Abstract:
A radiation device having a L-shaped ground plane. The radiation device comprises a radiation patch; a feeding-in device for exciting the radiation patch; and a L-shaped ground plane. The L-shaped ground plane has a first ground plane and a second ground plane, and the first ground plane is parallel to the radiation patch and an included angle is formed between the fist and the second ground plane. The feeding-in device is used for coupling the energy to the radiation patch, and is connected to the first ground plane of the L-shaped ground plane.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a radiation device, and particularly to a radiation device with a L-shaped ground plane. 
   2. Description of the Prior Art 
   In recent years, the communication industry has advanced vigorously and various communication products have been very successfully developed and manufactured. During this time, much attention has been paid to the design of the antenna of the related communication product. In the various antenna structures, the patch antenna is popular in the market for its characteristics of low profile and lower back radiation. However, the characteristic of the radiation pattern of the prior art patch antenna usually causes a maximum field is generated above the radiation patch in the direction perpendicular to the antenna (that is, θ=0° or having a broadside radiation pattern). And when the angle of |θ| increases, the radiation intensity of electric field will apparently increase. This kind of radiation characteristic for the antenna is unsuitable to the design of the radiation pattern needing omni-directional field above the radiation patch antenna. Although the variation of the filed of the antenna radiation pattern will slow down if the size of the ground plane is reduced, it will cost the gain of the antenna. Thus, the application of the prior art patch antenna is limited for the wireless communication product requiring an antenna with wider receiving/transmitting angle. 
   Please refer to FIG.  1 .  FIG. 1  is a perspective diagram of a prior art shorted microstrip antenna  10  with multiple ground planes. The antenna  10  comprises a radiation patch  11 , a compound ground plane  11   a,  and a feeding-in device  15  for connecting the radiation patch  11  to the multiple ground planes  11   a.  The multiple ground plane  11   a  comprises a first grounding conductive sheet  12  parallel to the radiation patch  11 , a second grounding conductive sheet  13  connected to the radiation patch  11  and the first grounding conductive sheet  12 , and a third grounding conductive sheet  14 . The third grounding conductive sheet  14  is perpendicular to the first grounding conductive sheet  12 , and parallel to the second grounding conductive sheet  13 . 
   The antenna  10  is so designed that the multiple ground planes  11   a  are employed for improving the beam-tilt characteristic caused by the shorted structure so as to promote the antenna gain in the z direction. Although the designed structure of the antenna  10  can improve the distribution of the radiation pattern, the multiple ground planes  11   a  have to be composed of three grounding conductive sheets  12 ,  13 ,  14  and the complexity of the structure design is increased. Besides, the second grounding conductive sheet  13  must be higher than the radiation patch  11 , and the is will affect the appearance of the product and increase the cost. 
   Please refer FIG.  2 .  FIG. 2  is a perspective diagram of a coaxial line feed-in broadband patch antenna  20  having a U-shaped ground plane  22 . The antenna  20  comprises an E-shaped radiation patch  21 , a U-shaped ground plane  22 , a coaxial feed-in line  23  for connecting the E-shaped radiation patch  21  and the U-shaped ground plane  22 . 
   The antenna  20  is so designed that cross polarization of the radiation pattern is reduced so as to increase the purity of the linear polarization of the antenna. However, this designed structure will not apparently improve the gain of the antenna. In addition, as shown in  FIG. 2 , the U-shaped ground plane  22  has to have a planar ground plane  22   a  and two perpendicular ground planes  22   b.  In other words, the plane  22  is composed of three metal pieces so as to increase the complexity of the structure of the antenna  20 . 
   SUMMARY OF THE INVENTION 
   Therefore, the main objective of the present invention is to provide a radiation device with a L-shaped ground plane. The radiation device has a simpler structure, enhanced broadside radiation patterns and the antenna profile is remained to be low. In the proposed antenna design, the radiation intensity of the antenna in the direction of |θ|≦90° can be promoted, and the inventive radiation device is suitable to all kind of planar patch antenna structures, such as shorted patch antennas, dual-frequency planar patch antennas and so on. 
