Abstract:
A planar antenna disposed on a substrate ( 50 ) including a first surface ( 57 ) and a second surface ( 58 ). The planar antenna includes a radiating body ( 10 ) for transmitting and receiving radio frequency (RF) signals, a feeding portion ( 30 ) for feeding signals, and a metallic ground plane ( 50 ). The radiating body includes an angled gap ( 15 ) formed therein. The feeding portion is electrically connected to the radiating body. The radiating body and the feeding portion are laid on the first surface of the substrate. The ground plane is laid on the second surface of the substrate.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to planar antennas, and particularly to a planar antenna for use in ultra-wideband (UWB) communication systems. 
         [0003]    2. Description of Related Art 
         [0004]    A frequency band of an ultra-wideband (UWB) wireless communication system is 3.1-10.6 GHz. In a wireless communication system, the antenna is a key element for radiating and receiving radio frequency signals. Therefore, an operating frequency band of the antenna must be 3.1-10.6 GHz or greater. 
       SUMMARY OF THE INVENTION 
       [0005]    An exemplary embodiment of the present invention provides a planar antenna disposed on a substrate including a first surface and a second surface. The planar antenna includes a radiating body for transmitting and receiving radio frequency (RF) signals, a feeding portion for feeding signals, and a metallic ground plane. The radiating body includes an angled gap formed therein. The feeding portion is electrically connected to the radiating body. The radiating body and the feeding portion are laid on the first surface of the substrate. The ground plane is laid on the second surface of the substrate. 
         [0006]    Other advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a schematic plan view of a planar antenna of an exemplary embodiment of the present invention; 
           [0008]      FIG. 2  is similar to  FIG. 1 , but viewed from another aspect; 
           [0009]      FIG. 3  is a schematic plan view illustrating dimensions of the planar antenna of  FIG. 1 ; 
           [0010]      FIG. 4  is a schematic plan view illustrating dimensions of the planar antenna of  FIG. 2 ; 
           [0011]      FIG. 5  is a graph of test results showing a voltage standing wave ratio (VSWR) of the planar antenna of  FIG. 1 ; 
           [0012]      FIG. 6  is a graph of test results showing a radiation pattern when the planar antenna of  FIG. 1  is operated at 3.1 GHz; 
           [0013]      FIG. 7  is a graph of test results showing a radiation pattern when the planar antenna of  FIG. 1  is operated at 7.0 GHz; and 
           [0014]      FIG. 8  is a graph of test results showing a radiation pattern when the planar antenna of  FIG. 1  is operated at 10.6 GHz. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]      FIG. 1  is a schematic plan view of a planar antenna of an exemplary embodiment of the present invention. In the exemplary embodiment, the planar antenna is printed on a substrate  50 . 
         [0016]    Referring also to  FIG. 2 , the substrate  50  comprises a first surface  57 , a second surface  58  parallel to the first surface  57 , a first side  52 , a second side  54  parallel to the first side  52 , and a third side  56  perpendicular to the first side  52 . 
         [0017]    The planar antenna comprises a radiating body  10 , a metallic ground plane  40 , and a feeding portion  30 . The radiating body  10  and the feeding portion  30  are printed on the first surface  57 . The ground plane  40  is printed on the second surface  58 . 
         [0018]    The radiating body  10  transmits and receives radio frequency (RF) signals. The radiating body  10  comprises a main body  12  and a connecting portion  14  electrically connecting the main body  12  and the feeding portion  30 . A length of the connecting portion  14  along a connecting side of the radiating body  10  with the connecting portion  14  is smaller than a width of the radiating body  10  along the same connecting side of the radiating body  10  (See below descriptions of  FIG. 3  for more details). An L-shaped gap  15  is formed in the main body  12 , thereby the main body  12  is divided into a first radiating portion  122  and a second radiating portion  124 . The second radiating portion  124  partly surrounds the first radiating portion  122 . The connecting portion  14  electrically connects the first radiating portion  122  and the feeding portion  30 . The gap  15  comprises a first portion  152 , and a second portion  154  perpendicularly communicating with the first portion  152 . The first portion  152  extends from a side of the main body  12  adjacent to the second side  54  of the substrate  50  terminating near an opposite side of the main body  12  adjacent to the first side  52  of the substrate  50 . The second portion  154  extends from a distal end of the first portion  152  terminating near the connecting portion  14 . In alternative embodiments, the gap  15  may form other angled shapes besides an L, such as a W-shape, a C-shape, and so on. The connecting portion  14  is defined as a part of the first radiating portion  122 . 
         [0019]    The feeding portion  30  is electrically connected to and feeds signals to the radiating portion  10 . The feeding portion  30  is generally parallel to the second side  54  of the substrate  50 , and is a  50 Ω transmission line. 
         [0020]    The ground plane  40  comprises a rectangular first ground portion  42 , a rectangular second ground portion  44 , and a rectangular third ground portion  46  connecting the first ground portion  42  with the second ground portion  44 . 
         [0021]    In the exemplary embodiment, an operating frequency band of the first radiating portion  122  overlaps an operating frequency band of the second radiating portion  124 , thereby bandwidth of the planar antenna is increased. 
         [0022]      FIGS. 3 and 4  are schematic plan views illustrating dimensions of the planar antenna of  FIG. 1 . In the exemplary embodiment, a length M of the main body  12  is generally 10.75 mm, and a width m of the main body  12  is generally 11.0 mm. A length A, of the connecting portion  14  is generally 6.0 mm, and a width a, of the connecting portion  14  is generally 11.0 mm. A distance K between the connecting portion  14  and the side of the main body  12  adjacent to the second side  54  of the substrate  50  is generally 4.5 mm. A distance L 3  between the first portion  152  of the gap  15  and a side of the main body  12  adjacent to the third side  56  of the substrate  50  is generally 1.0 mm. A length C of the first portion  152  of the gap  15  is generally 10.5 mm, and a width c of the first portion  152  is generally 0.1 mm. A length D of the second portion  154  of the gap  15  is generally 7.5 mm, and a width d of the second portion  154  is generally 0.1 mm. A length Q of the first ground portion  42  is generally 2.5 mm, and a width q of the first ground portion  42  is generally 1.5 mm. A length E of the second ground portion  44  is generally 3.0 mm, and a width e of the second ground portion  44  is generally 2.5 mm. A length F of the third ground portion  46  is generally 5.0 mm, and a width f of the third ground portion  46  is generally 0.5 mm. 
         [0023]      FIG. 5  is a graph of test results showing voltage standing wave ratios (VSWR) at UWB frequencies, of the planar antenna. A horizontal axis represents the frequency (in GHz) of the electromagnetic signals traveling through the planar antenna, and a vertical axis represents VSWR. VSWR of the planar antenna over the UWB range of frequencies is indicated by a curve. As shown in  FIG. 4 , the planar antenna has a good performance when operating at frequencies from 3.1-10.6 GHz. The amplitudes of the VSWRs in the band pass frequency range are less than 2, which is what is required for an antenna used in UWB systems. 
         [0024]      FIGS. 6-8  are graphs of test results showing radiation patterns when the planar antenna of  FIG. 1  is operated at 3.1 GHz, 7.0 GHz, and 10.6 GHz, respectively. As seen, all of the radiation patterns are substantially omni-directional. 
         [0025]    While embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only and not by way of limitation. Thus the breadth and scope of the present invention should not be limited by the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.