Patent Publication Number: US-9905913-B2

Title: Antenna structure and wireless communication device using same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Taiwanese Patent Application No. 106119261 filed on Jun. 9, 2017, and claims priority to U.S. Patent Application No. 62/364876, filed on Jul. 21, 2016, the contents of which are incorporated by reference herein. 
    
    
     FIELD 
     The subject matter herein generally relates to an antenna structure and a wireless communication device using the antenna structure. 
     BACKGROUND 
     Metal housings, for example, metallic backboards, are widely used for wireless communication devices, such as mobile phones or personal digital assistants (PDAs). Antennas are also important components in wireless communication devices for receiving and transmitting wireless signals at different frequencies, such as signals in Long Term Evolution Advanced (LTE-A) frequency bands. However, when the antenna is located in the metal housing, the antenna signals are often shielded by the metal housing. This can degrade the operation of the wireless communication device. Additionally, the metallic backboard generally defines slots or/and gaps thereon, which will affect an integrity and an aesthetic quality of the metallic backboard. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Implementations of the present technology will now be described, by way of example only, with reference to the attached figures. 
         FIG. 1  is an isometric view of a first exemplary embodiment of a wireless communication device using a first exemplary antenna structure. 
         FIG. 2  is similar to  FIG. 1 , but shown from another angle. 
         FIG. 3  is an assembled, isometric view of the wireless communication device of  FIG. 1 . 
         FIG. 4  is a circuit diagram of the antenna structure of  FIG. 1 . 
         FIG. 5  is a circuit diagram of a first switching circuit of the antenna structure of  FIG. 1 . 
         FIG. 6  is a circuit diagram of a second switching circuit of the antenna structure of  FIG. 1 . 
         FIG. 7  is a scattering parameter graph when the antenna structure of  FIG. 1  works at a first operation mode. 
         FIG. 8  is a radiating efficiency graph when the antenna structure of  FIG. 1  works at a first operation mode. 
         FIG. 9  is a scattering parameter graph when the antenna structure of  FIG. 1  works at a Global Positioning System (GPS) operation mode, a WIFI 2.4G mode, and a WIFI 5G mode. 
         FIG. 10  is a radiating efficiency graph when the antenna structure of  FIG. 1  works at a GPS operation mode, a WIFI 2.4G mode, and a WIFI 5G mode. 
         FIG. 11  is an isometric view of a second exemplary embodiment of a wireless communication device using a second exemplary antenna structure. 
         FIG. 12  is similar to  FIG. 11 , but shown from another angle. 
         FIG. 13  is an assembled, isometric view of the wireless communication device of  FIG. 11 . 
         FIG. 14  is a circuit diagram of the antenna structure of  FIG. 11 . 
         FIG. 15  is a current path distribution graph when the antenna structure of 
         FIG. 11  works at a first operation mode. 
         FIG. 16  is a current path distribution graph when the antenna structure of 
         FIG. 11  works at a second operation mode. 
         FIG. 17  is a circuit diagram of a switching circuit of the antenna structure of  FIG. 11 . 
         FIGS. 18 and 19  are scattering parameter graphs of the antenna structure of  FIG. 11 . 
         FIGS. 20 and 21  are radiation gain graphs of the antenna structure of  FIG. 11 . 
     
    
    
     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. 
     Exemplary Embodiment 1 
       FIG. 1  illustrates an embodiment of a wireless communication device  200  using a first exemplary antenna structure  100 . The wireless communication device  200  can be a mobile phone or a personal digital assistant, for example. The antenna structure  100  can receive and send wireless signals. 
     Per  FIG. 2 , the antenna structure  100  includes a housing  11 , a first feed portion S 1 , a first ground portion G 1 , a second ground portion G 2 , and a radiator  13 . The housing  11  can be a metal housing of the wireless communication device  200 . In this exemplary embodiment, the housing  11  is a frame structure and is made of metallic material. The housing  11  includes a front frame  111 , a backboard  112 , and a side frame  113 . The front frame  111 , the backboard  112 , and the side frame  113  can be integral with each other. The front frame  111 , the backboard  112 , and the side frame  113  cooperatively form the metal housing of the wireless communication device  200 . 
     The front frame  111  defines an opening (not shown) thereon. The wireless communication device  200  includes a display  201 . The display  201  is received in the opening. The display  201  has a display surface. The display surface is exposed at the opening and is positioned parallel to the backboard  112 . 
     The backboard  112  is positioned opposite to the front frame  111 . The backboard  112  is directly connected to the side frame  113  and there is no gap between the backboard  112  and the side frame  113 . In this exemplary embodiment, the backboard  112  serves as a ground of the antenna structure  100  and the wireless communication device  200 . 
     The side frame  113  is positioned between the front frame  111  and the backboard  112 . The side frame  113  is positioned around a periphery of the front frame  111  and a periphery of the backboard  112 . The side frame  113  forms a receiving space  114  together with the display  201 , the front frame  111 , and the backboard  112 . The receiving space  114  can receive a printed circuit board, a processing unit, or other electronic components or modules. 
     The side frame  113  includes an end portion  115 , a first side portion  116 , and a second side portion  117 . In this exemplary embodiment, the end portion  115  is a top portion of the wireless communication device  200 . The end portion  115  connects the front frame  111  and the backboard  112 . The first side portion  116  is positioned apart from and parallel to the second side portion  117 . The end portion  115  has first and second ends. The first side portion  116  is connected to the first end of the first frame  111  and the second side portion  117  is connected to the second end of the end portion  115 . The first side portion  116  connects the front frame  111  and the backboard  112 . The second side portion  117  also connects the front frame  111  and the backboard  112 . 
     The side frame  113  defines a slot  118 . The front frame  111  defines a gap  119 . In this exemplary embodiment, the slot  118  is defined at the end portion  115  and extends to the first side portion  116  and the second portion  117 . In other exemplary embodiments, the slot  118  is only defined at the end portion  115  and does not extend to any one of the first side portion  116  and the second portion  117 . In other exemplary embodiments, the slot  118  can be defined at the end portion  115  and extend to one of the first side portion  116  and the second portion  117 . 
     The gap  119  communicates with the slot  118  and extends across the front frame  111 . The gap  119  and the slot  118  cooperatively form a T-shaped structure. In this exemplary embodiment, the gap  119  is positioned adjacent to the second side portion  117 . The front frame  111  is divided into two portions by the slot  118  and the gap  119 . The two portions are a long portion A 1  and a short portion A 2  (long and short relative to each other). A first portion of the front frame  111  extends from a first side of the gap  119  to a first end E 1  of the slot  118  forms the long portion A 1 . A second portion of the front frame  111  extends from a second side of the gap  119  to a second end E 2  of the slot  118  forms the short portion A 2 . 
     In this exemplary embodiment, the gap  119  is not positioned at a middle portion of the end portion  115 . The long portion A 1  is longer than the short portion A 2 . 
     In this exemplary embodiment, the slot  118  and the gap  119  are both filled with insulating material, for example, plastic, rubber, glass, wood, ceramic, or the like, thereby isolating the long portion A 1 , the short portion A 2 , and the other parts of the housing  11 . 
     In this exemplary embodiment, the slot  118  is defined on the end of the side frame  113  adjacent to the backboard  112  and extends to the front frame  111 . Then the long portion A 1  and the short portion A 2  are fully formed by a portion of the front frame  111 . In other exemplary embodiments, a position of the slot  118  can be adjusted. For example, the slot  118  is defined on the end of the side frame  113  adjacent to the backboard  112  and extends towards the front frame  111 . Then the long portion A 1  and the short portion A 2  are formed by a portion of the front frame  111  and a portion of the side frame  113 . 
     In this exemplary embodiment, except for the slot  118  and the gap  119 , an upper half portion of the front frame  111  and the side frame  113  does not define any other slot, break line, and/or gap. That is, there is only one gap  119  defined on the upper half portion of the front frame  111 . 
     Per  FIG. 2 , in this exemplary embodiment, the first feed portion S 1  is positioned in the receiving space  114  and is positioned adjacent to the gap  119 . One end of the first feed portion S 1  is electrically connected to the long portion A 1  for feeding current to the long portion A 1 . Another end of the first feed portion S 1  is electrically connected to the backboard  112  as the ground connection. 
     The first ground portion G 1  and the second ground portion G 2  are positioned in the receiving space  114  and are positioned adjacent to each other. The first ground portion G 1  is positioned adjacent to the first side portion  116 . One end of the first ground portion G 1  is electrically connected to the long portion A 1 . Another end of the first ground portion G 1  is electrically connected to backboard  112  for grounding the long portion A 1 . The second ground portion G 2  is positioned between the first feed portion S 1  and the first ground portion G 1 . One end of the second ground portion G 2  is electrically connected to the long portion A 1 . Another end of the second ground portion G 2  is electrically connected to backboard  112  for grounding the long portion A 1 . 
