Patent Publication Number: US-8111195-B2

Title: Multi frequency antenna with low profile and improved grounding element

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an antenna, and more particularly to an multi-frequency antenna having wider range of frequency band. 
     2. Description of Prior Art 
     Wireless communication devices, such as cellular phones, notebook computers, electronic appliances, and the like, are normally equipped with an antenna for working in WLAN (Wireless Local Area Network) that serves as a medium for transmission and reception of electromagnetic signals, such as date, audio, image, and so on. However, more and more people dissatisfy their electronic devices only work in WLAN (Wireless Local Area Network). Making the portable electronic devices working in WWAN (Wireless Wide Area Network) or GPS (Global Positioning System) is a purpose of the many people. 
     In recent years, WLAN adopts two key technical standards of Bluetooth and Wi-Fi. Bluetooth works in 2.4 GHz, and Wi-Fi works in 2.4 GHz and 5 GHz. However, WWAN adopts three technical standards of GSM (Global System for Mobile Communication), GPS (Global Positioning System) and CDMA (Code Division Multiple Access). Operating frequency bands of the GSM are 900/1800 MHz, and operating frequency band of the GPS is 1.575 GHz. CDMA includes three kinds of technical standards: CDMA2000, WCDMA and TD-SCDMA. Operating frequency bands of the CDMA2000 are 800, 900, 1700, 1800, 1900, and 2100 MHz. Operating frequency bands of the WCDMA are 1800, 1900, and 2100 MHz. Operating frequency bands of the TD-SCDMA are 900, 1800, and 2100 MHz. 
     Taiwanese patent No. 1254493 discloses a multi-band antenna including two radiating elements for working 1800 MHz frequency band and 900 MHz frequency band. 
     However, the multi-band antenna has narrower range of frequency band, and is not capable to cover all frequency bands of WWAN. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a multi-frequency antenna which has wide range of frequency band. 
     To achieve the aforementioned object, the present invention provides a multi-frequency antenna comprising: a radiating patch having a first radiating element and a second radiating element; a grounding patch spaced apart from the radiating patch; a connecting element comprising a first connecting arm and a second connecting arm; a feeding line comprising an inner conductor and an outer conductor; wherein the first connecting arm connecting to the radiating patch and the second connecting arm connecting to the grounding patch; the first connecting arm locating in a first plane is perpendicular to the second connecting arm locating in a second plane. 
     Additional novel features and advantages of the present invention will become apparent by reference to the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a multi-frequency antenna in accordance with a preferred embodiment of the present invention; 
         FIG. 2  is a view similar to  FIG. 1 , but from a different aspect; and 
         FIG. 3  is a test chart recording for the multi-frequency antenna in accordance with a preferred embodiment of the present invention, showing Voltage Standing Wave Ratio (VSWR) as a function of WWAN frequency. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the preferred embodiment of the present invention. 
     Referring to  FIGS. 1 and 2 , a multi-frequency antenna  100  in accordance with a first embodiment of the present invention comprises a radiating patch  20 , a grounding patch  10  spaced apart from the radiating patch  20 , a connecting element  30  connecting the radiating patch  20  and the grounding patch  10 , a coupling radiating element  25 , and a feeding line  5 . 
     The grounding patch  10  comprises a horizontal grounding element  12  and a vertical grounding element  11  perpendicularly connecting to the horizontal grounding element  12 . The horizontal grounding element  12  is rectangle and narrow. One tail end of the horizontal grounding element  12  is triangle-shape. The vertical grounding element  11  has two installing hole  70  for a screw (not shown) through to installing the multi-frequency antenna  100  onto a cover of the portable electronic device (not shown). The horizontal grounding element  12  has a through hole  80  for the feeding line  5  through. 
     The connecting element  30  having triangle-shape comprises a first connecting arm  31  and a second connecting arm  32  extending from an end of the first connecting arm  31 . The first connecting arm  31  and the horizontal grounding element  12  form a sharp angle. The first connecting arm  31  and the second connecting arm  32  form an obtuse angle. 
     The radiating patch  20  comprises a first radiating-element extending from the middle of the second connecting arm  32 , a second radiating element  22  and a third radiating element  23  extending from an end of the first radiating element  21  to opposite directions, and a fourth radiating element  24  extending from an end of the second connecting arm  32 . The first radiating element  21  has rectangle-shape. The first radiating element  21  is wider than the second radiating element  22 , the third radiating element  23 , and the fourth radiating element  24 . The second radiating element  22  having “U” shape comprises a first radiating branch  221 , a second radiating branch  222  extending vertically from an end of the first radiating branch  221 , and a third radiating branch  223  extending from an edge of an end of the second radiating branch  222  to the first radiating branch  221 . The third radiating element  23  comprises a fourth radiating branch  231  locating in a common beeline with the first radiating branch  221  and a fifth radiating branch  232  extending vertically from an end of the fourth radiating branch  231 . The fourth radiating element  24  having “L” shape locates in a common plane with the first radiating element  21 . The fourth radiating element  24  comprises a shorter vertical part and a longer horizontal part. The coupling radiating element  25  comprises a first radiating arm  251  extending vertically from the middle of the horizontal grounding element  12  and a second radiating arm  252  extending an end of the first radiating arm  251  and paralleling to the horizontal grounding element  12 . The second radiating arm  252  having L-shape is longer than the first radiating arm  251 . 
     The feeding line  50  comprises an inner conductor  51 , an inner insulating layer  52 , an outer conductor  53  electrically connecting to the horizontal grounding element  12 , and an outer insulating layer  54 . The inner conductor  51  electrically connects to a joint point P of the fourth radiating element  24  and the connecting element  30 . 
     The first radiating element  21  and the second radiating element  22  form a first radiating body operating in lower frequency band of the WWAN. The first radiating element  21  and the third radiating element  23  form a second radiating body operating in higher frequency band of the WWAN. The length of the fourth radiating element  24  is about equal to the second radiating body. Accordingly, the fourth radiating element  24  is capable to widen the higher frequency band of the WWAN. The length of the coupling radiating element  25  is about equal to the second radiating body. Accordingly, the coupling radiating element  25  is capable to widen the higher frequency band of the WWAN. 
     The multi-frequency antenna  100  has lower profile because of the connecting element  30  and the horizontal grounding element  12  being coplanar. The connecting element  30  extends from a tip of the triangular end of the grounding element  12 , accordingly, the length of the multi-frequency antenna  100  is shorter than traditional antenna. If the connecting element  300  extends from a middle portion of the grounding patch as traditional antenna, the multi-frequency antenna  100  will be prolonged due to the length of the fourth radiating element  24  being changeless. 
       FIG. 3  is a test chart of Voltage Standing Wave Ratio of the multi-frequency antenna  100 . Referring to  FIG. 3 , operating frequency band of the multi-frequency antenna  100  are 840 MHz-920 MHz and 1680 MHz-2230 MHz. Above-mentioned operating frequency band has covered all of the frequency bands of the WWAN.