG. 8A  is a close-up cross sectional view of a twisted pair  70 A, having a dielectric tape  71 A with an alternative shape, in accordance with a fourth embodiment of the present invention. The dielectric tape  71 A has a width which extends approximately perpendicular to an extension length of the twisted pair  70 A from a first edge  72 A of the dielectric tape  71 A to an opposing second edge  73 A of the dielectric tape  71 A. The width, in the embodiment of  FIG. 8A , is equal to or slightly less than (e.g., two to four mils less than) the diameter of the first insulated conductor  38  plus the diameter of the second insulated conductor  40  plus a thickness of the dielectric tape  71 A. 
     The embodiment of  FIG. 8A  illustrates that the dielectric tape  71 A may be a generally flat member having a width which is approximately equal the diameter of the first insulated conductor  38  plus the diameter of the second insulated conductor  40  plus a thickness of the dielectric tape  71 A, such as about seventy-two mils plus or minus about three mils. 
       FIG. 8B  is a cross sectional view of a twisted pair cable  76  employing the first twisted pair  70 A of  FIG. 8A , in accordance with a preferred embodiment of the present invention. The twisted pair cable  76  also includes similarly configured second, third and fourth twisted pairs  77 ,  78  and  79 . The twists of the first, second, third and fourth twisted pairs  70 A,  77 ,  78  and  79  occupy respective spaces within the dashed lines  55  (See  FIG. 8A ). In this arrangement, the first through eighth insulated conductors  38 ,  40 ,  41 ,  43 ,  44 ,  46 ,  47  and  49  may contact a plus-shaped separator  37 A (sometimes referred to as an isolator, a flute or a crossweb) and also may contact inner ends of projections or fins  32 A on the inner wall of the jacket  32 .  FIG. 8B  shows twelve projections  32 A, however more or fewer projections may be included, with the goal being to hold the core of twisted pairs  70 A,  77 ,  78  and  79  in the center of the cable  76  while creating air pockets around the perimeter of the core of twisted pairs. 
       FIG. 9  is a perspective view of a twisted pair cable  81 , in accordance with a fifth embodiment of the present invention.  FIG. 10  is a cross sectional view of the cable  81  taken along line X-X in  FIG. 9 . The cable  81  includes a jacket  82  formed around and surrounding first, second, third and fourth twisted pairs  83 ,  84 ,  85  and  86 , respectively. 
     The fifth embodiment of the invention, as illustrated in  FIGS. 9 and 10 , does not include a separator  37 . However, pair separators (sometimes referred to as tapes, isolators, flutes or crosswebs) may optionally be included, if desired. 
     As best seen in the cross sectional view of  FIG. 10 , the first twisted pair  83  includes a first insulated conductor  88 , a first dielectric tape  89 , and a second insulated conductor  90 . The first insulated conductor  88  is twisted with the second insulated conductor  90 , in a helical fashion, with the first dielectric tape  89  residing between the first insulated conductor  88  and the second insulated conductor  90 . 
     The second twisted pair  84  includes a third insulated conductor  91 , a second dielectric tape  92 , and a fourth insulated conductor  93 . The third insulated conductor  91  is twisted with the fourth insulated conductor  93 , in a helical fashion, with the second dielectric tape  92  residing between the third insulated conductor  91  and the fourth insulated conductor  93 . 
     The third twisted pair  85  includes a fifth insulated conductor  94 , a third dielectric tape  95 , and a sixth insulated conductor  96 . The fifth insulated conductor  94  is twisted with the sixth insulated conductor  96 , in a helical fashion, with the third dielectric tape  95  residing between the fifth insulated conductor  94  and the sixth insulated conductor  96 . 
     The fourth twisted pair  86  includes a seventh insulated conductor  97 , a fourth dielectric tape  98 , and an eighth insulated conductor  99 . The seventh insulated conductor  97  is twisted with the eighth insulated conductor  99 , in a helical fashion, with the fourth dielectric tape  98  residing between the seventh insulated conductor  97  and the eighth insulated conductor  99 . 
       FIG. 11  is a close-up view of the first twisted pair  83 , which is similarly constructed to the second, third and fourth twisted pairs  84 ,  85  and  86 . Like the first embodiment of  FIGS. 3-5 , each of the first through eighth insulated conductors  88 ,  90 ,  91 ,  93 ,  94 ,  96 ,  97  and  99  is formed by a conductor K surrounded by a layer of dielectric insulating material R. Also, the insulating material R may have a radial thickness of about seven mils or less, more preferably about five mils or less. 