   The present invention relates to a radiation device wth a L-shaped ground plane. The radiation device comprises a radiation patch; a feeding-in device for exciting the radiation patch; and a L-shaped ground plane. The L-shaped ground plane has a first ground plane and a second ground plane. The first ground plane is approximately parallel to the radiation patch, and an included angle will be formed between the first and second ground plane. The feeding-in device will couple the energy to the radiation patch, and is connected to the first ground plane of the L-shaped ground plane. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and form part of the specification in which like numerals designate like parts, illustrate preferred embodiments of the present invention and together with the description, serve to explain the principles of the invention. In the drawings: 
       FIG. 1  is a perspective diagram of a prior art shorted microstrip antenna with multiple ground planes; 
       FIG. 2  is a perspective diagram of a coaxial line feed-in broadband patch antenna  20  with a U-shaped ground plane; 
     FIG.  3 ( a ) is a perspective diagram of a radiation device  30  with a L-shaped ground plane  35  according to a first embodiment of the present invention; 
     FIG.  3 ( b ) is a side view of the radiation device  30  according to the first embodiment; 
     FIG.  4 ( a ) is a perspective diagram of the radiation exciting current of the radiation device on the radiation patch according to the first embodiment; 
     FIG.  4 ( b ) is a perspective diagram of the radiation exciting current of the radiation device on the radiation patch according to the first embodiment; 
       FIG. 5  shows the measured result of the antenna radiation pattern of the radiation device on the x-z plane according to the first embodiment; 
       FIG. 6  is a perspective diagram of a radiation device according to a second embodiment of the present invention; 
       FIG. 7  shows the measured result of the antenna radiation pattern of the radiation device on the x-z plane according to the second embodiment; 
       FIG. 8  is a perspective diagram of a short radiation device with a L-shaped ground plane according to a third embodiment of the present invention; 
       FIG. 9  shows the measured result of the antenna radiation pattern of the radiation device on the x-z plane according to the third embodiment; 
       FIG. 10  is a perspective diagram of a dual-frequency shorted radiation device with a L-shaped ground plane according to a fourth embodiment of the present invention; 
       FIG. 11  shows the measured result of the antenna radiation pattern of the radiation device on the x-z plane when the radiation device is operated in a high frequency according to the fourth embodiment; and 
       FIG. 12  is a perspective diagram of a radiation device according to a fifth embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Please refer to FIGS.  3 ( a ) and  3 ( b ). FIG.  3 ( a ) is a perspective diagram of a radiation device  30  with a L-shaped ground plane  35  according to a first embodiment of the present invention. FIG.  3 ( b ) is a side view of the radiation device  30 . The radiation device  30  comprises a radiation patch  31 , a feeding-in device  32 , and a L-shaped ground plane  35 . The radiation device  30  transmits the energy through the feeding-in device  32 , and excites the radiation patch  31  to generate radiation. The L-shaped ground plane  35  si composed of a first ground plane  33  and a second ground plane  34 . The first ground plane  34  is almost perpendicular to the first ground plane  33 . The radiation metal piece (radiation patch)  31  is fixed on the first ground plane  33  by using a non-conductive post (not shown), and the feeding-in device  32  is used for connecting the radiation patch  31  and the L-shaped ground plane  35 , and for exciting the radiation patch  31  to transmit signals. On the left side of the first ground plane  33  (namely, the x direction), the second ground plane  34 , which is spaced-from and not in contact with the radiation patch  31 , is extended upward from the surface of the first ground plane  33  where the radiation patch  31  is installed so as to form a ground plane structure to form a L-shaped ground plane  35 . 
   As described above, the L-shaped ground plane  35  is composed of two ground metal sheets, namely the first ground plane  33  and the second ground plane  34 . The first ground plane  33  is roughly parallel to the radiation patch  31 , and the second ground plane  34  is connected to the first ground plane  33  in the direction of the exciting current of the radiation patch  31 , and they are not coplanar. Furthermore, the height of the second ground plane  34  is less than the twice distance between the radiation patch  31  and the first ground plane  33 . 
   Based on the above designed structure, the strength of the antenna radiation electric field on the semi-spherical surface (0°≦θ≦90°) corresponding to the second ground plane  34  will increase. When the strength of the radiation electric field of the antenna increases, the output power of the transmitting end of the radio frequency circuit can be reduced, and the sensitivity of the receiving end will be increased. And the angles for the antenna capable of receiving and transmitting can be increased. Besides, the inventive radiation device  30  has a simple structure and a low manufacture cost, and is greatly suitable to be used in the wireless communication product. 
