Abstract:
A bi-frequency symmetrical patch antenna includes two bi-frequency symmetrical radiation units, each having a first band radiation section and two second band radiation sections, to radiate a feed-in signal in a selected direction. Further, the antenna has a power distribution unit, to evenly distribute the feed-in power, corresponding to the feed-in signal, to each bi-frequency symmetrical radiation unit. The power distribution unit has two side arms connecting respectively to each bi-frequency symmetrical radiation unit to increase the bandwidth range of the bi-frequency antenna.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a patch antenna and particularly to a bi-frequency symmetrical patch antenna.  
       BACKGROUND OF THE INVENTION  
       [0002]     With continuous developments of wireless communication technology, nowadays users can transmit information through wireless communication systems without geometric restrictions. An antenna is one of the important elements in wireless communication. At present the antenna made from a printed circuit board is most popular. It is easier to fabricate and costs less.  
         [0003]     The commonly used wireless communication standards now are IEEE802.11 a and IEEE802.11b announced by the Electrical and Electronic Engineering Institute (IEEE). IEEE802.11a is for the band of 5 GHz. IEEE802.11b is for the band of 2.4 GHz. Design of the antenna baseboard has to comply with the corresponding bandwidth. If a wireless communication system has to be used in two different bands at the same time, matching antennas have to be provided. This causes inconvenience. To meet the requirement of different bands, adopting a bi-frequency antenna design is a growing trend. However, the present bi-frequency antenna still has drawbacks, such as an insufficient bandwidth and integration difficulties.  
         [0004]     Hence how to provide a broadband bi-frequency antenna is one of the research and development focuses in the industry.  
       SUMMARY OF THE INVENTION  
       [0005]     In view of the aforesaid problems, the primary object of the present invention is to provide a bi-frequency symmetrical patch antenna that has bi-frequency symmetrical radiation units to radiate feed-in signals and increase the bandwidth range of a bi-frequency antenna. The bi-frequency symmetrical radiation units are arranged in an array fashion to enhance the directionality of the bi-frequency antenna.  
         [0006]     In order to achieve the foregoing object, the bi-frequency symmetrical patch antenna according to the invention has a first surface and a second surface to receive a feed-in signal and radiate the feed-in signal in a selected direction. It includes two bi-frequency radiation units and a power distribution unit.  
         [0007]     Each of the two bi-frequency symmetrical radiation units has a first band radiation section and two second band radiation sections to radiate the feed-in signal. The first band radiation section has a length greater than the length of each second band radiation section.  
         [0008]     The power distribution unit aims to evenly distribute feed-in power corresponding to the feed-in signal to each bi-frequency symmetrical radiation unit. The power distribution unit is substantially formed in a T-shape. It is connected to the first band radiation section and the two second band radiation sections through a first micro strip, a second micro strip and a third micro strip.  
         [0009]     In another aspect, the invention provides an array type bi-frequency symmetrical patch antenna, which has a first surface and a second surface to receive a feed-in signal and radiate the feed-in signal in a selected direction. It includes one or more bi-frequency radiation units and one or more power distribution units.  
         [0010]     Each bi-frequency symmetrical radiation unit has a first band radiation section and two second band radiation sections to radiate the feed-in signal. The first band radiation section has a length greater than the length of each second band radiation section.  
         [0011]     The power distribution unit aims to evenly distribute feed-in power, corresponding to the feed-in signal, to each bi-frequency symmetrical radiation unit. The power distribution unit has two side arms connecting respectively to a distal end of a next power distribution unit, and the next power distribution unit has two other side arms connecting respectively to each bi-frequency symmetrical radiation unit. The power distribution unit is substantially formed in a T-shape.  
         [0012]     By means of the bi-frequency symmetrical patch antenna of the invention, the bi-frequency symmetrical radiation unit can receive a feed-in signal to increase the bandwidth range of the bi-frequency antenna. The power distribution unit can evenly distribute the feed-in power, corresponding to the feed-in signal, to each bi-frequency symmetrical radiation unit. The bi-frequency symmetrical radiation unit may be arranged in an array fashion to enhance the directionality of the bi-frequency antenna.  
         [0013]     The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is a schematic view of the bi-frequency symmetrical patch antenna of the invention.  
