Patent Publication Number: US-9419321-B2

Title: Self-supporting stripline RF transmission cable

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of commonly owned co-pending U.S. Utility patent application Ser. No. 13/208,443, titled “Stripline RF Transmission Cable” filed 12 Aug. 2011 by Frank A. Harwath, hereby incorporated by reference in its entirety. This application is also a continuation-in-part of commonly owned co-pending U.S. Utility patent application Ser. No. 13/427,313, titled “Low Attenuation Stripline RF Transmission Cable” filed 22 Mar. 2012 by Frank A. Harwath, hereby incorporated by reference in its entirety, which is a continuation-in-part of U.S. Utility patent application Ser. No. 13/208,443. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     RF Transmission systems are used to transmit RF signals from point to point, for example, from an antenna to a transceiver or the like. Common forms of RF transmission systems include coaxial cables and striplines. 
     2. Description of Related Art 
     Prior coaxial cables typically have a coaxial configuration with a circular outer conductor evenly spaced away from a circular inner conductor by a dielectric support such as polyethylene foam or the like. The electrical properties of the dielectric support and spacing between the inner and outer conductor define a characteristic impedance of the coaxial cable. Circumferential uniformity of the spacing between the inner and outer conductor prevents introduction of impedance discontinuities into the coaxial cable that would otherwise degrade electrical performance. 
     An industry standard characteristic impedance is 50 ohms. Coaxial cables configured for 50 ohm characteristic impedance generally have an increased inner conductor diameter compared to higher characteristic impedance coaxial cables such that the metal inner conductor material cost is a significant portion of the entire cost of the resulting coaxial cable. To minimize material costs, the inner and outer conductors may be configured as thin metal layers for which structural support is then provided by less expensive materials. For example, commonly owned U.S. Pat. No. 6,800,809, titled “Coaxial Cable and Method of Making Same”, by Moe et al, issued Oct. 5, 2004, hereby incorporated by reference in the entirety, discloses a coaxial cable structure wherein the inner conductor is formed by applying a metallic strip around a cylindrical filler and support structure comprising a cylindrical plastic rod support structure with a foamed dielectric layer therearound. The resulting inner conductor structure has significant materials cost and weight savings compared to coaxial cables utilizing solid metal inner conductors. However, these structures can incur additional manufacturing costs, due to the multiple additional manufacturing steps required to sequentially apply each layer of the structure. 
     One limitation with respect to metal conductors and/or structural supports replacing solid metal conductors is bend radius. Generally, a larger diameter coaxial cable will have a reduced bend radius before the coaxial cable is distorted and/or buckled by bending. In particular, structures may buckle and/or be displaced out of coaxial alignment by cable bending in excess of the allowed bend radius, resulting in cable collapse and/or degraded electrical performance. 
     A further cable consideration is supporting and securing the cable along its length, for example as the cable is routed and secured along a radio tower. Prior cables configured for hanging in the air, such as telephone and/or CATV cables between utility poles and a residence, have been configured with encapsulated messenger wires to increase the strength of the cable and/or provide a sturdy attachment point separate from the signal conductor portion of the cable. Thereby, the cable strength is improved and the cable may be secured with reduced risk of damage to the signal conductor portion of the cable. However, messenger wires may increase the materials cost and overall weight of the cable. 
     A stripline is a flat conductor sandwiched between parallel interconnected ground planes. Striplines have the advantage of being non-dispersive and may be utilized for transmitting high frequency RF signals. Striplines may be cost effectively generated using printed circuit board technology or the like. However, striplines may be expensive to manufacture in longer lengths/larger dimensions. Further, where a solid stacked printed circuit board type stripline structure is not utilized, the conductor sandwich is generally not self supporting and/or aligning, compared to a coaxial cable, and as such may require significant additional support/reinforcing structure. 
     Competition within the RF cable industry has focused attention upon reducing materials and manufacturing costs, electrical characteristic uniformity, defect reduction, installation simplification and overall improved manufacturing quality control. 
     Therefore, it is an object of the invention to provide a coaxial cable and method of manufacture that overcomes deficiencies in such prior art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention. Like reference numbers in the drawing figures refer to the same feature or element and may not be described in detail for every drawing figure in which they appear. 
         FIG. 1  is a schematic isometric view of an exemplary cable, with layers of the conductors, dielectric spacer and outer jacket stripped back. 
         FIG. 2  is a schematic end view of the cable of  FIG. 1 . 
         FIG. 3  is a schematic isometric view demonstrating a bend radius of the cable of  FIG. 1 . 
