Patent Publication Number: US-2023155295-A1

Title: Adapter Device, Feeder Device, and Antenna

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/CN2021/105095, filed on Jul. 8, 2021, which claims priority to Chinese Patent Application No. 202010670111.9, filed on Jul. 13, 2020. The disclosures of the aforementioned applications are hereby incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     This application relates to the field of antenna designs, and more specifically, to an adapter device, a feeder device, and an antenna. 
     BACKGROUND 
     In a feeder device of a base station antenna, a radio frequency signal often needs to be transmitted from a coaxial cable to an air dielectric microstrip, that is, the signal is transferred between the coaxial cable and the air dielectric microstrip. In an existing design, a cavity (or a reflection panel, namely, a ground plane) accommodating an air dielectric microstrip generally needs to be electroplated, and then an outer conductor of a coaxial cable is welded on them electroplated cavity (or the reflection panel), to implement electrical connection between the outer conductor of the coaxial cable and the cavity (or the reflection panel); and an inner conductor of the coaxial cable is electrically connected to the air dielectric microstrip. The manufacturing and processing costs of the feeder device with this design are high. 
     In another existing design, a coaxial cable is coupled to a cavity (or a reflection panel). In this design, an inner conductor of the coaxial cable is generally electrically connected to an air dielectric microstrip, an outer conductor of the coaxial cable is welded on a printed circuit board (PCB), and a ground plane of the PCB and the cavity (or the reflection panel) form capacitive coupling, to implement grounding of the outer conductor of the coaxial cable, which results in inconsistent electrical properties of capacitive coupling and makes it difficult for mass production. 
     SUMMARY 
     In view of the problems in the existing design that a device for transferring a signal between a coaxial cable and an air dielectric microstrip has inconsistent electrical properties and is unsuitable for mass production, this application provides an adapter device, a feeder device, and an antenna, in which stable coupling connection can be realized in a non-flat capacitive coupling manner, thereby achieving consistent electrical properties, and making it suitable for mass production. 
     According to a first aspect, an adapter device is provided, including a coaxial cable, an air dielectric microstrip, a ground plane, and a non-flat metal part. An outer conductor of the coaxial cable is electrically connected to the non-flat metal part, the non-flat metal part and the ground plane form non-flat capacitive coupling, and an inner conductor of the coaxial cable is electrically connected to the air dielectric microstrip. 
     According to the adapter device in the first aspect, the inner conductor of the coaxial cable is electrically connected to the air dielectric microstrip, the outer conductor of the coaxial cable is electrically connected to the non-flat metal part, and the non-flat metal part and the ground plane form non-flat capacitive coupling, so that the outer conductor of the coaxial cable is grounded. The non-flat capacitive coupling manner can realize stable coupling connection, thereby achieving consistent electrical properties, and making it suitable for mass production. 
     It should be understood that the ground plane may be a cavity, a reflection panel, or a ground structure in another form. This is not limited in this application. 
     It should be further understood that the ground plane may be a non-electroplated device, and therefore the costs can be greatly reduced. In embodiments of this application, the outer conductor of the coaxial cable is electrically connected to the non-flat metal part, the non-flat metal part and the ground plane form non-flat capacitive coupling, and a radio frequency signal may be transmitted to the air dielectric microstrip through capacitive coupling, so that the ground plane (the cavity or the reflection panel) does not need to be electroplated. Alternatively, the ground plane may be an electroplated device. This is not limited in this application. 
     It should be further understood that the outer conductor of the coaxial cable may be welded to the non-flat metal part along an axial direction of the coaxial cable. To facilitate connection and assembly, a connection portion may be disposed on the non-flat metal part, so that the outer conductor of the coaxial cable can be more conveniently electrically connected to the connection portion by welding or in another manner, to implement the electrical connection between the outer conductor of the coaxial cable and the non-flat metal part. This is not limited in this application. 
     [oon] It should be further understood that adhesive may be filled between the non-flat metal part and the ground plane for fixing and insulating. Another material may be alternatively used for filling between the non-flat metal part and the ground plane for fixing and/or insulating. This is not limited in this application. 
     In a possible implementation of the first aspect, a first connection point at which the outer conductor of the coaxial cable is electrically connected to the non-flat metal part may be located at a middle portion of the non-flat capacitor in a length direction; or the first connection point at which the outer conductor of the coaxial cable is electrically connected to the non-flat metal part may be located at one of two ends of the non-flat capacitor in the length direction. Alternatively, the first connection point may be disposed at another position. This is not limited in this application. 
     A connection portion may be disposed at the first connection point on the non-flat metal part. The connection portion may be specifically a metal sheet with a hole at an end of the non-flat metal part, or may be another component having a clamping/clipping function. This is not limited in this application. 
     In a possible implementation of the first aspect, the first connection point may be disposed at a position that is on the coaxial cable and is close to a second connection point at which the inner conductor of the coaxial cable is electrically connected to the air dielectric microstrip. In other words, positions of the first connection point and the second connection point may be set as close as possible. It should be understood that as close as possible in this application means that, the positions of the first connection point and the second connection point are set as close as possible when a processing and/or assembly condition permits. For example, a distance between the first connection point and the second connection point may be less than or equal to 5 mm. This is not limited in this application. At a signal plane, current is formed between the first connection point and the second connection point; and at the ground plane, current in an opposite direction is formed between the first connection point and the second connection point. As a result, a current loop is formed between the first connection point and the second connection point. The positions of the first connection point and the second connection point are set as close as possible, so that performance of the feeder device can be improved, and performance of the antenna can be accordingly improved. 
