Abstract:
A pre-engineered, packaged RF transparent barrier for non-penetrating installation on a roof, ground, or other surface can be pre-fabricated in different heights and or widths such that customizable barriers can be implemented without manufacturing costs typical of designing custom antenna gate structures. RF transparent materials reduce potential barrier-caused problems such as interference or reflection of RF signals. The barrier balances RF degradation potential, structural integrity, and cost considerations in its design, fabrication, and installation. A method of fulfilling the requirements for an antenna barrier installation is described.

Description:
This application claims the priority benefit of U.S. Provisional Application Ser. No. 60/793,906; filed Apr. 21, 2006. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to gates for radio frequency (RF) antenna systems. More specifically, the present invention relates to structures and methods for pre-engineered RF-permeable barriers for guarding or gating RF antenna systems. 
     BACKGROUND OF THE INVENTION 
     Cellular communications networks utilize radio frequency (RF) antenna systems at “cell sites” to transmit and receive RF signals. Cell sites are typically spaced from three to eight miles apart to achieve acceptable results. Consequently, a large metropolitan area can include hundreds of individual cell sites to insure thorough coverage. RF antenna systems are typically strategically placed atop the most prominent, visible locations within the surrounding landscape, attached to the sides or rooftops of buildings, or are mounted on new or existing tower structures. Furthermore, many such antenna systems are installed at locations which are accessible to maintenance personnel or the general public. 
     To distract would-be vandals, reduce access to areas of potentially high RF emissions, and reduce tampering of RF antenna systems, barriers are typically constructed to surround an antenna preventing access to the antenna and surrounding area. Also, concealment strategies have been attempted to make antennas blend within the existing architecture of a building or a location. 
     Successfully gating existing RF antenna systems requires a number of constraints to be considered including the design, fabrication and mounting of the antenna gate structure. These constraints include, for example, the structural integrity of the gate within any requirements of the local and/or regional building codes, the avoidance of RF signed degradation, the ability to resist degradation from environmental effects, and the capability for relatively quick installation with minimal damage to the surrounding environment, e.g., land or rooftop. Ideally, all of these constraints should be satisfied, or balanced, while maintaining economic viability. 
     Many communities, including most major cities, either already have, or will have, codes that demand concealment and/or securement of a cell site. Since each potential cell site is unique, no single antenna barrier structure or design will suffice. There is a need for an alternative to having a custom engineered barrier assembly for each site. Specifically, there is a need for an RF antenna barrier kit which can be efficiently assembled by the end user and which includes all materials required for assembly. What is further needed is such a kit that does not require design engineers and architects to custom build the gate structure as a function of the size and location of any given installation. The present invention addresses these and other needs. 
     SUMMARY OF THE INVENTION 
     The present invention provides a structure for pre-engineered RF permeable barriers for surrounding, guarding or gating RF antenna systems. 
     The present invention provides a pre-engineered, pre packaged RF transparent barrier. The barrier is non-penetrating in its installation (i.e. no roof, ground, or surface penetrations are required in its installation or assembly), pre-fabricated in different heights, widths, or both, such that customizable barriers can be implemented without the manufacturing costs attendant with designing custom antenna gate structures. By replacing the need for custom parts and installation with prefabricated structures, the overall cost of the barrier is reduced. The use of RF transparent materials in part, or all, of the barrier reduces potential barrier-caused problems such as interference or reflection of RF signals. 
     A barrier in accordance with the invention balances RF degradation potential, structural integrity, and cost considerations in its design, fabrication, and installation. 
     In one aspect, a barrier for surrounding an RF antenna and for placement on a surface at the cell cite is disclosed. The barrier includes a side wall having horizontal and vertical supports and a base integral to a bottom edge of the side wall. The base has horizontal supports and cross-bars and at least one pair of legs depending therefrom which allow the barrier to stand upright relative to the surface without penetration. The horizontal supports define a ballast support useful in securing the side walls to a surface free of any surface penetration by instead relying on the weight of a ballast. The horizontal supports, vertical supports and cross-bars are RF transparent. 