         FIG. 4  is a schematic isometric view of an alternative cable, with layers of the conductors, dielectric spacer and outer jacket stripped back. 
         FIG. 5  is a schematic end view of an alternative embodiment cable utilizing varied dielectric layer dielectric constant distribution. 
         FIG. 6  is a schematic end view of another alternative embodiment cable utilizing varied dielectric layer dielectric constant distribution. 
         FIG. 7  is a schematic end view of an alternative embodiment cable utilizing cavities for varied dielectric layer dielectric constant distribution. 
         FIG. 8  is a schematic end view of an alternative embodiment cable utilizing sequential vertical layers of varied dielectric constant in the dielectric layer. 
         FIG. 9  is a schematic end view of an alternative embodiment cable utilizing dielectric rods for varied dielectric layer dielectric constant distribution. 
         FIG. 10  is a schematic end view of an alternative embodiment cable utilizing dielectric rods for varied dielectric layer dielectric constant distribution. 
         FIG. 11  is a schematic end view of an alternative embodiment cable utilizing varied outer conductor spacing to modify operating current distribution within the cable. 
         FIG. 12  is a schematic end view of another alternative embodiment cable utilizing drain wires for varied outer conductor spacing to modify operating current distribution within the cable. 
         FIG. 13  is a schematic isometric view of an oval cross-section cable with an attachment feature provided as a rib extending from the jacket, parallel to the inner conductor. 
         FIG. 14  is a schematic isometric view of an oval cross-section cable with an attachment feature provided as a rib extending from the jacket, parallel to the inner conductor, including apertures. 
         FIG. 15  is a schematic end view of an oval cross-section cable with a fin extending from the jacket coplanar with a bottom section of the outer conductor. 
         FIG. 16  is a schematic end view of an hour glass-shaped cross-section cable with a fin extending from a bottom of the cable parallel with the inner conductor. 
         FIG. 17  is a schematic end view of an oval cross-section cable with a fin extending from the jacket at either side of the cable, coplanar with the inner conductor. 
         FIG. 18  is a schematic end view of an hour glass-shaped cross-section cable with a fin with a fin extending from the jacket at either side of the cable, coplanar with the inner conductor. 
         FIG. 19  is a schematic end view of an oval cross-section cable with a fin extending from the jacket, normal to the inner conductor. 
         FIG. 20  is a schematic end view of an hour glass-shaped cross-section cable with a fin extending from the jacket, normal to the inner conductor. 
         FIG. 21  is a schematic end view of an oval cross-section cable with a fin extending from the jacket, normal to the inner conductor. The fin provided with an additional layer. 
         FIG. 22  is a schematic end view of an hour glass-shaped cross-section cable with a fin extending from the jacket, normal to the inner conductor. The fin provided with an additional layer 
         FIG. 23  is a schematic end view of an oval cross-section cable with a fin extending from the jacket, normal to the inner conductor. The fin provided with an additional layer overlapping the fin. 
         FIG. 24  is a schematic end view of an hour glass-shaped cross-section cable with a fin extending from the jacket, normal to the inner conductor. The fin provided with an additional layer overlapping the fin. 
         FIG. 25  is a schematic end view of an oval cross-section cable with a fin extending from the jacket, normal to the inner conductor. The fin encapsulating an additional layer. 
         FIG. 26  is a schematic end view of an hour glass-shaped cross-section cable with a fin extending from the jacket, normal to the inner conductor. The fin encapsulating an additional layer. 
         FIG. 27  is a schematic isometric view of a cable with a fin extending from the jacket, normal to the inner conductor, with slots formed in the fin. 
         FIG. 28  is a schematic end view of an hour glass-shaped section cable with a fin loop extending from the jacket. 
         FIG. 29  is a schematic end view of an hourglass cross-section cable with a fin loop extending from the jacket. 
         FIG. 30  is a schematic end view of an oval cross-section cable with a fin loop extending from the jacket, an additional layer provided in the fin loop. 
         FIG. 31  is a schematic end view of an hour glass-shaped cross-section cable with a fin loop extending from the jacket, an additional layer provided in the fin loop. 
         FIG. 32  is a schematic view of  FIG. 30 , demonstrated with a fastener piercing the fin loop, a tear-out resistance of the fin loop improved by the presence of the additional layer. 
         FIG. 33  is a schematic end view of a pair of oval cross-section cables coupled to one another, top-to-bottom, by respective attachment features. 
         FIG. 34  is a schematic end view of a pair of hour glass-shaped cross-section cables coupled to one another, top-to-bottom, by respective attachment features. 
         FIG. 35  is a schematic end view of a pair of oval cross-section cables coupled to one another, side-to-side, by respective attachment features. 
         FIG. 36  is a schematic end view of a pair of oval cross-section cables coupled to one another, side-to-side, by respective attachment features. 
         FIG. 37  is a schematic isometric view of an exemplary jacket provided with side extending male and female attachment features according to the cables of  FIG. 35 . 
     
