Abstract:
An support for coaxial transmission lines is described, having a reduced mass and being configured to reduce bending stresses when subject to insertion or axial load effects.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to transmission line inner conductor support. More particularly, the present invention relates to light weight inner conductor support systems and methods for rigid coaxial transmission lines. 
   BACKGROUND OF THE INVENTION 
   With the advent of digital television, it has become increasingly important that transmission lines carrying broadcast signals to broadcast antennas convey the signals with minimal attenuation and signal distortion. Conventional transmission lines of the broadcast caliber are usually coaxial in nature and very long, being fabricated from joining several smaller coaxial transmission lines together. To maintain the necessary separation between the inner conductor and outer conductor of the coaxial transmission line, series of insulating supports are interspersed within the line at specified locations. The insulating support structures in the coaxial transmission line are subject to several significant loads over their life cycle. 
   Lines mounted horizontally subject all the supports to a nominal radial load that is proportional to the weight of the inner conductor divided by the number of supporting insulating supports. Lines mounted vertically subject the first support in each section to an axial load at least equal to the weight of the inner conductor plus the forces encountered during the normal differential expansion which occurs between the inner conductor and the outer conductor during power up or power down. Accordingly, for transmission lines that are vertically mounted, the first insulating support or anchor support is subject to a higher load due to axial forces in the transmission line than the load due to radial forces on the individual supports. 
   Other forms of loads may affect the transmission line such as those associated with the transportation and the installation of the line. For example, it should be understood that radial loads on the individual insulating supports are typically a fraction of the shock load (due to the inertia of the inner conductor) while the axial load on the anchor or end insulator support will equal the entire shock load due to the mast of the inner conductor. Also, there is an axial force called the insertion force associated with the process of forming the connection between successive sections of lines. Again, the axial forces on the anchor or end insulator support is understood to be greatly in excess of the radial loads anticipated on the individual supports. 
   Also, during the fabrication process, the inner conductor with all its internal support structures must be inserted into the outer conductor and pushed through the entire length of the transmission line section to arrive at its final position. Due to variations or irregularities in the outer conductor diameter or interior finish, for example, the insulating supports are subject to axial forces up to a maximum of the total insertion force (in the case where a single insulating support is the cause of the resistance). These loads are different from the radial loads typically encountered by the inner supports when under normal operating conditions. Therefore, these fabrication loads can be very large and primarily axially directed rather than radially (though there may be an occasional significant radial component). 
   It should be apparent from the above that the insulating supports&#39; greatest force loading will be due to axial forces rather than conventionally imagined radial forces. In this regard, conventional state-of-the art practices for supporting the inner conductor of rigid coaxial transmission lines have generally been of two types: dielectric pins oriented radially outward from the inner conductor or a disc of dielectric material or puck modified to have mass removed from the interior while retaining sufficient strength to perform the supporting function. These objects are manufactured from an electrically insulating material, generally either of ceramic or plastic composition. The radial forces are carried as compressive loads while axial loads are carried as bending loads, like a beam. 
   Conventional approaches to addressing the radial and axial loads rising from fabrication and supporting the transmission line have been directed to simply adding to the axial thickness or more material to the supports to accommodate the additional stresses. While the added mass may be effectively compensated for, on the average, by reducing the diameter of the inner section, manufacturing variations become proportionally greater increasing the perturbations of signals in the transmission line. 
   Therefore, there has been a long standing need in the transmission line community for providing systems and methods for a center conductor support implementation that reduces support mass while providing transmission line integrity. 
   SUMMARY OF THE INVENTION 
   The foregoing needs are met, to a great extent, by the present invention, wherein difficulties in the prior art are mitigated by using specially configured members to form insulating supports subject to reduced bending and frictional forces. These and other advantages of the invention are discussed in greater detail below. 
   In accordance with one embodiment of the present invention, systems and methods for an improved coaxial transmission line anchor insulating support are provided by an inner conductor insulating support, comprising an insulating perimeter ring, an outer portion of which is substantially conformal to the outer conductor, an inner portion of which is substantially displaced from the inner conductor, and a plurality of insulating center conductor facing prongs, which are disposed at symmetric angles about the perimeter ring, and extend from the perimeter ring in alternating off-radial angles, the prongs being sufficiently long so as to contact the inner conductor. 
   In accordance with another embodiment of the present invention, an inner conductor to outer conductor coaxial transmission line insulating support is provided, comprising an insulating perimeter ring, an outer portion of which is substantially conformal to the outer conductor, an inner portion of which is substantially displaced from the inner conductor; and a plurality of insulating center conductor facing prongs, which are disposed at symmetric angles about the perimeter ring and all extend from the perimeter ring at an angle that intersects a common point, the prongs being sufficiently long so as to contact the inner conductor. 
