Patent Publication Number: US-2022223317-A1

Title: Low dielectric constant structures for cables

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a divisional filing of U.S. application Ser. No. 17/259,053, filed Jan. 8, 2021, now allowed, which is a national stage filing under 35 C.F.R. 371 of PCT/IB2019/055836, filed Jul. 9, 2019, which claims the benefit of U.S. Provisional Application No. 62/696,501, filed Jul. 11, 2018, the disclosures of which are incorporated by reference in their entireties herein. 
    
    
     BACKGROUND 
     Electrical cables for transmission of electrical signals are well known. One common type of electrical cable is a coaxial cable. Coaxial cables generally include an electrically conductive wire surrounded by an insulating material. The wire and insulator are surrounded by a shield, and the wire, insulator, and shield are surrounded by a jacket. Another common type of electrical cable is a shielded electrical cable that includes one or more insulated signal conductors surrounded by a shielding layer formed, for example, by a metal foil. 
     SUMMARY 
     In some aspects of the present description, a ribbon cable is provided, including a plurality of conductors extending along a length of the cable; and a structured insulative tape including a plurality of spaced apart supports forming alternating first and second groups of supports disposed on a major surface thereof. Each first group of supports includes at least one taller first support, and each second group of supports includes at least one shorter second support. The insulative tape is helically wrapped around the conductors along the length of the cable such that each first group of supports is disposed between and maintains a minimum separation between two adjacent conductors, and each of the two adjacent conductors makes contact with a side of the taller first support. Each second group of supports is disposed around one or more conductors, such that each of the conductors makes contact with a top of the at least one shorter support. 
     In some aspects of the present description, a conductor set is provided, including a plurality of conductors, a structured insulative tape including a plurality of spaced apart supports forming alternating first and second groups of supports disposed on a major surface thereof, and an electrically conductive shield substantially surrounding the plurality of conductors and the structured insulative tape. Each first group of supports includes at least one taller first support, and each second group of supports includes at least one shorter second support. The insulative tape is helically wrapped around the conductors along the length of the cable such that each first group of supports is disposed between and maintains a minimum separation between two adjacent conductors, and each of the two adjacent conductors makes contact with a side of the taller first support. Each second group of supports is disposed around one or more conductors, such that each of the conductors makes contact with a top of the at least one shorter support. 
     In some aspects of the present description, a shielded electrical cable is provided, including a plurality of spaced apart, substantially parallel conductor sets extending along a length of the cable and arranged along a width of the cable. Each conductor set includes two substantially parallel conductors extending along the length of the cable and arranged along the width of the cable, and a structured insulative tape helically wrapped around the conductors of each conductor set along the length of the cable. The structured insulative tape includes a plurality of spaced apart first and second supports disposed on an inner major surface thereof facing the two conductors. Each first support is taller than each second support, and each first and second support extend substantially from a first lateral edge of the structured insulative tape to an opposite second lateral edge of the structured insulative tape. The first supports are disposed between and maintain a minimum separation between the two conductors, such that the two conductors make contact with opposite sides of the first supports, the second supports disposed around the two conductors and maintaining a minimum separation between the two conductors and the inner major surface of the structured insulative tape, the two conductors making contact with tops of the second supports. 
     In some aspects of the present description, a ribbon cable is provided, including a plurality of spaced apart, substantially parallel uninsulated conductors extending along a length of the cable and arranged along a width of the cable, a structured insulative tape including a plurality of spaced apart supports of equal heights integrally formed on a major surface thereof, and a spacer disposed and maintaining a minimum separation between each pair of adjacent uninsulated conductors along the length of the cable. The insulative tape is helically wrapped around the plurality of the uninsulated conductors along the length of the cable such that, for each helical wrap, each uninsulated conductor makes contact with a top of at least one support. The spacer makes contact with both uninsulated conductors and is not integrally formed with the insulative tape or either one of the uninsulated conductors. 
     In some aspects of the present description, a ribbon cable is provided, including a plurality of spaced apart, substantially parallel uninsulated conductors extending along a length of the cable and arranged along a width of the cable, an insulative tape helically wrapped around the uninsulated conductors along the length of the cable, and a spacer disposed and maintaining a minimum separation between each pair of adjacent uninsulated conductors along the length of the cable. For each helical wrap, each uninsulated conductor makes contact with the insulative tape. The spacer makes contact with both uninsulated conductors and is not integrally formed with the insulative tape or either one of the uninsulated conductors. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view of an electrical cable in accordance with an embodiment of the invention; 
         FIG. 1B  is a perspective view of a structured insulative tape in accordance with an embodiment of the invention; 
         FIG. 1C  is a top view of a structured insulative tape in accordance with an embodiment of the invention; 
         FIG. 2A  is a perspective view of an electrical cable in accordance with an embodiment of the invention; 
         FIG. 2B  is a side, profile view of a structured insulative tape in accordance with an embodiment of the invention; 
         FIG. 3A-3B  are cross-sectional views of an electrical cable in accordance with an embodiment of the invention; 
         FIGS. 4A-4B  are cross-sectional views of an electrical cable in accordance with an embodiment of the invention; 
         FIG. 4C  is a perspective view of an insulative tape in accordance with an embodiment of the invention; 
         FIGS. 5A-5B  are cross-sectional views of an electrical cable in accordance with an embodiment of the invention; 
         FIG. 6A  is an illustrative view demonstrating various widths of structured insulative tape wrapped around an electrical cable in accordance with an embodiment of the invention; 
         FIG. 6B  is an illustrative view illustrating various wrap angles which can be used with a structured insulative tape wrapped around an electrical cable in accordance with an embodiment of the invention; and 
         FIG. 7  is an illustrative view demonstrating various heights and widths of support structures which may be used with an electrical cable in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, reference is made to the accompanying drawings that form a part hereof and in which various embodiments are shown by way of illustration. The drawings are not necessarily to scale. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present description. The following detailed description, therefore, is not to be taken in a limiting sense. 