    
    
     DETAILED DESCRIPTION 
     The inventors have recognized that the prior accepted coaxial cable design paradigm of concentric circular cross-section design geometries results in unnecessarily large coaxial cables with reduced bend radius, excess metal material costs and/or significant additional manufacturing process requirements. 
     The inventors have further recognized that the application of a flat inner conductor, compared to a conventional circular inner conductor configuration, enables modification of the coaxial cable to improve a thermal dissipation characteristic of the cable with a reduced trade-off in electrical and/or mechanical performance. 
     An exemplary stripline RF transmission cable  1  is demonstrated in  FIGS. 1-3 . As best shown in  FIG. 1 , the inner conductor  5  of the cable  1 , extending between a pair of inner conductor edges  3 , is a flat metallic strip. A top section  10  and a bottom section  15  of the outer conductor  25  are aligned parallel to the inner conductor  5  with widths equal to the inner conductor width. The top and bottom sections  10 ,  15  transition at each side into convex edge sections  20 . Thus, the circumference of the inner conductor  5  is entirely sealed within an outer conductor  25  comprising the top section  10 , bottom section  15  and edge sections  20 . 
     The dimensions/curvature of the edge sections  20  may be selected, for example, for ease of manufacture. Preferably, the edge sections  20  and any transition thereto from the top and bottom sections  10 ,  15  is generally smooth, without sharp angles or edges. As best shown in  FIG. 2 , the edge sections  20  may be provided as circular arcs with an arc radius R, with respect to each side of the inner conductor  5 , equivalent to the spacing between each of the top and bottom sections  10 ,  15  and the inner conductor  5 , resulting in a generally equal spacing between any point on the circumference of the inner conductor  5  and the nearest point of the outer conductor  25 , minimizing outer conductor material requirements. 
     The desired spacing between the inner conductor  5  and the outer conductor  25  may be obtained with high levels of precision via application of a uniformly dimensioned spacer structure with dielectric properties, referred to as the dielectric layer  30 , and then surrounding the dielectric layer  30  with the outer conductor  25 . Thereby, the cable  1  may be provided in essentially unlimited continuous lengths with a uniform cross-section at any point along the cable  1 . 
     The inner conductor  5  metallic strip may be formed as solid rolled metal material such as copper, aluminum, steel or the like. For additional strength and/or cost efficiency, the inner conductor  5  may be provided as copper-coated aluminum or copper-coated steel. 
     Alternatively, the inner conductor  5  may be provided as a substrate  40  such as a polymer and/or fiber strip that is metal coated or metalized, for example as shown in  FIG. 4 . One skilled in the art will appreciate that such alternative inner conductor configurations may enable further metal material reductions and/or an enhanced strength characteristic enabling a corresponding reduction of the outer conductor strength characteristics. 
     The dielectric layer  30  may be applied as a continuous wall of plastic dielectric material around the outer surface of the inner conductor  5 . The dielectric layer  30  may be a low loss dielectric material comprising a suitable plastic such as polyethylene, polypropylene, and/or polystyrene. The dielectric material may be of an expanded cellular foam composition, and in particular, a closed cell foam composition for resistance to moisture transmission. Any cells of the cellular foam composition may be uniform in size. One suitable foam dielectric material is an expanded high density polyethylene polymer as disclosed in commonly owned U.S. Pat. No. 4,104,481, titled “Coaxial Cable with Improved Properties and Process of Making Same” by Wilkenloh et al, issued Aug. 1, 1978, hereby incorporated by reference in the entirety. Additionally, expanded blends of high and low density polyethylene may be applied as the foam dielectric. 
     Although the dielectric layer  30  generally consists of a uniform layer of foam material, as described in greater detail herein below, the dielectric layer  30  can have a gradient or graduated density varied across the dielectric layer cross-section such that the density of the dielectric increases and/or decreases radially from the inner conductor  5  to the outer diameter of the dielectric layer  30 , either in a continuous or a step-wise fashion. Alternatively, the dielectric layer  30  may be applied in a sandwich configuration as two or more separate layers together forming the entirety of the dielectric layer  30  surrounding the inner conductor  5 . 
