Mutual coupling suppression structure between antenna units of array antenna based on printed circuit board

Abstract

The present application discloses a mutual coupling suppression structure between antenna units of an array antenna based on a printed circuit board. A plurality of antenna units for constituting an array antenna are made in a multilayer printed circuit board, and a rectangular metal frame is provided around each antenna unit for separation; a groove extending downward from the top of the multilayer printed circuit board is provided at the position of the common vertex or common edge of two or four adjacent metal frames, and a metal through hole is provided at the bottom of each groove, and the metal through hole penetrates the multilayer printed circuit board from the bottom of each groove; two or four grooves of the common vertex or common edge of two or four adjacent metal frames are spliced ​​into a closed shape. The present application controls the coupling amplitude and phase between antenna units by introducing a groove and a metal through hole at the bottom between antenna units, and cancels the coupling between the existing antenna units, thereby achieving the effect of mutual coupling suppression, eliminating the scanning blind spot of the array antenna and increasing its working bandwidth.

Description

Technical Field

[0001] The present application relates to a structure for suppressing mutual coupling between antenna units of an array antenna. Background Art

[0002] An array antenna is a special antenna composed of multiple antenna units arranged according to specific rules. With its excellent beam aggregation and beam agility capabilities, array antennas are widely used in wireless transceiver equipment such as radar, satellite communications, and communication base stations. They are crucial to improving the range of wireless systems and realizing advanced functions.

[0003] In modern wireless devices, array antennas based on printed circuit boards have been widely used due to their mature technology, high integration, and controllable costs. In the design of array antennas based on printed circuit boards, since multiple antenna units are closely arranged, they will have mutual influence when sending and receiving electromagnetic signals, that is, mutual coupling. The existence of mutual coupling causes array antennas to have problems such as reduced working bandwidth, beam deformation, cross-polarization elevation, increased side lobes, and scanning blind spots. Therefore, mutual coupling reduction has always been a major problem in the theoretical research and engineering application of array antennas.

[0004] See also Figure 1 This is a cross-sectional schematic diagram of an array antenna based on a printed circuit board. A multilayer printed circuit board 10 is composed of, from bottom to top: a first floor layer 11, a feeder substrate layer 12, a second floor layer 13, and an antenna substrate layer 14. The first floor layer 11 and the second floor layer 13 are made of metal materials, indicated by light blue filling. The feeder substrate layer 12 and the antenna substrate layer 14 are made of dielectric materials, indicated by oblique lines filling. Various antenna units are made in the antenna substrate layer 14, the second floor layer 13, and the feeder substrate layer 12 of the multilayer printed circuit board 10, Figure 1 Two antenna units 100a and 100b are schematically shown in FIG. 1 , which are indicated by black filling. A dielectric board is located above the multilayer printed circuit board 10 and serves as an antenna cover (radome) 20 of the array antenna.

[0005] Figure 1The coupling path between the antenna units 100a and 100b in the array includes: the guided wave coupling introduced by the feeder substrate layer 12, the first floor layer 11 and the second floor layer 13, the surface wave coupling introduced by the antenna substrate layer 14, the spatial coupling existing in the near-field space, and the reflective coupling introduced by the antenna cover 20. The total coupling between the antenna units 100a and 100b is composed of the superposition of the above four couplings. Since the amplitudes and phases of the four couplings are different, the superposition may cause great mutual coupling due to the in-phase superposition, or may achieve the effect of mutual coupling suppression due to coupling decomposition. In actual design, each structure in the array antenna based on the printed circuit board has its original function and cannot be sacrificed for mutual coupling suppression, which limits the freedom of mutual coupling suppression design.

[0006] There are mainly the following types of mutual coupling suppression technologies between antenna units of existing array antennas.

[0007] The first is to densely add metal through holes around the antenna elements and feed lines of the array antenna to form an isolation barrier to suppress potential coupling. In this document, metal through holes refer to hole-like structures filled with metal materials, not simple holes, and do not necessarily penetrate the structure of the holes. This needs special attention. Please refer to Figure 2 , a plurality of antenna units 100 (white filled parts) for forming an array antenna are made in a multilayer printed circuit board 10 (dark gray filled parts). When the antenna units are arrayed, a rectangular metal frame 150 (light gray filled parts) is set around each antenna unit 100 to separate them. The widths of different sides of the metal frame 150 can be the same or different. The distance L between two adjacent antenna units 100 is the smaller of L1 and L2. In each metal frame 150, a rectangular isolation fence 160 is formed by a plurality of metal through holes, which basically surrounds each antenna unit 100. The isolation fence 160 may be missing in a local position. This method is the most commonly used, but its mutual coupling suppression ability is limited and its effect on spatial coupling is weak. In addition, it introduces a large number of pore structures, which brings great pressure to simulation design, simulation verification, and processing technology.

[0008] The second method is to design a decoupling network between the antenna elements of the array antenna to suppress the mutual coupling between the antenna ports from the circuit perspective. This method is mature in theory, but it introduces a complex feeding structure in actual engineering, occupies the space of the array antenna and introduces additional feeder losses.