     As best seen in  FIG. 11 , the first dielectric tape  89  has a first width which extends approximately perpendicular to an extension length of the first twisted pair  83  from a first edge  101  of the first dielectric tape  89  to a second edge  103  of the first dielectric tape  89 . The first width is greater than a diameter of the first insulated conductor  88  plus a diameter of the second insulated conductor  90  plus a thickness of the first dielectric tape  89 , wherein the thickness is measured by the spacing created between the first and second insulated conductors  88  and  90 . A typical spacing might be between four to twelve mils, such as about eight mils or about ten mils. By this arrangement, the twists of the first twisted pair  83  occupy a space within the dashed line  105 , which is circumscribed by the helical twisting of the first and second edges  101  and  103  of the first dielectric tape  89 . In this arrangement, the first through eighth insulated conductors  88 ,  90 ,  91 ,  93 ,  94 ,  96 ,  97  and  99  do not contact each other and also do not contact the inner wall of the jacket  82 . Rather, a small air pocket  107  is maintained around the outer perimeter of the dielectric insulating material R. Hence, the first insulated conductor  88  would be spaced from the inner wall of the jacket  82  by a first minimum distance, where the first minimum distance could be fixed in the range of one to twenty mils, such as two mils or four mils. Moreover, the first insulated conductor  88  would be spaced from any other insulated conductor of another twisted pair  84 ,  85  or  86  of the cable  81  by a second minimum distance. The second minimum distance would equal twice the first minimum distance, because the small air pocket  107  of the first twisted pair  83  would be added to the small air pocket  107  of the other twisted pair  84 ,  85  or  86 . 
     As in the first embodiment of  FIGS. 3-5 , the first through fourth twisted pairs  83 ,  84 ,  85  and  86  may be stranded together in the direction  109  (see the arrow in  FIG. 9 ) to form a stranded core. In one embodiment, the core strand direction  109  is opposite to the pair twist directions of the first through fourth twisted pairs  83 ,  84 ,  85  and  86 . However, this is not a necessary feature. The core strand length and pair twist lengths w, x, y and z may be tight, as described in conjunction with  FIGS. 3-5 , and may optionally be modulated. 
     As best seen in the cross sectional view of  FIG. 11 , the first dielectric tape  89  includes first and second recesses  111  and  113  to seat the first and second insulated conductors  88  and  90 . The first and second recesses  111  and  113  may assist in properly positioning the three parts  88 ,  89  and  90  of the first twisted pair  83  during a manufacturing process, and may also assist in keeping the three parts  88 ,  89  and  90  of the first twisted pair  83  in place during use of the cable  81  (e.g., pulling of the cable through conduits or ductwork). However, many advantages of the invention may be achieved without the recesses  111  and  113 , as will be seen in  FIG. 12 . 
       FIG. 12  is a close-up cross sectional view of a twisted pair  120 , having a dielectric tape  121  with an alternative shape, in accordance with a sixth embodiment of the present invention. The dielectric tape  121  has a width which extends approximately perpendicular to an extension length of the twisted pair  120  from a first edge  122  of the dielectric tape  121  to a second edge  123  of the dielectric tape  121 . Like the embodiment of  FIGS. 9-11 , the width of the dielectric tape  121  is greater than the diameter of the first insulated conductor  88  plus the diameter of the second insulated conductor  90  plus a thickness of the first dielectric tape  121 . The dielectric tape  121  may be formed as a generally flat member. The dielectric tape  121  will remain between the first and second insulated conductors  88  and  90  due to the frictional forces created during the twisting operation, when the twisted pair  120  is formed. 
       FIG. 13  is a close-up cross sectional view of a twisted pair  130 , having a dielectric tape  131  with an alternative shape, in accordance with a seventh embodiment of the present invention. The dielectric tape  131  has a width which extends approximately perpendicular to an extension length of the twisted pair  130  from a first edge  132  of the dielectric tape  131  to a second edge  133  of the dielectric tape  131 . The dielectric tape  131  has a cross sectional shape in a direction perpendicular to an extension length of the twisted pair  130 , which presents a first recessed portion  135  for seating the first insulated conductor  88  and a second recessed portion  136  for seating the second insulated conductor  90 . 
     The first edge  132  of the first dielectric tape  131  in  FIG. 13  will circumscribe an area  105  around the first twisted pair  130 , which includes the small air gaps  107 . However, the width of the first dielectric tape  131  is only slightly more than one-half the width of the dielectric tape  89  in the embodiment of  FIGS. 9-11 .  FIG. 14  illustrates a cable  140  with a jacket  141 , wherein the first twisted pair  130  is stranded with three other similarly-configured twisted pairs, namely a second twisted pair  142 , a third twisted pair  143  and a fourth twisted pair  144 . 
