Abstract:
Low cost antennas formed of conductive loaded resin-based materials. The conductive loaded resin-based materials are resins filled with conductive materials to provide a material which is a conductor rather than an insulator or body. The conductive materials comprise a resin-based structural material loaded with micron conductive powders or micron conductive fibers to provide a composite which is a conductor rather than an insulator. Virtually any antenna fabricated by conventional means such as wire, strip-line, printed circuit boards, or the like can be fabricated using the conductive loaded resin-based materials. The antennas can be formed using methods such as injection molding, overmolding, or extrusion.

Description:
[0001]    This Patent Application claims priority to the following U.S. Provisional Patent Applications, herein incorporated by reference:  
         [0002]    60/268,822, filed Feb. 15, 2001  
         [0003]    60/269,414, filed Feb. 16, 2001  
         [0004]    60/317,808, filed Sep. 7, 2001 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0005]    (1) Field of the Invention  
           [0006]    This invention relates to antennas formed of conductive loaded resin-based materials comprising micron conductive powders or micron conductive fibers.  
           [0007]    (2) Description of the Related Art  
           [0008]    Antennas are an essential part of electronic communication systems that contain wireless links. Low cost antennas offer significant advantages for these systems.  
           [0009]    U.S. Pat. No. 5,771,027 to Marks et al. describes a composite antenna having a grid comprised of electrical conductors woven into the warp of a resin reinforced cloth forming one layer of a multi-layer laminate structure of an antenna.  
           [0010]    U.S. Pat. No. 6,249,261 B1 to Solberg, Jr. et al. describes a direction-finding material constructed from polymer composite materials which are electrically conductive.  
         SUMMARY OF THE INVENTION  
         [0011]    Antennas are essential in any electronic systems containing wireless links. Such applications as communications and navigation require reliable sensitive antennas. Antennas are typically fabricated from metal antenna elements in a wide variety of configurations. Lowering the cost of antenna materials or production costs in fabrication of antennas offers significant advantages for any applications utilizing antennas.  
           [0012]    It is a principle objective of this invention to provide antennas fabricated from conductive loaded resin-based materials.  
           [0013]    It is another principle objective of this invention to provide antennas having two antenna elements fabricated from conductive loaded resin-based materials.  
           [0014]    It is another principle objective of this invention to provide antennas having an antenna element and a ground plane fabricated from conductive loaded resin-based materials.  
           [0015]    It is another principle objective of this invention to provide a method of forming antennas from conductive loaded resin-based materials.  
           [0016]    These objectives are achieved by fabricating the antenna elements and ground planes from conductive loaded resin-based materials. These materials are resins loaded with conductive materials to provide a resin-based material which is a conductor rather than an insulator. The resins provide the structural material which, when loaded with micron conductive powders or micron conductive fibers, become composites which are conductors rather than insulators.  
           [0017]    Antenna elements are fabricated from the conductive loaded resins. Almost any type of antenna can be fabricated from the conductive loaded resin-based materials, such as dipole antennas, monopole antennas, planar antennas or the like. These antennas can be tuned to a desired frequency range.  
           [0018]    The antennas can be molded or extruded to provide the desired shape. The conductive loaded resin-based materials can be cut, injection molded, overmolded, laminated, extruded, milled or the like to provide the desired antenna shape and size. The antenna characteristics depend on the composition of the conductive loaded resin-based materials, which can be adjusted to aid in achieving the desired antenna characteristics. Virtually any antenna fabricated by conventional means such as wire, strip-line, printed circuit boards, or the like can be fabricated using the conductive loaded resin-based materials.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    [0019]FIG. 1 shows a perspective view of a dipole antenna formed from a conductive loaded resin-based material.  
         [0020]    [0020]FIG. 2A shows a front view of the dipole antenna of FIG. 1 showing insulating material between the radiating antenna element and a ground plane.  
         [0021]    [0021]FIG. 2B shows a front view of the dipole antenna of FIG. 1 showing insulating material between both the radiating antenna element and the counterpoise antenna element and a ground plane.  
         [0022]    [0022]FIG. 2C shows an amplifier inserted between the radiating antenna element and the coaxial cable center conductor for the dipole antenna of FIG. 1.  
