Conversion circuit and circuit board

Abstract

To improve the transmission characteristics of the conversion circuit between coaxial connectors and microstrip lines. [Solution] The conversion circuit comprises a coaxial connector and a circuit board. The coaxial connector has a core wire, and the circuit board has a first conductor surrounding the core wire and electrically connected to the core wire, a second conductor electrically connected to the first conductor and extending toward the side away from the first conductor, and a ground conductor that at least partially overlaps the second conductor, wherein the ground conductor defines an opening that at least partially overlaps the first conductor, and the edge of the opening of the ground conductor includes a first portion surrounding the core wire except on the side where the second conductor is located, and a second portion that extends further inward from the side where the second conductor is located toward the side where the core wire is located than the first portion.

Description

Technical Field

[0001] The present invention relates to a conversion circuit and a circuit board.

Background Art

[0002] In recent years, various conversion circuits for converting transmission signals between coaxial connectors and microstrip lines have been developed.

[0003] Patent Document 1 describes a vertical printed circuit board (PCB) coaxial connector connected to a microstrip line. A printed wiring board (PWB) having a microstrip line has a ground, four plating holes connected to the coaxial connector, and six vias.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0007] One aspect of the present invention is, A coaxial connector having a core wire, A substrate having a first conductor surrounding the core wire and electrically connected to the core wire, a second conductor electrically connected to the first conductor and extending toward the side away from the first conductor, and a ground conductor that at least partially overlaps the second conductor, Equipped with, The ground conductor defines an opening that at least partially overlaps with the first conductor. The edge of the opening of the ground conductor is a conversion circuit that includes a first portion surrounding the core wire except on the side where the second conductor is located, and a second portion extending further inward from the side where the second conductor is located to the side where the core wire is located than the first portion.

[0008] One aspect of the present invention is, A first conductor surrounds the core wire of a coaxial connector and is electrically connected to the core wire, A second conductor electrically connected to the first conductor and extending toward the side away from the first conductor, A ground conductor that at least partially overlaps the second conductor, Equipped with, The ground conductor defines an opening that at least partially overlaps with the first conductor. The edge of the opening of the ground conductor is a circuit board having a first portion that surrounds the core wire except on the side where the second conductor of the core wire is located, and a second portion that extends further inward from the side where the second conductor of the core wire is located towards the side where the core wire is located than the first portion.

[0009] According to the above-described embodiment of the present invention, the transmission characteristics of the conversion circuit between the coaxial connector and the microstrip line can be improved. [Brief explanation of the drawing]

[0010] [Figure 1] This is an exploded perspective view of the conversion circuit according to the embodiment. [Figure 2]This is a plan view of the core wire, central land, tapered conductor, line conductor, four peripheral lands, and ground conductor according to the embodiment. [Figure 3] This is a plan view of the core wire and ground conductor according to the embodiment. [Figure 4] This is a plan view of the core wire, central land, tapered conductor, line conductor, peripheral conductor, and ground conductor according to an embodiment of a comparative example. [Figure 5] This is a plan view of the core wire and ground conductor in the comparative example. [Figure 6] This graph shows the TDR (Time Domain Reflectometry) characteristics of the conversion circuit according to the embodiment and the conversion circuit according to the comparative example. [Figure 7] This graph shows the frequency characteristics of the insertion loss of the conversion circuit according to the embodiment and the conversion circuit according to the comparative example. [Figure 8] This graph shows the frequency characteristics of the reflection loss of the conversion circuit according to the embodiment and the conversion circuit according to the comparative example. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below with reference to the drawings. In all drawings, similar components are denoted by the same reference numerals, and their descriptions are omitted where appropriate.

[0012] Figure 1 is an exploded perspective view of the conversion circuit 1 according to the embodiment. Figure 2 is a plan view of the core wire 13, central land 32, tapered conductor 33, line conductor 34, four peripheral lands 35, and ground conductor 36 according to the embodiment. Figure 3 is a plan view of the core wire 13 and ground conductor 36 according to the embodiment.

