Patent Publication Number: US-7916093-B2

Title: Multiband antenna

Description:
TECHNICAL FIELD 
     The present invention relates to antennas, and particularly to a multiband antenna. 
     DESCRIPTION OF THE RELATED ART 
     Antennas are usually designed to work with a particular wireless access technology in mind. Cellular telephones, for example, contain antennas that are used to handle radio-frequency communications with cellular base stations. Handheld computers often include short-range antennas for handling wireless connections with wireless access points. Global positioning system (GPS) devices typically contain antennas that are designed to operate at GPS frequencies. 
     Thus, in order to operate with multiband signals, electronic devices usually must include a number of antennas to accommodate different frequencies. However, as the number of antennas increases this may limit the miniaturization of the electronic device. 
     What is needed, therefore, is a multiband antenna to overcome the above-described problem. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present multiband antenna can be better understood with references to the accompanying drawings. The components in the drawing are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present multiband antenna. 
         FIG. 1  is a schematic plan view of a multiband antenna according to a first exemplary embodiment. 
         FIG. 2  is a schematic diagram showing the return loss versus frequency characteristic of the multiband antenna of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Embodiments of the present invention will now be described in detail below, with references to the accompanying drawings. 
     Referring to  FIG. 1 , a multiband antenna  100  according to an exemplary embodiment is shown. The multiband antenna  100  includes a conductive sheet  10  defining a slot structure  20 , a feeding point  30 , and a grounding point  40 . 
     The conductive sheet  10  can be a metal sheet or a circuit board. In the present embodiment, the conductive sheet  10  is a metal sheet. The slot structure  20  can be formed on the conductive sheet  10  by punching. If the conductive sheet  10  is a circuit board the slot structure  20  can be formed on the conductive sheet  10  by etching. 
     The slot structure  20  includes a first slot  210 , a second slot  220 , a third slot  230 , a fourth slot  240 , a fifth slot  250 , a sixth slot  260 , and a seventh slot  270 . In the present embodiment, all of the above slots are rectangular. Each of the slots has two opposite short sides and two opposite long sides longer than the short sides. 
     The second slot  220  and the third slot  230  extend from a same short side of the first slot  210  and are parallel to each other. The short sides of the second slot  220  and the third slot  230  are parallel to the short sides of the first slot  210 . The fourth slot  240 , the fifth slot  250 , the sixth slot  260 , and the seventh slot  270  extend from a short side of the third slot  230  and away from the first slot  210  in sequence. The fourth slot  240 , the fifth slot  250 , the sixth slot  260 , and the seventh slot  270  are curved inwards and extend perpendicular to the third slot  230 , the fourth slot  240 , the fifth slot  250 , and the sixth slot  260 , respectively. The third slot  230  and the fifth slot  250  are at the same side as the fourth slot  240 , the fourth slot  240  and the sixth slot  260  are at the same side as the fifth slot  250 , and the fifth slot  250  and the seventh slot  270  are at the same side as the sixth slot  260 . 
     In the present embodiment, the length of the first slot  210  is approximately 20 mm and the width is approximately 5 mm. The length of the second slot  220  is approximately 30 mm and the width is approximately 2 mm. The size of the third slot  230  is the same as that of the second slot  220 . The widths of the fourth slot  240 , the fifth slot  250 , the sixth slot  260 , and the seventh slot  270  are 1 mm. The lengths of the fourth slot  240 , the fifth slot  250 , the sixth slot  260 , and the seventh slot  270  are 8 mm, 20 mm, 3 mm, and 8 mm, respectively. The distance between the second slot  220  and the third slot  230  is approximately 1 mm. 
     The feeding point  30  is formed on the conductive sheet  10  at a long side of the first slot  210  away from the third slot  230 . In the present embodiment, the distance from the feeding point  30  to the short side of the first slot  210  away from the third slot  230  is approximately 8.5 mm. 
     The grounding point  40  is formed on the conductive sheet  10  at a margin of the slot structure  20  different from the location of the feeding point  30 . 
     In the present embodiment, the first slot  210  and the second slot  220  as a whole is capable of operating under a first frequency band for receiving or radiating Institute of Electrical and Electronics Engineers, Inc. (IEEE) 802.11 wireless standard (802.11) signals. The first slot  210 , the third slot  230 , the fourth slot  240 , the fifth slot  250 , the sixth slot  260 , and the seventh slot  270  as a whole is capable of operating under a second frequency band for receiving or radiating GPS signals. Referring to  FIG. 2 , the antenna  100  achieves a return loss smaller than −10 dB at approximately 1.575 GHz, which is the second frequency band for receiving or radiating GPS signals. The antenna  100  achieves a return loss smaller than −20 dB at approximately 2.5 GHz, which is the first frequency band for receiving or radiating IEEE 802.11 signals. Moreover, the antenna  100  can operate under two frequency bands for receiving or radiating IEEE 802.11 and GPS signals. 
     While certain embodiments have been described and exemplified above, various other embodiments will be apparent to those skilled in the art from the foregoing disclosure. The present invention is not limited to the particular embodiments described and exemplified, and the embodiments are capable of considerable variation and modification without departure from the scope of the appended claims.