   Please refer to FIGS.  4 ( a ) and  4 ( b ). They are the perspective diagrams of the radiation exciting current of the radiation device  30  on the radiation patch  31 . FIG.  4 ( a ) is a perspective diagram of the radiation exciting current in the signal polarization direction. FIG.  4 ( b ) is a perspective of the radiation exciting current in the dual polarization direction. The second ground plane  34  is connected to the first ground plane  33  in the exciting current direction  41  of the radiation patch. In FIG.  4 ( b ), the exciting current of the radiation patch has two directions  42 ,  43  perpendicular to each other, and the second ground plane  34  can be connected to the first ground plane  33  in the radiation exciting current direction  42  or  43  so as to increase the strength of the radiation electric field of the antenna. 
   Please refer to FIG.  5 .  FIG. 5  shows the measured result of antenna radiation pattern of the radiation device  30  on the x-z plane. The length of the radiation patch  31  is about 29 mm, and the width is about 6 mm. The distance between the radiation patch  31  and the first ground plane  33  is 6 mm, and both of the length and width of the first ground plane  33  are 40 mm. The second ground plane  34  is a ground metal sheet_perpendicularly extended upward from the left side (−x direction) of the first ground plane by 6 mm. 
   In  FIG. 5 , the reference number  51  represents the antenna radiation pattern on the x-z plane when the radiation device  30  does not have the second ground plane  34 . The reference number  52  represents the antenna radiation pattern on the x-z plane when the radiation device  30  has the second ground plane  34 . Based on the measured result of the radiation pattern, it is known that, compared to the radiation device  30  having no second ground plane  34 , the strength of the radiation electric field on the semi-spherical surface (0°≦θ≦90°) of radiation device  30  having the second ground plane  34  in the +x direction increase apparently. 
   Please refer to FIG.  6 .  FIG. 6  is a perspective diagram of a radiation device  60  according to a second embodiment of the present invention. The difference between the radiation device  60  and the radiation device  30  is that the radiation device  60  has a different L-shaped ground plane  61 . In the radiation device  60 , the second ground plane  61  is installed on the right side (+x direction) of the first ground plane  33  and is extended upward by the height of 6 mm from the surface of the first ground plane  33  where the radiation patch is installed. 
   Please refer to FIG.  7 .  FIG. 7  shows the measured result of the of the antenna pattern of the radiation device  60  on the x-z plane. The reference number  71  represents the radiation pattern of the radiation device  60 , and the reference number  51  represents the radiation pattern when the radiation device  60  does not comprises the second ground plane. According to the measured result of the pattern, it can be known that compared to the radiation device  60  having no second ground plane  61 , the strength of the radiation electric field on the semi-spherical surface (0°≧θ≧−90°) of the radiation device  60  having the second ground plane  61  in the −x direction is increased apparently. 
   Based on the measured results in FIG.  5  and  FIG. 7 , it can be known that the strength of the radiation electric field on the semi-spherical surface of the radiation pattern corresponding to the second ground plane will increase when a second ground plane is extended upward in any side of the exciting current direction from the surface of the first ground plane  33  where the radiation patch  31  is installed. In other words, when a second ground plane is extended upward in the −x direction, as shown in the first embodiment, the strength of the radiation electric field in the +x direction will increase. In the contrary, when a second ground plane is extended upward in the +x direction, as shown in the second embodiment, the strength of the radiation electric field in the −x direction will increase. 
   Please refer to FIG.  8 .  FIG. 8  is a perspective diagram of a shorted radiation device  80  with a L-shaped ground plane  86  according to a third embodiment of the present invention. The radiation device  80  comprises a radiation patch  81 , a feeding-in device  82 , a shorted structure  83 , and a L-shaped ground plane  86 . The L-shaped ground plane  86  is composed of a first ground plane  84  and a second ground plane  85 . The shorted structure  83  is used for connecting the radiation patch  81  to the first ground plane  84 , and the feeding-in device  82  is used for exciting the radiation patch  81  to generate the radiation. Besides, on the left side (−x direction) of the first ground plane  84 , the second ground plane  85  is extended upward from the surface of the first ground plane  84  where the radiation patch  81  is installed so as to form the L-shaped ground plane  86 . 
   The length of the radiation patch  81  is about 13 mm, and the width is about 2.5 mm. The distance between the radiation patch  81  and the first ground plane  84  is 5 mm, and the length and width of the first ground plane  84  are both 40 mm. The second ground plane  85  is a ground metal sheet extended upward by 5 mm on the left side (−x direction) of the first ground plane  84 . 
