Abstract:
A multi-band antenna includes a radiating element having at least two frequency bands and comprising a gap on one side edge thereof, a grounding element coupling and being perpendicular to said radiating element, and a reactance assembled to said radiating element and received in said gap.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a multi-band antenna, and more particularly to a multi-band antenna used for electronic devices, such as notebooks. 
     2. Description of the Prior Art 
     With the high-speed development of the mobile communication, people more and more expect to use a computer or other portable terminals to optionally connect to Internet. GPRS (General Packer Radio Service) and WLAN (Wireless Local Area Network) allow users to access data wirelessly over both cellular networks and 802.11b WLAN system. When operating in GPRS, the data transmitting speed is up to 30 Kbps˜50 Kbps, while when connected to a WLAN access point, the data transmitting speed is up to 11 Mbps. People can select different PC cards and cooperate with the portable terminals such as the notebook computer or the like to optionally connect to Internet. Since WLAN has a higher transmitting speed, WLAN is usually used to provide public WLAN high-speed data services in some hot areas (for example, hotel, airport, coffee bar, commerce heartland, conference heartland and etc.). When leaving from these hot areas, network connection is automatically switched to GPRS. 
     As it is known to all, an antenna plays an important role in wireless communication. As a result, the PC card may choose individual antennas to respectively operate at WWAN (Wireless Wide Area Network), namely GPRS, and WLAN. It arises a hot problem to integrate two individual antennas in a limited space to go along with the miniaturization of portal devices. Please refer to  FIG. 1 , a multi-band antenna  10 ′ comprises a first type of antenna which is used in WWAN and has first and second antennas  1 ′,  2 ′ and a second type of antenna which is used in WLAN and has third and fourth antennas  3 ′,  4 ′. The multi-band antenna  10 ′ is integrally made from a metal sheet and integrates the first type of antenna for WWAN and the second type antenna for WLAN together. However, with the two types of antennas integration, the interference therebetween will become greater, and owing to this structure, the multi-band antenna  10 ′ can not achieve desired bandwidth. TW pat. No. 253070 discloses a wide band antenna. As shown in FIG. 2 of TW Pat. No. 253070, the wide band antenna has a gap  30  formed by cutting the radiating portion  24  of the antenna and an inductance is soldered on the position of the gap  30 , so that the radiating portion  24  of the antenna become an integer. However, the method of soldering a reactance on an antenna is difficult to achieve except the antenna is arranged on a PCB. In present removable devices, one most popular antenna, PIFA antenna for short, is used widely. Because of the lack of the supporting from a PCB, said means of assembling a reactance don&#39;t conform to this kind of antenna. 
     Hence, an improved antenna is desired to overcome the above-mentioned shortcomings of the existing antennas. 
     BRIEF SUMMARY OF THE INVENTION 
     A primary object, therefore, of the present invention is to provide a multi-band antenna used in WWAN and WLAN with simple structure to achieve a good impedance, and the antenna has low cost and easy manufacture. 
     In order to implement the above object and overcomes the above-identified deficiencies in the prior art, the multi-band antenna comprises a radiating element having at least two frequency bands and comprising a gap on one side edge thereof, a grounding element, a reactance, wherein the reactance is assembled on said gap to be received in. 
     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 
         FIG. 1  is a perspective view illustrating a conventional multi-band antenna; 
         FIG. 2  is a perspective view of a multi-band antenna according to a preferred embodiment of the present invention; 
         FIG. 3  is a view similar to  FIG. 2 , but take from a different aspect; 
         FIG. 4  is an exploded, perspective view of the multi-band antenna of  FIG. 3 ; and 
         FIG. 5  is a test chart recording of Voltage Standing Wave Ratio (VSWR) of the multi-band antenna with reactance and without reactance as a function of frequency. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to a preferred embodiment of the present invention. 