     In a possible implementation of the first aspect, the non-flat capacitive coupling formed by the non-flat metal part and the ground plane may be non-flat multi-plane capacitive coupling. The multi-plane coupling may be, for example, three-plane coupling or four-plane coupling. However, this application is not limited thereto. 
     In several possible implementations of the first aspect, to adapt to a specific antenna structure, shapes, sizes, positions, and the like of components in the adapter device may have a plurality of forms, allowing the adapter device to be more flexibly used in the antenna structure. 
     In a possible implementation of the first aspect, the ground plane has a U-shaped groove structure, and the non-flat metal part is of a U-shaped structure. 
     In a possible implementation of the first aspect, the non-flat metal part and the ground plane form U-shaped capacitive coupling, and the non-flat metal part of the U-shaped structure is sleeved outside the coaxial cable. In this possible implementation, the problem of difficulty in mass production due to poor stability of capacitive coupling can be resolved. The U-shaped capacitive coupling (coupling in multiple planes) can ensure the coupling stability, that is, the U-shaped capacitor can ensure that the capacitance of the capacitor remains stable. In this way, the adapter device has consistent electrical properties and is suitable for mass production. When a material tolerance or an assembly tolerance is large, for example, when the non-flat metal part of the U-shaped structure clamped in the U-shaped groove structure of the ground plane shakes left and right, the U-shaped capacitive coupling structure can ensure that a sum of coupling gaps between two surfaces of the U-shaped sides of the non-flat metal part and the U-shaped groove structure of the ground plane remains unchanged, thereby ensuring that the capacitance of the U-shaped capacitor remains stable. 
     In a possible implementation of the first aspect, the non-flat metal part is disposed upside down on the U-shaped groove structure of the ground plane, and the coaxial cable is placed on a bottom surface of the non-flat metal part. 
     In a possible implementation of the first aspect, two U-shaped sides of the U-shaped structure of the non-flat metal part are disposed upside down and cover outside the U-shaped groove structure of the ground plane. In this possible implementation, the problem of difficulty in mass production due to poor stability of capacitive coupling can be resolved. Multi-plane capacitive coupling can ensure the coupling stability, that is, it can be ensured that the capacitance of the capacitor remains stable. In this way, the adapter device has consistent electrical properties and is suitable for mass production. When the non-flat metal part of the U-shaped structure is clamped on the cavity, and the non-flat metal part of the U-shaped structure shakes left and right, the sum of coupling gaps between the two surfaces of the U-shaped sides of the non-flat metal part and the U-shaped groove structure of the ground plane remains unchanged, thereby ensuring that the capacitance of the capacitor remains stable. 
     In a possible implementation of the first aspect, the ground plane is of a hollow square column structure, and the non-flat metal part is of a hollow square column structure. 
     The non-flat metal part may be disposed in the ground plane. The hollow square column structure of the non-flat metal part is placed in an inner cavity of the hollow square column structure of the cavity. In this possible implementation, the problem of difficulty in mass production due to poor stability of capacitive coupling can be resolved. Multi-plane capacitive coupling can ensure the coupling stability, that is, it can be ensured that the capacitance of the capacitor remains stable. In this way, the adapter device has consistent electrical properties and is suitable for mass production. When the non-flat metal part is clamped in the cavity, and the non-flat metal part shakes up, down, left, and right, a sum of coupling gaps between each surface of the non-flat metal part and each corresponding inner surface of the cavity remains unchanged. In this way, it can be ensured that the capacitance of the capacitor remains stable. 
     In a possible implementation of the first aspect, the ground plane is of a hollow square column structure, and the non-flat metal part is of a U-shaped structure. The non-flat metal part may be disposed in the ground plane, or the ground plane may be placed in the non-flat metal part. 
     In a possible implementation of the first aspect, the ground plane is of a hollow circular column structure, and the non-flat metal part is also of a hollow circular column structure. The non-flat metal part may be placed in the ground plane. In this possible implementation, the problem of difficulty in mass production due to poor stability of capacitive coupling can be resolved. The circular column capacitive coupling can ensure the coupling stability, meaning that the capacitance of the capacitor remains stable. In this way, the adapter device has consistent electrical properties and is suitable for mass production. When the non-flat metal part is clamped in the cavity, and the non-flat metal part shakes up, down, left, and right, an equivalent coupling gap between the non-flat metal part and the inner surface of the cavity remains unchanged. In this way, it can be ensured that the capacitance of the capacitor remains stable. Alternatively, the ground plane may be placed in the non-flat metal part. This is not limited in this application. 
     In a possible implementation of the first aspect, the non-flat metal part and the ground plane may form another curved surface coupling other than the circular column coupling, for example, elliptical cylinder coupling; the ground plane may be of a hollow elliptical cylinder structure; and the non-flat metal part is also of a hollow elliptical cylinder structure. 
     According to a second aspect, a feeder device is provided, including a connector for inputting a radio frequency signal, a feeding line, and the adapter device according to any one of the first aspect and the possible implementations of the first aspect. The connector is electrically connected to the coaxial cable, and the feeding line is connected to the air dielectric microstrip. 
