Abstract:
A planar dual polarization antenna for receiving and transmitting radio signals includes an upper patch plate and a metal grounding plate with a width along a first direction and a length along a second direction. A shape of the upper patch plate has a first symmetry axis along the first direction and a second symmetry axis along the second direction. The first symmetry axis divides the upper patch plate into a first section and a third section. The second symmetry axis divides the upper patch plate into a second section and a fourth section. A first geometry center of the first section and the symmetry center are separated by a first distance, and a second geometry center of the second section and the symmetry center are separated by a second distance unequal to the first distance.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a planar dual polarization antenna and a complex antenna, and more particularly, to a planar dual polarization antenna and a complex antenna of broadband, wide beamwidth, high antenna gain, better common polarization to cross polarization (Co/Cx) value, smaller size, and meeting 45-degree slant polarization requirements. 
         [0003]    2. Description of the Prior Art 
         [0004]    Electronic products with wireless communication functionalities, e.g. notebook computers, personal digital assistants, etc., utilize antennas to emit and receive radio waves, to transmit or exchange radio signals, so as to access a wireless communication network. Therefore, to facilitate a user&#39;s access to the wireless communication network, an ideal antenna should maximize its bandwidth within a permitted range, while minimizing physical dimensions to accommodate the trend for smaller-sized electronic products. Additionally, with the advance of wireless communication technology, electronic products may be configured with an increasing number of antennas. For example, a long term evolution (LTE) wireless communication system and a wireless local area network standard IEEE 802.11n both support multi-input multi-output (MIMO) communication technology, i.e. an electronic product is capable of concurrently receiving/transmitting wireless signals via multiple (or multiple sets of) antennas, to vastly increase system throughput and transmission distance without increasing system bandwidth or total transmission power expenditure, thereby effectively enhancing spectral efficiency and transmission rate for the wireless communication system, as well as improving communication quality. Moreover, MIMO communication systems can employ techniques such as spatial multiplexing, beam forming, spatial diversity, pre-coding, etc. to further reduce signal interference and to increase channel capacity. 
         [0005]    The LTE wireless communication system includes 44 bands which cover from 698 MHz to 3800 MHz. Due to the bands being separated and disordered, a mobile system operator may use multiple bands simultaneously in the same country or area. Under such a situation, conventional dual polarization antennas may not be able to cover all the bands, such that transceivers of the LTE wireless communication system cannot receive and transmit wireless signals of multiple bands. Therefore, it is a common goal in the industry to design antennas that suit both transmission demands, as well as dimension and functionality requirements. 
       SUMMARY OF THE INVENTION 
       [0006]    Therefore, the present invention provides a planar dual polarization antenna to effectively increase antenna beamwidth. 
         [0007]    An embodiment of the present invention discloses a planar dual polarization antenna for receiving and transmitting radio signals, comprising a metal grounding plate having a width along a first direction and a length along a second direction; and an upper patch plate, wherein a shape of the upper patch plate has a first symmetry axis along the first direction and a second symmetry axis along the second direction, the first symmetry axis divides the upper patch plate into a first section and a third section, and the second symmetry axis divides the upper patch plate into a second section and a fourth section; wherein a symmetry center of the shape is aligned to a center point of the metal grounding plate, a first geometry center of the first section and the symmetry center are separated by a first distance, and a second geometry center of the second section and the symmetry center are separated by a second distance unequal to the first distance. 
         [0008]    An embodiment of the present invention further discloses a complex antenna for receiving and transmitting radio signals, comprising a metal grounding plate comprising a plurality of rectangular regions, each of the plurality of rectangular regions has a width along a first direction and a length along a second direction; and an upper planar dual polarization antenna layer comprising a plurality of upper patch plates disposed corresponding to the plurality of rectangular regions respectively, wherein a shape of each of the plurality of the upper patch plates has a first symmetry axis along the first direction and a second symmetry axis along the second direction, the first symmetry axis divides the upper patch plate into a first section and a third section, and the second symmetry axis divides the upper patch plate into a second section and a fourth section; wherein a symmetry center of the shape is aligned to a center point of the corresponding rectangular region, a first geometry center of the first section and the symmetry center are separated by a first distance, and a second geometry center of the second section and the symmetry center are separated by a second distance unequal to the first distance. 
         [0009]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1A  is a top-view schematic diagram illustrating a planar dual polarization antenna according to an embodiment of the present invention. 
           [0011]      FIG. 1B  is a cross-sectional view diagram of the planar dual polarization antenna taken along a cross-sectional line A-A′ in  FIG. 1A . 
           [0012]      FIG. 2A  is a schematic diagram illustrating a cross quadrate pattern according to an embodiment of the present invention. 
           [0013]      FIGS. 2B and 2C  are schematic diagrams illustrating comparison between the cross quadrate pattern shown in  FIG. 2A  and another cross quadrate pattern. 
           [0014]      FIG. 3  is a top-view schematic diagram illustrating a planar dual polarization antenna according to an embodiment of the present invention. 
           [0015]      FIG. 4  is a top-view schematic diagram illustrating a planar dual polarization antenna according to an embodiment of the present invention. 
           [0016]      FIG. 5  is a top-view schematic diagram illustrating a planar dual polarization antenna according to an embodiment of the present invention. 
           [0017]      FIG. 6  is a top-view schematic diagram illustrating a complex antenna according to an embodiment of the present invention. 
           [0018]      FIG. 7  is a top-view schematic diagram illustrating a complex antenna according to an embodiment of the present invention. 