     Some of the advantages of the seventh embodiment of  FIGS. 13 and 14  over the fifth embodiment of  FIGS. 9-11  are that the material cost, and the weight of the cable  140  can be reduced. Yet, the seventh embodiment of  FIGS. 13 and 14  will still create the small air gaps  107 , primarily due to the tight twist lengths of the first through fourth twisted pairs  130 ,  142 ,  143  and  144 . 
       FIG. 15  is a close-up cross sectional view of a twisted pair  150 , having a dielectric tape  151  with an alternative shape, in accordance with a eighth embodiment of the present invention. The eighth embodiment is identical to the seventh embodiment of  FIGS. 13 and 14 , except that the dielectric tape  151  does not have recessed seats  135  and  136  to seat the first and second insulated conductors  88  and  90 . Rather, the dielectric tape  151  has a substantially rectangular cross sectional shape. The dielectric tape  151  will remain between the first and second insulated conductors  88  and  90  due to the frictional forces created during the twisting operation, when the twisted pair  150  is formed. 
       FIG. 16  is a close-up cross sectional view of a twisted pair  160 A, having a dielectric tape  161 A with an alternative shape, in accordance with a ninth embodiment of the present invention. The ninth embodiment includes a first insulated conductor  88 , a first dielectric tape  161 A, and a second insulated conductor  90 . The first insulated conductor  88  is twisted with the second insulated conductor  90  with the first dielectric tape  161 A residing between the first insulated conductor  88  and the second insulated conductor  90  to form the twisted pair  160 A. The dielectric tape  161 A has a width which extends approximately perpendicular to an extension length of the twisted pair  160 A from a first edge  162  of the dielectric tape  161 A to an opposing second edge  163  of the dielectric tape  161 A. The width, in the embodiment of  FIG. 16 , is equal to or less than the diameter of the first insulated conductor  88 . 
     The embodiment of  FIG. 16  is similar in most regards to the embodiment of  FIG. 8 , but illustrates that the dielectric tape  161 A may include a plurality of ridges  164 A and valleys  165 A on at least a first side of the first dielectric tape  161 A facing to the first insulated conductor  88 . In a preferred embodiment, the first dielectric tape  161 A includes a plurality of ridges  164 A and valleys  165 A on both the first side of the first dielectric tape  161 A facing to the first insulated conductor  88  and on a second side of the first dielectric tape  161 A facing to the second insulated conductor  90 . 
     The insulation layers R of the first and second insulated conductors  88  and  90  engage the ridges  164 A, so that the valleys  165 A introduces air immediately adjacent to the insulation layers R of the first and second insulated conductors  88  and  90 . Air has a dielectric constant of approximately 1.0, and the introduction of air close to the insulation layers R improves the overall dielectric constant of the first dielectric tape  161 A, e.g., reduces the overall dielectric constant of the first dielectric tape  161 A. 
     In  FIG. 16 , the plurality of ridges  164 A are shaped in the form of angled peaks, and the plurality of valleys  165 A are shaped in the form of angled valleys. The actual shapes of the ridges and/or valleys are not critical. Rather, an important aspect is the introduction of air into the first and second surfaces of the first dielectric tape  161 A, which contact the first and second insulated conductors  88  and  90 . 
       FIG. 17  is a close-up cross sectional view of a twisted pair  160 B, having a dielectric tape  161 B with an alternative shape, in accordance with a tenth embodiment of the present invention. The tenth embodiment is the same as the ninth embodiment, except that the plurality of ridges  164 B are shaped in the form of rectangular protrusions, and the plurality of valleys  165 B are shaped in the form of rectangular recesses. 
       FIG. 18  is a close-up cross sectional view of a twisted pair  160 C, having a dielectric tape  161 C with an alternative shape, in accordance with an eleventh embodiment of the present invention. The eleventh embodiment is the same as the ninth and tenth embodiments, except that the plurality of ridges  164 C are shaped in the form of curved protrusions, and the plurality of valleys  165 C are shaped in the form of curved recesses. 