     The radiator  13  is positioned in the receiving space  114  and is positioned adjacent to the short portion A 2 . The radiator  13  includes a second feed portion S 2 , a third ground portion G 3 , a first radiating portion  131 , and a second radiating portion  133 . The second feed portion S 2  is positioned in the receiving space  114  and is positioned adjacent to the second side portion  117 . One end of the second feed portion S 2  is electrically connected to the first radiating portion  131  and the second radiating portion  133  for feeding current to the first radiating portion  131  and the second radiating portion  133 . Another end of the second feed portion S 2  is electrically connected to backboard  112  to be grounded. The third ground portion G 3  is substantially rectangular and is positioned in the receiving space  114 . The third ground portion G 3  is positioned adjacent to the gap  119  and is spaced apart from the second feed portion S 2 . 
     The first radiating portion  131  is substantially rectangular and is positioned at a plane parallel to the plane of the backboard  112 . The first radiating portion  131  is electrically connected to the end of the second feed portion S 2  away from the backboard  112  and extends along a direction parallel to the end portion  115  towards the first side portion  116 . 
     The second radiating portion  133  is substantially L-shaped and includes a first radiating section  135  and a second radiating section  137 . The first radiating section  135  is substantially rectangular and is coplanar with the first radiating portion  131 . One end of the first radiating section  135  is electrically connected to a junction of the second feed portion S 2  and the first radiating portion  131 . Another end of the first radiating section  135  extends along a direction parallel to the second side portion  117  towards the short portion A 2 . The second radiating section  137  is substantially rectangular and is coplanar with the first radiating section  135 . The second radiating section  137  is electrically connected to the end of the first radiating section  135  away from the second feed portion S 2  and extends along a direction parallel to the end portion  115  towards the first side portion  116  until the second radiating section  137  is electrically connected to the end of the third ground portion G 3  away from the backboard  112 . 
     In this exemplary embodiment, the second radiating section  137  is longer than the first radiating section  135 . The first radiating portion  131  is longer than the second radiating portion  133 . The second radiating portion  133  is spaced apart from the short portion A 2 . 
     Per  FIG. 2  and  FIG. 3 , in this exemplary embodiment, the wireless communication device  200  includes at least one electronic element. In this exemplary embodiment, the wireless communication device  200  includes at least five electronic elements, that is, a first electronic element  202 , a second electronic element  203 , a third electronic element  204 , a fourth electronic element  205 , and a fifth electronic element  206 . In this exemplary embodiment, the first electronic element  202  and the second electronic element  203  are both rear camera modules. The first electronic element  202  and the second electronic element  203  are positioned between the first ground portion G 1  and the second portion G 2 . The first electronic element  202  and the second electronic element  203  are spaced apart from each other. The third electronic element  204  is a speaker module. The third electronic element  204  is positioned between the first feed portion S 1  and the second electronic element  203 . The fourth electronic element  205  is a front camera module. The fourth electronic element  205  is positioned between the first feed portion S 1  and the second feed portion S 2 . The fifth electronic element  206  is a flash light. 
     Per.  FIG. 2 , the backboard  112  is an integral and single metallic sheet. Except the holes  207 ,  208 , and  209  for exposing two camera lenses (that is, the first electronic element  202  and the second electronic element  203 ) and the flash light (that is, the fifth electronic element  206 ), the backboard  112  does not define any other slot, break line, and/or gap. 
     In this exemplary embodiment, when current enters from the first feed portion S 1 , the current flows through the long portion A 1  and is grounded by the position of the long portion A 1  adjacent to the first end E 1 , the first ground portion G 1 , and the second ground portion G 2 . This activates a first operation mode for generating radiation signals in a first frequency band. In this exemplary embodiment, the first operation mode is LTE-A low, middle, and high frequency modes. The first frequency band includes frequency bands of about 704-787 MHz, 824-960 MHz, and 1710-2690 MHz. When the current enters from the first feed portion S 1 , the current flows through the long portion A 1  and is grounded by the position of the long portion A 1  adjacent to the first end E 1 , to generate radiation signals in a frequency band of about 704-787 MHz. When the current enters from the first feed portion S 1 , the current flows through the long portion A 1  and is grounded by the first ground portion G 1 , to generate radiation signals in a frequency band of about 824-960 MHz. When the current enters from the first feed portion S 1 , the current flows through the long portion A 1  and is grounded by the second ground portion G 2 , to generate radiation signals in a frequency band of about 1710-2690 MHz. 
     When the current enters from the second feed portion S 2 , the current flows through the first radiating portion  131 . The second feed portion S 2  and the first radiating portion  131  cooperatively form a monopole antenna. This activates a second operation mode for generating radiation signals in a second frequency band. When the current enters from the second feed portion S 2 , the current flows through the first radiating section  135  and the second radiating section  137  of the second radiating portion  133 , and is grounded by the third ground portion G 3 . 
     The second feed portion S 2 , second radiating portion  133 , and the third ground portion G 3  cooperatively form a loop antenna to activate a third operation mode for generating radiation signals in a third frequency band. When the current enters from the second feed portion S 2 , the current flows through the second radiating portion  133 , and is electronically coupled to short portion A 2  through the second radiating portion  133 . The current is grounded because of the position of the short portion A 2  adjacent to the second end E 2 , and this activates a fourth operation mode for generating radiation signals in a fourth frequency band. In this exemplary embodiment, the second operation mode is a WIFI 2.4G operation mode. The third operation mode is a WIFI 5G operation mode. The fourth operation mode is a GPS operation mode. 
     Per  FIG. 1  and  FIG. 4 , in other exemplary embodiments, the antenna structure  100  further includes a first switching circuit  15  and a second switching circuit  16 . One end of the first switching circuit  15  is electrically connected to the first ground portion G 1 , thus the first switching circuit  15  is electrically connected to the long portion A 1  through the first ground portion G 1 . Another end of the first switching circuit  15 , electrically connected to backboard  112 , is grounded. One end of the second switching circuit  16  is electrically connected to the second ground portion G 2 , thus the second switching circuit  16  is electrically connected to the long portion A 1  through the second ground portion G 2 . Another end of the second switching circuit  16  is electrically connected to backboard  112 , and thus is grounded. 
     Per  FIG. 5 , the first switching circuit  15  includes a first switching unit  151  and a plurality of first switching elements  153 . The first switching unit  151  is electrically connected to the first ground portion G 1  and is electrically connected to the long portion A 1  through the first ground portion G 1 . The first switching elements  153  can be an inductor, a capacitor, or a combination of the inductor and the capacitor. 
     The first switching elements  153  are connected in parallel to each other. One end of each first switching element  153  is electrically connected to the first switching unit  151 . The other end of each first switching element  153  is electrically grounded to the backboard  112 . 
     Per  FIG. 6 , the second switching circuit  16  includes a second switching unit  161  and a plurality of second switching elements  163 . The second switching unit  161  is electrically connected to the second ground portion G 2  and is electrically connected to the long portion A 1  through the second ground portion G 2 . The second switching elements  163  can be an inductor, a capacitor, or a combination of the inductor and the capacitor. The second switching elements  163  are connected in parallel to each other. One end of each second switching element  163  is electrically connected to the second switching unit  161 . The other end of each second switching element  163  is electrically grounded to the backboard  112 . 
     Through controlling the first switching unit  151  and the second switching unit  161 , the long portion A 1  can be switched to connect with different first switching elements  153  and/or second switching elements  163 . Since each first switching element  153  and second switching element  163  has a different impedance, an operating frequency band of the first operation mode of the long portion A 1  can be adjusted through switching the first switching unit  151  and the second switching unit  161 . For example, the frequency band of the first mode of the long portion A 1  can be offset towards a lower frequency or towards a higher frequency (relative to each other). 
     In this exemplary embodiment, the first switching circuit  15  and the second switching circuit  16  can be switched independently or together. The first switching circuit  15  is mainly used to switch a low frequency band of the first frequency band (704-787 MHz and 824-960 MHz). The second switching circuit  16  is mainly used to switch a middle frequency band and a high frequency band of the first frequency band (1710-2690 MHz). 
     In other exemplary embodiments, the wireless communication device  200  further includes a shielding mask or a middle frame (not shown). The shielding mask is positioned at the surface of the display  201  towards the backboard  112  and is configured for shielding against electromagnetic interference. The middle frame is positioned at the surface of the display  201  towards the backboard  112  and is configured for supporting the display  201 . The shielding mask or the middle frame is made of metallic material. The shielding mask or the middle frame is electrically connected to the backboard  112  and serves as ground of the antenna structure  100  and the wireless communication device  200 . A ground point can be electrically connected to the shielding mask, the middle frame, or the backboard  112 . 
       FIG. 7  illustrates a scattering parameter graph of the antenna structure  100 , when the antenna structure  100  works at the first operation mode. Curve  71  illustrates a scattering parameter when the antenna structure  100  works at an LTE-A Band  17 / 13  (704-787 MHz). Curve  72  illustrates a scattering parameter when the antenna structure  100  works at an LTE-A Band  5 / 8  (824-960 MHz). Curve  73  illustrates a scattering parameter when the antenna structure  100  works at a frequency band of about 1710-2690 MHz. 
       FIG. 8  illustrates a radiating efficiency graph of the antenna structure  100 , when the antenna structure  100  works at the first operation mode. Curve  81  illustrates a radiating efficiency when the antenna structure  100  works at an LTE-A Band  17 / 13  (704-787 MHz). Curve  82  illustrates a radiating efficiency when the antenna structure  100  works at an LTE-A Band  5 / 8  (824-960 MHz). Curve  83  illustrates a radiating efficiency when the antenna structure  100  works at a frequency band of about 1710-2690 MHz. 