[0009] The third method is to add frequency selective surfaces, electromagnetic band gap structures, isolation plates and other mutual coupling isolation structures between the antenna units of the array antenna. This type of method has received extensive academic attention, but it requires additional space for the array antenna and requires a fixing device, and it is easy to affect the radiation performance design of the antenna units of the original array antenna.

[0010] The fourth method is to introduce coupling cancellation structures between antenna elements of the array antenna, such as neutralization lines, coupling lines, coupling bypasses, etc. The idea of ​​this method is ingenious, but its design freedom is limited by the actual structure.

[0011] See also Figure 3 , which is adopted Figure 2 The schematic diagram of the passive port reflection coefficient of the array antenna with mutual coupling suppression technology shown in the figure is when the antenna unit works alone (i.e. not forming an array). Each antenna unit itself is a broadband antenna with no reflection anomalies in its in-band reflection. However, when multiple antenna units are used in an array, abnormal points of active reflection coefficient are generated due to mutual coupling (such as Fig.18 The scanning blind area is generated. Summary of the invention

[0012] The technical problem to be solved by the present application is: for an array antenna based on a printed circuit board, how to achieve the effect of mutual coupling suppression and enhance the oblique scanning capability of the array antenna without occupying additional space or introducing additional processes.

[0013] In order to solve the above technical problems, the present application proposes a mutual coupling suppression structure between antenna units of an array antenna based on a printed circuit board. A plurality of antenna units for constituting an array antenna are made in a multilayer printed circuit board, and a rectangular metal frame is provided around each antenna unit for separation; a groove extending downward from the top of the multilayer printed circuit board is respectively provided at the position of a common vertex or a common edge of two or four adjacent metal frames, and a metal through hole is provided at the bottom of each groove, and the metal through hole passes through the multilayer printed circuit board from the bottom of each groove; two or four grooves at the common vertex or common edge of two or four adjacent metal frames are spliced ​​into a closed shape.

[0014] Furthermore, if there are only two adjacent metal frames that share a vertex, a groove extending downward from the top of the multilayer printed circuit board is respectively set at the two vertex corners of the common vertex of the two adjacent metal frames, and the top view shape of a single groove is a quarter of a waist circle, and the two grooves of the common vertex of the two adjacent metal frames are combined into a half waist circle. If there are four adjacent metal frames that share a vertex, a groove extending downward from the top of the multilayer printed circuit board is respectively set at the four vertex corners of the common vertex of the four adjacent metal frames, and the top view shape of a single groove is a quarter of a waist circle, and the four grooves of the common vertex of the four adjacent metal frames are combined into a complete waist circle. Alternatively, the top view shape of a single groove is changed to any one of the following: an isosceles right triangle, a half rounded rectangle, a non-isosceles right triangle, a quarter of an ellipse, or a quarter of a circle.

[0015] Furthermore, the edges of all metal frames have only two directions, either parallel to the X-axis direction or parallel to the Y-axis direction; if two adjacent metal frames share an edge in a certain direction, a groove extending downward from the top of the multilayer printed circuit board is respectively provided on both sides of the shared edge of the two adjacent metal frames, and the top view shape of a single groove is half of an ellipse, and the two grooves of the shared edge of the two adjacent metal frames are combined into a complete ellipse. Alternatively, the top view shape of a single groove is changed to any one of the following: an isosceles triangle, half a rectangle, half a waisted circle, a non-isosceles triangle, half a rounded rectangle, or half a circle.

[0016] Optionally, grooves are provided on both sides of the common edge parallel to the X-axis direction, and grooves are provided on both sides of the common edge parallel to the Y-axis direction; the grooves provided on the common edges in the two directions are independent of each other.

[0017] Further, the groove is only within the range of the metal frame when viewed from a top view; or, the groove is within the range of both the metal frame and the multilayer printed circuit board when viewed from a top view, but cannot fall within the range of the antenna unit.

[0018] Furthermore, the strength and phase of the initial coupling between the antenna units are controlled by adjusting the position of the groove relative to the antenna unit, and the strength and phase of the initial coupling between the antenna units are fine-tuned by adjusting the top view shape of the groove.

[0019] Furthermore, the multilayer printed circuit board includes an antenna substrate layer located at the top and a feeder substrate layer located at the bottom, the antenna substrate layer has one or more layers, and the feeder substrate layer has one or more layers; a floor layer is provided at one or more locations between the antenna substrate layer and the feeder substrate layer, above the top antenna substrate layer, below the bottom feeder substrate layer, between multiple antenna substrate layers, and between multiple feeder substrate layers; and each antenna unit used to constitute the array antenna is made in the antenna substrate layer and the feeder substrate layer of the multilayer printed circuit board.

[0020] Preferably, the length and width of a single groove do not exceed one third of the antenna unit spacing, and the depth of the groove does not exceed two thirds of the total thickness of the multilayer printed circuit board.

[0021] Furthermore, the cross-sectional shape of a single groove is any one of the following: rectangular, stepped, ∩-shaped, inverted trapezoidal, and regular trapezoidal.