         [0023]    [0023]FIG. 3 shows a segment of an antenna element formed from a conductive loaded resin-based material showing a metal insert for connecting to conducting cable elements.  
         [0024]    [0024]FIG. 4A shows a perspective view of a patch antenna comprising a radiating antenna element and a ground plane with the coaxial cable entering through the ground plane.  
         [0025]    [0025]FIG. 4B shows a perspective view of a patch antenna comprising a radiating antenna element and a ground plane with the coaxial cable entering between the ground plane and the radiating antenna element.  
         [0026]    [0026]FIG. 5 shows an amplifier inserted between the radiating antenna element and the coaxial cable center conductor for the patch antenna of FIGS. 4A and 4B.  
         [0027]    [0027]FIG. 6 shows a perspective view of a monopole antenna formed from a conductive loaded resin-based material.  
         [0028]    [0028]FIG. 7 shows a perspective view of a monopole antenna formed from a conductive loaded resin-based material with an amplifier between the radiating antenna element and the coaxial cable center conductor.  
         [0029]    [0029]FIG. 8A shows a top view of an antenna having a single L shaped antenna element formed from a conductive loaded resin-based material.  
         [0030]    [0030]FIG. 8B shows a cross section view of the antenna element of FIG. 8A taken along line  8 B- 8 B′ of FIG. 8A.  
         [0031]    [0031]FIG. 8C shows a cross section view of the antenna element of FIG. 8A taken along line  8 C- 8 C′ of FIG. 8A.  
         [0032]    [0032]FIG. 9A shows a top view of an antenna formed from a conductive loaded resin-based material embedded in an automobile bumper.  
         [0033]    [0033]FIG. 9B shows a front view of an antenna formed from a conductive loaded resin-based material embedded in an automobile bumper formed of an insulator such as rubber.  
         [0034]    [0034]FIG. 10A shows a schematic view of an antenna formed from a conductive loaded resin-based material embedded in the molding of a vehicle window.  
         [0035]    [0035]FIG. 10B shows a schematic view of an antenna formed from a conductive loaded resin-based material embedded in the plastic case of a portable electronic device.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0036]    The following embodiments are examples of antennas fabricated using conductive loaded resin-based materials. In some of the examples ground planes are also used and these ground planes can be formed of either conductive loaded resin-based materials or metals. The use of these conductive loaded resin-based materials in antenna fabrication significantly lowers the cost of materials and manufacturing processes used in the assembly antennas and the ease of forming these materials into the desired shapes. These materials can be used to form either receiving or transmitting antennas. The antennas and/or ground planes can be formed using methods such as injection molding, overmolding, or extrusion of the conductive loaded resin-based materials.  
         [0037]    The conductive loaded resin-based materials typically but not exclusively have a conductivity of between about 5 and 25 ohms per square. The antenna elements, used to form the antennas, are formed of the conductive loaded resin-based materials and can be formed using methods such as injection molding, overmolding, or extrusion. The antenna elements can also be stamped to produce the desired shape. The conductive loaded resin-based material antenna elements can also be cut or milled as desired.  
         [0038]    The conductive loaded resin-based materials comprise micron conductive powders or fibers loaded in a structural resin. The micron conductive powders are formed of metals such as nickel, copper, silver or the like. The micron conductive fibers can be nickel plated carbon fiber, stainless steel fiber, copper fiber, silver fiber, or the like. The structural material is a material such as a polymer resin. Structural material can be, here given as examples and not as an exhaustive list, polymer resins produced by GE PLASTICS, Pittsfield, MA, a range of other plastics produced by GE PLASTICS, Pittsfield, MA, a range of other plastics produced by other manufacturers, silicones produced by GE SILICONES, Waterford, NY, or other flexible resin-based rubber compounds produced by other manufacturers. The resin-based structural material loaded with micron conductive powders or fibers can be molded, using a method such as injection molding, overmolding, or extruded to the desired shape. The conductive loaded resin-based materials can be cut or milled as desired to form the desired shape of the antenna elements. The composition of the composite materials can affect the antenna characteristics and must be properly controlled. The composite could also be in the family of polyesters with woven or webbed micron stainless steel fibers or other micron conductive fibers forming a cloth like material which, when properly designed in metal content and shape, can be used to realize a very high performance cloth antenna. Such a cloth antenna could be embedded in a persons clothing as well as in insulating materials such as rubber or plastic. The woven or webbed conductive cloths could also be laminated to materials such as Teflon, FR-4, or any resin-based hard material.  