     The dielectric layer  30  may be bonded to the inner conductor  5  by a thin layer of adhesive. Additionally, a thin solid polymer layer and another thin adhesive layer may be present, protecting the outer surface of the inner conductor  5  (for example, as it is collected on reels during cable manufacture processing). 
     The outer conductor  25  is electrically continuous, entirely surrounding the circumference of the dielectric layer  30  to eliminate radiation and/or entry of interfering electrical signals. The outer conductor  25  may be a solid material such as aluminum or copper material sealed around the dielectric layer as a contiguous portion by seam welding or the like. Alternatively, helically wrapped and/or overlapping folded configurations utilizing, for example, metal foil and/or braided type outer conductor  25  may also be utilized. 
     If desired, a protective jacket  35  of polymer materials such as polyethylene, polyvinyl chloride, polyurethane and/or rubbers may be applied to the outer diameter of the outer conductor. The jacket  35  may comprise laminated multiple jacket layers to improve toughness, strippability, burn resistance, the reduction of smoke generation, ultraviolet and weatherability resistance, protection against rodent gnaw-through, strength resistance, chemical resistance and/or cut-through resistance. For ease of installation, an attachment feature  75  may be provided integrated with the jacket  35 . 
     The flattened characteristic of the cable  1  has inherent bend radius advantages. As best shown in  FIG. 3 , the bend radius of the cable perpendicular to the horizontal plane of the inner conductor  5  is reduced compared to a conventional coaxial cable of equivalent materials dimensioned for the same characteristic impedance. Since the cable thickness between the top section  10  and the bottom section  15  is thinner than the diameter of a comparable coaxial cable, distortion or buckling of the outer conductor  25  is less likely at a given bend radius. A tighter bend radius also improves warehousing and transport aspects of the cable  1 , as the cable  1  may be packaged more efficiently, for example provided coiled upon smaller diameter spool cores which require less overall space. 
     Electrical modeling of stripline-type RF cable structures with top and bottom sections with a width similar to that of the inner conductor (as shown in  FIGS. 1-4 ) demonstrates that the electric field generated by transmission of an RF signal along the cable  1  and the corresponding current density with respect to a cross-section of the cable  1  is greater along the inner conductor edges  3  at either side of the inner conductor  5  than at a mid-section  7  of the inner conductor. Uneven current density generates higher resistivity and increased signal loss. Therefore, the cable configuration may have an increased attenuation characteristic, compared to conventional circular/coaxial type RF cable structures where the inner conductor circumferences are equal. 
     To obtain the materials and structural benefits of the stripline RF transmission cable  1  as described herein, the electric field strength and corresponding current density may be balanced by increasing the current density proximate the mid-section  7  of the inner conductor  5 . The current density may be balanced, for example, by modifying the dielectric constant of the dielectric layer  30  to provide an average dielectric constant that is lower between the inner conductor edges  3  and the respective adjacent edge sections  20  than between a mid-section  7  of the inner conductor  5  and the top and the bottom sections  10 , 15 . Thereby, the resulting current density may be adjusted to be more evenly distributed across the cable cross-section to reduce attenuation. 
     The dielectric layer  30  may be formed with layers of, for example, expanded open and/or closed-cell foam dielectric material, where the different layers of the dielectric material have a varied dielectric constant. The differential between dielectric constants and the amount of space within the dielectric layer  30  allocated to each type of material may be utilized to obtain the desired average dielectric constant of the dielectric layer  30  in each region of the cross-section of the cable  1 . 
     As shown for example in  FIG. 5 , a dome-shaped increased dielectric constant portion  45  of the dielectric layer  30  may be applied proximate the top section  10  and the bottom section  15  extending inward toward the mid-section  7  of the inner conductor  5 . Alternatively, the dome-shaped increased dielectric constant portion  45  of the dielectric layer  30  proximate the inner conductor  5  may be positioned extending outward from the mid-section  7  of the inner conductor  5  towards the top and bottom sections  10 , 15 , as shown for example in  FIG. 6 . 
