Patent Publication Number: US-11031671-B2

Title: AOG antenna system and mobile terminal

Description:
TECHNICAL FIELD 
     The present disclosure relates to the field of wireless communication technologies, and in particular, to an AOG (Antenna On Glass) antenna system and a mobile terminal. 
     BACKGROUND 
     With 5G being the focus of research and development in the global industry, developing 5G technologies and formulating 5G standards have become the industry consensus. The ITU-RWP5D 22nd meeting held in June 2015 by International Telecommunication Union (ITU) identified three main application scenarios for 5G: enhance mobile broadband, large-scale machine communication, and highly reliable low-latency communication. These three application scenarios respectively correspond to different key indicators, and in the enhance mobile broadband scenario, the user peak speed is 20 Gbps and the minimum user experience rate is 100 Mbps. Currently, 3GPP is working on standardization of 5G technology. The first 5G Non-Stand Alone (NSA) international standard was officially completed and frozen in December 2017, and the 5G Stand Alone standard was scheduled to be completed in June 2018. Research work on many key technologies and system architectures during the 3GPP conference was quickly focused, including the millimeter wave technology. The high carrier frequency and large bandwidth characteristics unique to the millimeter wave are the main means to achieve 5G ultra-high data transmission rates. 
     The rich bandwidth resources of the millimeter wave band provide a guarantee for high-speed transmission rates. However, due to the severe spatial loss of electromagnetic waves in this frequency band, wireless communication systems using the millimeter wave band need to adopt an architecture of a phased array. The phases of respective array elements are caused to distribute according to certain regularity by a phase shifter, so that a high gain beam is formed and the beam is scanned over a certain spatial range through a change in phase shift. 
     With an antenna being an indispensable component in a radio frequency (RF) front-end system, it is an inevitable trend in the future development of the RF front-end to system-integrate and package the antenna with a RF front-end circuit while developing the RF circuit towards the direction of integration and miniaturization. The antenna-in-package (AiP) technology integrates, through package material and process, the antenna into a package carrying a chip, which fully balances the antenna performance, cost and volume and is widely favored by broad chip and package manufacturers. At present, companies including Qualcomm, Intel, IBM and the like have adopted the antenna-in-package technology. Undoubtedly, the AiP technology will also provide a good antenna solution for 5G millimeter wave mobile communication systems. 
     A metal middle frame with 3D glass is the mainstream solution for the future full-screen phone structure design, which can provide better protection, aesthetics, thermal diffusion, color and user experience. However, due to a higher dielectric constant of 3D glass, the radiation performance of the millimeter wave antenna will be seriously affected, and the antenna array gain will be reduced. Moreover, in the related antenna package technology, an overall thickness of the antenna system is relatively large, which does not satisfy the miniaturization requirement of the antenna system. 
     Therefore, it is necessary to provide a new antenna system and a new mobile terminal to solve the above problems. 
    
    
     
       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 perspective structural schematic diagram of a mobile terminal provided by the present disclosure; 
         FIG. 2  is a plane structural schematic diagram of a partial structure of the mobile terminal shown in  FIG. 1 ; 
         FIG. 3  is a hierarchical structure schematic diagram of a feeding network shown in  FIG. 1 ; 
         FIG. 4A  illustrates a radiation pattern with a phase shift of each metal antenna unit being 45° in an AOG system provided by the present disclosure; 
         FIG. 4B  illustrates a radiation pattern with a phase shift of each metal antenna unit being 0° in an AOG system provided by the present disclosure; 
         FIG. 4C  illustrates a radiation pattern with a phase shift of each metal antenna unit being −45° in an AOG system provided by the present disclosure; 
         FIG. 5  illustrates a reflection coefficient graph of an AOG system provided by the present disclosure; and 
         FIG. 6  illustrates a coverage efficiency graph of an AOG system provided by the present disclosure. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The present disclosure will be further illustrated with reference to the accompanying drawings and the embodiments. 
     As shown in  FIGS. 1-3 , the present disclosure provides a mobile terminal  100 . The mobile terminal  100  may be a mobile phone, an iPad, a POS machine, etc., which is not limited by the present disclosure. The mobile terminal  100  includes a frame  1 , a 3D glass back cover  2  covering and connected to the frame  1  and enclosing a receiving space with the frame  1 , a main board  3  that is received in the receiving space and spaced apart from the 3D glass back cover  2 , and an AOG antenna system  4  electrically connected to the main board  3 . 
