Abstract:
A multi-band antenna adapted for used in a portable electronic device, includes: a first antenna including a first radiating element, a common grounding element, and a first connecting element connecting the first radiating element and the common grounding element; a second antenna, including a first radiating portion, the common grounding element, and a second connecting element connecting the radiating portion and the grounding element. Free end portions of the first radiating element and the first radiating portion do not align with each other in any direction.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to an antenna, and more particularly to a multi-band antenna used in a portable electronic device, such as a notebook. 
   2. Description of the Prior Art 
   With the development of wireless communication, more and more people hope to own portable electronic devices, such as a notebook, capable of connecting to Internet. The systems of the WLAN (Wireless Local-area Network) and the GPRS (General Packer Radio Service) can make the portable electronic devices, such as a notebook, work in Internet. The GPRS is a wide-area network and the data transfer speed thereof is 30 Kbps˜50 Kbps. The WLAN is a local-area network and the data transfer speed is 11 Mbps. The portable electronic device, such as a notebook can choose different Wireless cards for jointing to Internet. 
   At present, the WLAN is based on Bluetooth technology standard or IEEE802.11 series technology standard. The frequency band of an antenna is 2.4 GHz and 5 GHz in IEEE802.11 series technology standard, but is 900 Mhz, 1800 MHz and 1900 MHz in GPRS technology standard. So, most antennas used in the notebooks work at the above-mentioned frequency bands in recent years. 
   PIFA (Planar Inverted-F Antenna) is a kind of minitype antenna usually used in a portable electronic device, such as a notebook. PIFA has compact structure, light weight, perfect impedance match, desired horizontal polarization and vertical polarization, and is easy to achieve multi-bands. So, more and more PIFAs are used in the portable electronic devices. 
   IEEE802.11 series technology standard comprises IEEE802.11a, IEEE802.11b and other different technology standards. The corresponding frequencies are different because of the different technology standards. So, PIFA usually has two radiating elements for providing two different frequencies. 
   The two different frequencies of the PIFA basically satisfy the requirements of the frequency band, while the radiating field usually has blind field making the signal not being radiated in some directions because of the characteristics of the two frequencies of the PIFA. 
   In the prior art, two same PIFAs being mirror image arranged to consist a PIFA system decrease radiating blind field. However, because the two PIFAs are mirror image arranged, a pair of radiating element ends of providing common frequency are mirror image arranged too, the PIFA system cannot distinguish which PIFA being a primary antenna and which being a secondary antenna, thus making the PIFA system occurring self-excitation. The self-excitation influences the natural work of the PIFA system. The radiating fields of the two mirror image arranged radiating elements occur superposition and radiating blind field. 
   Hence, in this art, a multi-band antenna to overcome the above-mentioned disadvantages of the prior art will be described in detail in the following embodiment. 
   BRIEF SUMMARY OF THE INVENTION 
   A primary object, therefore, of the present invention is to provide a multi-band antenna which can avoid self-excitation and fetch up radiating blind field. 
   In order to implement the above object and overcome the above-identified deficiencies in the prior art, a multi-band antenna adapted for used in a portable electronic device, comprising: a first antenna comprising a radiating element comprising a first radiating element, a grounding element, and a first connecting element connecting the radiating element and the grounding element; a second antenna comprising a radiating portion comprising a first radiating portion, the grounding element share with the first antenna, and a second connecting element connecting the radiating portion and the grounding element; wherein the free ends of the first radiating element and the first radiating portion locate on different lines. 
   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 of a preferred embodiment of a multi-band antenna in accordance with the present invention; and 
       FIG. 2  is a perspective view similar to  FIG. 1 , but take from a different direction. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Reference will now be made in detail to a preferred embodiment of the present invention. 
   Referring to  FIG. 1  and  FIG. 2 , a multi-band antenna  10  according to the preferred embodiment of the present invention is stamped and bent from a metal patch. The multi-band antenna  10  comprises a first antenna  1  and a second antenna. The first antenna  1  comprises a first radiating element  11 , a second radiating element  12 , a third radiating element  13 , a first feeding cap  14 , a first connecting element  15 , a grounding element  16 , and a first feeding line (not shown). The first radiating element  11  operates at 2.4 GHz of lower frequency band of IEEE802.1 a standard. The second radiating element  12  operates at 5 GHz of higher frequency band of IEEE802.11b/g. The third radiating element  13  is complementarity to the second radiating element  12  and enhances frequency band of the higher frequency. The second antenna  2  comprises a first radiating portion  21 , a second radiating portion  22 , a third radiating portion  23 , a second feeding cap  24 , a second connecting element  25 , the common grounding element  16  sharing with the first antenna  1  and a second feeding line (not shown). 