   In accordance with yet another embodiment of the present invention, a non-anchor inner conductor to outer conductor coaxial transmission line insulating support is provided, comprising a first support member extending from a first member hole in the inner conductor, and a second support member extending from a second member hole in the inner conductor, an outer portion of the second member being joined to the first member at an outer portion of the second member being joined to the first member at an outer portion of the second member to form an angled support, wherein an outer periphery of the joined portion abuts the outer conductor. 
   In accordance with yet another embodiment of the present invention, an inner conductor to outer conductor coaxial transmission line insulating support is provided, comprising a conically shaped insulating support of sufficient length to abut the outer conductor at the tip of the support, and having base portion conforming to the contour of the inner conductor, and a plurality of prongs disposed about a base of the support, wherein the prongs are matched to holes in the inner conductor. 
   In accordance with yet another embodiment of the present invention, an inner conductor to outer conductor coaxial transmission line insulating support is provided, comprising a hollow insulating support in the shape of a quadro-pod, wherein edges of the support are substantially thick to form reinforcing ribs, wherein the base of the support is conformed to a contour of the inner conductor and the support having a sufficient height to abut the outer conductor at the top of the support, and a plurality prongs disposed about corners of the base of the support that are co-located with holes in the inner conductor. 
   In accordance with yet another embodiment of the present invention, an inner conductor to outer conductor coaxial transmission line insulating support is provided, comprising an insulating support having trusses of insulating material to form a truss-like tetrahedral support structure, wherein the base of the support is conformal to a contour of the inner conductor, and the support having a sufficient height to abut the outer conductor at the top of the support, and a plurality of prongs disposed about corners of the base of the support that are co-located with holes in the inner conductor. 
   In accordance with yet another embodiment of the present invention, a method for supporting an inner conductor within an outer conductor of a coaxial transmission line is provided, comprising the step of inserting an inner conductor support onto an inner conductor, the support having an insulating perimeter ring, an outer portion of which is substantially conformal to the outer conductor, an inner portion of which is substantially displaced from the inner conductor, wherein the insulating support has a plurality of insulating center conductor facing prongs, which are disposed about the perimeter ring, and extend from the perimeter ring in alternating off-radial angles, the prongs being sufficiently long so as to contact the inner conductor. 
   In accordance with yet another embodiment of the present invention, a method for supporting an inner conductor within an outer conductor of a coaxial transmission line is provided, comprising the step of inserting an inner conductor support over an inner conductor, the support having an insulating perimeter ring, an outer portion of which is substantially conformal to the outer conductor, an inner portion of which is substantially displaced from the inner conductor, wherein the support has a plurality of insulating center conductor facing prongs, which are disposed about the perimeter ring, and extend from the perimeter ring in alternating off-radial angles, the prongs being sufficiently long so as to contact the inner conductor. 
   In accordance with yet another embodiment of the present invention, a method for supporting an inner conductor within an outer conductor of a coaxial transmission line is provided, comprising the step of inserting an inner conductor support over an inner conductor, the support having an insulating perimeter ring, an outer portion of which is substantially conformal to the outer conductor, an inner portion of which is substantially displaced from the inner conductor, wherein the support has a plurality of insulating center conductor facing prongs, which are disposed about the perimeter ring and all extend from the perimeter ring at an angle that intersects a common point, the prongs being sufficiently long so as to contact the inner conductor. 
   In accordance with yet another embodiment of the present invention, a method for supporting an inner conductor within an outer conductor of a coaxial transmission line is provided, comprising the step of inserting an inner conductor support over an inner conductor, the support having a first support member extending from a first member hole in the inner conductor and a second support member extending from a second member hole in the inner conductor, an outer portion of the second member being joined to the first member at an outer portion of the second member to form an angled support, wherein an outer periphery of the joined portion abuts the outer conductor. 
   In accordance with yet another embodiment of the present invention, a method for supporting an inner conductor within an outer conductor of a coaxial transmission line is provided, comprising the step of inserting an inner conductor support over an inner conductor, the support having a conically shaped insulating support of sufficient length to abut the outer conductor at the tip of the support and having base portion conforming to the contour of the inner conductor and a plurality of prongs disposed about a base of the support, wherein the prongs are matched to holes in the inner conductor. 
   In accordance with yet another embodiment of the present invention, a method for supporting an inner conductor within an outer conductor of a coaxial transmission line is provided, comprising the step of inserting an inner conductor support over an inner conductor, the support having a hollow insulating support in the shape of a quadro-pod, wherein edges of the support are substantially thick to form reinforcing ribs, wherein the base of the support is conformed to a contour of the inner conductor, the support having a sufficient height to abut the outer conductor at the top of the support and a plurality prongs disposed about corners of the base of the support that are co-located with holes in the inner conductor. 