     Air may be utilized as a low cost dielectric material. As shown for example in  FIG. 7 , one or more areas of the dielectric layer  30  proximate the edge sections  20  may be applied as a cavity  50  extending along a longitudinal axis of the cable  1 . Such cavities  50  may be modeled as air (pressurized or unpressurized) with a dielectric constant of approximately 1 and the remainder of the adjacent dielectric material of the dielectric layer  30  again selected and spaced accordingly to provide the desired dielectric constant distribution across the cross-section of the dielectric layer  30  when averaged with the cavity portions allocated to air dielectric. 
     As shown for example in  FIG. 8 , multiple layers of dielectric material may be applied, for example, as a plurality of vertical layers aligned normal to the horizontal plane of the inner conductor  5 , a dielectric constant of each of the vertical layers provided so that the resulting overall dielectric layer dielectric constant increases towards the mid-section  7  of the inner conductor  5  to provide the desired aggregate dielectric constant distribution across the cross-section of the dielectric layer  30 . Alternatively, for example as shown in  FIG. 9 , the dielectric material may be applied as simultaneous high and low (relative to one another) dielectric constant dielectric material streams through multiple nozzles with the proportions controlled with respect to cross-section position by the nozzle distribution or the like so that a position varied mixed stream of dielectric material is applied to obtain a desired (e.g., generally smooth) gradient of the dielectric constant across the cable cross-section, so that the resulting overall dielectric constant of the dielectric layer  30  increases in a generally smooth gradient from the edge sections  20  towards the mid-section  7  of the inner conductor  5 . 
     The materials selected for the dielectric layer  30 , in addition to providing varying dielectric constants for tuning the dielectric layer cross-section dielectric profile for attenuation reduction, may also be selected to enhance structural characteristics of the resulting cable  1 . For example, as shown in  FIG. 10 , the dielectric layer  30  may be provided with first and second dielectric rods  55  located proximate a top side  60  and a bottom side  65  of the mid-section  7  of the inner conductor  5 . The dielectric rods  55 , in addition to having a dielectric constant greater than the surrounding dielectric material, may be for example fiberglass or other high strength dielectric materials that improve the strength characteristics of the resulting cable  1 . Thereby, the thickness of the inner conductor  5  and/or outer conductor  25  may be reduced to obtain overall materials cost reductions without compromising strength characteristics of the resulting cable  1 . 
     Alternatively and/or additionally, the electric field strength and corresponding current density may also be balanced by adjusting the distance between the outer conductor  25  and the mid-section  7  of the inner conductor  5 . For example, as shown in  FIG. 11 , the outer conductor  25  may be provided spaced farther away from each inner conductor edge  3  than from the mid-section  7  of the inner conductor  5 , creating a generally hour glass-shaped cross-section. The distance between the outer conductor  25  and the mid-section  7  of the inner conductor  5  may be less than, for example, 0.7 of a distance between the inner conductor edges  3  and the outer conductor  25  (at the edge sections  20 ). 
     The dimensions may also be modified, for example as shown in  FIG. 12 , by applying a drainwire  70  coupled to the inner diameter of the outer conductor  25 , one proximate either side of the mid-section  7  of the inner conductor  5 . Because each of the drain wires  70  is electrically coupled to the adjacent inner diameter of the outer conductor  25 , each drain wire  70  becomes an inwardly projecting extension of the inner diameter of the outer conductor  25 , again forming the generally hour glass cross-section to average the resulting current density for attenuation reduction. As described with respect to the dielectric rods  55  of  FIG. 10 , the drain wires  70  may similarly increase structural characteristics of the resulting cable, enabling cost saving reduction of the metal thicknesses applied to the inner conductor  5  and/or outer conductor  25 . 
     The attachment feature  75  may be formed as an extension of the jacket  35 , for example as shown in  FIGS. 13-18 , as a longitudinal fin  80  aligned parallel with a horizontal plane of the inner conductor  5 . As shown in  FIG. 13 , the fin  80  may be provided ready for perforation by a fastener anywhere along the longitudinal extent, for example as required by the position of support structure relative to the cable in a specific installation, or configured with a plurality of pre-applied apertures  85  spaced periodically along the fin, for example as shown in  FIG. 14 . 
     The fin  80  may be provided extending from the cable  1  coplanar with the top or bottom sections  10 ,  15 , as shown for example in  FIGS. 13-16 , for flush mounting of the cable  1  to a desired support structure. The fin  80  may also be positioned coplanar with the inner conductor  5  with a fin  80  extending from one or both sides of the cable  1 , for example as shown in  FIGS. 17 and 18 , for ease of mounting to a range of varied surfaces. 
