Transmission line

Abstract

A transmission line comprises: a first transmission line having a signal line conductor; a second transmission line having a signal line conductor formed in a layer different from that of the signal line conductor of the first transmission line; and a connection portion having a connection via for electric interlayer connection of the signal line conductors, wherein the first transmission line is a microstrip line having the signal line conductor and a ground conductor, the second transmission line is a coplanar line having the signal line conductor and two ground conductors formed to sandwich the signal line conductor, and the connection portion includes two ground connection conductors electrically connected to each of the ground conductor of the first transmission line and the two ground conductors of the second transmission line so as to surround a part of at least one of the signal line conductors and the connection via in a plan view.

Description

transmission lines

[0001] This application claims priority to Japanese Patent Application No. 2024-047834, filed on March 25, 2024, the contents of which are incorporated herein by reference.

[0002] In recent years, wireless communications using high-frequency signals such as microwaves, quasi-millimeter waves, and millimeter waves have been attracting attention. For example, in 5G (fifth-generation mobile communications systems), high-frequency signals such as those in the 28 GHz band are used to achieve ultra-high speeds, ultra-low latency, and multiple simultaneous connections. Representative examples of planar high-frequency transmission lines that transmit such high-frequency signals include microstrip lines and coplanar lines. A microstrip line is generally a line in which a ground conductor is formed on one side of a dielectric and a signal line conductor is formed on the other side. A coplanar line is a line in which a ground conductor and a signal line conductor are formed on the same plane (e.g., on one side of a dielectric). In both microstrip lines and coplanar lines, high-frequency signals are transmitted via two conductors (a signal line conductor and a ground conductor).

[0003] The following Patent Documents 1 and 2 disclose a transmission line in which a coplanar waveguide signal conductor is formed on the same plane as a ground conductor of a microstrip line, and the microstrip line signal conductor and the coplanar waveguide signal conductor are connected to each other via an interlayer connection. Specifically, an open end of the microstrip line signal conductor is connected to an open end of the coplanar waveguide signal conductor via a through hole, thereby achieving an interlayer connection between the microstrip line signal conductor and the coplanar waveguide signal conductor.

[0004] Japanese Unexamined Patent Publication No. 2005-94445 Japanese Unexamined Patent Publication No. 5-199019

[0005] In the transmission lines disclosed in the above-mentioned Patent Documents 1 and 2, the width of the signal line conductor of the microstrip line is generally often significantly different from the width of the signal line conductor of the coplanar line. For example, the width of the signal line conductor of the microstrip line is sometimes designed to be about five times the width of the signal line conductor of the coplanar line. In this transmission line in which a first transmission line (e.g., a microstrip line) and a second transmission line (e.g., a coplanar line) are interlayer-connected, a significant difference in the width of the signal line conductors of the first transmission line and the second transmission line causes a problem of increased reflection loss.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a transmission line that can reduce reflection loss when connecting a first transmission line and a second transmission line between layers.

[0007] In order to solve the above-described problems, a transmission line according to a first aspect of the present invention includes: a first transmission line having a first signal line conductor; a second transmission line having a second signal line conductor formed on a layer different from that of the first signal line conductor; and a connection portion having a connection via that electrically connects the first signal line conductor and the second signal line conductor between layers, wherein the first transmission line is a microstrip line having the first signal line conductor and a first ground conductor; the second transmission line is a coplanar line having the second signal line conductor and two second ground conductors that are formed to sandwich the second signal line conductor; and the connection portion includes two ground connection conductors that are electrically connected to the first ground conductor and the two second ground conductors, respectively, so as to surround at least one of the first signal line conductor and the second signal line conductor and the connection via in a planar view.

[0008] In a transmission line according to a first aspect of the present invention, a first signal line conductor of a first transmission line and a second signal line conductor of a second transmission line are connected to each other by a connection via, and a portion of at least one of the first signal line conductor and the second signal line conductor and the connection via are surrounded in a plan view by two ground connection conductors electrically connected to the first ground conductor and two second ground conductors, respectively. This introduces an inductance component into the ground connection conductor that serves as a return path for the transmission line, thereby reducing reflection loss due to a capacitance component that occurs when the microstrip line and the coplanar line are connected to each other by an interlayer connection.