[0013] In FIGS. 1 to 3, for the purpose of explanation, the X-axis, Y-axis, and Z-axis indicating the X direction, Y direction, and Z direction, respectively, are shown. In FIGS. 2 and 3, the white circle with a black dot indicating the Z-axis indicates that the arrow of the Z-axis points toward the front of the paper surface. The Z direction is a direction parallel to the arrangement direction of the coaxial connector 10, the holder 20, and the substrate 30, which will be described later. The X direction is one of the directions perpendicular to the Z direction. The Y direction is one of the directions perpendicular to the Z direction and the X direction. Hereinafter, unless otherwise specified, the +X side refers to the side indicated by the arrow of the X-axis, and the -X side refers to the opposite side of the side indicated by the arrow of the X-axis. Hereinafter, unless otherwise specified, the +Y side refers to the side indicated by the arrow of the Y-axis, and the -Y side refers to the opposite side of the side indicated by the arrow of the Y-axis. Hereinafter, unless otherwise specified, the +Z side refers to the side indicated by the arrow of the Z-axis, and the -Z side refers to the opposite side of the side indicated by the arrow of the Z-axis. Hereinafter, the surface located on the +Z side of a certain element may be referred to as the +Z surface of the element, and the surface located on the -Z side of a certain element may be referred to as the -Z surface of the element.

[0014] Mainly referring to FIG. 1, the conversion circuit 1 according to the embodiment will be described. If necessary, FIGS. 2 and 3 will be referred to.

[0015] As shown in FIG. 1, the conversion circuit 1 according to the embodiment includes a coaxial connector 10, a holder 20, and a substrate 30.

[0016] The coaxial connector 10 is an SMA (Sub Miniature type A) connector. The coaxial connector 10 may be a connector of a type different from the SMA connector. As shown in FIG. 1, the coaxial connector 10 has a housing 11, a flange 12, a core wire 13, an insulator 14, and four posts 15.

[0017] The housing 11 is made of a conductor such as metal. The housing 11 has a substantially cylindrical shape. The outer peripheral surface of the housing 11 around the Z direction defines a thread for joining with a coaxial cable not shown. The housing 11 may not define this thread.

[0018] The flange 12 is made of a conductor such as metal. The +Z end of the housing 11 and the -Z surface of the flange 12 are electrically connected to each other. In this embodiment, the housing 11 and the flange 12 are integrated. As shown in Figure 1, when viewed from the +Z side, the flange 12 has a substantially square shape with a pair of sides substantially parallel to the X direction and a pair of sides substantially parallel to the Y direction. When viewed from the +Z side, the lengths of the flange 12 in the X and Y directions are longer than the diameter of the housing 11 in the direction perpendicular to the Z direction. The shape of the flange 12 is not limited to the example shown in Figure 1. For example, when viewed from the +Z side, the flange 12 may have a substantially rectangular or substantially circular shape.

[0019] The core wire 13 is made of a conductor such as metal. As shown in Figure 1, the core wire 13 extends in the Z direction. Viewed from the +Z side, the core wire 13 is located approximately in the center of the housing 11 and flange 12. The +Z end of the core wire 13 protrudes from the +Z surface of the flange 12 toward the +Z side. The portion of the core wire 13 located inside the housing 11 and flange 12 is covered by an insulator 14 embedded in the housing 11 and flange 12. Therefore, the conductor constituting the core wire 13 and the conductor constituting the housing 11 and flange 12 are electrically insulated from each other by the insulator 14.

[0020] Each post 15 is made of a conductor such as metal. As shown in Figure 1, when viewed from the +Z side, the four posts 15 protrude to the +Z side from the four corners of the +Z surface of the flange 12. The +Z surface of the flange 12 and the -Z ends of the four posts 15 are electrically connected to each other. In this embodiment, the flange 12 and the four posts 15 are integrated.

[0021] The holder 20 is made of an insulator such as glass epoxy. The holder 20 may also be made of metal. As shown in Figure 1, the holder 20 has a substantially plate shape that is substantially perpendicular to the Z direction.

[0022] As shown in Figure 1, the holder 20 defines a central insertion hole 21 and four peripheral insertion holes 22 located around the central insertion hole 21 in the Z direction. The central insertion hole 21 and the four peripheral insertion holes 22 penetrate the holder 20 in the Z direction. As can be seen from Figure 1, when the coaxial connector 10 and the holder 20 are assembled together, the core wire 13 is inserted through the central insertion hole 21, and the four posts 15 are inserted through the four peripheral insertion holes 22. The coaxial connector 10 is held by the holder 20 when the four posts 15 are inserted through the four peripheral insertion holes 22.

