Patent Publication Number: US-9899729-B2

Title: Antenna system

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure generally relates to mobile communication technologies, and more particularly, to an antenna system applicable to a mobile communication device. 
     BACKGROUND 
     With the development of mobile communication technologies, mobile communication devices such as mobile phones, tablet computers, or the like, are used more and more widely. Mobile communication devices with metal shells are preferred by people because of their fashion appearance as well as good durability. 
     In a typical mobile communication device, two parallel gaps are formed on a metal back cover thereof to enable a corresponding part of the metal cover to serve as an antenna radiator. However, the parallel gaps may impact the appearance and integrality of the metal shell, and also lower radiation efficiency of the antenna radiator. 
     Therefore, it is necessary to provide a new antenna system which can overcome the aforesaid problems. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the embodiments can be better understood with reference to the following drawings. The components in the drawing are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is a planar view of an antenna system according to an exemplary embodiment of the present disclosure. 
         FIG. 2  is an enlarged, partial view of the antenna system of  FIG. 1 . 
         FIG. 3  is a rear view of the antenna system of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure will be described in detail below with reference to the attached drawings and an embodiment thereof. 
     Referring to  FIG. 1  and  FIG. 2 , an antenna system  100  according to an embodiment of the present disclosure includes a metal shell  101 , a printed circuit board (PCB)  104  and an antenna part. The PCB  104  is housed in the metal shell  101 , and includes at least one ground point; the antenna part is disposed on the PCB  104 . 
     The metal shell  101  includes a metal back cover  102  and a metal frame  103 . The metal back cover  102  is surrounded by the metal frame  103 , and is connected to the metal frame  103 . Moreover, a first break point  103 A and a second break point  103 B are symmetrically formed at two opposite sides of the metal frame  103 , and the first break point  103 A and the second break point  103 B are configured for separating the metal frame  103  into a top frame portion  105  and a main frame assembly. In particular, the main frame assembly includes a left frame portion  106 , a right frame portion  107  opposite to the left frame portion  106 , and a bottom frame portion  108  opposite to the top frame portion  105 . 
     A first gap  109  and a second gap  110  are respectively formed at two opposite sides of the metal back cover  102 , and the first gap  109  and the second gap  110  are located adjacent to the top frame portion  105 . In the present embodiment, both the first gap  109  and the second gap  110  are L-shaped gaps formed at edges of the metal back cover  102 . 
     For example, the metal back cover  102  includes a top edge near the top frame portion  105 , a left edge near the left frame portion  106 , and a right edge near the right frame portion  107 . The first gap  109  extends from the top edge of the metal back cover  102  to the left edge of the metal back cover  102 , passing through a top left corner of the metal back cover  102  in an L-shaped manner. The second gap  110  extends from the top edge of the metal back cover  102  to the right edge of the metal back cover  102 , passing through a top right corner of the metal back cover  102  also in an L-shaped manner. 
     The metal back cover  102 , the left frame portion  106  and a left end of the top frame portion  105  are separated by the first gap  109  to form a first clearance area. The metal back cover  102 , the right frame portion  107  and a right end of the top frame portion  105  are separated by the second gap  110  to form a second clearance area. The first break point  103 A is communicated with the first clearance area, and the second break  103 B is communicated with the second clearance area. 
     The antenna part includes a first feed point  111  and a second feed point  112 , both of which are disposed on the PCB  104 . The first feed point  111  is located in the first clearance area and contacts the left frame portion  106 ; the second feed point  112  is located in the second clearance area and contacts the right frame portion  107 . Furthermore, the antenna part further includes a matching circuit and a plurality of ground points, and the matching circuit is electrically connected to the first feed point  111 . The metal back cover  102  is electrically connected to the ground points on the PCB  104 , and thus the metal back cover  102  is grounded entirely. 
     In the present embodiment, four ground points  113 ,  114 ,  115  and  116  are provided in the antenna system  100  as illustrated in  FIG. 2 , and the metal frame  103  is grounded through the four ground points  113 ,  114 ,  115  and  116 . The matching circuit may include a first inductor, a capacitor and a second inductor. Both the capacitor and the second inductor are electrically connected in parallel with the first inductor. An inductance of the first inductor may be approximate 1 nH, a capacitance of the capacitor may be approximate 0.6 pF, and an inductance of the first inductor may be approximate 4.7 nH. 
     Referring also to  FIG. 3 , a length L 1  of the first clearance area, which extends from the first break point  103 A along the left frame portion  106 , is approximate 30.7 mm. A length L 2  of the second clearance area, which extends from the second break point  103 B along the right frame portion  107 , is approximate 25.7 mm. Widths of the first clearance area and the second clearance area are both approximate 2 mm. Volumes of the first clearance area and the second clearance area are respectively related to corresponding antenna frequencies thereof. 
     In an exemplary embodiment of the present disclosure, the first feed point  111  serves as a GPS/WIFI antenna feed point, namely, a feed point provided for both a GPS antenna and a WIFI antenna. A frequency range of the GPS antenna is from 1570 MHz to 1610 MHz; a low frequency range of the WIFI antenna is from 2400 MHz to 2484 MHz, and a high frequency range of the WIFI antenna is from 5150 MHz to 5875 MHz. The second feed point  112  serves as a diversity antenna feed point, namely, a feed point provided for a diversity antenna. A frequency range of the diversity antenna is from 1805 MHz to 2170 MHz. As can be seen, the frequency range of the GPS/WIFI antenna is less than that of the diversity antenna, which means that a wavelength range of the GPS/WIFI antenna is greater than that of the diversity antenna. Therefore, a volume of the first clearance area corresponding to the GPS/WIFI antenna needs to be slightly greater than that of the second clearance area corresponding to the diversity antenna. 
     Furthermore, a furthest straight-line distance L between the top frame portion  105  and the first break point  103 A or the second break point  103 B is approximate 9.3 mm, and widths of both the first break point  103 A and the second break point  103 B are approximate 1.5 mm. 
     In the antenna system  100  as provided in the present disclosure, two gaps are respectively provided at two opposite sides of a top portion of the metal back cover  102  to form the first clearance area and the second clearance area, and both the first clearance area and the second clearance area are close to the metal frame  103  with a narrow width. With this configuration, integrality of the metal shell  101  can be maintained to ensure the mobile communication device to have a good appearance; moreover, the antenna system  100  can also have good isolation (e.g., less than −20 dB), and therefore, a radiation efficiency of the antenna system  100  can be improved. 
     It is to be understood, however, that even though numerous characteristics and advantages of the present embodiment have been set forth in the foregoing description, together with details of the structures and functions of the embodiment, 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.