     In accordance with another aspect of the invention, a method for fulfilling requirements of an antenna barrier installation of a given size at an antenna location comprises the steps of receiving installation parameters concerning the antenna barrier installation at the antenna location, the installation parameters including the given size of the installation, calculating components necessary to fulfill the antenna barrier installation requirements in view of the received parameters, defining a pick list of component parts based on the calculated components which together can be assembled into a completed antenna barrier at the antenna location, and shipping the component parts in the pick list in fulfillment of the antenna barrier installation requirements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present invention may be derived by referring to the detailed description and claims when considered in connection with the Figures, wherein like reference numbers refer to similar items throughout the Figures, and: 
         FIG. 1  shows a perspective view of an antenna barrier structure surrounding a cell site radio frequency antenna; 
         FIG. 2  shows a perspective view of an antenna barrier structure for placement about a cell site radio frequency antenna; 
         FIG. 3  shows a perspective front view of the antenna barrier structure of  FIG. 2 ; 
         FIG. 4  shows a front plain view of the antenna barrier structure of  FIG. 2 ; 
         FIG. 5  shows a side plain view of the antenna barrier structure of  FIG. 2 ; and 
         FIG. 6  is a flow diagram for fulfilling the requirements of an antenna barrier installation for an antenna site. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following description is provided in the context of a particular application of the invention and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art and the features described herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown. 
     The present invention pertains to RF antenna barriers composed in-part, or entirely, of RF transparent materials, and more preferably Fiberglass Reinforced Plastic (FRP), though other RF transparent materials and plastics such as polyfoam, glass or plexiglass can be used. These materials can be and are preferably assembled at the location of the antenna. A complete RF antenna barrier kit in accordance with a preferred embodiment comprises all materials required for assembly such that on-site barrier construction can be done efficiently. Depending on specific customer requirements, a complete RF antenna kit can be packaged and shipped with or without the ballasts or epoxy described below. 
     The barriers, constructed of FRP channels, sections, connectors and bolts are available in various widths and heights to satisfy a variety of RF antenna structures and mounting environments. Structural properties of the selected material include, but are not limited to, tensile strength and dielectric constant which are to be considered in determining the material&#39;s suitability for use in the barrier, as described further below. 
       FIG. 1  shows a configuration of an embodiment of an antenna barrier structure  10  that can be used to gate a cell site RF antenna  12 . Barrier structure  10  is used to deter and prevent access to one or more cell site RF antennas  12  by partially or wholly surrounding the cell site from all accessible directions except from air space above the barrier. 
     The antenna barrier structure  10  comprises four individual barrier sections  14 ,  16 ,  18  and  20 , respectively, and can have a box-shaped configuration with a top opening. Each individual barrier section is represented without its specific constituent parts, such as cross-bars and vertical and horizontal supports, for ease of illustration. Antenna barrier structure  10  is configured for placement on the roof of building, wooded area, open field, black-top, or any other man-made or naturally occurring structure where a cell site can be installed and operated. Fasteners for securing barrier structure  10  to surface  50  are unnecessary because legs  38  and a ballast support  39  are provided which are utilized to seat the barrier, as described below. 
     Antenna barrier structure  10  is formed by coupling multiple barrier structures together, along adjacent vertical supports  28  and cross-bars  30  ( FIG. 2 ). Thus, antenna barrier structure  10  can include four RF transparent side walls  22  and bases  24  which join at respective corners  23  as shown in  FIG. 1  as well as many or all of the features described in connection with  FIGS. 2-5  below. 
     Referring to  FIG. 2 , an individual barrier section  14  is shown in detail and it is to be understood that barrier sections  16 ,  18  and  20  can be designed the same way. Antenna barrier section  14  includes a side wall  22  and a base  24  affixed to side wall  22 . More particularly, side wall  22  includes horizontal supports  26 , each horizontal support  26  being fixed at its ends between vertical supports  28 . 
