Patent Publication Number: US-10777908-B2

Title: Millimeter wave array antenna and mobile terminal

Description:
FIELD OF THE PRESENT DISCLOSURE 
     The invention relates to the technical field of manufacturing of mobile terminals, particularly to a millimeter wave array antenna and a mobile terminal. 
     DESCRIPTION OF RELATED ART 
     The antenna is a key component which radiates electromagnetic energy into and receives electromagnetic energy from the space in wireless communication equipment. The antenna transmits digital signals or analog signals which are modulated to an RF frequency into the space wireless channel, or receives digital signals or analog signals which are modulated to an RF frequency from the space. 
     5G is the R&amp;D focus of the global industry. Developing 5G technology and making 5G standard are the common ideas of the industry. International Telecommunication Union (ITU) clearly specified the main application scenarios of 5G in the 22 md  ITU-RWP5D conference which was held in June, 2015. ITU defines three main application scenarios: enhanced mobile broadband, large-scale machine communication and high-reliability and low-delay communication. The three main application scenarios respectively match corresponding key indexes. In the scenario of the enhanced mobile broadband, the user peak velocity is 20 Gbps, and the minimum user experience rate is 100 Mbps. To meet these strict indexes, a plurality of key technologies, including the millimeter wave technology, are used. 
     With the fast development of the 5G technology in the communication field, the requirement on the data transmission efficiency becomes more and more higher. To meet the demand, the frequency range of the 5G network extends to the frequency range of the millimeter wave. Thus, more and more demands that the millimeter wave antenna works at the frequency range of 20 GHz are generated. 
     To meet application demands, the millimeter wave antenna is often designed into an array form, i.e., a plurality of same antenna units are applied to get high gain and compensate the increase of the loss of the free space path in the frequency range of the millimeter wave. In addition, in the frequency range of the millimeter wave, if the transmitter and receiver carry out NLOS communication, the communication link is interfered and even disrupted. Thus, to maintain horizon communication, the millimeter wave antenna shall be capable of radiating to the omnidirectional space. 
     Thus, a novel millimeter wave array antenna is necessary to be provided to solve the problems above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the exemplary embodiments can be better understood with reference to the following drawings. The components in the drawing are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. 
         FIG. 1 a    is an isometric view of a millimeter wave array antenna in accordance with an exemplary embodiment of the invention. 
         FIG. 1 b    is an illustrative view of metal grounding layers and a sandwich metal layer of the millimeter wave array antenna of the invention. 
         FIG. 1 c    is a front view of the structure in  FIG. 1 b    with a metal grounding layer moved. 
         FIG. 2 a    is an illustration of a radiation of an upper area of the millimeter wave array antenna of the invention. 
         FIG. 2 b    is an illustration of a radiation of a lower area of the millimeter wave array antenna of the invention. 
         FIG. 3 a    is an isometric view of a mobile terminal, with a metal back cover removed. 
         FIG. 3 b    is an isometric and exploded view of the mobile terminal. 
         FIG. 4 a    illustrates the radiation of a top area of the mobile terminal. 
         FIG. 4 b    illustrates the radiation of a bottom area of the mobile terminal. 
         FIG. 5 a    shows the reflection coefficients of a second slot antenna units of the invention. 
         FIG. 5 b    shows the isolation degree of all slot antenna units of the invention. 
         FIG. 5 c    illustrates the structure of the millimeter wave array antenna of the invention. 
         FIG. 6 a    is the radiation emulation three-dimensional visual angle view of the mobile terminal at the top area. 
         FIG. 6 b    is the radiation emulation side view of the mobile terminal at the top area. 
         FIG. 7 a    is the radiation emulation view of the mobile terminal when the difference of first slot antenna units is −150°. 
         FIG. 7 b    is the radiation emulation view of the mobile terminal when the difference of first slot antenna units is 0° of phase shift. 