     According to a third aspect, an antenna is provided, including the feeder device according to the second aspect. 
     The antenna in the third aspect may be used on a network device, for example, a base station. 
     According to a fourth aspect, a base station (a network device) is provided, including the adapter device according to any one of the first aspect and the possible implementations of the first aspect, or the feeder device according to the second aspect, or the antenna according to the third aspect. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of adaptation between a coaxial cable and an air dielectric microstrip accommodated in an electroplated cavity; 
         FIG.  2    is a schematic diagram of adaptation between a coaxial cable and an air dielectric microstrip placed on a reflection panel; 
         FIG.  3    is a schematic diagram of an adapter device according to an embodiment of this application; 
         FIG.  4    is a schematic diagram of an adapter device according to another embodiment of this application; 
         FIG.  5    is a schematic diagram of an adapter device according to another embodiment of this application; 
         FIG.  6    is a schematic diagram of an adapter device according to another embodiment of this application; 
         FIG.  7    is a schematic diagram of an adapter device according to another embodiment of this application; 
         FIG.  8    is a schematic diagram of an adapter device according to another embodiment of this application; 
         FIG.  9    is a schematic diagram of an adapter device according to another embodiment of this application; and 
         FIG.  10    is a schematic diagram of an adapter device according to another embodiment of this application. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     The following describes technical solutions of this application with reference to the accompanying drawings. 
     It should be noted that when an element is considered to be “connected” or “electrically connected” to another element, the element may be directly connected to the another element, or there may be an intermediate element. The terms “up”, “down”, “left”, “right”, and similar expressions used in this specification are merely for the purpose of illustration. 
     Adaptation between a coaxial cable and an air dielectric microstrip requires connection between an inner conductor of the coaxial cable and the air dielectric microstrip, that is, connection of a signal plane is implemented, and further requires connection between an outer conductor of the coaxial cable and a cavity (or a reflection panel), that is, connection of a ground plane is implemented. The adapter device in this application is a device for implementing adaptation between a coaxial cable and an air dielectric microstrip, and may be used in a scenario in which a radio frequency signal is transmitted from the coaxial cable to the air dielectric microstrip. The adapter device includes an inner conductor of the coaxial cable, an outer conductor of the coaxial cable, the air dielectric microstrip, and related parts of a ground plane. The adapter device may be a part of a feeder device/feeder system of an antenna, and may be used on a network device, for example, a base station. However, this application is not limited thereto. 
       FIG.  1    is a schematic diagram of adaptation between a coaxial cable and an air dielectric microstrip accommodated in an electroplated cavity. A material of the cavity accommodating the air dielectric microstrip is generally aluminum. To weld an outer conductor of the coaxial cable with the cavity, the cavity needs to be electroplated (for example, tinned) to facilitate welding. As shown in  FIG.  1   , an electroplated cavity  110  accommodates an air dielectric microstrip  120 , a coaxial cable  130  enters the electroplated cavity no through a round hole  112  on the cavity, and an inner conductor  132  of the coaxial cable  130  is directly electrically connected to the air dielectric microstrip (not specifically shown), for example, through welding. An outer conductor  134  of the coaxial cable  130  is electrically connected to the electroplated cavity  110  by welding at the round hole  112 . Electroplating the cavity causes high costs of the antenna. 
       FIG.  2    is a schematic diagram of adaptation between a coaxial cable and an air dielectric microstrip placed on a reflection panel. As shown in  FIG.  2   , an outer conductor  212  of a coaxial cable  210  is welded on a printed circuit board (PCB)  220 . The outer conductor  212  of the coaxial cable  210  is connected to a pad  222  of the PCB  220 , and is connected to the ground of the PCB  220  by using a base material  224  (whose back surface is a ground plane) of the PCB  220 , where the pad  222  of the PCB  220  is electrically connected to the ground plane of the PCB  220  by a plated via. The PCB  220  and a reflection panel  230  form capacitive coupling, to implement grounding of the outer conductor  212  of the coaxial cable  210 . An inner conductor  214  of the coaxial cable  210  is electrically connected to an air dielectric microstrip  240 . The PCB  220  and the reflection panel  230  form capacitive coupling. Since the PCB  220  and the reflection panel  230  may be deformed, a stable gap cannot be ensured between the PCB  220  and the large reflection panel  230 , which makes it difficult for mass production and results in inconsistent electrical properties. 
     Based on the foregoing problem, this application provides an adapter device. The adapter device may be used in adaptation between a coaxial cable and an air dielectric microstrip. 
       FIG.  3    is a schematic diagram of an adapter device  300  according to an embodiment of this application. As shown in  FIG.  3   , the adapter device  300  may include a coaxial cable  310 , an air dielectric microstrip  320 , a ground plane  330 , and a non-flat metal part  340 . An outer conductor  312  of the coaxial cable  310  is electrically connected to the non-flat metal part  340 , the non-flat metal part  340  and the ground plane  330  form non-flat capacitive coupling, and an inner conductor  314  of the coaxial cable  310  is electrically connected to the air dielectric microstrip  320 . 