     Base  24  includes horizontal supports  26 , each being fixed at its ends between cross-bars  30 . Antenna barrier section  14  further includes braces  32 . Each brace  32  is fixed at its ends at midpoints along a respective vertical support  28  and horizontal cross-bar  30  using a hinge  34 . As shown, side wall  22  and base  24  connect at their union utilizing hinges  36 . Support brace  32  provides an additional connection of the side wall and base to rigidify the antenna barrier section  14 . 
     Horizontal supports  26  and braces  32  are preferably continuous FRP members integral to barrier  14  to provide dimensional stability to the barrier and to serve as strengthening elements. Horizontal and vertical supports,  26  and  28 , respectively, cross-bars  30 , and braces  32  are preferably composed of FRP or any other RF transparent material such that interference with the cell cite is minimized. The FRP medium allows the passage of radio frequency signals, is non-conductive, non-magnetic, and resistant to degradation from environmental effects, each of which is a desirable property for the barrier structure  10 . 
     Four legs  38  are mounted to the underside of base  24  to support antenna barrier  14  above the surface  50 . Ballasts  40  ( FIG. 1 ) can be mounted to base  24  to add weight to the base and enhance the barrier&#39;s ability to withstand forces of nature such as wind. Preferably, a ballast support surface  39  is defined along a portion of the base  24  to support the ballast  40 . As shown in  FIGS. 2 and 4 , the ballast support surface  39  can be disposed away from the union of the base  24  with the side wall  22  so as to maximize the effect of the ballast  40  in resisting wind forces. The ballast support surface can take on a variety of forms. In the illustrated embodiment it comprises FRP support elements  39  connected between horizontal supports  26 . In another arrangement, the horizontal supports  26  are spaced so as to define the ballast support surface free of additional elements. In still another arrangement the ballast support surface can be a generally planar surface such as a shelf supported upon or extending between the horizontal supports  26  and/or the cross-bars  30 . Legs  38  and ballasts  40  can be composed of RF transparent materials such that they do not interfere with the RF signals transmitted and received by RF antenna  12 . The ballasts  40  preferably permit the antenna barrier to be set in position around the antenna  12  without the need for surface penetrating tools, screws or nails. An epoxy (not shown) can be used to affix legs  38  to surface  50 , and as such serves to supplement the legs ability to secure antenna barrier  14  to surface  50 . 
     In the event that the barrier support structure is to be mounted on a peaked roof or hillside, the ballast support surface preferably includes an upstanding flange or wall to engage one or more side surfaces of the ballasts  40 . In particular, the weight of the ballast  40  is supported by the ballast support surface  39 , while the flange or wall preclude the ballasts  40  from unseating from the support surface  39  due to the inclined surface of the rooftop or hillside. 
     Each of the antenna barrier sections  16 ,  18  and  20  includes side walls, bases, horizontal and vertical supports, cross-bars, braces, legs, and where appropriate, hinges, ballasts, screws and bolts to complete a respective section. In a given implementation, any of the sections can include corner panels which include horizontal supports  26  extending in more than one plane, for example, supports  26  that intersect at a common vertical support  28  and an additional vertical support  28  disposed away from the corner. 
     Referring back to  FIG. 1 , antenna barriers  14 ,  16 ,  18  and  20  can be placed about RF antenna  12  so that the resulting antenna barrier structure  10  entirely surrounds the cell site preventing access thereto. The antenna barrier sections can be tethered or joined together using conventional clips, fasteners or ties; however, it is important that any device used to secure the antenna barrier sections together be made of an RF transparent material so as not to interfere with reception of RF signals at the antenna  12 . 
     Referring to  FIGS. 2 and 3 , horizontal supports  26 , vertical supports  28 , cross-bars  30  and braces  32  include orifices  80  through which FRP screws  42  can be passed. FRP screws  82  and bolts  84  are preferably used to secure the supports, braces, cross-bars, legs, ballasts and hinges. 
