Patent Publication Number: US-2010123628-A1

Title: Multi-Band Antenna

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an antenna, and more particularly to a multi-band antenna. 
     2. The Related Art 
     In recent years, portable wireless communication devices are becoming progressively popular. In order to communicate with other communication devices, various antennas are assembled in these devices for transmitting and receiving electromagnetic waves. Considering the miniaturization trend of the portable wireless communication device, the size of the antenna should be correspondingly reduced in order to be assembled in the limited space of the portable wireless communication device. 
     Among present wireless technologies, wireless communication bands include global system for mobile communications (GSM) band about 850 MHz, extended global system for mobile communications (EGSM) band about 900 MHz, digital cellular system (DCS) band about 1800 MHz, personal conferencing specification (PCS) band about 1900 MHz and wideband code division multiple access (WCDMA) band about 2000 MHz. 
     Many different types of antennas for the portable wireless communication devices are used, including planar inverted-F antennas, monopole antennas, loop antennas and the like. However, all of these antennas could not meet the demand of operating at multiple frequencies while the sizes thereof are reduced. Therefore, a disadvantage is exposed that covering multiple frequencies and occupying smaller space could not concurrent. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a multi-band antenna covering multiple bands and having reduced size. The multi-band antenna includes a base plate, a first radiating portion and a second radiating portion. The base plate has a first edge and a second edge perpendicularly connected with the first edge. A slot is defined substantially at a middle portion of the base plate and parallel to the first edge and penetrating through the second edge to divide the base plate into a grounding portion and a feeding portion which defines the first edge as a long edge thereof. The first radiating portion extends substantially perpendicularly from the first edge of the base plate and has a transverse edge facing and substantially parallel to the second edge of the base plate. The second radiating portion has a connecting section extending substantially perpendicularly from the transverse edge of the first radiating portion and a radiating part which shows a substantial stair-shape connected with the connecting section. The radiating part has a first radiating strip extending substantially perpendicularly and in opposition to the first edge of the base plate from a free end of the connecting section, a second radiating strip extending substantially perpendicularly and towards the first radiating portion from a free end of the first radiating strip, a third radiating strip extending substantially perpendicularly and in opposition to the first radiating strip from a free end of the second radiating strip, and an extended radiating strip extending continuously from a free end of the third radiating strip and then expanding in opposition to the second radiating strip to be wider than the third radiating strip. 
     As described above, the arrangement of the first radiating portion and the second radiating portion makes the multi-band antenna transmit and receive multiple bands. The feeding portion and the grounding portion are separated by the slot, the radiating part of the second radiating portion is designed as a substantial stair-shape structure, which reduces the size of the multi-band antenna and makes the multi-band antenna take up smaller space when assembled in a portable wireless communication device. 
    
    
     
       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: 
       FIGURE is a plan view of a multi-band antenna in accordance with the present invention; 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to FIGURE, a multi-band antenna  1  according to the invention is etched by a flexible printed circuit board  2 . The multi-band antenna  1  includes a substantially rectangular base plate  11  which defines a first edge  11 A and a second edge  11 B perpendicularly connected with the first edge  11 A. 
     The base plate  11  has an elongated slot  15  longitudinally extending at a middle portion thereof and substantially parallel to the first edge  11 A. The slot  15  penetrates through the second edge  11 B to divide the base plate  11  into a grounding portion  17  and a feeding portion  16  which defines the first edge  11 A as a long edge thereof. The feeding portion  16  defines a feeding point  161  adjacent to the second edge  11 B, the grounding portion  17  defines a grounding point  171  adjacent to the second edge  11 B too. The feeding portion  16  and the grounding portion  17  form a simulation inductance therebetween for tuning bandwidth and input impedance of the multi-band antenna  1  to realize impedance matching between the multi-band antenna  1  and a feeding cable (not shown). 
     A substantially rectangular first radiating portion  12  extends substantially perpendicularly from a middle portion of the first edge  11 A. The first radiating portion  12  has a transverse edge  121  facing and substantially parallel to the second edge  11 B of the base plate  11 . A second radiating portion  13  extends from the transverse edge  121  and the width thereof is smaller than the width of the first radiating portion  12 . The second radiating portion  13  includes a connecting section  131  extending substantially perpendicularly from the transverse edge  121  and a radiating part  132  which shows a substantial stair-shape connected with the connecting section  131 . The connecting section  131  is arranged adjacent to the first edge  11 A of the base plate  11  and an opening  14  is formed between the base plate  11  and the connecting section  131 . 
     The radiating part  132  has a first radiating strip  132 A extending substantially perpendicularly and in opposition to the first edge  11 A of the base plate  11  from a free end of the connecting section  131  to be parallel to the first radiating portion  12 . The first radiating strip  132 A defines an outer edge  132 A 1  substantially at the same level with the second edge  11 B of the base plate  11 . A free end of the first radiating strip  132 A extends substantially perpendicularly and towards the first radiating portion  12  to form a second radiating strip  132 B adjacent to a free end of the first radiating portion  12 . A third radiating strip  132 C extends substantially perpendicularly and in opposition to the first radiating strip  132 A from a free end of the second radiating strip  132 B. An extended radiating strip  132 D extends continuously from a free end of the third radiating strip  132 C and then expands in opposition to the second radiating strip  132 B to be wider than the third radiating strip  132 C. The extended radiating strip  132 D has a top edge  132 D 1  substantially in alignment with the transverse edge  121  of the first radiating portion  12 . 
     When the multi-band antenna  1  is used in wireless communication, an electric current is fed into the multi-band antenna  1  by means of the feeding point  161 . The first radiating portion  12  resonates at a higher frequency range covering from 1800 MHz to 2000 MHz; the second radiating portion  13  operates at a lower frequency range covering from 850 MHz to 900 MHz. Therefore, the multi-band antenna  1  obtains frequency range covering 850 MHz, 900 MHz, 1800 MHz, 1900 MHz and 2000 MHz corresponding to GSM band, EGMS band, DCS band, PCS band and WCDMA band in wireless communication. 
     As described above, the arrangement of the first radiating portion  12  and the second radiating portion  13  makes the multi-band antenna  1  transmit and receive multiple bands covering 850 MHz, 900 MHz, 1800 MHz, 1900 MHz and 2000 MHz. The feeding portion  16  and the grounding portion  17  are separated by the slot  15 , the radiating part  132  of the second radiating portion  13  is designed as a substantial stair-shape structure, which reduces the size of the multi-band antenna  1  and makes the multi-band antenna  1  take up smaller space when assembled in a portable wireless communication device. 
     Moreover, the multi-band antenna  1  can be duly bent according to the internal structure of the portable wireless communication device for conveniently being assembled in the portable wireless communication device. The multi-band antenna  1  even can be fixed to a specific antenna holder and then assembled in the portable wireless communication device to further reduce the occupancy space. Therefore, the multi-band antenna  1  not only can transmit and receive multiple bands covering from 850 MHz to 2000 MHz, but also occupies smaller space in the portable wireless communication device.