       FIG. 19  is a close-up cross sectional view of a twisted pair  160 D, having a dielectric tape  161 D with an alternative configuration, in accordance with a twelfth embodiment of the present invention. The twelfth embodiment is the same as the ninth embodiment, in that the plurality of ridges  164 D are shaped in the form of angled peaks, and the plurality of valleys  165 D are shaped in the form of angled valleys. However, in the twelfth embodiment, the first dielectric tape  161 D is formed of at least two different materials. A first side  168  of the first dielectric tape  161 D, facing to the first insulated conductor  88 , and a second side  167  of the first dielectric tape  161 D, facing to the second insulated conductor  90 , are formed of a first dielectric material. A mid-portion  166  of the first dielectric tape  161 D is formed of a second dielectric material. A first dielectric constant of the first material is different from a second dielectric constant of the second material. In a preferred embodiment, the second dielectric constant is lower than the first dielectric constant. The second material improves the overall dielectric constant of the first dielectric tape  161 D, e.g., reduces the overall dielectric constant of the first dielectric tape  161 D. 
       FIGS. 20 and 20A  are close-up cross sectional views of a twisted pair  160 E, having a dielectric tape  161 E with an alternative configuration, in accordance with a thirteenth embodiment of the present invention. The thirteenth embodiment is the same as the twelfth embodiment, in that the plurality of ridges  164 E are shaped in the form of angled peaks, and the plurality of valleys  165 E are shaped in the form of angled valleys. However, in the thirteenth embodiment, the construction of the first dielectric tape  161 E is different. In  FIG. 20 , the first side  168  of the first dielectric tape  161 E, facing to the first insulated conductor  88  is attached to the second side  167  of the first dielectric tape  161 E, facing to the second insulated conductor  90  along the first edge  162  and along the second edge  166 . 
     Like the embodiment depicted in, and described in relation to  FIG. 5A , the first dielectric tape  161 E has a hollow core which may possess a gas (See  FIG. 20A ), like air  166 A (with a dielectric constant of about 1.0) or, as depicted in  FIG. 20 , a foamed insulation material  166  (with a dielectric constant approaching 1.0). Again, the material  166  would have a lower dielectric constant than a material used to form the remaining portions of the first dielectric tape  161 E. By filling the hollow core with a gas or material with a lower dielectric constant than a material used to form the remaining portions of the first dielectric tape  161 E, the overall dielectric constant of the first dielectric tape  161 E may be reduced. The hollow core may extend the entire length of the dielectric tape  161 E, resulting in a “straw-like” structure. Alternatively, support structures may be formed at intervals IN 1 , IN 2 , IN 3 , . . . along the length of the dielectric tape  161 E to form closed-cell air pockets, each having a short length, such as ½ inch, one inch, two inches, etc., as graphically shown, not to scale, in  FIG. 20B . Alternatively, one or more support structures may be formed within the hollow core, which extend along the length of the dielectric tape  161 E and connect between the first and second sides  168  and  167  of the hollow core to resist crushing of the hollow core during the twisting of the twisted pair  160 E. 
     In cables of the background art, different twist lengths were applied to each of the four twisted pairs. The different twist lengths had the benefit of reducing crosstalk between adjacent pairs within the cable. However, employing different twist lengths also created drawbacks, such as delay skew (e.g., it takes more time for a signal to travel to the far end of the cable on a relatively tighter twisted pair, as compared to a relatively longer twisted pair in the same cable). Differing twist lengths can also cause relative differences between the twisted pairs in such performance characteristics as attenuation and impedance. 
     In the background art, the insulation layers R were varied in thickness and/or material composition to compensate for the differences. For example, the insulation layers R of the insulated conductors  91  and  93  in the tighter twisted pair  84  (in  FIG. 9 ) could be formed of a material with a different dielectric constant than the insulation layers R of the insulated conductors  94  and  96  in the longer twisted pair  85  (in  FIG. 9 ). Also, air could be introduced into the insulation layers R to foam the insulation layers R. The foaming could be set at different levels for one or more of the twisted pairs, depending upon their twist length. 
     Such measures of the background art helped to offset the different performance characteristics induced by the different twist lengths of the twisted pairs. However, there was an added cost in that the insulated conductors used in different twisted pairs of the same cable had to be manufactured differently. This created a need for inventorying different types of insulated conductors and added more complexity in the manufacturing process. 
     In accordance with one embodiment of the present invention, the insulated conductors  38 ,  40 ,  41 ,  43 ,  44 ,  46 ,  47  and  49  of each of the twisted pairs  33 ,  34 ,  35  and  36  in the cable  31  may be made structurally identical (noting that certain non-structural features, like colors, stripe patterns or printed indicia may be employed to merely identify the insulated conductors from each other). In this embodiment of the present invention, the dielectric tape structure can be used to mitigate the performance differences, which arise when different twist lengths are employed in the twisted pairs. Moreover, the insulated conductors  38 ,  40 ,  41 ,  43 ,  44 ,  46 ,  47  and  49  may be made structurally identical and also be identical in appearance. In this embodiment, the color of, or indicia on, the first through fourth dielectric tapes  39 ,  42 ,  45  and  48  could be used to distinguish between the first through fourth twisted pairs  33 ,  34 ,  35  and  36  of the cable  31 , when the cable  31  is terminated and a connector is attached thereto. 
     For example, the dielectric tape of one twisted pair of a given cable may be different in shape, size or material content as compared to the dielectric tape of another twisted pair in the same cable. In  FIG. 4 , the first dielectric tape  39  of the first twisted pair  33  has a first thickness, which sets a spacing distance between the first insulated conductor  38  and the second insulated conductor  40 . In the third twisted pair  35 , the third dielectric tape  45  has a second thickness, which sets a spacing distance between the fifth insulated conductor  44  and the sixth insulated conductor  46 . The second thickness is different from the first thickness, which also means that the shape of the first dielectric tape  39  is different than the shape of the third dielectric tape  45 . 
     In one embodiment, the difference between the second thickness and the first thickness is at least 1 mil. For example, the first dielectric tape  39  could have a thickness of about 10 mils, whereas the third dielectric tape  45  could have a thickness of about 8 mils. Such a change in thickness and shape will affect the respective performance characteristics of the first twisted pair  33  and the third twisted pair  35 , such as their respective attenuation, impedance, delay skew, etc. 
     Also in  FIG. 4 , the first dielectric tape  39  of the first twisted pair  33  has a first width, which extends approximately perpendicular to an extension length of said cable  31  from its first edge  51  to its second edge  53  (See  FIG. 5 ). In the fourth twisted pair  36 , the fourth dielectric tape  48  has a second width, which extends approximately perpendicular to the extension length of said cable  31  from its corresponding first edge  51  to its corresponding second edge  53 . The second width is different from the first width. For example, the second width may be several mils shorter than the first width, such as about 2 to 12 mils shorter, e.g., about 5 mils shorter. Again, the respective differences in width will serve to create differences in performance characteristics, which can be adjusted and used to offset for the performance differences created by the different twist lengths. 
     Also in  FIG. 4 , the first dielectric tape  39  of the first twisted pair  33  is formed of a first material having a first dielectric constant. In the second twisted pair  34 , the second dielectric tape  42  is formed of a second material having a second dielectric constant (as illustrated by the different thicknesses in the cross hatching). The second dielectric constant is different from the first dielectric constant. For example, the second dielectric constant could differ from the first dielectric constant by about 0.1 to about 0.8, e.g., the first dielectric constant might be 1.2, whereas the second dielectric constant is 1.4, thus illustrating a difference of 0.2 in dielectric constant between the two materials. Again, the respective differences in material will serve to create differences in performance characteristics, which can be adjusted and used to offset for the performance differences created by the different twist lengths. Of course, the differences between the dielectric tapes can also be employed as a supplemental measure in conjunction with differences in insulation layers on the insulated conductors to provide an additional ability to compensate for performance differences between the twisted pairs. 
     The cables  31 ,  66 ,  81  and  140  of the present invention may be manufactured using standard twisting equipment, such as a double twist twinning machine, known in the art of twisted pair cable making. An additional spool would be added to feed the dielectric tape into the twisting machine between the insulated conductors of the twisted pair. 
     Although, the cables illustrated in the drawing figures have included four twisted pairs, it should be appreciated that the present invention is not limited to cables having only four twisted pairs. Cables having other numbers of twisted pairs, such as one twisted pair, two twisted pairs or even twenty-five twisted pairs, could benefit from the structures disclosed in the present invention. Further, although the drawing figures have illustrated that each of the twisted pairs within the cable have a dielectric tape, it would be possible for less than all of the twisted pairs to have the dielectric tape. For example, the first through third twisted pairs could include a dielectric tape, while the fourth twisted pair could be formed without a dielectric tape. Further, although the drawing figures have illustrated an unshielded cable, it is within the scope of the appended claims that the cable could include a shielding layer and/or a core wrap between the core of twisted pairs and the inner wall of the outermost jacket. Further, although some drawing figures have illustrated a jacket having a smooth inner wall, it is within the scope of the present invention that in all embodiments the inner wall of the jacket could include fins or projections (as illustrated in  FIG. 8B ) for creating air pockets around the perimeter of the core of twisted pairs. Further, all embodiments of the present invention may include a separator (e.g., tape, isolator, flute, crossweb). 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.