Patent Publication Number: US-8125395-B2

Title: Multi-band antenna

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a multi-band antenna, and particularly to a multi-band antenna with a compact structure adapted for being mounted in a portable electronic device. 
     2. The Related Art 
     With the development of wireless communication, more and more portable electronic devices, such as a notebook, install an antenna for working in a Wireless Wide Network (WWAN), such as GSM850 (Global System for Mobile communications), GSM900 (Global System for Mobile communications), DCS (Digital Cellular System), PCS (Personal Conferencing Specification) and WCDMA (Wideband Code Division Multiple Access). However, a conventional antenna generally has a big size for meeting a requirement of multiple frequency bands which is against miniaturization trend of the portable electronic device. So it is necessary to design an antenna with a simple and compact structure capable of covering above-mentioned frequency bands synchronously. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a multi-band antenna with a compact structure capable of being mounted in a portable electronic device. 
     The multi-band antenna has an elongated grounding plate disposed vertically with a top edge defined thereon. Two opposing ends of the top edge respectively extend perpendicularly to form a first fixing portion and a second fixing portion. A simulation induction portion includes a first conduction strip extended obliquely from a substantial middle of the top edge and located at a substantially same plane with the first fixing portion, a second conduction strip extended along the top edge and towards the second fixing portion from a free end of the first conduction strip to form an obtuse angle between the first and second conduction strips. A connecting portion extends opposite to the grounding plate and perpendicularly from a free end of the second conduction strip. A feeding point is disposed on the connecting portion adjacent to the second conduction strip. A high frequency radiator has a first radiation strip extended downwards and then towards the second fixing portion from a free end of the connecting portion, facing to the grounding plate, a second radiation strip extended towards the grounding plate from a top edge of a free end of the first radiation strip, a third radiation strip extended perpendicularly from a free end of the second radiation strip and opposite to the first radiation strip. A low frequency radiator includes a fourth radiation strip extended oppositely to the first radiation strip from an end of the first radiation strip, a fifth radiation strip located at a substantially same plane with the connecting portion, with an inner edge and an outer edge farther from the grounding plate than the inner edge thereof. Two opposite ends of the outer edge of the fifth radiation strip respectively are connected with a free end of the fourth radiation strip and an end of a sixth radiation strip. The sixth radiation strip extends from the fifth radiation strip opposite to and in alignment with the fourth radiation strip. A seventh radiation strip extends from a free end of the sixth radiation strip opposite to and in alignment with the fifth radiation strip. 
     As described above, the multi-band antenna has a simple and compact structure to suit miniaturization development of the portable electronic device and reduce a manufacture cost, meanwhile, can improve performances of the multi-band antenna in a high and low frequency bands, such as in GSM850 (824˜880 MHZ), GSM900 (881˜960 MHZ), DCS (1710˜1850 MHZ), PCS (1880˜1990 MHZ) and WCDMA (2110˜2170 MHZ). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be apparent to those skilled in the art by reading the following description of an embodiment thereof, with reference to the attached drawings, in which: 
         FIG. 1  is a perspective view of a multi-band antenna according to the present invention; 
         FIG. 2  is a perspective view of the multi-band antenna shown in  FIG. 1  seen from anther direction; 
         FIG. 3  shows is a Smith chart recording impedance of the multi-band antenna shown in  FIG. 1 ; 
         FIG. 4  shows a Voltage Standing Wave Ratio (VSWR) test chart of the multi-band antenna shown in  FIG. 1 ; and 
         FIG. 5  shows an Antenna Performance test chart of the multi-band antenna shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT 
     Please refer to  FIG. 1 , an embodiment of a multi-band antenna mounted on a Note Book (not shown) according to the present invention is shown. The multi-band antenna  100  punched from a sheet metal includes an elongated grounding plate  1 , a simulation induction portion  2 , a connecting portion  3 , a feeding point  4 , a high frequency radiator  5  and a low frequency radiator  6 . 
