Abstract:
A multi-band antenna has a ground portion, a first radiating portion defining opposite first and second ends, a L-shaped radiating portion connected to the second end of the first radiating portion and defining a third end extending towards the ground portion and a fourth end extending towards a direction, a stair-shaped radiating portion located between the ground portion and the L-shaped radiating portion and defining a fifth end connected to the first end of the first radiating portion and a sixth end extending towards the direction, and having at least one bent section, which has at least one bent section, a connecting portion interconnecting the bent section of the fourth radiating portion and the ground portion, and a feeding point arranged at the first end of the first radiating portion.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an antenna, more specifically, an antenna capable of receiving and transmitting various frequency bands at the same time. 
         [0003]    2. The Related Art 
         [0004]    With the progress of broadcasting information and electronic technology, the technology of electronic products such as computers, mobile phones and network communication products is rapidly developed. Hence, the electronic products have the advantages of compact size, low price and multiple functions. 
         [0005]    Especially, network communication products are popularly used in daily life and at various spaces, such as office, home, automobile, etc. And therefore improves the convenience of information communication. Because various network communication products are rapidly upgraded in marketing, the requests for advanced functions of the network communication products are increased. Hence, combining various functions and services of convenience and efficiency are important appraisals for the network communication products. 
         [0006]    With the rapid progress of the portable communication products, antenna products are aimed by electronic component manufacturers. Due to the antennas capable of transferring current into radio wave and transferring radio wave into current, it is a major component in communication system. Thus, the efficiency and the gain of the antenna may directly affect the quality of transmitted data in the communication system. Hence, the electronic component manufacturers spend a lot of time and money to improve the efficiency and the gain of the antenna in order to improve quality and sale quantity of the portable communication products. 
         [0007]    Institute of Electrical and Electronic Engineer (IEEE) 802.11a/b/g and 802.16e are general standards of wireless local area network nowadays. IEEE 802.11a operates at 5.2 GHz band (5.15 GHz to 5.875 GHz). IEEE 802.11b/g operates at 2.4 GHz band (2.412 GHz to 2.462 GHz). IEEE 802.16e operates about 2 GHz to 6 GHz. Frequency bands covering 2.6 GHz and 3.5 GHz are two channels in IEEE 802.16e standard. 
         [0008]    In order to improve the feature of compatibility, the antenna configured in the portable communication products is capable of receiving and transmitting signals carried through at least two wireless local area network frequency bands for conforming IEEE standards mentioned above. Hence, the antenna operated at least two wireless local area network frequency bands becomes an essential component of the portable communication products. 
         [0009]    The antenna has the external type and the embedded type. Generally speaking, the embedded antenna is more preferable than the external antenna for the portable communication products owing to the mechanical and ergonomic reasons. The embedded antenna is protected by the portable communication products case or housing and therefore tend to be more durable than external antenna. 
         [0010]    A conventional antenna is disclosed at Taiwan patent M329873. The conventional antenna includes a grounding element having a first side, a radiating element separated from the first side of the grounding element, and a connecting element. The radiating element has a first radiating section and a second radiating section. The connecting element connects the grounding element to the radiating element and includes a first end slantwise extending from the grounding element to form a first angle except a right angle between the connecting element and the grounding element. 
         [0011]    The first radiating section of the radiating element can receive and transmit signals carried through a higher band covering 5.2 GHz. The second radiating section of the radiating element can receive and transmit signals carried through a lower band covering 2.4 GHz. Hence, the conventional antenna can operate at IEEE 802.11a/b/g standard. 
         [0012]    However, the conventional antenna operated according to IEEE 802.11 standard can not be operated at IEEE 802.16e standard covering 2.6 GHz and 3.5 GHz at the same time. 
       SUMMARY OF THE INVENTION 
       [0013]    An object of the present invention is to provide a multi-band antenna capable of operating with various wireless local area network frequency bands. 
         [0014]    According to the invention, the multi-band antenna has a feeding point, a ground portion, a first radiating portion, a second radiating portion, a third radiating portion, a fourth radiating portion and a connecting portion. The ground portion extends in a first direction. The first radiating portion extends in a second direction perpendicular to the first direction and defines a first end close to the ground portion, a second end opposite to the first end, a first side and a second side opposite to the first side. 
         [0015]    The second radiating portion extends from the first side of the second end of the first radiating portion. The third radiating portion extends in the first direction and from the second side of the second end of the first radiating portion. The fourth radiating portion extends from the second side of the first end of the first radiating portion and is located between the ground portion and the third radiating portion. The connecting portion interconnects the ground portion and the fourth radiating portion. The feeding point is located at the first end of the first radiating portion. 
         [0016]    The feeding point, the ground portion, the first radiating portion, the second radiating portion, a part of the fourth radiating portion, and the connecting portion are formed as a first Inverted-F antenna which resonates at a first band covering 5.2 GHz corresponding to IEEE 802.11a. 
