Abstract:
An antenna for receiving and/or transmitting electromagnetic signals is disclosed. The antenna includes a ground plane with a length and having a vertical axis along the length, and a dipole radiating element projects outwardly from a surface of the ground plane. The radiating element includes a feed section, and a ground section.

Description:
RELATED APPLICATION 
     This application claims the benefit under 35 U.S.C. 119 (e) of U.S. provisional patent application Ser. No. 60/779,241, filed on Mar. 3, 2006, incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to broadband base station antennas for wireless communications systems. 
     BACKGROUND OF THE INVENTION 
     The number of base station antennas needed for cellular and other wireless communications applications is increasing rapidly due to increased use of mobile wireless communications. Therefore, it is desirable to design low cost base station antennas. At the same time such wireless applications increasingly will require wideband capability. Most of the previous approaches to such antenna designs are dipole antennas with fish hook type of balun feed with various arrangements. Such systems are not readily compatible with the desired goals of low cost and wide bandwidth. Accordingly, a need presently exists for an improved base station antenna design. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a broadband single vertical polarized base station antenna and assembly that addresses the above shortcomings. In one embodiment, the present invention provides an antenna assembly for receiving and/or transmitting electromagnetic signals, comprising a ground plane and at least one dipole antenna, wherein each dipole antenna includes a first conductor extending transversely from a surface of the ground plane, the first conductor having a first radiating element projecting outwardly therefrom; and a second conductor coupled to the ground plane by a dielectric and extending transversely relative to the surface of the ground plane spaced from the first conductor, the second conductor having a second radiating element projecting outwardly therefrom. Further, the first and second conductors are spaced from one another by a gap, and the first and second radiating elements project outwardly in essentially opposite directions. 
     In another embodiment, the present invention provides a broadband single vertical polarized base station comprising a ground plane and an antenna assembly including multiple dipole antennas. Each dipole antenna, comprises a first conductor extending transversely from a surface of the ground plane, the first conductor having a first radiating element projecting outwardly therefrom; and a second conductor coupled to the ground plane by a dielectric and extending transversely relative to the surface of the ground plane spaced from the first conductor, the second conductor having a second radiating element projecting outwardly therefrom. Further, the first and second conductors are spaced from one another by a gap, and the first and second radiating elements project outwardly in essentially opposite directions. A feed line is coupled to said first conductor of each dipole antenna and spaced from said ground plane by an air dielectric, wherein the feed line provides a common input to the dipole antennas. 
     In another embodiment, the present invention provides an antenna for receiving and/or transmitting electromagnetic signals, comprising a ground plane with a length and having a vertical axial along the length, and a dipole radiating element projects outwardly from a surface of the ground plane. The radiating element includes a feed section and a ground section. 
     Further features and advantages of the present invention are set out in the following detailed disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a vertical polarized base station antenna on a ground plane, according to an embodiment of the present invention. 
         FIG. 2  shows a staggered dipole antenna arrangement on the ground plane, according to an embodiment of the present invention. 
         FIG. 3A  shows another staggered dipole antenna arrangement on the ground plane, according to an embodiment of the present invention. 
         FIG. 3B  shows the end view of the staggered dipole arrangement of  FIG. 3A , according to an embodiment of the present invention. 
         FIG. 4  shows an isometric view of a dipole antenna on the ground plane, according to an embodiment of the present invention. 
         FIG. 5  shows one of the dipole arm with the microstrip line attached, according to an embodiment of the present invention 
         FIG. 6  shows one of the dipole arm attached to the ground plane, according to an embodiment of the present invention. 
         FIG. 7  shows an isometric view of the dipole antenna without the ground plane, according to an embodiment of the present invention. 
         FIGS. 8A-C  shows top views of alternate dipole arm arrangements, according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides an antenna for use in wireless communication systems which addresses the above noted problems. One embodiment of the present invention operates across various frequency bands, 806-960 MHz band, 380-470 MHz band, 1710-2170 MHz. Although the present invention is particularly adapted for use in a base station, it also can be used in all types of telecommunication systems, such as WiMax 2.3 GHz, 2.5 GHz and 3.5 GHz bands, etc. 
       FIG. 1  shows a set of four example dipole array antennas  10  with a common input  11 , according to the present invention, for transmitting and receiving electromagnetic signals. Each antenna element  10  ( FIG. 7 ) includes two arms  18 ,  20 , a ground plate  12  and two electrical conductors/legs  14  and  16  ( FIGS. 5 and 6 ). The conductor  16  is attached to ground using the plate  12 , with a dipole arm  18  ( FIG. 6 ) towards one side, while the other conductor  14  is spaced to the ground by a dielectric  23  ( FIG. 3B ), such as air, foam, etc., with a dipole arm  20  ( FIG. 5 ) towards the opposite side of dipole arm  20 , therefore forming a dipole configuration. Each dipole arm forms a radiating section/element. In this example, the conductor  14  and dipole arm  20  are formed/stamped from a sheet of conductive material, forming an L-shape. Further, the conductor  16  and dipole arm  18  are formed/stamped from a sheet of conductive material, forming an L-shape. The input conductors  14  and  16  are separated by a gap  22  ( FIGS. 3B ,  8 A-C). 
     The conductor  14  connects a part of the dipole arm  20  to a feed line  24  and the conductor  16  connects a part of the dipole arm  18  to ground via the plate  12 . 