         FIG. 7 c    is the radiation emulation view of the mobile terminal when the difference of first slot antenna units is 150° of phase shift. 
         FIG. 8  is a cross-sectional view which is used for observing the gain of the millimeter wave array antenna of the mobile terminal. 
         FIG. 9 a    is the emulation gain view of the top area, which is expressed in a rectangular coordinate way, of the mobile terminal. 
         FIG. 9 b    is the emulation gain view of the top area, which is expressed in a polar coordinate way, of the mobile terminal. 
         FIG. 10 a    is the radiation emulation three-dimensional visual angle view of the mobile terminal at the bottom area. 
         FIG. 10 b    is the radiation emulation side view of the mobile terminal at the bottom area. 
         FIG. 11 a    is the radiation emulation view of the mobile terminal when the difference of second slot antenna units is −120°. 
         FIG. 11 b    is the radiation emulation view of the mobile terminal when the difference of second slot antenna units is 0°. 
         FIG. 11 c    is the radiation emulation view of the mobile terminal when the difference of second slot antenna units is 120°. 
         FIG. 12 a    is the emulation gain view of the bottom area, which is expressed in a rectangular coordinate way, of the mobile terminal. 
         FIG. 12 b    is the emulation gain view of the bottom area, which is expressed in a polar coordinate way, of the mobile terminal. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     The present disclosure hereinafter is described in detail with reference to several exemplary embodiments. To make the technical problems to be solved, technical solutions and beneficial effects of the present disclosure more apparent, the present disclosure is described in further detail together with the figure and the embodiments. It should be understood the specific embodiments described hereby is only to explain the disclosure, not intended to limit the disclosure. 
     Please refer to  FIGS. 1 a  and 1 b   , the embodiment of the invention provides a strip-shaped millimeter wave array antenna  100  of which the work frequency range includes 28 GHz. The strip-shaped millimeter wave array antenna  100  comprises of two metal grounding layers  1  and a sandwich metal layer  2 , wherein, the two metal grounding layers  1  are arranged in parallel. The sandwich metal layer  2  is sandwiched between the two metal grounding layers  1 . The sandwich metal layer  2  and the two metal grounding layers  1  are in a strip shape. The millimeter wave array antenna  100  is thinner than 1 mm. The thickness direction of the millimeter wave array antenna  100  is the direction in which one metal grounding layer  1  points to the other metal grounding layer  1 . The millimeter wave array antenna  100  is a phased array antenna. 
     The sandwich metal layer  2  comprises of a top surface  21 , a bottom surface  22 , a plurality of antenna slots  20  and a sandwich dielectric layer  200 , wherein, the top surface  21  is connected with the two metal grounding layers  1  along the long axis direction, the bottom surface  22  is opposite to and in parallel with the top surface  21 , the antenna slots  20  space the array along the long axis direction, penetrate the top surface  21  and bottom surface  22  and are connected with the two metal grounding layers  1 . Please refer to  FIG. 1 c   , the sandwich dielectric layer  200  is filled in the antenna slots  20  and made from non-conductive media. 
     The positions of the metal grounding layers  1  corresponding to each antenna slot  20  are provided with feed parts  10  which are used to feed. Each antenna slot  20 , and the metal grounding layers  1  and the sandwich metal layer  2  enclosing the slot  20  form a slot antenna unit  3 . 
     The slot antenna unit  3  comprises of a plurality of first slot antenna units  31  and a plurality of second slot antenna units  32 , which are staggered in order along the long axis direction of the sandwich metal layer  2 . The gap between a first slot antenna unit  31  and a contiguous second slot antenna unit  32  is half of the wavelength of a central work frequency point. 