     The elongated grounding plate  1  disposed vertically has a top edge  11  defined thereon. Two opposing ends of the top edge  11  respectively extend perpendicularly to the grounding plate  1  to form a first fixing portion  12  and a second fixing portion  13  both of rectangular shape. The first fixing portion  12  and the second fixing portion  13  are punched to form fixing holes  14  thereon for fixing the multi-band antenna  100  on the Note Book (not shown). The simulation induction portion  2  mitered with the grounding plate  1  has a first conduction strip  21  extended obliquely from a substantial middle of the top edge  11  and located at a substantially same plane with the first fixing portion  12 , a second conduction strip  22  extended along the top edge  11  and towards the second fixing portion  13  from a free end of the first conduction strip  21  to form an obtuse angle between the first and second conduction strips  21 ,  22 . A plane in which the grounding plate  1  locates is perpendicular to a plane in which the simulation induction portion  2  locates. A free end of the second conduction strip  22  extends opposite to the grounding plate  1  and perpendicularly to form a connecting portion  3 . The feeding point  4  is disposed on the connecting portion  3 , adjacent to the second conduction strip  22 . The high frequency radiator  5  has a first radiation strip  51  extended downwards and then elongated towards the second fixing portion  13  from a free end of the connecting portion  3 , parallel and facing to the grounding plate  1 . A top edge of a free end of the first radiation strip  51  extends towards the grounding plate  1  to form a second radiation strip  52 . A third radiation strip  53  extends perpendicularly from a free end of the second radiation strip  52  and opposite to the first radiation strip  51 . The third radiation strip  53  is spaced and flush with the second fixing portion  13  with a predetermined distance. The low frequency radiator  6  defines a fourth radiation strip  61  extended opposite to the first radiation strip  51  from an end of the first radiation strip  51  away from the second radiation strip  52 . A fifth radiation strip  62  is located at a substantially same plane with the connecting portion  3 , with an inner edge  621  spaced from the second conduction strip  22  and an outer edge  622  farther from the grounding plate  1  than the inner edge  621  thereof. Two opposite ends of the outer edge  622  of the fifth radiation strip  62  respectively are connected with a free end of the fourth radiation strip  61  and an end of a sixth radiation strip  63 . The sixth radiation strip  63  extends from the fifth radiation strip  62  opposite to and in alignment with the fourth radiation strip  61 . A seventh radiation strip  64  extends from a free end of the sixth radiation strip  63  opposite to and in alignment with the fifth radiation strip  62 . 
     When the multi-band antenna operates at a wireless communication environment, the simulation induction portion  2  achieves impedance matching with the low frequency radiator  5  and the high frequency radiator  6 . A current is fed from the feeding point  4  to the low frequency radiator  5  to generate an electronic resonance corresponding to frequency band ranging between 824 MHz and 960 MHz. While the current is fed from the feeding point  4  to the high frequency radiator  6  to generate an electronic corresponding to frequency band ranging between 1710 MHz and 2170 MHz. 
     Please refer to  FIG. 3 , which shows a Smith chart recording the impedance of the multi-band antenna in the embodiment when the multi-band antenna operates at a wireless communication environment. The multi-band antenna exhibits an impedance of (92.295−j75.890) Ohm at 824 MHz, an impedance of (36.661+j47.554) Ohm at 960 MHz, an impedance of (49.336+j27.195) Ohm at 1.71 GHz, an impedance of (88.579−j6.602) Ohm at 1.88 GHz, an impedance of (38.577+j26.485) Ohm at 2.17 GHz. Therefore, the multi-band antenna has good impedance characteristics. 
     Please refer to  FIG. 4 , which shows a Voltage Standing Wave Ratio (VSWR) test chart of the multi-band antenna in the embodiment when the multi-band antenna operates at a wireless communication environment. When the multi-band antenna operates at 824 MHz (indicator Mkr 1  in  FIG. 4 ), the VSWR value is 3.338. When the multi-band antenna operates at 960 MHz (indicator Mkr 2  in  FIG. 4 ), the VSWR value is 2.922. When the multi-band antenna operates at 1.71 GHz (indicator Mkr 3  in  FIG. 4 ), the VSWR value is 1.708. When the multi-band antenna operates at 1.88 GHz (indicator Mkr 4  in  FIG. 4 ), the VSWR value is 1.768. When the multi-band antenna operates at 2.17 GHz (indicator Mkr 5  in  FIG. 4 ), the VSWR value is 1.912. The VSWR value of the multi-band antenna shows that the multi-band antenna has an excellent frequency response between 824 MHz˜960 MHz and between 1.71 GHz˜2.17 GHz. 
     Please refer to  FIG. 5 , which shows a chart of an antenna transmission ratio of the multi-band antenna in the embodiment. When the multi-band antenna receives and sends electromagnetic signals in GSM 850 (824˜880 MHZ), the average antenna transmission ratio is 57.97%. When the multi-band antenna receives and sends electromagnetic signals in GSM 900 (881˜960 MHZ), the average antenna transmission ratio is 70.71%. When the multi-band antenna receives and sends electromagnetic signals in DCS (1710˜1850 MHZ), the average antenna transmission ratio is 58.50%. When the multi-band antenna receives and sends electromagnetic signals in PCS (1880˜1990 MHZ), the average antenna transmission ratio is 67.38%. When the multi-band antenna receives and sends electromagnetic signals in WCDMA (2110˜2170 MHZ), the average antenna transmission ratio is 44.91%. The average antenna transmission ratio shows that the multi-band antenna has a good performance in low and high bands. 
     As described above, the multi-band antenna  100  has a simple and compact structure to suit miniaturization development of the portable electronic device and reduce a manufacture cost, meanwhile, can improve performances of the multi-band antenna  100  in a high and low frequency bands, such as in GSM850 (824˜880 MHZ), GSM900 (881˜960 MHZ), DCS (1710˜1850 MHZ), PCS (1880˜1990 MHZ) and WCDMA (2110˜2170 MHZ). 
     Furthermore, the present invention is not limited to the embodiment described above; various additions, alterations and the like may be made within the scope of the present invention by a person skilled in the art. For example, respective embodiments may be appropriately combined.