         [0015]      FIG. 2A  is a schematic front view of the first surface of a first embodiment of the invention.  
         [0016]      FIG. 2B  is a schematic front view of the second surface of the first embodiment of the invention.  
         [0017]      FIG. 3  is a schematic view of the antenna baseboard of a second embodiment of the invention.  
         [0018]      FIGS. 4A through 4C  are charts showing the V-polarization radiation pattern of a first band according to the invention.  
         [0019]      FIGS. 4D through 4F  are charts showing the H-polarization radiation pattern of the first band according to the invention.  
         [0020]      FIGS. 5A through 5D  are charts showing the V-polarization radiation pattern of a second band according to the invention.  
         [0021]      FIGS. 5E through 5H  are charts showing the H-polarization radiation pattern of the second band according to the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]     Refer to  FIG. 1  for a schematic view of the bi-frequency symmetrical patch antenna of the invention. The antenna includes an antenna baseboard  10 , which has an antenna pattern formed thereon. The antenna baseboard  10  is made from glass fibers or the like. The antenna baseboard  10  has a first surface and a second surface that are respectively a circuit layer and a ground layer. The antenna pattern on the first surface and the second surface are symmetrical.  
         [0023]     Refer to  FIG. 2A  for the front view of the first surface of a first embodiment of the invention. The first surface  101  has a micro strip circuit pattern of the circuit layer. In the center of the antenna baseboard  10 , there is a power distribution unit  120 . A radio signal feeds in through a distal end  120   a  of the power distribution unit  120 . There are bi-frequency symmetrical radiation units  110 , connecting respectively to two side arms  120   b  and  120   c,  to form a completed antenna pattern. The power distribution unit  120  evenly distributes feed-in power corresponding to the feed-in signal to each of the bi-frequency symmetrical radiation units  110 .  
         [0024]     The bi-frequency symmetrical radiation units  110  have a first band radiation section  110   a  and second band radiation sections  110   b  and  110   c.  The first band (such as 2.4 GHz) radiation section  110   a  is located on one side of a distal end of a first micro strip  20  and vertically connected to one side of the distal end of the first micro strip wire  20 . One second band (such as 5 GHz) radiation section  110   b  is located on a distal end of a second micro strip  21  and vertically connected to one side of the distal end of the second micro strip  21 . The second micro strip  21  is formed in a zigzag path and substantially in a U-shape.  
         [0025]     Another second band (such as 5 GHz) radiation section  110   c  is located on a distal end of a third micro strip  22  and is vertically connected to one side of the distal end of the third micro strip  22 . The third micro strip  22  is formed in a zigzag path and substantially in a U-shape, and is symmetrical to the second micro strip  21 .  
         [0026]     In addition, the first band radiation section  110   a  is extended in a direction opposite to the second band radiation sections  110   b  and  110   c.  Namely, if the first band radiation section  110   a  is extended to one side of the antenna baseboard  10 , the second band radiation sections  110   b  and  110   c  are extended to another side of the antenna baseboard  10  (based on the distal end of each micro strip).  
         [0027]     The power distribution unit  120  evenly distributes the feed-in power corresponding to the feed-in signal through the first micro strip  20 , second micro strip  21  and third micro strip  22 , that are connected to the first band radiation section  110   a  and second radiation sections  110   b  and  110   c  of each bi-frequency symmetrical radiation unit  110 . The power distribution unit  120  is substantially formed in a T-shape.  
         [0028]     Refer to  FIG. 2B  for the front view of the second surface of the first embodiment of the invention. The second surface  102  has a micro strip circuit pattern of the ground layer. In the center of the antenna baseboard  10 , there is a power distribution unit  140 . There are bi-frequency symmetrical radiation units  130  connecting respectively to two side arms of the power distribution unit  140  to form a completed antenna pattern. The power distribution unit  140  evenly distributes the feed-in power corresponding to the feed-in signal to each of the bi-frequency symmetrical radiation units  130 . The second surface  102  has a micro strip circuit pattern of the ground layer that is symmetrical to the micro strip circuit pattern of the circuit layer on the first surface  101 . Namely, the first band radiation section  110   a,  and the second band radiation sections  110   b  and  110   c  are extended in the directions opposite to that of the first band radiation section  130   a,  and the second band radiation sections  130   b  and  130   c  and the antenna patterns are symmetrical.  