[0009] Furthermore, a transmission line according to a second aspect of the present invention may be the transmission line according to the first aspect of the present invention, wherein at least one of the two ground connection conductors includes a first conductor portion connected to the first ground conductor, a second conductor portion connected to the second ground conductor, a third conductor portion formed on a layer different from that of the first conductor portion and the second conductor portion, a first via connecting the first conductor portion and the third conductor portion, and a second via connecting the second conductor portion and the third conductor portion.

[0010] A transmission line according to a third aspect of the present invention may be the transmission line according to the first aspect of the present invention, wherein the first transmission line further includes two third ground conductors that are formed on the same layer as the first signal line conductor so as to sandwich the first signal line conductor and are connected to the first ground conductor through vias, and the two third ground conductors are electrically connected to two of the second ground conductors, respectively.

[0011] Furthermore, a transmission line according to a fourth aspect of the present invention may be the transmission line according to the third aspect of the present invention, wherein at least one of the two third ground conductors in the transmission line according to the third aspect of the present invention has an extension portion formed to extend toward the second transmission line, and at least one of the two ground connection conductors has a second conductor portion connected to the second ground conductor, a third via connecting the second conductor portion and the extension portion, and the extension portion.

[0012] Furthermore, a transmission line according to a fifth aspect of the present invention may be the transmission line according to the third aspect of the present invention, wherein at least one of the two third ground conductors has an extension portion formed to extend toward the second transmission line, and at least one of the two ground connection conductors is formed on a layer opposite to the layer on which the second ground conductor is formed, with respect to the layer on which the third ground conductor is formed, and comprises: a first relay pad connected to the second ground conductor through a via, the extension portion, a second relay pad formed on the same layer as the second ground conductor, a fourth conductor portion formed on the same layer as the first relay pad and connected to the first relay pad, a fourth via connecting the extension portion and the second relay pad, and a fifth via connecting the second relay pad and the fourth conductor portion.

[0013] A transmission line according to a sixth aspect of the present invention may be the transmission line according to the first aspect of the present invention, wherein at least one of the two ground connection conductors is formed on a layer on which the second ground conductor is formed, opposite to a layer on which the first signal line conductor is formed, and further includes: a first relay pad connected to the second ground conductor through a via, a first conductor portion connected to the first ground conductor, a fourth conductor portion connected to the first relay pad, and a sixth via connecting the first conductor portion and the fourth conductor portion.

[0014] Furthermore, a transmission line according to a seventh aspect of the present invention may be the transmission line according to the first aspect of the present invention, wherein at least one of the two ground connection conductors is formed on a layer on the opposite side of a layer on which the first signal line conductor is formed with respect to a layer on which the second ground conductor is formed, and includes: a first relay pad connected to the second ground conductor through a via; a fourth ground conductor formed on a layer different from the layer on which the second ground conductor and the layer on which the first relay pad are formed and connected to the first relay pad through a via; a first conductor portion connected to the first ground conductor; a fifth conductor portion formed on the same layer as the first relay pad; a sixth conductor portion formed on the same layer as the fourth ground conductor and connected to the fourth ground conductor; a seventh via connecting the first conductor portion and the fifth conductor portion; and an eighth via connecting the fifth conductor portion and the sixth conductor portion.

[0015] Furthermore, the transmission line according to an eighth aspect of the present invention may be the transmission line according to any one of the third to fifth aspects of the present invention, wherein the width of the ground connection conductor is narrower than half the narrower of the width of the second ground conductor and the width of the third ground conductor.

[0016] A transmission line according to a ninth aspect of the present invention may be the transmission line according to any one of the first to eighth aspects of the present invention, wherein the connection portion is connected to at least one of the other end of the first signal line conductor and one end of the second signal line conductor, and includes a signal line narrow portion that is narrower than the first signal line conductor and the second signal line conductor, and the connection via electrically connects the first signal line conductor and the second signal line conductor between layers via the signal line narrow portion.