     The conductors  14  and  16  form a paired strips transmission line having an impedance. The arms  18 ,  20  also have an impedance. 
     The impedance of the paired strips transmission line  14 ,  16 , is adjusted by varying the width of conductor sections  14 ,  16  and/or the gap  22  therebetween. The specific dimensions vary with the application. As such, the intrinsic input impedance of each dipole is adjusted to match the impedance of the corresponding feed section. 
     The two conductor sections  14 ,  16  of the dipole antenna form a balanced paired strips transmission line; therefore, it is unnecessary to provide a balun. This provides the antenna  10  with a very wide impedance bandwidth. Also, the antenna  10  has a stable far-field pattern across the impedance bandwidth. 
       FIG. 4  shows an isometric view of a single dipole antenna  10  on the ground plane  28 .  FIG. 5  shows the dipole arm  20  with the microstrip feed line  24  attached and  FIG. 6  shows the dipole arm  18  that can be attached to the ground plane  28  via the plate  12 . The feed line  24  (and its extension feed line  11 ) comprises a microstrip feed line spaced from the ground plane  28  by non-conductor such as air dielectric (e.g., dielectric  23 ). The impedance of the microstrip line is adjusted by varying the width of the element  24 , and/or the space between the microstrip line to the ground plane. The feed line  24  is shown as a unitary element of the conductor  14 .  FIG. 7  shows an isometric view of the dipole antenna  10 , as combination of elements in  FIGS. 5 and 6 . 
     The conductor section  16  can be connected to the ground plane  28  by any suitable fastening device  30  ( FIG. 3B ) such as a nut and bolt, a screw, a rivet, or any suitable fastening method including soldering, welding, etc. The suitable connection provides both an electrical and mechanical connection between the conductor  16  and ground plane  28 . 
     The arrangement of the four dipole antennas  10  in  FIG. 1  provides 90 degree, 105 degree, and 120 degree 3 dB azimuth beam width base station antenna implementations, with different shapes of the ground plane  28 . The staggered dipole arrangement in  FIG. 2  and  FIGS. 3A-B  provide a 65 degree 3 dB azimuth beam width base station antenna implementations. In the staggered arrangement in  FIG. 2  the legs  14 ,  16  of the antennas  10  are essentially perpendicular to the ground plane  28 . 
     In the above implementation, the legs  14 ,  16  of each antenna  10  are at about 90 degree angles in relation to the ground plane  28 . In another implementation, the legs  14 ,  16  of an antenna  10  can be at less than 90 degree angles to the ground plane  28 . For example, the legs  14 ,  16  of an antenna  10  can be between about 90 degrees (perpendicular to the ground plane  28 ) and about 30 degree to the ground plane  28 . Other angles are possible.  FIGS. 3A-B  provide examples of a staggered arrangement with the legs  14 ,  16  of each antenna between about 90 degrees (perpendicular to the ground plane  28 ) and about 30 degree to the ground plane  28 . 
       FIG. 3A  shows a staggered arrangement of four dipole antennas  10 A-D on the ground plane  28 , wherein the legs  14 ,  16  of each the antenna  10 A are transverse in relation to the legs  14 ,  16  of the antenna  10 B. Further, the legs  14 ,  16  of the antenna  10 A are at less than 90 degree angles (e.g., 30 to 90 degrees) in relation to the ground plane  28 . Similarly, the legs  14 ,  16  of the antenna  10 B are at less than 90 degree angles (e.g., 30 to 90 degrees) in relation to the ground plane  28 . As such, in this example the dipole antennas  10 A and  10 B can be at transverse angles of e.g. greater than 0 to about 120 degrees, in relation to one another. Other transverse angles between the antennas  10 A and  10 B are possible. 
     Similarly the legs of the antennas  10 C and  10 D are transverse in relation to one another, and at less than 90 degrees in relation to the ground plane  28 .  FIG. 3B  shows a partial end view of the staggered dipole arrangement of  FIG. 3A , showing antennas  10 A and  10 B. 
     Specific additional variations and implementation details will vary with the particular application as will be appreciated by those skilled in the art. For example,  FIGS. 8A-C  show top views of alternate dipole arm arrangements, according to the present invention. The gap  22  between the legs  14  and  16  in the alternate antennas  40 A-C in  FIGS. 8A-C  is the same, while  FIGS. 8B and 8C  show an enlarged view of the gap  22  for clarity. 
       FIG. 8A  shows a top view of the antenna  40 A wherein the dipole arms  18 ,  20  and the legs  14 ,  16  are symmetric. Further, the legs  14  and  16  are the same distance from the centerline  32 A of the dipole arms  18 ,  20 .  FIG. 8B  shows a top view of the antenna  40 B wherein the dipole arms  18 ,  20  are asymmetric, and the leg  16  lies on the centerline  32 B of the dipole arms  18 ,  20 .  FIG. 8C  shows a top view of the antenna  40 C wherein the dipole arms  18 ,  20  are asymmetric, and the leg  14  lies on the centerline  32 C of the dipole arms  18 ,  20 . 
     Further features and advantages of the invention will be apparent to those skilled in the art. Also, it will be appreciated by those skilled in the art that a variety of modifications of the illustrated implementation are possible while remaining within the scope of the invention.