       FIG. 9  illustrates a scattering parameter graph of the antenna structure  100 , when the antenna structure  100  works at the GPS operation mode, WIFI 2.4G operation mode, and WIFI 5G operation mode. Curve  91  illustrates a scattering parameter when the antenna structure  100  works at the GPS band and the WIFI 2.4G band. Curve  92  illustrates a scattering parameter when the antenna structure  100  works at the WIFI 5G band. 
       FIG. 10  illustrates a radiating efficiency graph of the antenna structure  100 , when the antenna structure  100  works at the GPS operation mode, WIFI 2.4G operation mode, and WIFI 5G operation mode. Curve  101  illustrates a radiating efficiency when the antenna structure  100  works at the GPS band and the WIFI 2.4G band. Curve  102  illustrates a radiating efficiency when the antenna structure  100  works at the WIFI 5G band. 
     Per  FIGS. 7 to 10 , the antenna structure  100  can work at a low frequency band, for example, LTE-A band  17 / 13 / 5 / 8 . The antenna structure  100  can also work at LTE-A middle and high frequency bands of about 1710-2690 MHz, the GPS band (1.575 GHz), the WIFI 2.4G band, and the WIFI 5G band. When the antenna structure  100  works at these frequency bands, a working frequency satisfies a design target of the antenna and also has a good radiating efficiency. 
     As described above, the antenna structure  100  defines the slot  118  and the gap  119 , then the housing  11  is divided into a long portion A 1 . The antenna structure  100  further includes the first feed portion S 1 , the first ground portion G 1 , and the second ground portion G 2 . The long portion A 1  can activate a first operation mode to generate radiation signals in low, middle, and high frequency bands. The wireless communication device  200  can use carrier aggregation (CA) technology of LTE-A to receive or send wireless signals at multiple frequency bands simultaneously. In detail, the wireless communication device  200  can use the CA technology and use the long portion A 1  to receive or send wireless signals at multiple frequency bands simultaneously. 
     In addition, the antenna structure  100  includes the housing  11 . The slot  118  and the gap  119  are both defined on the front frame  111  and the side frame  113  instead of the backboard  112 . Then the backboard  112  forms an all-metal structure. That is, the backboard  112  does not define any slot and/or gap thereon and therefore has a good structural integrity and an aesthetic quality. 
     Exemplary Embodiment 2 
       FIG. 11  illustrates an embodiment of a wireless communication device  400  using a second exemplary antenna structure  300 . The wireless communication device  400  can be a mobile phone or a personal digital assistant, for example. The antenna structure  300  can receive and send wireless signals. 
     Per  FIG. 12 , the antenna structure  300  includes a housing  31 , a feed portion  32 , and a ground portion  33 . The housing  31  can be a metal housing of the wireless communication device  400 . In this exemplary embodiment, the housing  31  is a frame structure and is made of metallic material. The housing  31  includes a front frame  311 , a backboard  312 , and a side frame  313 . The front frame  311 , the backboard  312 , and the side frame  313  can be integral with each other. The front frame  311 , the backboard  312 , and the side frame  313  cooperatively form the metal housing of the wireless communication device  400 . 
     The front frame  311  defines an opening (not shown). The wireless communication device  400  includes a display  401 . The display  401  is received in the opening. The display  401  has a display surface. The display surface is exposed at the opening and is positioned parallel to the backboard  312 . 
     The backboard  312  is positioned opposite to the front frame  311 . The backboard  312  is directly connected to the side frame  313  and there is no gap between the backboard  312  and the side frame  313 . In this exemplary embodiment, the backboard  312  serves as ground connection of the antenna structure  300  and the wireless communication device  400 . 
     The side frame  313  is positioned between the front frame  311  and the backboard  312 . The side frame  313  is positioned around a periphery of the front frame  311  and a periphery of the backboard  312 . The side frame  313  forms a receiving space  314  together with the display  401 , the front frame  311 , and the backboard  312 . The receiving space  314  can receive a printed circuit board, a processing unit, or other electronic components or modules. 
     The side frame  313  includes an end portion  315 , a first side portion  316 , and a second side portion  317 . In this exemplary embodiment, the end portion  315  is a bottom portion of the wireless communication device  400 . The end portion  315  connects the front frame  311  and the backboard  312 . The first side portion  316  is positioned apart from and parallel to the second side portion  317 . The end portion  315  has first and second ends. The first side portion  316  is connected to the first end of the first frame  311  and the second side portion  317  is connected to the second end of the end portion  315 . The first side portion  316  connects the front frame  311  and the backboard  312 . The second side portion  317  also connects the front frame  311  and the backboard  312 . 