         [0039]    Refer now to FIGS. 1-10B for examples of antennas fabricated using conductive loaded resin-based materials. These antennas can be either receiving or transmitting antennas. FIG. 1 shows a perspective drawing of a dipole antenna with a radiating antenna element  12  and a counterpoise antenna element  10  formed from conductive loaded resin-based materials. The antenna comprises a radiating antenna element  12  and a counterpoise antenna element  10  each having a length  24  and a rectangular cross section perpendicular to the length  24 . The length  24  is greater than three multiplied by the square root of the cross sectional area. The center conductor  14  of a coaxial cable  50  is electrically connected to the radiating antenna element  12  using a metal insert  15  formed in the radiating antenna element  12 . The shield  52  of the coaxial cable  50  is connected to the counterpoise antenna element  10  using a metal insert formed in the counterpoise antenna element  10 . The metal insert in the counterpoise antenna element  10  is not visible in FIG. 1 but is the same as the metal insert  15  in the radiating antenna element  12 . The length  24  is a multiple of a quarter wavelength of the optimum frequency of detection or transmission of the antenna. The impedance of the antenna at resonance should be very nearly equal to the impedance of the coaxial cable  50  to assure maximum power transfer between cable and antenna.  
         [0040]    [0040]FIG. 3 shows a detailed view of a metal insert  15  formed in a segment  11  of an antenna element. The metal insert can be copper or other metal. A screw  17  can be used in the metal insert  15  to aid in electrical connections. Soldering or other electrical connection methods can also be used.  
         [0041]    [0041]FIG. 1 shows an example of a dipole antenna with the radiating antenna element  12  placed on a layer of insulating material  22 , which is placed on a ground plane  20 , and the counterpoise antenna element  10  placed directly on the ground plane  20 . The ground plane  20  is optional and if the ground plane is not used the layer of insulating material  22  may not be necessary. As another option the counterpoise antenna element  10  can also be placed on a layer of insulating material  22 , see FIG. 2A. If the ground plane  20  is used it can also be formed of the conductive loaded resin-based materials.  
         [0042]    [0042]FIG. 2A shows a front view of the dipole antenna of FIG. 1 for the example of an antenna using a ground plane  20 , a layer of insulating material  22  between the radiating antenna element  12  and the ground plane  20 , and the counterpoise antenna element  10  placed directly on the ground plane  20 . FIG. 2B shows a front view of the dipole antenna of FIG. 1 for the example of an antenna using a ground plane  20  and a layer of insulating material  22  between both the radiating antenna element  12  and the counterpoise antenna element  10 .  
         [0043]    As shown in FIG. 2C, an amplifier  72  can be inserted between the center conductor  14  of the coaxial cable and the radiating antenna element  12 . A wire  70  connects metal insert  15  in the radiating antenna element  12  to the amplifier  72 . For receiving antennas the input of the amplifier  72  is connected to the radiating antenna element  12  and the output of the amplifier  72  is connected to the center conductor  14  of the coaxial cable  50 . For transmitting antennas the output of the amplifier  72  is connected to the radiating antenna element  12  and the input of the amplifier  72  is connected to the center conductor  14  of the coaxial cable  50 .  
         [0044]    In one example of this antenna the length  24  is about 1.5 inches with a square cross section of about 0.09 square inches. This antenna had a center frequency of about 900 MHz.  
         [0045]    [0045]FIGS. 4A and 4B show perspective views of a patch antenna with a radiating antenna element  40  and a ground plane  42  formed from conductive loaded resin-based materials. The antenna comprises a radiating antenna element  40  and a ground plane  42  each having the shape of a rectangular plate with a thickness  44  and a separation between the plates  46  provided by insulating standoffs  60 . The square root of the area of the rectangular square plate forming the radiating antenna element  40  is greater than three multiplied by the thickness  44 . In one example of this antenna wherein the rectangular plate is a square with sides of 1.4 inches and a thickness of 0.41 inches the patch antenna provided good performance at Global Position System, GPS, frequencies of about 1.5 GHz.  
