Patent Publication Number: US-2010123629-A1

Title: Dual-Polarized Antenna

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an antenna, and more particularly to a dual-polarized antenna. 
     2. The Related Art 
     In recent years, portable communication devices are becoming progressively popular. In order to communicate with the outside world, various antennas are assembled in these devices for transmitting and receiving electromagnetic waves. Dual-polarized antenna is just a category among the varied antennas. A known dual-polarized antenna adopts two pairs of half-wave oscillators symmetrically arranged in a substantially cross-shaped structure to realize orthogonal magnetic field between the two pairs of the half-wave oscillators and achieve double polarization. 
     However, the above known dual-polarized antenna is by means of two couples of half-wave oscillators to perform communication function, the structure of the dual-polarized antenna is simple, but the gain of the dual-polarized antenna is also correspondingly reduced, which affects the efficiency of the dual-polarized antenna. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a dual-polarized antenna having an improved gain. The dual-polarized antenna includes a grounding plate, a vertically polarized portion and a horizontally polarized portion. The vertically polarized portion has a first connecting portion extending from one edge of the grounding plate, a vertical radiating element spaced at the edge for forming a simulation capacitance therebetween, and a first feeding portion connected to the first connecting portion and the vertical radiating element. The horizontally polarized portion has a second connecting portion extending from another edge of the grounding plate substantially perpendicular to the edge of the grounding plate, a horizontal radiating element spaced at the another edge for forming a simulation capacitance therebetween, and a second feeding portion connected to the second connecting portion and the horizontal radiating element. 
     As described above, a simulation capacitance is respectively formed between the vertical radiating element and the grounding plate, and the horizontal radiating element and the grounding plate, which can adjust bandwidth and input impedance of the dual-polarized antenna for improving the gain of the dual-polarized antenna. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be apparent to those skilled in the art by reading the following description of an embodiment thereof, with reference to the attached drawings, in which: 
         FIG. 1  is a perspective view of a dual-polarized antenna in accordance with the present invention; 
         FIG. 2  is a partial enlarged view of a first feeding portion of the dual-polarized antenna labeled IX shown in  FIG. 1 ; and 
         FIG. 3  is a vertical view of the dual-polarized antenna shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to  FIGS. 1 to 3 , a dual-polarized antenna  100  according to the invention includes a grounding plate  10 , a vertical radiating element  40  spaced at one edge of the grounding plate  10  and a horizontal radiating element  70  spaced at another edge of the grounding plate  10  substantially perpendicular to the edge of the grounding plate  10 . 
     The grounding plate  10  includes a first grounding plate  11 , a second grounding plate  13  spaced at the first grounding plate  11  and a narrow linking portion  12  connecting the first grounding plate  11  with the second grounding plate  13 . 
     The first grounding plate  11  is of substantially rectangular shape and has two opposite first and second longitudinal edges  11   a,    11   c,  and two opposite top and bottom transverse edges  11   b,    11   d  substantially perpendicularly connected to the first and second longitudinal edges  11   a  and  11   c.  The first grounding plate  11  has a first grounding point  111  positioned at a corner formed by the first longitudinal edge  11   a  and the bottom transverse edge  11   d.  A first connecting portion  20  extends outward and inclines towards the bottom transverse edge  11   d  from a lower position of the first longitudinal edge  11   a  which is near the first grounding point  111 . 
     The vertical radiating element  40  has a substantially rectangular shaped vertical radiating section  41  spaced at the first longitudinal edge  11   a  of the first grounding plate  11 . A top end of the vertical radiating section  41  has a cambered radiating section  42  bent towards the first longitudinal edge  11   a.  A bottom end of the vertical radiating section  41  exceeds the bottom transverse edge  11   d  of the first grounding plate  11 . 
     A first feeding portion  30  arranged between the vertical radiating element  40  and the first connecting portion  20  for connecting the vertical radiating element  40  with the first connecting portion  20 . The first feeding portion  30  has a base  31  extending towards the vertical radiating section  41  from a free end of the first connecting portion  20  and a raised junction  32  connecting a long edge of the vertical radiating section  41  and a free end of the base  31 . The base  31  defines a first feeding point  311  adjacent to the first grounding point  111 . A bottom edge of base  31  is substantially at the same level with the bottom transverse edge  11   d  of the first grounding plate  11 . The raised junction  32  defines a drop height between the vertical radiating element  40  and the first grounding plate  11 . 