     Alternatively, the fin  80  may be arranged, for example as shown in  FIGS. 19-27 , normal to the horizontal plane of the inner conductor  5 . To reduce the impact of the fin  80  on the bending characteristic of the cable  1 , the fin  80  may be provided with a plurality of longitudinally spaced slots  81 , as shown for example in  FIG. 27 . 
     The strength characteristics of the fin  80  may be configured, for example, by selecting the jacket  35  material and/or the dimensions of the fin  80 , including a thickness of the fin  80 . Further, the fin  80  may be reinforced by application of a reinforcing layer  90  to the fin  80  as a single layer ( FIGS. 21-22 ) or an overlapping layer ( FIG. 23-24 ). The reinforcing layer  90  may be a further portion of the jacket  35  material or a higher strength material selected for longitudinal and/or tear strength characteristics. The reinforcing layer  90  may be applied, for example, as filaments and/or woven meshes of metal, glass reinforced plastic, fiberglass, aramid or the like. The reinforcing layer  90  may be entirely enclosed within the fin  80 , for example as shown in  FIGS. 25-26 . Alternatively, for example as shown in  FIGS. 28-32 , the attachment feature  75  may be provided in a double wall configuration as a fin loop  82  extending from both the top and bottom sections  10 ,  15  of the cable  1  to distribute the attachment feature  75  connection to more than a single point along the circumference of the jacket  35 . The loop of the attachment feature  75  formed between the top and bottom sections  10 ,  15  may include a reinforcing layer  90  disposed in the fin loop  82 , for example, positioned equidistant from the cable  1 . Thereby, a fastener  83  may be inserted through each of the double walls and tear out inhibited by the reinforcing layer  90 , as demonstrated in  FIG. 32 . 
     The attachment feature  75  may be provided, for example as shown in  FIGS. 33-36 , as complementary male portions  92  and female portions  94  at opposite sides of the cable  1 , for example the top and bottom or left and right sides with respect to a horizontal plane of the inner conductor  5 , configured to mate with corresponding features of adjacent cables  1  and/or mounting points. Thereby, the several cables  1  may be easily aligned supporting one another in compact space saving parallel runs. For example as shown in  FIGS. 33 and 34 , the male portion  92  may be provided as a projection rib  96  that seats within a female portion  94  provided as a groove  98 . Where the male and female portions  92 ,  94  are continuous along the longitudinal extent, manufacture via extrusion and or cutting elements in the process line is simplified and the interconnection therebetween may be made without requiring longitudinal alignment between the male and female portions  92 ,  94 . 
     Alternatively, the male and female portions  92 ,  94  may be provided periodically along the longitudinal extent, for example as shown in  FIGS. 35-37 , as male protrusions  100  that snap-fit into female seats  102 , to provide a longitudinal interlock characteristic to the attachment feature  75 . 
     In further embodiments, the attachment feature  75  may be provided as a longitudinally periodic attachment to the cable  1  that is then encapsulated by the application of the jacket  35  around both the outer conductor and at least a base portion of the attachment feature  75 . For example, the attachment feature  75  may be provided as a clip with a male protrusion configured for direct mating with a standard attachment point, such as a three quarter inch hole often provided on tower structures for “snap-in” type cable hangers. Because of the non-circular cross-section of the cable  1 , the clip portion of the attachment feature may anchor upon the cable without requiring additional anti-rotation structure or reinforcement. 
     One skilled in the art will appreciate that the cable  1  has numerous advantages over a conventional circular cross-section coaxial cable. Because the desired inner conductor surface area is obtained without applying a solid or hollow tubular inner conductor, a metal material reduction of one half or more may be obtained. Alternatively, because complex inner conductor structures which attempt to substitute the solid cylindrical inner conductor with a metal coated inner conductor structure are eliminated, required manufacturing process steps may be reduced. The attachment features  75  provided integral with the jacket  35  may simplify installation of the cables  1  and/or enable easy alignment of multiple adjacent cables  1  in close quarters to conserve space. Because the attachment features  75  are integrated with the jacket  35 , separate attachment hardware requirements, such as cable hangers, and their respective installation steps, may be eliminated. 
     
