Pseudo-surface plasmon polarization pathway structure and circuit board

Abstract

The invention proposes a fabricated surface plasmon polarization conduit structure, circuit board, and electronic device, to reduce the size of the SSPP conduit structure. The SSPP conduit structure consists of a first bipolar substrate, a first metal strip, and a second metal strip. The first and second metal strips are arranged on opposite surfaces of the first bipolar substrate, respectively. The first and second metal strips extend separately in the first direction, and the length of the first metal strip in the first direction is less than the length of the second metal strip in the first direction. In the first direction, the cross-sectional area of ​​the first metal strip gradually decreases, and at least one side of the second metal strip has spaced protrusions.

Description

Artificial surface plasmon transmission line structure, circuit board and electronic equipment

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of China on August 31, 2020, with application number 202010907536.7 and application name “An artificial surface plasmon transmission line structure, circuit board and electronic device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of microwave technology, and in particular to an artificial surface plasmon transmission line structure, a circuit board, and an electronic device. Background Art

[0004] Artificial surface plasmon polaritons (SSPPs) are special electromagnetic wave modes excited on the surface of specific periodic structures within microwave or terahertz frequency bands. Compared to naturally occurring surface plasmon polaritons (SPPs), SSPPs have attracted widespread attention due to their high binding capacity, low loss, short operating wavelength, and conformal transmission. The periodic metal structures that propagate SSPPs are called SSPP transmission lines. With the advancement of research in recent years, SSPP transmission lines have gradually evolved from three-dimensional to two-dimensional structures, allowing them to be processed using modern printed circuit board processes, promoting low-cost, large-scale, and practical applications.

[0005] In order to connect SSPP transmission lines with existing microwave transmission lines, coplanar waveguides are usually used to convert microwave transmission lines, or coaxial waveguides, microstrip lines, slot lines and other transmission line forms are used. The disadvantage of these transmission structures is that they require a large space and the overall width is several times the width of the SSPP transmission line, which is not conducive to the compact integrated design of the equipment.

[0006] Summary of the Invention

[0007] The present application provides an artificial surface plasmon transmission line structure, a circuit board, and an electronic device, which are used to reduce the size of the artificial surface plasmon transmission line structure.

[0008] In a first aspect, the present application provides an SSPP transmission line structure, which may include a first dielectric substrate and a first metal strip and a second metal strip, wherein the first dielectric substrate can be used to support and fix the first metal strip and the second metal strip, and the first metal strip and the second metal strip are respectively arranged on two opposite surfaces of the first dielectric substrate, and the first metal strip and the second metal strip respectively extend along a first direction, along the first direction, the length of the first metal strip is less than the length of the second metal strip, and the cross-sectional area of ​​the first metal strip gradually decreases until it is zero; at least one side of the second metal strip has a plurality of protrusions arranged at intervals, and the periodically arranged protrusions have corresponding signal operating frequencies. In the process of the first metal strip gradually changing and disappearing, the signal energy originally distributed between the first metal strip and the second metal strip will gradually couple to the second metal strip, so that the second metal strip is finally formed into an SSPP transmission line with a single-layer metal structure.

[0009] In the above scheme, the SSPP transmission line structure can couple the signal energy in the vertical direction through the spatially stacked first metal strip and the second metal strip, and finally concentrate the signal energy on the second metal strip, so that the second metal strip is formed into an SSPP transmission line with a single-layer metal structure. Compared with the existing technology of using coplanar waveguides to couple energy in the horizontal direction, this scheme can reduce the width of the SSPP transmission line structure, thereby reducing the occupied circuit space.

[0010] In one specific embodiment, the SSPP transmission line structure may further include a second dielectric substrate and a third metal strip. The second dielectric substrate may be stacked on a side of the first dielectric substrate where the second metal strip is disposed, and the third metal strip may be disposed on a side of the second dielectric substrate facing away from the first dielectric substrate, such that the third metal strip and the second metal strip are separated by the second dielectric substrate. Specifically, the third metal strip may extend along a first direction, with its length being shorter than that of the second metal strip along the first direction, and its cross-sectional area gradually decreasing. In this manner, as the first and third metal strips gradually change and disappear, signal energy previously distributed between the second and third metal strips is gradually coupled to the second metal strip, ultimately forming an SSPP transmission line with a single-layer metal structure.

[0011] In order to reduce the manufacturing cost of the SSPP transmission line structure and improve its manufacturing accuracy, in some possible implementations, the patterns of the first metal strip, the second metal strip, and the third metal strip may be formed by etching processes.

[0012] In a specific embodiment, along the first direction, the second metal strip may include a first section and a second section connected to each other. On the first section, the area of ​​each protrusion may gradually increase as the second metal strip extends. When the signal energy between the first metal strip and the second metal strip, and between the second metal strip and the third metal strip is gradually coupled to the second metal strip, the area of ​​the protrusion also increases to a certain set value. The second metal strip transitions from the first section to the second section. On the second section, the area of ​​each protrusion is stable at the above set value, and the signal energy can be concentrated on the second section. The second section is thus formed into an SSPP transmission line with a single-layer metal structure.

[0013] In a specific embodiment, on the same side of the second metal strip, the protrusions may be arranged at substantially equal intervals to improve signal transmission quality.