     The second grounding plate  13  is of substantially rectangular shape and has two opposite third and fourth longitudinal edges  13   a,    13   c,  and two opposite upper and lower transverse edges  13   b,    13   d  substantially perpendicularly connected to the third and fourth longitudinal edges  13   a  and  13   c.  The linking portion  12  connects a portion of the second longitudinal edge  11   c  of the first grounding plate  11  with a portion of the third longitudinal edge  13   a  of the second grounding plate  13  which is spaced parallel to the second longitudinal edge  11   c.  The second grounding plate  13  has two projecting pieces  131  respectively protruding upward from the upper transverse edge  13   b  and downward from the lower transverse edge  13   d  until a bottom edge thereof aligned with the bottom transverse edge  11   d  of the first grounding plate  11 . The two projecting pieces  131  are adjacent to the third longitudinal edge  13   a.  The junction of the upper transverse edge  13   b  and the fourth longitudinal edge  13   c  is cut off to form an arc trace  132 . A second grounding point  133  is disposed at a portion of the second grounding plate  13  adjacent to the upper transverse edge  13   b.    
     The horizontal radiating element  70  is spaced at the upper transverse edge  13   b  of the second grounding plate  13  with a top edge of the horizontal radiating element  70  substantially at the same level with the top transverse edge  11   b  of the first grounding plate  11 . A second connecting portion  50  extends slantwise from a portion of the upper transverse edge  13   b  and towards the fourth longitudinal edge  13   c.  A second feeding portion  60  extends towards the upper transverse edge  13   b  of the second grounding plate  13  from a bottom edge of the horizontal radiating element  70  and terminates to a free end of the second connecting portion  50  for connecting the horizontal radiating element  70  with the second connecting portion  50 . The second feeding portion  60  defines a second feeding point  61  adjacent to the second grounding point  133 . 
     Structures of the cambered radiating section  42 , the raised junction  32  and the arc trace  132  described above are shaped for adapting the dual-polarized antenna  100  to the interior space of an electronic product and installing the dual-polarized antenna  100  to the electronic product easily. Furthermore, the raised junction  32  can prevent the vertical radiating element  40  from rising up when assembled it to the electronic product. 
     The vertical radiating section  41  and the first grounding plate  11  are parallel to each other to form a simulation capacitance therebetween. The horizontal radiating element  70  and the second grounding plate  13  are parallel with each other to form a simulation capacitance therebetween. Both of the two simulation capacitances can tune the bandwidth and input the impedance of the dual-polarized antenna  100  to realize the impedance matching between the dual-polarized antenna  100  and the feeding cables (not shown) for decreasing the backwash effect and boosting the gain of the dual-polarized antenna  100 . 
     The first connecting portion  20 , the first feeding portion  30  and the vertical radiating element  40  corporately form a vertically polarized portion. The antenna characteristics of the vertically polarized portion and the grounding plate  10  are similar to a planar inverted-F antenna resonating at a frequency band of about 2.4 GHz. The second connecting portion  50 , the second feeding portion  60  and the horizontal radiating element  70  collectively compose a horizontally polarized portion. The antenna characteristics of the horizontally polarized portion and the grounding plate  10  are similar to another planner inverted-F antenna also resonating at a frequency band of about 2.4 GHz. Both of the lengths of the horizontally and the vertically polarized portions are substantially equal to a quarter of wavelength with respect to the frequency band of about 2.4 GHz. 
     The linking portion  12  connects up the first grounding plate  11  and the second grounding plate  13 , which not only avoids a reduced efficiency of the horizontally and the vertically polarized portions caused by a complete detachment between the first grounding plate  11  and the second grounding plate  13 , but also helps to decrease a interference between the horizontally polarized portion and the vertically polarized portion on account of a utter connection between the first grounding plate  11  and the second grounding plate  13 . 
     When the dual-polarized antenna  100  is used for wireless communications, the horizontally polarized portion resonates at a frequency range covering 2.4-2.5 GHz to correspond to horizontally polarized electromagnetic waves of the Wireless Fidelity (WIFI), the vertically polarized portion operates at a frequency range covering 2.4-2.5 GHz to correspond to vertically polarized electromagnetic waves of the WIFI. The horizontally polarized portion and the vertically polarized portion are complementary to each other, which helps to improve the gain of the dual-polarized antenna  100 . 
     As described above, the first connecting portion  20 , the first feeding portion  30  and the vertical radiating element  40  corporately form the vertically polarized portion. The second connecting portion  50 , the second feeding portion  60  and the horizontal radiating element  70  together constitute the horizontally polarized portion. The horizontally polarized portion and the grounding plate  10 , the vertically polarized portion and the grounding plate  10  respectively form a planar inverted-F antenna resonating at a frequency range covering 2.4-2.5 GHz, so that the dual-polarized antenna  100  can receive and transmit the electromagnetic waves of the WIFI. The two simulation capacitances, one of which formed between the vertical radiating section  41  and the first grounding plate  11  and the other one formed between the horizontal radiating element  70  and the second grounding plate  13 , can adjust bandwidth of the dual-polarized antenna  100  and better the gain of the dual-polarized antenna  100 , so as to improve the property and the efficiency of the dual-polarized antenna  100 . 
     The foregoing description of the present invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. Such modifications and variations that may be apparent to those skilled in the art are intended to be included within the scope of this invention as defined by the accompanying claims.