     In embodiments of this application, non-flat means not in a same plane. The non-flat metal part means that the metal part may have a plurality of portions that are not in a same plane, that is, the metal part has a plurality of surfaces; or the metal part may be curved or arc-shaped. The non-flat capacitor means that each electrode plate of the capacitor may have a plurality of portions that are not in a same plane, that is, each electrode plate has a plurality of surfaces; or each electrode plate of the capacitor may be curved or arc-shaped. For example, the non-flat capacitor may be a U-shaped capacitor (three-plane coupling), a square columnar capacitor (four-plane coupling), a cylindrical capacitor (curved surface coupling), or the like, but is not limited thereto. The non-flat may be a combination of three surfaces, a combination of four surfaces, a curved surface, an arc surface, or the like, but is not limited thereto. 
     In embodiments of this application, capacitive coupling may also be referred to as capacitive coupling, electric field coupling, or electrostatic coupling, which intends to achieve signal transmission through the coupling manner of forming capacitors. 
     In embodiments of this application, the ground plane may be a cavity or a reflection panel. In the following embodiments of this application, there are specific embodiments in which the ground plane is a cavity or the ground plane is a reflection panel. Alternatively, the ground plane may be a ground structure in another form. This is not limited in this application. The cavity or the reflection panel may be made of a metal material, for example, aluminum, or may be made of another material. This is not limited in this application. 
     The ground plane in embodiments of this application may be a non-electroplated device, and therefore the costs can be greatly reduced. In embodiments of this application, the outer conductor of the coaxial cable is electrically connected to the non-flat metal part, the non-flat metal part and the ground plane form non-flat capacitive coupling, and a radio frequency signal may be transmitted to the air dielectric microstrip through capacitive coupling, so that the ground plane (the cavity or the reflection panel) does not need to be electroplated. Certainly, the ground plane in embodiments of this application may be alternatively an electroplated device. This is not limited in this application. 
     In embodiments of this application, the inner conductor of the coaxial cable and the air dielectric microstrip may be electrically connected through welding, or may be electrically connected in another manner, for example, electrically connected by crimping, winding, or screw (cap) fastening. This is not limited in this application. 
     In embodiments of this application, the outer conductor of the coaxial cable and the non-flat metal part may be electrically connected through welding, or may be electrically connected in another manner, for example, electrically connected by crimping, winding, or screw (cap) fastening. This is not limited in this application. 
     In embodiments of this application, the outer conductor of the coaxial cable may be electrically connected along an axial direction of the coaxial cable, for example, welded to the non-flat metal part. The electrical connection may be connection in a point-based manner (for example, welding at a point), may be connection in a line-based manner (for example, welding along a line), or may be connection in a plane-based manner (for example, welding in a wide area). To facilitate connection and assembly, a connection portion may be disposed on the non-flat metal part, so that the outer conductor of the coaxial cable can be more conveniently welded to the connection portion, to implement the electrical connection between the outer conductor of the coaxial cable and the non-flat metal part. The connection portion may also be disposed for connection in a point-based manner or in a line-based or plane-based manner. This is not limited in this application. 
     In embodiments of this application, adhesive may be filled between the non-flat metal part and the ground plane for fixing and insulating. Certainly, another material may be alternatively used for filling, for fixing and/or insulating. This is not limited in this application. 
     According to the adapter device provided in this application, the inner conductor of the coaxial cable is electrically connected to the air dielectric microstrip, the outer conductor of the coaxial cable is electrically connected to the non-flat metal part, and the non-flat metal part and the ground plane form non-flat capacitive coupling, so that the outer conductor of the coaxial cable is grounded. The non-flat capacitive coupling manner can realize stable coupling connection, thereby achieving consistent electrical properties, and making it suitable for mass production. 
     The non-flat capacitor structure has coupling in several planes (multi-plane coupling) or curved surface/arc surface coupling. When the non-flat capacitor structure shakes, some parts of capacitance formed between surfaces or curved surfaces of the non-flat capacitor increase, and some parts decrease. However, a total capacitance remains unchanged or changes slightly, which facilitates stability and ensures consistent electrical properties. The stability ensures that the requirements for processing and assembly are naturally reduced, which facilitates mass production. 
     The position at which the outer conductor of the coaxial cable is electrically connected to the non-flat metal part is not limited in embodiments of this application. 
     In some embodiments of this application, a first connection point at which the outer conductor of the coaxial cable is electrically connected to the non-flat metal part may be located at a middle portion of the non-flat capacitor in a length direction. It should be understood that the middle portion is a point or a segment within a distance in the middle of the non-flat capacitor in the length direction. This is not limited in this application. In a specific example, a connection portion may be disposed at the first connection point on the non-flat metal part. 
     In some other embodiments of this application, the first connection point at which the outer conductor of the coaxial cable is electrically connected to the non-flat metal part may be located at one of two ends of the non-flat capacitor in the length direction. In a specific example, a connection portion may be disposed at the first connection point on the non-flat metal part. 
     Alternatively, the first connection point may be disposed at another position. This is not limited in this application. 