     Reference to  FIG. 2  to  FIG. 4 , a perspective view of a multi-band antenna  1  in accordance with a preferred embodiment of the present invention is shown. The multi-band antenna  1  consists of an antenna body  100 , an insulative member  200  affixed to the antenna body  100 , a metal foil  300  and a reactance  400  soldered on the antenna body  100 . The multi-band antenna  1  also comprises a first antenna  2  used in WWAN, a second antenna  3  used in WLAN, a grounding element  6  integrally formed with the first antenna  2  and the second antenna  3 , and a pair of fitting elements  4 ,  5  for mounting the multi-band antenna  1  to an electronic device. In this embodiment, the insulative member  200 , the metal foil  300  and the reactance  400  are all on the first antenna  2 . The antenna body  100  of the multi-band antenna  1  is made of a metal patch with a pressing means, which combine a WWAN antenna and a WLAN antenna. The grounding element  6  comprises a first grounding portion  61 , an L-shape metal patch  62  extending upwardly from the middle area of the first grounding portion  61 , and a metal patch  63  with interrupted shape. 
     The first antenna  2  comprises a radiating element  21 , a grounding element  6 , a connecting portion  22  connecting the radiating element  21  and the grounding element  6  and a protrusion  23  extending from the connecting portion  22  to connect a feeding line (not shown). The radiating element  21  is separated from and parallel to the grounding element  6 , and the radiating element  21  and are located on the same side of the connecting portion  22 . The radiating element  21  comprises a high-frequency radiating portion  210  and a low-frequency radiating portion  212 . The high-frequency radiating portion  210  comprises a first radiating arm  2101  having a triangle-shape notch  2101   a  and a second radiating arm  2102  bending from the first radiating arm  2101  to the grounding element  6 . The low-frequency radiating portion  212  is a metal patch with interrupted shape like an “L”. The low-frequency radiating portion  212  comprises a first end  2120  connecting with the high-frequency radiating portion  210  and a second end  2122  opposite to the first end  2120  with a narrower width than that of the first end  2120 . A gap  2121  is defined by the first end  2120  by cutting itself on one side thereof to receive the reactance  400 . The insulative member  200  and the metal foil  300  are plastered to the second end  2122 . In this embodiment, the insulative member  200  comprises a rectangle main body  201 , a rib  202  extending from the joint of the upper surface  201   a  and the side  201   c  of the main body  201 , and a bar  203  extending from the joint of the lower surface  201   b  and the side  201   c  of the main body  201 . The side  201   c , the rib  202  and the bar  203  constitute a cavity (not labeled). The upper surface  201   a  of the main body  201  is plastered on the surface, opposite to the grounding element  6 , of the low-frequency radiating portion  212  of the first antenna  2 . The side  201   c  is adjacent to the second antenna  3 . The second antenna  3  is partially received in the cavity defined by the upper surface  201   a , the rib  202  and the bar  203 . The metal foil  300  is inverted-U shape, and plastered to the low-frequency radiating portion  202  to enclose the insulative member  200 . The metal foil  3  comprises an upper wall  301 , a lower wall  302  and a side wall  303 . The metal foil  300  opens toward the second antenna  3 . The upper wall  301  is fixed on the surface, facing to the grounding element  6 , of the first antenna  2 . The side wall  303  cover the side, opposite to the side  201   c , of the insulative member  200 . The lower wall  302  is plastered to the lower surface  201   b  of the insulative member  200 . The metal foil  300  never touches the second antenna  3 . The metal foil  300  induces the area of the low-frequency radiating portion  212  of the second antenna rather than the length of the low-frequency radiating portion  212 , and then the band width of the low-frequency radiating portion  212  increases. To reduce the interference between the first antenna  2  and the second antenna  3 , a certain distance is needed therebetween. So the shape of the insulative member  200  is designed to fasten the first antenna  2  and the second antenna  3  together while still keeps the certain distance to reduce the interference between the first antenna  2  and the second antenna  3 . At the same time, the insulative member  200  supports the metal foil  300 . In alternative embodiment, the location site and shape of the insulative member  200  can be changed if needed. The reactance  400  locates in the gap  2121  of the low-frequency radiating portion  212  and defines a tinned area on its surface to solder itself on the low-frequency radiating portion  212 . The reactance  400  can be assembled on the other radiating portion, such as the high-frequency radiating portion  210 . The reactance  400  can be not only a Multi Layer Ceramic Capacitor but also a Multi Layer Ceramic Inductance. The protrusion  23  extends from a point M on the connecting portion  22  along the direction parallel to the grounding element  6 . The protrusion  23  is located on the same side of the connecting portion  22  same as the grounding element  6 . 