           [0019]      FIG. 8A  is a schematic diagram illustrating antenna resonance simulation results of the complex antenna shown in  FIG. 7  corresponding to size 5. 
           [0020]      FIGS. 8B to 8E  are schematic diagrams illustrating antenna pattern characteristic simulation results of the complex antenna shown in  FIG. 7  corresponding to size 5 operated at 2.3 GHz, 2.4 GHz, 2.496 GHz and 2.69 GHz respectively. 
           [0021]      FIG. 9A  is a schematic diagram illustrating antenna resonance simulation results of the complex antenna shown in  FIG. 7  corresponding to size 13. 
           [0022]      FIGS. 9B to 9E  are schematic diagrams illustrating antenna pattern characteristic simulation results of the complex antenna shown in  FIG. 7  corresponding to size 13 operated at 2.3 GHz, 2.4 GHz, 2.496 GHz and 2.69 GHz respectively. 
           [0023]      FIG. 10A  is a schematic diagram illustrating antenna resonance simulation results of the complex antenna shown in  FIG. 7  corresponding to size 15. 
           [0024]      FIGS. 10B to 10E  are schematic diagrams illustrating antenna pattern characteristic simulation results of the complex antenna shown in  FIG. 7  corresponding to size 15 operated at 2.3 GHz, 2.4 GHz, 2.496 GHz and 2.69 GHz respectively. 
           [0025]      FIG. 11  is a top-view schematic diagram illustrating a complex antenna according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]      FIG. 1A  is a top-view schematic diagram illustrating a planar dual polarization antenna  10  according to an embodiment of the present invention.  FIG. 1B  is a cross-sectional view diagram of the planar dual polarization antenna  10  taken along a cross-sectional line A-A′ in  FIG. 1A . The planar dual polarization antenna  10  is utilized to receive and transmit radio signals of a broad band or different frequency bands, such as radio signals in Band  40  and Band  41  of an LTE wireless communication system (Band  40 : substantially 2.3 GHz-2.4 GHz, Band  41 : substantially 2.496 GHz-2.690 GHz). As shown in  FIGS. 1A and 1B , the planar dual polarization antenna  10  is substantially a seven-layered square architecture of reflection symmetry with respect to symmetry axes axis_x and axis_y along directions x and y, respectively. The planar dual polarization antenna  10  comprises a feeding transmission line layer  100 , dielectric layers  110 ,  130 ,  150 , a metal grounding plate  120 , a lower patch plate  140  and an upper patch plate  160 . A symmetry center point SCEN of the lower patch plate  140  and the upper patch plate  160  are aligned to a center point CEN of the metal grounding plate  120 . The feeding transmission line layer  100  comprises feeding transmission lines  102   a  and  102   b  which are symmetric with respect to a symmetry axis axis_y and orthogonal to feed in radio signals of two polarizations. The metal grounding plate  120  is used for providing a ground and comprises slots  122   a  and  122   b , which are orthogonal to the feeding transmission lines  102   a  and  102   b , respectively. The slots  122   a  and  122   b  are symmetry to the symmetry axis axis_y so as to generate an orthogonal dual-polarized antenna pattern. The lower patch plate  140  is the main radiating body and has a shape substantially conforming to a cross pattern in order to generate electromagnetic waves with linear polarization but not circular polarization. The upper patch plate  160  is utilized to increase resonance bandwidth of the planar dual polarization antenna  10 , and is electrically isolated from the lower patch plate  140  by the dielectric layer  150 . Besides, since the feeding transmission line layer  100 , the metal grounding plate  120  and the lower patch plate  140  are isolated by the dielectric layers  110  and  130  and parallel to one another, the feeding transmission line layer  100  is coupled to the lower patch plate  140  by means of the slots of the metal grounding plate  120 —that is to say, radio signals from the feeding transmission lines (e.g., the feeding transmission line  102   a ) are coupled to the slots (e.g., the slot  122   a ), and then coupled to the lower patch plate  140  when the slots (i.e., the slot  122   a ) resonates—to increase antenna bandwidth. The resonance direction of the lower patch plate  140  with the shape substantially conforming to a cross pattern tilts with respect to the metal grounding plate  120 , and this effectively minimizes the size of the planar dual polarization antenna  10  while meeting 45-degree slant polarization requirements. 
         [0027]    Briefly, a length L 1  of the metal grounding plate  120  along the symmetry axis axis_y is longer than a width W 1  of the metal grounding plate  120  along the direction x, thereby increasing 3 dB beamwidth in the horizontal plane. The upper patch plate  160  is spread out to be more distributed along the direction x in order to balance the asymmetry/inequivalence of the length L 1  and the width W 1  and thus improve common polarization to cross polarization (Co/Cx) value. 
         [0028]    Specifically, to increase the beamwidth in horizontal plane (i.e., the xz plane), the width W 1  of the metal grounding plate  120  along the direction x must be shortened to make the antenna pattern in horizontal plane diverge. It turns out that the length L 1  of the metal grounding plate  120  along the symmetry axis axis_y is longer than the width W 1  of the metal grounding plate  120  along the direction x. Since the length L 1  is not equal to the width W 1 , equivalent resonance lengths in the vertical direction and in the horizontal direction will differ. The shape of the upper patch plate  160 , however, could balance the asymmetry due to the uneven quantities between the length L 1  and the width W 1 . It is because the upper patch plate  160  has the shape substantially conforming to a cross pattern, and a cross pattern comprises structures such as a cross quadrate pattern according to common knowledge such as from Wikipedia, for example. Please refer to  FIGS. 2A to 2C .  FIG. 2A  is a schematic diagram illustrating a cross quadrate pattern  20  according to an embodiment of the present invention.  FIGS. 2B and 2C  are schematic diagrams illustrating comparison between the cross quadrate pattern  20  shown in  FIG. 2A  and another cross quadrate pattern  21 . Both the cross quadrate patterns  20  and  21  have shapes substantially conforming to cross patterns. Particularly, across section  162  and a quadrilateral section  164  overlapping constitute the cross quadrate pattern  20  with a maximum width Wmax and a maximum length Lmax along the directions x and y respectively, while a cross section and a square section overlapping constitute the cross quadrate pattern  21  with maximum dimensions along the directions x and y equal to a reference dimension D corresponding to the resonance bandwidth, such that the dimensions of the cross quadrate pattern  21  are related to antenna operation frequency. Compared to the cross quadrate pattern  21 , the cross quadrate pattern  20  extends along the direction x (meaning that the area of the cross quadrate pattern  20  is spread out to be more distributed toward the direction x) to satisfy the equation 
         [0000]    
       