       FIG.  4    is a schematic diagram of an adapter device  400  according to another embodiment of this application, where the adapter device is provided with a connection portion at a first connection point. As shown in  FIG.  4   , the adapter device  400  may include a coaxial cable  410 , an air dielectric microstrip  420 , a ground plane  430  (which is a cavity in  FIG.  4   ), and a non-flat metal part  440 . An inner conductor  414  of the coaxial cable  410  is electrically connected to the air dielectric microstrip  420 . An outer conductor  412  of the coaxial cable  410  is electrically connected to the non-flat metal part  440 , and the non-flat metal part  440  and the ground plane  430  form non-flat capacitive coupling. A first connection point at which the outer conductor  412  of the coaxial cable  410  is electrically connected to the non-flat metal part  440  may be located at one of two ends of a non-flat capacitor in the length direction. A connection portion  442  is disposed at the first connection point between the outer conductor  412  of the coaxial cable  410  and the non-flat metal part  440  shown in  FIG.  4   . 
     The first connection point (the connection portion  442 ) between the outer conductor  412  of the coaxial cable  410  in the adapter device  400  shown in  FIG.  4    and the non-flat metal part  440  is at an end close to a second connection point between the inner conductor  414  of the coaxial cable  410  and the air dielectric microstrip  420 , that is, a right end of the non-flat capacitor in the length direction. In another embodiment, the first connection point may be located at the other end of the non-flat capacitor in the length direction, that is, a left end of the non-flat capacitor in the length direction, which is the end away from the connection point between the inner conductor  414  of the coaxial cable  410  and the air dielectric microstrip  420 . The first connection point is disposed at one of the two ends of the non-flat capacitor in the length direction. Certainly, in another embodiment of this application, the first connection point may not be limited to being disposed at one of the two ends of the non-flat capacitor in the length direction, and the first connection point may be located at a middle portion of the non-flat capacitor in the length direction. This is not limited in this application. 
     The connection portion may be specifically a metal sheet with a hole at an end of the non-flat metal part. The outer conductor of the coaxial cable may be electrically connected to the metal sheet, for example, connected through welding. The inner conductor of the coaxial cable may be electrically connected to the air dielectric microstrip through the hole on the metal sheet. Alternatively, the connection portion may be another component having a clamping/clipping function. This is not limited in this application. In another embodiment of this application, no connection portion may alternatively be disposed at the first connection point, and the outer conductor of the coaxial cable is directly connected to the non-flat metal part. This is not limited in this application. 
     In some embodiments of this application, the first connection point may be disposed at a position that is on the coaxial cable and is close to a second connection point at which the inner conductor of the coaxial cable is electrically connected to the air dielectric microstrip. In other words, positions of the first connection point and the second connection point may be set as close as possible. It should be understood that as close as possible in this application means that when a processing and/or assembly condition permits, the positions of the first connection point and the second connection point are set as close as possible. For example, a distance between the first connection point and the second connection point may be less than or equal to 5 mm. Alternatively, for example, the distance between the first connection point and the second connection point may be less than or equal to 1/10 of the length of the non-flat metal part. This is not limited in this application. At a signal plane (which is a plane formed by the electrical connection between the inner conductor of the coaxial cable and the air dielectric microstrip), current is formed between the first connection point and the second connection point; and at the ground plane (which is a plane to which the outer conductor of the coaxial cable is connected), current in an opposite direction is formed between the first connection point and the second connection point. As a result, a current loop is formed between the first connection point and the second connection point. The positions of the first connection point and the second connection point are set as close as possible, so that performance of the feeder device can be improved, and performance of the antenna can be accordingly improved. 
     In embodiments of this application, to adapt to a specific antenna structure, shapes, sizes, positions, and the like of components in the adapter device may have a plurality of forms, allowing the adapter device to be more flexibly used in the antenna structure.  FIG.  5    to  FIG.  10    are some specific examples of different forms, but the structure of the adapter device in this application is not limited to the structures in these figures. 
     In some embodiments of this application, the non-flat capacitive coupling formed by the non-flat metal part and the ground plane may be non-flat multi-plane capacitive coupling. The multi-plane coupling refers to the formation of coupling in a plurality of planes, and may be, for example, three-plane coupling or four-plane coupling. However, this application is not limited thereto. 
     In some specific embodiments of this application, the ground plane has a U-shaped groove structure, and the non-flat metal part is of a U-shaped structure. The non-flat metal part and the ground plane form U-shaped capacitive coupling, and the non-flat metal part of the U-shaped structure is sleeved outside the coaxial cable. In other words, the non-flat metal part of the U-shaped structure is embedded into the U-shaped groove structure of the ground plane to form a U-shaped capacitor (form a capacitor with three-plane coupling), and the non-flat metal part of the U-shaped structure is sleeved outside the coaxial cable. The adapter devices shown in  FIG.  3    and  FIG.  4    are both of the foregoing structure. The ground plane may be a cavity having a U-shaped groove structure shown in  FIG.  4   , or may be a reflection panel having a U-shaped groove structure. 
       FIG.  5    is a schematic diagram of an adapter device  500  according to another embodiment of this application.  FIG.  5    shows an example of forming U-shaped capacitive coupling by a non-flat metal part and a ground plane in the adapter device. As shown in  FIG.  5   , the adapter device  500  may include a coaxial cable  510 , an air dielectric microstrip  520 , a ground plane  530  (where the ground plane in  FIG.  5    is a reflection panel, and the reflection panel forms a U-shaped groove structure through bending), and a non-flat metal pall  540 . An inner conductor  514  of the coaxial cable  510  is electrically connected to the air dielectric microstrip  520 . An outer conductor  512  of the coaxial cable  510  is electrically connected to the non-flat metal part  540 , and the non-flat metal part  540  and the ground plane  530  form non-flat capacitive coupling having three-plane coupling. 