[0017] According to the present invention, it is possible to reduce reflection loss when connecting the first transmission line and the second transmission line between layers.

[0018] 1 is a perspective view showing a configuration of a main part of a transmission line according to an embodiment of the present invention; FIG. 2 is an enlarged perspective view of a portion of a transmission line according to an embodiment of the present invention; FIG. 3 is an enlarged plan view of a portion of a transmission line according to an embodiment of the present invention; FIG. 4 is a plan view showing a portion of a transmission line according to a first modified example; FIG. 5 is a plan view showing a portion of a transmission line according to the first modified example; FIG. 6 is a plan view showing a portion of a transmission line according to a second modified example; FIG. 7 is a side view showing a portion of a transmission line according to a third modified example; FIG. 8 is a perspective view showing a configuration of a main part of a transmission line according to a fifth modified example; FIG. 9 is a side view showing a portion of a transmission line according to a sixth modified example; FIG. 10 is a side view showing a portion of a transmission line according to a tenth modified example; FIG. 11 is a perspective view showing a configuration of a main part of a transmission line according to a comparative example; and FIG. 12 is a diagram showing the reflection characteristics of a transmission line according to an embodiment of the present invention and a transmission line according to a comparative example.

[0019] Hereinafter, transmission lines according to embodiments of the present invention will be described in detail with reference to the drawings. To facilitate understanding, the positional relationships of the components will be described with reference to an XYZ Cartesian coordinate system (the origin of which will be changed as appropriate) set in the drawings as needed. Furthermore, in the drawings referred to below, the dimensions of the components will be changed as needed to facilitate understanding.

[0020] FIG. 1 is a perspective view showing the main configuration of a transmission line according to one embodiment of the present invention. As shown in FIG. 1, the transmission line 1 of this embodiment includes a microstrip line 10 (first transmission line), a coplanar line 20 (second transmission line), and a connection portion 30 that provides interlayer connection between the microstrip line 10 and the coplanar line 20. Such a transmission line 1 is a line with a multilayer structure formed using semiconductor manufacturing technology. The transmission line 1 illustrated in FIG. 1 is a line with a four-layer structure. For ease of understanding, the four layers arranged in order from the −Z side to the +Z side will be referred to as the “first layer,” “second layer,” “third layer,” and “fourth layer.”

[0021] 1 is a line that transmits high-frequency signals such as microwaves, quasi-millimeter waves, and millimeter waves. Specifically, when a high-frequency signal is input to port P1 of microstrip line 10, transmission line 1 transmits the input high-frequency signal sequentially through microstrip line 10 and coplanar line 20 and outputs it from port P2 of coplanar line 20. When a high-frequency signal is input to port P2 of coplanar line 20, transmission line 1 transmits the input high-frequency signal sequentially through coplanar line 20 and microstrip line 10 and outputs it from port P1 of microstrip line 10.

[0022] The microstrip line 10 includes a signal line conductor 11 (first signal line conductor), a ground conductor 12 (first ground conductor), and ground conductors 13a and 13b (third ground conductors). The signal line conductor 11 has a constant width and thickness. The signal line conductor 11 is a linear strip conductor that has a predetermined length and extends in the X direction. One end E11 of the signal line conductor 11 serves as a port P1 through which a high-frequency signal is input or output, and the other end E12 is connected to the coplanar line 20 via a connection portion 30. The signal line conductor 11 is formed on the fourth layer.

