Abstract:
An antenna including a first FM portion and first and second AM portions. The first AM portion at least partially circumscribes the first FM portion and the second AM portion at least partially circumscribes the first AM portion and at least partially circumscribes the first FM portion.

Description:
TECHNICAL FIELD 
   This invention generally relates to vehicle radio antennas and more specifically relates to vehicle radio antennas which are integrated with the vehicle windows. 
   BACKGROUND OF THE INVENTION 
   In order to enhance a vehicle&#39;s aesthetic qualities, it is common to integrate the vehicle radio antennas with one or more of the vehicle&#39;s windows (commonly known as hidden antenna systems or on-glass AM/FM antenna system). Unlike mast (rod) antennas, on-glass antenna systems do not introduce any external vehicle protrusions and they typically offer excellent mechanical stability and satisfactory reception performance. Although on-glass antennas are widely used, they do suffer from various drawbacks. Specifically, on-glass antennas are difficult to design because a small change in a vehicle&#39;s body design can radically change the reception performance of the antenna. 
   On-glass antenna systems are usually fabricated by printing metallic conductors on an inner surface of the back-glass or the side-glass of a vehicle window. A low-noise-amplifier (LNA) circuit is typically mounted in close proximity to the on-glass antenna and is electrically coupled to the on-glass antenna to amplify the weak signal received by the antenna before it is sent to the radio receiver for further conditioning. The on-glass antennas are typically fed vertically (close to the vehicle roof) so that the LNA circuit can be housed in the vicinity where the vehicle roof intersects the window. Recently, vehicle designers have found it advantageous to place side-airbags in the locations where the LNA circuits have traditionally resided. Accordingly, new feed points for the on-glass antennas and for the placement of the LNA are required. The most obvious approach is to simply rotate the current on-glass antenna design by 90 degrees which would enable a horizontal feed from the LNA circuit to the on-glass antenna. However, this approach has been shown to tremendously degrade the reception performance of the on-glass antenna rendering its reception quality so poor that it no longer meets the performance specified by many vehicle manufacturers. 
   This invention sets forth various on-glass window grid antenna designs that can be fed horizontally while still maintaining excellent reception performance characteristics. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an environmental view of the on-glass antenna of the present invention; 
       FIG. 2  is a first embodiment of the on-glass antenna of the present invention; 
       FIG. 3  is a second embodiment of the on-glass antenna of the present invention; 
       FIG. 4  is a third embodiment of the on-glass antenna of the present invention; 
       FIG. 5  is a fourth embodiment of the on-glass antenna of the present invention; 
       FIG. 6  is a fifth embodiment of the on-glass antenna of the present invention; 
       FIG. 7  is a sixth embodiment of the on-glass antenna of the present invention; 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Six embodiments of the present invention are included in this disclosure. Although all six of the embodiments are disclosed in conjunction with side glass implementation, it is to be understood that the embodiments are not limited to side glass implementation and that they can just as easily be implemented on the rear glass or the front windshield of a vehicle. 
   Now referring to  FIGS. 1 and 2 , in a first embodiment, the on-glass antenna of the present invention includes two main feeds  10 ,  12 . Main feed  10  is associated with the implementation of an AM antenna and main feed  12  is associated with the implementation of an FM antenna. Main FM feed segment  12  extends generally horizontally across side glass  9  and splits into generally parallel, bifurcated forks comprising upper FM antenna segment F 2  and lower FM antenna segment F 1 . 
   Main AM feed segment  10  bifurcates into first AM feed segment  14  and second AM feed segment  16 . Both AM feed segments  14 ,  16  extend generally vertically from main AM feed  10  wherein first AM feed segment  14  extends generally downwardly from main AM feed  10  and wherein second AM feed segment  16  extends generally upwardly from main AM feed segment  10 . First AM feed segment  14  branches into lower AM antenna pair  24  consisting of antenna segments A 1  and A 2 . Second AM feed segment  16  branches into upper AM antenna pair  22  consisting of antenna segments A 3  and A 4 . Antenna segments A 1 , A 2  extend generally horizontally from their common branch point  32  and, likewise, antenna segments A 3 , A 4  extend generally horizontally from their common branch point  30 . 
   Antenna segments A 2 , A 3  are connected to one another by way of generally vertical AM antenna connector segment A 5 . Antenna segments A 1  and A 4  are connected to one another by way of generally vertical AM antenna connector segment A 6 . A first, inner loop AM antenna  34  is formed from segments  16 , A 3 , A 5 , A 2 , and  14 . A second, outer loop AM antenna is formed from segments  16 , A 4 , A 6 , A 1 , and  14 . Although inner loop AM antenna  34  and outer loop AM antenna  36  share common elements  14 ,  16  they are also respectively comprised of non-shared elements. For example, inner loop  34  includes generally linear elements A 3 , A 5 , and A 2 . None of which are common to outer loop AM antenna  36 . In contrast, outer loop AM antenna  36  includes, in part, antenna segments A 4 , A 6 , and A 1 —none of which are common to inner loop AM antenna  34 . At least a portion of inner loop antenna  34  is completely contained within a portion of outer loop antenna. Specifically, antenna segments A 3 , A 5 , and A 2  are circumscribed by outer loop AM antenna segments A 4 , A 6 , and A 1 . It is also important to note that upper FM antenna segment F 2  and lower FM antenna segment F 1  are completely circumscribed by both inner loop AM antenna  34  and outer loop AM antenna  36 . 