       FIGS. 4 and 5  show respective front plan and side plan views of the antenna barrier structure of  FIG. 1 . As compared to the arrangement of  FIG. 2 , the horizontal supports  26  of the side wall  22  are shown mounted on a rear face of vertical supports  28 , and the braces  32  have been omitted. In all other respects this arrangement is the same as previously described. 
     With further reference to  FIG. 5 , the ballast support surface  39  is aligned with the vertical supports  28  such that the ballasts  40  optionally can be located at one or more locations along the barrier structure  20  at which the horizontal supports  26  meet the vertical supports  28 . Optionally, an RF-transparent sign and RF-transparent sign mounting hardware can be included on antenna barrier  16  to warn or instruct persons approaching the cell site. 
     Referring now to  FIG. 6 , a process flow useful for ordering an antenna barrier kit for any given installation it is described. The process flow shown in  FIG. 6  can be implemented in a variety of ways, but it is preferred the order be processed through a computer interface, such as a Web-browser based interface to a Web-compliant host machine. At block  110 , the user is instructed as to how to define the size of an installation. The size of the installation takes into account physical constraints that may limit the placement of a barrier about an antenna. For example, if an antenna seated on a flat rooftop with space all around, then the size of the installation can be defined as an area surrounding the antenna. On the other hand, for example, if the antenna is mounted is supported by a wall, then the site installation can be defined as a U-shaped region extending away from and back towards the wall so as to surround the antenna on three sides. In like manner, a site installation can be defined on a hillside or other shaped roof surface, and it is preferred that the interface for entering the installation size provide guidance to the user so that sufficient information is obtained to enable a complete set of components to be identified, selected and gathered for inclusion in the antenna barrier kit constructed as a result of a session including the steps of this process flow. At block  120 , installation parameters are input by an user. Such parameters include the desired height of the barrier anticipated wind forces, and optional other parameters concerning the dimensions of the barrier kit to be provided. Among the installation parameters that can be input is the size of the installation defined at block  110 . 
     At block  130 , calculations are performed to determined the components to be compiled into an antenna barrier kit for this installation site. The calculations take into account the dimensions of any pre-cut horizontal or vertical supports that are to be included in a given kit. For example, the components that are inspected for availability may be limited those that are presently in inventory, as determined with reference by the host machine to an inventory database, can include any known size component regardless of whether it is in inventory. As another example, the parts may include pre-cut pieces of FRP material having specific sizes to be combined so as to satisfy the installation parameters. In response to the calculating step, a pick-list of parts is defined at block  140 , with the parts representing all of the components that are necessary for creating the antenna barrier structure, except for the ballast which is supplied by the customer. Optionally, a ballast can be supplied as well. Preferably, the pick-list includes at least one ballast support  39  among the components in the kit, with or without a wall or flange to support the ballast against lateral sliding movement. 
     The components that are retrieved using the pick-list are then packed and shipped to the purchaser for installation at the site, as indicated at block  150 . The pick-list can serve as a parts list of all of the parts being provided to the user. Preferably, assembly instructions are provided with the shipment. Optionally, the assembly instructions can be tailored in response to the calculations performed and the pick-list generated so as to inform the purchaser of how the picked pieces are to be used. 
     Although the preferred embodiments of the invention have been illustrated and described in detail, it will be readily apparent to those skilled in the art that various modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims. For example, a wide variety of antenna screen structure, shapes, and sizes may be developed to best fit various cell site locations. In addition, the present invention will accommodate a wide variation in the specific tasks and the specific task ordering used to accomplish the processes described herein. 
     It is to be understood that this invention is not limited to those precise embodiments and modifications, and that other modifications and variations may be affected by one skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, any one or more features of any embodiment of the invention may be combined with any one or more other features of any other embodiment of the invention, without departing from the scope of the invention.