     According to some aspects of the present description, electrical cables incorporating the structures described herein have been found to provide improved performance over conventional cables. For example, the electrical cables may have one or more of a reduced impedance variation along the cable length, lower skew, lower propagation delay, lower insertion loss, increased crush resistance, reduced cable size, increased conductor density, and improved bend performance compared to conventional cables. 
     In some embodiments, an electrical cable is constructed by creating a planar three-dimensional (3D) structured dielectric and then wrapping the structured dielectric helically around two or more signal conductors. The structured dielectric may be an insulative tape featuring a series of supports of varying heights. When the structured dielectric is wrapped around two or more conductors, the supports may provide precise spacing between adjacent conductors, as well as precise spacing between the conductors and a shielding film placed around the conductors, incorporating air into the cable as well as providing crush resistance. The supports may have a low effective dielectric constant and/or a low dielectric loss (e.g., low effective loss tangent). For example, the supports may have a high air (or other low dielectric constant material) content to provide the low effective dielectric constant. The supports may be a porous material with air in the voids. In some embodiments, the air content of the supports may be greater than 40%. 
     In some embodiments, each of the supports may have a dielectric constant of less than about 2, or less than about 1.7, or less than about 1.6, or less than about 1.5, or less than about 1.4, or less than about 1.3, or less than about 1.2. In some embodiments, an dielectric constant of the cable for at least one pair of adjacent conductors driven with differential signals of equal amplitude and opposite polarities is less than about 2.5, or less than about 2.2, or less than about 2, or less than 1.7, or less than about 1.6, or less than about 1.5, or less than about 1.4, or less than about 1.3, or less than about 1.2. The dielectric constant of the supports may be in any of the specified ranges when determined at an operating frequency of the cable and/or when determined at a frequency of 100 MHz, 1 GHz, or 10 GHz, for example. 
     The conductors may include any suitable conductive material, such as an elemental metal or a metal alloy (e.g., copper or a copper alloy), and may have a variety of cross sectional shapes and sizes. For example, in cross section, the conductors may be circular, oval, rectangular or any other shape. One or more conductors in a cable may have one shape and/or size that differs from other one or more conductors in the cable. The conductors may be solid or stranded wires. All the conductors in a cable may be stranded, all may be solid, or some may be stranded and some solid. Stranded conductors and/or ground wires may take on different sizes and/or shapes. The conductors may be coated or plated with various metals and/or metallic materials, including gold, silver, tin, and/or other materials. 
     In some embodiments, the supports may be adhered to the insulative tape of the structured dielectric. The supports may be placed such that, when the structured dielectric is helically wrapped around two or more conductors, a first subset of the supports is disposed between and maintains a minimum separation between adjacent conductors, and a second subset of the supports is disposed between each conductor and a surrounding shielding film. In some embodiments, the first subset of supports may be taller than the second subset of supports. 
     In some embodiments, one or more separate spacers may be used to separate adjacent conductors in addition to the supports of the structured dielectric. The spacers may be separately formed from the structured dielectric, and may be held in place by the conductors. In some embodiments, the spacers may be placed between adjacent conductors and then adhered to a structured dielectric which is helically wrapped around the conductors in the process of forming the electrical cable. In some embodiments, a spacer may be used in place of supports to separate adjacent conductors. The spacers may be made of a material which has a low effective dielectric constant and/or a low dielectric loss. For example, the spacers may have a high air content to provide the low effective dielectric constant. 
     In some embodiments, the cable can be produced with high uniformity to maintain a constant impedance, and related data transmission performance along a single transmission path or among cables of the same design manufactured at different times. In some embodiments, the spacing between conductors (e.g., center-to-center spacing) in the cable can be different (e.g., smaller) than the spacing in a direction orthogonal to the plane of the conductors between the shields included in the cables. This can allow for a high density of conductors in the cable, for example, which is highly desirable in some cases. 