         
           
             
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         [0000]    where ratio values Ax and Ay respectively denote the extent to which the dimensions of the cross quadrate pattern  20  are adjusted with respect to the reference dimension D according to the asymmetry of the metal grounding plate  120 . Therefore, the dimensions of the cross quadrate pattern  20  are related to antenna operation frequency and can be adjusted according to the inequivalence of the length L 1  and the width W 1 . It is worth noting that the ratio values Ax and Ay can be close to or even equal to 1 so as to prevent resonance frequency from shifting to change the resonance bandwidth as the cross quadrate pattern  20  is reshaped. 
         [0029]    As shown in  FIG. 2B , the symmetry axis axis_x of the cross quadrate pattern  20  divides the cross quadrate pattern  20  into a section SEC_U with a geometry center G_U 2  and a section SEC_D. Similarly, the symmetry axis axis_y of the cross quadrate pattern  20  divides the cross quadrate pattern  20  into a section SEC_R with a geometry center G_R 2  and a section SEC_L as shown in  FIG. 2C . If the symmetry center SCEN of the cross quadrate pattern  20  has an x-coordinate of 0 and a y-coordinate of 0, the coordinates of the geometry centers G_U 2 , G_R 2  are labeled as 
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         [0000]    respectively, where the output of the function ƒ(x,y) corresponding to the input (x,y) located within the cross quadrate pattern  20  equals to 1 (i.e., ƒ(x,y)=1), and the output of the function ƒ(x,y) corresponding to the input (x,y) located outside the cross quadrate pattern  20  equals to 0 (i.e., ƒ(x,y)=0). In such a situation, the geometry center G_U 2  and the symmetry center SCEN are separated by a distance DIS_U 2  which equals to 
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         [0000]    The geometry center G_R 2  and the symmetry center SCEN are separated by a distance DIS_R 2  which equals to 
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         [0000]    The distance DIS_U 2  is less than the distance DIS_R 2 , meaning that the area of the cross quadrate pattern  20  tends to be distributed toward the direction x. 
         [0030]    Please note that the planar dual polarization antenna  10  as shown in  FIG. 1A  and  FIG. 1B  is an exemplary embodiment of the invention, and those skilled in the art can make alternations and modifications accordingly. For example, the shape of the upper patch plate  160  may be modified to spread the upper patch plate  160  further out along the direction x.  FIG. 3  is a top-view schematic diagram illustrating a planar dual polarization antenna  30  according to an embodiment of the present invention. Since the structure of the planar dual polarization antenna  30  is similar to that of the planar dual polarization antenna  10  shown in  FIG. 1A , the same numerals and notations denote the same components in the following description, and the similar parts are not detailed redundantly. Different from the planar dual polarization antenna  10 , dimensions of across section  362  of a upper patch plate  360  of the planar dual polarization antenna  30  along the directions x and y are equal to reference dimensions corresponding to the resonance bandwidth respectively; that is to say, the ratio values Ax and Ay are equal to 1. In addition, a quadrilateral section  364  of the upper patch plate  360  comprises protrusion portions  364   a  and  364   b . Therefore, a distance DIS_U 3  between a geometry center G_U 3  and the symmetry center SCEN is less than a distance DIS_R 3  between a geometry center G_R 3  and the symmetry center SCEN, and this means that the upper patch plate  360  is spread out to be more distributed along the direction x. 
         [0031]    Besides,  FIG. 4  is a top-view schematic diagram illustrating a planar dual polarization antenna  40  according to an embodiment of the present invention. The structure of the planar dual polarization antenna  40  is similar to that of the planar dual polarization antenna  10 , and hence the same numerals and notations denote the same components in the following description. Different from the planar dual polarization antenna  10 , dimensions of a cross section  462  of a upper patch plate  460  of the planar dual polarization antenna  40  along the directions x and y are equal to the reference dimensions corresponding to the resonance bandwidth respectively; that is to say, the ratio values Ax and Ay are equal to 1. Additionally, a quadrilateral section  464  of the upper patch plate  460  comprises notches  464   c  and  464   d . Consequently, a distance DIS_U 4  between a geometry center G_U 4  and the symmetry center SCEN is less than a distance DIS_R 4  between a geometry center G_R 4  and the symmetry center SCEN, and this means that the upper patch plate  460  is spread out to be more distributed along the direction x. Similarly,  FIG. 5  is a top-view schematic diagram illustrating a planar dual polarization antenna  50  according to an embodiment of the present invention. The structure of the planar dual polarization antenna  50  is similar to that of the planar dual polarization antenna  40 , and hence the same numerals and notations denote the same components in the following description. Different from the planar dual polarization antenna  40 , a quadrilateral section  564  of the upper patch plate  560  comprises protrusion portions  564   a ,  564   b  and notches  564   c ,  564   d . As a result, a distance DIS_U 5  between a geometry center G_U 5  and the symmetry center SCEN is less than a distance DIS_R 5  between a geometry center G_R 5  and the symmetry center SCEN, and this means that the upper patch plate  560  is spread out to be more distributed along the direction x. 
