Patent Publication Number: US-9887451-B2

Title: Antenna structure and wireless communication device using same

Description:
FIELD 
     The disclosure generally relates to antenna structure and wireless communication device using same. 
     BACKGROUND 
     Long term evolution (LTE) antennas are used in wireless communication devices, such as mobile phones, for receiving and transmitting wireless signals at a plurality of bandwidths. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present disclosure can be better understood with reference to the drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the views. 
         FIG. 1  is an isometric view of a wireless communication device, according to an exemplary embodiment. 
         FIG. 2  is an isometric view of an antenna structure, according to an exemplary embodiment. 
         FIG. 3  is a circuit view of a matching circuit of the wireless communication device of  FIG. 1 . 
         FIG. 4  is an exploded view of the antenna structure of  FIG. 2 . 
         FIG. 5  is a first return loss (RL) graph of the antenna structure working in a low frequency mode and a high frequency mode. 
         FIG. 6  is a second RL graph of the antenna structure working in a low frequency mode and a high frequency mode. 
     
    
    
     DETAILED DESCRIPTION 
     It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein. The drawings are not necessarily to scale and the proportions of certain parts have been exaggerated to better illustrate details and features of the present disclosure. 
     Several definitions that apply throughout this disclosure will now be presented. 
     The term “coupled” is defined as connected, whether directly or indirectly through intervening components, and is not necessarily limited to physical connections. The connection can be such that the objects are permanently connected or releasably connected. The term “outside” refers to a region that is beyond the outermost confines of a physical object. The term “inside” indicates that at least a portion of a region is partially contained within a boundary formed by the object. The term “substantially” is defined to be essentially conforming to the particular dimension, shape or other word that substantially modifies, such that the component need not be exact. For example, substantially cylindrical means that the object resembles a cylinder, but can have one or more deviations from a true cylinder. The term “comprising,” when utilized, means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in the so-described combination, group, series and the like. 
     The present disclosure is described in relation to a wireless communication device. 
       FIGS. 1-2  illustrate a wireless communication device  100  employing an antenna structure  50 , according to an exemplary embodiment. The wireless communication device  100  can be a mobile phone or a tablet device, for example (details not shown). 
     The wireless communication device  100  includes a printed circuit board (PCB)  10 . The PCB  10  is a substantially rectangular board having a keep-out-zone  12 . The purpose of keep-out-zone  12  is to delineate an area on the PCB  10  in which other elements (such as a camera, a vibrator, a speaker, etc.) cannot be placed. 
     In the exemplary embodiment, the keep-out-zone  12  is located near an end of the PCB  10  and a housing  70 . The PCB  10  further forms a feed pin  14  and a ground pin  16  in the keep-out-zone  12 . The feed pin  14  provides current for the antenna structure  50 , and the antenna structure  50  can be grounded by the ground pin  16 . 
     The antenna structure  50  includes a feed end  51 , a ground end  53 , a first metallic sheet  55 , a second metallic sheet  57 , and a radiator  59 . A first gap  71  is defined between the housing  70  and the first metallic sheet  55 , and a second gap  72  is defined between the housing  70  and the second metallic sheet  57 . 
     The feed end  51  is coupled to the feed pin  14 . The ground end  53  is substantially parallel to the feed end  51 , and is coupled to the ground pin  16 . Both of the first metallic sheet  55  and the second metallic sheet  57  can be metal frames of the wireless communication device  100 . In at least one embodiment, both the first metallic sheet  55  and the second metallic sheet  57  are rectangular sheets, and are positioned at two opposite sides of the keep-out-zone  12 . The radiator  59  is coupled to the first metallic sheet  55  and the second metallic sheet  57  to form a loop structure. 
       FIG. 3  illustrates that the wireless communication device  100  further includes a matching circuit  200 . The matching circuit  200  is configured to match an impedance of the antenna structure  50  for optimizing performance of the antenna structure  50  when the antenna structure  50  works in a low frequency mode. The matching circuit  200  is electronically coupled between the feed end  51  and the feed pin  14 . In at least one embodiment, the matching circuit  200  includes a first capacitor C 1 , a second capacitor C 2 , and an inductor L. The first capacitor C 1  and the inductor L are connected between the feed pin  14  and the antenna structure  50  in series. A first end of the second capacitor C 2  is coupled between the inductor L and the antenna structure  50 , and a second end of the second capacitor C 2  is coupled to a ground. The first capacitor C 1  can be an adjustable capacitor. In at least one embodiment, a capacitance value of the first capacitor C 1  can be, for example, about 1.8 pF or 15 pF, a capacitance value of the second capacitor C 2  can be, for example, about 1.3 pF, and an inductance value of the inductor L can be, for example, about 4.7 nH. 
       FIG. 4  illustrates the radiator  59  including a first radiator portion  595 , a second radiator portion  593 , a third radiator portion  591 , a first connection section  594 , and a second connection section  592 . A plane of the first radiator portion  595 , the first connection section  594 , and the second connection section  592  is substantially perpendicular to the PCB  10 . A plane of the second radiator portion  593  and the third radiator portion  591  is substantially parallel to the PCB  10 . 
