Patent Publication Number: US-11387568-B2

Title: Millimeter-wave antenna array element, array antenna, and communications product

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Stage of International Patent Application No. PCT/CN2018/086197 filed on May 9, 2018, which is hereby incorporated by reference in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to the field of antenna technologies, and in particular, to a dual-band dual-polarized millimeter-wave antenna. 
     BACKGROUND 
     With development of the fifth generation mobile communications technology, a millimeter-wave frequency band is formally used. For example, two millimeter-wave frequency bands in the United States are respectively 28 GHz and 39 GHz. To meet operators&#39; requirements, antennas of communications products (such as smart phones and notebook computers) should cover both the millimeter-wave frequency bands. However, so far, there is no design of a dual-band dual-polarized millimeter-wave antenna in the industry. 
     SUMMARY 
     Embodiments of this application provide a design of a dual-band dual-polarized millimeter-wave antenna. 
     According to a first aspect, this application provides a millimeter-wave antenna array element, including a ground layer, a first dielectric layer, a first radiation patch, a second dielectric layer, and a second radiation patch that are sequentially stacked, the millimeter-wave antenna array element further includes a first feeding part and a second feeding part; at least a part of the first feeding part is disposed inside the first dielectric layer, or inside the second dielectric layer, or between the first dielectric layer and the second dielectric layer, and the first feeding part is insulated from the first radiation patch, the second radiation patch, and the ground layer; at least a part of the second feeding part is disposed inside the first dielectric layer, or inside the second dielectric layer, or between the first dielectric layer and the second dielectric layer, and the second feeding part is insulated from the first feeding part, the first radiation patch, the second radiation patch, and the ground layer; and the first feeding part and the second feeding part are electrically connected to a feed, to excite electromagnetic wave signals of two frequency bands to each of the first radiation patch and the second radiation patch. Specifically, the electromagnetic wave signals are excited through spatial coupling. In addition, electromagnetic wave signals with two polarizations are generated on each of the first radiation patch and the second radiation patch. In other words, electromagnetic wave signals with two polarizations are generated on the first radiation patch. Specifically, orthogonally polarized electromagnetic wave signals are generated on the first radiation patch, and orthogonally polarized electromagnetic wave signals are also generated on the second radiation patch. 
     For example, the electromagnetic wave signals of the two frequency bands may be electromagnetic wave signals of a frequency band range of 26.5 GHz to 29.5 GHz and electromagnetic wave signals of a frequency band range of 37.0 GHz to 40.5 GHz. 
     In this application, the first feeding part and the second feeding part are disposed, the first feeding part is spatially coupled to the first radiation patch and the second radiation patch, and the second feeding part is spatially coupled to the first radiation patch and the second radiation patch, so that electromagnetic wave signals with two different polarizations of a first frequency band are excited on the first radiation patch, and electromagnetic wave signals with two different polarizations of a second frequency band are excited on the second radiation patch. In this way, the millimeter-wave antenna array element provided in this application can be dual-band and dual-polarized. Specifically, a frequency of an electromagnetic wave signal on the first radiation patch is lower than a frequency of an electromagnetic wave signal on the second radiation patch, the first radiation patch is a low-frequency radiator, and the second radiation patch is a high-frequency radiator. 
     In an implementation, when at least a part of the first feeding part and at least a part of the second feeding part are disposed between the first dielectric layer and the second dielectric layer, the first feeding part includes a first feeding plate and a first conducting wire, the second feeding part includes a second feeding plate and a second conducting wire, a first accommodation hole and a second accommodation hole are disposed on the first radiation patch, the first feeding plate is disposed in the first accommodation hole, the second feeding plate is disposed in the second accommodation hole, the first conducting wire is electrically connected between the first feeding plate and the feed, and the second conducting wire is electrically connected between the second feeding plate and the feed. In this implementation, the first feeding plate and the second feeding plate are disposed at the same layer as the first radiation patch. In this way, only one dielectric layer needs to be disposed between the first radiation patch and the ground layer, and only one dielectric layer needs to be disposed between the second radiation patch and the first radiation patch. This helps reduce an overall size of the millimeter-wave antenna array element. In this architecture, it is equivalent that the millimeter-wave antenna array element provided in this application is disposed on a double-layer PCB, and the double-layer PCB has two dielectric layers (namely, the first dielectric layer and the second dielectric layer) and three metal layers (namely, the ground layer, the first radiation patch, and the second radiation patch). Specifically, the first feeding plate and the second feeding plate may be in any shape such as a circle, a triangle, or a square. 