         [0032]    As set forth above, when the ratio values Ax and Ay are equal to 1, the upper patch plate does not extend or contract in one direction only. However, with the protrusion portions or the notches of the quadrilateral section of the upper patch plate, the geometry centers of different sections of the upper patch plate (divided by the symmetry axes axis_x or axis_y) are separated from the symmetry center SCEN of the upper patch plate by different distances to make area more distributed toward the direction x. 
         [0033]    On the other hand, to enhance antenna gain, the planar dual polarization antenna  10 ,  30 ,  40  and  50  may be arranged to form an array antenna.  FIG. 6  is a top-view schematic diagram illustrating a complex antenna  60  according to an embodiment of the present invention. Similar to the planar dual polarization antenna  10 , the complex antenna  60  is a seven-layered square architecture as well and comprises a feeding transmission line layer  600 , three layers of dielectric layers (not shown), a metal grounding plate  620 , a lower planar dual polarization antenna layer  640  and a upper planar dual polarization antenna layer  660 . Unlike the planar dual polarization antenna  10 , the metal grounding plate  620  can be divided into rectangular regions SC 1  and SC 2  with slots SL_ 1   a , SL_ 1   b , SL_ 2   a  and SL_ 2   b , respectively. The slots SL_ 1   a , SL_ 1   b , SL_ 2   a  and SL_ 2   b  on the rectangular regions SC 1  and SC 2  are disposed corresponding to feeding transmission lines FTL_ 1   a , FTL_ 1   b , FTL_ 2   a  and FTL_ 2   b  of the feeding transmission line layer  600  to feed in radio signals of two polarizations. The lower planar dual polarization antenna layer  640  comprises lower patch plates DPP_ 1  and DPP_ 2  with a shape substantially conforming to a cross pattern, and the upper planar dual polarization antenna layer  660  comprises upper patch plates UPP_ 1  and UPP_ 2  with a shape substantially conforming to the cross quadrate pattern  21 . The lower patch plates DPP_ 1  and DPP_ 2  are disposed corresponding to the rectangular regions SC 1  and SC 2 , and the upper patch plates UPP_ 1  and UPP_ 2  are disposed corresponding to the lower patch plates DPP_ 1  and DPP_ 2 . The maximum dimensions of the upper patch plates UPP_ 1  and UPP_ 2  along the directions x and y are equal to the reference dimension D corresponding to the resonance bandwidth. In other words, the upper patch plates UPP_ 1  and UPP_ 2  do not extend or contract in one direction only (such as the direction x or y), and the ratio values Ax and Ay are equal to 1. Therefore, the dimensions of the upper patch plates UPP_ 1  and UPP_ 2  are directly related to antenna operation frequency. In such a situation, each geometry center and its symmetry center are separated by equal distance. For example, a geometry center G_U 6  of the upper patch plate UPP_ 1  and a symmetry center SCENE of the upper patch plate UPP_ 1  are separated by a distance DIS_U 6 . A geometry center G_R 6  of the upper patch plate UPP_ 1  and the symmetry center SCENE are separated by a distance DIS_R 6  equal to the distance DIS_U 6 . 
         [0034]    Technically, because an LTE base station is generally located near the ground, radiation power of the complex antenna  60  should be concentrated in vertical plane (i.e., the yz plane) within plus or minus 10 degrees elevation angle with respect to the horizon, considering the distance between an LTE base station and a user. In such a situation, the lower patch plates DPP_ 1  and DPP_ 2  vertically aligned to forma 1×2 array antenna can ensure that antenna gain meets system requirements. Moreover, the length L 1  of the rectangular regions SC 1  and SC 2  along the symmetry axis axis_y is longer than the width W 1  of the rectangular regions SC 1  and SC 2  along the direction x, thereby increasing 3 dB beamwidth in horizontal plane (i.e., the xz plane). Table 1 is an antenna characteristic table for the complex antenna  60 . As can be seen from Table 1, the complex antenna  60  meets LTE wireless communication system requirements for maximum gain and front-to-back (F/B) ratio. Furthermore, as the width W 1  of the metal grounding plate  620  shrinks from 100 mm to 70 mm, the beamwidth in horizontal plane can increase to 69.5-73.0 degrees. 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
             