     The first radiator portion  595  includes a main body  5951  and two distal ends  5953 . The main body  5951  is a rectangular sheet. The two distal ends  5953  are positioned at two opposite sides of the first radiator portion  595 , and are connected to two ends of the second metallic sheet  57 , respectively. 
     The second radiator portion  593  and the third radiator portion  591  are substantially perpendicular to the first radiator portion  595 , and are symmetrically positioned at a flange of the first radiator portion  595 . The second radiator portion  593  is connected to the ground end  53 , and includes a first extending section  5931 , a second extending section  5933 , and a third extending section  5935 . The first extending section  5931  is substantially perpendicular to the ground end  53  and extends away from the feed end  51 . The second extending section  5933  is perpendicularly connected between the first extending section  5931  and the third extending section  5935 . The third extending section  5935  connects to a flange of the main body  5951 , and extends along the main body  5951  until a distal end of the third extending section  5935  is aligned with a first distal end of the main body  5951 . The third radiator portion  591  is connected to the feed end  51 , and includes a first radiation section  5911 , a second radiation section  5913 , and a third radiation section  5915 . The first radiation section  5911  is substantially perpendicular to the feed end  51  and extends away from the ground end  53 . The second radiation section  5933  is perpendicularly connected between the first radiation section  5911  and the third radiation section  5915 . The third radiation section  5915  connects to the flange of the main body  5951 , and extends along the main body  5951  until a distal end of the third radiation section  5915  is aligned with a second distal end of the main body  5951 . 
     The first connection section  594  is perpendicularly connected between the first extending section  5931  and the first metallic sheet  55 . The second connection section  592  is perpendicularly connected between the first radiation section  5911  and the first metallic sheet  55 . 
     When current is input to the feed pin  14 , a first portion of the current flows to the matching circuit  200 , the feed end  51 , the third radiator portion  591 , the first radiator portion  595 , the second metallic sheet  57 , the second radiator portion  593 , the first gap  71 , and the first metallic sheet  55  to form a first current path for resonating a first low frequency mode. A second portion of the current flows to the third radiator portion  591 , the first radiator portion  595 , the first gap  71 , and the second radiator portion  593  to form a second current path for resonating a second low frequency mode. When the capacitance value of the first capacitor C 1  is about 15 pF, a central frequency of the first low frequency mode can be, for example, about 800 MHZ, and a central frequency of the second low frequency mode can be, for example, about 925 MHZ. When the capacitance value of the first capacitor C 1  is about 1.8 pF, a central frequency of the first low frequency mode can be, for example, about 700 MHZ, and a central frequency of the second low frequency mode can be, for example, about 850 MHZ. 
     Additionally, the second portion of the current can resonate a first high frequency mode and a second high frequency mode based on frequency doubling. A central frequency of the first high frequency mode can be, for example, about 1730 MHZ, and a central frequency of the second high frequency mode can be, for example, about 1910 MHZ. And then, a third portion of the current flows to the third radiator portion  591 , the main body  5951 , and the second radiator portion  593  to form a third current path for resonating a third high frequency mode. A central frequency of the third high frequency mode can be, for example, about 2200 MHZ. Moreover, a fourth portion of the current flows to the third radiator portion  591 , the main body  5951 , the second radiator portion  593 , the first connection section  594 , the second connection section  592 , and the first metallic sheet  55  to form a fourth current path for resonating a fourth high frequency mode. A central frequency of the fourth high frequency mode can be, for example, about 2500 MHZ. Furthermore, a fifth portion of the current flows to the first connection section, the second connection section, and the first metallic sheet  55  to form a fifth current path for resonating a fifth high frequency mode. A central frequency of the fifth high frequency mode can be, for example, about 2630 MHZ. 
       FIGS. 5-6  illustrate return loss (RL) graphs of the antenna structure  50  working in the first low frequency mode, the second low frequency mode, the first high frequency mode, the second high frequency mode, the third high frequency mode, the fourth high frequency mode, and the fifth high frequency mode. The wireless communication device  100  has good performance when operating at 750-960 MHZ, 700-900 MHZ, and 1710-2710 MHZ. 
     In summary, the radiator  59  is connected between the first metallic sheet  55  and the second metallic sheet  57  to allow the first metallic sheet  55  and the second metallic sheet  57  to be configured as a portion of the antenna structure  50 . Thus, the wireless communication device  100  does not need any additional antennas, which can effectively utilize a space of the wireless communication device  100 . In addition, a radiating capability of the antenna structure  50  of the wireless communication device  100  is effectively improved because of the matching circuit  200 . 
     It is to be understood, however, that even through numerous characteristics and advantages of the present disclosure have been set forth in the foregoing description, together with details of assembly and function, the disclosure is illustrative only, and changes may be made in detail, especially in the matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.