     In some embodiments, the conductors of the cable are insulated with a dielectric layer. In some embodiments, incorporating low effective dielectric constant materials or structures in the insulative layer(s) of the cable allows the thickness of the dielectric layer to be smaller than that of conventional cables while providing a desired cable impedance (e.g., a differential impedance in a range of 70 ohms to 110 ohms). For example, conventional cables typically have a ratio of a diameter of the insulated conductor to the diameter of the conductor of the insulated conductor substantially greater than 2 (e.g., about 2.8 or higher), while this ratio for cables of the present description having the same impedance can be less than about 2 in some embodiments. 
     In some embodiments, an electrically conductive shield may be wrapped or otherwise placed around the conductors and structured dielectric. The shield may include an electrically conductive shielding layer disposed on an electrically insulative substrate layer. In some embodiments, the shield may include a first shield disposed on a top side of the electrical cable and a second shield disposed on a bottom side of the electrical cable. The shield may include cover portions and pinched portions, such that the cover portions create a channel or pocket which substantially surround and contain the conductors and structured dielectric, and the pinched portions are portions where the first and second shields are pushed together or nearly together and which may not contain conductors and structured dielectric. 
       FIGS. 1A-1C  illustrate an electrical cable with structured insulative tape in accordance with an embodiment of the invention.  FIG. 1A  is a perspective view of a ribbon cable  100  including a plurality of electrical conductors  10  extending along a length of the cable (e.g., in the x-direction of  FIG. 1A ), and a structured insulative tape  20  wrapped helically around the plurality of conductors  10  along the length of ribbon cable  100 . The structured insulative tape  20  comprises a plurality of supports  30  of variable heights and dimensions disposed on a major surface  21  of the structured insulative tape  20 . In some embodiments, a conductive shield  60  is wrapped around or otherwise encloses the conductors  10  and structured insulative tape  20 . 
       FIG. 1B  is a perspective view of a portion of the structured insulative tape  20  of  FIG. 1A  before it has been wrapped around conductors  10 . In some embodiments, the plurality of supports  30  forms alternating first groups of supports  31  and second groups of supports  32  disposed on a major surface  21  of the structured insulative tape  20 . In some embodiments, each first group of supports  31  includes at least one taller first support  30   a , and each second group of supports  32  includes at least one shorter second support  30   b . In some embodiments, each first group of supports  31  includes a single taller first support  30   a , and each second group of supports  32  includes at least two spaced apart shorter second supports  30   b . In some embodiments, each first group of supports  31  includes a single taller first support  30   a , and at least one other first group of supports  31  includes two taller first supports  30   a . In some embodiments, at least one second group of supports  32  includes a single shorter second support  30   b , and at least one second group of supports  32  includes at least two shorter second supports  30   b . The embodiments described are exemplary only and are not limiting in any way. Each first group of supports  31  may contain any appropriate number of taller first supports  30   a , including but not limited to 1, 2, 4, 6, or 10, and each second group of supports  32  may contain any appropriate number of shorter second supports  30   b , including but not limited to 1, 2, 4, 6, or 10. 
     When the structured insulative tape  20  is wrapped helically around conductors  10 , as illustrated in  FIG. 1A , each taller first support  30   a  extends up between and maintains a precise separation between adjacent conductors  10 , such that each of the two adjacent conductors  10  make contact with a side  35  of the taller first support  30   a . When the structured insulative tape  20  is wrapped helically around conductors  10 , each shorter second support  30   b  is positioned such that it provides support for the conductors  10  and maintains a precise separation between conductors  10  and the major surface  21  of structured insulative tape  20  and/or conductive shield  60 , such that each of the conductors  10  makes contact with a top side  36  of a shorter second support  30   b.    
       FIG. 1C  is a top view of a portion of the structured insulative tape  20  of  FIG. 1B . The structured insulative tape  20  includes a plurality of supports  30  disposed on a major surface  21  of the structured insulative tape  20 . The major surface  21  may be the top film of a backing layer constructed of a polyester, a Mylar, or any appropriate backing material. In some embodiments, supports  30  extend from a first lateral edge  22  to a second lateral edge  23  of the major surface  21 . In other embodiments, supports  30  may extend only part way across the width of the major surface  21 . The placement of the supports  30  on the major surface  21  may be such that an angle, A 1 , of the supports  30  corresponds to a wrap angle of the structured insulative tape  20  when it is helically wrapped around conductors  10 . In some embodiments, the major surface  21  may be formed by a separate process than that used to create the supports  30 , and the supports  30  may be adhered to the major surface  21  by an adhesive. In other embodiments, major surface  21  and supports  30  may be created in a single process as a single, cohesive structure. In yet other embodiments, a first subset of supports  30  may be adhered to or otherwise integral to major surface  21 , while a second subset of supports  30  may be separate components. For example, in an embodiment, shorter second supports  30   b  ( FIG. 2 ) may be adhered to major surface  21 , and taller first supports  30   a  may be standalone components placed between adjacent conductors  10  before the structured insulative tape  20  is wrapped around the conductors  10 . 