             
               
                 a total length L 
                 200 
                 200 
                 200 
                 200 
               
               
                 of the metal 
               
               
                 grounding plate 
               
               
                 620 (mm) 
               
               
                 the width W1 
                 100 
                  90 
                  80 
                  70 
               
               
                 of the metal 
               
               
                 grounding 
               
               
                 plate 620 (mm) 
               
               
                 maximum gain 
                 11.0-11.6 
                 10.9-11.5 
                 10.7-11.3 
                 10.5-11.1 
               
               
                 (dBi) 
               
               
                 front-to-back 
                 11.5-12.7 
                 11.4-12.4 
                 11.4-12.7 
                 10.1-11.1 
               
               
                 (F/B) ratio (dB) 
               
               
                 3 dB 
                 62.0°-65.5° 
                 64.0°-68.5° 
                 68.0°-70.5° 
                 69.5°-73.0° 
               
               
                 beamwidth in 
               
               
                 horizontal 
               
               
                 plane 
               
               
                 Co/Cx value in 
                 19.8-23.8 
                 19.1-22.5 
                 17.4-20.9 
                 14.7-19.8 
               
               
                 horizontal 
               
               
                 plane 
               
               
                 within 
               
               
                 ±30° (dB) 
               
               
                 Co/Cx value in 
                 22-29 
                 20-29 
                 18-29 
                 14-28 
               
               
                 vertical plane 
               
               
                 within 
               
               
                 ±10° (dB) 
               
               
                   
               
             
          
         
       
     
