Abstract:
A hidden antenna system is disclosed. The hidden antenna system includes an external vehicle component, such as, an article carrier. The article carrier includes a removable portion attached to a fixed portion that defines a cavity. An antenna element is housed within the cavity in the article carrier. According to an embodiment, an end cap structure that elevates and supports a side rail over a vehicle roof includes the removeable portion and fixed portion. According to an embodiment, the article carrier includes a first and second cavity that houses a first and second antenna element, respectively, within the first and second cavities, such that the at least two antennta elements operate in a diversity application.

Description:
FIELD  
       [0001]     The invention relates to article carriers. More particularly, the invention relates to an article carrier including an antenna element.  
       BACKGROUND  
       [0002]     Article carriers, which are also referred to in the art as roof racks or luggage carriers, are typically mounted over an outer surface of a vehicle, such as a roof portion or trunk deck lid. The article carrier typically includes at least one side rail and/or cross rail, which may be formed of any desirable material, such as a plastic material or metallic material. The primary function of an article carrier is to increase the storage capacity of a vehicle by allowing items to be stored over a vehicle&#39;s outer surface.  
         [0003]     Due to the optimal radiating location on the roof portion or trunk deck lid, article carriers have also been utilized to function as, or, provide support for an antenna or antenna assembly. A known article carrier, which is described in U.S. Pat. No. 4,535,336 to Shaver, is shown generally at  100  in  FIGS. 5 and 6 . The article carrier  100  includes front and rear cross rails  102 ,  104 , and left and right side rails  106 ,  108  that are supported by stanchions  110 , which are secured to a vehicle roof portion  112  by sheet metal screws  114  and plastic bushings (not shown). A television transformer  116  is connected to the cross rails  102 ,  104  and side rails  106 ,  108  with conductive leads  118  by screws  120 . In operation, the article carrier  100  functions as a dipole antenna for reception of television signals.  
         [0004]     Another known article carrier, which is described in U.S. Pat. No. 5,629,712 to Adrian et al., is shown generally at  200  in  FIG. 7 . The article carrier  200  is shown to include a cross rail  202  and a sheet metal roof portion  204 . The sheet metal roof portion  204  provides a ground plane. The cross rail  202  conceals a conducting loop antenna  206 . Concealed in the roof portion  204  is a coaxial cable  208  that is connected to the conducting loop antenna  206 . In operation, the article carrier  200  functions as a dual FM slot and AM monopole antenna.  
         [0005]     Although adequate in receiving television signals, AM signals, and FM signals, the article carriers  100 ,  200  include a plurality of structural components and associated manufacturing steps that increase cost while making serviceability of the article carrier  100 ,  200  more complex and time consuming. Even further, known article carriers do not provide an antenna element or antenna assembly for reception of higher frequency signals, such as, for example, signals relating to personal communication systems/advanced mobile phone service (PCS/AMPS), global positioning systems (GPS), satellite digital audio radio services (SDARS), and the like.  
         [0006]     A need therefore exists for an improved article carrier that provides reception for higher frequency signals, functions as a concealing element for an antenna element, and maintains eye-pleasing vehicle aesthetics and antenna performance. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     The inventors of the present invention have recognized these and other problems associated with article carriers. The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
         [0008]      FIG. 1  is a top perspective view of an article carrier according to an embodiment;  
         [0009]      FIG. 2  is an exploded view of the article carrier according to  FIG. 1 ;  
         [0010]      FIG. 3  is a perspective view of an antenna element according to an embodiment that is concealed by the article carrier of  FIG. 1 ;  
         [0011]      FIG. 4  is an exploded view of the antenna element according to  FIG. 3 ;  
         [0012]      FIG. 5  is a perspective view of a conventional article carrier including an antenna;  
         [0013]      FIG. 6  is a magnified view of the conventional article carrier of  FIG. 5 ; and  
         [0014]      FIG. 7  is a perspective view of another conventional article carrier including an antenna. 
     
    
     DESCRIPTION  
       [0015]     The above-described disadvantages are overcome and a number of advantages are realized by an inventive article carrier, which is shown generally at  10  in  FIGS. 1 and 2 . As illustrated, the article carrier  10  include side rails  12 ,  14  and cross rails  16 ,  18 . Pairs of end cap structures  20  are secured to the vehicle roof  22 . The end cap structures  20  elevate and provide support for the side rails  12 ,  14 .  
         [0016]     Referring to  FIG. 2 , each end cap structure  20  includes a fixed portion  24  and a removable portion  26 . The fixed portion  24  is secured to the vehicle roof  22  and is attached to the side rail  12 ,  14 . The removable portion  26  may be snap fit, locked, or secured to the fixed portion  24  in any desirable manner. When the removable portion  26  is attached to the fixed portion  24 , a cavity  28  is defined for housing an antenna element  30 . Although four end cap structures  20  and four associated antenna elements  30  are shown, it will be appreciated that any desirable number of end cap structures  20 , antenna elements  30 , or side rails  12 ,  14  may be incorporated into the design of the article carrier  10 .  
         [0017]     The end cap structure  20  includes a thermoplastic material that permits reception and transmission of signals, S ( FIG. 1 ), to and from the antenna element  30 . For example, the end cap structure  20  may include polycarbonate-Acrylonitrile-Butadiene-Styrene (PC/ABS). The thermoplastic material that is used to form the end cap structure  20  is commercially available from General Electric Corporation of New York, N.Y., and is sold under the trade-name GELOY®. According to an embodiment, the signals, S, may be terrestrial signals, or, as shown in  FIG. 1 , high frequency signals from a satellite  75 . The frequency of the signals, S, may range, for example, between approximately 540-1700 kHz (i.e. the AM frequency range), 88.1-107.9 MHz (i.e. the FM frequency range), 824-894 MHz (i.e. the AMPS frequency range), 1563-1587 MHz (i.e. the GPS frequency range), 1850-1990 MHz (i.e., the PCS frequency range), 2320-2345 MHz (i.e. the SDARS frequency range), or the like.  