       FIGS. 2A-2B  illustrate an electrical cable with structured insulative tape in accordance with an alternate embodiment of the invention.  FIG. 2A  is a perspective view of an embodiment of a ribbon cable  100  including a plurality of electrical conductors  10  extending along a length (e.g., in the x-direction of  FIG. 2A ) of the cable and a structured insulative tape  20  wrapped helically around the plurality of conductors  10  along the length of ribbon cable  100 . The plurality of electrical conductors  10  are arranged along a width (e.g., in the y-direction of  FIG. 2A ) of the cable  100 . Although the example of  FIG. 2A  includes four conductors (e.g., two inner signal wires and two outer ground/drain wires), any appropriate number of conductors may be used, including but not limited to 1, 2, 3, 4, 6, 8, 12, 25, or 50 conductors. The structured insulative tape  20  comprises a plurality of supports  30   a  and  30   b  disposed on a structured insulative tape  20 . In some embodiments, a conductive shield  60  is wrapped around or otherwise encloses conductors  10  and structured insulative tape  20 . 
     As described elsewhere, one or more taller first supports  30   a  extend up between and maintain a precise separation between adjacent conductors  10 , and one or more shorter second supports  30   b  are positioned such that they provide support for conductors  10  and maintain a precise separation between conductors  10  and conductive shield  60 . The structured insulative tape  20  has a defined width W and a projected width W′ along the length of the cable and is wrapped around the conductors  10  at a pitch P, where P is defined as the distance from a lateral edge  22  of one wrap of the structured insulative tape  20  to the same lateral edge  22 ′ of the immediately successive (adjacent) wrap of the structured insulative tape  20 . The structured insulative tape  20  is helically wrapped around conductors  10  such that a difference between the projected width W′ and pitch P defines a helical gap G between adjacent wraps of the structured insulative tape  20 . In various embodiments, the width W and pitch P can be varied to create different helical gaps G. By increasing the helical gap G, it may be possible to increase the air content of ribbon cable  100  (i.e., create a lower effective dielectric constant and/or a lower dielectric loss). In an embodiment, the helical gap G may be greater than or equal to two times the width W of structured insulative tape  20 . In some embodiments, the helical gap G may be greater than the projected width W′ by at least a factor of 2. In another embodiment, helical gap G may be less than equal to zero (i.e., the pitch P may be adjusted such that successive adjacent wraps of structured insulative tape  20  touch or overlap each other, greatly reducing or eliminating helical gap G. Any appropriate width W, pitch P, and gap G may be used, depending on the desired electrical and physical properties of the ribbon cable  100 . 
     In some embodiments, the heights of second supports  30   b  may be substantially equal throughout the length of structured insulative tape  20 , such that a consistent spacing is maintained between conductors  10  and outer conductive shield  60 . In other embodiments, the heights of second supports  30   b  may be varied over the length of structured insulative tape  20 , such that the spacing between a first subset of the conductors  10  and the conductive shield  60  is different than the spacing between a second subset of the conductors  10  and the conductive shield  60 . For example, in the four-conductor example of  FIG. 2A , the two inner wires may be differential signal wires carrying data, and the two outer wires may be a ground/drain wires. It may be desirable in some embodiments to reduce or eliminate the spacing between the outer drain wires and the conductive shielding  60  to allow the drain wires to be more strongly electrically coupled. 
       FIG. 2B  provides a side, profile view of two different structured insulative tapes  20   a  and  20   b  illustrating this concept. In both embodiments of the structured illustrative tape  20   a / 20   b , as described elsewhere, the supports form alternating first groups of supports  31  and second groups of supports  32  disposed on a major surface  21  of the structured insulative tape  20 . Each first group of supports  31  includes at least one taller first support  30   a , and each second group of supports  32  includes at least one shorter second support  30   b . In structured insulative tape  20   a  (top), each of supports  30   b  is substantially equal in height, providing consistent spacing between conductors and the conductive shield throughout when the structured insulative tape  20   a  is wrapped helically around the conductor sets. In the alternate embodiment of structured insulative tape  20   b  (bottom), the height of the second supports  30   b  in subgroup  32   a  is significantly reduced or entirely removed, such that any of the conductors which are located in  32   a  will be spaced closer to conductive shield  60  once the structured insulative tape  20   b  is helically wrapped around the conductor set. In this example, the area  32   a  of structured insulative tape  20   b  with the reduced or missing supports  30   b  may correspond to the outer conductors in the example of  FIG. 2A . 