     When a material tolerance or an assembly tolerance is large, for example, when the non-flat metal part of the U-shaped structure clamped in the U-shaped groove structure of the ground plane shakes left and right, the U-shaped capacitive coupling structure can ensure that a sum of coupling gaps between two surfaces of the U-shaped sides of the non-flat metal part and the U-shaped groove structure of the ground plane remains unchanged or changes slightly, which can ensure that the capacitance of the U-shaped capacitor remains stable, thereby ensure the stability of capacitive coupling. In this way, the adapter device has consistent electrical properties and is suitable for mass production. 
     In addition, a first connection point at which the outer conductor  512  of the coaxial cable  510  is electrically connected to the non-flat metal part  540  may be located at a right end of the non-flat capacitor in a length direction, or may be located at a left end or a middle portion of the non-flat capacitor in the length direction. This is not limited in this application. 
     In some specific embodiments of this application, the ground plane has a U-shaped groove structure, and the non-flat metal part is of a U-shaped structure. The non-flat metal part is disposed upside down on the U-shaped groove structure of the ground plane, and the coaxial cable is placed on a bottom surface of the non-flat metal part. 
       FIG.  6    is a schematic diagram of an adapter device  600  according to another embodiment of this application. Different from  FIG.  5   ,  FIG.  6    shows an example in which both a non-flat metal part and a ground plane in the adapter device are of a U-shaped structure and disposed upside down on each other to form capacitive coupling. Embodiments of this application may be flexibly applied to various different antenna structures. In  FIG.  6   , a coaxial cable and an air dielectric microstrip are located on a same side of a second connection point (which is a connection point between an inner conductor of the coaxial cable and the air dielectric microstrip). For example, both the coaxial cable and the air dielectric microstrip shown in  FIG.  6    are located on a left side of the second connection point. As shown in  FIG.  6   , the adapter device  600  may include a coaxial cable  610 , an air dielectric microstrip  620 , a ground plane  630  (which is a cavity in  FIG.  6   ), and a non-flat metal part  640 . An inner conductor  614  of the coaxial cable  610  is electrically connected to the air dielectric microstrip  620 . An outer conductor  612  of the coaxial cable  610  is electrically connected to the non-flat metal part  640 , and the non-flat metal part  640  and the ground plane  630  form non-flat capacitive coupling. As shown in  FIG.  6   , the ground plane  630  has a U-shaped groove structure, and the non-flat metal part  640  is of a U-shaped structure. The non-flat metal part  640  is disposed upside down on the U-shaped groove structure of the ground plane  630 , and the coaxial cable  610  is placed on a bottom surface of the non-flat metal part  640 . 
     Specifically, the outer conductor  612  of the coaxial cable  610  and the non-flat metal part  640  of the U-shaped structure may be welded to each other at an end close to the second connection point between the inner conductor  614  of the coaxial cable  610  and the air dielectric microstrip  620 . The non-flat metal part  640  of the U-shaped structure is placed across a narrow edge of the cavity to form a capacitor with three-plane coupling. The coaxial cable  610  is placed on the bottom surface (not the two surfaces of the U-shaped sides) of the non-flat metal part  640  of the U-shaped structure. The inner conductor  614  of the coaxial cable  610  is welded to the air dielectric microstrip  620 , where a connecting component may be disposed for ease of welding. In the adapter device shown in  FIG.  6   , the two U-shaped sides of the U-shaped structure of the non-flat metal part  640  are disposed upside down and cover outside the U-shaped groove structure of the ground plane  630  (the cavity). 
     When the non-flat metal part  640  of the U-shaped structure is clamped on the cavity, and the non-flat metal part  640  of the U-shaped structure shakes left and right, the sum of coupling gaps between the two surfaces of the U-shaped sides of the non-flat metal part and the U-shaped groove structure of the ground plane remains unchanged or changes slightly, which can ensure that the capacitance of the U-shaped capacitor remains stable, thereby ensure the stability of capacitive coupling. In this way, the adapter device has consistent electrical properties and is suitable for mass production. 
     In addition, a first connection point at which the outer conductor  612  of the coaxial cable  610  is electrically connected to the non-flat metal part  640  may be located at a right end of the non-flat capacitor in a length direction, or may be located at a left end or a middle portion of the non-flat capacitor in the length direction. This is not limited in this application. 
