Abstract:
Planer inverted-F antennas are easily assembled into one device without diversity. The device diminishes interferences and polarization of the antenna to obtain high gain.

Description:
FIELD OF THE INVENTION  
       [0001]    The present invention relates to planer inverted-F antenna (PIFA); more particularly, relates to simplifying an assembling of the antenna and obtaining a high gain by reducing interruption of the antenna. 
       DESCRIPTION OF THE RELATED ARTS  
       [0002]    A general antenna is polarized. A so-called all-direction antenna is only an ante n n a with weak polarization. To avoid interferences owing to polarization on receiving signals by a wireless device, at least two antennas are extended out with diversity from a signal transferring device of the wireless device. The extended antennas are set at various places, or even are polarized to different directions, to reduce the interference owing to the polarization. 
         [0003]    In another way, a metal conductive element is set around the PIFA to change an electronical characteristic or a frequency characteristic of a PIFA The metal conductive element itself is not an antenna, only to change the electronical characteristic or the frequency characteristic of the PIFA by electromagnetic induction between the metal conductive element and the antenna so that a radio characteristic of the antenna is enhanced and a limited space in an electronical device is well used to obtain a wider bandwidth for the antenna. Because it is useless to use the metal conductive element alone, the metal conductive element is called a parasitic element. 
         [0004]    In  FIG. 9 , a U.S. patent is shown, called “Multi-band planar inverted-F antennas including floating parasitic elements and wireless terminals incorporating the same.” The prior art comprises a multi-band PIFA  7  and a floating parasitic element  71 , where the multi-band PIFA  7  has two frequency bands. One is between 1710 and 1990 mega-hertz (MHz), which is extended from a first terminal  72  toward a second terminal  73 . The other is between 824 and 894 MHz. Because the parasitic element  71  is isolated from the multi-band PIFA  7  without circuit connected, the parasitic element  71  is called a floating parasitic element. Although the floating parasitic element seems been isolated, the floating parasitic element and the multi-band PIFA  7  is related electromagnetically; especially, the second frequency band of the multi-band PIFA  7  is closely related to the floating parasitic element. By referring to  FIG. 10 , it is found that, when no floating parasitic element is used, a voltage standing wave ratio (VSWR) curve of the multi-band PIFA  7  is shown as the first curve  8 . After the floating parasitic element is used, a new VSWR curve of the multi-band PIFA  7  is shown as the second curve  81 . It is concluded that the floating parasitic element enhances the frequency bands of the multi-band PIFA  7 . However, the prior art is still interfered by the polarization. 
         [0005]    Moreover, a minimization in size and a maximization in function are both true to an electronical device now. The space for setting an antenna device in an electronical device is getting smaller, while the frequency bands of the antenna device is asked to be getting wider. But these two requirements are basically contradictive. Hence, the prior arts do not fulfill users&#39; requests on actual use. 
       SUMMARY OF THE INVENTION  
       [0006]    The main purpose of the present invention is to have a base plate shared by and connected with three grounding plates of three antennas so that an antenna device is easily assembled without diversity, and interruption of the antenna device is reduced to obtain a high gain. 
         [0007]    To achieve the above purpose, the present invention is a planer inverted-F antenna (PIFA) device, comprising a base plate; a first antenna at a side of an end of the base plate; a second antenna at a side in middle of the base plate; and a third antenna at a side of another end of the base plate, where the first, the second and the third antennas each has a grounding plate laterally connected at a side of the and a connecting plate connecting the grounding plate and the frequency plate. Accordingly, a novel PIFA device is obtained. 
     
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS  
         [0008]    The present invention will be better understood from the following detailed description of the preferred embodiment according to the present invention, taken in conjunction with the accompanying drawings, in which 
           [0009]      FIG. 1  is the perspective view of the preferred embodiment according to the present invention; 
           [0010]      FIG. 2  is an other perspective view of the present invention; 
           [0011]      FIG. 3A  is the view of the specifications of the present invention; 
           [0012]      FIG. 3B  is the view of the specifications of the first invention; 
           [0013]      FIG. 3C  is the view of the specifications of the first antenna; 
           [0014]      FIG. 3D  is the view of the specifications of the first antenna; 
           [0015]      FIG. 4  is the view showing the state of assembly; 
           [0016]      FIG. 5  is the view showing the state of use; 
           [0017]      FIG. 6  is the view of the prior art; and 
           [0018]      FIG. 7  is the VSWR view of the prior art. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0019]    The following description of the preferred embodiment is provided to understand the features and the structures of the present invention. 