   The first radiating element  11  comprises a first radiating arm  111  partaking with the second radiating element  12 , a second radiating arm  112  perpendicularly extending from one end of the first radiating arm  111 , a third radiating arm  113  being coplanar with the second arm  112  and located at different beelines, and a fourth radiating arm  114  connecting the second radiating arm  112  and the third radiating arm  113 . The third radiating arm  113  and the fourth radiating arm  114  together form an L-shape. The second radiating element  12  comprises a fifth radiating arm  115  extending from one end of the first radiating arm  111  and located in the common beeline with the second radiating arm  112  extending along an opposite direction. The third radiating element  13  perpendicularly extends from the other end of the first radiating arm  111  and is parallel to the fifth radiating arm  115 . 
   The first feeding cap  14  is a rectangular sheet and perpendicularly extends from the joint of the third radiating element  13  and the first radiating arm  111 . The First feeding line comprises an inner conductor soldering at the first feeding cap  14  and an outer conductor soldering at the grounding element  16 . 
   The grounding element  16  comprises a smaller first grounding plane  161  being coplanar with the three radiating elements  11 ,  12 ,  13  of the first antenna  1  and a bigger second grounding plane  162  perpendicular to the first grounding plane  161 . A rectangular gap  17  is formed at a middle portion of the first grounding plane  161  for avoiding the third radiating arm  113  and the fourth radiating arm  114  extending and contacting the first grounding plane  161 . Two longitudinal ends of the second grounding plane  162  each have an installing section  3  coplanar with the first grounding plane  161 . The installing section  3  has an installing hole  30  for locking the multi-band antenna  10  on a portable electronic device, such as a notebook. 
   The first connecting element  15  extends from one end of the first grounding plane  161  connecting to the joint of the third radiating element  13  and the first radiating arm  111 . 
   The first radiating element  11 , the second radiating element  12 , the third radiating element  13 , the first connecting element  15 , and the first grounding plane  161  are coplanar. 
   The first radiating portion  21  of the second antenna  2  operates at 2.4 GHz of a lower frequency band of the IEEE802.1 a technology standard. The second radiating portion  22  operates at 5 GHz of a higher frequency band of the IEEE802.11b/g technology standard. The third radiating portion  23  is complementarity to the second radiating portion  22  and enhances frequency band of the higher frequency. 
   The first radiating portion  21  comprises a first radiating branch  211 , a second radiating branch  212  extending perpendicularly from one end of the first radiating branch  211  and being coplanar with the first radiating branch  211 , a third radiating branch  213  extending from one end of the second radiating branch  212  and perpendicular to the plane in which the second radiating branch  212  is located. The third radiating branch  213  of the second antenna  2  and the first radiating arm  11  of the first antenna  1  are not coplanar. The second radiating branch  212  and the third radiating branch  213  together form an L-shape structure. The second radiating portion  22  comprises the common first radiating branch  211  sharing with the first radiating portion  21  and a fourth radiating branch  214  extending perpendicularly from one end of the first radiating branch  211  to an opposition direction compared with the second radiating branch  212 . 
   The second connecting element  25  extends from the other end of the first grounding plane  161  to a joint of the third radiating portion  23  and the first radiating branch  211 . The second connecting element  25  and third radiating portion  23  locate on one common line. 
   The second feeding cap  24  is a rectangular sheet and perpendicularly extends from the joint of the third radiating portion  23  and the first radiating branch  211 . The First feeding line comprises an inner conductor soldering at the second feeding cap  24  and an outer conductor soldering at the grounding element  16 . 
   The first radiating element  11  and the first radiating portion  21  operate at the same frequency, two free end portions of the first radiating element  11  and the first radiating portion  21  locate in different planes and are not arranged in a line because of the above design of the first radiating element  11  of the first antenna  1  and the first radiating portion  21  of the second antenna  2 . The radiating field of the first antenna  1  and the second antenna  2  are not overlapped because of above design. The antenna module (not shown) connecting to the multi-band antenna  10  is easy to distinguish which is the main antenna and which is the secondary antenna for avoiding the multi-band antenna  10  occurring self-excitation. The secondary antenna can fully fetch up radiating blind field of the main antenna and the multi-band antenna  10  has better radiating performance of the lower frequency. 
   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.