       FIG.  7    is a schematic diagram of an adapter device  700  according to another embodiment of this application. Different from  FIG.  6   ,  FIG.  7    also shows an example in which both a non-flat metal part and a ground plane in the adapter device are of a U-shaped structure and disposed upside down on each other to form capacitive coupling. However, a coaxial cable and an air dielectric microstrip are located on different sides of a second connection point. For example, the coaxial cable shown in  FIG.  7    is located on a left side of the second connection point, and the air dielectric microstrip is located on a right side of the second connection point. As shown in  FIG.  7   , the adapter device  700  may include a coaxial cable  710 , an air dielectric microstrip  720 , a ground plane  730  (where the ground plane in  FIG.  7    is a reflection panel, and the reflection panel forms a U-shaped groove structure through bending), and a non-flat metal part  740 . An inner conductor  714  of the coaxial cable  710  is electrically connected to the air dielectric microstrip  720 . An outer conductor  712  of the coaxial cable  710  is electrically connected to the non-flat metal part  740 , and the non-flat metal part  740  and the ground plane  730  form non-flat capacitive coupling. The two U-shaped sides of the U-shaped structure of the non-flat metal part  740  are disposed upside down and cover outside the U-shaped groove structure of the ground plane  730  (the reflection panel). When the non-flat metal part  740  of the U-shaped structure is clamped outside the U-shaped groove structure of the reflection panel, and the non-flat metal part  740  of the U-shaped structure shakes left and right, the sum of coupling gaps between the two surfaces of the U-shaped sides of the non-flat metal part and the U-shaped groove structure of the reflection panel remains unchanged or changes slightly, which can ensure that the capacitance of the U-shaped capacitor remains stable, thereby ensure the stability of capacitive coupling. In this way, the adapter device has consistent electrical properties and is suitable for mass production. 
     In another embodiment of this application, one U-shaped side of the U-shaped structure of the non-flat metal part may be disposed upside down in the U-shaped groove structure of the ground plane. Alternatively, the two U-shaped sides of the U-shaped structure of the non-flat metal part may both be disposed upside down in the U-shaped groove structure of the ground plane. This is not limited in this application. 
     In addition, a first connection point at which the outer conductor  712  of the coaxial cable  710  is electrically connected to the non-flat metal part  740  may be located at a right end of the non-flat capacitor in a length direction, or may be located at a left end or a middle portion of the non-flat capacitor in the length direction. This is not limited in this application. 
     In some specific embodiments of this application, the ground plane is of a hollow square column structure, and the non-flat metal part is of a hollow square column structure. The non-flat metal part is placed in the ground plane, that is, the hollow square column structure of the non-flat metal part is placed in the ground plane (the cavity) of the hollow square column structure. 
       FIG.  8    is a schematic diagram of an adapter device  800  according to another embodiment of this application.  FIG.  8    shows an example in which a ground plane is of a hollow square column structure, a non-flat metal part is of a hollow square column structure, and both are sleeved to form capacitive coupling, where the ground plane of the hollow square column structure surrounds the hollow square column structure of the non-flat metal part. As shown in  FIG.  8   , the adapter device  800  may include a coaxial cable  810 , an air dielectric microstrip  820 , a ground plane  830  (which is a cavity in  FIG.  8   ), and a non-flat metal part  840 . An inner conductor  814  of the coaxial cable  810  is electrically connected to the air dielectric microstrip  820 . An outer conductor  812  of the coaxial cable  810  is electrically connected to the non-flat metal part  840 , and the non-flat metal part  840  and the ground plane  830  form non-flat capacitive coupling. The hollow square column structure of the non-flat metal part  840  is placed in an inner cavity of the hollow square column structure of the cavity. When the non-flat metal part  840  is clamped in the cavity, and the non-flat metal part  840  shakes up, down, left, and right, a sum of coupling gaps between each surface of the non-flat metal part and each corresponding inner surface of the cavity remains unchanged or changes slightly, which can ensure that the capacitance of the capacitor remains stable, thereby ensure the stability of capacitive coupling. In this way, the adapter device has consistent electrical properties and is suitable for mass production. 
     In addition, a first connection point at which the outer conductor  812  of the coaxial cable  810  is electrically connected to the non-flat metal part  840  may be located at a right end of the non-flat capacitor in a length direction, or may be located at a left end or a middle portion of the non-flat capacitor in the length direction. This is not limited in this application. 
     In some specific embodiments of this application, the ground plane is of a hollow square column structure, and the non-flat metal part is of a hollow square column structure; or the ground plane is of a hollow square column structure, and the non-flat metal part is of a U-shaped structure. The ground plane is placed in the non-flat metal part, that is, the hollow square column structure or the U-shaped structure of the non-flat metal part surrounds the ground plane (the cavity) of the hollow square column structure. 
       FIG.  9    is a schematic diagram of an adapter device  900  according to another embodiment of this application. Different from  FIG.  8   ,  FIG.  9    shows an example in which the ground plane is of a hollow square column structure, the non-flat metal part is of a hollow square column structure or a U-shaped structure, and both are sleeved to form capacitive coupling. However, the hollow square column structure of the non-flat metal part surrounds the ground plane of the hollow square column structure. As shown in  FIG.  9   , the adapter device  900  may include a coaxial cable  910 , an air dielectric microstrip  920 , a ground plane  930  (which is a cavity in  FIG.  9   ), and a non-flat metal part  940 . An inner conductor  914  of the coaxial cable  910  is electrically connected to the air dielectric microstrip  920 . An outer conductor  912  of the coaxial cable  910  is electrically connected to the non-flat metal part  940 , and the non-flat metal part  940  and the ground plane  930  form non-flat capacitive coupling. The hollow square column structure of the non-flat metal part  940  surrounds the hollow square column structure of the cavity. When the non-flat metal part  940  surrounds the cavity, and the non-flat metal part  940  shakes left and right, a sum of coupling gaps between each surface of the non-flat metal part and each corresponding outer surface of the cavity remains unchanged, which can ensure that the capacitance of the capacitor remains stable, thereby ensure the stability of capacitive coupling. In this way, the adapter device has consistent electrical properties and is suitable for mass production. 