         [0046]    [0046]FIG. 4A shows an example of the patch antenna where the coaxial cable  50  enters through the ground plane  42 . The coaxial cable shield  52  is connected to the ground plane  42  by means of a metal insert  15  in the ground plane. The coaxial cable center conductor  14  is connected to the radiating antenna element  40  by means of a metal insert  15  in the radiating antenna element  40 . FIG. 4B shows an example of the patch antenna where the coaxial cable  50  enters between the radiating antenna element  40  and the ground plane  42 . The coaxial cable shield  52  is connected to the ground plane  42  by means of a metal insert  15  in the ground plane  42 . The coaxial cable center conductor  14  is connected to the radiating antenna element  40  by means of a metal insert  15  in the radiating antenna element  40 .  
         [0047]    As shown in FIG. 5 an amplifier  72  can be inserted between the coaxial cable center conductor  14  and the radiating antenna element  40 . A wire  70  connects the amplifier  72  to the metal insert  15  in the radiating antenna element  40 . For receiving antennas the input of the amplifier  72  is connected to the radiating antenna element  40  and the output of the amplifier  72  is connected to the center conductor  14  of the coaxial cable  50 . For transmitting antennas the output of the amplifier  72  is connected to the radiating antenna element  40  and the input of the amplifier  72  is connected to the center conductor  14  of the coaxial cable  50 .  
         [0048]    [0048]FIG. 6 shows an example of a monopole antenna having a radiating antenna element  64 , having a height  71 , arranged perpendicular to a ground plane  68 . The radiating antenna element  64  and the ground plane  68  are formed of conductive plastic or conductive composite materials. A layer of insulating material  66  separates the radiating antenna element  64  from the ground plane  68 . The height  71  of the radiating antenna element  64  is greater than three times the square root of the cross sectional area of the radiating antenna element  64 . An example of this antenna with a height  71  of 1.17 inches performed well at GPS frequencies of about 1.5 GHz.  
         [0049]    [0049]FIG. 7 shows an example of the monopole antenna described above with an amplifier  72  inserted between the center conductor  14  of the coaxial cable  50  and the radiating antenna element  64 . For receiving antennas the input of the amplifier  72  is connected to the radiating antenna element  64  and the output of the amplifier  72  is connected to the center conductor  14  of the coaxial cable  50 . For transmitting antennas the output of the amplifier  72  is connected to the radiating antenna element  64  and the input of the amplifier  72  is connected to the center conductor  14  of the coaxial cable  50 .  
         [0050]    [0050]FIGS. 8A, 8B, and  8 C shows an example of an L shaped antenna having a radiating antenna element  80  over a ground plane  98 . The radiating antenna element  80  and the ground plane  98  are formed of conductive loaded resin-based materials. A layer of insulating material  96  separates the radiating antenna element  64  from the ground plane  98 . The radiating antenna element  80  is made up of a first leg  82  and a second leg  84 . FIG. 8A shows a top view of the antenna. FIG. 8B shows a cross section of the first leg  82 . FIG. 8C shows a cross section of the second leg  84 . FIGS. 8B and 8C show the ground plane  98  and the layer of insulating material  96 . The cross sectional area of the first leg  82  and the second leg  84  need not be the same. Antennas of this type may be typically built using overmolding technique to join the conductive resin-based material to the insulating material.  
         [0051]    Antennas of this type have a number of uses. FIGS. 9A and 9B show a dipole antenna, formed of conductive loaded resin-based materials, embedded in an automobile bumper  100 , formed of insulating material. The dipole antenna has a radiating antenna element  102  and a counterpoise antenna element  104 . FIG. 9A shows the top view of the bumper  100  with the embedded antenna. FIG. 9B shows the front view of the bumper  100  with the embedded antenna.  
         [0052]    The antennas of this invention, formed of, can be used for a number of additional applications. Antennas of this type can be embedded in the molding of a window of a vehicle, such as an automobile or an airplane. FIG. 10A shows a schematic view of such a window  106 . The antenna  110  can be embedded in the molding  108 . Antennas of this type can be embedded in the plastic housing, or be part of the plastic shell itself, of portable electronic devices such as cellular phones, personal computers, or the like. FIG. 10B shows a schematic view of a segment  112  of such a plastic housing with the antenna  110  embedded in the housing  112 .  
         [0053]    While the invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the invention.