     The feed parts  10  of the first slot antenna units  31  are arranged closely to the bottom surface  22 , and the feed parts  10  of the second slot antenna units  32  are arranged closely to the top surface  21 . The first slot antenna units  31  form a first millimeter wave array antenna, and the second slot antenna units  32  form a second millimeter wave array antenna. Please refer to  FIGS. 2 a  and 2 b   , main beams of the first millimeter wave array antenna face the top surface  21  and accumulate on the upper area A corresponding to the top surface  21 , and main beams of the second millimeter wave array antenna face the bottom surface  22  and accumulate on the lower area B corresponding to the bottom surface  22 . 
     Please refer to  FIGS. 3 a  and 3 b   ; the invention also provides a mobile terminal  400  which uses the millimeter wave array antenna  100 . The mobile terminal  400  also comprises of a back cover  41 , a framework  42  and a rectangular frame  43 , wherein, the frame  43  is included between the back cover  41  and the framework  42 . Of course, the mobile terminal  400  can comprise of other components, such as an LCD panel which is protected by the framework  42 . 
     The millimeter wave array antenna  100  is arranged on the inner side surface of the frame  43 , and the metal grounding layers  1  of the millimeter wave array antenna  100  are opposite to the inner side surface. The top surface of the sandwich metal layer  2  faces the back cover. The bottom surface of the sandwich metal layer faces the framework. 
     The frame  43  can be set as 142 mm long and 72 mm wide, i.e., the frame  43  can be used for a 5.5-inch mobile terminal or an LCD tablet computer which is 6 inches in maximum. The frame  43  comprises of a first short edge  431  at the top, a second short edge  432  which is at the bottom and spaced in parallel with the first short edge  431 , and two long edges  433  which connect with the first short edge  431  and the second short edge  432 . The millimeter wave array antenna  100  is arranged on the inner side surface of the first short edge  431 , and the length direction of the millimeter wave array antenna  100  is consistent with the length direction of the first short edge  431 . It has to explain that the sizes of the frame and the mobile terminal of the application are not limited. Reserving enough space in the mobile terminal to set the millimeter wave array antenna is the only requirement. 
     The back cover  41  is made of metal. The position corresponding to the millimeter wave array antenna  100  is provided with a first located groove  410 . The framework  42  is made of metal. The position corresponding to the millimeter wave array antenna  100  is provided with a second located groove  420 . The frame  43  is a metal frame and electrically connected with the metal grounding layers  1 . 
     The millimeter wave array antenna  100  which is designed in the way above has high space utilization ratio and doesn&#39;t occupy the horizontal spaces of the back cover  41  and the frame  42 . In addition, the first located groove  410  and the second located groove  420  are also used for the millimeter wave array antenna  100  to upward or downward radiate electromagnetic waves and prevent the electromagnetic wave radiation of the millimeter wave array antenna  100  from being influenced by the electromagnetic shielding of the back cover  41  and the framework  42 . 
     It should be noted that the back cover  41 , the framework  42  and the frame  43  of the invention are not limited to be made from metal. In other embodiments, the back cover  41 , the framework  42  and the frame  43  can be totally or partially made from nonmetal materials. When the back cover  41  and the framework  42  are made from nonmetal materials, the first located groove  410  and the second located groove  420  can be saved to avoid the electromagnetic wave radiation. 
     Refer to  FIGS. 4-12  for the radiation performance of the millimeter wave array antenna  100  in the mobile terminal. 
     Refer to  FIG. 4 a    for details, the main beams which are generated by a first millimeter wave array antenna point to the direction of the back cover  41  and the main beams accumulate at a top area C. The first slot antenna units  31  work, and the feed parts  10  of the first slot antenna units  31  are in a close-up state, and the feed parts  10  of the second slot antenna units  32  are in a close-down state. 
     Referring to  FIG. 4 b   , the main beams which are generated by a second millimeter wave array antenna point to the direction of the framework  42  and the main beams accumulate at a bottom area D. At this time, the second slot antenna units  32  work, and the feed parts  10  of the second slot antenna units  32  are in the close-up state, and the feed parts  10  of the first slot antenna units  31  are in the close-down state. 
