Abstract:
A low-profile antenna according to exemplary embodiments generally includes a patch antenna enclosed in a housing, and a directional element for directing a direction of sensitivity for the patch antenna. The directional element is positioned on the external surface of the housing. A protective lens may be positioned over the directional element. In one exemplary embodiment, the directional element is formed from a layer of conductive material. In another exemplary embodiment, the directional element is formed from conductive ink containing silver particles.

Description:
FIELD 
       [0001]    The present disclosure relates to patch antennas. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0003]    A patch antenna is a narrowband, wide-beam antenna that includes an active antenna element bonded to a dielectric substrate. Patch antennas have a low profile compared to aerial antennas and are mechanically rugged. Patch antennas are therefore suitable for mounting on the exterior of vehicles to receive satellite signals, such as Satellite Digital Audio Radio Services (SDARS). 
         [0004]    A patch antenna for automotive use is generally positioned on the roof, hood, or trunk lid to help ensure that the antenna has an unobstructed view overhead or towards the zenith. A receiving sensitivity or directivity of the antenna should also be directed towards the zenith. To this end, the patch antenna can include a passive director element that focuses the receiving sensitivity towards zenith. 
         [0005]    Referring now to  FIG. 1 , a cross-sectional view is shown of a conventional patch antenna assembly  10  of the prior art. The assembly  10  includes a patch antenna  12  that is enclosed within a protective cover  14 . A directional element  16  is positioned on an interior roof of the cover  14 . The directional element  16  is concentric with the patch antenna  12  and increases directivity of the assembly  10  towards the zenith, which is indicated by an arrow Z. 
         [0006]    An air gap between the patch antenna  12  and the directional element  16  has a height of H 1 . The magnitude of H 1  is based on a center frequency of the patch antenna  12  and a desired degree of directional gain. The height H 1  must be controlled when the patch antenna assembly  10  is assembled and thereafter remain stable to achieve and maintain the desired degree of directivity. 
       SUMMARY 
       [0007]    An antenna assembly includes a patch antenna that receives radio signals. A passive directional element increases the patch antenna gain in a particular direction. A protective cover shields the patch antenna from the environment. The patch antenna is positioned adjacent an interior surface of the protective cover, and the directional element is positioned on an exterior surface of the protective cover. 
         [0008]    In other features, a distance between the interior and exterior surfaces is between about one millimeter and about two millimeters, inclusive. The directional element can be formed from aluminum. The directional element can be a conductive ink. The conductive ink can include silver particles. The directional element can include a graphic design. A protective shield can be positioned on the directional element. The protective shield can be between about 0.5 millimeter and about 2.5 millimeters thick, inclusive. The protective shield can be formed from transparent plastic. The protective cover can be formed from a dielectric material. The dielectric material can be a thermoplastic. The patch antenna is tuned to a center frequency between about 2.320 GHz and about 2.345 GHz, inclusive. 
         [0009]    In one exemplary embodiment, an antenna assembly includes a patch antenna that receives radio signals. A cover is formed to define a space that houses the patch antenna. The cover includes an exterior surface that is exposed to the environment. A passive directional element is positioned on the exterior surface and cooperates with the patch antenna to establish a dominant direction of sensitivity for the antenna assembly. 
         [0010]    In some features, a thickness of the cover between the patch antenna and the passive directional element is between about one millimeter and about two millimeters, inclusive. The directional element can be a conductive ink. The conductive ink may include silver particles. The antenna assembly can further include a transparent protective cover that is positioned on the directional element. The conductive ink may be printed on the transparent protective cover. The antenna assembly can further include an adhesive that adheres the directional element to the exterior surface of the cover. 
         [0011]    In another exemplary embodiment, an antenna assembly includes a patch antenna that receives radio signals. A cover is formed to define a space that houses the patch antenna. The cover includes an exterior surface that is exposed to the environment. A decal assembly is positioned on the exterior surface of the cover. The cover includes a dielectric material. A directional element is formed of conductive ink printed on the dielectric material. An adhesive is applied to the directional element that adheres to the exterior surface of the cover. 
         [0012]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
     
       DRAWINGS 
         [0013]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0014]      FIG. 1  illustrates a cross sectional view of a prior art patch antenna assembly; 
           [0015]      FIG. 2  illustrates a perspective view of an improved patch antenna assembly; 
           [0016]      FIG. 3  illustrates a cross sectional view of the improved patch antenna assembly of  FIG. 2 ; and 
           [0017]      FIG. 4  illustrates an exploded view of the improved patch antenna assembly of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0019]    Referring now to  FIG. 2 , an improved patch antenna assembly  20  is shown positioned on a vehicle roof  22 . In preferred embodiments, the improved antenna assembly  20  can provide a lower overall height than prior art patch antenna assemblies for similar applications. In addition, the improved antenna assembly  20  can also provide improved dimension control for a distance between a passive directional element  24  and a patch antenna  26  (shown in  FIG. 3 ) that is located within a housing  28 . A cable  30 , such as a suitable coaxial cable, communicates received signals from the assembly  20  to a radio receiver (not shown). The housing  28  can be formed from a thermoplastic, such as GE Plastics Geloy® XP4034 Resin, although other suitable or equivalent materials can be used for the housing  28 . 