     Although the examples presented herein discuss varying the heights of or eliminating second supports  30   b , the same principles may be applied to taller first supports  30   a , as well. Various embodiments may use any number of sizes or shapes of supports  30  (including taller first supports  30   a  and shorter second supports  30   b ) to meet different ribbon cable design requirements. Supports  30  may be any appropriate shape, including, but not limited to, cylindrical, rectangular, pyramidal, spherical, hemispherical, and cross-shaped. Supports  30  may be solid forms or hollow to increase air content in the structures. In one embodiment, the heights of taller first supports  30   a  may be such that the tops of supports  30   a  extend up from the structured insulative tape  20  to a point past the conductors it is between. In another embodiment, the heights of taller first supports  30   a  may only extend up through a fraction of the diameter of the conductors, such as 10%, 25%, 50%, 75%, or 90% of the diameter of the conductors, or any other appropriate percentage of the diameter of the conductors. In an embodiment, the height of taller first supports  30   a  may be substantially equal to the height of shorter second supports  30   b.    
       FIG. 3A-3B  are cross-sectional views of an alternate embodiment of an electrical cable  100  in which a spacer  90  which is not integrally formed with the structured insulative tape  20  is used to separate and maintain spacing between adjacent conductors  10 . As used herein, a first element “integrally formed” with a second element means that the first and second elements are manufactured together rather than manufactured separately and then subsequently joined. Integrally formed includes manufacturing a first element followed by manufacturing the second element on the first element. Integrally formed also includes manufacturing a first element with projected features in a single manufacturing step, such as, for example, molding a flat tape including a series of projected supports as a single, homogeneous component. 
     Turning to  FIG. 3A , a ribbon cable  100  includes a plurality of spaced apart substantially parallel uninsulated conductors  10  extending along a length of the cable  100  and arranged along a width of the cable  100 , and a structured insulative tape  20  comprising a plurality of spaced apart supports  30  of equal heights integrally formed on a major surface  21  thereof, the structured insulative tape  20  helically wrapped around the plurality of the uninsulated conductors  10  along the length of the cable  100  such that for each helical wrap, each uninsulated conductor  10  makes contact with a top of at least one support  30 . The ribbon cable  100  further includes a spacer  90  disposed and maintaining a minimum separation between each pair of adjacent uninsulated conductors  10  along the length of the cable, the spacer  90  making contact with both uninsulated conductors  10  and not integrally formed with the structured insulative tape  20  or either one of the uninsulated conductors  10 . The structured insulative tape  20  may be manufactured with an alternating pattern of groups of supports  30  and gaps  33 . The spacer  90  may include opposing first sides  93 , each first side  93  making contact with one of the uninsulated connectors  10 , and opposing second sides  94 , each second side  94  disposed within a gap  33  defined by two adjacent supports  30 . 
     This spacer  90  is initially a separate component which may in some embodiments be held in place by the conductors and pressure from the surrounding structured insulative tape  20  without requiring additional adhesion to the conductors  10  or tape  20 . In other embodiments, the spacer  90  may be placed in between conductors  10  and adhered to conductors  10 , structured insulative tape  20 , and/or supports  30  in a separate process. The spacers may be made of a material which has a low effective dielectric constant and/or a low dielectric loss. For example, the spacers may have a high air content to provide the low effective dielectric constant. 
     In the embodiment of  FIG. 3B , the spacer  90  includes opposing first sides  91  shaped to conformingly make contact with insulated conductors  10 , and opposing second sides  92  making contact with the structured insulative tape  20 . In an embodiment, each first sides  91  may be a concave cylindrical arc and each second side  92  may be substantially flat. In the embodiment of  FIG. 3B , spacer  90  is shaped and sized such that the overall height of ribbon cable  100  is defined by the height of spacer  90  and supports  30 . That is, spacer  90  is held in place by conductors  10  on concave first sides  91  and supports  30  on substantially flat sides  92 . In the embodiment shown, the structured insulative tape  20  would have a periodic arrangement of supports  30  covering substantially the entire length of structured insulative tape  20 . 
     In some embodiments, the length L of spacer  90  of  FIG. 3A  or  FIG. 3B  may be substantially equal to the length of ribbon cable  100 . That is, spacer  90  may be a continuous piece disposed between and separating conductors  10  for substantially the entire length of conductors  10  or ribbon cable  100 , with no gaps. In other embodiments, spacer  90  may comprise a plurality of shorter, separate subsections, wherein the length L of each subsection is less than the length of ribbon cable  100 , spaced apart from each other along the length of ribbon cable  100 , such that the separate subsections alternate with pockets of air to create areas of lower dielectric constant along the length of ribbon cable  100 . 
       FIGS. 4A-4B  are cross-sectional views of an alternate embodiment of an electrical cable  100  in which an insulative tape  20   a  and a separate spacer  90  provide the structure and support for a ribbon cable  100 .  FIG. 4C  provides a perspective view of the insulative tape  20   c  of  FIGS. 4A-4B , illustrating that insulative tape  20   c  does not have projected support structures (such as supports  30  of  FIG. 1A ). Instead of supports, insulative tape  20   c  may be a solid dielectric or a flat tape structure that contains air or a foamed material with a low dielectric constant. In an embodiment, insulative tape  20   c  may be wrapped helically around conductors  10  for the length of ribbon cable  100 , and conductors  10  may be separated by one or more spacers  90 . In the embodiments of  FIGS. 4A and 4B , spacing between conductors  10  and an outer conductive shield (not shown) is provided by the thickness T of insulative tape  20   c , rather than from supports (such as supports  30  of  FIG. 1A ). 