[0022] Furthermore, the bottom of the groove is either in the antenna substrate layer or in the feeder substrate layer; when the bottom of the groove is in the antenna substrate layer, the cross-sectional shape of the groove affects the surface wave coupling between the antenna units; when the bottom of the groove reaches the feeder substrate layer, the cross-sectional shape of the groove affects both the surface wave coupling and the waveguide coupling between the antenna units.

[0023] Furthermore, the relative position of the metal through hole and the groove is any one of the following: the metal through hole is at the center of the bottom of the groove, the metal through hole is at a position deviated from the center of the bottom of the groove, the metal through hole is at the edge of the bottom of the groove, and if there is a protruding structure inside the groove, the position of the metal through hole is independent of the position of the protruding structure; the relative position of the metal through hole and the groove affects the waveguide coupling between the antenna units.

[0024] Furthermore, the bottom surface and / or side wall of the groove are not coated with metal coating, or the groove is coated with metal coating only on the side wall, or the groove is coated with metal coating only on the bottom surface, or the groove is coated with metal coating on both the side wall and the bottom surface; the presence or absence of metal coating on the side wall of the groove affects the surface wave coupling between the antenna units; the presence or absence of metal coating on the bottom surface of the groove affects the guided wave coupling between the antenna units.

[0025] Furthermore, when designing the mutual coupling suppression structure, a groove is first set, and the position, shape, size, side wall and bottom of the groove are adjusted, and whether a metal plating process is selected to suppress the guided wave coupling and surface wave coupling between the antenna units; then a metal through hole is set at the bottom of the groove, and a controllable new coupling path is formed by adjusting the number of metal through holes, their relative position and size with the groove, so as to offset the surface wave coupling, guided wave coupling and spatial coupling between the antenna units.

[0026] The technical effect achieved by this application is: by introducing grooves between antenna units and metal through holes at their bottoms to control the coupling amplitude and phase between antenna units, and cancel the coupling between the existing antenna units, so as to achieve the effect of mutual coupling suppression, eliminate the scanning blind spots of the array antenna and increase its working bandwidth. This method is very compatible with array antennas manufactured based on printed circuit boards, does not require additional space or additional processes, and adds new design freedom to the mutual coupling suppression design between antenna units at a very low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the coupling paths between antenna units of an array antenna based on a printed circuit board.

[0028] Figure 2 The present invention is a schematic diagram of a mutual coupling suppression technology between antenna units of an existing array antenna.

[0029] Figure 3 Is adopted Figure 2 A schematic diagram of the port reflection coefficient of the array antenna using the mutual coupling suppression technology when the antenna units work alone.

[0030] Figure 4-Figure 6 It is a top view schematic diagram of the first embodiment of the mutual coupling suppression structure between antenna units of the array antenna based on the printed circuit board proposed in the present application.

[0031] Figure 7-10 It is a top view schematic diagram of the second embodiment of the mutual coupling suppression structure between antenna units of the array antenna based on the printed circuit board proposed in the present application.

[0032] Fig.11 It is a partial cross-sectional schematic diagram of a mutual coupling suppression structure between antenna units of an array antenna based on a printed circuit board proposed in the present application.

[0033] Figure 12-Figure 17 It is a cross-sectional schematic diagram of different types of grooves and metal through holes at their bottoms proposed in this application.

[0034] Fig.18 It is a comparative schematic diagram of the active reflection coefficients of the antenna units before and after the mutual coupling suppression structure of the present application is adopted during oblique scanning.

[0035] Fig.19 It is a comparative schematic diagram of the antenna unit radiation patterns in the array during oblique scanning before and after the mutual coupling suppression structure of the present application is adopted.

[0036] Explanation of the reference numerals in the figure: 10 is a multi-layer printed circuit board, 11 and 13 are floor layers, 12 is a feeder substrate layer, 14 is an antenna substrate layer, 20 is an antenna cover, 100, 100a and 100b are antenna units, 150 is a metal frame, 160 is an isolation fence, 30 is a multi-layer printed circuit board, 31, 33, 35, 37, 39 are floor layers, 32 and 34 are feeder substrate layers, 36 and 38 are antenna substrate layers, 40 is a semi-cured sheet layer, 41, 42, 43 are metal through holes extending from the top of the multi-layer printed circuit board to the bottom, 5 is a metal through hole extending from the bottom of the groove to the bottom, 6 is a groove, and 7 is a metal plating. DETAILED DESCRIPTION

[0037] See also Figure 4, the first embodiment of the mutual coupling suppression structure between antenna units of the array antenna based on the printed circuit board proposed in the present application is that a plurality of antenna units 100 (white filled part) for constituting the array antenna are made in the multi-layer printed circuit board 30 (dark gray filled part). When the antenna units are arrayed, a rectangular metal frame 150 (light gray filled part) is provided around each antenna unit 100 for separation. The rectangular metal frame 150 has four sides and four vertices, and the widths of different sides can be the same or different. If there are only two adjacent metal frames 150 that share a vertex, then a groove 6 extending downward from the top of the multi-layer printed circuit board 30 is respectively provided at the two vertex corners of the common vertex of the two adjacent metal frames 150, and the top view shape of a single groove 6 is a quarter of a waist circle (that is, the shape of a runway in a standard playground), and the two grooves 6 at the common vertex of the two adjacent metal frames 150 are assembled into a half waist circle, such as Figure 4 As shown in position A and position B in FIG. If four adjacent metal frames 150 share a vertex, a groove 6 extending downward from the top of the multilayer printed circuit board 30 is respectively set at the four vertex corners of the common vertex of the four adjacent metal frames 150. The top view of a single groove 6 is a quarter of a waist circle. The four grooves 6 at the common vertex of the four adjacent metal frames 150 are assembled into a complete waist circle, as shown in FIG. Figure 4 As shown in position C in FIG. A metal through hole (not shown) is provided at the bottom of each groove 6 , and the metal through hole passes through the bottom of the multilayer printed circuit board 30 from the bottom of each groove 6 .