         [0018]     Referring to  FIGS. 3 and 4 , the antenna element  30  generally comprises a cover portion  32 , a circuit board assembly  34 , a case  36 , and an optional metal ground plane  38 . The ground plane  38  may be an optional element if the vehicle roof  22  does not comprise a metallic material. The cover portion  32  may include any desirable thermoplastic material and may be formed using any desirable method, such as injection molding. The case  36  is a conductive enclosure including a metal-impregnated thermoplastic resin, such as, for example, PC/ABS, and may also be formed, for example, by injection molding. As illustrated, the case  36  encloses the circuit board assembly  34 . The metal elements impregnated in the PC/ABS may include, for example, nickel plated graphite fibers and/or carbon fiber segments, and be in the form of pellets, shavings, or fibers that are mixed with the PC/ABS material prior to the injection molding operation. According to another embodiment, the case  36  may include a conductive paint applied to a thermoplastic case. Alternatively, in yet another embodiment, the case  36  may include a metal-formed “can” enclosure that may be applied to a, thermoplastic case. When the antenna element  30  is activated, the metal elements in the case  36  provide a capacitive coupling between the circuit board assembly  34  and the vehicle roof  22  or ground plane  38 .  
         [0019]     As shown in  FIG. 4 , the circuit board assembly  34  is received by the case  36 . The case  36  also includes a peripheral flange  40  that receives a bottom periphery  42  of the cover portion  32 . The case  36  also includes a passage  44  for permitting extension of a cable  46  from the circuit board assembly  34 . The cable  46  may be extended through the vehicle roof  22  to electronics within the vehicle. However, it will be appreciated that the cable  46  may be eliminated and the antenna element  30  may be electromagnetically coupled to communicate signals through the vehicle roof  22  so that a passage does not have to be provided in the vehicle roof  22  for the cable  46 . The cover portion  32  is shaped to include an embossed portion  48  for receiving a low noise amplifier and patch antenna element  50  of the circuit board assembly  34 . When placed over the peripheral flange  40  of the case  36 , the cover portion  32  encapsulates the circuit board assembly  34 .  
         [0020]     Once assembled as shown in  FIG. 3 , the peripheral flange  40  of the case  36  is ultrasonically welded to the bottom periphery  42  of the cover portion  32  to define a welded seam  52 , which seals the circuit board assembly  34  from contaminates and the like. In an alternative embodiment, frictional snaps, or other types of fastening devices, may be used in conjunction with a perimeter gasket to hold together and seal the assembly. The antenna element  30 , may generally include a diameter, D, approximately equal to 35.0 mm and a height, Y, approximately equal to 12.5 mm.  
         [0021]     If the ground plane  38  is incorporated with the antenna element  30 , the case  36  may include a pair of integrated fastening portions  54  ( FIG. 4 ) that extend from a bottom portion  56  of the case  36  for reception at receiving portions  58  in the ground plane  38 . The ground plane  38  may further comprise a plurality of resilient tabs  60  and/or guide flanges  62  for securing the antenna element  30  to a structural element, such as the fixed portion  24  of the end cap structure  20  or the vehicle roof  22 . If the ground plane  38  is not incorporated with the antenna element, the case  36  may be adhesively secured to the fixed portion  24  of the end cap structure  20  or vehicle roof  22 ; alternatively, the case  36  may include similar resilient tabs and/or guide flanges as similarly shown with the ground plane  38 .  
         [0022]     Referring to  FIGS. 1 and 2 , a plurality of antenna elements  30  are shown within the article carrier  10  for implementation in a diversity application where the plurality of antennas elements  30  are utilized to improve antenna performance. As is known in the art, if a first antenna in a diversity application loses reception of an expected signal, the diversity application will poll the other antennas in the application for expected signal reception so that the diversity system will switch to a different antenna that is receiving the expected signal while the reception of the expected signal by the first antenna is temporarily unavailable. Because the article carrier  10  extends generally from a front to rear portion of the vehicle roof  22 , the antenna elements  30  may be spaced apart at multiple locations on the vehicle roof  22  for optimized expected signal reception in the diversity application.  
         [0023]     Accordingly, the article carrier  10  provides a dual function as a roof rack for stowing articles, such as luggage, while also providing structure for concealing one or more antenna elements  30  in a “hidden antenna” system. Because the antenna elements  30  include a relatively small patch antenna element  50 , the antenna elements  30  are optimally sized for being housed in a hidden antenna system within the article carrier  10 . As such, because the antenna elements  30  are hidden from sight within the article carrier  10 , an aesthetically-pleasing look to the vehicle is thereby maintained. Additionally, because each end cap structure  20  includes a removable portion  26 , the antenna elements  30  may be easily serviced due to the simplified structure of the end caps  20  of the article carrier  10 . Even further, because the article carrier  10  may house multiple antenna elements  30 , signal reception may be maintained in a diversity application.  
         [0024]     Although the illustrated embodiments of the article carrier  10  show a removable portion  26  of an end cap structure  20 , it will be appreciated that a fixed portion and a removable portion may be included in any desirable structural element of the article carrier  10 , such as, for example, the side rails  12 ,  14  and/or cross rails  16 ,  18  such that the antenna elements  30  may be housed within a cavity of any of the rails  12 - 18 . Even further, it will be appreciated that structures other than an article carrier  10 , such as, for example, a spoiler, a third brake light housing, or a tail lamp, may include a fixed portion and a removable portion for housing an antenna element  30  in a hidden antenna application.  
         [0025]     While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit.