Patent Publication Number: US-2019190157-A1

Title: Antenna structure and wireless communication device using the same

Description:
FIELD 
     The subject matter herein generally relates to an antenna structure and a wireless communication device using the antenna structure. 
     BACKGROUND 
     Metal housings are widely used for wireless communication devices, such as mobile phones and personal digital assistants (PDAs), and can be served as an antenna of the wireless communication device for receiving and transmitting wireless signals at different frequencies, such as signals in frequency bands adopted by Long Term Evolution Advanced (LTE-A) system. Additionally, the wireless communication device often defines a through hole corresponding to a Universal Serial Bus (USB) module. An external USB device can then be inserted into the through hole and be electrically connected to the USB module. However, when the external USB device is inserted into the through hole, the external USB device will pass across the antenna, thereby affecting a radiation performance of the antenna. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Implementations of the present disclosure will now be described, by way of example only, with reference to the attached figures. 
         FIG. 1  is an isometric view illustrating an embodiment of a portion of a wireless communication device having an antenna structure. 
         FIG. 2  is a circuit diagram of the antenna structure of  FIG. 1 . 
         FIG. 3  is a side view of the antenna structure of  FIG. 1 . 
         FIG. 4  is a circuit diagram of a matching circuit of the antenna structure of  FIG. 1 . 
         FIG. 5  is a circuit diagram of a switching circuit of the antenna structure of  FIG. 1 . 
         FIG. 6  is a scattering parameter graph of the antenna structure of  FIG. 1  for different values of a distance between a coupling portion and a second radiating section. 
         FIG. 7  is a scattering parameter graph of the antenna structure of  FIG. 1  for different values of a width of the coupling portion. 
         FIG. 8  is a scattering parameter graph of the antenna structure of  FIG. 1 . 
         FIG. 9  is a radiating efficiency graph of the antenna structure of  FIG. 1 . 
     
    
    
     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 “substantially” is defined to be essentially conforming to the particular dimension, shape, or other feature that the term 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 an antenna structure and a wireless communication device using same. 
       FIG. 1  illustrates an embodiment of a wireless communication device  200  having an antenna structure  100 . The wireless communication device  200  can be, for example, a mobile phone or a personal digital assistant. The antenna structure  100  can receive and transmit wireless signals. 
     In  FIGS. 1-3 , the antenna structure  100  includes a housing  11 , a feed source  12 , a matching circuit  13 , a connecting portion  15 , a coupling portion  16 , and a switching circuit  17 . 
     The housing  11  can be an outer housing of the wireless communication device  200 . In an embodiment, the housing  11  is made of metallic material and includes at least a back plate  111  and a side frame  112 . The back plate  111  and the side frame  112  can be integrally formed with each other. The side frame  112  is positioned around a periphery portion of the back plate  111 . The side frame  112  and the back plate  111  cooperatively form a receiving space  114 . The receiving space  114  can receive a printed circuit board, a processing unit, or other electronic components or modules (not shown) of the wireless communication device  200 . 
     In an embodiment, the side frame  112  includes an end portion  115 , a first side portion  116 , and a second side portion  117 . The end portion  115  can be a bottom portion of the wireless communication device  200 . The first side portion  116  is spaced apart from and parallel to the second side portion  117 . The end portion  115  has two ends. The first side portion  116  is connected to one end of the end portion  115  and the second side portion  117  is connected to the other end of the end portion  115 . 
     The housing  11  further defines a through hole  118  and a slot  119 . The through hole  118  is defined at the end portion  115  and passes through the end portion  115 . In this exemplary embodiment, the slot  119  is positioned adjacent to the end portion  115 . The slot  119  is defined in the back plate  111  and cuts through the first side portion  116  and the second side portion  117  to form a U-shaped slot. The housing  11  is divided into two portions by the slot  119 . The two portions are a radiating portion A 1  and a grounding portion A 2  spaced apart from the radiating portion A 1 . In this embodiment, the grounding portion A 2  is a ground of the antenna structure  100  and the wireless communication device  200 . 