     In another implementation, the first feeding plate and the second feeding plate may alternatively be disposed in other locations, for example, embedded in the first dielectric layer. In other words, a metal layer is further disposed inside the first dielectric layer. In this way, it is equivalent that the millimeter-wave antenna array element in this application is disposed on a multi-layer PCB. Certainly, the first feeding plate and the second feeding plate may alternatively be embedded in the second dielectric layer. Alternatively, the first feeding plate and the second feeding plate are respectively disposed inside the first dielectric layer and the second dielectric layer. That is, the first feeding plate and the second feeding plate may be disposed at different layers. 
     In an implementation, the first conducting wire vertically extends from the first feeding plate to the ground layer, and extends out of the millimeter wave array element from the ground layer, and the second conducting wire vertically extends from the second feeding plate to the ground layer, and extends out of the millimeter wave array element from the ground layer. Lead-out directions of the first conducting wire and the second conducting wire are limited in this implementation. This architecture helps reduce impact of the first feeding part and the second feeding part on antenna radiation performance, reduce a feeding loss, and improve an antenna gain. 
     The first conducting wire and the second conducting wire may be coaxial cables. An inner conductor of the coaxial cable extends into the first dielectric layer and is electrically connected to the first feeding plate, and an outer conductor of the coaxial cable is electrically connected to the ground layer. Specifically, openings may be disposed at the ground layer and the first dielectric layer, and the openings extend from the ground layer to the first feeding plate. In this way, the first conducting wire and the second conducting wire may extend into the openings and be electrically connected to the first feeding plate and the seconding feeding plate. 
     In an implementation, the first radiation patch is symmetrically distributed along both a first axis and a second axis, the first axis is perpendicular to the second axis, and the first feeding plate and the second feeding plate are respectively disposed on the first axis and the second axis. 
     In an implementation, a center of the second radiation patch faces a center of the first radiation patch, and an area of the second radiation patch is less than an area of the first radiation patch. An outline of the first radiation patch is a cross shape, and the outline of the first radiation patch includes four straight line edges located on four sides and four └-shaped edges that are each connected between two adjacent straight line edges and that are located at four corners. An outline of the second radiation patch includes four side edges of a same shape that are located on four sides and that are sequentially connected. Each side edge includes one straight line edge and two L-shaped edges, the two L-shaped edges are bilaterally symmetrical on two sides of the straight line edge, and L-shaped edges of two adjacent side edges are connected. A through hole is disposed in a center area of the second radiation patch. In a specific implementation, the through hole may be but is not limited to a circle. Specific shape structures of the first radiation patch and the second radiation patch are not limited to those described in this implementation, and shapes of the first radiation patch and the second radiation patch may change based on a specific antenna matching requirement. 
     In an implementation, the millimeter-wave antenna array element further includes one or more resonators, the one or more resonators are distributed on a periphery of the second radiation patch and are insulated from the second radiation patch, and the one or more resonators are configured to improve isolation and a spread bandwidth of the millimeter-wave antenna array element. 
     In an implementation, there are four resonators, and the resonators are distributed pairwise opposite to each other on four sides of the second radiation patch. 
     In an implementation, each resonator is in a strip shape, an extension direction of two resonators that are disposed opposite to each other is a first direction, and an extension direction of the other two resonators that are disposed opposite to each other is a second direction. The first direction is perpendicular to the second direction, and in the first direction and the second direction, a size of the second radiation patch is less than or equal to an extension size of each resonator. In other words, a vertical projection of the second radiation patch on the resonator coincides with the resonator or falls within a range of the resonator. 
     According to a second aspect, this application provides an array antenna, including a plurality of millimeter-wave antenna array elements according to the first aspect. The plurality of millimeter-wave antenna array elements are distributed in an array, all the first dielectric layers are coplanar and jointly form a complete dielectric slab, all the second dielectric layers are coplanar and jointly form a complete dielectric slab, and all the ground layers are coplanar and interconnected as a whole. 