[0023] As shown in Figure 1, a conductive layer 23 is formed on the +Z plane of the holder 20, the inner surface around the Z direction of the central insertion hole 21, and the inner surface around the Z direction of the four peripheral insertion holes 22. The conductive layer 23 is also formed on the -Z plane side of the holder 20. The conductive layer 23 is, for example, a metal layer. In the example shown in Figure 1, the conductive layer 23 formed on the +Z plane side of the holder 20 has a roughly rectangular shape centered on the central insertion hole 21, with a pair of sides that are roughly parallel to the X direction and a pair of sides that are roughly parallel to the Y direction. When viewed from the +Z side, the four peripheral insertion holes 22 are located at the four corners of the conductive layer 23.

[0024] The substrate 30 is a circuit board. In this embodiment, the substrate 30 is a flexible substrate such as an FPC (Flexible Printed Circuits). The substrate 30 may also be a rigid substrate such as a PCB (Printed Circuit Board). As shown in Figure 1, the substrate 30 has a film 31, a central land 32, a tapered conductor 33, a line conductor 34, four peripheral lands 35, and a ground conductor 36.

[0025] The film 31 is made of a resin such as polyimide. As shown in Figure 1, the film 31 is in a substantially sheet shape extending in a direction substantially perpendicular to the Z direction. The film 31 is flexible. Therefore, the film 31 can be deformed with a relatively high degree of freedom. The film 31 defines a central through hole 311 and four peripheral through holes 312 located around the central through hole 311 in the Z direction. The central through hole 311 and the four peripheral through holes 312 penetrate the film 31 in the Z direction. The central insertion hole 21 and the central through hole 311 overlap at least partially in the Z direction. The four peripheral insertion holes 22 and the four peripheral through holes 312 overlap at least partially in the Z direction.

[0026] As shown in Figure 1, the central land 32, tapered conductor 33, and line conductor 34 are conductors provided on the +Z side of the film 31. The central land 32, tapered conductor 33, and line conductor 34 are, for example, metal layers formed on the +Z side of the film 31. In this embodiment, the central land 32, tapered conductor 33, and line conductor 34 are integrated.

[0027] As shown in Figure 1, the central through-hole 311 and the central land 32 overlap at least partially in the Z direction. As can be seen from Figure 1, when the coaxial connector 10, the holder 20, and the substrate 30 are assembled together, the central land 32 has a surrounding shape that encloses the +Z end of the core wire 13 around the Z direction, as viewed from the +Z side. In the example shown in Figure 1, the central land 32 has a roughly ring-shaped form that encloses the +Z end of the core wire 13 around the Z direction, as viewed from the +Z side. Hereafter, unless otherwise specified, the hole in the central land 32 refers to the hole surrounded by the inner circumference of the central land 32 around the Z direction.

[0028] As shown in Figures 1 and 2, the line conductor 34 extends in the X direction toward the +X side away from the central land 32, with tapered conductors 33 positioned at the +X end of the central land 32 and the -X end of the line conductor 34. The +X end of the central land 32 and the -X end of the tapered conductor 33 are electrically connected to each other. The +X end of the tapered conductor 33 and the -X end of the line conductor 34 are electrically connected to each other. Therefore, the central land 32 and the line conductor 34 are electrically connected to each other via the tapered conductor 33. The width of the tapered conductor 33 in the Y direction decreases continuously as it moves from the central land 32 toward the line conductor 34. The width of the line conductor 34 in the Y direction is approximately constant regardless of its position in the X direction.

[0029] In this embodiment, as shown in Figure 2, the +X end of the central land 32 and the -X end of the line conductor 34 are connected via a tapered conductor 33. Therefore, compared to the case where the +X end of the central land 32 and the -X end of the line conductor 34 are directly connected without the tapered conductor 33, the change in the Y-direction width of the conductors constituting the central land 32 and the line conductor 34 between the +X end of the central land 32 and the -X end of the line conductor 34 can be made more gradual. Therefore, compared to the case where the change in the Y-direction width of the conductors constituting the central land 32 and the line conductor 34 between the +X end of the central land 32 and the -X end of the line conductor 34 is steep, disconnection of the conductors constituting the central land 32 and the line conductor 34 between the +X end of the central land 32 and the -X end of the line conductor 34 can be suppressed. The +X end of the central land 32 and the -X end of the line conductor 34 may be directly connected without the tapered conductor 33.