         [0035]    To further improve Co/Cx value of the complex antenna  60 , the shape of the upper patch plates UPP_ 1  and UPP_ 2  may be modified to in order to balance the inequivalence of the length L 1  and the width W 1 .  FIG. 7  is a top-view schematic diagram illustrating a complex antenna  70  according to an embodiment of the present invention. The structure of the complex antenna  70  is similar to that of the complex antenna  60 , and hence the same numerals and notations denote the same components in the following description. Unlike the complex antenna  60 , the maximum width Wmax of upper patch plates UPP_ 3  and UPP_ 4  of a upper planar dual polarization antenna layer  760  along the direction x is longer than the maximum length Lmax along the direction y to balance the asymmetry of the rectangular regions SC 1  and SC 2  of the metal grounding plate  620  caused by the inequivalence of the length L 1  and the width W 1 . According to the extent to which the length L 1  is longer than the width W 1 , the upper patch plates UPP_ 3  and UPP_ 4  extend along the direction x or contract along the direction y if compared with the reference dimension D of the complex antenna  60 . The ratio value Ax is therefore greater than the ratio value Ay, and each geometry center and its symmetry center are separated by unequal distance. For example, a geometry center G_U 7  of the upper patch plate UPP_ 3  and the symmetry center SCEN of the upper patch plate UPP_ 3  are separated by a distance DIS_U 7 . A geometry center G_R 7  of the upper patch plate UPP_ 3  and the symmetry center SCEN are separated by a distance DIS_R 7  less than the distance DIS_U 7 . Moreover, as the planar dual polarization antenna  10  can be arranged in rows and columns to form the complex antenna  70 , the planar dual polarization antennas  30 ,  40  and  50  can also be arrayed to form the complex antenna  70 . 
         [0036]    In other words, with the array antenna structure, antenna gain of the complex antenna  70  increases. And the width W 1  of the rectangular regions SC 1  and SC 2  is shortened to increase beamwidth. In order to balance inequivalence of the length L 1  and the width W 1 , the upper patch plates UPP_ 3  and UPP_ 4  are spread out to be more distributed along the direction x and thus improve common polarization to cross polarization (Co/Cx) value. Because the present invention merely adjusts the shape of the upper patch plates UPP_ 3  and UPP_ 4  without forming slots on the metal grounding plate  620 , the metal grounding plate  620  in the present invention is confined and enclosed, such that active circuits can be disposed within shielding areas provided by the metal grounding plate  620  in order to isolate the active circuits from the complex antenna  70 . 
         [0037]    Simulation and measurement may be employed to determine whether the complex antenna  70  meets system requirements. Specifically, please refer to Tables 2, 3 and  FIGS. 8A-10E . Tables 2 and 3 are simulation antenna characteristic tables for the complex antenna  70  with the upper patch plates UPP_ 3  and UPP_ 4  corresponding to sizes 1-15 respectively, wherein the total length L of the metal grounding plate  620  is 200 mm, and the width W 1  is 70 mm. As can be seen from Tables 2 and 3, by properly resizing and reshaping the upper patch plates UPP_ 3  and UPP_ 4  of the complex antenna  70 , antenna characteristics can be changed. In particular, when the ratio value Ax increases to 1.02, or when the ratio value Ay decreases to 0.97, Co/Cx value within plus or minus 30 degrees angle can be effectively improved. Alternatively, when the ratio value Ax increases to 1.01 and the ratio value Ay decreases to 0.99, Co/Cx value within plus or minus 30 degrees angle can also be effectively improved. Because the ratio values Ax and Ay approximate 1, reshaping the upper patch plates UPP_ 3  and UPP_ 4  barely shifts resonance frequency and affects the resonance bandwidth. 
         [0000]    
       
         
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                   
                 the 
                 the 
                   
                   
               
               
                   
                 S11 
                 iso- 
                 ratio 
                 ratio 
               
               
                   
                 parameter 
                 lation 
                 value 
                 value 
                 maximum 
                 front-to-back 
               
               
                   
                 (dB) 
                 (dB) 
                 Ax 
                 Ay 
                 gain (dBi) 
                 (F/B) ratio (dB) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 size 1 
                 &gt;11.5 
                 &gt;28.9 
                 1 
                 1 
                 10.4-11.1 
                  9.9-11.0 
               
               
                 size 2 
                 &gt;11.7 
                 &gt;27.7 
                 1.005 
                 1 
                 10.5-11.0 
                  9.8-11.0 
               
               
                 size 3 
                 &gt;11.8 
                 &gt;26.4 
                 1.01 
                 1 
                 10.5-11.0 
                  9.8-11.0 
               
               
                 size 4 
                 &gt;11.8 
                 &gt;25.2 
                 1.015 
                 1 
                 10.5-10.9 
                  9.8-11.0 
               
               
                 size 5 
                 &gt;11.8 
                 &gt;24.0 
                 1.02 
                 1 
                 10.5-10.8 
                  9.7-11.0 
               
               
                 size 6 
                 &gt;10.6 
                 &gt;21.7 
                 1.03 
                 1 
                 10.5-10.7 
                  9.5-10.9 
               
               
                 size 7 
                 &gt;8.2 
                 &gt;18.4 
                 1.05 
                 1 
                 10.0-10.6 
                  9.0-10.9 
               
               
                 size 8 
                 &gt;11.3 
                 &gt;28.6 
                 1 
                 0.995 
                 10.5-11.2 
                 10.1-11.2 
               
               
                 size 9 
                 &gt;11.4 
                 &gt;27.1 
                 1 
                 0.99 
                 10.5-11.2 
                 10.1-11.2 
               
               
                 size 10 
                 &gt;11.3 
                 &gt;25.8 
                 1 
                 0.985 
                 10.5-11.2 
                 10.2-11.1 
               
               
                 size 11 
                 &gt;11.0 
                 &gt;24.6 
                 1 
                 0.98 
                 10.5-11.3 
                 10.3-11.2 
               
               
                 size 12 
                 &gt;10.9 
                 &gt;23.8 
                 1 
                 0.975 
                 10.4-11.3 
                 10.3-11.3 
               