         [0017]    The feeding point, the ground portion, the first radiating portion, the third radiating portion, the part of the fourth radiating portion, and the connecting portion are formed as a second Inverted-F antenna which resonates at a second band covering 2.4 GHz and 2.6 GHz corresponding to IEEE 802.11b/g and IEEE 802.16e respectively. 
         [0018]    The feeding point, the ground portion, the fourth radiating portion, and the connecting portion are formed as a third Inverted-F antenna which resonates at a third band covering 3.5 GHz corresponding to IEEE 802.16e. Therefore, the multi-band antenna can be operated at various wireless local area network frequency bands at the same time. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The present invention will be apparent to those skilled in the art by reading the following description of preferred embodiments thereof, with reference to the attached drawings, in which: 
           [0020]      FIG. 1  shows a first preferred embodiment of a multi-band antenna according to the present invention; 
           [0021]      FIG. 2  shows a second preferred embodiment of the multi-band antenna according to the present invention; and 
           [0022]      FIG. 3  shows a Voltage Standing Wave Ratio (VSWR) test chart of the multi-band antenna according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0023]    Please refer to  FIG. 1 . A first preferred embodiment of a multi-band antenna  100  is made of a metal foil. The multi-band antenna  100  has a feeding point  2 , a ground point  4 , a first radiating portion  6 , a second radiating portion  8 , a third radiating portion  10 , a fourth radiating portion  12  and a connecting portion  14 . 
         [0024]    The first radiating portion  6 , the second radiating portion  8 , the third radiating portion  10 , the fourth radiating portion  12  and the connecting portion  14  are arranged at one side of the ground portion  4 . The ground portion  4  is of a rectangular shape and extends in a first direction. The first radiating portion  6  is of a rectangular shape and extends in a second direction perpendicular to the first direction. 
         [0025]    The first radiating portion  6  defines opposite first end  16  and second end  18 , and opposite first side  20  and second side  22 . The first end  16  of the first radiating portion  6  is close to the ground portion  4 . The feeding point  2  is located at the first end  16  of the first radiating portion  6 . 
         [0026]    The second radiating portion  8  extends from the first side  20  of the second end  18  of first radiating portion  6  and has a first radiating section  24  and a second radiating section  26 . One end of the first radiating section  24  connects to the first side  20  of the second end  18  of the first radiating portion  6 , and the other end of the first radiating section  24  connects to the second radiating section  26 . 
         [0027]    Especially, the first radiating section  24  of the second radiating portion  8  extends in the first direction, and the second radiating section  26  extends in the second direction. The second radiating section  26  of the second radiating portion  8  is arranged to face to and close to the first radiating portion  6 . The free end of the second radiating section  26  is towards the ground portion  4 . The second radiating portion  8  is of a L shape. The second radiating portion  8  and the third radiating portion  10  are together formed as a L-shape. 
         [0028]    The third radiating portion  10  extends from the second side  22  of the second end  18  of the first radiating portion  6  and extends in the first direction. The third radiating portion  10 , the first radiating section  24  of the second radiating portion  8  and the second end  18  of the first radiating portion  6  are substantially at the same level. The fourth radiating portion  12  extends from the second side  22  of the first end  16  of the first radiating portion  6 , and is arranged between the ground portion  4  and the third radiating portion  10 . 
         [0029]    The fourth radiating portion  12  has a third radiating section  28 , a fourth radiating section  30  and a fifth radiating section  32 . The third radiating section  28  of the fourth radiating portion  10  extends in the first direction. The third radiating section  28  of the fourth radiating portion  10  is close to the ground portion  4 . One end of the third radiating section  28  connects to the second side  22  of the first end  16  of the first radiating portion  6 , and the other end of the third radiating section  28  connects to the fourth radiating section  30 . 
         [0030]    The fourth radiating section  30  extends in the second direction, and is arranged to face to and close to the first radiating portion  6 . The fourth radiating section  30  interconnects the third radiating section  28  and the fifth radiating section  32 . The fifth radiating section  32  extends in the first direction. The free end of the third radiating portion  10  and the free end of the fifth radiating section  32  are towards the same direction. Especially, the fourth radiating portion  12  is of a stair shape. 
         [0031]    The connecting portion  14  interconnects the fourth radiating portion  12  and the ground portion  4 . The connecting portion  14  has a first section  34  and a second section  26 . One end of the first section  34  of the connecting portion  14  connects to a corner defined by the third radiating section  28  and the fourth radiating section  30  of the fourth radiating portion  12 . The second section  36  interconnects the other end of the first section  34  and the ground portion  4 . 
         [0032]    Especially, the first section  34  extends in the first direction, and the second section  36  extends in the second direction. The first section  34  of the connecting portion  14  and the third radiating section  28  of the fourth radiating portion  12  are substantially at the same level. The first section  34  is close to the ground portion  4 . The connecting portion  14  is of a L shape. 