     The 3D glass back cover  2  can cover and be connected to the frame  1  by an adhesive, or the frame  1  and the 3D glass back cover  2  may be respectively provided with a corresponding buckle structure, such that the 3D glass back cover  2  can be fixedly connected to the frame  1  by a buckling manner. Alternatively, the frame  1  and the 3D glass back cover may be formed into one piece. The 3D glass back cover  2  can provide better protection, aesthetics, thermal diffusion, color and user experience. 
     The AOG antenna system  4  can receive and transmit electromagnetic wave signals, thereby achieving the communication function of the mobile terminal  100 . Specifically, the AOG antenna system  4  can be connected to the main board  3  through BGA package technology. 
     The AOG antenna system  4  is a millimeter wave phased array antenna system. Specifically, the AOG antenna system  4  includes a metal antenna  41  provided on a surface of the 3D glass back cover  2 , and a packaged feeding module  42  provided between the 3D glass back cover  2  and the main board  3  and electrically connected to the main board  3 . The packaged feeding module  42  corresponds to a position of the metal antenna  41  and feeds the metal antenna  41  with power by coupling. It should be noted that the metal antenna  41  may be provided on an outer surface or an inner surface of the 3D glass back cover  2 . The outer surface of the 3D glass back cover  2  is a face facing away from the main board  3 , and the inner surface of the 3D glass back cover  2  is a face close to the main board  3 . 
     In this embodiment, the metal antenna  41  may be selected from one of a square patch antenna, a ring patch antenna, a circular patch antenna, and a cross-shaped patch antenna. As an example, the metal antenna  41  may be a square patch antenna. Without doubt, in other embodiments, the metal antenna  41  may also use an antenna of other forms. 
     Each of the surfaces of the 3D glass back cover  2  may be designed as a planar surface, alternatively, part of the surfaces are designed as a planar surface and the other part of the surfaces are designed as a curved surface, so as to meet the needs of different users. The metal antenna  41  is formed on the surface of the 3D glass back cover  2  by a printed conductive silver paste method or a printed LDS ink method. Moreover, in order to prevent the metal antenna  41  from affecting the beauty degree of the mobile terminal  100 , the metal antenna  41  may be designed to be located near the Logo. Alternatively, a protective film may be applied to the surface of the metal antenna  41 , which not only avoids affecting the beauty degree but also protects the antenna. The protective film is preferably a low dielectric thin film or plastic. 
     Further, the metal antenna  41  is a one-dimensional linear array, occupies a narrow space in the mobile phone, and is scanned only in one perspective, which simplifies design difficulty, test difficulty, and beam management complexity. As an example, the metal antenna  41  may be a linear array of 1×4, i.e., the metal antenna  41  includes four metal antenna units  411 . 
     The packaged feeding module  42  includes a substrate  421 , an integrated circuit chip  422  provided on a side of the substrate  421  facing towards the main board  3 , and a feeding network  423  provided in the substrate  421  and arranged opposite to the metal antenna  41 , and a circuit  424  connecting the feeding network  423  with the integrated circuit chip  422 . The feeding network  423  feeds the metal antenna  41  with power by coupling, and the circuit  424  is electrically connected to the main board  3 . 
     The substrate  421  is used to carry the feeding network  423 . The substrate  421  may be formed as a whole or may be arranged by layers. 
     The integrated circuit chip  422  is fixedly connected to the substrate  421  by the flip-chip bonding process. 
     The feeding network  423  is a strip wire having impedance that is easy to control and having better shielding, which can effectively reduce the loss of electromagnetic energy and improve the antenna efficiency. The feeding network  423  includes a first metal layer  4231  close to the metal antenna  41 , a second metal layer  4232  arranged opposite to and spaced apart from the first metal layer  4231 , and a strip wire layer  4233  sandwiched between the first metal layer  4231  and the second metal layer  4232 . 
     The first metal layer  4231  is provided with a slit  40  at a position corresponding to the metal antenna  41 , and the feeding network  423  feeds the metal antenna  41  with power by coupling via the slit  40 . 
     The number of the slits  40  matches the number of the metal antenna units  411  and each of the metal antenna units  411  is fed with power by the feeding network  423  by coupling via the slit  40 . Specifically, electromagnetic energy is coupled to the metal antenna unit  411  through the slit  40 . In this embodiment, the number of the slits  40  is four, and each of the slits  40  is provided corresponding to one of the metal antenna units  411 . The cross-sectional shape of the slit  40  is in an I-shape. In other embodiments, the cross-sectional shape of the slit  40  may be square, circular or triangular, which is not limited in the present disclosure. 
     Further, an orthographic projection of the slit  40  towards the metal antenna unit  411  completely falls within the range of the metal antenna unit  411 . 
     Even further, the packaged feeding module  42  is stacked by a PCB process or an LTCC process. 
     Compared with the antenna-in-package, the AOG antenna system  4  in this embodiment is provided with the metal antenna  41  on the 3D glass back cover  2 , and is only provided with the feeding structure on the substrate  421  and uses it as a package structure of the integrated circuit chip  422 , which can reduce the space occupied by the AOG antenna system  4  as a whole. Specifically, according to the bandwidth of n257 of the 5G communication and taking a 1×4 array as an example, a thickness of the AOG antenna system  4  can be reduced by at least 0.4 mm, and its area is reduced from 5.5 mm×12 mm to 3 mm×10 mm. 
     Moreover, in this embodiment, the 3D glass back cover  2  has a dielectric constant of 6.3+i0.039 and a thickness of 0.7 mm; the substrate  421  of the packaged feeding module  42  is formed by pressing 6 layers of high-frequency low-loss PCB sheets, in which a core layer is pressed with Rogers4350B and has a thickness of 0.254 mm, while the remaining dielectric layers are pressed with Rogers4450F and have a thickness of 0.2 mm. Without doubt, it should be noted that the present disclosure does not limit the dielectric constant of the 3D glass back cover  2 , nor does it limit the number, thickness, and manufacturing manner of the substrate  411  of the packaged feeding module  42 . 
     Referring to  FIG. 4A  to  FIG. 6 ,  FIG. 4A  illustrates a radiation pattern with a phase shift of each metal antenna unit being 45° in an AOG system provided by the present disclosure,  FIG. 4B  illustrates a radiation pattern with a phase shift of each metal antenna unit being 0° in an AOG system provided by the present disclosure,  FIG. 4C  illustrates a radiation pattern with a phase shift of each metal antenna unit being −45° in an AOG system provided by the present disclosure, and  FIG. 5  illustrates a reflection coefficient graph of an AOG system provided by the present disclosure. 
     Generally, due to the high dielectric constant of 3D glass, using it as the back cover of the mobile phone seriously may affect the radiation performance of the antenna system received therein, reduce the radiation efficiency and the gain, and results in the distortion of the radiation pattern due to the influence of surface waves. In the present disclosure, by using the 3D glass back cover  2  as a dielectric substrate of an antenna and transmitting electromagnetic energy from the packaged feeding module  42  to the metal antenna  41  by coupling so as to radiate outwardly, the effect of the 3D glass back cover  2  on the antenna system is greatly reduced and the antenna efficiency is improved, thereby avoiding the distortion of the radiation pattern and maintaining good working state. 
     Referring to  FIG. 6 ,  FIG. 6  illustrates a coverage efficiency graph of an AOG antenna system provided by the present disclosure. As can be seen from  FIG. 6 , in the case where the coverage efficiency is 50%, the gain threshold of the AOG antenna system  4  is decreased by 12 dB, while in the 3GPP discussion, the gain threshold is reduced by 12.98 dB for the case of 50% coverage efficiency, showing that the AOG antenna system  4  of the present disclosure has the better coverage efficiency. 
     Compared with the related art, the AOG antenna system  4  and the mobile terminal  100  provided by the present disclosure have the following beneficial effects. By providing the metal antenna  41  on the surface of the 3D glass back cover  2  and feeding the metal antenna with power by coupling with the packaged feeding module  42 , the effect of the 3D glass back cover on the antenna system can be greatly reduced, increasing the antenna radiation efficiency and reducing the gain reduction, thereby achieving the communication effect and reducing the space occupied by the AOG antenna system  4 . The millimeter wave phased array antenna system adopts a linear array instead of a planar array, so as to occupy a narrower space in the mobile phone and to perform scanned in one perspective, which simplifies design difficulty, test difficulty and beam management complexity. 
     What has been described above is only an embodiment of the present disclosure, and it should be noted herein that one ordinary person skilled in the art can make improvements without departing from the inventive concept of the present disclosure, but these are all within the scope of the present disclosure.