     The side frame  313  defines a first through hole  318 , a second through hole  319 , and a slot  318 . The front frame  311  defines a first gap  321  and a second gap  322 . 
     In this exemplary embodiment, the first through hole  318  and the second through hole  319  are both defined on the end portion  315 . The first through hole  318  and the second through hole  319  are spaced apart from each other and both pass through the end portion  315 . 
     Per  FIG. 12  and  FIG. 13 , the wireless communication device  400  includes at least one electronic element. In this exemplary embodiment, the wireless communication device  400  includes a first electronic element  402 , a second electronic element  403 , a third electronic element  404 , a fourth electronic element  405 , and a fifth electronic element  406 . In this exemplary embodiment, the first electronic element  402  is an earphone interface module. The first electronic element  402  is positioned in the receiving space  314  and is positioned adjacent to the second side portion  317 . The first electronic element  402  corresponds to the first through hole  318  and is partially exposed from the first through hole  318 . An earphone can thus be inserted in the first through hole  318  and be electrically connected to the first electronic element  402 . 
     The second electronic element  403  is a Universal Serial Bus (USB) module. The second electronic element  403  is positioned in the receiving space  314  and is positioned between the first electronic element  402  and the second side portion  317 . 
     The second electronic element  403  corresponds to the second through hole  319  and is partially exposed from the second through hole  319 . A USB device can be inserted in the second through hole  319  and be electrically connected to the second electronic element  403 . The third electronic element  404  and the fourth electronic element  405  are both rear camera modules. The fifth electronic element  406  is a flash light. 
     In this exemplary embodiment, the backboard  312  is an integral and single metallic sheet. Except the holes  407 ,  408 , and  409  for exposing two camera lenses (that is, the third electronic element  404  and the fourth electronic element  405 ) and the flash light (that is, the fifth electronic element  406 ), the backboard  312  does not define any other slot, break line, and/or gap. 
     In this exemplary embodiment, the slot  320  is defined at the end portion  315  and extends to the first side portion  316  and the second portion  317 . The slot  320  communicates with the first through hole  318  and the second through hole  319 . In other exemplary embodiments, the slot  320  can only be defined at the end portion  315  and does not extend to any one of the first side portion  316  and the second portion  317 . In other exemplary embodiments, the slot  320  can be defined at the end portion  315  and extends to one of the first side portion  316  and the second portion  317 . 
     The first gap  321  and the second gap  322  both communicate with the slot  320  and extend across the front frame  311 . In this exemplary embodiment, the first gap  321  is defined on the front frame  311  and communicates with a first end E 1  of the slot  320  positioned on the first side portion  316 . The second gap  322  is defined on the front frame  311  and communicates with a second end E 2  of the slot  320  positioned on the second side portion  317 . The front frame  311  is divided into two portions by the slot  320 , the first gap  321 , and the second gap  322 , these portions being a first radiating portion T 1  and a second radiating portion T 2 . The portion of the front frame  311  surrounded by the slot  320 , the first gap  321 , and the second gap  322  forms the first radiating portion T 1 . The portion of the side frame  313  surrounded by the slot  320  and the backboard  312  forms the second radiating portion T 2 . In this exemplary embodiment, the first radiating portion T 1  and the second radiating portion T 2  both form antenna structures for receiving and sending wireless signals. 
     In this exemplary embodiment, the second radiating portion T 2  is substantially T-shaped and is part of the end portion  315 . The second radiating portion T 2  includes a connecting section T 21 , a first radiating section T 22 , and a second radiating section T 23 . The connecting section T 21  is substantially rectangular and is positioned between the first radiating portion T 1  and the backboard  312 . The first radiating section T 22  is perpendicularly connected to the side of the connecting section T 21  adjacent to the first side portion  316  and extends along a direction parallel to the end portion  315  towards the first side portion  316 . The second radiating section T 23  is substantially rectangular. The second radiating section T 23  is positioned between the first radiating portion T 1  and the backboard  312 . The second radiating section T 23  is perpendicularly connected to a junction between the connecting section T 21  and the first radiating section T 22  and extends along a direction parallel to the end portion  315  towards the second side portion  317 . The second radiating section T 23  is collinear with the first radiating section T 22 . The connecting section T 21 , the first radiating section T 22 , and the second radiating section T 23  cooperatively form a T-shaped structure. 
     In this exemplary embodiment, the slot  320 , the first gap  321 , and the second gap  322  are all filled with insulating material, for example, plastic, rubber, glass, wood, ceramic, or the like, thereby isolating the first radiating portion T 1  and the other parts of the housing  31 . 
