Patent Publication Number: US-10763577-B2

Title: Antenna system for optimizing isolation and mobile terminal

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a 35 U.S.C. § 371 National Phase conversion of International (PCT) Patent Application No. PCT/CN2017/103632 filed on Sep. 27, 2017, which claims foreign priority of Chinese Patent Application No. 201610991317.5, filed on Nov. 10, 2016 in the National Intellectual Property Administration of China, the contents of all of which are hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to the technical field of radio antennas, and particularly to an antenna system for optimizing isolation and a mobile terminal. 
     BACKGROUND 
     Wireless multiple-input and multiple-output technology, as one of the key technologies to realize high-speed broadband wireless network access, can satisfy requirements for high transmission rate and extended coverage of future mobile communication, and is widely applied in mobile communication systems. With the development of the mobile terminal technology, the wireless multiple-input and multiple-output technology has increasingly complicated design environment, and is restricted by the appearance and size of the mobile terminal, especially hand-held mobile terminal, such that certain difficulties occur in multi-antenna implementation. 
     The design of current antennas often involves a need to provide a diversity antenna and a WIFI/BT/GPS antenna within a limited space. When a feed point of the diversity antenna is quite near to a feed point of other antenna, the two antennas will produce a coupling effect and thereby affect performance of the antennas. Therefore, isolation is a key indicator for judging magnitude of mutual influence between antennas. How to coordinate isolation between antenna units and limited size of a mobile terminal device to ensure excellent inter-antenna isolation within a working frequency band in limited environment is a main research issue of multiple antennas of the mobile terminal. 
     SUMMARY 
     The technical problem to be solved by the present disclosure is to provide an antenna system for optimizing isolation, which can increase the isolation between antennas. 
     In order to solve the above-mentioned technical problem, an aspect of the present disclosure provides an antenna system for optimizing isolation. The system includes a circuit board, and the circuit board is provided with: a clearance slot defined in an electromagnetic conductor of the circuit board and between antenna feed points for optimizing isolation between the antenna feed points; and at least two clearance areas disposed on both sides of the electromagnetic conductor having the clearance slot of the circuit board for arranging the antenna feed points. Neither the clearance areas nor the clearance slot contains an electromagnetic conductor. 
     In order to solve the above-mentioned technical problem, a further aspect of the present disclosure provides a mobile terminal. The mobile terminal comprises a circuit board. The circuit board is provided with: a clearance slot defined in an electromagnetic conductor of the circuit board and between antenna feed points for optimizing isolation between the antenna feed points; and at least two clearance areas disposed on both sides of the electromagnetic conductor having the clearance slot of the circuit board for arranging the antenna feed points. Neither the clearance areas nor the clearance slot contains an electromagnetic conductor. 
     The present disclosure provides clearance slots between the diversity antenna feed point and other antenna feed point, and provides clearance areas on both sides of the clearance slots, thereby increasing isolation between the antennas in a limited space, avoiding the coupling effect between the antennas, and alleviating the problem present in traditional multiple-input and multiple-output antennas limited by the size of the terminal device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a structural diagram of an embodiment of an antenna system for optimizing isolation according to the present disclosure. 
         FIG. 2  is a structural diagram showing size of clearance slots of an embodiment of an antenna system for optimizing isolation according to the present disclosure. 
         FIG. 3  is a planar structural diagram of an embodiment of a mobile terminal including an antenna system for optimizing isolation according to the present disclosure. 
         FIG. 4  is a three-dimensional structural diagram of an embodiment of a mobile terminal including an antenna system for optimizing isolation according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure will be described in detail below in conjunction with the accompanying drawings and embodiments. 
     Referring to  FIG. 1 , an antenna system for optimizing isolation according to the present disclosure comprises a circuit board. The circuit board defines clearance slots  10  in an electromagnetic conductor  40  of the circuit board and between antenna feed points  30  for optimizing isolation between antenna units. 
     In the present embodiment, the clearance slots  10  do not include an electromagnetic conductor. The two clearance slots  10  are inverted mirror slotted matrix, i.e., the two clearance slots  10  form a matrix of slots, and one clearance slot is an inverted mirror image of another clearance slot; and the direction in which the two clearance slots  10  are arranged is perpendicular to a connection line between the antenna feed points  30 . 
     At least two clearance areas  20  are disposed on both sides of the electromagnetic conductor  40  defining the clearance slots  10  of the circuit board for arranging the antenna feed points  30 . 
     In the present embodiment, the clearance areas  20  do not include an electromagnetic conductor. The antenna feed point  30  is a diversity antenna feed point or a WIFI/BT/GPS antenna feed point respectively disposed within the two clearance areas  20 . The diversity antenna feed point within one clearance area further includes a plurality of single-antenna feed points. A plurality of single antennas are used for simultaneously transmitting and receiving a plurality of spatial streams, and can make a distinction between signals to or from different spatial orientations. The coupling effect is not considered between the plurality of single-antenna feed points. Therefore, the plurality of single-antenna feed points can be regarded as one diversity antenna feed point, and are arranged within a same clearance area. 