         [0020]    Referring now to  FIG. 3 , a cross-sectional view is shown of assembly  20  and taken along the section line  3 - 3  shown in  FIG. 2 . The patch antenna  26  is positioned on a circuit board  32 . The circuit board  32  is secured to a chassis  34 . In some embodiments, the chassis  34  is die cast from zinc. The housing  28  encloses the aforementioned items. 
         [0021]    The directional element  24  can be positioned on an external surface of the housing  28 . In some embodiments, a protective layer or shield  38  protects the directional element  24  from weather and the elements. In some embodiments, a conductive ink can be used to print the directional element  24  on one surface of the protective layer  38 . In some embodiments, the conductive ink can include silver particles. In other embodiments, the directional element  24  can be formed from one or more layers of electrically-conductive material, such as a metallic tape. In further embodiments, the directional element  24  can be formed from sheet aluminum. In still other embodiments, the protective layer  38  is formed from urethane or an equivalent material. In some embodiments, the protective layer  38  is transparent. Alternatively, other embodiments can include a protective layer  38  that is substantially transparent or translucent. 
         [0022]    With continued reference to  FIG. 3 , a portion of the housing  28  has a thickness H 2  and is sandwiched between the patch antenna  26  and the directional element  24 . In this particular embodiment, the sandwiched portion of the housing  28  improves the dimensional control and stability between the patch antenna  26  and the directional element  24 . The distance H 2  is preferably based on the wavelength of the frequencies received by the antenna assembly  20 . In some embodiments, such as for frequencies currently used with SDARS, the thickness H 2  is between about one millimeter and about two millimeters, inclusive. For example, one embodiment includes a thickness H 2  of one millimeter. Another embodiment includes a thickness H 2  of two millimeters. Still further embodiments can include a thickness H 2  that is slightly less than one millimeter, slightly more than one millimeter, or somewhere in-between one millimeter and two millimeters. 
         [0023]    The protective layer  38  has a thickness H 3  for limiting capacitive coupling between the directional element  24  and environmental moisture. Capacitive coupling can degrade the reception performance of the antenna assembly  20 . In some embodiments, the thickness H 3  is between about 0.5 millimeter and about 2.5 millimeters, inclusive. For example, one embodiment includes a thickness H 3  of 0.5 millimeter. Another embodiment includes a thickness H 3  of 2.5 millimeters. Still further embodiments can include a thickness H 3  that is slightly less than 0.5 millimeter, slightly more than 2.5 millimeters, or somewhere in-between 0.5 millimeter and 2.5 millimeters. In some embodiments a thickness H 3  of 1.43 millimeters is preferred. 
         [0024]    Referring now to  FIG. 4 , an exploded view is shown of the antenna assembly  20 . In this illustrated embodiment, the printed circuit board  32  can be secured with screws  40  to the chassis  34 . Alternatively, the printed circuit board  32  may be secured using other suitable means. 
         [0025]    One end of the coaxial cable  30  can include a strain relief  42  that interfaces with the chassis  34  and housing or protective cover  28 . The other end of cable  30  can include a connector  44  that mates with a radio receiver (not shown). 
         [0026]    The directional element  24  can include text, a logo, a graphic element, or other indicia. In some embodiments, the directional element  24  is printed on one surface of the protective shield  38 . An adhesive is then applied to the otherwise exposed surface of the printed directional element  24 . The protective shield  38 , directional element  24 , and the adhesive are thereby layered and form a decal that can be adhered to the protective housing or cover  28 . 
         [0027]    Certain terminology is used herein for purposes of reference only, and thus is not intended to be limiting. For example, terms such as “upper”, “lower”, “above”, and “below” refer to directions in the drawings to which reference is made. Terms such as “front”, “back”, “rear”, “bottom” and “side”, describe the orientation of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import. Similarly, the terms “first”, “second” and other such numerical terms referring to structures do not imply a sequence or order unless clearly indicated by the context. 
         [0028]    When introducing elements or features and the exemplary embodiments, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of such elements or features. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements or features other than those specifically noted. It is further to be understood that the method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order or performance. It is also to be understood that additional or alternative steps may be employed. 
         [0029]    Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.