         [0029]     Refer to  FIG. 3  for a schematic view of the antenna baseboard of a second embodiment of the invention. The bi-frequency symmetrical radiation units are arranged in an array fashion through the power distribution units and connected to one another. The schematic view includes a first bi-frequency symmetrical radiation unit  111 , a second bi-frequency symmetrical radiation unit  112 , a third bi-frequency symmetrical radiation unit  113 , a fourth bi-frequency symmetrical radiation unit  114 , a first power distribution unit  121 , a second power distribution unit  122 , a third power distribution unit  123 , a fourth power distribution unit  124 , a fifth power distribution unit  125 , a sixth power distribution unit  126 , and a seventh power distribution unit  127 .  
         [0030]     The first bi-frequency symmetrical radiation unit  111 , second bi-frequency symmetrical radiation unit  112 , third bi-frequency symmetrical radiation unit  113 , and fourth bi-frequency symmetrical radiation unit  114  are formed in an antenna pattern same as that shown in  FIGS. 2A and 2B , thus details are omitted.  
         [0031]     The first power distribution unit  121  has two side arms  121   b  and  121   c  connecting respectively to a distal end  122   a  of the second power distribution unit  122  and a distal end  123   a  of the third power distribution unit  123  to perform a first time power distribution. The second power distribution unit  122  has two side arms  122   b  and  122   c  connecting respectively to a distal end  124   a  of the fourth power distribution unit  124  and a distal end  125   a  of the fifth power distribution unit  125 ; the third power distribution unit  123  has two side arms  123   b  and  123   c  connecting respectively to a distal end  126   a  of the sixth power distribution unit  126  and a distal end  127   a  of the seventh power distribution unit  127 , to perform respectively a second time power distribution.  
         [0032]     Next, the fourth power distribution unit  124  has two side arms  124   b  and  124   c  connecting respectively to the first bi-frequency symmetrical radiation unit  111 , the fifth power distribution unit  125  has two side arms  125   b  and  125   c  connecting respectively to the second bi-frequency symmetrical radiation unit  112 , the sixth power distribution unit  126  has two side arms  126   b  and  126   c  connecting respectively to the third bi-frequency symmetrical radiation unit  113 , and the seventh power distribution unit  127  has two side arms  127   b  and  127   c  connecting respectively to the fourth bi-frequency symmetrical radiation unit  114  to perform respectively a third time power distribution. Therefore, by evenly distributing the feed-in power corresponding to the feed-in signal of the first bi-frequency symmetrical radiation unit  111 , second bi-frequency symmetrical radiation unit  112 , third bi-frequency symmetrical radiation unit  113 , and fourth bi-frequency symmetrical radiation unit  114 , and arranging the first bi-frequency symmetrical radiation unit  111 , second bi-frequency symmetrical radiation unit  112 , third bi-frequency symmetrical radiation unit  113 , and fourth bi-frequency symmetrical radiation unit  114  in an array fashion, the directionality of the antenna can be improved, and the directional gain is enhanced.  
         [0033]     Practical tests of the embodiments of the invention have been conducted based on first band frequencies of 2.4 GHz, 2.45 GHz and 2.5 GHz, and second band frequencies of 4.9 GHz, 5.25 GHz, 5.6 GHz and 5.875 GHz. Refer to  FIGS. 4A through 4C  for the V-polarization radiation pattern of the first band,  FIGS. 4D through 4F  for the H-polarization radiation pattern of the first band,  FIGS. 5A through 5D  for the V-polarization radiation pattern of the second band, and  FIGS. 5E through 5H  for the H-polarization radiation pattern of the second band.  
         [0034]     By means of the bi-frequency symmetrical patch antenna previously discussed, through symmetrical arrangement of the radiation units and power distribution units, the bandwidth of the bi-frequency antenna can be increased, and the feed-in power can be evenly distributed to each bi-frequency symmetrical radiation unit. By arranging the bi-frequency symmetrical radiation units in an array fashion, the directionality of the bi-frequency antenna is enhanced.  
         [0035]     While the preferred embodiments of the invention have been set forth for the purpose of disclosure, modifications of the disclosed embodiments of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments, which do not depart from the spirit and scope of the invention.