[0023] The ground conductor 12 is wider than the signal line conductor 11 and has a constant thickness. The ground conductor 12 is a strip-shaped conductor extending in the X direction and having approximately the same length as the signal line conductor 11. The ground conductor 12 is formed on the third layer. The ground conductors 13a and 13b are narrower than the signal line conductor 11 and have a constant thickness. The ground conductors 13a and 13b are linear strip-shaped conductors extending in the X direction and having approximately the same length as the signal line conductor 11. The ground conductors 13a and 13b are formed on the fourth layer so as to sandwich the signal line conductor 11 in the Y direction with a predetermined gap between them. The ground conductors 13a and 13b are connected to the ground conductor 12 through multiple vias 14 provided at multiple locations in the X direction.

[0024] The signal line conductor 11 is disposed so as to be located at the center of the ground conductor 12 in the Y direction. The ground conductor 13a is disposed so that one side edge (+Y side) thereof is positioned substantially in the Y direction as one side edge (+Y side) of the ground conductor 12, and the ground conductor 13b is disposed so that the other side edge (-Y side) thereof is positioned substantially in the Y direction as the other side edge (-Y side) of the ground conductor 12. Furthermore, the signal line conductor 11, the ground conductor 12, and the ground conductors 13a and 13b are disposed so that the ends on the -X side and the ends on the +X side are positioned substantially in the X direction.

[0025] The coplanar line 20 includes a signal line conductor 21 (second signal line conductor), ground conductors 22a and 22b (second ground conductors), and a ground conductor 23 (fourth ground conductor). The signal line conductor 21 has a constant width and thickness. The signal line conductor 21 is a linear strip conductor that has a predetermined length and extends in the X direction. The width of the signal line conductor 21 is smaller than the width of the signal line conductor 11 of the microstrip line 10. For example, the width of the signal line conductor 21 is approximately one-third the width of the signal line conductor 11. One end E21 of the signal line conductor 21 is connected to the microstrip line 10 via a connection portion 30, and the other end E22 serves as a port P2 through which a high-frequency signal is input and output. The signal line conductor 21 is formed on the third layer.

[0026] The widths of the ground conductors 22a and 22b are approximately the same as the width of the signal line conductor 21, and the thicknesses of the ground conductors 22a and 22b are constant. The ground conductors 22a and 22b are linear strip conductors extending in the X direction and having approximately the same length as the signal line conductor 21. The ground conductors 22a and 22b are formed on the third layer so as to sandwich the signal line conductor 21 in the Y direction with a predetermined gap between them. The gap in the Y direction between the ground conductors 22a and 22b and the signal line conductor 21 is narrower than the gap in the Y direction between the signal line conductor 11 and the ground conductors 13a and 13b in the microstrip line 10. For example, the gap in the Y direction between the ground conductors 22a and 22b and the signal line conductor 21 is approximately one-third of the gap in the Y direction between the signal line conductor 11 and the ground conductors 13a and 13b.

[0027] The ground conductors 22a and 22b are connected to the ground conductor 23 through multiple vias 24 provided at multiple locations in the X direction. The width of the ground conductor 23 is wider than the width of the signal line conductor 21. The thickness of the ground conductor 23 is constant. The ground conductor 23 is a strip-shaped conductor that extends in the X direction and has approximately the same length as the ground conductors 22a and 22b. The ground conductor 23 is formed on the first layer.

[0028] Here, on the second layer between the third layer on which the ground conductors 22a and 22b are formed and the first layer on which the ground conductor 23 is formed, a plurality of relay pads 25 are formed at positions where the vias 24 are provided. The relay pads 25 are connected to the ground conductors 22a and 22b through the vias 24 on the +Z side, and are connected to the ground conductor 23 through the vias 24 on the −Z side. In other words, the ground conductors 22a and 22b and the ground conductor 23 are connected via the relay pads 25.

[0029] The reason for connecting the ground conductors 22a, 22b and the ground conductor 23 via the relay pads 25 in this manner is to ensure a sufficient distance in the Z direction between the ground conductors 22a, 22b and the ground conductor 23. Note that, to further ensure a sufficient distance in the Z direction between the ground conductors 22a, 22b and the ground conductor 23, one or more layers other than the second layer may be formed between the ground conductors 22a, 22b and the ground conductor 23.

[0030] The signal line conductor 21 is disposed so as to be located at the center of the ground conductor 23 in the Y direction. The ground conductor 22a is disposed so that one side edge (+Y side) is positioned substantially flush with one side edge (+Y side) of the ground conductor 23 in the Y direction, and the ground conductor 22b is disposed so that the other side edge (-Y side) is positioned substantially flush with the other side edge (-Y side) of the ground conductor 23 in the Y direction. Furthermore, the signal line conductor 21, the ground conductor 23, and the ground conductors 22a and 22b are disposed so that the -X side ends and the +X side ends are positioned substantially flush with each other in the X direction.

[0031] The ground conductors 22a and 22b and the ground conductor 23 are arranged so that their ends on the -X side are positioned at approximately the same position in the X direction, but the -X side end of the signal line conductor 21 is positioned closer to the -X side than the -X side ends of the ground conductors 22a and 22b and the ground conductor 23. The signal line conductor 21, the ground conductors 22a and 22b, and the ground conductor 23 are arranged so that their ends on the +X side are positioned at approximately the same position in the X direction.

[0032] 2 is an enlarged perspective view of a portion of a transmission line according to an embodiment of the present invention, and FIG. 3 is an enlarged plan view of a portion of a transmission line according to an embodiment of the present invention. As shown in FIG. 2 and FIG. 3, the connection portion 30 includes a signal line narrow portion 31, an upper pad 32, a connection via 33, a lower pad 34, and ground connection conductors 35 a and 35 b.

[0033] The signal line narrow section 31 is narrower than the signal line conductor 11 of the microstrip line 10, has approximately the same thickness as the signal line conductor 11, and is a linear strip-shaped conductor extending in the X direction with a predetermined length. The signal line narrow section 31 is formed on the fourth layer. The signal line narrow section 31 is formed to extend in the +X direction from the other end E12 of the signal line conductor 11. If the signal line conductor 11 of the microstrip line 10 and the signal line narrow section 31 of the connection section 30 are considered to be a single signal line, this signal line can be said to be a line formed so that its width narrows in a step-like manner at the other end E12 of the signal line conductor 11. The signal line narrow section 31 is provided to reduce the reflection loss of the transmission line 1 by introducing an inductance component into the signal line of the transmission line 1.

[0034] The upper pad 32 is a rectangular flat conductor connected to the other end (+X side) of the signal line narrow portion 31. The long sides of the upper pad 32 extend in the Y direction, and the short sides of the upper pad 32 extend in the X direction. The upper pad 32 is formed on the fourth layer. The lower pad 34 is a rectangular flat conductor connected to one end E21 of the signal line conductor 21 of the coplanar line 20. The long sides of the lower pad 34 extend in the Y direction, and the short sides of the upper pad 32 extend in the X direction. The lower pad 34 is formed on the third layer. The upper pad 32 and the lower pad 34 are formed to overlap in a plan view.

[0035] The upper pad 32 is provided to connect the signal line narrow portion 31 and the signal line conductor 21 of the coplanar line 20 with a plurality of connection vias 33 via the lower pad 34. The upper pad 32 and the lower pad 34 may be formed so that their long sides extend in the X direction and their short sides extend in the Y direction. The upper pad 32 and the lower pad 34 may also be connected by only one connection via 33. If the signal line narrow portion 31 and the signal line conductor 21 of the coplanar line 20 are directly connected by the connection via 33, the upper pad 32 and the lower pad 34 may be omitted.

[0036] The connection via 33 interlayer connects the upper pad 32 formed on the fourth layer with the lower pad 34 formed on the third layer. Here, the signal line conductor 11 of the microstrip line 10 is connected to the signal line narrow portion 31, and the upper pad 32 is connected to the signal line narrow portion 31. The signal line conductor 21 of the coplanar line 20 is connected to the lower pad 34. The upper pad 32 and the lower pad 34 are connected by the connection via 33. Therefore, the connection via 33 connects the signal line conductor 11 of the microstrip line 10 to the signal line conductor 21 of the coplanar line 20 via the upper pad 32, the signal line narrow portion 31, and the lower pad 34.

