Patent Publication Number: US-7592960-B2

Title: High frequency capacitive coupling antenna for vehicles

Description:
TECHNICAL FIELD 
     The present invention is generally directed to an antenna system, and, more specifically, to a high frequency capacitive coupling antenna including a unique mounting arrangement that provides for accurate positioning of antenna components during both initial installation/assembly and during servicing of the antenna. 
     BACKGROUND OF THE INVENTION 
     High frequency antennas have been developed for use on vehicles to receive signals such as a radio signal from a satellite. Such antennas may include a thin layer of conductive material disposed on an inner side of the vehicle glass utilizing an etching process or other suitable process. An electrical circuit board and antenna feed wire are positioned directly adjacent the conductive element. The antenna feed wire is spaced apart from the conductive element on the glass surface and it may be encapsulated by a dielectric material. Proper operation of the antenna requires precise positioning of the antenna feed wire relative to the conductive element on the glass surface. The need to provide precise mounting of the antenna feed wire has led to difficulties in manufacture and servicing of the antenna. For example, if one of the electrical components on the circuit board fails replacement of the circuit board may be difficult because positioning of a new circuit board and antenna feed wire in the field may be quite difficult. 
     Accordingly, an antenna arrangement alleviating these difficulties would be beneficial. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention is a high frequency capacitive coupling antenna system for motor vehicles. The antenna system includes a generally planar conductive antenna element adapted to be fixed to a non-conductive component of a vehicle. A bezel includes a mounting surface configured to fixedly position the bezel relative to a surface of a non-conductive vehicle component and relative to the conductive antenna element. The bezel further includes a support surface configured to support and position an electrical circuit board. The circuit board assembly includes a board structure and a plurality of electrical circuit elements mounted to the board structure. The antenna system further includes an antenna feed wire electrically connected to the electrical circuit elements. At least a portion of the feed wire extends away from the circuit board towards the conductive antenna element. The antenna feed wire is spaced apart from the conductive antenna element, and does not directly contact the conductive antenna element. The antenna system further includes a dielectric material encapsulating the antenna feed wire. A housing is removably connected to the bezel, and a resiliently compressible member is secured to the housing and positioned between the circuit board and the housing. The circuit board is secured to the resiliently compressible member, and the resiliently compressible member biases the circuit board into contact with the support surface of the bezel and thereby positions the circuit board and antenna feed wire relative to the bezel. 
     Another aspect of the present invention is an antenna system for vehicles including a bezel having a mounting surface, guide surfaces. and at least one support surface. Adhesive disposed on the mounting surface provides for mounting of the bezel to window glass of a vehicle. The antenna system further includes a circuit board having electrical circuit elements mounted to a board structure. An antenna feed wire extends from the circuit board, and dielectric material encapsulates at least a portion of the antenna feed wire. At least a selected one of the circuit board and the dielectric material contact the mounting surface of the bezel to thereby position the antenna feed wire relative to the mounting surface of the bezel. 
     These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a partially fragmentary isometric view of a high frequency capacitive coupling antenna system according to one aspect of the present invention; 
         FIG. 2  is an exploded isometric view of the antenna system of  FIG. 1 ; 
         FIG. 3  is an exploded isometric view of the antenna system of  FIG. 1  from a different angle than that of  FIG. 2 ; 
         FIG. 4  is a cross-sectional view of the antenna system taken along the line IV-IV;  FIG. 1 ; 
         FIG. 5  is a cross-sectional view of the antenna system taken along the line V-V;  FIG. 1 ; 
         FIG. 6  is a partially exploded view of the antenna system of  FIG. 4  wherein the detachable upper assembly is detached from the bezel assembly; 
         FIG. 7  is a partially exploded view of the antenna system of  FIG. 5  wherein the detachable upper assembly is detached from the bezel assembly; and 
         FIG. 8  is a fragmentary cross-sectional view of an antenna system according to another aspect of the present invention wherein dielectric material contacts a bezel to position the circuit board and antenna lead wire. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For purposes of description herein, the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the invention as oriented in  FIG. 1 . However, it is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise. 