         [0020]    Please refer to  FIG. 1 , which is a perspective view of a preferred embodiment according to the present invention. As shown in the figure, the present invention is a planer inverted-F antenna (PIFA) device, comprising a baseplate  1 , a first antenna  2 , a second antenna  3  and a third antenna  4 , where an assembling of an antenna device is simplified and interruption of the antenna device is reduced to obtain a high gain. 
         [0021]    The base plate  1  is flat, whose length is 124 millimeters (mm); and the height of the base plate  1  together with antennas  2 ,  3 ,  4  is 14 mm. 
         [0022]    The first antenna  2  comprises a first grounding plate  21  laterally being connected at a side of an end of the baseplate  1 ; a first frequency plate  22  corresponding to the first grounding plate  21 ; and a first connecting plate  23  connecting the first grounding plate  21  and the first frequency plate  22 , where the first grounding plate  21  has a first grounding conductor  211 ; the first grounding conductor  211  has a length of 7.2 m m; the first frequency plate  22  has a length of 25 mm; and the first connecting plate  23  has a first feed-in conductor  231 . 
         [0023]    The second antenna  3  comprises a second grounding plate  31  being laterally connected at a side in middle of the base plate  1 ; a second frequency plate  32  corresponding to the second grounding plate  31 ; and a second connecting plate  33  connecting the second grounding plate  31  and the second frequency plate  32 , where the second grounding plate  31  has a second grounding conductor  311 ; the second grounding conductor  311  has a length of 14 mm; and the second frequency plate  32  has a length of 29.5 mm. 
         [0024]    The third antenna  4  comprises a third grounding plate  41  being laterally connected at a side of another end of the baseplate  1 ; a third frequency plate  42  corresponding, to the third grounding plate  41 ; and a third connecting plate  43  connecting the third grounding plate  41  and the third frequency plate  42 , where the third grounding plate  41  has a third grounding conductor  411 ; the third grounding conductor  411  has a length of 6.2 mm; the third frequency plate  42  has a length of 24 mm; and the third connecting plate  43  has a second feed-in conductor  431 . 
         [0025]    Please refer to  FIG. 4  and  FIG. 5 , which are views showing a state of assembly and a state of use. As shown in the figures, when using the present invention, various coaxial leading wires  5 ,  5   a ,  5   b  are connected to the first, the second and the third antennas  2 , 3 , 4  respectively. The coaxial leading wires  5 ,  5   a ,  5   b  used in a mobile communication device  5 ,  5   a ,  5   b  comprises a central leading line  51 ,  51   a ,  51   b  and a braid metal shielding net  52 ,  52   a ,  52   b  respectively. The central leading line  51 ,  51   a,    51   b  is used to transfer signals; and the braid metal shielding net  52 ,  52   a ,  52   b  is used to keep the line from interferences from outside. 
         [0026]    When the first, the second and the third antennas  2 ,  3 ,  4  are connected with the various coaxial leading wires  5 ,  5   a ,  5   b  respectively, the central leading lines  51 ,  51   a ,  51   b  is fixed to the first feed-in conductor  231 , the second frequency plate  32 , and the second feed-in conductor  431  respectively; and the braid metal shielding nets  52 ,  52   a ,  52   b  are fixed to the first, the second and the third grounding conductors  211 ,  311 ,  411  respectively. And, then, the assembled antenna device is fixed on a proper place of an electronical device  6 , such as a notebook computer. 
         [0027]    The present invention has an acceptable interference from all directions; and the present invention receives signals having a frequency between 2.4 GHz and 2.5 GHz, whose isolation is acceptable. Hence, the present invention receives signals having a frequency between 2.4 GHz and 2.5 GHz without interference in between. 
         [0028]    To sum up, the present invention is a PIFA device, where multiple antennas share and connect to the same base plate with grounding plates to obtain an antenna device without diversity so that an assembling of the antenna device is simplified and interruption of the antenna device is reduced to obtain a high gain. 
         [0029]    The preferred embodiment herein disclosed is not intended to unnecessarily limit the scope of the invention. Therefore, simple modifications or variations belonging to the equivalent of the scope of the claims and the instructions disclosed herein for a patent are all with in the scope of the present invention.