       
         
           
               
             
               
                   
               
               
                 Table of Parts 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 1 
                 cable 
               
               
                 3 
                 inner conductor edge 
               
               
                 5 
                 inner conductor 
               
               
                 7 
                 mid-section 
               
               
                 10 
                 top section 
               
               
                 15 
                 bottom section 
               
               
                 20 
                 edge section 
               
               
                 25 
                 outer conductor 
               
               
                 30 
                 dielectric layer 
               
               
                 32 
                 thermally conductive material 
               
               
                 35 
                 jacket 
               
               
                 40 
                 substrate 
               
               
                 45 
                 increased dielectric constant portion 
               
               
                 50 
                 cavity 
               
               
                 55 
                 dielectric rod 
               
               
                 60 
                 top side 
               
               
                 65 
                 bottom side 
               
               
                 70 
                 drain wire 
               
               
                 75 
                 attachment feature 
               
               
                 80 
                 fin 
               
               
                 81 
                 slot 
               
               
                 82 
                 fin loop 
               
               
                 83 
                 fastener 
               
               
                 85 
                 aperture 
               
               
                 90 
                 additional layer 
               
               
                 92 
                 male portion 
               
               
                 94 
                 female portion 
               
               
                 96 
                 projection rib 
               
               
                 98 
                 groove 
               
               
                 100 
                 male protrusion 
               
               
                 102 
                 female seat 
               
               
                   
               
            
           
         
       
     
     Where in the foregoing description reference has been made to ratios, integers or components having known equivalents then such equivalents are herein incorporated as if individually set forth. 
     While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus, methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of applicant&#39;s general inventive concept. Further, it is to be appreciated that improvements and/or modifications may be made thereto without departing from the scope or spirit of the present invention as defined by the following claims.