   In accordance with yet another embodiment of the present invention, a method for supporting an inner conductor within an outer conductor of a coaxial transmission line is provided, comprising the step of inserting an inner conductor support over an inner conductor, the support having an insulating support having trusses of insulating material to form a truss-like tetrahedral support structure, wherein the base of the support is conformal to a contour of the inner conductor, the support having a sufficient height to abut the outer conductor at the top of the support and having a plurality of prongs disposed about corners of the base of the support that are co-located with holes in the inner conductor. 
   In accordance with yet another embodiment of the present invention, an inner conductor to outer conductor coaxial transmission line insulating support is provided, comprising a first supporting means for securing the inner conductor within the outer conductor, wherein the supporting means is formed of an electrically insulating material and is asymmetrically shaped about the inner conductor, wherein the securing means is affixed via inner conductor-side prongs to a radial sector of the inner conductor via holes in the inner conductor; and a second supporting means for securing the inner conductor within the outer conductor, wherein the supporting means is formed of an electrically insulating material and is asymmetrically shaped about the inner conductor, wherein the securing means is affixed via inner conductor-side prongs to another radial sector of the inner conductor via holes in the inner conductor 
   In accordance with yet another embodiment of the present invention, a coaxial transmission line is provided, comprising an inner electrical energy conducting means, an outer electrical energy conducting means, and an axial securing means for securing the outer conductor with respect the inner conductor, wherein the outer securing means is formed of an electrically insulating material and is circular about its outer periphery with inner conductor facing opposing prongs about its inner periphery. 
   In accordance with yet another embodiment of the present invention, a coaxial transmission line is provided, comprising an inner electrical energy conducting means, an outer electrical energy conducting means, and a first a plurality of securing means for securing the inner conductor within the outer conductor, the plurality of securing means being arranged radially along the inner conductor, wherein the securing means is formed of an electrically insulating material and is asymmetrically shaped about the inner conductor, wherein the securing means is affixed via inner conductor-side prongs to the inner conductor via holes in the inner conductor. 
   There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto. 
   In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. 
   As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a prospective view of an exemplary support according to this invention. 
       FIG. 2  is a front view of a pair of alternative exemplary supports. 
       FIG. 3  is a side view of a pair of the exemplary supports of  FIG. 2 . 
       FIG. 4  is a side view of an another alternative exemplary support. 
       FIG. 5  is a side view of another alternative exemplary support. 
       FIG. 6  is a side view of another alternative exemplary support. 
       FIG. 7  is a side view of another alternative exemplary support. 
   

   DETAILED DESCRIPTION 
   The invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. 
     FIG. 1  illustrates an exemplary support structure  10  according to a preferred embodiment of this invention. The structure  10  contains an outer support ring  12  with a plurality of “inward” facing prongs  14  radially orientated and offset from each other at the center conductor junction point. The prongs  14  are supported at the outer periphery by the support ring  12  at intervals that are at approximately 90°. Through the prongs  14  are shown as being substantially straight members with a beveled edge  16 , it should be appreciated, however, that the prongs may be curved to afford the same effect. The prongs  14  are also illustrated as having offset symmetric angles with each other from the plane of the structure  10 . By having offset symmetric angles, the prongs  14  provide support at both sides of the support  10  and helps maintain upright stability. 
   The exemplary structure  10  has the advantages of being a support structure capable of withstanding the anticipated loads associated with the anchor support. The configuration of the exemplary support structure  10  of  FIG. 1  reduces or eliminates bending loads on the support and replaces them with axial compression or tensile loads on the prongs  14 , much like the spokes of a bicycle wheel. 
     FIG. 2  is a front view of a pair of modified exemplary anchor supports  20  positioned over an anchor connector assembly  22 . The exemplary support(s)  20  has prongs  24  similar in design to the prongs  14  of  FIG. 1 . However, the inner ends of the prongs  24  are shown as being constrained by a inner prong support  26 , having a contour that matches the inner conductor. The outer portion of the prongs is also supported at the outer periphery by a stepped support ring  25 . 
     FIG. 3  is a side view of a pair of the exemplary anchor supports  20  of  FIG. 2  positioned over the anchor connector assembly  22 . The anchor connector assembly  22  is formed by the junction of two pieces of the inner connector of a transmission line having a male end  34  and a female end  36 . Each support  20  is configured so that the faces  38  mate with each other when the supports  20  are properly positioned at the male end  34  and female  36  of the inner conductor when the connector is joined together. 