     In this embodiment, the hollow square column structure of the non-flat metal part  940  may be a closed square column, or may be a non-closed square column (for example, the non-flat metal part  940  shown in  FIG.  9    does not have an upper surface). Non-closed square columns are easier to process and assemble. When the non-flat metal part  940  shown in  FIG.  9    does not have an upper surface, the U-shaped structure of the non-flat metal part may surround the cavity of the hollow square column structure. 
     In addition, a first connection point at which the outer conductor  912  of the coaxial cable  910  is electrically connected to the non-flat metal part  940  may be located at a left end of the non-flat capacitor in a length direction, or may be located at a right end or a middle portion of the non-flat capacitor in the length direction. This is not limited in this application. 
     In some embodiments of this application, the non-flat metal part may be alternatively another multi-plane cylinder, for example, a triangular prism, a pentagonal prism, a hexagonal prism, or another cylinder. A corresponding groove, protrusion, or the like that matches the shape of the non-flat metal part may be disposed on the ground plane, so that the non-flat metal part and the ground plane form non-flat multi-plane capacitive coupling. This is not limited in this application. 
     In some embodiments of this application, the non-flat capacitive coupling formed by the non-flat metal part and the ground plane may be arc-shaped or curved capacitive coupling, for example, elliptical cylinder coupling. The ground plane may be of a hollow elliptical cylinder structure, and the non-flat metal part is also of a hollow elliptical cylinder structure. 
     In some specific embodiments of this application, the ground plane is of a hollow circular column structure, and the non-flat metal part is also of a hollow circular column structure. The non-flat metal part is placed in the ground plane, that is, the hollow circular column structure of the non-flat metal part is placed in the ground plane (the cavity) of the hollow circular column structure. 
       FIG.  10    is a schematic diagram of an adapter device  1000  according to another embodiment of this application. Different from the square column structure or the U-shaped structure in the embodiments corresponding to the foregoing accompanying drawings,  FIG.  10    shows an example in which the ground plane is of a hollow circular column structure, the non-flat metal part is of a hollow circular column structure, and both are sleeved to form capacitive coupling. As shown in  FIG.  10   , the adapter device  1000  may include a coaxial cable  1010 , an air dielectric microstrip  1020 , a ground plane  1030  (which is a cavity in  FIG.  10   ), and a non-flat metal part  1040 . An inner conductor  1014  of the coaxial cable  1010  is electrically connected to the air dielectric microstrip  1020 . An outer conductor  1012  of the coaxial cable  1010  is electrically connected to the non-flat metal part  1040 , and the non-flat metal part  1040  and the ground plane  1030  form non-flat capacitive coupling. The hollow circular column structure of the non-flat metal part  1040  is placed in an inner cavity of the hollow circular column structure of the cavity. When the non-flat metal part  1040  is clamped in the cavity, and the non-flat metal part  1040  shakes up, down, left, and right, an equivalent coupling gap between the non-flat metal part  1040  and the inner surface of the cavity remains unchanged or changes slightly, which can ensure that the capacitance of the capacitor remains stable, thereby ensure the stability of capacitive coupling. In this way, the adapter device has consistent electrical properties and is suitable for mass production. 
     In this embodiment, the hollow circular column structure of the non-flat metal part  1040  may be a closed circular column, or a non-closed circular column with a slit shown in  FIG.  10   . Non-closed circular columns are easier to process and assemble. 
     In addition, a first connection point at which the outer conductor  1012  of the coaxial cable  1010  is electrically connected to the non-flat metal part  1040  may be located at a right end of the non-flat capacitor in a length direction, or may be located at a left end or a middle portion of the non-flat capacitor in the length direction. This is not limited in this application. 
     In some other specific embodiments of this application, the ground plane is of a hollow circular column structure, and the non-flat metal part is also of a hollow circular column structure. The ground plane is placed in the non-flat metal part, that is, the hollow circular column structure of the non-flat metal part surrounds the ground plane (the cavity) of the hollow circular column structure, which is not shown in the drawings again. 
     This application further provides a feeder device, including a connector for inputting a radio frequency signal, a feeding line, and the adapter device described above, where the connector is electrically connected to the coaxial cable, and the feeding line is connected to the air dielectric microstrip. 
     This application further provides an antenna, including the feeder device described above. 
     The antenna may be used on a network device, for example, a base station. 
     This application further provides a base station (a network device), including the adapter device in this application, or the feeder device in this application, or the antenna in this application. 
     It should be understood that various numbers in this specification are merely used for differentiation for ease of description, and are not used to limit the scope of this application. 
     The technical features of the foregoing embodiments may be combined randomly. For brevity of description, not all possible combinations of the technical features in the foregoing embodiments are described. However, as long as no conflict exists between the combinations of the technical features, it should be considered that the technical features fall within the scope of the disclosure of this specification. 
     The foregoing descriptions are merely specific implementations of this application, but are not intended to limit the protection scope of this application. Any variation or replacement readily figured out by a person skilled in the art within the technical scope disclosed in this application shall fall within the protection scope of this application. Therefore, the protection scope of this application shall be subject to the protection scope of the claims.