Patent Publication Number: US-2022239004-A1

Title: Antenna Apparatus and Mobile Terminal

Description:
This disclosure claims priority to Chinese Patent Application No. 201910401967.3, filed with the China National Intellectual Property Administration on May 13, 2019 and entitled “ANTENNA APPARATUS AND MOBILE TERMINAL”, which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to the field of antenna technologies, and in particular, to an antenna apparatus used in a terminal. 
     BACKGROUND 
     With development of mobile communications technologies, a multi-input multi-output (multi input multi output, MIMO) antenna technology, such as a high-fidelity wireless multi-input multi-output (wireless fidelity MIMO, Wi-Fi MIMO) antenna, is increasingly widely used on a terminal, a quantity of antennas is multiplied, and increasingly more frequency bands are covered. Recently, the terminal tends to be designed with a higher screen-to-body ratio, more multimedia components, and a larger battery capacity. These designs cause intense compression of antenna space. How to arrange a plurality of antennas in limited design space is a very challenging problem. In addition, an industry design (industry design, ID) such as a metal ID or a full-screen ID of a terminal product also needs to be considered in antenna arrangement. This further increases an antenna arrangement difficulty. 
     SUMMARY 
     A technical problem to be resolved in embodiments of this disclosure is to provide an antenna apparatus that has an advantage of a compact structure, so that a plurality of antennas can be arranged in limited design space, and can be flexibly installed in a mobile terminal. 
     According to a first aspect, an embodiment of this disclosure provides an antenna apparatus, including a grounding plate, a monopole, a first feeding unit, and a second feeding unit. Specifically, the grounding plate may be a metal sheet structure, or may be a metal layer disposed on a dielectric board. The grounding plate is electrically connected to ground on a mainboard in a mobile terminal. The monopole may be a metal strip structure, or may be a microstrip structure disposed on the dielectric board. A slot is disposed on the grounding plate, the slot includes a first slot and a second slot that interpenetrate each other, and the second slot extends from the first slot to an edge of the grounding plate. In other words, the slot on the grounding plate forms an opening at an edge position of the grounding plate, so that the monopole extends into the slot through the opening. The monopole includes a first stub and a second stub. The second stub extends from the first stub into the second slot, in other words, the second stub extends from an opening position of the slot into the slot. The second stub extends to a position of the second slot, and the second stub is insulated from the grounding plate by using a gap, in other words, the second stub is not in contact with an inner wall of the slot. Specifically, the second stub is at a central position in the second slot. The second stub and the second slot form a feeding structure. The first feeding unit is electrically connected to the grounding plate and performs feeding as the feeding structure, to excite a first radiation mode of the antenna apparatus, where the first slot and the grounding plate are used as radiators in the first radiation mode. The second feeding unit is electrically connected to the second stub and performs feeding as the feeding structure, to excite a second radiation mode of the antenna apparatus, where the second stub and the grounding plate are used as radiators in the second radiation mode. A polarization direction in the first radiation mode is orthogonal to a polarization direction in the second radiation mode. 
     According to the antenna apparatus provided in this embodiment of this disclosure, two radiation modes of the antenna apparatus can be implemented by using a feeding structure formed after the monopole is coupled with the grounding plate. In this disclosure, the grounding plate is used as a main radiator, so that the antenna apparatus has balanced high performance, in other words, radiation performance is stable and of high quality, and a dual-antenna effect is implemented by using a simple and compact structure. In the two radiation modes, polarization directions of the antenna apparatus are orthogonal, so that the antenna apparatus has high isolation. 
     In an implementation, the first feeding unit excites an in-phase current loop around the first slot, and the in-phase current loop excites currents on the grounding plate in a first direction, to form the first radiation mode. 
     In the first radiation mode, the first slot on the grounding plate may be considered as two opening-to-opening open-circuit slots. Each open circuit works in a quarter-wave mode, and phases in the two quarter-wave modes are opposite to each other. Specifically, the first slot extends in the first direction. In the first direction, from one end to the other end of the first slot, an electric field changes from null (that is, a position on the grounding plate, where the position may be considered as a short-circuit point) to a maximum value (that is, a position at which the second slot intersects with the first slot, where in an implementation, a start point of the second slot is located at a central position in the first slot); and after the electric field passes through the second slot, a direction of the electric field is reversed, and the electric field changes from a reverse maximum value to null. In this way, currents surround the first slot to form a loop of in-phase currents in a same direction. The in-phase currents may excite the currents on the grounding plate in the first direction, so that the grounding plate becomes a main radiator, and a polarization direction is the first direction. 
     In an implementation, the second feeding unit excites generation of currents on the monopole and the grounding plate, the currents on the monopole and the grounding plate include currents distributed in the first direction and currents distributed in a second direction, and the currents in the first direction are in mirrored distribution by using the second stub as an axis of symmetry, in other words, the currents in the first direction have mutually reversed components and therefore do not form effective radiation, and only the currents distributed in the second direction contribute to radiation, to form the second radiation mode. The first direction is perpendicular to the second direction. 
     The second radiation mode is a monopole mode. In an implementation, the monopole and the grounding plate are distributed in an axisymmetric structure by using the second stub as a central axis, and the second stub is a strip structure. The currents in the first direction have mutually reversed components that offset each other. Therefore, in the second radiation mode, a current direction is only the second direction, the second stub and two edges of the grounding plate form radiation, and the two edges of the grounding plate are edges of the grounding plate that extend in a same direction as the second stub, are referred to as radiation edges, and are distributed on two sides of the second stub. For the monopole, currents on the second stub flow to the first stub from a tail end that is of the second stub and that is away from the first stub, and separately flow, on the first stub, to two ends of the first stub. Therefore, currents on the first stub that are distributed on the two sides of the second stub are in opposite directions, and can offset each other. For the grounding plate, currents that flow to the second slot are formed on an edge of the grounding plate. The edge of the grounding plate is an edge connected between the two radiation edges, in other words, an edge on which the second slot is located. Currents on the edge are all in the first direction, but are in opposite directions on two sides of the second slot, in other words, currents on one side flow leftward and currents on the other side flow rightward, and are mutually reversed currents. In this way, currents on the radiation edges of the grounding plate are in the second direction, and are in a same direction as the currents on the second stub. In this way, the grounding plate and the second stub form radiators, and the grounding plate is a main radiator. 
     In an implementation, an intersection between the second stub and the first stub is a connection part, and a first segment and a second segment of the first stub are symmetrically distributed on two sides of the connection part. In this embodiment, the monopole may be in a T-shape, a Y-shape, or another similar structure, and the first stub may be in a linear shape, or may be in an arc shape or a serpentine shape. This is not limited in this disclosure. 
     In an implementation, both the first segment and the second segment are linear and collinear, and a shape in which the first stub extends may affect an overall size of the antenna apparatus. A linear and collinear design helps save space. 
     In an implementation, the second stub is linear, and the second stub is perpendicular to the first segment. In other words, the monopole is T-shaped, has a simple structure, and is easy to manufacture. 
     Certainly, a shape of the monopole in the antenna apparatus in this disclosure may be extended. For example, in an implementation, the first stub includes a pair of bent segments, one of the bent segments is connected to an end that is of the first segment and that is away from the connection part, and the other bent segment is connected to an end that is of the second segment and that is away from the connection part. The pair of bent segments are symmetrically distributed on the two sides of the second stub. 
     In an implementation, the pair of bent segments and the second stub are located on same sides of the first segment and the second segment. In other words, the bent segments are located in space between the grounding plate and both the first segment and the second segment. It is clear that this structure helps save space. 
     In an implementation, a part that is of the second stub and that extends into the second slot and the grounding plate on an edge of the second slot jointly form a CPW (Coplanar Waveguide, coplanar waveguide) feeding structure. 
     In an implementation, in the first radiation mode, electric field distribution of the CPW feeding structure is a differential mode, and in the second radiation mode, electric field distribution of the CPW feeding structure is a common mode. In the two radiation modes, electric field distribution of the CPW feeding structure is opposite. In this disclosure, the differential mode of the CPW feeding structure is used to excite the first radiation mode (also referred to as an in-phase current loop mode) of the antenna apparatus. In this disclosure, the common mode of the CPW feeding structure is used to excite the second radiation mode (also referred to as a monopole mode) of the antenna apparatus. 
     Specifically, the antenna apparatus provided in this disclosure may be an intra-band dual-antenna pair with balanced high performance and high isolation. Optionally, the antenna apparatus may be specifically a Sub-6G dual-antenna pair, and a working frequency of the antenna apparatus is 3.4 GHz to 3.6 GHz, in other words, the same frequency band is a Sub-6G frequency band. Optionally, the antenna apparatus may be specifically an intra-band dual-Wi-Fi antenna pair such as a dual-Wi-Fi antenna pair on a 2.4 GHz frequency band, in other words, the same frequency band is a Wi-Fi frequency band such as a 2.4 GHz Wi-Fi frequency band. This constitutes no limitation. The antenna apparatus may alternatively be an intra-band dual-antenna pair on another frequency band. 
     In another implementation, the antenna apparatus may alternatively work on different frequency bands in the two modes. For example, the antenna apparatus works on a first frequency band in the first radiation mode, and works on a second frequency band in the second radiation mode. Optionally, the first frequency band may include a Wi-Fi frequency band, and the second frequency band may include a Wi-Fi frequency band and a GPS frequency band. For example, the antenna apparatus may excite slot to generate a 2.4 GHz Wi-Fi resonance (the first frequency band is a 2.4 GHz Wi-Fi frequency band), or may excite to generate two resonances: a GPS L1 resonance and a 2.4 GHz Wi-Fi resonance (the second frequency band includes a 2.4 GHz Wi-Fi frequency band and a GPS L1 frequency band). This constitutes no limitation. The first frequency band and the second frequency band may be other frequency bands. 
     In an implementation, the first feeding unit includes a first feeding point and a first feeder, an insulation slot is disposed on the grounding plate, the first feeding point is located in the insulation slot, and the first feeder crosses the CPW feeding structure, and is electrically connected between the first feeding point and the grounding plate. 
     In an implementation, the first feeding unit further includes a matching component, the matching component is electrically connected to the first feeder and is grounded, and the matching component is configured to adjust a resonance point and impedance matching that are of the antenna apparatus in the first radiation mode. By adjusting an antenna transmit coefficient, impedance, and the like, the matching component may also adjust a frequency band range covered by the antenna apparatus. In this implementation, electrically connecting the matching component to the first feeder is specifically: first connecting a 0.2 pF capacitor in parallel, and then connecting a 5.6 nH inductor in series. 
     In an implementation, the second feeding unit includes a second feeding point and a second feeder, and the second feeder is electrically connected between the second feeding point and the second stub to excite the second radiation mode. The second feeding unit also includes a matching component. The matching component is electrically connected to the second feeding point to affect the second feeding point, and is configured to adjust a resonance point and impedance matching that are of the antenna apparatus in the second radiation mode. For example, electrically connecting the matching component to the second feeding point is specifically: first connecting a 0.5 pF capacitor in parallel, and then connecting a 0.4 pF capacitor in series. 
     In an implementation, the first slot is an axisymmetric structure, and a symmetric central axis of the first slot is located on a center line that is of the second slot and that is in the second direction. 
     In an implementation, the first slot includes a first end and a second end that are disposed oppositely, a direction in which the first end extends to the second end is the first direction, the antenna apparatus works in a quarter-wave mode from the first end to a position of the second slot, the antenna apparatus works in the quarter-wave mode from the second slot to a position of the second end, an electric field at the first end and an electric field at the second end are zero, and an electric field value at the position of the second slot is the largest. 
     In an implementation, the monopole and the grounding plate are coplanar. 
     In an implementation, the antenna apparatus is a microstrip structure printed on a surface of a substrate. For example, a mobile terminal includes a mainboard and a side board. The side board is disposed at an edge position of the mainboard, and is disposed between the mainboard and a side frame of the mobile terminal. The side board may be perpendicular to the mainboard. In an implementation, the mainboard and the side board each may be an FR-4 dielectric plate with a thickness of 0.8 mm. Main ground is disposed on the mainboard, that is, a ground plane on the mainboard. The antenna apparatus is printed on the side board, and the grounding plate is electrically connected to the main ground on the mainboard. The grounding plate and the monopole are printed on an outer side of the side board. The outer side of the side board is a surface that is of the side board and that faces the side frame of the mobile terminal. A surface that is of the side board and that faces the inside of the mobile terminal and a surface of the mainboard is an inner side of the side board. The first feeding unit and the second feeding unit are disposed on the inner side of the side board. The side board includes a top part and a bottom part. The bottom part is an end that is of the side board and that is connected to the mainboard, and the top part is an end that is of the side board and that is away from the mainboard. In an implementation, the monopole is disposed on the top part of the side board, and the first slot in the slot is located on the bottom part of the side board. 
     According to a second aspect, an embodiment of this disclosure provides a mobile terminal, including a side frame connected between a display screen and a rear cover. A mainboard is disposed in the mobile terminal. An edge of the mainboard is disposed near the side frame, the mobile terminal further includes the antenna apparatus in any one of the foregoing implementations, and the antenna apparatus is located between the mainboard and the side frame. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       To describe the technical solutions in the embodiments of the present invention or in the background more clearly, the following briefly describes the accompanying drawings required for describing the embodiments of the present invention or the background. 
         FIG. 1  is a diagram of an disclosure environment of an antenna apparatus according to an implementation of this disclosure; 
         FIG. 2  is a schematic diagram of a positional relationship between a printed circuit board PCB and a side board in a mobile terminal in  FIG. 1 ; 
         FIG. 3  is a schematic diagram of an architecture of an antenna apparatus according to an implementation of this disclosure; 
         FIG. 4  is a schematic planar diagram of the antenna apparatus shown in  FIG. 3 ; 
         FIG. 5  is a schematic diagram of enlarging a second feeding unit of the antenna apparatus in  FIG. 3 ; 
         FIG. 6  is a schematic planar diagram of an antenna apparatus according to an implementation of this disclosure; 
         FIG. 7  is a schematic diagram of a first radiation mode of an antenna apparatus according to an implementation of this disclosure; and 
         FIG. 8  is a schematic diagram of a second radiation mode of an antenna apparatus according to an implementation of this disclosure. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The following describes the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. 
     The technical solutions provided in this disclosure are applicable to a terminal that uses one or more of the following MIMO communications technologies: a long term evolution (long term evolution, LTE) communications technology, a Wi-Fi communications technology, a 5G communications technology, a Sub-6G communications technology, another MIMO communications technology in the future, and the like. In this disclosure, the terminal may be an electronic device such as a mobile phone, a tablet computer, or a personal digital assistant (personal digital assistant, PDA). 
       FIG. 1  shows an example of an internal environment of a mobile terminal on which an antenna design solution provided in this disclosure is based. As shown in  FIG. 1 , the mobile terminal may include a display screen  11 , a printed circuit board PCB  13 , a PCB grounding plate  15 , a side frame  17 , and a rear cover  19 . The display screen  11 , the printed circuit board PCB  13 , the PCB grounding plate  15 , and the rear cover  19  may be separately disposed at different layers, and these layers may be parallel to each other. A plane on which the layers are located may be referred to as an X-Y plane, and a direction perpendicular to the X-Y plane is a Z direction. In other words, the display screen  11 , the printed circuit board PCB  13 , the PCB grounding plate  15 , and the rear cover  17  may be distributed at different layers in the Z direction. 
     The printed circuit board PCB  13  may be an FR-4 dielectric board, or may be a Rogers (Rogers) dielectric board, or may be a dielectric board mixing Rogers and FR-4, or the like. Herein, FR-4 is a grade designation for a flame-retardant material, and the Rogers dielectric board is a high-frequency board. 
     The rear cover  19  may be a rear cover made of an insulating material, for example, a glass rear cover or a plastic rear cover. The rear cover  19  may alternatively be a metal rear cover. If the mobile terminal shown in  FIG. 1  is a terminal of a full-metal ID, the rear cover  19  is a metal rear cover. 
     The PCB grounding plate  15  is grounded, and may be disposed between the printed circuit board PCB  13  and the rear cover  19 . The PCB grounding plate  15  may also be referred to as a PCB baseboard. Specifically, the PCB grounding plate  15  may be a metal layer etched on a surface of the PCB  13 , and the metal layer may also be connected to a metal frame (not shown) by using a series of metal spring plates, to be integrated with the metal frame. The PCB grounding plate  15  may be configured to ground an electronic component carried on the printed circuit board PCB  13 . Specifically, the electronic component carried on the printed circuit board PCB  13  may be grounded through wiring to the PCB grounding plate  15 , to prevent a user from getting an electric shock or prevent a device from being damaged. 
     The side frame  17  may be disposed on an edge of the printed circuit board PCB  13  and an edge of the PCB grounding plate  15 , and may cover the printed circuit board PCB  13  and the PCB grounding plate  15  between the rear cover  19  and the display screen  11  from a side edge, to be dustproof and waterproof. In an implementation, the side frame  17  may include four metal edges, and the four metal edges may be disposed around the display screen  11 , the printed circuit board PCB  13 , the PCB grounding plate  15 , and the rear cover  19 . In another implementation, the side frame  17  may include only two metal edges, and the two metal edges may be disposed on two sides of the display screen  11 , the printed circuit board PCB  13 , the PCB grounding plate  15 , and the rear cover  19  in a Y direction. The two implementations constitute no limitation. The side frame  17  may alternatively present another design style, such as a side frame  17  with a single metal edge. This is not limited in this disclosure. 
     The printed circuit board PCB  13  may be a mainboard in the mobile terminal. An antenna apparatus  100  provided in this disclosure is disposed at a position between the printed circuit board PCB  13  and the side frame  17 . In other words, the antenna apparatus  100  may be disposed at an edge position of the printed circuit board PCB  13 . As shown in  FIG. 2 , a side board  101  is disposed in the mobile terminal, the side board  101  is located on an edge of the printed circuit board PCB  13 , the side board  101  may be perpendicular to the printed circuit board PCB  13 , and the antenna apparatus  100  is disposed on the side board  101 , in other words, the side board  101  is a board for bearing the antenna apparatus  100 . In this disclosure, the antenna apparatus  100  may be disposed at positions on left and right sides of the mobile terminal, so that small space is occupied, and working of another antenna apparatus is not affected. The antenna apparatus  100  may be disposed on both the left side and the right side of the mobile terminal. In an implementation, the antenna apparatus  100  may be disposed at a position close to a top part of the mobile terminal, to avoid a handheld area (when holding the mobile terminal, a user usually tends to hold an area that is in a middle part and near a bottom part of the mobile terminal, and rarely holds a top area). In this way, performance stability of the antenna apparatus can be ensured. In an implementation, the mainboard and the side board each may be an FR-4 dielectric board with a thickness of 0.8 mm, and main ground is disposed on the mainboard, that is, a ground plane (namely, the foregoing PCB grounding plate  15 ) on the mainboard. 
     Referring to  FIG. 3 ,  FIG. 4 , and  FIG. 6 , the antenna apparatus  100  includes a grounding plate  10 , a monopole  20 , a first feeding unit  30 , and a second feeding unit  40 . In  FIG. 3 , reference numerals  10  and  20  indicate areas in pointed dotted boxes. Specifically, the grounding plate  10  may be a metal sheet structure, or may be a metal layer disposed on a dielectric board. As shown in  FIG. 3 , the grounding plate  10  is printed on a surface of the side board  101 . The grounding plate  10  is electrically connected to ground on the mainboard (namely, the printed circuit board PCB  13 ) of the mobile terminal. The monopole  20  may be a metal strip structure, or may be a microstrip structure disposed on the dielectric board. As shown in  FIG. 3 , the monopole  20  is printed on the surface of the side board  101  and is coplanar with the grounding plate  10 . In the embodiment shown in  FIG. 3 , the first feeding unit  30  and the second feeding unit  40  are printed on the surface of the side board  101 , and the surface on which the first feeding unit  30  and the second feeding unit  40  are located is disposed oppositely to a surface on which the grounding plate  10  and the monopole  20  are located. 
     A slot  12  is disposed on the grounding plate  10 , the slot  12  includes a first slot  121  and a second slot  122  that interpenetrate each other, and the second slot  122  extends from the first slot  121  to an edge of the grounding plate  10 . In other words, the slot  12  on the grounding plate  10  forms an opening at an edge position of the grounding plate  10 , so that the monopole  20  extends into the slot  12  through the opening. The monopole  20  includes a first stub  21  and a second stub  22 . The second stub  22  extends from the first stub  21  into the second slot  122 , in other words, the second stub  22  extends from an opening position of the slot  12  into the slot  12 . The second stub  22  extends to a position of the second slot  122 . Specifically, in an implementation, the second stub  22  extends to an intersection between the second slot  122  and the first slot  121 . In another implementation, the second stub  22  may alternatively extend into the first slot  121 , or an end point to which the second stub  22  extends is located inside the second slot  122  or at a middle position of the second slot  122 . The second stub  22  is insulated from the grounding plate  10  by using a gap, in other words, the second stub  22  is not in contact with an inner wall of the slot  12 . Specifically, the second stub  22  is at a central position in the second slot  122 . The second stub  22  and the second slot  122  form a feeding structure. The first feeding unit  30  is electrically connected to the grounding plate  10  and is configured to feed the feeding structure, to excite a first radiation mode of the antenna apparatus, where the grounding plate  10  and the second slot  122  are used as radiators in the first radiation mode. The second feeding unit  40  is electrically connected to the second stub  22  and performs feeding as the feeding structure, to excite a second radiation mode of the antenna apparatus, where the second stub  22  and the grounding plate  10  are used as radiators in the second radiation mode. A polarization direction in the first radiation mode is orthogonal to a polarization direction in the second radiation mode. 
     According to the antenna apparatus provided in this embodiment of this disclosure, two radiation modes of the antenna apparatus can be implemented by using a feeding structure formed after the monopole  20  is coupled with the grounding plate  10 . In this disclosure, the grounding plate  10  is used as a main radiator, so that the antenna apparatus has balanced high performance, in other words, radiation performance is stable and of high quality, and a dual-antenna effect is implemented by using a simple and compact structure. In the two radiation modes, polarization directions of the antenna apparatus are orthogonal, so that the antenna apparatus has high isolation. 
     As shown in  FIG. 7 , in an implementation, the first feeding unit  30  excites an in-phase current loop around the first slot  121 , and the in-phase current loop excites currents on the grounding plate  10  in a first direction, to form the first radiation mode. The first direction is an X direction in  FIG. 7 . 
     In the first radiation mode, the first slot  121  on the grounding plate  10  may be considered as two opening-to-opening open-circuit slots. Each open circuit works in a quarter-wave mode, and phases in the two quarter-wave modes are opposite. Specifically, the first slot  121  extends in the first direction. In the first direction, from one end A to the other end B of the first slot  121 , an electric field changes from null (that is, a position on the grounding plate  10 , where the position may be considered as a short-circuit point) to a maximum value (that is, a position at which the second slot  122  intersects with the first slot  121 , where in an implementation, a start point of the second slot  122  is located at a central position in the first slot  121 ); and after the electric field passes through the second slot  122 , a direction of the electric field is reversed, and the electric field changes from a reverse maximum value to null. In this way, currents surround the first slot  121  to form a loop of in-phase currents in a same direction. In the embodiment shown in  FIG. 7 , the direction of the in-phase current loop is a current in a clockwise direction around the first slot  121 . The in-phase currents may excite the currents on the grounding plate  10  in the first direction (in the embodiment shown in  FIG. 7 , a current direction on the grounding plate  10  is horizontally leftward), so that the grounding plate  10  becomes a main radiator, and a polarization direction is the first direction. 
     As shown in  FIG. 8 , in an implementation, the second feeding unit  40  excites generation of currents on the monopole  20  and the grounding plate  10 . Currents on the first stub  21  are distributed in the first direction, and currents on the second stub  22  are distributed in a second direction. For the monopole  20 , the currents flow from a bottom part of the second stub  22  to the first stub  21  in the second direction (that is, the Y direction), and the currents separately flow leftward and rightward on the first stub  21 . In this way, the currents on the first stub  21  that are located on two sides of the second stub  22  are in opposite directions, in other words, mutually reversed components of the currents on the first stub  21  are formed. The currents on the grounding plate  10  include currents distributed in the first direction and currents distributed in the second direction. As shown in  FIG. 8 , the currents on the grounding plate  10  flow from a bottom part of the grounding plate  10  to a top part of the grounding plate  10  in the second direction (the Y direction). At the top part of the grounding plate  10 , the currents all flow to the second slot  122 . In this way, mutually reversed components of the currents are formed at the top part of the grounding plate  10 . The currents on the first stub  21  and the currents on the grounding plate  10  that are distributed in the first direction have mutually reversed components, and the currents on the grounding plate  10  in the second direction are in a same direction as the currents on the second stub  22 . Therefore, this mode is the second radiation mode, and the first direction is perpendicular to the second direction. In other words, the currents on the monopole  20  and the grounding plate  10  include the currents distributed in the first direction and the currents distributed in the second direction, and the currents in the first direction are in mirrored distribution by using the second stub  22  as an axis of symmetry, in other words, the currents in the first direction have mutually reversed components and therefore do not form effective radiation, and only the currents distributed in the second direction contribute to radiation, to form the second radiation mode. 
     The second radiation mode is a monopole  20  mode. In an implementation, the monopole  20  and the grounding plate  10  are distributed in an axisymmetric structure by using the second stub  22  as a central axis, and the second stub  22  is a strip structure. The currents in the first direction have mutually reversed components that offset each other. Therefore, in the second radiation mode, a current direction is only the second direction (that is, the Y direction), the second stub  22  and two edges  11  of the grounding plate  10  form radiation, and the two edges  11  of the grounding plate  10  are edges of the grounding plate  10  that extend in a same direction as the second stub  22 , are referred to as radiation edges  11 , and are distributed on the two sides of the second stub  22 . For the monopole  20 , the currents on the second stub  22  flow to the first stub  21  from a tail end that is of the second stub  22  that is away from the first stub  21 , and separately flow, on the first stub  21 , to two ends of the first stub  21 . Therefore, the currents on the first stub  21  that are distributed on the two sides of the second stub  22  are in opposite directions, and can offset each other. For the grounding plate  10 , currents that flow to the second slot  122  are formed on an edge  13  of the grounding plate  10 . The edge  13  of the grounding plate  10  is an edge connected between the two radiation edges  11 , in other words, an edge on which the second slot  122  is located. Currents on the edge are all in the first direction, but are in opposite directions on the two sides of the second slot  122 , in other words, currents on one side flow leftward and currents on the other side flow rightward, and are mutually reversed currents. In this way, currents on the radiation edges  11  of the grounding plate  10  are in the second direction, and are in a same direction as the currents on the second stub  22 . In this way, the grounding plate  10  and the second stub  22  form radiators, and the grounding plate  10  is a main radiator. 
     In an implementation, as shown in  FIG. 3  to  FIG. 5 , the second stub  22  includes a connection part  211 , a first segment  212 , and a second segment  213 . An intersection between the second stub  22  and the first stub  21  is the connection part  211 , and the first segment  212  and the second segment  213  of the first stub  21  are symmetrically distributed on two sides of the connection part  211 . In this embodiment, the monopole  20  may be in a T-shape, a Y-shape, or another similar structure, and the first stub  21  may be in a linear shape, or may be in an arc shape or a serpentine shape. This is not limited in this disclosure. 
     In an implementation, both the first segment  212  and the second segment  213  are linear and collinear, and a shape in which the first stub  21  extends may affect an overall size of the antenna apparatus. A linear and collinear design helps save space. 
     In an implementation, the second stub  22  is linear, and the second stub  22  is perpendicular to the first segment  212 . In other words, the monopole  20  is T-shaped, has a simple structure, and is easy to manufacture. 
     Certainly, a shape of the monopole  20  in the antenna apparatus in this disclosure may be extended. For example, as shown in  FIG. 3  and  FIG. 4 , in an implementation, the first stub  21  includes a pair of bent segments  214 , one of the bent segments  214  is connected to an end that is of the first segment  212  and that is away from the connection part  211 , and the other bent segment  214  is connected to an end that is of the second segment  213  and that is away from the connection part  211 . The pair of bent segments  214  are symmetrically distributed on the two sides of the connection part  211  of the second stub  22 . 
     In an implementation, the pair of bent segments  214  and the second stub  22  are located on same sides of the first segment  212  and the second segment  213 . In other words, the bent segments  214  are located in space between the grounding plate  10  and both the first segment  212  and the second segment  213 . It is clear that this structure helps save space. 
     In an implementation, a part that is of the second stub  22  and that extends into the second slot  122  and the grounding plate  10  on an edge of the second slot  122  jointly form a CPW (Coplanar Waveguide, coplanar waveguide) feeding structure. 
     In an implementation, in the first radiation mode, electric field distribution of the CPW feeding structure is a differential mode, and in the second radiation mode, electric field distribution of the CPW feeding structure is a common mode. In the two radiation modes, electric field distribution of the CPW feeding structure is opposite. In this disclosure, the differential mode of the CPW feeding structure is used to excite the first radiation mode (also referred to as an in-phase current loop mode) of the antenna apparatus. In this disclosure, the common mode of the CPW feeding structure is used to excite the second radiation mode (also referred to as a monopole mode) of the antenna apparatus. 
     Specifically, the antenna apparatus provided in this disclosure may be an intra-band dual-antenna pair with balanced high performance and high isolation. Optionally, the antenna apparatus may be specifically a Sub-6G dual-antenna pair, and a working frequency of the antenna apparatus is 3.4 GHz to 3.6 GHz, in other words, the same frequency band is a Sub-6G frequency band. Optionally, the antenna apparatus may be specifically an intra-band dual-Wi-Fi antenna pair such as a dual-Wi-Fi antenna pair on a 2.4 GHz frequency band, in other words, the same frequency band is a Wi-Fi frequency band such as a 2.4 GHz Wi-Fi frequency band. This constitutes no limitation. The antenna apparatus may alternatively be an intra-band dual-antenna pair on another frequency band. 
     In another implementation, the antenna apparatus may alternatively work on different frequency bands in the two modes. For example, the antenna apparatus works on a first frequency band in the first radiation mode, and works on a second frequency band in the second radiation mode. Optionally, the first frequency band may include a Wi-Fi frequency band, and the second frequency band may include a Wi-Fi frequency band and a GPS frequency band. For example, the antenna apparatus may excite generation of a 2.4 GHz Wi-Fi resonance (the first frequency band is a 2.4 GHz Wi-Fi frequency band), or may excite generation of two resonances: a GPS L1 resonance and a 2.4 GHz Wi-Fi resonance (the second frequency band includes a 2.4 GHz Wi-Fi frequency band and a GPS L1 frequency band). This constitutes no limitation. The first frequency band and the second frequency band may be other frequency bands. 
     As shown in  FIG. 3  and  FIG. 4 , in an implementation, the first feeding unit  30  includes a first feeding point  31  and a first feeder  32 , an insulation slot  13  is disposed on the grounding plate  10 , the first feeding point  31  is located in the insulation slot  13 , and the first feeder  32  crosses the CPW feeding structure, and is electrically connected between the first feeding point  31  and the grounding plate  10 . 
     In an implementation, the first feeding unit  30  further includes a matching component  34 , the matching component  34  is electrically connected to the first feeder  32  and is grounded, and the matching component  34  is configured to adjust a resonance point and impedance matching that are of the antenna apparatus in the first radiation mode. By adjusting an antenna transmit coefficient, impedance, and the like, the matching component  34  may also adjust a frequency band range covered by the antenna apparatus. In this implementation, electrically connecting the matching component  34  to the first feeder  32  is specifically: first connecting a 0.2 pF capacitor in parallel, and then connecting a 5.6 nH inductor in series. 
     As shown in  FIG. 3  and  FIG. 5 , in an implementation, the second feeding unit  40  includes a second feeding point  41  and a second feeder  42 , and the second feeder  42  is electrically connected between the second feeding point  41  and the second stub  22  to excite the second radiation mode. Specifically, the second feeding point  41  may be disposed on the mainboard of the mobile terminal, or the second feeder  42  may be a microstrip printed on a surface of the mainboard. The second feeding unit  40  also includes a matching component  44 . The matching component  44  is electrically connected to the second feeding point  41  to affect the second feeding point  41 , and is configured to adjust a resonance point and impedance matching that are of the antenna apparatus in the second radiation mode. For example, electrically connecting the matching component  44  to the second feeding point  41  is specifically: first connecting a 0.5 pF capacitor in parallel, and then connecting a 0.4 pF capacitor in series. In the embodiment shown in  FIG. 5 , the second feeding point  41  and the matching component  44  are disposed on a bottom surface of the mainboard in the mobile terminal, the second feeder  42  is printed on a top surface of the mainboard, and the second feeder  42  and the second feeding point  41  may be electrically connected by using a metallized through-hole. 
     In an implementation, the first slot  121  is an axisymmetric structure, and a symmetric central axis of the first slot  121  is located on a center line that is of the second slot  122  and that is in the second direction. 
     In an implementation, as shown in  FIG. 7 , the first slot  121  includes a first end A and a second end B that are disposed oppositely, a direction in which the first end A extends to the second end B is the first direction, the antenna apparatus works in a quarter-wave mode from the first end A to a position of the second slot  122 , the antenna apparatus works in the quarter-wave mode from the second slot  122  to a position of the second end B, an electric field at the first end A and an electric field at the second end B are zero, and an electric field value at the position of the second slot  122  is the largest. 
     In an implementation, the monopole  20  and the grounding plate  10  are coplanar. 
     In an implementation, the antenna apparatus is a microstrip structure printed on a surface of a substrate, and the grounding plate  10  is electrically connected to the main ground on the mainboard in the mobile terminal. The grounding plate  10  and the monopole  20  are printed on an outer side of the side board  101 . The outer side of the side board  101  is a surface that is of the side board  101  and that faces the side frame  17  of the mobile terminal. A surface that is of the side board  101  and that faces the inside of the mobile terminal and the surface of the mainboard is an inner side of the side board  101 . The first feeding unit  30  and the second feeding unit  40  are disposed on the inner side of the side board  101 . The side board  101  includes a top part and a bottom part. The bottom part is an end that is of the side board  101  and that is connected to the mainboard, and the top part is an end that is of the side board  101  and that is away from the mainboard. In an implementation, the monopole  20  is disposed on the top part of the side board, and the first slot  121  in the slot  12  is located on the bottom part of the side board. 
     In this disclosure, a size of the mainboard in the mobile terminal is 155 mm×75 mm, and a height of the side board  101  (that is, a vertical distance between the bottom part and the top part of the side board) is 7 mm. A total size of the antenna apparatus in this disclosure is 15 mm×7 mm. 
     It can be learned through a simulation test (parasitic parameters and loss internal resistance that are of a lumped element are considered in simulation) that, in a working frequency range, for the in-phase current loop mode excited by the first feeding point, a reflection coefficient is less than −5.3 dB, impedance bandwidth of −6 dB is 7.6% (3.41 GHz to 3.68 GHz), total efficiency is between 48.0% and 60.3%, and average total efficiency is 55.8%; and for the monopole mode excited by the second feeding point, a reflection coefficient is less than −7.4 dB, impedance bandwidth of −6 dB is 7.1% (3.38 GHz to 3.63 GHz), total efficiency is between 52.1% and 63.0%, and average total efficiency is 59.1%. Therefore, two antennas in a dual-antenna pair have very balanced high performance. Because the modes are orthogonal, quite high isolation and a quite small envelope-related coefficient are obtained. On a working frequency band, the isolation is greater than −28 dB, and the envelope-related coefficient is less than 0.0015. 
     A camera and a terminal provided in the embodiments of this disclosure are described in detail above. The principle and embodiment of this disclosure are described herein through specific examples. The description about the embodiments of this disclosure is merely provided to help understand the method and core ideas of this disclosure. In addition, persons of ordinary skill in the art can make variations and modifications to this disclosure in terms of the specific embodiments and disclosure scopes according to the ideas of this disclosure. Therefore, the content of specification shall not be construed as a limitation to this disclosure.