     With reference to  FIG. 1  a high frequency capacitive coupling antenna system  1  according to one aspect of the present invention includes an electrical unit  2  that is electrically connected to a conventional connector  3  via a coaxial cable  4 . The connector  3  connects to the electrical system (not shown) of a motor vehicle. The electrical unit  2  includes a cover or housing  5  chat is attached to a bezel  6  that is adhesively bonded to the interior surface of a vehicle glass window component  7 . A conductive antenna element  8  (see  FIG. 2 ) is disposed on the vehicle interior glass surface  7  directly adjacent and “below” the bezel  6 . It will be understood that antenna system  1  is typically oriented upside down or at an acute angle relative to a horizontal plane, and the terms “above”, “below” and the like merely refer to the orientations shown in the figures. 
     With further reference to  FIGS. 2 and 3 , electrical unit  2  comprises a detachable upper assembly  10 , and a bezel assembly  11  (see also  FIGS. 6 and 7 ). The detachable upper assembly  10  includes cover  5 , foam retainer  12 , shield  13 , circuit board assembly  14  and dielectric member  15 . An antenna feed element such as conductive wire  31  extends downwardly from circuit board  14  and capacitively couples with conductive element  8 . Antenna feed wire element  31  is fixed to a circuit board  28  of circuit board assembly  14 . Proper positioning of antenna wire element  31  relative to conductive antenna element  8  on glass  7  can therefore be accomplished by properly positioning circuit board  28  relative to glass  7 . 
     Accurate positioning of antenna feed wire  31  relative to conductive antenna element  8  is important for antenna performance. In the illustrated example, the allowable variation in the position of feed wire  31  relative to conductive antenna element  8  in a direction normal to the plane of antenna element  8  is less than 0.25 mm. The allowable variation in side-to-side positioning of feed wire  31  in the plane of antenna element  8  is 2.00 mm. 
     Bezel assembly  11  includes bezel  6  and adhesive pad or layer  16  that secures bezel  6  to vehicle glass  7 . As described in more detail below, the bezel assembly  11  is adhesively bonded to the vehicle glass  7  in a permanent manner, and upper assembly  10  detachably connects to bezel assembly  11 . As also described in more detail below, upper assembly  10  detaches from bezel assembly  11  to permit repair/replacement at a vehicle service center or the like, and the connecting arrangement between the upper assembly  10  and the bezel assembly  11  locates the circuit board  14  and antenna feed wire  31  of upper assembly  10  relative to bezel assembly  11  and relative to the conductive antenna elements  8  on the vehicle glass  7 . Accurate positioning of antenna feed wire  31  of upper assembly  10  relative to the conductive antenna element  8  ensures that the antenna system  1  operates correctly. 
     Cover  5  includes a wall or web  20 , and sidewalls  21  extending perpendicularly from the web  20 . Foam retainer  12  has a square or quadrilateral outer perimeter  22 , and an enlarged square opening  23  through a central portion of the foam retainer  12 . The upper surface  24  ( FIG. 2 ) and the lower surface  25  ( FIG. 3 ) have adhesive disposed thereon to secure the foam retainer  12  to the inner surface  26  of cover  5 , and to upper surface  27  of circuit board  28 . 
     Circuit board assembly  14  includes circuit board  28 . and a plurality of electrical components  29  and conductive elements  30 . In the illustrated example, circuit board  28  includes four side edge portions  43  that form a quadrilateral outer peripheral edge  41 . The antenna feed wire  31  ( FIG. 3 ) is electrically connected to the electrical components  29  of circuit board assembly  14 . and the antenna feed wire  31  extends downwardly away from lower surface  32  of circuit board  28 . The electrical circuit components  29  and antenna feed wire  31  are of a known design utilized for high frequency capacitive antennas, such that these components will not be described in detail herein. Shield  13  is made of tinned cold-rolled steel, and shield  13  is soldered to the circuit board assembly  14  to ground the shield  13  and secure the shield  13  to the circuit board assembly  14 . When assembled, antenna feed wire  31  is encapsulated by dielectric material or member  15 . 