       FIG. 5 a    shows reflection coefficients of the second slot antenna units  32 , which indicate the second slot antenna units  32  work near 28 GHz.  FIG. 5 b    shows the isolation degree among all slot antenna units. Combining with  FIG. 5 c   , the eight slot antenna units of the antenna system  100  are respectively marked as a 1 , a 2 , a 3 , a 4 , a 5 , a 6 , a 7  and a 8  in order, wherein, a 1 , a 3 , a 5  and a 7  are the first slot antenna units  31 , and a 2 , a 4 , a 6 , and a 8  are the second slot antenna units  32 . In  FIG. 5 b   , take S_ 21  and S_ 71  as examples, S_ 21  is the isolation degree between the second slot antenna unit a  2  and the first slot antenna unit a 1 . Thus, near 28 GHz, the longer the distance between two slot antenna units, the better the isolation degree is. 
       FIGS. 6 a  and 6 b    show the antenna radiation emulation graphs of the top area C when the first millimeter wave array antenna is at 28 GHz. In the condition, the feed parts  10  of the first slot antenna units  31  are in the close-up state, and the feed parts  10  of the second slot antenna units  32  are in the close-down state. Clearly indicated by the antenna radiation emulation graphs, radiation main beams with the maximum gain G are at the top area C of the mobile terminal  400 . 
       FIGS. 7 a -7 c    show beam pointed directions when the phase differences among the first slot antenna units  31  are respectively −150°, 0°, and 150°. Clearly indicated by the figures, with the different phase differences, the beams of the first millimeter wave array antenna are scanned in the top area. The maximum gains G when the phase differences are −150°, 0° and 150° are respectively 11.7 dB, 14.9 dB, and 11.5 dB. 
       FIGS. 9 a -9 b    show the collection of the antenna gains of the first slot antenna units  31  of the millimeter wave array antenna  100  in seven different phase differences. Indicated by the antenna gain emulation, the scanning angle of the millimeter wave array antenna  100  is from −30° to 30°, and the total covering angle is 60°. The observation plane is the plane which is shown in  FIG. 8 . 
       FIGS. 10 a  and 10 b    show the antenna radiation emulation graphs of the bottom area D when the second millimeter wave array antenna is at 28 GHz. In the condition, the feed parts  10  of the second slot antenna units  32  are in the close-up state, and the feed parts  10  of the first slot antenna units  31  are in the close-down state. Clearly indicated by the antenna radiation emulation graphs, main radiation beams with the maximum gain G are at the bottom area D of the mobile terminal  400 . 
       FIGS. 11 a , 11 b  and 11 c    show beam pointed directions when the phase differences among the second slot antenna units  32  are respectively −120°, 0°, and 120°. Clearly indicated by the figures, with the different phase differences, the beams of the second slot antenna units  32  are scanned in the bottom area. The maximum gains G when the phase differences are −120°, 0° and 120° are respectively 10.7 dB, 12.9 dB, and 11.6 dB. 
       FIGS. 12 a -12 b    show the collection of the antenna gains of the second slot antenna units of the millimeter wave array antenna in seven different phase differences. Indicated by the antenna gain emulation, the scanning angle of the second millimeter wave array antenna is from 150° to 210°, and the total covering angle is 60°. The observation plane is the plane which is shown in  FIG. 8 . 
     Compared with the prior art, the millimeter wave array antenna and the mobile terminal of the invention have the following advantages: the millimeter wave array antenna is thin and can be vertically arranged on a side wall of the mobile terminal in order to occupy little horizontal space of the mobile terminal. The millimeter wave array antenna has low requirement on the clearance area and can be used if the antenna slot opening is not covered. The millimeter wave array antenna can scan the beams respectively in the two opposite directions of the mobile terminal. 
     It is to be understood, however, that even though numerous characteristics and advantages of the present exemplary embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms where the appended claims are expressed.