[0030] As shown in Figure 1, the four peripheral lands 35 are conductors provided on the +Z side of the film 31. The four peripheral lands 35 are, for example, metal layers formed on the +Z side of the film 31. The four peripheral through holes 312 and the four peripheral lands 35 overlap at least partially in the Z direction. As can be seen from Figure 1, when the coaxial connector 10, the holder 20 and the substrate 30 are assembled together, the four peripheral lands 35 form a surrounding shape that encloses the +Z side ends of the four posts 15 around the Z direction, as viewed from the +Z side. In the example shown in Figure 1, the four peripheral lands 35 form a roughly annular shape that encloses the +Z side ends of the four posts 15 around the Z direction, as viewed from the +Z side. Hereafter, unless otherwise specified, the hole in the peripheral land 35 refers to the hole surrounded by the inner circumference of the peripheral land 35 around the Z direction.

[0031] As shown in Figure 1, the ground conductor 36 is a conductor provided on the -Z plane side of the film 31. The ground conductor 36 is, for example, a metal layer formed on the -Z plane side of the film 31. The ground conductor 36 defines a central opening 361 and four peripheral openings 362 located around the central opening 361 in the Z direction. The central insertion hole 21, the central through hole 311, and the central opening 361 overlap at least partially in the Z direction. The four peripheral insertion holes 22, the four peripheral through holes 312, and the four peripheral openings 362 overlap at least partially in the Z direction.

[0032] The line conductor 34 and the ground conductor 36 constitute a microstrip line. Specifically, in the example shown in Figure 1, the ground conductor 36 is located on substantially the entire -Z plane of the film 31, except for the central opening 361 and the four peripheral openings 362. Therefore, the line conductor 34 and the ground conductor 36 overlap each other at least partially in the Z direction. By adjusting conditions such as the width of the line conductor 34 in the Y direction, the thickness of the line conductor 34 in the Z direction, and the distance in the Z direction between the -Z plane of the line conductor 34 and the +Z plane of the ground conductor 36, the line conductor 34 and the ground conductor 36 can constitute a microstrip line with a predetermined characteristic impedance. The conversion circuit 1 is configured to convert the transmission signal between the coaxial connector 10 and the microstrip line composed of the line conductor 34 and the ground conductor 36.

[0033] As can be seen in Figure 1, when the coaxial connector 10, the holder 20, and the substrate 30 are assembled together, the four posts 15 pass through the holes of the four peripheral insertion holes 22, the four peripheral openings 362, the four peripheral through holes 312, and the four peripheral lands 35 in the Z direction. The +Z end of each post 15 and each peripheral land 35 are joined to each other, for example, by soldering. The solder that joins the +Z end of each post 15 and each peripheral land 35 also enters the gap between the outer surface of each post 15 around the Z direction and the inner surface of each peripheral opening 362 around the Z direction. Furthermore, when the holder 20 and the substrate 30 are stacked on top of each other in the Z direction, the +Z surface of the conductor layer 23 located on the +Z side of the holder 20 and the -Z surface of the ground conductor 36 are in contact with each other. Therefore, when the +Z end of each post 15 and each surrounding land 35 are joined to each other by soldering, each post 15, conductor layer 23, each surrounding land 35, and ground conductor 36 are electrically connected to each other.