               
                 size 13 
                 &gt;10.8 
                 &gt;22.9 
                 1 
                 0.97 
                 10.5-11.3 
                 10.4-11.3 
               
               
                 size 14 
                 &gt;10.3 
                 &gt;18.6 
                 1 
                 0.95 
                 10.4-11.3 
                 10.7-11.5 
               
               
                 size 15 
                 &gt;11.7 
                 &gt;24.3 
                 1.01 
                 0.99 
                 10.5-11.0 
                 10.0-11.1 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                   
                 Co/Cx value in 
                   
               
               
                   
                 3 dB beamwidth in 
                 horizontal plane 
                 Co/Cx value in vertical 
               
               
                   
                 horizontal plane 
                 within ±30° (dB) 
                 plane within ±10° (dB) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 size 1 
                 69.5°-73.5° 
                 14.3-19.4 
                 14-26 
               
               
                 size 2 
                 69.5°-73.0° 
                 15.1-19.0 
                 15-30 
               
               
                 size 3 
                 69.5°-73.5° 
                 15.6-19.1 
                 15-32 
               
               
                 size 4 
                 69.5°-72.5° 
                 16.2-19.4 
                 16-28 
               
               
                 size 5 
                 70.0°-73.0° 
                 16.4-19.8 
                 17-25 
               
               
                 size 6 
                 69.5°-73.0° 
                 14.9-20.5 
                 18-27 
               
               
                 size 7 
                 69.0°-73.0° 
                 11.6-22.8 
                 14-29 
               
               
                 size 8 
                 69.5°-73.5° 
                 14.9-19.4 
                 15-30 
               
               
                 size 9 
                 69.5°-73.0° 
                 15.5-19.3 
                 15-35 
               
               
                 size 10 
                 69.5°-73.0° 
                 15.9-19.6 
                 16-32 
               
               
                 size 11 
                 69.5°-73.5° 
                 16.5-20.5 
                 16-27 
               
               
                 size 12 
                 69.5°-73.0° 
                 16.8-20.6 
                 17-25 
               
               
                 size 13 
                 69.5°-73.0° 
                 17.1-21.1 
                 18-26 
               
               
                 size 14 
                 69.5°-73.0° 
                 15.5-22.9 
                 18-31 
               
               
                 size 15 
                 69.5°-73.0° 
                 16.7-20.2 
                 17-26 
               
               
                   
               
             
          
         
       
     