         [0033]    Especially, the ground portion  4 , the first radiating portion  6 , the second radiating portion  8 , the third radiating portion  10 , the fourth radiating portion  12  and the first section  34  of the connecting portion  14  are of an elongate shape. The second section  36  of the connecting portion  14  is of a rectangular shape. 
         [0034]    Please refer to  FIG. 2 . A second embodiment of a multi-band antenna  100  is printed on a circuit board  38 , such as a printed circuit board or a flex printed board. In this case, the ground portion  4 , the first radiating portion  6 , the second radiating portion  8 , the third radiating portion  10 , the fourth radiating portion  12  and the connecting portion  14  are printed on one surface of the circuit board  38 . 
         [0035]    Especially, the circuit board has plurality of through hole  40 . The fifth radiating section  32  of the fourth radiating portion has a curve  42  for avoiding the through hole  40 . The through hole  40  can engage with a corresponding engaging element for fixing the circuit board  38  to an electric device. 
         [0036]    The feeding point  2 , the ground portion  4 , the first radiating portion  6 , the second radiating portion  8 , the third radiating section  28  of the fourth radiating portion  12 , and the connecting portion  14  are formed as a first Inverted-F antenna. The cooperation of them resonates at a first band covering 5.2 GHz. The electronic length of the first radiating portion  6  and the second radiating portion  8  is a quarter wavelength corresponding to the first band. 
         [0037]    The feeding point  2 , the ground portion  4 , the first radiating portion  6 , the third radiating portion  10 , the third radiating section  28  of the fourth radiating portion  12 , and the connecting portion  14  are formed as a second Inverted-F antenna. The cooperation of them resonates at a second band covering 2.4 GHz and 2.6 GHz. The electronic length of the first radiating portion  6  and the third radiating portion  10  is a quarter wavelength corresponding to the second band. In the case of the first Inverted-F antenna and the second Inverted-F antenna, the third radiating section  28  of the fourth radiating portion  10  functions as a part of the connecting portion  14 . 
         [0038]    The feeding point  2 , the ground portion  4 , the fourth radiating portion  12 , and the connecting portion  14  are formed as a third Inverted-F antenna. The cooperation of them resonates at a third band covering 3.5 GHz. The electronic length of the fourth radiating portion  12  is a quarter wavelength corresponding to the third band. 
         [0039]    The connecting portion  14  functions as an inductance for tuning bandwidth of the second band, antenna matching and impedance. If the length of the connecting portion  14  is increased, then the value of the inductance will be therefore increased. Hence, the bandwidth of the second band is enhanced. 
         [0040]    The location of the fifth radiating section  32  of the fourth radiating portion  12  is related to the antenna gain of the second band and the third band. If the fifth radiating section  32  of the fourth radiating portion  12  is close to the third radiating portion  10 , then the Voltage Standing Wave Ratio (VSWR) of the second band will be raised, and the VSWR of the third band will be decreased. If the fifth radiating section  32  of the fourth radiating portion  12  is close to the ground portion  4 , then the Voltage Standing Wave Ratio (VSWR) of the second band will be decreased, and the VSWR of the third band will be raised. 
         [0041]    Please refer to  FIG. 3 , it shows a VSWR test chart of the multi-band antenna  100 . If the multi-band antenna  100  operates at 2.3 GHz, then the VSWR value will be 2.8497 (M 1  in  FIG. 3 ). If the multi-band antenna  100  operates at 2.7 GHz, then the VSWR value will be 2.6221 (M 2  in  FIG. 3 ). Therefore, the multi-band antenna  100  can stably operate at the second band covering 2.4 GHz corresponding to IEEE 802.11b/g and 2.6 GHz corresponding to IEEE 802.16e. 
         [0042]    If the multi-band antenna  100  operates at 3.3 GHz, then the VSWR value will be 1.8931 (M 3  in  FIG. 3 ). If the multi-band antenna  100  operates at 3.8 GHz, then the VSWR value will be 1.464 (M 4  in  FIG. 3 ). Therefore, the multi-band antenna  100  can stably operate at the third band covering 3.5 GHz corresponding to IEEE 802.16e. 
         [0043]    If the multi-band antenna  100  operates at 5.15 GHz, then the VSWR value will be 1.6213 (M 5  in  FIG. 3 ). If the multi-band antenna  100  operates at 5.85 GHz, then the VSWR value will be 1.1057 (M 6  in  FIG. 3 ). Therefore, the multi-band antenna  100  can stably operate at the first band covering 5.2 GHz corresponding to IEEE 802.11a. 
         [0044]    Therefore, the multi-band antenna  100  can operate at the first band covering 5.2 GHz corresponding IEEE 802.11a, the second band covering 2.4 GHz and 2.6 GHz corresponding IEEE 802.11b/g and IEEE 802.16e respectively, and the third band covering 3.5 GHz corresponding IEEE 802.16e. 
         [0045]    Furthermore, the present invention is not limited to the embodiments described above; diverse additions, alterations and the like may be made within the scope of the present invention by a person skilled in the art. For example, respective embodiments may be appropriately combined.