     In the embodiment of  FIG. 4A , spacer  90  may be have a cylindrical shape, and may be placed between adjacent conductors  10  to provide and maintain a spacing between the conductors  10 . In some embodiments, spacer  90  may be a continuous piece disposed between and separating conductors  10  for substantially the entire length of conductors  10  or ribbon cable  100 , with no gaps. In other embodiments, spacer  90  may comprise a plurality of shorter, separate subsections, wherein the length L of each subsection is less than the length of ribbon cable  100 , spaced apart from each other along the length of ribbon cable  100 , such that the separate subsections alternate with pockets of air to create areas of lower dielectric constant along the length of ribbon cable  100 . In other embodiments, spacer  90  may have alternate shapes, such as the shape illustrated in  FIG. 4B . Although two example shapes for spacer  90  are illustrated in  FIGS. 4A and 4B , these examples are not meant to be limiting. Any appropriate shape, size, and length of spacer  90  may be used to provide spacing between adjacent conductors  10 . 
     In some embodiments, spacer  90  may be held in place by contact with conductors  10  and/or insulative tape  20   c , which may be wrapped helically around conductors  10 . In some embodiments, an outer conductive shield and/or a cable jacket (not shown) may surround and contain conductors  10 , spacer  90 , and insulative tape  20   c . In other embodiments, an adhesive may be applied between spacer  90  and insulative tape  20   c  and/or conductors  10  to hold ribbon cable  100  together. 
     As illustrated in  FIGS. 1A and 2A , some embodiments of ribbon cable  100  may have one or more electrically conductive shields  60  substantially surrounding conductors  10  and structured insulative tape  20  (e.g., the one or more electrically conductive shields  60  may surround at least 60% or at least 80% or a perimeter of the conductors  10  and insulative tape  20 , or may completely surround the conductors  10  and insulative tape  20 ). The conductive shield  60  may be composed of braided strands of metal, a spiral winding of metallic tape, a conductive polymer film, or any other appropriate conductive shielding material. In some embodiments, the conductive shield  60  may be enclosed within a protective jacket (not shown), which provides protection for the ribbon cable  100  from items which may damage the cable, such as, for example, moisture, mechanical damage, fire, and chemical exposure. In some embodiments, the purpose of a conductive shield  60  is to reduce or eliminate electrical noise from external sources, and to reduce the electromagnetic radiation produced by the ribbon cable  100 . In some embodiments, the conductive shield  60  may also act as a return path for a data signal propagating through conductors  10 . In some embodiments, the conductive shield  60  may include an electrically conductive shielding layer disposed on an electrically insulative substrate layer. 
     In some embodiments, the conductive shield  60  may be longitudinally wrapped around ribbon cable  100 . In other embodiments, conductive shield  60  may be helically wrapped around ribbon cable  100 . In still other embodiments, conductive shield  60  may include a first and second shield layer disposed respectively on top and bottom sides of ribbon cable  100 .  FIG. 5A  illustrates a cross-sectional view of an electrical cable in accordance with an embodiment of the invention, wherein conductive shield  60  includes a first shield layer  60   a  and a second shield layer  60   b  disposed on opposing sides of ribbon cable  100 . Each shield layer  60   a  and  60   b  may include an electrically conductive shielding layer  76  disposed on an electrically insulative substrate layer  78 . 
     The conductive shielding layer  76  may include any suitable conductive material, including but not limited to copper, silver, aluminum, gold, and alloys thereof. The electrically insulative substrate layer  78  may be an electromagnetic interference (EMI) absorbing layer. For example, electrically insulative substrate layer  78  may include EMI absorbing filler material (e.g., ferrite materials). Alternatively, or in addition, in some embodiments, one or more separate EMI absorbing layers are included. The conductive shielding layer  76  and electrically insulative substrate layer  78  may have a thickness in the range of 0.01 mm to 0.05 mm and the overall thickness of the cable may be less than 2 mm or less than 1 mm. 
     Shield layers  60   a  and  60   b  are disposed on respective top and bottom sides of ribbon cable  100  such that they include cover portions  72  and pinched portions  74 . Cover portions  72  of first shield layer  60   a  and second shield layer  60   b  are aligned or otherwise arranged with respect to each other such that, in combination, they surround ribbon cable  100 . Similarly, pinched portions  74  of first shield layer  60   a  and second shield layer  60   b  are aligned or otherwise arranged to form pinched portions  74  in shield  60 , substantially enclosing and isolating conductors  10  and structured insulative tape  20 . In some embodiments, an adhesive may be used between the pinched portions  74  of first shield layer  60   a  and second shield layer  60   b . One or more taller first supports  30   a  extend up from structured insulative tape  20 , maintaining precise spacing between conductors  10 , and one or more shorter second supports  30   b  provide and maintain spacing between conductors  10  and shield  60 . 