     In the illustrated example, bezel  6  of bezel assembly  11  includes four sidewall portions  33  that together define a quadrilateral opening  34  through a central portion of the bezel  6 . A flange  35  extends outwardly away from sidewalls  33 . The lower surface  36  ( FIG. 3 ) of flange  35  forms a mounting surface that fits closely against glass  7  when the electrical unit  2  is installed on vehicle glass  7 . Bezel  6  includes a plurality of guide/support members  38  that extend outwardly away from sidewalls  33 . As described in more detail below, guide/support members  38  include tapered end surfaces  39  that guide circuit board  28  of detachable upper assembly  10  into position on the bezel assembly  11  both during initial assembly and during servicing after the vehicle has been in use. Bezel  6  includes a plurality of snap connectors  40  that detachably interconnect cover  5  and bezel  6 . Adhesive pad  16  has a quadrilateral shape forming an opening  37  that aligns with opening  34  through bezel  6  when assembled. The adhesive pad  16  substantially conforms to the shape and size of lower surface  36  of flange  35  of bezel  6 . In a preferred embodiment, cover  5  and bezel  6  are made of a polycarbonate material, and the foam retainer  12  is made of a resilient urethane foam with acrylic adhesive on the upper and lower surfaces  24  and  25  of foam retainer  12 , respectively, that resiliently attaches circuit board assembly  14  to housing  5 . 
     With further reference to  FIGS. 4-7  when detachable upper assembly  10  is assembled, outer peripheral edges  41  of circuit board  28  are closely received against vertical locating surfaces  42  of guide/support members  38  to position circuit board assembly  14  relative to the bezel  6  in the plane of the glass  7 . Each sidewall portion  33  of bezel  6  includes two guide/support members  38  that are configured to slidably contact edge portions  43  (see also  FIG. 2 ) of circuit board  28  during assembly of detachable upper assembly  10  with bezel assembly  11  to accurately guide and position the circuit board  28  relative to bezel  6  as circuit board  28  is brought into engagement with bezel  6 . When electrical unit  2  is assembled. lower surface  32  of circuit board  28  contacts upper edges  44  of sidewalls  33  to vertically position the Circuit board  28  relative to glass  7 , and foam retainer  12  is compressed somewhat, and therefore generates a biasing force pushing circuit board  28  into contact with edges  44  of sidewalls  33 . Also, foam retainer  12  provides for some side-to-side movement of circuit board  28  relative to cover  5 . and therefore permits the edge portions  43  of circuit board  28  to contact edges  42  of guide/support members  38  to accurately position circuit board  28  and antenna feed wire  31  relative to bezel  6  and conductive antenna element  8 , even if cover  5  is somewhat out of position in a side-to-side direction relative to bezel  6  and conductive element  8 . Snap connectors  40  are received in notches  45  in cover  5  to thereby retain cover  5  to bezel  6 . A notch  46  ( FIG. 2 ) in cover  5  receives a screw driver or the like for removal of cover  5  and detachable upper assembly  10 . 
     During assembly. the circuit board assembly  14  (including shield  13 ) is secured to foam retainer  12  utilizing adhesive, and foam retainer  12  is secured to cover  5  utilizing adhesive. Cover  5  is then attached to bezel  6 . During assembly, tapered end surfaces  39  of guide/support members  38  contact edge portions  43  of circuit board  28  if circuit board  28  is not properly aligned with bezel  6 , and the circuit board  28  is thereby guided into the proper alignment with bezel  6  as the circuit board  28  and bezel  6  are brought together. When fully assembled, lower surface  32  of circuit board  28  contacts edge portions  44  of guide/support members  38  to vertically position circuit board  28  and edge portions  43  of circuit board  28  contact edges  42  of guide/support members  38  to horizontally position circuit board  28  and antenna feed wire element  31  relative to bezel  6  and conductive antenna element  8 . It will be understood that the distance between opposite edge surfaces  42  is equal to or slightly greater than the distance between opposite edge portions  43  of circuit board  28 , such that there may be very small gaps between some of the edge portions  42  of guide/support members  38  and edge portions  43  of circuit board  28 . Also, as discussed above, foam retainer  12  is resilient and therefore allows the circuit board  28  to shift side-to-side somewhat so that circuit board  28  can seat properly against edges  42  and  44  of guide/supports  38 , and thereby properly and accurately position circuit board  28  and antenna feed wire element  31  relative to bezel  6  and antenna element  8  on glass  7 . 