     In this exemplary embodiment, the slot  320  is defined on the end of the side frame  313  adjacent to the backboard  312  and extends to the front frame  311 . Then the first radiating portion T 1  is fully formed by a portion of the front frame  311 . In other exemplary embodiments, a position of the slot  320  can be adjusted. For example, the slot  320  can be defined on the end of the side frame  313  adjacent to the backboard  312  and extend towards the front frame  311 . Then the first radiating portion T 1  is formed by a portion of the front frame  311  and a portion of the side frame  313 . 
     In this exemplary embodiment, a distance from the first radiating section T 22  and the second radiating section T 23  to the front frame  311  is about 1.83 mm. A width of the first radiating section T 22  and the second radiating section T 23  is about 1 mm. A distance from the first radiating section T 22  and the second radiating section T 23  to the backboard  312  is about 1 mm. 
     Per  FIG. 12 , the feed portion  12  is positioned in the receiving space  314  between the second electronic element  403  and the first side portion  316 . One end of the feed portion  12  is electrically connected to the first radiating portion T 1  for feeding current to the first radiating portion T 1 . Another end of the feed portion  12  is electrically grounded to the backboard  312 . 
     The ground portion  33  is positioned in the receiving space  314  between the second electronic element  403  and the feed portion  12 . One end of the ground portion  33  is electrically connected to the first radiating portion T 1  for grounding the first radiating portion T 1 . Another end of the ground portion  33  is electrically grounded to the backboard  312 . 
     Per  FIG. 12 , in other exemplary embodiments, the antenna structure  300  further includes a connecting portion  34 . The connecting portion  34  is positioned between the receiving space  314  and is positioned adjacent to the first side portion  316 . 
     One end of the connecting portion  34  is electrically connected to the first radiating portion T 1 . Another end of the connecting portion  34  is electrically connected to first radiating section T 22  for electrically connecting the first radiating portion T 1  and the first radiating section T 22 . The connecting portion  34  effectively adds the radiating length of the first radiating portion T 1 . Then the first radiating portion T 1  can operate at low and middle frequency bands. The connecting portion  34  also adjusts a capacitive reactance and an inductive reactance of the antenna structure  300 . Then the antenna structure  300  has wideband characteristics. In this exemplary embodiment, the connecting portion  34  is a Flexible Printed Circuit Board (FPCB). A frequency band of the antenna structure  300  can be adjusted by changing the connecting portion  34 , the structures of the first radiating portion T 1  and the second radiating portion T 2  do not need to be changed. 
     Per  FIG. 15 , when the current enters from the feed portion  32 , the current flows through the first radiating portion T 1  and flows to the first radiating section T 22  through the connecting portion  34 . The current is further grounded through the connecting section T 21  and the backboard  312 . Then the first radiating portion T 1 , the connecting portion  34 , and the first radiating section T 22  cooperatively activate a first operation mode for generating radiation signals in a first frequency band (the path P 1 ). In this exemplary embodiment, the first operation mode is LTE-A low and middle frequency modes. The first frequency band includes frequency bands of about 704-960 MHz and 1710-2300 MHz. A resonance current path of the LTE-A low frequency band includes the first radiating portion T 1 . A resonance current path of the LTE-A middle frequency band only includes the portion of the first radiating portion T 1  from the feed portion  32  to the first gap  321 . 
     Per  FIG. 16 , when the current enters from the feed portion  32 , the current flows through the portion of the first radiating portion T 1  adjacent to the connecting portion  34  and flows to the first radiating section T 22  and the second radiating section T 23  through the connecting portion  34 . The current is further coupled to the first radiating portion T 1  through the second radiating section T 23  and is grounded through the ground portion  33 . Then the first radiating portion T 1  and the second radiating section T 23  cooperatively activate a second operation mode for generating radiation signals in a second frequency band (Per the path P 2 ). In this exemplary embodiment, the second operation mode is an LTE-A high frequency band. The second frequency band includes a frequency band of about 2500-2690 MHz. 
     Per  FIG. 12  and  FIG. 14 , in other exemplary embodiments, the antenna structure  300  further includes a switching circuit  35 . The switching circuit  35  is positioned in the receiving space  314 . One end of the switching circuit  35  is electrically connected to the ground portion  33 , thus the switching circuit  35  is electrically connected to the first radiating portion T 1  through the ground portion  33 . Another end of the switching circuit  35  is electrically grounded to backboard  312 . 
     Per  FIG. 17 , the switching circuit  35  includes a switching unit  351  and a plurality of switching elements  353 . The switching unit  351  is electrically connected to the first radiating portion T 1  through the ground portion  33 . The switching elements  353  can be an inductor, a capacitor, or a combination of the inductor and the capacitor. The switching elements  353  are connected in parallel. One end of each switching element  353  is electrically connected to the switching unit  351 . The other end of each switching element  353  is electrically grounded to the backboard  312 . Through controlling the switching unit  351 , the first radiating portion T 1  can be switched to connect with different switching elements  353 . Since each switching element  353  has a different impedance, an operating frequency band of the antenna structure  300  can be adjusted through switching the switching unit  351 . 