[0014] When protrusions are respectively provided on both sides of the second metal strip, in a specific embodiment, along the first direction, the first metal strip and the third metal strip respectively have a first end and a second end positioned opposite to each other, and a first notch may be provided at the first end of the first metal strip, and the first notch extends toward the first end of the first metal strip, dividing the first metal strip into a first branch and a second branch, and along the first direction, the widths of the first branch and the second branch gradually decrease until they are reduced to zero at the second end of the first metal strip, thereby achieving a rule that the cross-sectional area of ​​the first metal strip gradually decreases; similarly, a second notch may be provided at the first end of the third metal strip, and the second notch extends toward the first end of the third metal strip, dividing the third metal strip into a third branch and a fourth branch, and along the first direction, the widths of the third branch and the fourth branch gradually decrease until they are reduced to zero at the second end of the third metal strip, thereby achieving a rule that the cross-sectional area of ​​the third metal strip gradually decreases.

[0015] In another specific embodiment, along the first direction, the two side surfaces of the first metal strip may gradually approach each other until they intersect, so as to achieve a gradual reduction in the width of the first metal strip; similarly, the two side surfaces of the third metal strip may also gradually approach each other until they intersect, so as to achieve a gradual reduction in the width of the third metal strip.

[0016] In specific design, along the first direction, the width of the first metal strip may gradually decrease in a step-like manner; or, the width of the first metal strip may decrease linearly; or, the two side surfaces of the first metal strip may be designed as arc-shaped surfaces, and in the process of the two side surfaces of the first metal strip gradually approaching each other, the width of the third metal strip decreases nonlinearly; similarly, along the first direction, the width of the third metal strip may gradually decrease in a step-like manner; or, the width of the third metal strip may decrease linearly; or, the two side surfaces of the third metal strip may be designed as arc-shaped surfaces, and in the process of the two side surfaces of the third metal strip gradually approaching each other, the width of the third metal strip decreases nonlinearly.

[0017] In addition, when protrusions are provided on both sides of the second metal strip, the number of protrusions on both sides of the second metal strip can be the same or different, and this application does not impose specific restrictions on this. When the number of protrusions on both sides of the first metal strip is equal, the positions of the protrusions on both sides can be opposite or staggered.

[0018] In a specific embodiment, the first metal strip and the third metal strip may respectively include a first side and a second side, wherein the first side may be the same side as the protruding side on which the protrusion is provided on the second metal strip. When specifically set, the second side of the first metal strip gradually tilts toward the first side of the first metal strip and intersects with the first side of the first metal strip to achieve a gradual reduction in width; the second side of the third metal strip may also gradually tilt toward the first side of the third metal strip and intersect with the first side of the third metal strip to achieve a gradual reduction in width.

[0019] In addition, in order to improve the signal transmission quality and the coupling efficiency of the signal energy, the vertical projection of the first metal strip on the second dielectric substrate may overlap with the third metal strip.

[0020] When the first metal strip is disposed on the first dielectric substrate, the first metal strip may be attached to the surface of the first dielectric substrate, or the first metal strip may be embedded in the surface of the first dielectric substrate, as long as the first metal strip can be fixed on the surface of the first dielectric substrate.

[0021] Similarly, the second metal strip can be attached between the first dielectric substrate and the second dielectric substrate, or can be embedded in the surface of the first dielectric substrate, or can be embedded in the surface of the first dielectric substrate, or can be partially embedded in the first dielectric substrate and the other part embedded in the second dielectric substrate, as long as the first dielectric substrate and the second dielectric substrate can be fixed.

[0022] When the third metal strip is disposed on the second dielectric substrate, the third metal strip may be attached to the surface of the second dielectric substrate, or the third metal strip may be embedded in the surface of the second dielectric substrate, as long as the third metal strip can be fixed on the surface of the second dielectric substrate.

[0023] Secondly, the present application also provides a circuit board that may include the SSPP transmission line structure described in any of the aforementioned possible embodiments. In a transmission line interconnection scenario within a microwave circuit composed of a multilayer board, the SSPP transmission line structure 100 can be used for transmission line conversion within the circuit board to simplify the circuit structure. For example, as shown in FIG23 , for a multilayer board with a complex circuit structure and long transmission distance, the SSPP transmission line structure 100 can couple a shielded stripline with the artificial surface plasmon transmission line structure to achieve single-layer transmission, further simplifying the circuit board structure. Furthermore, because the SSPP transmission line has a relatively large phase velocity, this conversion method can also shorten the length of the phase delay line, thereby making the overall circuit structure more compact.

[0024] The circuit board may also include an interface, which can be a coaxial connector connected to a coaxial transmission line external to the circuit board. The SSPP transmission line structure can be coupled to the connector to convert the coaxial transmission line into an SSPP transmission line on the circuit board. In a specific implementation, the first metal strip of the transmission line structure can be coupled to the outer conductor of the coaxial transmission line via the interface, and the second metal strip can be coupled to the inner conductor of the coaxial transmission line via the interface. This allows the signal from the coaxial transmission line to be transmitted to the SSPP transmission line structure. The SSPP transmission line structure then converts the signal energy into the second metal strip, ultimately forming a single-layer metal structure SSPP transmission line on the circuit board.

[0025] In a third aspect, the present application also provides an electronic device, which may include the circuit board in the aforementioned solution. The coaxial transmission line outside the electronic device can be converted into the SSPP transmission line on the circuit board by utilizing the transmission line structure on the circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG1 is a schematic structural diagram of an SSPP transmission line structure provided in an embodiment of the present application;

[0027] FIG2 is a cross-sectional view of the SSPP transmission line structure in FIG1 taken perpendicular to a first direction;

[0028] FIG3 is a cross-sectional view perpendicular to a first direction of another SSPP transmission line structure provided in an embodiment of the present application;

[0029] FIG4 is a bottom view of a first dielectric substrate provided in an embodiment of the present application;

[0030] FIG5 is a schematic diagram of the electric field vector distribution at a certain moment within an electric field variation cycle in an SSPP transmission line structure provided by an embodiment of the present application;

[0031] FIG6 is a schematic structural diagram of another SSPP transmission line structure provided in an embodiment of the present application;

[0032] FIG7 is a cross-sectional view of the SSPP transmission line structure in FIG6 taken perpendicular to the first direction;

[0033] FIG8 is a cross-sectional view perpendicular to the first direction of another SSPP transmission line structure provided in an embodiment of the present application;

[0034] FIG9 is a schematic diagram of the electric field vector distribution at a certain moment within the electric field variation cycle in another SSPP transmission line structure provided by an embodiment of the present application;

[0035] FIG10 is a bottom view of the first dielectric substrate shown in FIG6;

[0036] FIG11 is a top view of the SSPP transmission line structure shown in FIG6 ;

[0037] FIG12 is a graph showing S-parameter simulation results of the SSPP transmission line structure docking model shown in FIG6 ;

[0038] FIG13 is a schematic structural diagram of another SSPP transmission line structure provided in an embodiment of the present application;

[0039] FIG14 is a top view of the SSPP transmission line structure shown in FIG13;

[0040] FIG15 is a schematic structural diagram of another SSPP transmission line structure provided in an embodiment of the present application;

[0041] FIG16 is a top view of the SSPP transmission line structure shown in FIG15 ;

[0042] FIG17 is a structural diagram of another SSPP transmission line structure provided in an embodiment of the present application;

[0043] FIG18 is a top view of the SSPP transmission line structure shown in FIG17 ;

[0044] FIG19 is a bottom view of another first dielectric substrate provided in an embodiment of the present application;

[0045] FIG20 is a schematic structural diagram of another SSPP transmission line structure provided in an embodiment of the present application;

[0046] FIG21 is a bottom view of the first dielectric substrate in FIG20;

[0047] FIG22 is a top view of the SSPP transmission line structure shown in FIG20 ;

[0048] FIG23 is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application;

[0049] FIG24 is a schematic diagram of the conversion principle of the SSPP transmission line structure provided in an embodiment of the present application.

[0050] Reference numerals:

[0051] 100-SSPP transmission line structure; 10-first dielectric substrate; 20-first metal strip; 30-second metal strip; 31-protrusion; 40-second dielectric substrate; 50-third metal strip; 21-first notch; 22-first branch; 23-second branch; 24-first side; 25-second side; 200-electronic device; 300-circuit board; 310-interface; 400-coaxial transmission line. DETAILED DESCRIPTION

[0052] In order to facilitate understanding of the embodiments of the present application, its application scenario is first explained below. The SSPP transmission line structure provided in the embodiments of the present application can be applied to electronic devices to connect an external coaxial transmission line with an SSPP transmission line inside an electronic device, such as the conversion of internal and external connected transmission lines such as the radio frequency interface of a wireless base station and the front end of a high-frequency signal data acquisition; or it can also be used for transmission line conversion inside a circuit, such as coupling a strip line with a shielding layer with the artificial surface plasmon transmission line structure to achieve single-layer transmission. Among them, the electronic device can be a receiver, transmitter or antenna in the prior art, such as a television transmitter used in the field of the Internet of Things. In the conversion structure currently used, the conversion is usually achieved in the form of a coplanar waveguide. This conversion form is relatively large in size, and therefore requires a large installation space, which is not conducive to the miniaturization design of electronic equipment.

[0053] Based on this, embodiments of the present application provide an SSPP transmission line structure that couples different metal strips vertically. Compared to the prior art conversion method that uses coplanar waveguides for horizontal coupling, the width of this SSPP transmission line structure can be significantly reduced, thereby saving circuit board space. The SSPP transmission line structure provided by embodiments of the present application is described in detail below with reference to the accompanying drawings.

[0054] First, referring to Figures 1 and 2 , Figure 1 is a schematic diagram of an SSPP transmission line structure according to an embodiment of the present application, and Figure 2 is a cross-sectional view of the SSPP transmission line structure shown in Figure 1 taken perpendicular to a first direction. The SSPP transmission line structure 100 may include a first dielectric substrate 10 and a first metal strip 20 and a second metal strip 30. The first dielectric substrate 10 may be used to support and secure the first and second metal strips 20 and 30. In a specific implementation, the first and second metal strips 20 and 30 may be disposed on opposing surfaces of the first dielectric substrate 10, such that the two metal strips are spaced apart by the first dielectric substrate 10, thereby spatially overlapping.

[0055] The first dielectric substrate 10 can be either a flexible substrate or a rigid substrate, which is not limited in this application and can be configured based on actual needs. When the first dielectric substrate 10 is a flexible substrate, its material can be polyimide (PI), modified polyimide (MPI), or liquid crystal polymer (LCP). When the first dielectric substrate 10 is a rigid substrate, its material can be epoxy resin, ceramic, glass, phenolic cotton paper, etc.

[0056] 2 , in one embodiment of the present application, the first metal strip 20 and the second metal strip 30 may be attached to both side surfaces of the first dielectric substrate 10, respectively. Alternatively, as shown in FIG3 , in another SSPP transmission line structure provided in an embodiment of the present application, the first metal strip 20 and the second metal strip 30 may also be embedded in both side surfaces of the first dielectric substrate, respectively. Alternatively, the first metal strip 20 and the second metal strip 30 may also be fixed to the first dielectric substrate 10 by attachment and embedding, respectively.

[0057] In addition, in order to reduce the manufacturing cost of the SSPP transmission line structure and improve its manufacturing accuracy, in some embodiments of the present application, the patterns of the first metal strip 20 and the second metal strip 30 can be formed by etching processes respectively.

[0058] Figure 4 is a bottom view of a first dielectric substrate provided by an embodiment of the present application. Referring to Figures 1 and 4 , the first metal strip 20 and the second metal strip 30 can each extend along a first direction (i.e., the x-direction). The second metal strip 30 has a plurality of spaced-apart protrusions 31 on at least one side. The cross-sectional area of ​​the first metal strip 20 gradually decreases to zero as it extends. In other words, the first metal strip 20 gradually disappears along the first direction, and its length along the first direction is less than the length of the second metal strip 30 along the first direction. It can be understood that the aforementioned first direction is the direction of signal transmission within the SSPP transmission line structure. The second metal strip 30 is coupled and excites the desired mode of the SSPP transmission line. Referring also to FIG5 , the electric field vector can vary with the shape of the first metal strip 20. The periodically arranged protrusions 31 have a corresponding signal operating frequency. As the first metal strip 20 gradually changes and disappears, the signal energy originally distributed primarily between the first metal strip 20 and the second metal strip 30 is gradually coupled to the second metal strip 30, ultimately forming the second metal strip 30 into an SSPP transmission line having a single-layer metal structure. Thus, compared to the prior art method of utilizing coplanar waveguides for energy coupling in the horizontal direction, the embodiment of the present application can transform the interconnections between different metal conductors into the vertical direction, thereby reducing the width of the SSPP transmission line structure and thereby reducing the occupied circuit space.

[0059] It should be noted that FIG5 shows the electric field distribution diagram of the SSPP transmission line structure at a certain moment in the electric field variation cycle, where the direction of the arrow can be understood as the direction of the electric field in the half cycle at that moment. It can be understood that in the other half cycle of the same cycle, the direction of the electric field in the SSPP transmission line is opposite to the direction of the electric field shown in FIG5 .

[0060] Figure 6 is a schematic diagram of another SSPP transmission line structure provided in an embodiment of the present application, and Figure 7 is a cross-sectional view of the SSPP transmission line structure in Figure 6 taken perpendicular to a first direction. In this embodiment, the SSPP transmission line structure may further include a second dielectric substrate 40 and a third metal strip 50. The second dielectric substrate 40 may be stacked on a side of the first dielectric substrate 10 on which the second metal strip 30 is disposed, and the third metal strip 50 may be disposed on a side of the second dielectric substrate 40 facing away from the first dielectric substrate 10. In this case, the first metal strip 20 and the second metal strip 30 may be separated by the first dielectric substrate 10, and the second metal strip 30 and the third metal strip 50 may be separated by the second dielectric substrate 40, thereby spatially overlapping the three metal strips.

[0061] Similarly, the second dielectric substrate 40 can be a flexible substrate or a rigid substrate, and this application does not impose any restrictions on this. The material options for the second dielectric substrate 40 can refer to the description of the first dielectric substrate 10 above and will not be further elaborated here. Furthermore, the thickness of the second dielectric substrate 40 can be equal to or different from that of the first dielectric substrate 10. This application also does not impose any restrictions on this and can be adjusted based on actual needs.

[0062] The third metal strip 50 can also be fixed to the surface of the second dielectric substrate 40 by bonding or embedding. Referring to FIG7 , in one embodiment of the present application, the third metal strip 50 can be attached to the surface of the second dielectric substrate 40. Similarly, the first metal strip 20 can be attached to the surface of the first dielectric substrate 10, and the second metal strip 30 can be attached between the first dielectric substrate 10 and the second dielectric substrate 40. Alternatively, as shown in FIG8 , in another SSPP transmission line structure provided in an embodiment of the present application, the third metal strip 50 can be embedded in the surface of the second dielectric substrate 40, the first metal strip 20 can also be embedded in the surface of the first dielectric substrate 10, and the second metal strip 30 can be embedded in the surface of the first dielectric substrate 10, or in the surface of the second dielectric substrate 40, or can be partially embedded in the first dielectric substrate 10 and partially embedded in the second dielectric substrate 40.

[0063] In addition, the pattern of the third metal strip 50 can also be formed by an etching process to further reduce the manufacturing cost of the SSPP transmission line structure and improve its manufacturing accuracy.

[0064] In a specific configuration, the third metal strip 50 may also extend along the first direction (i.e., the x-direction), and the cross-sectional area of ​​the third metal strip 50 gradually decreases to zero as the length of the third metal strip 50 increases. That is, the third metal strip 50 gradually disappears along the first direction, and its length along the first direction is less than the length of the second metal strip 30 along the first direction. In this embodiment, the SSPP transmission line structure uses stripline feeding to couple to the second metal strip 30 and excite the required SSPP transmission line mode. Referring to FIG. 9 , the electric field vector may vary with the shape of the first and third metal strips 20, 50. The periodically arranged protrusions have corresponding signal operating frequencies. As the first and third metal strips 20, 50 gradually change and disappear, the signal energy originally distributed between the first and second metal strips 20, 30, and between the second and third metal strips 30, 50, is gradually coupled to the second metal strip 30, ultimately forming the second metal strip 30 into an SSPP transmission line with a single-layer metal structure.

[0065] Similarly, FIG9 shows the electric field distribution diagram of the SSPP transmission line structure at a certain moment in the electric field variation cycle, where the direction of the arrow can be understood as the direction of the electric field in the half cycle at that moment. It can be understood that in the other half cycle of the same cycle, the direction of the electric field in the SSPP transmission line is opposite to the direction of the electric field shown in FIG9 .

[0066] Referring to FIG10 , when specifically configuring the second metal strip 30, the areas of the protrusions on the second metal strip 30 may be equal or unequal, and this application is not limited thereto. In some possible embodiments, along a first direction, the second metal strip 30 may include a first segment L1 and a second segment L2, adjacent to each other. In the first segment L1, the areas of the protrusions 31 may gradually increase as the second metal strip 30 extends. As the signal energy between the first metal strip 20 and the second metal strip 30, and between the second metal strip 30 and the third metal strip 50, is gradually coupled to the second metal strip 30, the areas of the protrusions 31 also increase to a predetermined value. The second metal strip 30 then transitions from the first segment L1 to the second segment L2. In the second segment L2, the areas of the protrusions 31 stabilize at the predetermined value, allowing the signal energy to be concentrated in the second segment L2. This second segment L2 forms an SSPP transmission line having a single-layer metal structure.

[0067] The protrusions 31 can be arranged on one side of the second metal strip 30, such as the left or right side of the second metal strip 30, or can be located on the left and right sides of the second metal strip 30 respectively. In specific implementation, on the same side of the second metal strip 30, the protrusions 31 can be arranged at roughly equal intervals, that is, the spacing between any two adjacent protrusions can be roughly equal, and a certain difference is allowed, as long as the difference is within the allowable error range. The specific spacing length can be in the range of 1.8 to 2.2 mm, for example, 1.8 mm, 2.0 mm, 2.2 mm, etc., and this application does not impose any restrictions on this. In addition, the area increase of each protrusion 31 can be equal or unequal, and this application does not impose any restrictions on this. The specific increase can be set according to parameters such as the frequency of the signal actually to be transmitted.

[0068] In one specific embodiment of the present application, the shape of the protrusion 31 can be rectangular. In this case, the area of ​​the protrusion 31 can be changed by changing the length of the protrusion 31 in a second direction (i.e., the y-direction) perpendicular to the first direction, i.e., the extension length of the protrusion 31. Optionally, in the second section L2, the extension length of the protrusion 31 can be specifically 0.8 mm. Of course, in other embodiments of the present application, the shape of the protrusion 31 can also be an arc, a triangle, or any other arbitrary polygon, and this application does not impose specific limitations on this.

[0069] The specific structural form of the first metal strip 20 and the third metal strip 50 is not limited. It is understood that, along the first direction, if the thickness of the first metal strip 20 and the third metal strip 50 remains unchanged, the cross-sectional area of ​​the first metal strip 20 and the third metal strip 50 can be determined by their widths in the first direction. Therefore, by reducing the widths of the first metal strip 20 and the third metal strip 50, their cross-sectional areas can be reduced. In specific implementations, the widths of the first metal strip 20 and the third metal strip 50 can be reduced in various ways, including but not limited to linear reduction, arc-shaped reduction, or step-shaped reduction. Furthermore, the shapes of the first metal strip 20 and the third metal strip 50 can be the same or different, and this application does not impose any restrictions thereon, as long as both can achieve a trend of gradually decreasing cross-sectional areas. It should be noted that when the first metal strip 20 and the third metal strip 50 have the same shape, the vertical projection of the first metal strip 20 on the second dielectric substrate can overlap with that of the third metal strip 50.

[0070] The following takes the case where the protrusions 31 are provided on both the left and right sides of the second metal strip 30 as an example to illustrate the specific structures of the first metal strip 20 and the third metal strip 50 when adopting several different reduction forms.

[0071] Please refer to FIG. 6 and FIG. 11 . FIG. 11 is a top view of the SSPP transmission line structure shown in FIG. 6 . In this embodiment, the first metal strip 20 may include a first end and a second end positioned opposite to each other. A first notch 21 may be provided at the second end of the first metal strip 20. The first notch 21 extends toward the first end of the first metal strip 20 (i.e., extends toward the −x direction), and the width of the first notch 21 gradually decreases to zero along its extension direction. In this way, the first notch 21 can divide the first metal strip 20 into a first branch 22 and a second branch 23. Accordingly, along the first direction, the widths of the first branch 22 and the second branch 23 gradually decrease until they decrease to zero at the second end of the first metal strip 20. Similarly, the third metal strip may also include a first end and a second end positioned opposite to each other. A second notch may be provided at the second end of the third metal strip. The second notch extends toward the first end of the third metal strip, and the width of the second notch gradually decreases to zero along its extension direction. In this way, the second notch can divide the third metal strip into a third branch and a fourth branch. Accordingly, along the first direction, the widths of the third branch and the fourth branch gradually decrease until they decrease to zero at the second end of the third metal strip. As the first and third metal strips gradually change and disappear, the signal energy originally distributed between the first and second metal strips, and between the second and third metal strips, is gradually coupled to the second metal strip, so that the second metal strip eventually forms an SSPP transmission line with a single-layer metal structure.

[0072] In an embodiment of the present application, the width d0 of the second metal strip can be in the range of 0.25mm to 0.35mm. For example, d0 can be 0.25mm, 0.3mm, 0.35mm, etc.; the initial width w1 of the first metal strip 20 (i.e., the width of the first end of the first metal strip) can be in the range of 2.9mm to 3.1mm. For example, w1 can be 2.9mm, 3.0mm, 3.1mm, etc.; the length l1 of the first branch 22 and the second branch 23 can be in the range of 15mm to 17mm. For example, l1 can be 15mm, 16mm, 17mm, etc.; the size setting of the third metal strip is similar to the size setting of the first metal strip 20, and will not be repeated here.

[0073] Please refer to Figure 12, which shows the S-parameter simulation results for the SSPP transmission line structure docking model shown in Figure 6 within the 5 GHz to 30 GHz frequency band. The dashed curve S11 represents the reflection coefficient, and the solid curve S21 represents the transmission coefficient. It can be seen that this SSPP transmission line structure exhibits the S-parameter regularity characteristic of SSPP transmission lines and exhibits high transmission efficiency.

[0074] Referring to Figures 13 and 14 , Figure 13 is a schematic diagram of another SSPP transmission line structure provided in an embodiment of the present application, and Figure 14 is a top view of the SSPP transmission line structure shown in Figure 13 . In this embodiment, the two sides of the first metal strip 20 and the two sides of the third metal strip gradually approach each other until they intersect, thereby achieving a gradual reduction in width. Specifically, the width of the first metal strip 20 can be gradually reduced in a step-like manner, and similarly, the width of the third metal strip can also be reduced in a step-like manner. As the first metal strip 20 and the third metal strip gradually change and disappear, the signal energy originally distributed between the first metal strip 20 and the second metal strip, and between the second metal strip and the third metal strip, is gradually coupled to the second metal strip, so that the second metal strip is ultimately formed into an SSPP transmission line having a single-layer metal structure.

[0075] In specific implementation, the width d0 of the second metal strip can be in the range of 0.05mm to 0.15mm. For example, d0 can be 0.05mm, 0.1mm, 0.15mm, etc.; the initial width w1 of the first metal strip 20 can be in the range of 2.7mm to 2.9mm. For example, w1 can be 2.7mm, 2.8mm, 2.9mm, etc.; the length l2 of each step of the first metal strip 20 can be in the range of 2.5mm to 3.5mm. For example, l2 can be 2.5mm, 3.0mm, 3.5mm, etc.; the width difference between adjacent steps on the first metal strip 20 can be in the range of 0.25mm to 0.35mm. For example, the width difference can be 0.25mm, 0.3mm, 0.35mm, etc.; the size setting of the third metal strip is similar to the size setting of the first metal strip 20, and will not be repeated here.

[0076] It has been verified that the SSPP transmission line structure shown in FIG13 can achieve a working effect similar to that of the SSPP transmission line structure shown in FIG6 .

[0077] Referring to Figures 15 and 16 , Figure 15 is a schematic diagram of another SSPP transmission line structure provided in an embodiment of the present application, and Figure 16 is a top view of the SSPP transmission line structure shown in Figure 15 . In this embodiment, the two sides of the first metal strip 20 and the two sides of the third metal strip gradually converge until they intersect, thereby achieving a gradual decrease in width. Specifically, the width of the first metal strip 20 can decrease linearly. That is, in the width gradient section L3 of the first metal strip 20, the vertical projection of the side surface of the first metal strip 20 on the first dielectric substrate 10 can be a straight line. Similarly, the width of the third metal strip can also decrease linearly. As the first and third metal strips gradually disappear, the signal energy originally distributed between the first metal strip 20 and the second metal strip, and between the second and third metal strips, is gradually coupled to the second metal strip, ultimately forming the second metal strip into an SSPP transmission line with a single-layer metal structure.

[0078] It should be noted that the width gradient section L3 of the first metal strip 20 can be understood as a section on the first metal strip 20 where the width gradually changes. The width gradient section L3 can be the entire first metal strip 20, or it can be a section on the first metal strip 20 close to its second end. This application does not impose any restrictions on this.

[0079] In specific implementation, the width d0 of the second metal strip can be in the range of 0.05mm to 0.15mm. For example, d0 can be 0.05mm, 0.1mm, 0.15mm, etc.; the initial width w1 of the first metal strip 30 can be in the range of 2.7mm to 2.9mm. For example, w1 can be 2.7mm, 2.8mm, 2.9mm, etc.; the length of the width gradient section L3 of the first metal strip 20 can be in the range of 14mm to 16mm. For example, the length of the width gradient section L3 of the first metal strip 20 can be 14mm, 15mm, 16mm, etc.; the size setting of the third metal strip is similar to the size setting of the first metal strip 20, and will not be repeated here.

[0080] It has been verified that the SSPP transmission line structure shown in FIG15 can achieve a working effect similar to that of the SSPP transmission line structure shown in FIG6 .

[0081] Referring to Figures 17 and 18 , Figure 17 is a schematic diagram of another SSPP transmission line structure provided in an embodiment of the present application, and Figure 18 is a top view of the SSPP transmission line structure shown in Figure 17 . In this embodiment, the sides of the first metal strip 20 and the sides of the third metal strip gradually converge until they intersect, thereby achieving a gradual decrease in width. Specifically, in the width gradient section L3 of the first metal strip 10, the side surfaces of the first metal strip 10 are curved surfaces. That is, the vertical projection of the side surfaces of the first metal strip 10 on the first dielectric substrate 10 is an arc. Similarly, the side surfaces of the width gradient section of the third metal strip can also be curved surfaces. As the first and third metal strips 20 and 3rd metal strips gradually disappear, the signal energy originally distributed between the first metal strip 20 and the second metal strip, and between the second and third metal strips, is gradually coupled to the second metal strip, ultimately forming the second metal strip into an SSPP transmission line with a single-layer metal structure.

[0082] In specific implementation, the width d0 of the second metal strip can be in the range of 0.05mm to 0.15mm. For example, d0 can be 0.05mm, 0.1mm, 0.15mm, etc.; the initial width w1 of the first metal strip can be in the range of 2.7mm to 2.9mm. For example, w1 can be 2.7mm, 2.8mm, 2.9mm, etc.; the length of the width gradient section L3 of the first metal strip 20 can be in the range of 14mm to 16mm. For example, the length of the width gradient section L3 of the first metal strip 20 can be 14mm, 15mm, 16mm, etc.; the size setting of the third metal strip is similar to the size setting of the first metal strip 20, and will not be repeated here.

[0083] It has been verified that the SSPP transmission line structure shown in FIG17 can achieve a working effect similar to that of the SSPP transmission line structure shown in FIG1 .

[0084] It is also worth mentioning that in the above-mentioned embodiments, the number of multiple protrusions on both sides of the second metal strip can be the same or different, and this application does not impose specific restrictions on this. When the number of multiple protrusions on both sides of the first metal strip is equal, the positions of the multiple protrusions on both sides can be opposite to each other or staggered. Referring to Figure 19, when the multiple protrusions 31 on both sides are staggered, the distance between any protrusion 31 on one side and its two adjacent protrusions 31 on the other side along the first direction can be equal.

[0085] The above are several possible structural forms of the SSPP transmission line structure when the second metal strip has protrusions on both the left and right sides. It should be noted that in other embodiments of the present application, when the second metal strip has protrusions only on the left or right side, the SSPP transmission line structure can also employ first and third metal strips having the various gradient forms described above. The details are not further elaborated here. Furthermore, within the same SSPP transmission line structure, the gradient forms of the first and third metal strips can be the same or different, and this application does not impose any restrictions on this.

[0086] With reference to Figures 20, 21, and 22, Figure 15 is a schematic structural diagram of another SSPP transmission line structure provided in an embodiment of the present application, Figure 21 is a bottom view of the first dielectric substrate in Figure 20, and Figure 22 is a top view of the SSPP transmission line structure shown in Figure 20. In this embodiment, a second metal strip 30 is provided with a plurality of protrusions 31 on one side thereof. The first metal strip 20 may include a first side 24 and a second side 25 that are positioned opposite each other. The first side 24 may be the same side as the protrusion 31 on the second metal strip 30. In the width gradient section of the first metal strip 20, the second side 25 of the first metal strip 20 gradually tilts toward the first side 24 until it intersects with the first side 24, thereby gradually decreasing in width. Similarly, the third metal strip may also include a first side and a second side that are positioned opposite each other. In the width gradient section of the third metal strip, the second side of the third metal strip gradually tilts toward the first side until it intersects with the first side, thereby gradually decreasing in width. As the first metal strip 20 and the third metal strip gradually change and disappear, the signal energy originally distributed between the first metal strip 20 and the second metal strip 30, and between the second metal strip 30 and the third metal strip, is gradually coupled to the second metal strip 30, so that the second metal strip 30 is finally formed into an SSPP transmission line with a single-layer metal structure.

[0087] In specific implementation, the width d0 of the second metal strip 30 can be in the range of 0.15mm to 0.25mm. For example, d0 can be 0.15mm, 0.2mm, 0.25mm, etc.; the initial width w1 of the first metal strip 20 can be in the range of 1.3mm to 1.5mm. For example, w1 can be 1.3mm, 1.4mm, 1.5mm, etc.; the length of the width gradient section L3 of the first metal strip 20 can be in the range of 12mm to 14mm. For example, the length of the width gradient section L3 of the first metal strip 20 can be 12mm, 13mm, 14mm, etc.; the size setting of the third metal strip is similar to the size setting of the first metal strip 20, and will not be repeated here.

[0088] It has been verified that the SSPP transmission line structure shown in FIG20 can achieve a working effect similar to that of the SSPP transmission line structure shown in FIG1 .

[0089] It should be understood that in the embodiments of the present application, the gradient form of the first metal strip and the third metal strip is not limited to the methods described in the above embodiments. For example, in some other embodiments, the two sides of the first metal strip and the third metal strip can also be non-linear or non-arc shapes, such as sawtooth or wavy. In this case, the two sides of the first metal strip and the third metal strip can be sawtooth or wavy and gradually approach each other.

[0090] In summary, the SSPP transmission line structure provided in the embodiment of the present application can couple the signal energy in the vertical direction through the spatially stacked first metal strip and the second metal strip, and finally concentrate the signal energy on the second metal strip, so that the second metal strip is formed into an SSPP transmission line. Compared with the method of using coplanar waveguides to couple energy in the horizontal direction in the prior art, this solution can reduce the width of the SSPP transmission line structure, thereby reducing the occupied circuit space.

[0091] The present application also provides a circuit board that may include the SSPP transmission line structure described in any of the aforementioned possible embodiments. In a transmission line interconnection scenario within a microwave circuit constructed of a multilayer board, the SSPP transmission line structure 100 can be used for transmission line conversion within the board to simplify the circuit structure. For example, as shown in FIG23 , for a multilayer board with a complex circuit structure and long transmission distances, the SSPP transmission line structure 100 can couple a shielded stripline with the artificial surface plasmon transmission line structure to achieve single-layer transmission, further simplifying the circuit board structure. Furthermore, because the SSPP transmission line has a relatively large phase velocity, this conversion method can also shorten the length of the phase delay line, thereby making the overall circuit structure more compact.

[0092] The circuit board may also include an interface, which can be a coaxial connector connected to a coaxial transmission line external to the circuit board. The SSPP transmission line structure can be coupled to the connector to convert the coaxial transmission line into an SSPP transmission line on the circuit board. In a specific implementation, the first metal strip of the transmission line structure can be coupled to the outer conductor of the coaxial transmission line via the interface, and the second metal strip can be coupled to the inner conductor of the coaxial transmission line via the interface. This allows the signal from the coaxial transmission line to be transmitted to the SSPP transmission line structure. The SSPP transmission line structure then converts the signal energy into the second metal strip, ultimately forming a single-layer metal structure SSPP transmission line on the circuit board.

[0093] Referring to Figure 24, an embodiment of the present application further provides an electronic device 200, which may include the circuit board 300 in the aforementioned embodiment. The SSPP transmission line structure on the circuit board 300 can be used to convert the coaxial transmission line 400 outside the electronic device 200 into the SSPP transmission line on the circuit board 300. For example, when the SSPP transmission line is used to transmit microwave signals, the SSPP transmission line structure can be used to convert the external coaxial transmission line into the SSPP transmission line on the circuit board 300 through the interface 310 to input the microwave signal. The SSPP transmission line can continue to transmit the microwave signal to the back end of the electronic device 200, such as to the signal processing module or antenna of the electronic device 200; or, when the electronic device 200 outputs a microwave signal, the SSPP transmission line structure can also be used to couple the SSPP transmission line on the circuit board 300 with the interface 310, and then transmit it to other electronic devices through the coaxial transmission line 400 connected to the interface.

[0094] The above are only specific embodiments of the present application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. An artificial surface plasmon transmission line structure, characterized in that: The invention comprises a first dielectric substrate and a first metal strip and a second metal strip, wherein: The first metal strip and the second metal strip are respectively arranged on two opposite surfaces of the first dielectric substrate, and the first metal strip and the second metal strip respectively extend along a first direction, and the length of the first metal strip along the first direction is shorter than the length of the second metal strip along the first direction; Along the first direction, the cross-sectional area of ​​the first metal strip gradually decreases, and at least one side of the second metal strip has a plurality of protrusions arranged at intervals.

2. The artificial surface plasmon transmission line structure according to claim 1, wherein: The device further comprises a second dielectric substrate and a third metal strip, wherein the second dielectric substrate is stacked on a side of the first dielectric substrate on which the second metal strip is disposed, and the third metal strip is disposed on a side of the second dielectric substrate facing away from the first dielectric substrate; The third metal strip extends along the first direction, and the length of the third metal strip along the first direction is less than the length of the second metal strip along the first direction; and the cross-sectional area of ​​the third metal strip gradually decreases along the first direction.

3. The artificial surface plasmon transmission line structure according to claim 1, wherein: Along the first direction, the second metal strip includes a first section and a second section, the area of ​​the protrusion arranged in the first section gradually increases to a set value, the area of ​​the protrusion arranged in the second section is equal and both are the set value, and the second section forms an artificial surface plasmon transmission line with a single-layer metal structure.

4. The artificial surface plasmon transmission line structure according to claim 2 or 3, wherein: The plurality of protrusions located on the same side of the second metal strip are arranged at equal intervals.

5. The artificial surface plasmon transmission line structure according to any one of claims 2 to 4, characterized in that: The protrusions are respectively provided on both sides of the second metal strip.

6. The artificial surface plasmon transmission line structure according to claim 5, wherein: Along the first direction, the first metal strip and the third metal strip have a first end and a second end respectively; A first notch is formed at the second end of the first metal strip, the first notch dividing the first metal strip into a first branch and a second branch, and the widths of the first branch and the second branch gradually decrease along the first direction; A second notch is formed at the second end of the third metal strip, and the second notch divides the third metal strip into a third branch and a fourth branch. The widths of the third branch and the fourth branch gradually decrease along the first direction.

7. The artificial surface plasmon transmission line structure according to claim 5, wherein: Along the first direction, two side surfaces of the first metal strip gradually approach and intersect; and / or two side surfaces of the third metal strip gradually approach and intersect.

8. The artificial surface plasmon transmission line structure according to claim 7, wherein: Along the first direction, the width of the first metal strip gradually decreases in a step-like manner; or, the width of the first metal strip decreases linearly; or, the side surface of the first metal strip includes an arc-shaped surface; and / or, Along the first direction, the width of the third metal strip gradually decreases in a step-like manner; or, the width of the third metal strip decreases linearly; or, the side surface of the third metal strip includes an arc-shaped surface.

9. The artificial surface plasmon transmission line structure according to any one of claims 5 to 8, wherein: The positions of the multiple protrusions on both sides of the second metal strip are opposite to each other; or the positions of the multiple protrusions on both sides of the second metal strip are staggered.

10. The artificial surface plasmon transmission line structure according to any one of claims 2 to 4, characterized in that: The first metal strip and the third metal strip respectively include a first side and a second side, the first side being the same side as the protruding side, and the protruding side being the side of the second metal strip on which the protruding portion is provided; The second side of the first metal strip gradually tilts toward the first side of the first metal strip and intersects with the second side of the first metal strip; and the second side of the third metal strip gradually tilts toward the first side of the third metal strip and intersects with the second side of the third metal strip.

11. The artificial surface plasmon transmission line structure according to any one of claims 2 to 10, characterized in that: A vertical projection of the first metal strip on the second dielectric substrate overlaps with the third metal strip.

12. The artificial surface plasmon transmission line structure according to any one of claims 2 to 11, characterized in that: The first metal strip is attached to the surface of the first dielectric substrate; or the first metal strip is embedded in the surface of the first dielectric substrate.

13. The artificial surface plasmon transmission line structure according to any one of claims 2 to 12, characterized in that: The second metal strip is attached between the first dielectric substrate and the second dielectric substrate; or, the second metal strip is embedded in the surface of the first dielectric substrate and / or the surface of the second dielectric substrate.

14. The artificial surface plasmon transmission line structure according to any one of claims 2 to 13, wherein: The third metal strip is attached to the surface of the second dielectric substrate; or, the third metal strip is embedded in the surface of the second dielectric substrate.

15. A circuit board, characterized in that: It comprises the artificial surface plasmon transmission line structure according to any one of claims 1 to 14.

16. The circuit board according to claim 15, wherein: The circuit board further includes an interface coupled to the artificial surface plasmon transmission line structure.

17. The circuit board according to claim 16, wherein: The interface is connected to a coaxial transmission line outside the circuit board.

18. The circuit board according to claim 17, wherein: The first metal strip of the transmission structure is coupled and connected to the outer conductor of the coaxial transmission line through the interface, and the second metal strip of the transmission structure is coupled and connected to the second conductor of the coaxial transmission line through the interface.

19. An electronic device, characterized in that: The circuit board comprises the circuit board according to any one of claims 15 to 18.

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