     The feed source  12  is positioned in the receiving space  114 . One end of the feed source  12  is electrically connected to, through the matching circuit  13 , one portion of the radiating portion A 1  adjacent to the through hole  118 . The feed source  12  supplies current to the radiating portion A 1 . 
       FIG. 4  shows, in this embodiment, the matching circuit  13  includes a first matching element  131 , a second matching element  133 , a third matching element  135 , and a fourth matching element  137 . The first matching element  131  and the second matching element  133  are connected in series between the radiating portion A 1  and the feed source  12 . One end of the third matching element  135  is electrically connected to a junction of the first matching element  131  and the second matching element  133 . Another end of the third matching element  135  is grounded. One end of the fourth matching element  137  is electrically connected to a junction of the second matching element  133  and the feed source  12 . Another end of the fourth matching element  137  is grounded. 
     In this embodiment, the first matching element  131 , the second matching element  133 , and the fourth matching element  137  are all capacitors. The third matching element  135  is an inductor. Capacitance values of the first matching element  131 , the second matching element  133 , and the fourth matching element  137  are 6.3 pF, 5.4 pF, and 2.2 pF, respectively. An inductance value of the third matching element  135  is about 12 nH. 
     In other embodiments, the first matching element  131 , the second matching element  133 , the third matching element  135 , and the fourth matching element  137  may be other than inductors and capacitors. For example, the first matching element  131 , the second matching element  133 , the third matching element  135 , and the fourth matching element  137  can be other impedance elements or a combination. 
     In this embodiment, when the feed source  12  supplies current, the current will flow towards the first side portion  116  and the second side portion  117  at the radiating portion A 1 , so that the radiating portion A 1  is divided, by the feed source  12  functioning as a separation point, into a first radiating section A 11  adjacent to the first side portion  116  and a second radiating section A 12  adjacent to the second side portion  117 . 
     In this embodiment, one portion of the radiating portion A 1  between the feed source  12  and the first side portion  116  is the first radiating section A 11 . Another one portion of the radiating portion A 1  between the feed source  12  and the second side portion  117  is the second radiating section A 12 . In this exemplary embodiment, a location of the feed source  12  does not correspond to a middle position of the radiating portion A 1 . The second radiating section A 12  is longer in length than the first radiating section A 11 . 
     In this embodiment, when the feed source  12  supplies current, the current flows through the first radiating section A 11 , so that the first radiating section A 11  excites a first resonant mode for generating radiation signals in a first frequency band. When the feed source  12  supplies current, the current flows through the second radiating section A 12 , so that the second radiating section A 12  excites a second resonant mode for generating radiation signals in a second frequency band. In this embodiment, the first resonant mode is a Long Term Evolution Advanced (LTE-A) middle frequency resonant mode. The second resonant mode is a LTE-A low frequency resonant mode. Frequencies of the first frequency band are higher than frequencies of the second frequency band. 
     In an embodiment, the connecting portion  15  can be a flat spring, a screw, a microstrip line, a probe, a flexible circuit board, or other connecting structures. The connecting portion  15  is positioned between the feed source  12  and the first side portion  116 . One end of the connecting portion  15  is electrically connected to one end of the radiating portion A 1  adjacent to the first side portion  116 . Another end of the connecting portion  15  is electrically connected to the grounding portion A 2  for grounding the radiating portion A 1 . 
     In this embodiment, frequencies of the first frequency band can be effectively adjusted through adjusting a length of the connecting portion  15  and a grounding position of the connecting portion  15 . 
     Referring to  FIG. 1  and  FIG. 3 , the coupling portion  16  is positioned between the feed source  12  and the second side portion  117  and includes a connecting section  161  and a coupling section  163 . The connecting section  161  is substantially rectangular. One end of the connecting section  161  is perpendicularly connected to one end of the grounding portion A 2  adjacent to the slot  119 . Another end of the connecting section  161  extends along a direction perpendicular to the back plate  111  and parallel to the end portion  115 . 