     In other exemplary embodiments, the wireless communication device  400  further includes a shielding mask or a middle frame (not shown). The shielding mask is positioned at the surface of the display  401  towards the backboard  312  and shields against electromagnetic interference. The middle frame is positioned at the surface of the display  401  towards the backboard  312  and is configured for supporting the display  401 . The shielding mask or the middle frame is made of metallic material. The shielding mask or the middle frame is electrically connected to the backboard  312  and serves as the ground of the antenna structure  300  and the wireless communication device  400 . In above grounding points, the shielding mask or the middle frame can replace the backboard  312  for grounding purposes. 
       FIG. 18  and  FIG. 19  illustrate a scattering parameter graph of the antenna structure  300 . Curve  161  and curve  171  illustrate a scattering parameter when the antenna structure  300  works at a first mode, in frequency bands of about 824-894 MHz and 1710-1880 MHz. Curve  162  and curve  172  illustrate a scattering parameter when the antenna structure  300  works at a second mode, in frequency bands of about 880-960 MHz and 2300-2400 MHz. Curve  163  illustrates a scattering parameter when the antenna structure  300  works at a third mode, in a frequency band of about 703-803 MHze. Curve  173  illustrates a scattering parameter when the antenna structure  300  works at a fourth mode, in a frequency band of about 1710-2170 MHz. 
       FIG. 20  and  FIG. 21  illustrate a radiating gain graph of the antenna structure  300 . Curve  181  and curve  191  illustrate a radiating gain when the antenna structure  300  works at the first mode, in frequency bands of about 824-894 MHz and 1710-1880 MHz. Curve  182  and curve  192  illustrate a radiating gain when the antenna structure  300  works at the second mode, in frequency bands of about 880-960 MHz and 2300-2400 MHz. Curve  183  illustrates a radiating gain when the antenna structure  300  works at the third mode, in a frequency band of about 703-803 MHz. Curve  193  illustrates a radiating gain when the antenna structure  300  works at the fourth mode, in a frequency band of about 1710-2170 MHz. 
     Per  FIGS. 18 to 21 , the antenna structure  300  can work at a low frequency band, a middle frequency band, and a high frequency band, for respective frequencies of 704-960 MHz, 1710-2300 MHz, and 2500-2690 MHz. When the antenna structure  300  works at these frequency bands, a working frequency satisfies a design target of the antenna and also has a good radiating efficiency. Additionally, when the antenna structure  300  includes the switching circuit  35 , since the first radiating portion T 1  and the second radiating section T 23  cooperatively control the high frequency band, the high frequency band of the antenna structure  300  is always activated, no matter which of the first to fourth modes the switching circuit  35  is switched to. 
     As described above, the antenna structure  300  defines the slot  320 , the first gap  321 , and the second gap  322 , then the housing  31  is divided into the first radiating portion T 1  and the second radiating portion T 2 . The antenna structure  300  further includes the feed portion  32 , the connecting portion  34 , and the switching circuit  35 , then the antenna structure  300  can activate a first operation mode and a second operation mode to generate radiation signals in a low frequency band, a middle frequency band, and a high frequency band. The wireless communication device  400  can use carrier aggregation (CA) technology of LTE-A to receive and send wireless signals at multiple frequency bands simultaneously. In detail, the wireless communication device  400  can use the CA technology and use the first radiating portion T 1  and the second radiating portion T 2  to receive and send wireless signals at multiple frequency bands simultaneously. 
     In addition, the antenna structure  300  includes the housing  31 . The slot  320 , the first gap  321 , and the second gap  322  are all defined on the front frame  311  and the side frame  313  instead of on the backboard  312 . Then the backboard  312  forms a single all-metal structure. That is, the backboard  312  does not define any other slot and/or gap and has a good integrity structural and an aesthetic quality. 
     The antenna structure  100  of exemplary embodiment  1  and the antenna structure  300  of exemplary embodiment  2  can both be applied to one wireless communication device. For example, the antenna structure  100  can serve as an upper antenna of the wireless communication device and the antenna structure  300  can serve as a lower antenna of the wireless communication device. When the wireless communication device sends wireless signals, the wireless communication device can use the antenna structure  300  to send wireless signals. When the wireless communication device receives wireless signals, the wireless communication device can use the antenna structure  100  and antenna structure  300  to receive wireless signals. 
     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 technology 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.