       FIG. 5B  illustrates a cross-sectional view of a shielded electrical cable in accordance with an embodiment of the invention. The shielded electrical cable  100  includes a plurality of spaced apart substantially parallel conductor sets  40  extending along the length of the cable  100  and arranged along the width of the cable  100 . In some embodiments, each conductor set  40  includes two or more substantially parallel conductors  10  extending along the length of the cable  100  and arranged along the width of the cable  100 . In some embodiments, at least one of the conductors  10  in at least one conductor set  40  is an uninsulated conductor. In some embodiments, at least one of the conductors  10  in at least one conductor set  40  is an insulated conductor. A structured insulative tape  20  is helically wrapped around the two or more conductors  10  of each conductor set  40  along the of the cable  100 , the structured insulative tape  20  including a plurality of spaced apart first supports  30   a  and second supports  30   b  disposed on an inner major surface  21  facing the two or more conductors  10 , each first support  30   a  taller than each second support  30   b , each first support  30   a  and each second support  30   b  extending substantially from a first lateral edge of the structured insulative tape (see  22 ,  FIG. 1C ) to an opposite second lateral edge of the structured insulative tape (see  23 ,  FIG. 1C ), each first support  30   a  disposed between and maintaining a minimum separation between two adjacent conductors  10  in a conductor set  40 , the two adjacent conductors  10  making contact with opposite sides of the first support  30   a , and each shorter support  30   b , disposed between the two or more conductors  10  and maintaining a minimum separation between the two or more conductors and a major surface (such as surface  21 ,  FIG. 1B ) of the structured insulative tape  20 , the two or more conductors making contact the tops of the second supports  30   b.    
     In an embodiment, two or more conductor sets  40  share a common shield  60 . The shield  60  includes a first shield layer  60   a  and a second shield  60   b , disposed on respective top and bottom sides of conductor sets  40 . Each shield layer  60   a  and  60   b  includes an electrically conductive shielding layer  76  disposed on an electrically insulative substrate layer  78 . Shield layers  60   a  and  60   b  are disposed on respective top and bottom sides of ribbon cable  100  such that they include cover portions  72  and pinched portions  74 . Cover portions  72  of first shield layer  60   a  and second shield layer  60   b  are aligned or otherwise arranged with respect to each other such that, in combination, they surround a conductor set  40 . Similarly, pinched portions  74  of first shield layer  60   a  and second shield layer  60   b  are aligned or otherwise arranged to form pinched portions  74  in shield  60 , substantially surrounding and isolating each conductor set  40  in ribbon cable  100 . In some embodiments, an adhesive may be used between the pinched portions  74  of first shield layer  60   a  and second shield layer  60   b.    
     In some embodiments, shield  60  includes first and second shields  60   a  and  60   b  disposed on respective top and bottom sides of the ribbon cable  100  and includes cover portions  72  and pinched portions  74  arranged such that, in cross-section, the cover portions  72  of the first and second shields  60   a  and  60   b , in combination, substantially surround the ribbon cable  100 , and the pinched portions  74  of the first and second shields  60   a  and  60   b , in combination, form pinched portions of the conductor set on at least one side of the ribbon cable  100 . In some embodiments, the pinched portions  74  of the first and second shields  60   a  and  60   b , in combination, form the pinched portions  74  of the conductor set  40  on each side of the ribbon cable  100 . In some embodiments, the pinched portions  74  of the first and second shields  60   a  and  60   b , in combination, form the pinched portions of the conductor set  40  only on one side of the ribbon cable  100 . 
     Although the example of  FIG. 5B  shows two conductor sets  40  in ribbon cable  100 , any appropriate number of conductor sets  40  may be included. Each conductor set  40  may have two conductors  10 , as shown, or may have any appropriate number of conductors  10 . For example, a conductor set  40  may have one, two, three, four, six, eight, ten, or twenty conductors  10 . Each conductor set  40  may have the same number of conductors  10 , or one or more of the conductor sets  40  may have a different number of conductors  10 . One or more conductor sets  40  may include an additional conductive shield (not shown) disposed inside the cover portion  72  containing the conductor set  40  and surrounding the conductor set  40 . This additional conductive shield may be longitudinally wrapped or helically wrapped around a conductor set  40 , or may be applied by any appropriate shielding technique. 