[0038] As Figure 4 For an alternative to the first embodiment shown, please refer to Figure 5 The top view of a single groove 6 is an isosceles right triangle. The two grooves 6 of the common vertex of two adjacent metal frames 150 are assembled into an equiangular right triangle with twice the area, such as Figure 5 As shown in position A and position B in FIG. The four grooves 6 at the common vertex of four adjacent metal frames 150 are assembled into a square with four times the area, as shown in FIG. Figure 5 As shown in position C.

[0039] As Figure 4 For another alternative to the first embodiment shown, please refer to Figure 6 The top view of a single groove 6 is a quarter of a rounded rectangle. The two grooves 6 of the common vertex of two adjacent metal frames 150 are combined into a half of a rounded rectangle. Figure 6 As shown in position A and position B in FIG. The four grooves 6 at the common vertices of four adjacent metal frames 150 are assembled into a complete rounded rectangle, as shown in FIG. Figure 6 As shown in position C.

[0040] Figure 4Other alternatives to the illustrated embodiment 1 include: the top view shape of a single groove 6 is a non-isosceles right triangle, a quarter of an ellipse, a quarter of a circle, etc.

[0041] See also Figure 7 , the second embodiment of the mutual coupling suppression structure between antenna units of the array antenna based on the printed circuit board proposed in the present application is that a plurality of antenna units 100 (white filling part) for constituting the array antenna are made in the multi-layer printed circuit board 30 (dark gray filling part). When the antenna units are arrayed, a rectangular metal frame 150 (light gray filling part) is set around each antenna unit 100 for separation. The rectangular metal frame 150 has four sides and four vertices, and the widths of different sides can be the same or different. The sides of all metal frames 150 have only two directions, either parallel to the X-axis direction or parallel to the Y-axis direction. If there are two adjacent metal frames 150 that share an edge in a certain direction (for example, they share an edge in the Y-axis direction), then a groove 6 extending downward from the top of the multi-layer printed circuit board 30 is respectively set on both sides of the common edge of the two adjacent metal frames 150, and the top view shape of a single groove 6 is half of an ellipse, and the two grooves 6 on the common edge of the two adjacent metal frames 150 are assembled into a complete ellipse, such as Figure 7 As shown in the position D in FIG. A metal through hole (not shown) is provided at the bottom of each groove 6 , and the metal through hole passes through the bottom of the multilayer printed circuit board 30 from the bottom of each groove 6 .

[0042] As Figure 7 For an alternative to the second embodiment shown, please refer to Figure 8 The top view of a single groove 6 is an isosceles triangle. The two grooves 6 on the common side of two adjacent metal frames 150 are assembled into a rhombus with twice the area, such as Figure 8 As shown in position D.

[0043] As Figure 7 For another alternative to the second embodiment shown, please refer to Fig. 9 The top view of a single groove 6 is half a rectangle. The two grooves 6 of the common side (for example, the side in the X-axis direction) of two adjacent metal frames 150 are assembled into a complete rectangle. Fig. 9 As shown in position D.

[0044] As Figure 7 For another alternative to the second embodiment shown, please refer to Fig.10 The top view of a single groove 6 is half of a round shape. The two grooves 6 of the common side (for example, the side in the X-axis direction) of two adjacent metal frames 150 are assembled into a complete round shape. Fig.10 As shown in position D.

[0045] Figure 7 Other alternatives to the second embodiment include: the top view shape of a single groove 6 is a non-isosceles triangle, a half rounded rectangle, a half circle, etc.

[0046] Figure 7 In the second embodiment shown, grooves of common edges in different directions can be arranged in a superimposed manner. Figure 7 Grooves are set on both sides of the common edge in the Y-axis direction. Fig. 9 The grooves are arranged on both sides of the common edge in the X-axis direction, and the two can be superimposed. At this time, the grooves arranged on the common edge in the two directions are independent of each other, and their top view shapes and sizes can be the same or different.

[0047] Figure 7 In the second embodiment shown, the grooves 6 arranged on both sides of the common edge in a certain direction may be located at the center of the common edge or may not be located at the center of the common edge (e.g. Figure 7-10 as shown).

[0048] Figures 4 to 10 In the two embodiments shown, a single groove 6 can be only within the range of the metal frame 150 (eg, Figure 4 , Figure 6 , Fig. 9 Alternatively, a single groove 6 may also break through the range of the metal frame 150 and be within the range of both the metal frame 150 and the multilayer printed circuit board 30 when viewed from a top view (as shown in FIG. Figure 5 , Figure 7 , Figure 8 , Fig.10 In any case, the groove 6 cannot fall within the range of the antenna unit 100 when viewed from a top view.

[0049] Depend on Figures 4 to 10 It can be seen that the position and shape of the groove 6 provided in the present application have a variety of variations, without strict restrictions, and need to be adjusted for different antenna units, array antenna layouts, array antenna covers, and the materials and processes used. When adjusting the position of the groove 6 relative to the antenna unit 100, due to the different electromagnetic field distributions at different positions around the antenna unit 100, the strength and phase of the initial coupling can be controlled by adjusting the position of the groove 6. Then, adjusting the top view shape of the groove 6 can further fine-tune the strength and phase of the initial coupling, thereby flexibly suppressing and canceling the coupling between the antenna units of the array antenna.

[0050] See also Fig.11, which is a partial cross-sectional schematic diagram of the mutual coupling suppression structure between antenna units of the array antenna based on the printed circuit board proposed in the present application. As an example, a multi-layer printed circuit board 30 includes from bottom to top: a first floor layer 31, a first feeder substrate layer 32, a second floor layer 33, a second feeder substrate layer 34, a third floor layer 35, a first antenna substrate layer 36, a fourth floor layer 37, a second antenna substrate layer 38, and a ninth floor layer 39. Floor layers 31, 33, 35, 37, and 39 are metal materials, indicated by light blue filling, and each floor layer may occupy all or part of the printed circuit board area. Feeder substrate layers 32, 34 and antenna substrate layers 36, 38 are all dielectric materials, indicated by oblique line filling. Each metal layer is made above or below each dielectric layer and can be regarded as a whole with the dielectric layer. There is a semi-cured sheet layer 40 between different dielectric layers, indicated by diamond grid filling. The semi-cured sheet layer 40 is used to bond single-layer printed circuit boards together to form a multi-layer printed circuit board. The total thickness of the multilayer printed circuit board 30 is H. A dielectric board is located above the multilayer printed circuit board 30 and serves as an antenna cover 20 of the array antenna.

[0051] Fig.11 In the figure, part of the third floor layer 35 is filled with white, indicating that the third floor layer 35 here is removed. There are multiple metal through holes in the multilayer printed circuit board 30, and some metal through holes 41 and 43 penetrate the entire multilayer printed circuit board 30; some metal through holes 42 do not penetrate the entire multilayer printed circuit board 30 from the top of the multilayer printed circuit board 30, for example, from the top fifth floor layer 39 to the second floor layer 33. Various antenna units (not shown) are made in the multilayer printed circuit board 30. When the antenna units are arrayed, a rectangular metal frame (not shown) is set around each antenna unit to separate them. A groove 6 is set at the position of the common vertex of each metal frame or the common edge in a certain direction, which is represented by a dotted box. The side wall and bottom of the groove 6 can optionally have a metal plating layer 7, which is filled with orange. A metal through hole 5 is also provided at the bottom of each groove 6. The metal through hole 5 penetrates the bottom of the multilayer printed circuit board 30 from the bottom of each groove 6 to the bottommost layer (at the bottom). Fig.11 In the middle is the first floor layer 31).

[0052] Fig.11 There are two types of metal through holes. The first type of metal through holes is opened downward from the top of the multilayer printed circuit board 30, and may penetrate the multilayer printed circuit board 30, such as metal through holes 41 and 43; or may not penetrate the multilayer printed circuit board 30, such as metal through hole 42. The second type of metal through holes is opened downward from the bottom of the groove 6 and penetrates the multilayer printed circuit board 30, such as metal through hole 5.

[0053] Compare Figure 1 and Fig.11 It can be found that the number of layers and structures of multilayer printed circuit boards vary greatly. But in summary, a multilayer printed circuit board always includes an antenna substrate layer located at the top and a feeder substrate layer located at the bottom. The antenna substrate layer may have one or more layers, and the feeder substrate layer may also have one or more layers. The substrate layer is a dielectric material. There is usually a floor layer between the antenna substrate layer and the feeder substrate layer, and there may also be a floor layer above the top antenna substrate layer, and there may also be a floor layer below the bottom feeder substrate layer. If there are multiple antenna substrate layers, there are usually floor layers between different antenna substrate layers. If there are multiple feeder substrate layers, there are usually floor layers between different feeder substrate layers. The floor layer is a metal material, and each floor layer may occupy all or part of the printed circuit board area. Each antenna unit used to form an array antenna is always made in the antenna substrate layer and the feeder substrate layer of a multilayer printed circuit board, and of course also includes the floor layers above and between the substrate layers involved. In the mutual coupling suppression structure between antenna units of the array antenna based on the printed circuit board proposed in the present application, the bottom of the groove 6 may be in the antenna substrate layer or in the feeder substrate layer. Preferably, the length and width of the groove 6 do not exceed one-third of the antenna unit spacing L to avoid encroaching on the space of the antenna unit on the multi-layer printed circuit board. The depth of the groove 6 does not exceed two-thirds of the total thickness H of the multi-layer printed circuit board to avoid affecting the mechanical strength of the multi-layer printed circuit board.