         [0038]      FIG. 8A  is a schematic diagram illustrating antenna resonance simulation results of the complex antenna  70  corresponding to size 5 (of the ratio value Ax equal to 1.02 and the ratio value Ay equal to 1), wherein the maximum width Wmax and the maximum length Lmax are 52.89 mm and 51.85 mm, respectively.  FIG. 9A  is a schematic diagram illustrating antenna resonance simulation results of the complex antenna  70  corresponding to size 13 (of the ratio value Ax equal to 1 and the ratio value Ay equal to 0.97), wherein the maximum width Wmax and the maximum length Lmax are 51.85 mm and 50.30 mm, respectively.  FIG. 10A  is a schematic diagram illustrating antenna resonance simulation results of the complex antenna  70  corresponding to size 15 (of the ratio value Ax equal to 1.01 and the ratio value Ay equal to 0.99), wherein the maximum width Wmax and the maximum length Lmax are 52.37 mm and 51.34 mm, respectively. In  FIGS. 8A, 9A and 10A , dotted and solid lines respectively indicate antenna resonance simulation results for a 45-degree slant polarization and a 135-degree slant polarization of the complex antenna  70 , while a dashed line indicates antenna isolation simulation results between the 45-degree slant polarization and the 135-degree slant polarization of the complex antenna  70 . 
         [0039]    In addition,  FIGS. 8B to 8E  are schematic diagrams illustrating antenna pattern characteristic simulation results of the complex antenna  70  corresponding to size 5 operated at 2.3 GHz, 2.4 GHz, 2.496 GHz and 2.69 GHz respectively when applied to an LTE wireless communication system.  FIGS. 9B to 9E  are schematic diagrams illustrating antenna pattern characteristic simulation results of the complex antenna  70  corresponding to size 13 operated at 2.3 GHz, 2.4 GHz, 2.496 GHz and 2.69 GHz respectively when applied to an LTE wireless communication system.  FIGS. 10B to 10E  are schematic diagrams illustrating antenna pattern characteristic simulation results of the complex antenna  70  corresponding to size 15 operated at 2.3 GHz, 2.4 GHz, 2.496 GHz and 2.69 GHz respectively when applied to an LTE wireless communication system. In  FIGS. 8B to 8E, 9B to 9E and 10B to 10E , common polarization radiation pattern of the complex antenna  70  in horizontal plane (i.e., at 0 degrees) is presented by a solid line, common polarization radiation pattern of the complex antenna  70  in vertical plane (i.e., at 90 degrees) is presented by a dotted line, cross polarization radiation pattern of the complex antenna  70  in horizontal plane is presented by a long dashed line, and cross polarization radiation pattern of the complex antenna  70  in vertical plane is presented by a short dashed line.  FIGS. 8A to 10E  show that the beamwidth of the complex antenna  70  in horizontal plane is wide and the complex antenna  70  meets LTE wireless communication system requirements for maximum gain and front-to-back (F/B) ratio. Besides, Co/Cx value of the complex antenna  70  can be effectively improved. 
         [0040]    Please note that the planar dual polarization antennas  10 ,  30 ,  40 ,  50  and the complex antennas  60 ,  70  are exemplary embodiments of the invention, and those skilled in the art can make alternations and modifications accordingly. For example, portions of the feeding transmission lines  102   a ,  102   b , FTL_ 1   a , FTL_ 1   b , FTL_ 2   a , FTL_ 2   b  and the slots  122   a ,  122   b , SL_ 1   a , SL_ 1   b , SL_ 2   a , SL_ 2   b  may be modified according to different considerations, which means that degrees of the included angles enclosed by two adjacent portions can be either obtuse or acute angles, length ratios or width ratios of the portions may be changed, and the shape and the number of portions may vary. Also, having a shape “substantially conforming to a cross pattern” recited in the present invention relates to the lower patch plates  140 , DPP_ 1 , DPP_ 2  and the upper patch plates  160 ,  360 ,  460 ,  560 , UPP_ 1 , UPP_ 2 , UPP_ 3 , UPP_ 4  being formed by two overlapping and intercrossing quadrilateral patch plates. However, the present invention is not limited thereto, and any patch plate having a shape “substantially conforming to a cross pattern” is within the scope of the present invention. For example, a patch plate extends outside a quadrilateral side plate; alternatively, a patch plate extends outside a saw-tooth shaped side plate; alternatively, a patch plate further extends outside an arc-shaped side plate; alternatively, edges of a patch plate are rounded. The protrusion portions  364   a ,  364   b ,  564   a ,  564   b  and the notches  464   c ,  464   d ,  564   c ,  564   d  of the quadrilateral sections  364 ,  464 ,  564  can be quadrilateral, but the present invention is not limited thereto and other geometric patterns are also feasible. The dielectric layers  110 ,  130 ,  150  can be made of various electrically isolation materials such as air; moreover, the dielectric layers  110 ,  130 ,  150  in fact depend on bandwidth requirements and may therefore be optional. The complex antennas  60  and  70  are 1×2 array antennas, but not limited thereto and can be 1×3, 2×4 or m×n array antennas. 
         [0041]    On the other hand, to reduce the beamwidth in horizontal plane (i.e., the xz plane), the width of the metal grounding plate along the direction x may be enlarged.  FIG. 11  is a top-view schematic diagram illustrating a complex antenna  80  according to an embodiment of the present invention. The structure of the complex antenna  80  is substantially similar to that of the complex antenna  70 , and the similar parts are not detailed redundantly. Different from the complex antenna  70 , a width W 8  of a metal grounding plate  820  along the direction x is increased to make the antenna pattern in horizontal plane converge. Therefore, a length L 8  of rectangular regions SC 8  and SC 9  of the metal grounding plate  820  along the symmetry axis axis_y is less than the width W 8  of the rectangular regions SC 8  and SC 9  along the direction x. Furthermore, the maximum width Wmax 8  of the upper patch plates UPP_ 8  and UPP_ 9  of the upper planar dual polarization antenna layer  860  along the direction x is shorter than the maximum length Lmax 8  along the direction y to balance the asymmetry of the metal grounding plate  820  caused by the inequivalence of the length L 8  and the width W 8 . In other words, the upper patch plates UPP_ 8  and UPP_ 9  extend along the direction y or contract along the direction x, which makes the ratio value Ax less than the ratio value Ay and distances between geometry centers and the symmetry center different. For example, a geometry center G_U 8  of the upper patch plate UPP_ 8  and the symmetry center SCEN of the upper patch plate UPP_ 8  are separated by a distance DIS_U 8 . A geometry center G_R 8  of the upper patch plate UPP_ 8  and the symmetry center SCEN are separated by a distance DIS_R 8  less than the distance DIS_U 8 . 
         [0042]    To sum up, by adjusting the ratio of the length to the width of each rectangular region of the metal grounding plate corresponding to each upper patch plate, beamwidth increases. In order to balance inequivalence of the length and the width of each rectangular region, the upper patch plates are spread out to be more distributed along one specific direction, thereby improving Co/Cx value. Without forming slots on the metal grounding plate, the metal grounding plate in the present invention is confined and enclosed, such that active circuits can be disposed within shielding areas provided by the metal grounding plate in order to isolate the active circuits from the antenna. 
         [0043]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method 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.