   The exemplary anchor support  20  can be considered as a “half image” variant of the support of  FIG. 1 . That is, the support  20  can be arrived at by generally taking, in essence, the support of  FIG. 1  and splitting it along the center of the support ring  12 . It should be noted, that the prongs of the exemplary embodiments of  FIGS. 2 and 3  are illustrated as being spaced 120° from each, while the prongs of the exemplary embodiment of  FIG. 1  illustrated as being separated by 90°. Of course, it is understood that the separation angle is a design preference, and may be varied without departing from the spirit and scope of this invention. Additionally, as one of many alternatives, the tips of the prongs  24  may be configured without the inner prong support  26  and inserted into holes  35  of the inner conductor to secure the support  20 , as desired. Further, while  FIGS. 2–3  show the outer support ring  25  as being stepped, non-stepped, or otherwise alternate contours may be used as desired. 
   Due to the angles employed for the prongs, the beam type loading of the prior art is converted to compression and tensile loads which may be borne by members having significantly reduced cross section and associated mass. Additionally, as stated above, with the decrease in the mass of the insulator support  20 , significant reduction of costs and decreases in signal perturbation can be achieved. 
     FIG. 4  illustrates another exemplary embodiment of an intermediate (or non-anchor) support structure. An angle support arm  40  is shown protruding from an inner conductor  42  via holes  44  in the inner conductor  42 . The support  40  may be formed by “bending” a rod of insulating material, for example. Alternatively, it may be formed by stamping, milling, casting, etc., or by any now or future known method for conforming suitable material to the shape shown in  FIG. 4 . The general support  40  can be retained within the inner conductor  42  by any one or more of commonly or future arrived methods for securing the support arm  40 . For example, the surface of the insulator support  40  may be milled in a manner to form an indent or fitting ring for the holes  44  thereby enabling the support  40  to “snap” into place. Additionally, the support  40  may traverse the entire diameter of the hollow inner conductor  42  and thus be fixed within the inner conductor  42 . 
   Though  FIG. 4  illustrates the insulating support  40  as having one member being longer than the other member, it should be appreciated that other shapes or forms may be configured as desired. For example, both sides of the insulating support may be of equal length. Furthermore, the insulating support  40  may be formed to have a “U-shaped” appearance, for example. 
   Additionally, it should be apparent that in order for the exemplary support  40  to afford complete support between the inner conductor and the outer conductor, a plurality of supports  40  should be placed at various axial locations along the inner and at various radial locations around the inner conductor, possibly at the same location as other supports. 
     FIG. 5  illustrates another exemplary support embodiment  50  having a hollow cone-like structure. The inner conductor side of the support  50  is terminated with insertion prongs  52  at the “corners” of the support  50 . The prongs  52  provide the support  50  the ability to be fixed to the inner conductor  54  via the insertion holes  56  (obstructed from view). The support  50  is illustrated as being generally in the shape of a cone, with the base portion of the cone conformed to the contour of the surface of the inner conductor  54 . The support  50  is illustrated as being hollow throughout its entirety, however, various sections of it may be solid, for added reinforcement, as desired. Also, the base of the support  50  may be shaped to allow a greater or lesser plurality of prongs  52  to be formed, than the four (one obstructed from view) shown. 
     FIG. 6  illustrates another exemplary support embodiment  60  having a quadro-pod like structure. The support  60  is configured to be similar in many respects to the embodiment of  FIG. 5 . However, rather than having a conical shape, the exemplary embodiment of  FIG. 6  has a semi-tetrahedral or quadro-pod shape. Further, ribs  62  are formed at the “corners” of the support  60  and at the base edge  64 . Webbed surface  68  spans the ribs to add additional support. Prongs  66  affix the support  60  to holes in the inner conductor  69 . 
     FIG. 7  illustrates another embodiment of an exemplary support  70  having a truss-like structure. The base of the base of the support  70  is configured to conform to the surface of the inner conductor  72  and is attached to the inner conductor  72  via prongs  74  and holes (obstructed from view) in the inner conductor  72 . Trusses and their various shapes are well known in the art and therefore the available different variations of designs and shapes are not further discussed. 
   It should be apparent that the above exemplary embodiments provide systems and methods for at least reducing axial stresses on the supports. Accordingly, various types of light weight structures, shapes, configurations exploiting the various support shapes shown above may be implemented according to the knowledge of one of ordinary skill in the art without departing from the spirit and scope of this invention. It should be appreciated that due to the reduced mass of the exemplary supports described herein, significant reduction in cost of dielectric material such as TFE (Teflon) and PFA (Teflon based polymer) which are commonly used in these applications, can be achieved. Other costs and performance related benefits can be achieved depending on the particular choice of materials used. 
   The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.