     In an implementation, the array antenna further includes an isolation structure, the isolation structure is disposed between adjacent millimeter-wave antenna array elements, the isolation structure includes an isolation plate and a plurality of metal through holes, the isolation plate is disposed on a side that is of the second dielectric layers and that is away from the first dielectric layers, the isolation plate is disposed between adjacent second radiation patches, and the plurality of metal through holes extend from the isolation plate to the ground layers. 
     In an implementation, in a direction perpendicular to the second dielectric layers, a height at which the isolation plate protrudes from the second dielectric layers is greater than a height at which the second radiation patches protrude from the second dielectric layers. 
     According to a third aspect, this application provides a communications product, including a feed source and the array antenna according to the second aspect, and the feed source is configured to feed electromagnetic wave signals into the first feeding part and the second feeding part. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic diagram of a communications product including a millimeter-wave antenna array element according to an implementation of this application; 
         FIG. 2  is a three-dimensional schematic diagram of a millimeter-wave antenna array element without a first dielectric layer and a second dielectric layer according to an implementation of this application; 
         FIG. 3  is a three-dimensional exploded schematic diagram of a millimeter-wave antenna array element in which a first dielectric layer and a second dielectric layer are separated according to an implementation of this application; 
         FIG. 4  is a schematic diagram of a cross section of a millimeter-wave antenna array element according to an implementation of this application; 
         FIG. 5  is a schematic diagram of a cross section of a millimeter-wave antenna array element in which a feed and a duplex circuit structure are added according to an implementation of this application; 
         FIG. 6  is a schematic planar diagram of a first radiation patch of a millimeter-wave antenna array element according to an implementation of this application; 
         FIG. 7  is a schematic planar diagram of a second radiation patch of a millimeter-wave antenna array element according to an implementation of this application; 
         FIG. 8  is a schematic diagram of a cross section of a millimeter-wave antenna array element according to an implementation of this application; 
         FIG. 9  is a schematic diagram of an array antenna (a 2×2 array) according to an implementation of this application; 
         FIG. 10  is a schematic diagram of a cross section of an array antenna according to an implementation of this application; 
         FIG. 11  is a schematic diagram of curves of isolation obtained before and after an array antenna uses an isolation structure according to this application; 
         FIG. 12  is a system performance diagram of an array antenna according to this application; 
         FIG. 13  is a radiation diagram of a millimeter-wave antenna array element in a low frequency band according to this application; 
         FIG. 14  is a radiation diagram of a millimeter-wave antenna array element in a high frequency band according to this application; and 
         FIG. 15  is a radiation pattern of an array antenna (in an example of a 2×2 array) according to this application. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The following describes the embodiments of this application with reference to accompanying drawings. 
     A millimeter-wave antenna array element and an array antenna provided in this application are applied to a communications product. The communications product may be a mobile terminal such as a mobile phone operating within a millimeter-wave frequency band range of a 5G communications system. As shown in  FIG. 1 , an antenna  100  is disposed on the back of a communications product  200  (for example, a mobile phone), and signal receiving and sending may be implemented by using a rear housing of the communications product  200  or a gap on the rear housing. The antenna  100  includes a plurality of antenna array elements  10  arranged in an array, and each antenna array element  10  is a millimeter-wave antenna array element. 
     Referring to  FIG. 2 ,  FIG. 3 , and  FIG. 4 , a millimeter-wave antenna array element  10  provided in an implementation of this application includes a ground layer  12 , a first dielectric layer  13 , a first radiation patch  14 , a second dielectric layer  15 , and a second radiation patch  16  that are sequentially stacked. The first dielectric layer  13  and the second dielectric layer  15  are base material layers, and are configured to carry the ground layer  12 , the first radiation patch  14 , and the second radiation patch  16 . The first dielectric layer  13  and the second dielectric layer  15  may be of insulation materials such as a PCB base material and a ceramic base material. In another implementation, the first dielectric layer  13  and the second dielectric layer  15  may alternatively be of a flexible material. In a specific implementation, the first dielectric layer  13  and the second dielectric layer  15  are dielectrics. 
     The millimeter-wave antenna array element  10  further includes a first feeding part  17  and a second feeding part  18 . At least a part of the first feeding part  17  is disposed inside the first dielectric layer  13 , or inside the second dielectric layer  15 , or between the first dielectric layer  13  and the second dielectric layer  15 . The first feeding part  17  is insulated from the first radiation patch  14 , the second radiation patch  16 , and the ground layer  12 . At least a part of the second feeding part  18  is disposed inside the first dielectric layer  13 , or inside the second dielectric layer  15 , or between the first dielectric layer  13  and the second dielectric layer  15 . The second feeding part  18  is insulated from the first feeding part  17 , the first radiation patch  14 , the second radiation patch  16 , and the ground layer  12 . Specifically, in an implementation, being insulated herein means that features are insulated through isolation of dielectrics, and the dielectrics may be the first dielectric layer  13  and the second dielectric layer  15 . 
     The first feeding part  17  and the second feeding part  18  may be disposed at a same layer, or may be disposed at different layers. The first feeding part  17  and the second feeding part  18  are electrically connected to a feed, to excite electromagnetic wave signals of two frequency bands to each of the first radiation patch  14  and the second radiation patch  16  through spatial coupling, and generate electromagnetic wave signals with two polarizations on each of the first radiation patch  14  and the second radiation patch  16 . In other words, electromagnetic wave signals with two polarizations are generated on the first radiation patch  14 . Specifically, orthogonally polarized electromagnetic wave signals are generated on the first radiation patch  14 , and orthogonally polarized electromagnetic wave signals are also generated on the second radiation patch  16 . 
     For example, the electromagnetic wave signals of the two frequency bands may be electromagnetic wave signals of a frequency band range of 26.5 GHz to 29.5 GHz and electromagnetic wave signals of a frequency band range of 37.0 GHz to 40.5 GHz. 
     In this application, the first feeding part  17  and the second feeding part  18  are disposed, the first feeding part  17  is spatially coupled to the first radiation patch  14  and the second radiation patch  16 , and the second feeding part  18  is spatially coupled to the first radiation patch  14  and the second radiation patch  16 , so that electromagnetic wave signals with two different polarizations of a first frequency band are excited on the first radiation patch  14 , and electromagnetic wave signals with two different polarizations of a second frequency band are excited on the second radiation patch  16 . In this way, the millimeter-wave antenna array element provided in this application can be dual-band and dual-polarized. Specifically, a frequency of an electromagnetic wave signal on the first radiation patch  14  is lower than a frequency of an electromagnetic signal on the second radiation patch  16 , that is, the first radiation patch  14  is a low-frequency radiator, and the second radiation patch  16  is a high-frequency radiator. 
     A thickness of the first dielectric layer  13  is greater than a thickness of the second dielectric layer  15 . Herein, the “thickness” is a size in a direction perpendicular to the first dielectric layer  13  and the second dielectric layer  15 . In a specific implementation, a vertical distance between the first radiation patch  14  and the ground layer  12  is 0.7 mm, and a vertical distance between the second radiation patch  16  and the ground layer  12  is 0.9 mm. 
     Specifically, the ground layer  12  is a metal layer formed on a bottom surface of the first dielectric layer  13 . The ground layer  12  may be a large-area copper foil layer that covers all the bottom surface of the first dielectric layer  13 , or the ground layer  12  may cover only a part of the bottom surface of the first dielectric layer  13 . The first radiation patch  14  is a metal layer formed on a top surface of the first dielectric layer  13 , the first radiation patch  14  is sandwiched between the first dielectric layer  13  and the second dielectric layer  15 , and the second radiation patch  16  is a metal layer formed on a top surface of the second dielectric layer  15 . 
     In an implementation, the first feeding part  17  includes a first feeding plate  171  and a first conducting wire  172 , and the second feeding part  18  includes a second feeding plate  181  and a second conducting wire  182 . A first accommodation hole  141  and a second accommodation hole  142  are disposed on the first radiation patch  14 , the first feeding plate  171  is disposed in the first accommodation hole  141 , and the second feeding plate  181  is disposed in the second accommodation hole  142 . The first conducting wire  172  is electrically connected between the first feeding plate  171  and the feed, and the second conducting wire  182  is electrically connected between the second feeding plate  181  and the feed. In this implementation, the first feeding plate  171  and the second feeding plate  181  are disposed at the same layer as the first radiation patch  14 . In this way, only one dielectric layer needs to be disposed between the first radiation patch  14  and the ground layer  12 , and only one dielectric layer needs to be disposed between the second radiation patch  16  and the first radiation patch  14 . This helps reduce an overall size of the millimeter-wave antenna array element. In this architecture, it is equivalent that the millimeter-wave antenna array element provided in this application is disposed on a double-layer PCB, and the double-layer PCB has two dielectric layers (namely, the first dielectric layer  13  and the second dielectric layer  15 ) and three metal layers (namely, the ground layer  12 , the first radiation patch  14 , and the second radiation patch  16 ). Specifically, the first feeding plate  171  and the second feeding plate  181  may be in any shape such as a circle, a triangle, or a square. 
     In another implementation, the first feeding plate  171  and the second feeding plate  181  may alternatively be disposed in other locations, for example, embedded in the first dielectric layer  13 . In other words, a metal layer is further disposed inside the first dielectric layer  13 . In this way, it is equivalent that the millimeter-wave antenna array element in this application is disposed on a multi-layer PCB. Certainly, the first feeding plate  171  and the second feeding plate  181  may alternatively be embedded in the second dielectric layer  15 . Alternatively, the first feeding plate  171  and the second feeding plate  181  are respectively disposed inside the first dielectric layer  13  and the second dielectric layer  15 . That is, the first feeding plate  171  and the second feeding plate  181  may be disposed at different layers. 
     In an implementation, the first conducting wire  172  vertically extends from the first feeding plate  171  to the ground layer  12 , and extends out of the millimeter wave array element  10  from the ground layer  12 , and the second conducting wire  182  vertically extends from the second feeding plate  181  to the ground layer  12 , and extends out of the millimeter wave array element  10  from the ground layer  12 . Lead-out directions of the first conducting wire  172  and the second conducting wire  182  are limited in this implementation. This architecture helps reduce impact of the first feeding part  17  and the second feeding part  18  on antenna radiation performance, reduce a feeding loss, and improve an antenna gain. 
     The first conducting wire  172  and the second conducting wire  182  may be coaxial cables. An inner conductor of the coaxial cable extends into the first dielectric layer  13  and is electrically connected to the first feeding plate  171 , and an outer conductor of the coaxial cable is electrically connected to the ground layer  12 . Specifically, two openings  11  may be disposed at the ground layer  12  and the first dielectric layer  13 . As shown in  FIG. 3 , the openings  11  extend from the ground layer  12  to the first feeding plate  171  and the second feeding plate  181 . In this way, the first conducting wire  172  and the second conducting wire  182  may extend into the openings  11  and be electrically connected to the first feeding plate  171  and the seconding feeding plate  181 . A diameter of the opening  11  at the ground layer  12  may be greater than a diameter of the opening  11  at the first dielectric layer  13 . In this way, the first conducting wire  172  and the second conducting wire  182  can easily extend into the openings  11 . 
     The first conducting wire  172  and the second conducting wire  182  may alternatively be probes or other feeding structures. 
     As shown in  FIG. 5 , in an implementation, the first conducting wire  172  and the second conducting wire  182  each are connected to the feed through a duplexer (or a duplex circuit)  20 . The feed has two ports for inputting to the duplexer, and the ports each are configured to input electromagnetic wave signals of a different frequency band. In an implementation, an input end of a duplexer  20  connected to the first conducting wire  172  includes a first port  31  and a second port  32 , and an input end of a duplexer  20  connected to the second conducting wire  182  includes a third port  33  and a fourth port  34 . The first port  31  and the third port  33  are configured to perform low-frequency feeding, and the second port  32  and the fourth port  34  are configured to perform high-frequency feeding. 
     As shown in  FIG. 6 , in an implementation, the first radiation patch  14  is symmetrically distributed along both a first axis A 1  and a second axis A 2 , and the first axis A 1  is perpendicular to the second axis A 2 . The first feeding plate  171  and the second feeding plate  181  are respectively disposed on the first axis A 1  and the second axis A 2 . In other words, the first axis A 1  passes through the first feeding plate  171 , and the second axis A 2  passes through the second feeding plate  181 . In this way, the millimeter-wave antenna array element can enable two polarizations of electromagnetic wave signals to be in an orthogonal mode. Specifically, a center of the first feeding plate  171  may be disposed on the first axis A 1 , and a center of the second feeding plate  181  may be disposed on the second axis A 2 . A specific location of the first feeding plate  171  on the first axis A 1  and a specific location of the second feeding plate  181  on the second axis A 2  are determined based on matching performance of the millimeter-wave antenna array element. However, sometimes, due to a matching requirement, the two feeding radiation plates ( 171  and  181 ) do not necessarily need to be disposed on the axes (A 1  and A 2 ). 
     In an implementation, a center of the second radiation patch  16  faces a center of the first radiation patch  14 , and an area of the second radiation patch  16  is less than an area of the first radiation patch  14 . An outline of the first radiation patch  14  is a cross shape, and the outline of the first radiation patch  14  includes four straight line edges  143  located on four sides and four └-shaped edges  144  that are each connected between two adjacent straight line edges  143  and that are located at four corners. 
     As shown in  FIG. 7 , an outline of the second radiation patch  16  includes four side edges  161  of a same shape that are located on four sides and that are sequentially connected. Each side edge includes one straight line edge  162  and two L-shaped edges  163 , the two L-shaped edges  163  are bilaterally symmetrical on two sides of the straight line edge  162 , and L-shaped edges  163  of two adjacent side edges  161  are connected. A through hole  164  is disposed in a center area of the second radiation patch  16 . In a specific implementation, the through hole  164  may be but is not limited to a circle. 
     Specific shape structures of the first radiation patch  14  and the second radiation patch  16  are not limited to those described in this implementation, and shapes of the first radiation patch  14  and the second radiation patch  16  may change based on a specific antenna matching requirement. 
     In an implementation, the millimeter-wave antenna array element  10  further includes one or more resonators  19 , the one or more resonators  19  are distributed on a periphery of the second radiation patch  16  and are insulated from the second radiation patch  16 , and the one or more resonators  19  are configured to improve isolation and a spread bandwidth of the millimeter-wave antenna array element  10 . 
     In an implementation, there are four resonators  19 , and the resonators are distributed pairwise opposite to each other on four sides of the second radiation patch  16 . 
     In an implementation, each resonator  19  is in a strip shape, an extension direction of two resonators  19  that are disposed opposite to each other is a first direction, and an extension direction of the other two resonators  19  that are disposed opposite to each other is a second direction. The first direction is perpendicular to the second direction, and in the first direction and the second direction, a size of the second radiation patch  16  is less than or equal to an extension size of each resonator  19 . In the first direction and the second direction, a center of the second radiation patch  16  faces a center of the resonator  19 . In this way, an orthographic projection of the second radiation patch  16  on any resonator  19  falls within a range of the resonator  19  or coincides with the resonator  19 . This architecture herein helps improve isolation between millimeter-wave antenna array elements. 
     As shown in  FIG. 8 , in an implementation, an area that is on a surface of the second dielectric layer  15  and that is used to adhere to the second radiation patch  16  is used as a reference surface  151 . A height h 1  at which the resonators  19  that are disposed on four sides of the second radiation patch  16  protrude from the reference surface  151  is greater than a height h 2  at which the second radiation patch  16  protrudes from the reference surface  151 . In this way, an isolation effect can be better improved. Specifically, a groove may be disposed on the top surface of the second dielectric layer  15 , a shape of the groove is consistent with a shape of the second radiation patch  16 , the second radiation patch  16  is disposed in the groove, and a bottom surface of the groove is the reference surface  151 . 
     An array antenna provided in this application includes a plurality of millimeter-wave antenna array elements distributed in an array. All the first dielectric layers  13  are coplanar and jointly form a complete dielectric slab, all the second dielectric layers  15  are coplanar and jointly form a complete dielectric slab, and all the ground layers  12  are coplanar and interconnected as a whole. In other words, the array antenna includes a first dielectric slab and a second dielectric slab that are stacked, a bottom surface of the first dielectric slab is the ground layers  12 , a plurality of first radiation patches  14  arranged in an array are disposed on a top surface of the first dielectric slab, and a plurality of second radiation patches  16  arranged in an array and the resonators  19  arranged around each second radiation patch  16  are disposed on a top surface (to be specific, a surface that is of the second dielectric slab and that is away from the first dielectric slab) of the second dielectric slab. Each second radiation patch  16  is disposed opposite to each first radiation patch  14 . The first radiation patch  14 , the second radiation patch  16 , the resonators  19  around the second radiation patch  16 , and a part of the ground layers  12  facing the first radiation patch  14  jointly form a millimeter-wave antenna array element. 