     The upper assembly  10  and bezel  6  are inverted and cavity  47  bounded by lower surface  32  of circuit board  28  and sidewalls  33  is filled with liquid dielectric material to encapsulate antenna lead wire  31 . The dielectric material is then cured to form a solid member  15  encapsulating antenna lead wire  31 . Although various dielectric materials may be utilized, in the illustrated example, the dielectric material is alumina filled silicone that is cured by heating the assembly. Adhesive pad  16  is positioned on lower surface  36  of flange  35 , and the electrical unit  2  is then adhesively secured to vehicle glass  7  in the proper position relative to the conductive antenna elements  8  on vehicle glass  7 . Outer edge  48  of flange  35  protrudes beyond sidewall  21  of cover  5 , and thereby provides a surface that can be utilized by a robotic tool or the like to accurately position bezel  6  relative to vehicle glass  7  during assembly. 
     With further reference to FIG  8 , an electrical unit  2 A according to another aspect of the present invention includes a cover  5 A, foam retainer  12 A, circuit board assembly  14 A, and shield  13 A. Bezel  6 A includes tapered end surfaces  39 A with locating surfaces  42 A and upper support surface  44 A. Dielectric material  50  is formed around antenna lead wire  31 A to thereby encapsulate the lead wire  31 A. Dielectric material  50  may comprise a pre-formed ceramic material that is adhesively bonded to circuit board  28 A prior to assembly of detachable upper assembly  10 A to bezel assembly  11 A. Dielectric material  50  is preferably a ceramic material that can be formed within high tolerances, and includes precise outer surfaces  51  and  52  that engage surfaces  42 A and  44 A of guide/support members  38 A to thereby accurately position circuit board  28 A and antenna lead wire  31 A relative to bezel  6 A. Bezel  6 A is secured to vehicle glass  7  utilizing an adhesive pad  16 A that is substantially similar to the adhesive pad  16  described in detail above. 
     If antenna system  1  needs to be serviced after it has been installed to the glass  7  of a vehicle, the detachable upper assembly  10  can be removed by inserting a screw driver (not shown) into notch  46  to thereby pry cover  5  apart from bezel  6  and release snap connectors  40 . A new (replacement) detachable upper assembly  10  can then be installed to bezel  6 . Tapered end surfaces  39  of guide/support members  38  ensure that the circuit board  28  and antenna feed wire  31  are guided and supported in the proper position wherein circuit board  28  is supported and/or positioned by edges  42  and  44  of bezel  6 , and biased into contact with edges  44  by resilient foam retainer  12 . The positioning features of bezel  6 , along with foam retainer  12 , ensure accurate positioning of circuit board  28  and antenna feed wire  31  of upper assembly  10  relative to bezel  6  and antenna element  8  by service personnel, without requiring specialized mounting procedures, tools, or the like. Because the bezel  6  is permanently attached to the vehicle glass  7 , the position of the bezel  6  does not change, and the replacement circuit board and antenna feed wire are thereby properly positioned relative to the conductive antenna elements  8  on the vehicle glass  7 . 
     The antenna mounting arrangement of the present invention provides for accurate positioning of the antenna feed wire and circuit board relative to the conductive elements on the vehicle glass during both initial assembly and during servicing of the antenna system. The design of the bezel and circuit board reduces the number of parts utilized to position the circuit board and antenna feed wire, thereby reducing the number of parts and resulting difficulty in maintaining tolerance that would otherwise occur if more parts were utilized in the assembly. 
     The above description is considered that of the preferred embodiments only. Modifications of the invention will occur to those skilled in the art and to those who make or use the invention. Therefore, it is understood that the embodiments shown in the drawings and described above are merely for illustrative purposes and not intended to limit the scope of the invention, which is defined by the following claims as interpreted according to the principles of patent law, including the doctrine of equivalents.