[0037] The ground connection conductor 35a connects the ground conductor 12 of the microstrip line 10 to the ground conductor 22a of the coplanar line 20. The ground connection conductor 35b connects the ground conductor 12 of the microstrip line 10 to the ground conductor 22b of the coplanar line 20. The ground connection conductors 35a and 35b are formed on the third layer.

[0038] Specifically, the ground connection conductor 35a is an L-shaped conductor that extends in the +X direction from the other end (+X side) on the +Y side of the other end (+X side) of the ground conductor 12, bends in the −Y direction at one end (−X side) of the ground conductor 22a in the Y direction, and is connected to one side edge (+Y side) of the one end (−X side) of the ground conductor 22a. The ground connection conductor 35b is an L-shaped conductor that extends in the +X direction from the other end (+X side) on the −Y side of the other end (+X side) of the ground conductor 12, bends in the +Y direction at one end (−X side) of the ground conductor 22b in the Y direction, and is connected to the other side edge (−Y side) of the one end (−X side) of the ground conductor 22b.

[0039] 3, the ground connection conductors 35a and 35b are formed in a plan view so as to surround the signal line narrow portion 31, the upper pad 32, the connection via 33, and the lower pad 34 (not shown in Fig. 3) together with the ground conductor 12 and the ground conductor 23. That is, in the connection portion 30, the microstrip line 10 and the coplanar line 20 overlap with the ground conductors in a plan view, but the signal line narrow portion 31, the upper pad 32, the connection via 33, and the lower pad 34 do not overlap with the ground conductor in a plan view. The reason for this configuration is to increase the inductance component of the signal line narrow portion 31.

[0040] 3 , the width W3 of the ground connecting conductors 35a and 35b is narrower than the width W1 of the ground conductors 13a and 13b of the microstrip line 10 and the width W2 of the ground conductors 22a and 22b of the coplanar line 20. Here, the width W3 of the ground connecting conductors 35a and 35b is preferably narrower than half the narrower of the width W1 of the ground conductors 13a and 13b and the width W2 of the ground conductors 22a and 22b. The width W3 of the ground connecting conductors 35a and 35b is narrowed in order to reduce the reflection loss of the transmission line 1 by introducing an inductance component into the ground connecting conductors 35a and 35b, which serve as the return path of the transmission line 1.

[0041] As described above, the transmission line 1 of this embodiment includes the microstrip line 10 having the signal line conductor 11 formed on the fourth layer, and the coplanar line 20 having the signal line conductor 21 formed on the third layer. The signal line narrow portion 31, which is narrower than the signal line conductor 11 and the signal line conductor 21, is connected to the signal line conductor 11, and the signal line conductor 11 and the signal line conductor 21 are electrically connected to each other via the signal line narrow portion 31 by the connecting via 33. In this embodiment, the upper pad 32 connected to the signal line conductor 11 and the lower pad 34 connected to the signal line conductor 21 are connected to each other via the connecting via 33.

[0042] In this transmission line 1, an inductance component of the signal line narrow section 31 itself and an inductance component resulting from the step-like shape when the signal line conductor 11 and the signal line narrow section 31 are considered as a single signal line are introduced into the signal line of the transmission line 1. This makes it possible to reduce the return loss resulting from the capacitor component that occurs when the microstrip line 10 and the coplanar line 20 are connected to each other via an interlayer connection. Furthermore, although the return loss of the transmission line 1 is frequency-dependent due to the capacitor component of the transmission line 1, the frequency dependence of the return loss of the transmission line 1 can be suppressed by the inductance component introduced by the signal line narrow section 31.

[0043] In this embodiment, the signal line narrow portion 31 is configured not to overlap the ground conductor in a plan view at the connection portion 30 that connects the microstrip line 10 and the coplanar line 20. This increases the inductance component of the signal line narrow portion 31, further reduces the reflection loss due to the capacitor component that occurs when the microstrip line 10 and the coplanar line 20 are connected to each other between layers, and further reduces the frequency dependency.