     The coupling section  163  is substantially rectangular. One end of the coupling section  163  is perpendicularly connected to one end of the connecting section  161  away from the grounding portion A 2 . Another end of the coupling section  163  extends along a direction parallel to the back plate  111  towards the end portion  115 . The coupling section  163  is parallel to the radiating portion A 1 . 
       FIG. 1  shows, in this embodiment, when the feed source  12  supplies current, the current flows through the second radiating section A 12  and is coupled to the coupling portion  16  through the second radiating section A 12 . Then, the second radiating section A 12  generates a harmonic frequency to excite a third resonant mode for generating radiation signals in a third frequency band. 
     In  FIG. 2 , through adjusting a size of the coupling portion  16 , for example, adjusting a width W of the coupling portion  16 , a location of the coupling portion  16 , and a distance g (shown in  FIG. 3 ) between the coupling portion  16  and the second radiating section A 12 , frequencies of the third frequency band can be adjusted to fall within a frequency band of WIFI 2.4 GHz. In this embodiment, the third resonant mode is a WIFI 2.4 GHz mode and/or a LTE-A high frequency resonant mode. 
     Now referring to  FIGS. 1 to 3 , the wireless communication device  200  further includes at least one electronic element. In this embodiment, the wireless communication device  200  includes an electronic element  202 . The electronic element  202  can be, for example, a Universal Serial Bus (USB) module. The electronic element  202  is disposed in the receiving space  114 . In  FIG. 1 , the electronic element  202  is disposed on a surface of the coupling section  163  away from the back plate  111 . That is, the electronic element  202  is disposed on and supported by the coupling section  163 . In  FIG. 1 , the electronic element  202  corresponds in a position to the through hole  118  and is partially exposed from the through hole  118 . An external USB device can be inserted into the through hole  118  and be electrically connected to the electronic element  202 . 
     The switching circuit  17  is disposed in the receiving space  114  between the through hole  118  and the second side portion  117 . One end of the switching circuit  17  is electrically connected to one portion of the second radiating section A 12  adjacent to the through hole  118 . Another end of the switching circuit  17  is electrically connected to the grounding portion A 2  to be grounded. 
     In  FIG. 5 , the switching circuit  17  includes a switch  171  and a plurality of switching elements  173 . In this embodiment, the switching circuit  17  includes two switching elements  173 . The switch  171  is electrically connected to the second radiating section A 12 . Each switching element  173  can be an inductor, a capacitor, or a combination of the inductor and the capacitor. The switching elements  173  are connected in parallel to each other. One end of each switching element  173  is electrically connected to the switch  171 . The other end of each switching element  173  is electrically connected to the grounding portion A 2  to be grounded. 
     The second radiating section A 12  can be switched to connect with different switching elements  173  through switching of the switch  171 . Since each switching element  173  has a different impedance, a frequency band, i.e. the second frequency band, of the second radiating section A 12  can be adjusted through the switching of the switch  171 . Accordingly, a low frequency band of the antenna structure  100  can cover a frequency band of LTE band  28  (704 MHz-803 MHz), a frequency band of GSM  850 , and a frequency band of EGSM  900 . 
     In  FIG. 1 , for example, when the feed source  12  supplies current, the current flows to the first radiating section A 11  through the matching circuit  13 , and is further grounded through the connecting portion  15 . The feed source  12 , the first radiating section A 11 , and the connecting portion  15  cooperatively form an inverted-F antenna to excite the first resonant mode for generating radiation signals in the first frequency band. 
     When the feed source  12  supplies current, the current flows to the second radiating section A 12  through the matching circuit  13 , and is further grounded through the switching circuit  17 . The feed source  12 , the second radiating section A 12 , and the switching circuit  17  cooperatively form another inverted-F antenna to excite the second resonant mode for generating radiation signals in the second frequency band. 
     When the feed source  12  supplies current, the current flows to the second radiating section A 12  through the matching circuit  13 . The current is further coupled to the coupling section  163  of the coupling portion  16  through the second radiating section A 12  to excite the third resonant mode for generating radiation signals in the third frequency band. 