[0054] See also Figures 12 to 17 The cross-sectional shape of the groove 6 (black dashed box) proposed in this application is very flexible and only needs to match the manufacturing process used. The cross-sectional shape of the groove 6 can be a rectangle, such as Fig.12 , Fig.14 , Fig.15 As shown; it can also be stepped, such as Fig.13 , Fig.16 It can also be ∩-shaped, that is, there is a convex structure inside the groove 6, such as Fig.17 As shown; it can also be an inverted trapezoid with a larger top and a smaller bottom, a regular trapezoid with a smaller top and a larger bottom, etc. When the depth (bottom) of the groove 6 is only in the antenna substrate layer, the cross-sectional shape of the groove 6 mainly affects the surface wave coupling existing inside the multilayer printed circuit board, and has little effect on the coupling of the guided wave coupling existing at the bottom of the multilayer printed circuit board. When the depth (bottom) of the groove 6 reaches the feeder substrate layer, it also has a certain inhibitory effect on the guided wave coupling at the bottom of the multilayer printed circuit board. From a technical principle, it is equivalent to adding interference to the original surface wave coupling and guided wave coupling path, so that the electromagnetic environment between the antenna units after adding the groove 6 is not conducive to the generation of surface wave coupling and guided wave coupling.

[0055] See also Figures 12 to 17The relative positions of the groove 6 and the metal through hole 5 proposed in the present application are also flexible. The metal through hole 5 can penetrate the multilayer printed circuit board downward at the center of the bottom of the groove 6, such as Fig.12 It is also possible to deviate from the central position at the bottom of the groove 6 and penetrate the multilayer printed circuit board downward, such as Fig.13 , Fig.15 , Fig.16 It is also possible to penetrate the multilayer printed circuit board downward at the edge of the bottom of the groove 6, such as Fig.14 If there is a protruding structure inside the groove 6, the position of the metal through hole 5 has nothing to do with the position of the protruding structure, and can even be below the protruding structure, such as Fig.17 The relative position change between the groove 6 and the metal through hole 5 will significantly affect the waveguide coupling at the bottom of the multilayer printed circuit board. The different positions of the metal through hole 5 will have a significant impact on the intensity and phase of the waveguide coupling. Adjusting the position of the metal through hole 5 is an effective mutual coupling tuning method for the waveguide coupling.

[0056] See also Figures 12 to 17 In the present application, the side wall and the bottom surface of the groove 6 may not be coated with a metal coating, such as Fig.15 , Fig.16 , Fig.17 As shown; the metal coating 7 may also be applied only on the side wall of the groove 6 (not shown); the metal coating 7 may also be applied only on the bottom surface of the groove 6, such as Fig.14 It is also possible to simultaneously coat the side walls and bottom surface of the groove 6 with a metal coating 7, such as Fig.12 , Fig.13 As shown, the presence or absence of the metal plating layer 7 on the side wall of the groove 6 mainly affects the surface wave coupling existing inside the multilayer printed circuit board. The presence or absence of the metal plating layer 7 on the bottom surface of the groove 6 mainly affects the guided wave coupling existing at the bottom of the multilayer printed circuit board.

[0057] The present application can independently and flexibly adjust the cross-sectional shape of the groove 6, the positional relationship between the groove 6 and the metal through hole 5, and the surface treatment method of the side wall and bottom of the groove 6 based on the design of the array antenna and the actual process, so as to obtain the qualified mutual coupling suppression effect and achieve the purpose of coupling cancellation.

[0058] For the array antenna based on the printed circuit board, the design process of the mutual coupling suppression structure proposed in this application is as follows. First, the antenna unit of the array antenna is selected and designed based on the operating frequency, scanning range, mechanical strength and other indicators. Then the array antenna cover and feeder layer are designed. Then a groove 6 is set between the antenna units and in the metal frame area around the antenna unit (or slightly larger than the area). By adjusting the position, shape (top view shape and cross-sectional shape), size (size and depth), side wall and bottom surface of the groove 6, whether the metal plating process is selected, the coupling between the antenna units is controlled, which is mainly used to suppress guided wave coupling and surface wave coupling. Then a metal through hole 5 is set at the bottom of the groove 6, and a controllable new coupling path is formed by adjusting the number of metal through holes 5, the relative position and size (size and depth) of the groove 6, which is mainly used to offset surface wave coupling + guided wave coupling + space coupling. Finally, the design parameters of the overall structure are jointly fine-tuned (jointly debugged) to obtain the required array scanning performance within the working frequency band and determine the mutual coupling suppression effect.

