Patent Publication Number: US-2007120749-A1

Title: Portable electronic device with a slot antenna

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application claims priority of Taiwanese application no. 094142082, filed on Nov. 30, 2005.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This invention relates to a portable electronic device, more particularly to a portable electronic device that includes a slot antenna.  
      2. Description of the Related Art  
       FIG. 1  illustrates a conventional portable electronic device  1  that includes a casing  11 , a circuit board  10 , and a planar inverted-F antenna (PIFA)  12 . The casing  11  is made from metal (or coated with a metal-containing painting), and confines an accommodating space. The circuit board  10  is disposed in the accommodating space. The PIFA  12  is disposed in the accommodating space, is coupled electrically to the circuit board  10 , and is operable within the 2.4 GHz to 2.5 GHz Industrial, Scientific, and Medical (ISM) band.  
      Based from experimental results, the PIFA  12  of the conventional portable electronic device  1  has antenna gains of −1 dBi, −0.7 dBi, and −1.2 dBi when operated at 2.4 GHz, 2.45 GHz, and 2.5 GHz, respectively.  
      The aforementioned conventional portable electronic device  1  is disadvantageous in that, since the casing  11  is made from metal, which is the current trend in portable electronic devices, the antenna gain of the PIFA  12  is considerably deteriorated.  
      It has been proposed heretofore to replace a portion  111  of the casing  11 , which is proximate to the PIFA  12 , with a non-metallic material, such as plastics, to solve the above problem. This, however, results in a complex manufacturing process for the casing  11  and has an adverse effect on the appearance of the casing  11 .  
     SUMMARY OF THE INVENTION  
      Therefore, the object of the present invention is to provide a portable electronic device that can overcome the aforesaid drawbacks of the prior art.  
      According to the present invention, a portable electronic device comprises a metallic casing, a circuit board, a feeding line, and a grounding line. The metallic casing confines an accommodating space, and is formed with a slot that is in spatial communication with the accommodating space and that is defined by a slot-defining wall. The circuit board is disposed in the accommodating space, and is provided with feeding and grounding ports. The feeding line serves to couple electrically the feeding port to the slot-defining wall. The grounding line serves to couple electrically the grounding port to the slot-defining wall. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment with reference to the accompanying drawings, of which:  
       FIG. 1  is a perspective view of a conventional portable electronic device with a planar inverted-F antenna;  
       FIG. 2  is a perspective view of the first preferred embodiment of a portable electronic device with a slot antenna according to the present invention;  
       FIG. 3  is a schematic partly cutaway view to illustrate the slot antenna of the preferred embodiment;  
       FIG. 4  is a plot illustrating a voltage standing wave ratio of the slot antenna of the preferred embodiment;  
       FIG. 5  is a perspective view of the second preferred embodiment of a portable electronic device with a slot antenna according to the present invention; and  
       FIG. 6  is a perspective view of the third preferred embodiment of a portable electronic device with a slot antenna according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Before the present invention is described in greater detail, it should be noted that like elements are denoted by the same reference numerals throughout the disclosure.  
      Referring to  FIGS. 2 and 3 , the first preferred embodiment of a portable electronic device  2  according to this invention is shown to include a metallic casing  22 , a circuit board  21 , a feeding line  23 , and a grounding line  24 .  
      In this embodiment, the portable electronic device  2  is in the form of a mobile phone.  
      The portable electronic device  2  of this embodiment is capable of connecting with other electronic devices (not shown) through Bluetooth or Wi-Fi technologies, in a manner that will be described hereinafter.  
      The casing  22  confines an accommodating space  220 , and is formed with a slot  221  that is in spatial communication with the accommodating space  220  and that is defined by a slot-defining wall  223 . In this embodiment, the slot-defining wall  223  is generally rectangular in shape, and has a longer wall surface  2231 , and a shorter wall surface  2232 , which has a length shorter than that of the longer wall surface  2231 .  
      The casing  22  and the slot  221  cooperatively constitute a slot antenna for operation within the 2.4 GHz to 2.5 GHz Industrial, Scientific, and Medical (ISM) band.  
      The circuit board  21  is disposed in the accommodating space  220 , and is provided with feeding and grounding ports  211 ,  212 .  
      The feeding line  24  couples electrically the feeding port  211  to a first connecting point  25  that is provided on the shorter wall surface  2232  of the slot-defining wall  223 .  
      The grounding line  23  couples electrically the grounding port  212  to a second connecting point  26  that is spaced apart from the first connecting point  25  and that is provided on the shorter wall surface  2232  of the slot-defining wall  223 .  
      In this embodiment, each of the feeding and grounding lines  24 ,  23  is a micro strip line. In an alternative embodiment, each of the feeding and grounding lines  24 ,  23  is a conductive lead.  
      Based from experimental results, as illustrated in  FIG. 4 , the slot antenna of the portable electronic device  2  of this invention achieves a voltage standing wave ratio (VSWR) of 1.7 when operated at 2.45 GHz. Moreover, the slot antenna of the portable electronic device  2  of this invention has antenna gains of 0.8 dBi, 1.5 dBi, and 0.5 dBi when operated at 2.4 GHz, 2.45 GHz, and 2.5 GHz, respectively.  
      By forming the casing  22  of the portable electronic device  2  of this invention into a slot antenna, the aforesaid drawbacks associated with the prior art can be eliminated.  
       FIG. 5  illustrates the second preferred embodiment of a portable electronic device  2 ′ according to this invention. In this embodiment, the portable electronic device  2 ′ is in the form of a personal digital assistant.  
       FIG. 6  illustrates the third preferred embodiment of a portable electronic device  2 ″ according to this invention. In this embodiment, the portable electronic device  2 ″ is in the form of a notebook computer.  
      While the present invention has been described in connection with what is considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.