[0034] As can be seen from Figure 1, when the coaxial connector 10, the holder 20, and the substrate 30 are assembled together, the core wire 13 passes through the holes of the central insertion hole 21, the central opening 361, the central through hole 311, and the central land 32 in the Z direction. The core wire 13 is inserted into the central insertion hole 21 with the outer surface of the core wire 13 around the Z direction and the conductor layer 23 formed on the inner surface of the central insertion hole 21 around the Z direction spaced apart from each other. Therefore, the core wire 13 and the conductor layer 23 are not electrically connected. The core wire 13 is inserted into the central opening 361 with the outer surface of the core wire 13 around the Z direction and the curved edge 361a, a pair of straight edges 361b, and a pair of tapered edges 361c of the central opening 361 spaced apart from each other. Therefore, the core wire 13 and the ground conductor 36 are not electrically connected. Details of the curved edge 361a, the pair of straight edges 361b, and the pair of tapered edges 361c will be described later with reference to Figures 2 and 3. The +Z end of the core wire 13 and the central land 32 are joined to each other, for example, by soldering. By joining the +Z end of the core wire 13 and the central land 32 to each other by soldering, the core wire 13 and the central land 32 are electrically connected to each other. Thus, the coaxial connector 10 and the microstrip line, which is composed of the line conductor 34 and the ground conductor 36, can be electrically connected to each other.

[0035] In this embodiment, a coaxial structure is formed by a core wire 13 and a conductor layer 23 formed on the inner surface of the central insertion hole 21 around the Z direction. This coaxial structure can be configured to match the characteristic impedance of the coaxial connector 10 with the characteristic impedance of the microstrip line composed of the line conductor 34 and the ground conductor 36 by adjusting dimensions such as the diameter of the core wire 13 in the direction perpendicular to the Z direction, the diameter of the central insertion hole 21 in the direction perpendicular to the Z direction, and the distance between the outer surface of the core wire 13 around the Z direction and the inner surface of the central insertion hole 21 around the Z direction.

[0036] Next, with reference to Figures 2 and 3, the central opening 361 of the ground conductor 36 according to this embodiment will be described further.

[0037] As shown in Figures 2 and 3, the edges of the central opening 361 around the Z direction include a curved edge 361a, a pair of straight edges 361b, and a pair of tapered edges 361c. As shown in Figure 3, viewed from the +Z side, the central opening 361 has a substantially circular shape with the curved edge 361a as part of the circumference and partially cut out by the pair of straight edges 361b and the pair of tapered edges 361c. In the example shown in Figures 2 and 3, viewed from the +Z side, the central land 32 and the circular shape are substantially concentric in the projection of the central land 32 and the ground conductor 36 onto a plane perpendicular to the Z direction. As can be seen from Figures 2 and 3, viewed from the +Z side, the curved edge 361a surrounds the core wire 13 around the Z direction, except for the +X side where the line conductor 34 of the core wire 13 is located. As can be seen from Figures 2 and 3, when viewed from the +Z side, the pair of straight edges 361b and the pair of tapered edges 361c extend further inward from the +X side where the line conductor 34 of the core wire 13 is located to the -X side where the core wire 13 is located than the curved edge 361a. In the example shown in Figure 3, the pair of straight edges 361b extend in the Y direction from both ends of the curved edge 361a located on either side of the tapered conductor 33 in the Y direction, moving closer to each other. The pair of tapered edges 361c extend in the +X direction from the ends of the pair of straight edges 361b that are opposite each other in the Y direction. The distance in the Y direction between the pair of tapered edges 361c decreases as you move towards the +X side.

[0038] As can be seen from Figures 2 and 3, the Y-edges of the tapered conductor 33 and the pair of tapered edges 361c are arranged at least partially parallel to each other. When viewed from the +Z side, the Y-edges of the tapered conductor 33 and the pair of tapered edges 361c may overlap each other at least partially in the Z direction. Alternatively, when viewed from the +Z side, in the projection of the tapered conductor 33 and the pair of tapered edges 361c onto a plane perpendicular to the Z direction, the Y-edges of the tapered conductor 33 and the pair of tapered edges 361c may be offset from each other.

[0039] Figure 4 is a plan view of the core wire 13, central land 32, tapered conductor 33, line conductor 34, peripheral conductor 37, and ground conductor 36 according to the comparative example embodiment. Figure 5 is a plan view of the core wire 13 and ground conductor 36 according to the comparative example. The conversion circuit 1 according to the comparative example is the same as the conversion circuit 1 according to the embodiment, except for the following points.

[0040] As shown in Figure 4, when viewed from the +Z side, the peripheral conductor 37 of the comparative example has a roughly square shape with rounded corners, having a pair of sides that are roughly parallel to the X direction and a pair of sides that are roughly parallel to the Y direction. As shown in Figure 4, the peripheral conductor 37 defines a notch pattern 371 and four opening patterns 372 located around the notch pattern 371 in the Z direction. As can be seen from Figures 4 and 5, the notch pattern 371 includes a circular pattern 371a that overlaps with the central opening 361 in the Z direction, and a straight line pattern 371b that extends in the X direction between the +X side end of the circular pattern 371a and the approximate center in the Y direction of the +X side of the peripheral conductor 37. The central land 32 and tapered conductor 33 are located within the circular pattern 371a. The line conductor 34 passes through the straight line pattern 371b on the +X side of the central land 32 and tapered conductor 33. As can be seen from Figures 4 and 5, when viewed from the +Z side, the four opening patterns 372 are located at the four corners of the peripheral conductor 37 and overlap with the four peripheral openings 362 in the Z direction.

[0041] As shown in Figure 5, when viewed from the +Z side, the central opening 361 in the comparative example is simply circular in shape. In other words, the central opening 361 in the comparative example does not include edges corresponding to the pair of straight edges 361b and the pair of tapered edges 361c according to the embodiment.

[0042] The conversion circuit 1 according to the embodiment and the conversion circuit 1 according to the comparative example are compared.

[0043] In the comparative example conversion circuit 1, the characteristic impedance of the tapered conductor 33 located at the connection point between the +X end of the central land 32 and the -X end of the line conductor 34 tends to be higher than the characteristic impedance of the coaxial connector 10 and the characteristic impedance of the microstrip line composed of the line conductor 34 and the ground conductor 36. Therefore, in the comparative example conversion circuit 1, it may be difficult to suppress the mismatch in the characteristic impedance of the tapered conductor 33. In the embodiment, the +X side edge of the central opening 361 extends further into the -X side where the core wire 13 is located, due to the pair of straight edges 361b and the pair of tapered edges 361c compared to the comparative example. Therefore, in the embodiment, the tapered conductor 33 and the ground conductor 36 can be brought closer to each other than in the comparative example. Therefore, in the embodiment, the characteristic impedance of the tapered conductor 33 can be reduced compared to the comparative example, and the mismatch in the characteristic impedance of the tapered conductor 33 can be suppressed. Therefore, in the embodiment, the transmission characteristics of the conversion circuit 1 between the coaxial connector 10 and the microstrip line composed of the line conductor 34 and the ground conductor 36 can be improved compared to the comparative example.

[0044] As described above, the characteristic impedance of the tapered conductor 33 can be reduced by having the +X side edge of the central opening 361 extend into the -X side where the core wire 13 is located. However, if the +X side edge of the central opening 361 simply extends into the -X side, the characteristic impedance of the tapered conductor 33 may become too low. In the conversion circuit 1 according to the embodiment, both Y-direction edges of the tapered conductor 33 and the pair of tapered edges 361c are arranged substantially parallel to each other. Therefore, by adjusting the distance between both Y-direction edges of the tapered conductor 33 and the pair of tapered edges 361c to an appropriate distance, the characteristic impedance of the tapered conductor 33 can be adjusted to a value suitable for matching the characteristic impedance of the coaxial connector 10 with the characteristic impedance of the microstrip line composed of the line conductor 34 and the ground conductor 36. Depending on the characteristic impedance of the tapered conductor 33, the +X side edge of the central opening 361 may simply extend into the -X side.

[0045] Figure 6 is a graph showing the TDR (Time Domain Reflectometry) characteristics of the conversion circuit 1 according to the embodiment and the conversion circuit 1 according to the comparative example. The horizontal axis of the graph in Figure 6 represents time (unit: ps). The vertical axis of the graph in Figure 6 represents characteristic impedance Z0 (unit: Ω). In the graph in Figure 6, the impedance of the coaxial cable electrically connected to the coaxial connector 10 is 50Ω.

[0046] The time domain from 0 ps to 250 ps in the graph shown in Figure 6 is divided into the following time domains: 0 ps to approximately 50 ps corresponds to the housing 11 in the embodiment and comparative example. Approximately 50 ps to approximately 85 ps corresponds to the holder 20 in the embodiment and comparative example. Approximately 85 ps to approximately 130 ps corresponds to the tapered conductor 33 in the embodiment and comparative example. Approximately 130 ps to approximately 250 ps corresponds to the line conductor 34 in the embodiment and comparative example.

[0047] As shown in Figure 6, the maximum value of the characteristic impedance Z0 (unit: Ω) at approximately 100 ps is closer to the impedance of the coaxial cable (50 Ω) in this embodiment than in the comparative example. From the results shown in Figure 6, it can be said that the characteristic impedance Z0 of the tapered conductor 33 can be reduced by extending the +X side edge of the central opening 361 inward from the curved edge 361a on the -X side where the core wire 13 is located.

[0048] Figure 7 is a graph showing the frequency characteristics of the insertion loss of the conversion circuit 1 according to the embodiment and the conversion circuit 1 according to the comparative example. The horizontal axis of the graph in Figure 7 represents frequency (unit: GHz). The vertical axis of the graph in Figure 7 represents insertion loss (unit: dB). In the graph in Figure 7, the larger the absolute value of the negative value on the vertical axis, the greater the insertion loss of the conversion circuit 1.

[0049] As shown in Figure 7, in the range of approximately 6 GHz to approximately 20 GHz, the insertion loss in this embodiment is smaller than that of the comparative example. From the results shown in Figure 7, it can be said that by extending the +X side edge of the central opening 361 further into the -X side where the core wire 13 is located than the curved edge 361a, the transmission characteristics of the conversion circuit 1 can be improved over a wide bandwidth.

[0050] Figure 8 is a graph showing the frequency characteristics of the reflection loss of the conversion circuit 1 according to the embodiment and the conversion circuit 1 according to the comparative example. The horizontal axis of the graph in Figure 8 represents frequency (unit: GHz). The vertical axis of the graph in Figure 8 represents reflection loss (unit: dB). In the graph in Figure 8, the larger the absolute value of the negative value on the vertical axis, the smaller the reflection loss of the conversion circuit 1.

[0051] As shown in Figure 8, in the range of approximately 6 GHz to approximately 20 GHz, the reflection loss in this embodiment is smaller than that of the comparative example. From the results shown in Figure 8, it can be said that by extending the +X side edge of the central opening 361 inward from the curved edge 361a on the -X side where the core wire 13 is located, the reflection characteristics of the transmission signal of the conversion circuit 1 can be improved over a wide bandwidth.

[0052] The embodiments of the present invention have been described above with reference to the drawings, but these are merely examples of the present invention, and various other configurations can also be adopted.

[0053] According to this specification, conversion circuits and circuit boards in the following embodiments are provided. (Aspect 1) In embodiment 1, the conversion circuit comprises a coaxial connector and a circuit board. The coaxial connector has a core wire, and the circuit board has a first conductor surrounding the core wire and electrically connected to the core wire, a second conductor electrically connected to the first conductor and extending toward the side away from the first conductor, and a ground conductor that at least partially overlaps the second conductor, wherein the ground conductor defines an opening that at least partially overlaps the first conductor, and the edge of the opening of the ground conductor includes a first portion surrounding the core wire except on the side where the second conductor is located, and a second portion that extends further inward from the side where the second conductor is located toward the side where the core wire is located than the first portion.

[0054] The "first conductor" corresponds to the "central land" in the above-described embodiment. The "second conductor" corresponds to the "track conductor" in the above-described embodiment. The "opening" corresponds to the "central opening" in the above-described embodiment. The "first part" corresponds to the "curved edge" in the above-described embodiment. The "second part" corresponds to the "straight edge" and "tapered edge" in the above-described embodiment.

[0055] According to the above-described embodiment, the connection point between the first and second conductors and the ground conductor can be brought closer to each other compared to the case where the second portion does not extend into the side where the core wire is located. Therefore, the characteristic impedance at the connection point between the first and second conductors can be reduced compared to the case where the second portion does not extend into the side where the core wire is located, and the mismatch in characteristic impedance at the connection point between the first and second conductors can be suppressed. Consequently, the transmission characteristics of the conversion circuit between the coaxial connector and the microstrip line composed of the second conductor and the ground conductor can be improved compared to the case where the second portion does not extend into the side where the core wire is located.