     In addition, the antenna structure  100  includes the matching circuit  13  to perform a matching adjustment of the antenna structure  100 , so that a bandwidth of the antenna structure  100  can cover 704 MHz-960 MHz and 1710 MHz-2690 MHz, that is, to cover the current frequency bands of 4G LTE including 704 MHz-960 MHz, 1710 MHz-1990 MHz, 2110 MHz-2170 MHz, 2300 MHz-2400 MHz, and 2500 MHz-2690 MHz. 
       FIG. 6  is a scattering parameter graph of the antenna structure  100  for different values of the distance g between the coupling portion  16  and the second radiating section A 12 . Curve S 61  represents scattering parameters of the antenna structure  100  when the distance g between the coupling portion  16  and the second radiating section A 12  is about 0.3 mm. Curve S 62  represents scattering parameters of the antenna structure  100  when the distance g between the coupling portion  16  and the second radiating section A 12  is about 0.5 mm. Curve S 63  represents scattering parameters of the antenna structure  100  when the distance g between the coupling portion  16  and the second radiating section A 12  is about 0.7 mm. Curve S 64  represents scattering parameters of the antenna structure  100  when the distance g between the coupling portion  16  and the second radiating section A 12  is about 0.9 mm. 
       FIG. 7  is a scattering parameter graph of the antenna structure  100  for different values of the width W of the coupling portion  16 . Curve S 71  represents scattering parameters of the antenna structure  100  when the width W of the coupling portion  16  is about 6 mm. Curve S 72  represents scattering parameters of the antenna structure  100  when the width W of the coupling portion  16  is about 5.5 mm. Curve S 73  represents scattering parameters of the antenna structure  100  when the width W of the coupling portion  16  is about 5 mm. Curve S 74  represents scattering parameters of the antenna structure  100  when the width W of the coupling portion  16  is about 4.5 mm. Curve S 75  represents scattering parameters of the antenna structure  100  when the width W of the coupling portion  16  is about 4 mm. 
       FIG. 8  is a scattering parameter graph of the antenna structure  100 . Curve S 81  represents scattering parameters of the antenna structure  100  when the antenna structure  100  does not include the matching circuit  13 . Curve S 82  represents scattering parameters of the antenna structure  100  when the antenna structure  100  includes the matching circuit  13 .  FIG. 9  is a radiating efficiency graph of the antenna structure  100 . 
     In  FIGS. 6-9 , the antenna structure  100  may completely cover system bandwidths required by currently communication systems. For example, the low frequency band of the antenna structure  100  can cover 704 MHz-960 MHz, and the middle and high frequency bands of the antenna structure  100  can cover 1710 MHz-1990 MHz, 2110 MHz-2170 MHz, 2300 MHz-2400 MHz, and 2500 MHz-2690 MHz, which meets the antenna design requirements. 
     The antenna structure  100  includes the housing  11 . The housing  11  is divided into the radiating portion A 1  and the grounding portion A 2  as shown in  FIG. 1  for example. The antenna structure  100  further includes the coupling portion  16 . The coupling portion  16  is spaced apart from the radiating portion A 1 . The coupling portion  16  can effectively shield the electronic element  202  and the radiating portion A 1 , thereby preventing the electronic element  202  from affecting the radiation of the antenna structure  100 . With the coupling portion  16 , the antenna structure  100  can excite an additional resonant mode. In addition, with the matching circuit  13 , the antenna structure  100  can have a broadband effect. 
     The embodiments shown and described above are only examples. Many details are often found in the art such as the other features of the antenna structure and the wireless communication device. Therefore, many such details are neither shown nor described. Even though numerous characteristics and advantages of the present disclosure have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in the details, especially in matters of shape, size, and arrangement of the parts within the principles of the present disclosure, up to and including the full extent established by the broad general meaning of the terms used in the claims. It will therefore be appreciated that the embodiments described above may be modified within the scope of the claims.