Patent Publication Number: US-2019181565-A1

Title: Antenna system and mobile terminal

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to Chinese Patent Application No. 201711326394.X, filed on Dec. 13, 2017, the content of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to the field of electronic technologies and, in particular, to an antenna system and a mobile terminal. 
     BACKGROUND 
     The International Telecommunication Union (ITU) defined main application scenarios of 5G at the ITU-RWPSD 22nd meeting held on June 2015. The ITU defined three main application scenarios: enhanced mobile broadband, large-scale machine communications, and highly-reliable low-latency communications. These three application scenarios respectively correspond to different key indicators. Under the enhanced mobile bandwidth scenario, the user peak speed is 20 Gbps, and the minimum user experience rate is 100 Mbps. In order to achieve these rigorous indexes, several key techniques will be utilized, including the millimeter wave technique. 
     Rich bandwidth resources of a millimeter wave frequency band provide guarantees for high-speed transmission rates. However, due to the severe space loss of electromagnetic waves at this frequency band, phased array architecture is needed for a wireless communication system using the millimeter wave frequency band. By means of a phase shifter, the phases of various array elements are distributed according to a certain rule, thereby forming a high-gain beam. In addition, by changing the phase shift, the beam is scanned within a certain space range. However, the scanning coverage of a single millimeter wave array antenna is generally smaller than a hemisphere (half space under a sphere coordinate system), if a terminal such as a cellphone adopts a single millimeter wave array antenna, it may cause a problem that the signal is unstable. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Many aspects of the exemplary embodiment can be better understood with reference to the following drawings. The components in the drawings 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 schematic structural diagram of an antenna system in accordance with a first embodiment of the present disclosure; 
         FIG. 2  is a schematic layout diagram of the antenna system in a mobile terminal in accordance with the first embodiment of the present disclosure; 
         FIG. 3  is a schematic diagram of radiation beam pointing of the antenna system in accordance with the first embodiment of the present disclosure; 
         FIG. 4  is a pattern of a first millimeter wave array antenna on an H plane when respective first antenna units are fed at a constant amplitude and a same phase in the antenna system in accordance with the first embodiment; 
         FIG. 5  is a pattern of the first millimeter wave array antenna on an E plane when respective first antenna units are fed at a constant amplitude and a same phase in the antenna system in accordance with the first embodiment; 
         FIG. 6  is a schematic diagram illustrating relationships between gain values and coverage efficiencies of the antenna system in accordance with a first embodiment of the present disclosure; 
         FIG. 7  is a schematic layout diagram of an antenna system in a mobile terminal in accordance with a second embodiment of the present disclosure; and 
         FIG. 8  is a schematic layout diagram of an antenna system in a mobile terminal in accordance with a third embodiment of the present disclosure. 
     
    
    
     The drawings herein are incorporated into the description and constitute a part thereof, which show embodiments of the present disclosure and are used to explain principles of the present disclosure together with the description. 
     DESCRIPTION OF EMBODIMENTS 
     The present disclosure will be illustrated in further details with reference to the following description and the drawings. 
     First Embodiment 
     As shown in  FIGS. 1-2 , a first embodiment of the present disclosure provides an antenna system  1 , which can be applied to a mobile terminal  10  such as a cellphone. The antenna system  1  includes a circuit board  10 , a first feeding point  102  and a second feeding point  104  that are arranged on the circuit board  10 , a first millimeter wave array antenna  12  electrically connected to the first feeding point  102 , and a second millimeter wave array antenna  14  electrically connected to the second feeding point  104 . 
     The first millimeter wave array antenna  12  includes a first feeding network  122  electrically connected to the first feeding point  102 , and a first antenna array face  124  fed by the first feeding network  122 . 
     The second millimeter wave array antenna  14  includes a second feeding network  142  electrically connected to the second feeding point  104 , and a second antenna array face  144  fed by the second feeding network  142 . 
     As shown in  FIG. 3 , the mobile terminal  10  in the present disclosure has a length direction, a width direction and a thickness direction. In the three-dimensional coordinate system, as shown in  FIG. 3 , the length direction of the mobile terminal  10  is a direction where the X axis of the three-dimensional coordinate system is located, the width direction of the mobile terminal  10  is a direction where the Y axis of the three-dimensional coordinate system is located, and the thickness direction of the mobile terminal  10  is a direction where the Z axis of the three-dimensional coordinate system is located. The size of the mobile terminal  10  in the length direction is greater than the size of the mobile terminal  10  in the width direction, and the size of the mobile terminal  10  in the width direction is greater than the size of the mobile terminal  10  in the thickness direction. 
     In the present embodiment, the first antenna array face  124  and the second antenna array face  144  are respectively arranged on opposite sides of the mobile terminal  10  along the width direction, and each of the first antenna units  124   a  and each of the second antenna units  144   a  are distributed along the length direction of the mobile terminal  10 . That is to say, the first antenna array face  124  and the second antenna array face  144  are arranged on the long side of the mobile terminal  10 . 
     The above mobile terminal  10  has a top and a bottom, and the top and the bottom are arranged opposite to each other along the length direction of the mobile terminal  10 . It should be noted that, the bottom of the mobile terminal  10  is generally closer to the handhold portion of the user. In order to reduce the influence on the antenna system  1  when the user is holding the mobile terminal  10 , the first and second antenna array faces  124 ,  144  can be arranged closer to the top than to the bottom during the design thereof. 
     In the present embodiment, the first antenna array face  124  includes a plurality of first antenna units  124   a,  and the first antenna units  124   a  are arranged into a one-dimensional linear array at intervals. Similarly, the second antenna array face  144  includes a plurality of second antenna units  144   a,  and the second antenna units  144   a  are arranged into a one-dimensional linear array at intervals. That is to say, both the first antenna array face  124  and the second antenna array face  144  are in the form of a one-dimensional linear array. 
     In the present embodiment, the above antenna array face (the first antenna array face  124  and the second antenna array face  144 ) can be made of a flexible circuit board, or can be made by LDS or LTCC processing, or can also be formed by a metal housing of the mobile terminal. For example, when the housing of the mobile terminal is made of metal, a portion of a side border of the housing can be made as the antenna array face. When the above antenna array face is made of a flexible circuit board, or made by LDS or LTCC technique, it can be attached onto the surface of the housing, or can be attached onto the surface of a non-metal support within the housing. 
     In the present embodiment, the first feeding network  122  includes a plurality of first phase shifters  122   a.  The number of the plurality of first phase shifters  122   a  is the same as the number of the first antenna units  124   a.  Each first antenna unit  124   a  is connected to the first feeding point  102  through one first phase shifter  122   a.  The first phase shifter  122   a  can control the feeding phase of the first antenna unit  124   a,  so as to realize beam scanning. Similarly, the second feeding network  142  includes a plurality of second phase shifters  142   a.  The number of the plurality of second phase shifters  142   a  is the same as the number of the second antenna units  144   a.  Each second antenna unit  144   a  is connected to the second feeding point  104  through one second phase shifter  142   a.  The second phase shifter  142   a  can control the feeding phase of the second antenna unit  144   a,  so as to achieve beam scanning. 
     Specifically, the radiation coverage of the first millimeter wave array antenna  12  covers a first half space, and the radiation coverage of the second millimeter wave array antenna  14  covers a second half space. The first half space and the second half space are complementary, and together form an omnidirectional space. That is to say, through arranging the first millimeter wave array antenna  12  and the second millimeter wave array antenna  14  in the mobile terminal  10 , omnidirectional radiation of the antenna system  1  can be achieved. 
     Based on the above structure, as shown in  FIG. 3 , the first millimeter wave array antenna  12  and the second millimeter wave array antenna  14  form a wide beam in the θ direction. By changing the phase shift of the phase shifter, the first millimeter wave array antenna  12  and the second millimeter wave array antenna  14  scan in the φ direction. To be specific, the first millimeter wave array antenna  12  scans in the range from φ=0° to φ=180° (the first half space), and the second millimeter wave array antenna  14  scans in the range from φ=180° to φ=360° (the second half space). It should be noted that, the first radiation beam  12   a  and the second radiation beam  14   a  in  FIG. 3  respectively show the radiation beam pointing of the first millimeter wave array antenna  12  and the second millimeter wave array antenna  14 . 
     When respective first antenna units  124   a  are fed at a constant amplitude and a same phase, the pattern of the first millimeter wave array antenna  12  on an H plane (yoz plane in the sphere coordinate system) is shown in  FIG. 4 , and the pattern of the first millimeter wave array antenna  12  on an E plane (xoy plane in the sphere coordinate system) is shown in  FIG. 5 . When respective second antenna units  144   a  are fed at a constant amplitude and a same phase, the second millimeter wave array antenna  14  has a pattern similar to the first millimeter wave array antenna  12 , except that its radiation beam pointing is opposite to that of the first millimeter wave array antenna  12 . 
