Abstract:
A wide-band antenna ( 1 ) for a wireless communication device has a ground plane ( 14 ), a first radiating portion ( 11 ), a second radiating portion ( 12 ), and a third radiating portion ( 13 ). The first and second radiating portions both extend from a same edge of the ground plane and together constitute a first frequency resonant structure. The third radiating portion extends from a proximal end of the second radiating portion. The second and third radiating portions together constitute a second frequency resonant structure.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates in general to antenna structures, and in particular to a wide-band antenna structure in a wireless communication device.  
           [0003]    2. Description of the Prior Art  
           [0004]    There is a growing need for micro-strip patch antennas for use in wireless communication devices to receive and transmit RF signals. However, patch antennas have a major disadvantage: narrow bandwidth.  
           [0005]    [0005]FIG. 1 shows a conventional antenna  3  comprising a ground element  33  and a first and second radiating elements  31 ,  32 . The first and second radiating elements  31 ,  32  together constitute a frequency resonant structure. FIG. 2 shows a computer simulated return loss chart for the antenna  3 . A value of the return loss below the threshold value “−10 dB” between point C and point D shown in the FIG. 2 indicates acceptably efficient operation bandwidth. This bandwidth of acceptably efficient operation of the antenna  3  lies between point C, corresponding to 2.32 GHz, and point D, corresponding to 2.56 GHz. Thus, the bandwidth of the antenna  3  is only 0.24 GHz.  
           [0006]    However, the conventional antenna only has one resonating frequency so that the operating bandwidth of the antenna is narrow.  
           [0007]    Hence, an improved antenna with a wider bandwidth is desired to overcome the above-mentioned shortcoming of the existing antenna.  
         BRIEF SUMMARY OF THE INVENTION  
         [0008]    A primary object of the present invention is to provide an antenna with two resonating frequencies, which yield a wider operating bandwidth.  
           [0009]    A wide-band antenna in accordance with the present invention for a wireless communication device comprises a ground plane, a first radiating portion, a second radiating portion, and a third radiating portion. The first and second radiating portions both extend from a first edge of the ground plane. The third radiating portion bends from a second edge of the second radiating portion. The first radiating portion has a first radiating patch and a first connecting patch connecting an end of the first radiating patch with the first edge of the ground plane. The second radiating portion has a second radiating patch and a second connecting patch connecting an end of the second radiating patch with the first edge of the ground plane. The third radiating portion has a third radiating patch and a third connecting patch connecting the second radiating patch with an end of the third radiating patch. A coaxial cable feeder has a conductive inner core and a conductive outer shield. The inner core is connected to the second radiating patch and the outer shield is connected to the first connecting patch. The first radiating patch, the second radiating patch, and a first aperture defined therebetween constitute a first frequency resonant structure. The second radiating patch, the third radiating patch, and a second aperture defined therebetween constitute a second frequency resonant structure. 
       
    
    
       [0010]    Other objects, advantages and novel features of the invention will become more apparent from the following detailed description of a preferred embodiment when taken in conjunction with the accompanying drawings.  
       BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a perspective view of a conventional antenna;  
         [0012]    [0012]FIG. 2 is a computer simulated return loss chart for the conventional antenna of FIG. 1.  
         [0013]    [0013]FIG. 3 is a perspective view of a preferred embodiment of a wide-band antenna in accordance with the present invention;  
         [0014]    [0014]FIG. 4 computer simulated return loss chart for the wide-band antenna of FIG. 3. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    Reference will now be made in detail to a preferred embodiment of the present invention.  
         [0016]    Referring to FIG. 3, a wide-band antenna  1  in accordance with the present invention is integrally made from a metal sheet, and includes a first radiating portion  11 , a second radiating portion  12 , a third radiating portion  13 , and a ground plane  14 . The first, second and third radiating portions  11 ,  12  and  13  all have L-shaped structures. The ground plane  14  has a substantially elongated rectangular shape with a first edge (not labeled) being parallel to a longitudinal axis of the ground plane. The first and second radiating portions  11 ,  12  both extend from the first edge of the ground plane  14 , and near one end of the ground plane  14 . The second radiating portion  12  has a second edge (not labeled). The third radiating portion  13  bends from the second edge of the second radiating portion  12 .  
         [0017]    The first radiating portion  11  includes an elongated rectangular first radiating patch  110  and a first connecting patch  111  connecting an end of the first radiating patch  110  with the first edge of the ground plane  14 . The first connecting patch  111  is perpendicular to the first edge of the ground plane  14  and the first radiating patch  110  is perpendicular to the first connecting patch  111 . The second radiating portion  12  includes an elongated rectangular second radiating patch  120  and a second connecting patch  121  connecting an end of the second radiating patch  120  with the first edge of the ground plane  14 . The second connecting patch  121  is perpendicular to the first edge of the ground plane  14  and the second radiating patch  120  is perpendicular to the second connecting patch  121 . The third radiating portion  13  includes an elongated rectangular third radiating patch  130  and a third connecting patch  131  connecting an end of the third radiating patch  130  and the second radiating patch  120 . The third connecting patch  131  bends upwardly from the second edge of the second radiating patch  120 . The third connecting patch  131  is perpendicular to the second edge of the second radiating patch  120  and the third radiating patch  130  is perpendicular to the third connecting patch  131 . Axes of the first, second and third radiating patches  110 ,  120  and  130  are parallel to the longitudinal axis of the ground plane  14 . A first aperture  16  is defined between the first and second radiating patches  110 ,  120 . A second aperture  17  is defined between the second and third radiating patches  120 ,  130 .  
         [0018]    A coaxial cable feeder  15  comprises a conductive inner core  150 , an inner dielectric layer (not labeled) around the inner core  150 , a conductive outer shield  151  around the inner dielectric layer, and an outer dielectric layer (not labeled) around the conductive outer shield  151 . The inner core  150  is soldered onto a top surface of the second radiating patch  120  near the junction with the third connecting patch  131 , and the outer shield  151  is soldered onto a top surface of the first connecting patch  111 . RF signals are fed to the wide-band antenna  1  through the conductive inner core  150  of the coaxial cable  15 . The location of the solder point of the inner core  150  on the second radiating patch  120  is predetermined to achieve a desired matching impedance.  
         [0019]    The first and second radiating patches  110 ,  120  together constitute a first resonant structure. A first resonating frequency electric field is formed in the first aperture  16  defined between the first and second radiating patches  110 ,  120 , radiating at a first resonating frequency. The second and third radiating patches  120 ,  130  together constitute a second resonant structure. A second resonating frequency electric field is formed in the second aperture  17  defined between the second radiating patch  120  and the third radiating patch  130 , radiating at a second resonating frequency.  
         [0020]    [0020]FIG. 4 shows a computer simulated return loss chart for the wide-band antenna  1 . A value of the return loss below the threshold value “−10 dB” indicates acceptably efficient operation. In FIG. 4, values of return loss are below “−10 dB” for all frequencies between points A and B, which correspond to the frequencies 2.32 GHz and 2.66 GHz. Therefore, the bandwidth of acceptably efficient operation is indicated to be 2.32 GHz to 2.66 GHz, so the bandwidth is 0.34 GHz wide. This compares favorably with the 0.24 GHz bandwidth of the prior art antenna. The bandwidth is this wide because the wide-band antenna has two resonating frequencies, whose bands of acceptable return losses overlap.  
         [0021]    It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.