[0059] comprehensive Figures 4 to 17 , the present application introduces additional grooves 6 and metal through holes 5 at the bottom of the grooves in the multilayer printed circuit board used to make antenna units of the array antenna, which adds new design freedom for mutual coupling suppression and cancellation between antenna units of the array antenna. First, the present application adds grooves 6 between the antenna units of the array antenna, and the position, shape, size, sidewall and bottom surface process of the grooves 6 help to suppress surface wave coupling and waveguide coupling. Secondly, when the mutual coupling suppression effect of the grooves 6 is insufficient, the present application further introduces metal through holes 5 at the bottom of the grooves 6, which forms a controllable new coupling path between the antenna units. By adjusting the number, position and size of the metal through holes 5, the coupling coefficient amplitude and phase of the new coupling path can be flexibly manipulated. When the new coupling generated by the new coupling path is similar to the overall amplitude of the original surface wave coupling + waveguide coupling + space coupling but opposite in phase, the effect of canceling the coupling is achieved. Therefore, the present application has significant intensity suppression and cancellation of surface wave coupling, waveguide coupling and space coupling, so that the purpose of mutual coupling suppression between antenna units of the array antenna can be achieved more flexibly. In addition, the groove 6 and the metal through hole 5 at the bottom of the groove have little impact on the performance of the original array antenna.

[0060] See also Fig.18 , this is a comparative schematic diagram of the active reflection coefficient of the antenna unit during oblique scanning before and after the mutual coupling suppression structure of the present application is adopted. Figure 3 Shown is the passive port reflection coefficient when the antenna elements are not arrayed. Fig.18 What is shown is the active reflection coefficient after the same antenna units form an array, that is, the active port reflection coefficient of the same antenna unit after the mutual coupling effect is taken into account. Fig.18In the figure, the dotted line indicates that before the mutual coupling suppression structure of the present application is adopted, after multiple antenna units are used in an array, an abnormal point of active reflection coefficient is generated within the working frequency band due to mutual coupling during scanning, and an obvious active reflection high point is generated at the f0 frequency position, which will make the array antenna unable to work normally at the f0 frequency position, and form a scanning blind spot with specific frequency points and angles during oblique scanning. The solid line indicates that after the mutual coupling suppression structure of the present application is adopted, the coupling strength of some coupling paths is adjusted through the groove and the metal through-holes at the bottom, and the total coupling strength between the antenna units is reduced, eliminating the active reflection strong point and its corresponding scanning blind spot.

[0061] See also Fig.19 , this is a comparative schematic diagram of the antenna unit radiation pattern in the array during oblique scanning before and after the mutual coupling suppression structure of the present application is adopted. The dotted line represents the main polarization amplitude before the mutual coupling suppression structure of the present application is adopted, and the solid line represents the main polarization amplitude after the mutual coupling suppression structure of the present application is adopted. The dash-dotted line represents the cross-polarization amplitude before the mutual coupling suppression structure of the present application is adopted, and the dotted line represents the cross-polarization amplitude after the mutual coupling suppression structure of the present application is adopted. The lower the curve of the same indicator is, the better the performance. After comparison, it can be seen that the present application adjusts the coupling strength of some coupling paths through the groove and the metal through-holes at the bottom thereof, thereby weakening the radiation degradation phenomenon caused by mutual coupling, which is specifically manifested in suppressing the cross-polarization amplitude, which helps to improve the radiation performance of the array antenna. At the same time, the mutual coupling suppression structure proposed in the present application does not affect the main polarization radiation performance of the antenna unit, which helps to maintain the original radiation performance design.

[0062] Compared with the prior art, the main technical advantages of the mutual coupling suppression structure proposed in this application are as follows. First, it is very compatible with the array antenna manufactured by the printed circuit board process and does not require additional process support. Second, compared with the traditional isolation barrier method (such as Figure 2 As shown in the figure), the mutual coupling suppression capability is significantly improved. Third, compared with the decoupling network method, the design complexity and structural complexity are low, which is convenient for engineering implementation. Fourth, compared with adding additional mutual coupling isolation devices, no additional three-dimensional structures and various supporting and fixing devices are introduced, which will not increase the system volume or its structural complexity, will not bring obvious burden to the mechanical strength design, and will not cause significant changes in radiation performance due to the introduction of additional scatterers. Fifth, compared with the previous coupling cancellation structure, a new mutual coupling suppression design freedom is introduced at a very small structural design cost, which helps to improve the mutual coupling suppression performance.

[0063] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should all be included in the protection scope of the present application.

Claims

1. A mutual coupling suppression structure between antenna units of an array antenna based on a printed circuit board, characterized in that: A plurality of antenna units for forming an array antenna are made in a multilayer printed circuit board, and a rectangular metal frame is arranged around each antenna unit for separation; the sides of all metal frames have only two directions, either parallel to the X-axis direction or parallel to the Y-axis direction; a groove extending downward from the top of the multilayer printed circuit board is arranged at the position of the common vertex or common edge of two or four adjacent metal frames, and a metal through hole is arranged at the bottom of each groove, and the metal through hole penetrates the multilayer printed circuit board from the bottom of each groove; two or four grooves at the common vertex or common edge of two or four adjacent metal frames are spliced ​​into a closed shape; If there are and only two adjacent metal frames that share a vertex, a groove extending downward from the top of the multilayer printed circuit board is respectively set at the two vertex corners of the common vertex of the two adjacent metal frames, and the top view shape of a single groove is a quarter of a waist circle, and the two grooves of the common vertex of the two adjacent metal frames are combined into a half waist circle; if there are four adjacent metal frames that share a vertex, a groove extending downward from the top of the multilayer printed circuit board is respectively set at the four vertex corners of the common vertex of the four adjacent metal frames, and the top view shape of a single groove is a quarter of a waist circle, and the four grooves of the common vertex of the four adjacent metal frames are combined into a complete waist circle; or, the top view shape of a single groove is changed to any one of the following: an isosceles right triangle, a half rounded rectangle, a non-isosceles right triangle, a quarter of an ellipse, or a quarter of a circle; If two adjacent metal frames share an edge in a certain direction, a groove extending downward from the top of the multilayer printed circuit board is provided on both sides of the shared edge of the two adjacent metal frames, and the top view shape of a single groove is half an ellipse, and the two grooves of the shared edge of the two adjacent metal frames are assembled into a complete ellipse; or, the top view shape of a single groove is changed to any one of the following: an isosceles triangle, half a rectangle, half a girdle circle, a non-isosceles triangle, half a rounded rectangle, or half a circle.