     As shown in  FIG. 6 , when the first millimeter wave array antenna  12  and the second millimeter wave array antenna  14  are working at the same time, the coverage efficiency of the antenna system is much greater than the coverage efficiency when only one of the first and second millimeter wave array antennas  12 ,  14  is working. When the first and second millimeter wave array antennas  12 ,  14  are working at the same time and the gain is 5 dBi, the coverage efficiency is close to  1 , which means the antenna system can reach a beam coverage of 5 dBi in the omnidirectional space. 
     In the present embodiment, the number of the first antenna units  124   a  is 12, and the number of the second antenna units  144   a  is 12. Since the number of the first phase shifters  122   a  is the same as the number of the first antenna units  124   a  and the number of the second phase shifters  142   a  is the same as the number of the second antenna units  144   a,  the number of both the first phase shifters  122   a  and the second phase shifters  142   a  is 12. 
     It should be noted that, the number of the first antenna units  124   a  and the number of the second antenna units  144   a  is not limited to 12, and can also be 5, 6, 15, 16, etc. The specific number can be determined according to the accommodation space within the mobile terminal and the design requirements of the antenna system  1 . 
     In addition, both the first phase shifter  122   a  and the second phase shifter  142   a  can be 5 bit phase shifters with a phase precision of 11.25 degrees. 
     Second Embodiment 
     The second embodiment is generally the same as the first embodiment, except for the placement position of the antenna array face. As shown in  FIG. 7 ,  FIG. 7( a )  shows a front face of a mobile terminal  20  provided by the second embodiment, and  FIG. 7( b )  shows a rear face of the mobile terminal  20  provided by the second embodiment. In the second embodiment, two millimeter wave array antennas are provided, that is, a first millimeter wave array antenna  12  and a second millimeter wave array antenna  14 . The first antenna array face of the first millimeter wave array antenna  12  and the second antenna array face of the second millimeter wave array antenna  14  are respectively arranged on opposite sides of the mobile terminal  20  along the thickness direction, and the antenna units are arranged along the width direction of the mobile terminal  20 . The first antenna array face of the first millimeter wave array antenna  12  is arranged on the front face of the mobile terminal  20 , and the second antenna array face of the second millimeter wave array antenna  14  is arranged on the rear face of the mobile terminal  20 . The front face of the mobile terminal  20  refers to a side where the screen is located, and the rear face refers to a side where the back shell is located. In the present embodiment, the first antenna array face and the second antenna array face are closer to the top of the mobile terminal  20 , than to the bottom of the mobile terminal  20 . 
     In the present embodiment, the working principle of the antenna system is the same as the antenna system in the first embodiment. The first millimeter wave array antenna  12  achieves beam scanning in the space outward from the screen (the first half space), and the second millimeter wave array antenna  14  achieves beam scanning in the space outward from the back shell (the second half space). Through the cooperation of the first and second millimeter wave array antennas, the coverage efficiency of the entire antenna system can be improved, and thus the signal can be more stable. 
     Third Embodiment 
     The third embodiment is generally the same as the first embodiment and the second embodiment, except for the placement position of the antenna array face. As shown in  FIG. 8 , in the third embodiment, a mobile terminal  30  is provided, which includes two millimeter wave array antennas are provided, that is, a first millimeter wave array antenna  12  and a second millimeter wave array antenna  14 . The first antenna array face of the first millimeter wave array antenna  12  and the second antenna array face of the second millimeter wave array antenna  14  are respectively arranged on opposite sides of the mobile terminal  30  along the length direction, and the antenna units are arranged along the width direction of the mobile terminal  30 . The first antenna array face of the first millimeter wave array antenna  12  is arranged at the top of the mobile terminal  30 , and the second antenna array face of the second millimeter wave array antenna  14  is arranged at the bottom of the mobile terminal  30 . 
     In the present embodiment, the working principle of the antenna system is the same as the antenna system in the first embodiment and the second embodiment. The first millimeter wave array antenna  12  achieves beam scanning in the space outward from the top of the mobile terminal  30  (the first half space), and the second millimeter wave array antenna  14  achieves beam scanning in the space outward from the bottom of the mobile terminal  30  (the second half space). Through the cooperation of the first and second millimeter wave array antennas, the coverage efficiency of the entire antenna system can be improved, and thus the signal can be more stable. 
     The above are preferred embodiments of the present invention, which are not intended to limit the present invention, for person skilled in the art, the present invention can have various alternations and modifications. Any modification, equivalent replacement and improvement made within the spirit and principle of the present invention shall fall into the protection scope of the present invention.