     The high-frequency radiating portion  210  is on a first plane same as the low-frequency radiating portion  212  of the first antenna  2 . The connecting portion  22 , extends from the joint of the high-frequency radiating portion  210  and the low-frequency radiating portion  212 , is Z shape and on a second plane perpendicular to the first plane. The connecting portion  22  connects the high-frequency radiating portion  210  and the low-frequency radiating portion  212  on a point Q. The gap  2121  of the low-frequency radiating portion  212  is adjacent to the point Q, while the triangle gap  2101   a  is located on a side of the high-frequency radiating portion  210  opposite to the point Q. 
     The second antenna  3  comprises a radiating element  31 , a grounding element  6 , a connecting portion  32  connecting the radiating element  31  and the grounding element  6 , and a heave  33  connecting a feeding line (not shown). The radiating element  31  comprises a high-frequency radiating portion  310 , a low-frequency radiating portion  312 , a third radiating portion  314  and a common arm  3102  shared by the high-frequency radiating portion  310  and the low-frequency radiating portion  312  together. The common arm  3102  is perpendicular to the high-frequency radiating portion  310  and the low-frequency radiating portion  312 . The high-frequency radiating portion  310  also comprises a lengthwise radiating arm  3101 , and the low-frequency radiating portion  312  comprises a second radiating arm  3122 , Z shaped, extending along a direction reverse to the lengthwise radiating arm  3101 . The third radiating portion  314  connects the common radiating arm  3102  and the connecting portion  32  on a point P together. The radiating element  31  of the second antenna  3  is located on a plane same as the connecting portion  32 , and on the same side of the grounding element  6  as the radiating element  21  and the connecting portion  22  of the first antenna  2 . 
     In this embodiment of the present invention, the high-frequency radiating portion  210  of the first antenna  2  is used to receive and send the high frequency signal on 1800-1900 MHz, and the low-frequency radiating portion  212  is used to receive and send the low frequency signal on 900 MHz. The high-frequency radiating portion  310  of the second antenna  3  is used to receive and send the high frequency signal on 5 GHz, and the low-frequency radiating portion  312  is used to receive and send the low frequency signal on 2.4 GHz. The low-frequency radiating portion  212  of the first antenna  2  is adjacent to the low-frequency radiating portion  312  of the second antenna  3 . It&#39;s known that the radiating performance is greatly influenced by the impedance. In this embodiment, the first antenna  2  has small volume compared with conventional antenna while still has substantially same frequency and bandwidth because the aid of the insulative member  200  and the metal foil  300 . In addition, the existence of the reactance  400  regulates the impedance to increase the power of the low-frequency radiating portion  212 .  FIG. 5  illustrates two gain curves of the first antenna  2  with the reactance  400  and without the reactance  400 . The gain increases 2 dBi when the reactance  400  is imported. Therefore, the antenna assembled reactance achieves good performance. Besides the excellent performance mentioned above, this method of assembling a reactance to the radiating element of the antenna of this embodiment has a simple manufacture process and low cost. In other embodiment, the reactance  400  can be assembled on different positions of different antennas in need. 
     While the foregoing description includes details which will enable those skilled in the art to practice the invention, it should be recognized that the description is illustrative in nature and that many modifications and variations thereof will be apparent to those skilled in the art having the benefit of these teachings. It is accordingly intended that the invention herein be defined solely by the claims appended hereto and that the claims be interpreted as broadly as permitted by the prior art.