     As shown in  FIG. 9  and  FIG. 10 , in an implementation, the antenna further includes an isolation structure  40 . The isolation structure  40  is disposed between adjacent millimeter-wave antenna array elements  10 . The isolation structure  40  includes an isolation plate  41  and a plurality of metal through holes  42 . The isolation plate  41  is disposed on a side that is of the second dielectric layers  15  and that is away from the first dielectric layers  13 . In other words, the isolation plate  41  is located on a side: a top surface of the second dielectric layers  15 . Specifically, the isolation plate  41  may be directly disposed on the top surface of the second dielectric layers  15 . The isolation plate  41  is disposed between adjacent second radiation patches  16 , and the plurality of metal through holes  42  extend from the isolation plate  41  to the ground layers  12 . In the array antenna, the isolation structure  40  disposed between millimeter-wave antenna array elements that are distributed in a 2×2 array is in a cross shape. That is, the isolation plate  41  is in a cross shape, four quadrants are obtained through division by using the isolation plate  41 , and each millimeter-wave antenna array element  10  is disposed in one quadrant. 
     In an implementation, in a direction perpendicular to the second dielectric layers  15 , a height at which the isolation plate protrudes from the second dielectric layers  15  is greater than a height at which the second radiation patches  16  protrude from the second dielectric layers  15 . The isolation plate  41  may be a metal plate fastened on the top surface of the second dielectric layers  15 , or may be a metal layer formed on the top surface of the second dielectric layers  15  by using a PCB manufacturing process. 
       FIG. 11  shows isolation between two feeding parts (a first feeding part  17  and a second feeding part  18 ) of an antenna using the isolation structure  40  and an antenna that does not use the isolation structure  40 . S 21  is a coupling coefficient of the first feeding part  17  of the antenna that does not use the isolation structure  40 , S 21 ′ is a coupling coefficient of the first feeding part  17  of the antenna using the isolation structure  40 , S 41  is a coupling coefficient of the second feeding part  18  of the antenna that does not use the isolation structure  40 , and S 41 ′ is a coupling coefficient of the second feeding part  18  of the antenna using the isolation structure  40 . It can be learned from  FIG. 11  that isolation of an antenna is improved after the isolation structure is used. 
       FIG. 12  is a system performance diagram of an antenna according to this application. S 11  and S 22  respectively represent reflection of the first feeding part  17  and the second feeding part  18 . It can be learned from the figure that values of S 11  and S 22  in both a high frequency band and a low frequency band are less than −10 dB. −10 dB is an acceptable value in terms of antenna performance. S 21  represents isolation between the first feeding part  17  and the second feeding part  18 . It can be learned from the figure that values of S 21  in both the high frequency band and the low frequency band are less than −15 dB. −15 dB is an acceptable value in terms of antenna performance. This meets an antenna design requirement. 
       FIG. 13  is a radiation diagram of a millimeter-wave antenna array element in a low frequency band according to this application. As shown in the figure, a direction of maximum radiation energy is perpendicular to a plane of a radiator, and a radiation side lobe value meets a design requirement. 
       FIG. 14  is a radiation diagram of a millimeter-wave antenna array element in a high frequency band according to this application. As shown in the figure, a direction of maximum radiation energy is perpendicular to a plane of a radiator, and a radiation side lobe value meets a design requirement. 
       FIG. 15  is a radiation pattern of an antenna (in an example of a 2×2 array) according to this application. As shown in the figure, the 2×2 antenna array provides an expected gain. To be specific, a beam of a radiation main lobe is narrowed, so that radiation energy is better concentrated in a required direction. 
     The embodiments of this application are described in detail above. The principle and embodiments of this application are described herein through specific examples. The description about the embodiments of this application is merely provided to help understand the method and core ideas of this application. In addition, a person of ordinary skill in the art can make variations and modifications to this application in terms of the specific embodiments and application scopes according to the ideas of this application. Therefore, the content of specification shall not be construed as a limitation on this application.