     The other clearance area includes: a WIFI antenna feed point, wherein the WIFI antenna is used to intensify wireless network signals; a BT antenna feed point, wherein the BT antenna is used to transmit and receive electromagnetic wave energy in wireless communication; and a GPS antenna feed point, wherein the GPS antenna is used to receive satellite positioning signals. 
     The coupling effect is not considered between the WIFI antenna feed point, the BT antenna feed point and the GPS antenna feed point, either. Therefore, the WIFI antenna feed point, the BT antenna feed point and the GPS antenna feed point can be regarded as one antenna feed point, and are arranged within a same clearance area. Specific positions of the plurality of single-antenna feed points and the WIFI/BT/GPS antenna feed points in the respective clearance areas are configured as actually required and are not defined herein. 
     Referring to  FIG. 2 , each of the clearance slots  10  is a rectangle lacking one side, and each width a of two opposite sides of the rectangle is 0.45 to 0.55 mm, preferably, a is 0.5 mm; a width b of one side between the two opposite sides is 0.65 to 0.75 mm, preferably, b is 0.7 mm; and a spacing c between the rectangles is 0.45 to 0.55 mm, preferably c is 0.5 mm. The side with width b is perpendicular to a connection line between the antenna feed points  30 . 
     In the present embodiment, a length d of the rectangle in the clearance slot  10  is 2.45 to 2.55 mm, preferably, d is 2.5 mm; and a width e of the rectangle is 1.95 to 2.05 mm, preferably, e is 2 mm. The specific size and position of the clearance slot  10  are adjusted according to the actual positions and properties of the two antennas. The isolation effect produced by the clearance slot  10  between the two antenna feed points  30  is equivalent to introducing a capacitance or inductance through slotting, thereby creating a stopband to reduce the coupling effect between the two antenna feed points. 
     The present embodiment provides clearance slots between the diversity antenna feed point and other antenna feed point, and provides clearance areas on both sides of the clearance slots, thereby increasing isolation between the antennas in a limited space, avoiding the coupling effect between the antennas, and alleviating the problem present in traditional multiple-input and multiple-output antennas limited by the size of the terminal device. 
     Referring to  FIG. 3  and  FIG. 4 , the present disclosure provides a mobile terminal which includes a circuit board. The circuit board defines clearance slots  10  in an electromagnetic conductor  40  of the circuit board and between antenna feed points  30  for optimizing isolation between antenna units, and is provided with at least two clearance areas  20  on both sides of the electromagnetic conductor  40  having the clearance slots  10  of the circuit board for arranging the antenna feed points  30 . 
     In the present embodiment, the circuit board is a PCB board comprising an electromagnetic conductor layer and an insulation layer. In practical applications, the size of the PCB board is limited, and it is impossible to increase isolation between the antennas by enlarging physical distance between the antenna feed points. Therefore, in the present embodiment, the clearance slots  10  and the clearance areas  20  are arranged to increase isolation between the antennas. The clearance slots  10  only penetrate through the electromagnetic conductor layer, with the insulation layer remaining. The clearance areas  20  also contain no electromagnetic conductor, with the insulation layer remaining. 
     In the present embodiment, the positions and sizes of the clearance slot  10  can be referred to the embodiments of the antenna system, and details are not described herein. The clearance areas  20  are divided into one side provided with a diversity antenna feed point and the other side provided with a WIFI/BT/GPS antenna feed point. The specific positions and sizes of the clearance areas  20  are adjusted according to numbers, sizes and positions of the feed points actually included in the diversity antenna feed point or WIFI/BT/GPS antenna feed point. For antennas operating in different frequency bands, the impedance bandwidth of the antennas can be adjusted by reserved antenna matching, feed point position, and slotted size of the clearance slot  10  on the PCB board. 
     It should be noted that, the mobile terminal in the present embodiment includes, but is not limited to, a mobile phone, and may also be applied to all circumstances where the antenna technology can be applied, for example, wireless access. 
     The present embodiment provides clearance slots between the diversity antenna feed point and other antenna feed point, and provides clearance areas on both sides of the clearance slots, thereby increasing isolation between the antennas in a limited space, avoiding the coupling effect between the antennas, and alleviating the problem present in traditional multiple-input and multiple-output antennas limited by the size of the terminal device. 
     The foregoing are only embodiments of the present disclosure, and thus do not limit the patent scope of the present disclosure. Any equivalent structural transformation made by turning to the contents set forth in description and drawings of the present disclosure, or directly or indirectly applied to other related technical fields, shall likewise be included in the scope of the patent protection of the present disclosure.