       FIGS. 6A-6B  provide illustrative views of how the width and wrap angle of a structured insulative tape can be varied to create electrical cables with different structural and electrical properties.  FIG. 6A  shows three different sets of conductors  10  ( 10   a ,  10   b ,  10   c ) wrapped by structured insulative tapes  20  ( 20   x ,  20   y ,  20   z ). Each structured insulative tape  20  has a set of taller first supports  30   a  that extends from a surface of the tape  20  up between two adjacent conductors  10 , and each structured insulative tape  20  is helically wrapped about the corresponding conductors  10  using the same wrap angle A. However, each structured insulative tape  20  has a different width. Structured insulative tape  20   x  has a width of W 1 , structured insulative tape  20   y  has a width of W 2 , and structured insulative tape  20   z  has a width of W 3 . The various widths W 1 -W 3  and wrap angle A are meant to be illustrative and are not limiting in any way. Any appropriate width and wrap angle may be used. As can be seen in these examples, using a narrower width (for example, width W 2  in  FIG. 6A ) may create a cable that has increased air content (that is, more open space between successive wraps), and therefore a lower dielectric content as compared to a cable using a wider width (for example, width W 3  in  FIG. 6A ). On the other hand, using a wider width tape (e.g., width W 3 ), while reducing open space in the cable, may provide a cable that is more structurally sound (e.g., more resistant to crushing) than the use of a narrower width tape (e.g., width W 2 ). 
       FIG. 6B  shows three different sets of conductors  10  ( 10   d ,  10   e ,  10   f ) wrapped by structured insulative tapes  20  ( 20   u ,  20   v ,  20   w ). Each structured insulative tape  20  has a set of taller first supports  30   a  that extends from a surface of the tape  20  up between two adjacent conductors  10 , and each structured insulative tape  20  is helically wrapped about the corresponding conductors  10 . In the examples of  FIG. 6B , the width WO of each tape  20  is held constant, but the wrap angles are varied. Structured insulative tape  20   u  is wrapped with a wrap angle of A 1 , structured insulative tape  20   v  is wrapped with an angle of A 2 , and structured insulative tape  20   w  is wrapped with an angle of A 3 . As can be seen in these examples, a smaller wrap angle (e.g., angle A 3 ) decreases the amount of open space in the resulting cable and increases the number of taller first supports  30   a  present between adjacent conductors  10 , resulting in a more structurally sound cable when compared to a cable using a larger wrap angle (e.g., angle A 2 ). 
     It should be noted that, for simplicity&#39;s sake, the examples provided do not show shorter second supports or conductive shielding. The intent of  FIGS. 6A and 6B  is to show the effect of varying the width and wrap angle of a structured insulative tape. 
     Finally,  FIG. 7  is an illustrative side view demonstrating various heights and widths of support structures  30   a  which may be used with an electrical cable in accordance with an embodiment of the invention. The examples shown are intended to be illustrative only and are not limiting in any way. The examples show various structured insulative tapes  20  ( 20   q ,  20   r ,  20   s ,  20   t ) with taller first supports  30   a  of various dimensions. For the sake of simplicity, only conductors  10 , structured insulative tape  20 , and taller first supports  30   a  are shown, however, other components may be present. For example, shorter second supports  30   b  ( FIG. 1B ) may be present and provide spacing and support between conductors  10  and major surface  21  of structured insulative tape  20 . 
     In example structured insulative tape  20   q , supports  30   a  are substantially equal in size and placed at regular intervals along major surface  21 . Supports  30   a  extend from surface  21  between conductors  10 , but do not extend past conductors  10 . In example structured insulative tape  20   r , supports  30   a  are similarly spaced as those in tape  20   q , but are longer, extending past conductors  10 . Longer supports  30   a  such as these may be used to provide additional structure to the ribbon cable, providing support for an outer wrap such as a conductive shield or cable jacket. In example structured insulative tape  20   s , supports  30   a  vary in both height and width throughout the length of the resulting ribbon cable. This may be done as required to balance trade-offs such as additional structural support (for example, additional crush resistance) and a lower dielectric constant. Finally, in example structured insulative tape  20   t , supports  30   a  are broad, such that supports  30   a  span the width of major surface  21 . As can be appreciated by one skilled in the art, any appropriate size, shape, and number or supports  30   a  may be used to achieve the desired properties in an electrical cable. 
     Terms such as “about” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “about” as applied to quantities expressing feature sizes, amounts, and physical properties is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “about” will be understood to mean within 10 percent of the specified value. A quantity given as about a specified value can be precisely the specified value. For example, if it is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, a quantity having a value of about 1, means that the quantity has a value between 0.9 and 1.1, and that the value could be 1. 
     Terms such as “substantially” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “substantially equal” is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “substantially equal” will mean about equal where about is as described above. If the use of “substantially parallel” is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “substantially parallel” will mean within 30 degrees of parallel. Directions or surfaces described as substantially parallel to one another may, in some embodiments, be within 20 degrees, or within 10 degrees of parallel, or may be parallel or nominally parallel. If the use of “substantially aligned” is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “substantially aligned” will mean aligned to within 20% of a width of the objects being aligned. Objects described as substantially aligned may, in some embodiments, be aligned to within 10% or to within 5% of a width of the objects being aligned. 
     All references, patents, and patent applications referenced in the foregoing are hereby incorporated herein by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control. 
     Descriptions for elements in figures should be understood to apply equally to corresponding elements in other figures, unless indicated otherwise. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.