   Please refer to FIG.  9 .  FIG. 9  shows the measured result of the antenna radiation pattern of the radiation device  80  on the x-z plane. The reference number  91  represents the antenna radiation pattern of the radiation device  80  on the x-z plane when it does not have the second ground plane. The reference number  92  represents the antenna radiation pattern of the radiation device  80  on the x-z plane when it has the second ground plane. Based on the measured result of the pattern, it can be known that compared to the radiation device  80  having no second ground plane, the strength of the radiation electric field on the semi-spherical surface (0°≦θ≦90°) of the radiation device  80  having the second ground plane in the +x direction will increase. 
   Please refer to FIG.  10 .  FIG. 10  is a perspective diagram of a dual-frequency radiation device  100  having a L-shaped ground plane  108  according to a fourth embodiment of the present invention. The radiation device  100  comprises a microwave substrate  102 , a feeding-in device  103 , two shorted posts  104 ,  105 , and a L-shaped ground plane  108 . The L-shaped ground plane  108  is composed of a first ground plane  106  and a second ground plane  107 . As shown in the figure, the radiation patch  1011  having a greater area and the radiation patch  1012  having a smaller area are etched on the microwave substrate  102 . 
   In addition, the feeding-in device  103  is used for exciting the smaller radiation patch  1012 , and exciting the greater radiation patch  1011  by a coupling mode. Therefore, the feeding-in device  103  can simultaneously excite off the ISM (Industrial Scientific Medical) bands of 2.4 GHz and 5.2 GHz. Furthermore, the two radiation patch  1011  and  1012  are connected to the first ground plane  106  via the shorted posts  104 ,  105 , and on the left side (−x direction) of the first ground plane  106 , the second ground plane  107  is extended upward from the surface of the first ground plane  106  where the microwave substrate  102  is installed. The ground plane structure composed of the first ground plane  106  and the second ground plane  107  is the L-shaped ground plane  108 . 
   The length of the greater radiation patch  1011  is about 19 mm, and the width is about 10 mm. The length of the smaller radiation patch  1012  is about 12 mm, and the width is about 2.5 mm. The distance between the greater radiation patch  1011  and the first ground plane  106  is 5 mm and the same as the distance between the smaller radiation patch  1012  and the first ground plane  106 . Both of the length and width of the first ground plane  106  are 40 mm. And the second ground plane  107  is a ground metal sheet extended upward by 5 mm on the left side (−x direction) of the first ground plane  106 . 
   Please refer to FIG.  11 .  FIG. 11  shows the measured result of the antenna radiation pattern of the radiation device  100  on the x-z plane when the radiation device  100  is operated in a high frequency according to the fourth embodiment. The reference number  111  represents the antenna radiation pattern on the x-z plane when the radiation device  100  does not have the second ground plane. The reference number  112  represents the antenna radiation pattern on the x-z plane when the radiation device  100  has the second ground plane. Based on the measured result of the radiation pattern, compared to the radiation device  100  having no second ground plane, the strength of the radiation electric field on the semi-spherical surface (0°≦θ≦90°) of the radiation device  100  having the second ground plane in the +x direction will apparently increase. 
   Please refer to FIG.  12 .  FIG. 12  is a perspective diagram of a radiation device according to a fifth embodiment of the present invention. The radiation device  120  comprises a radiation patch  121 , a feeding-in device  122 , and a L-shaped ground plane  125 . The L-shaped ground plane  125  is composed of a first ground plane  123  and a second ground plane  124 . Compared with the other embodiments, the characteristic of the radiation device  120  is that the radiation patch  121  is a circular patch. 
   Compared with the prior art, the radiation device according to the present invention has the L-shaped ground plane, and therefore, the strength of the antenna radiation electric field on the semi-spherical surface (|θ|≦90°) corresponding to the second ground plane will increase so as to promote the gain of the antenna on the semi-spherical surface of |θ|≦90°. Thus, the power output of the transmitting end of the radio frequency circuit will be reduced, and the sensitivity of the receiving end will be increased. In addition, the angles for the antenna capable of receiving and transmitting can be increased, and the inventive radiation device has a low manufacture cost, and is greatly suitable to be used in the wireless communication product. 
   Furthermore, the radiation device according to the present invention has a simple structure and the height of the antenna will not be affected. Besides, the radiation gain of the antenna radiation pattern in the direction of |θ|≦90° can be promoted. Therefore, the inventive radiation device is greatly suitable to be used in all kinds of the planar patch antenna structures, such as the shorted patch antennas, the dual-frequency patch antennas and so on. 
   Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.