[0056] (Aspect 2) In embodiment 2, the substrate further has a third conductor that electrically connects the first conductor and the second conductor and whose width decreases from the first conductor toward the second conductor, and the edge of the third conductor and the second portion of the edge of the opening are arranged at least partially in parallel.

[0057] The "third conductor" corresponds to the "tapered conductor" in the above-described embodiment. The "second part" corresponds to the "tapered edge" in the above-described embodiment.

[0058] According to the above-described embodiment, by adjusting the distance between the edge of the third conductor and the second portion of the edge of the opening to an appropriate distance, the characteristic impedance of the connection point between the first and second conductors can be adjusted to a value suitable for matching the characteristic impedance of the coaxial connector with the characteristic impedance of the microstrip line formed by the second conductor and the ground conductor.

[0059] (Aspect 3) In embodiment 3, the circuit board comprises a first conductor surrounding the core wire of a coaxial connector and electrically connected to the core wire, a second conductor electrically connected to the first conductor and extending away from the first conductor, and a ground conductor that at least partially overlaps the second conductor, wherein the ground conductor defines an opening that at least partially overlaps the first conductor. The edge of the opening of the ground conductor has a first portion that surrounds the core wire except on the side where the second conductor of the core wire is located, and a second portion that extends further inward from the side where the second conductor of the core wire is located towards the side where the core wire is located than the first portion.

[0060] "Circuit board" corresponds to "substrate" in the above-described embodiment. "First conductor" corresponds to "central land" in the above-described embodiment. "Second conductor" corresponds to "line conductor" in the above-described embodiment. "Opening" corresponds to "central opening" in the above-described embodiment. "First part" corresponds to "curved edge" in the above-described embodiment. "Second part" corresponds to "straight edge" and "tapered edge" in the above-described embodiment.

[0061] According to the above-described embodiment, similar to embodiment 1, the transmission characteristics of the conversion circuit between the coaxial connector and the microstrip line composed of the second conductor and the ground conductor can be improved compared to the case where the second portion does not extend into the side where the core wire is located. [Explanation of symbols]

[0062] 1 Conversion circuit, 10 Coaxial connector, 11 Housing, 12 Flange, 13 Core wire, 14 Insulator, 15 Post, 20 Retainer, 21 Central insertion hole, 22 Peripheral insertion hole, 23 Conductor layer, 30 Substrate, 31 Film, 311 Central through hole, 312 Peripheral through hole, 32 Central land, 33 Tapered conductor, 34 Line conductor, 35 Peripheral land, 36 Ground conductor, 361 Central opening, 361a Curved edge, 361b Straight edge, 361c Tapered edge, 362 Peripheral opening, 37 Peripheral conductor, 371 Notch pattern, 371a Circle pattern, 371b Straight pattern, 372 Opening pattern

Claims

1. A coaxial connector having a core wire, A substrate having a first conductor surrounding the core wire and electrically connected to the core wire, a second conductor electrically connected to the first conductor and extending toward the side away from the first conductor, and a ground conductor that at least partially overlaps the second conductor, Equipped with, The ground conductor defines an opening that at least partially overlaps with the first conductor. A conversion circuit in which the edge of the opening of the ground conductor includes a first portion that surrounds the core wire except on the side where the second conductor of the core wire is located, and a second portion that extends further inward from the side where the second conductor of the core wire is located towards the side where the core wire is located than the first portion.

2. The substrate further comprises a third conductor that electrically connects the first conductor and the second conductor and whose width decreases as it moves from the first conductor to the second conductor. The conversion circuit according to claim 1, wherein the edge of the third conductor and the second portion of the edge of the opening are arranged at least partially substantially parallel to each other.

3. A first conductor surrounds the core wire of a coaxial connector and is electrically connected to the core wire, A second conductor electrically connected to the first conductor and extending toward the side away from the first conductor, A ground conductor that at least partially overlaps the second conductor, Equipped with, The ground conductor defines an opening that at least partially overlaps with the first conductor. A circuit board wherein the edge of the opening of the ground conductor has a first portion that surrounds the core wire except on the side where the second conductor of the core wire is located, and a second portion that extends further inward from the side where the second conductor of the core wire is located towards the side where the core wire is located than the first portion.

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