   Although the exact causal connection is uncertain, it is speculated that the juxtaposition of FM antenna segments F 1  and F 2  surrounded by inner loop AM antenna  34  and outer loop AM antenna  36  gives rise to significant improvements in the reception performance of the FM antenna ( 12 , F 1 , and F 2 ). Preferably the perimeter of both inner and outer loop AM antennas  34 ,  36  is much smaller than the operation wave length of the FM antenna ( 12 , F 1 , and F 2 ). It is possible that the superior performance of the FM antenna is due to the combination of the horizontal FM antenna segments F 1 , F 2  and the inner and outer loop AM antennas  34 ,  36  which together may provide a round linear polarization pattern which may generate a small gain difference between the maximums and minimums of the pattern. 
   Now referring to  FIG. 3 , a second embodiment of the on-glass antenna system of the present invention include the elements and layout of the first embodiment, but in addition it includes, first and second jumper segments A 7 , A 8  respectively. Both first and second jumper segments A 7 , A 8  are connected between inner loop AM antenna  34  and outer loop AM antenna  36 . Specifically, first and second intersections  42 ,  44 , are respectively formed on inner loop AM antenna  34  (intersection  42  is formed at the junction of segment A 2  and A 5 , wherein intersection  44  is formed at the junction of A 3  and A 5 ). Third and fourth intersections  46 ,  48  are formed along outer loop AM antenna  36 . Specifically, intersection  46  is formed at the junction between segment A 1  and A 6  and intersection  48  is formed at the intersection of A 4  and A 6 . First jumper segment  38  extends between first intersection  42  and third intersection  46  wherein second jumper segment  40  extends between second intersection  44  and fourth intersection  48 . First and second jumper segments  38 ,  40  extend generally horizontally and they are generally parallel to one another. Segments A 2  and A 7  are generally straight segments and, in the embodiment of  FIG. 3 , they are co-linear. 
   The embodiment of  FIG. 3  also includes a third FM antenna segment  50  (F 3 ) which extends generally horizontal and parallel with upper and lower FM antenna segments F 1 , F 2 . 
   Now referring to  FIG. 4 , third embodiment is shown having all elements depicted in the embodiment of  FIG. 3  but in addition thereto, a third jumper segment  52  is added to inner loop AM antenna  34 . Specifically, third jumper segment  52  extends between generally vertical AM antenna connector segment  26  and first AM feed segment  14 . Thus, segment  52  is connected in a parallel electrical circuit to segment A 2 . In all other ways, the embodiment of  FIG. 4  is identical to the embodiment of  FIG. 3 . 
   Now referring to  FIG. 5 , the fourth embodiment of the present invention is identical to the embodiment set forth in  FIG. 4  except that floating segment  52  does not terminate at generally vertical AM antenna connector segment  26  but rather terminates  54  short of segment  26 . In all other ways the embodiment set forth in  FIG. 5  is identical to the embodiment of  FIG. 4 . 
   Now referring to  FIG. 6 , in the fifth embodiment of the on-glass antenna of the present invention, floating segment  52  is not contained within inner loop AM antenna  34  but rather resides outside of outer loop antenna  36  ( 16 , A 4 , A 6 , A 1  and  14 ). Floating segment  52  extends generally horizontally and generally parallel to lower AM antenna pair  24 . In all other ways the embodiment of  FIG. 6  is identical to that disclosed in  FIG. 5 . 
   Now referring to  FIG. 7 , in a sixth embodiment of the on-glass antenna of the present invention is identical to the embodiment set forth in  FIG. 4  except that in  FIG. 7 , first jumper segment  38  is co-linear with third jumper segment  52  (this is in contrast to the embodiment of  FIG. 4  wherein first jumper segment  38  is co-linear with antenna segment A 2 ). 
   All of the embodiments disclosed herein have a preferred range of antenna conductor width of 0.25 mm to 1.50 mm. 
   It is recognized that those skilled in the art may make various modifications or additions to the embodiments chosen here to illustrate the present invention, without departing from the spirit of the present invention. Accordingly, it is to be understood that the subject matter sought to be afforded protection hereby should be deemed to extend to the subject matter defined in the appended claims, including all fair equivalents thereof.