2. The mutual coupling suppression structure between antenna units of the array antenna based on a printed circuit board according to claim 1, characterized in that: Grooves are arranged on both sides of the common edge parallel to the X-axis direction, and grooves are arranged on both sides of the common edge parallel to the Y-axis direction; the grooves arranged on the common edges in the two directions are independent of each other.

3. The mutual coupling suppression structure between antenna units of the array antenna based on a printed circuit board according to claim 1, characterized in that: The groove is only within the range of the metal frame when viewed from a top view; or, the groove is within the range of both the metal frame and the multilayer printed circuit board when viewed from a top view, but cannot fall within the range of the antenna unit.

4. The mutual coupling suppression structure between antenna units of the array antenna based on a printed circuit board according to claim 1, characterized in that: The strength and phase of the initial coupling between the antenna units are controlled by adjusting the position of the groove relative to the antenna unit, and the strength and phase of the initial coupling between the antenna units are fine-tuned by adjusting the top view shape of the groove.

5. The mutual coupling suppression structure between antenna units of the array antenna based on a printed circuit board according to claim 1, characterized in that: The multi-layer printed circuit board includes an antenna substrate layer located at the top and a feeder substrate layer located at the bottom, the antenna substrate layer has one or more layers, and the feeder substrate layer has one or more layers; a floor layer is provided at one or more locations between the antenna substrate layer and the feeder substrate layer, above the top antenna substrate layer, below the bottom feeder substrate layer, between multiple antenna substrate layers, and between multiple feeder substrate layers; each antenna unit used to form an array antenna is made in the antenna substrate layer and the feeder substrate layer of the multi-layer printed circuit board.

6. The mutual coupling suppression structure between antenna units of the array antenna based on a printed circuit board according to claim 1, characterized in that: The length and width of a single groove do not exceed one third of the antenna unit spacing, and the depth of the groove does not exceed two thirds of the total thickness of the multilayer printed circuit board.

7. The mutual coupling suppression structure between antenna units of the array antenna based on a printed circuit board according to claim 1, characterized in that: The cross-sectional shape of a single groove is any one of the following: rectangular, stepped, ∩-shaped, inverted trapezoidal, and regular trapezoidal.

8. The mutual coupling suppression structure between antenna units of the array antenna based on a printed circuit board according to claim 7, characterized in that: The bottom of the groove is either in the antenna substrate layer or in the feeder substrate layer; when the bottom of the groove is in the antenna substrate layer, the cross-sectional shape of the groove affects the surface wave coupling between the antenna units; when the bottom of the groove reaches the feeder substrate layer, the cross-sectional shape of the groove affects both the surface wave coupling and the waveguide coupling between the antenna units.

9. The mutual coupling suppression structure between antenna units of the array antenna based on a printed circuit board according to claim 1, characterized in that: The relative position of the metal through hole and the groove is any one of the following: the metal through hole is at the center of the bottom of the groove, the metal through hole is at a position deviated from the center of the bottom of the groove, the metal through hole is at the edge of the bottom of the groove, and if there is a protruding structure inside the groove, the position of the metal through hole is independent of the position of the protruding structure; the relative position of the metal through hole and the groove affects the guided wave coupling between the antenna units.

10. The mutual coupling suppression structure between antenna units of the array antenna based on a printed circuit board according to claim 1, characterized in that: The bottom surface and / or side wall of the groove are not coated with metal plating, or the groove is coated with metal plating only on the side wall, or the groove is coated with metal plating only on the bottom surface, or the groove is coated with metal plating on both the side wall and the bottom surface; the presence or absence of metal plating on the side wall of the groove affects the surface wave coupling between the antenna units; the presence or absence of metal plating on the bottom surface of the groove affects the guided wave coupling between the antenna units.

11. The mutual coupling suppression structure between antenna units of the array antenna based on a printed circuit board according to claim 1, characterized in that: When designing the mutual coupling suppression structure, a groove is first set, and the position, shape, size, side wall and bottom of the groove are adjusted to suppress the guided wave coupling and surface wave coupling between the antenna units; then a metal through hole is set at the bottom of the groove, and a controllable new coupling path is formed by adjusting the number of the metal through holes, the relative position and size of the groove to offset the surface wave coupling, guided wave coupling and spatial coupling between the antenna units.

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