[0044] Additionally, in this embodiment, the width W3 of the ground connecting conductors 35a and 35b that connect the ground conductor 12 of the microstrip line 10 and the ground conductors 22a and 22b of the coplanar line 20 is set narrower than the width W1 of the ground conductors 13a and 13b and the width W2 of the ground conductors 22a and 22b. This introduces an inductance component into the ground connecting conductors 35a and 35b, which serve as the return path for the transmission line 1, thereby further reducing the reflection loss of the transmission line 1 and further reducing the frequency dependency.

[0045] <Modifications> <First Modification> Figures 4A and 4B are plan views showing a portion of a transmission line according to a first modification. In Figures 4A and 4B, components corresponding to those shown in Figures 1 to 3 are denoted by the same reference numerals. The transmission line according to the first modification shown in Figures 4A and 4B has a configuration in which the shapes of the ground connection conductors 35a and 35b of the connection portion 30 are changed. The ground connection conductors 35a and 35b may have any shape as long as they are configured to surround the signal line narrow portion 31, the upper pad 32, the connection via 33, and the lower pad 34 together with the ground conductor 12 and the ground conductor 23 in a plan view.

[0046] 4A, the ground connection conductor 35a is configured to extend beyond one side edge (+Y side) of the ground conductor 12 and one side edge (+Y side) of the ground conductor 22a toward the +Y side. The ground connection conductor 35b is configured to extend beyond the other side edge (-Y side) of the ground conductor 12 and the other side edge (-Y side) of the ground conductor 22b toward the -Y side. As a result, the area of ​​the region enclosed by the ground connection conductors 35a, 35b, together with the ground conductor 12 and the ground conductor 23, is larger in plan view than in the configurations shown in FIGS. 1 to 3.

[0047] Specifically, the ground connection conductor 35a is a generally J-shaped conductor that extends in the +Y direction from one edge (+Y side) of the other end (+X side) of the ground conductor 12, bends in the +X direction at a predetermined distance, extends in the +X direction to one end (-X side) of the ground conductor 22a in the Y direction, bends in the -Y direction at a position where it extends in the +X direction, and is connected to one edge (+Y side) of the one end (-X side) of the ground conductor 22a. The ground connection conductor 35b is a generally J-shaped conductor that extends in the -Y direction from the other edge (-Y side) of the other end (+X side) of the ground conductor 12, bends in the +X direction at a predetermined distance, extends in the +X direction to one end (-X side) of the ground conductor 22b in the Y direction, bends in the +Y direction at a position where it extends in the +X direction, and is connected to the other edge (-Y side) of the one end (-X side) of the ground conductor 22b.

[0048] 4B, the ground connection conductor 35a is configured to protrude in the +Y direction beyond one side edge (+Y side) of the ground conductor 12 and one side edge (+Y side) of the ground conductor 22a, and to partially extend in the +X direction. Furthermore, the ground connection conductor 35b is configured to protrude in the -Y direction beyond the other side edge (-Y side) of the ground conductor 12 and the other side edge (-Y side) of the ground conductor 22b, and to partially extend in the +X direction. As a result, the area of ​​the region enclosed by the ground connection conductors 35a, 35b, together with the ground conductor 12 and the ground conductor 23, is larger in plan view than in the example shown in FIG. 4A.

[0049] Specifically, the ground connection conductor 35a extends in the +Y direction from one side edge (+Y side) of the other end (+X side) of the ground conductor 12, bends in the +X direction after a predetermined distance, and continues in the +X direction to a position on the +X side of one end (-X side) of the ground conductor 22a in the Y direction. Then, it bends in the -Y direction from that position, bends in the -X direction after a predetermined distance, bends in the -X direction again at a position extending in the -X direction to one end (-X side) of the ground conductor 22a in the Y direction, and is connected to one side edge (+Y side) of one end (-X side) of the ground conductor 22a.

[0050] The ground connection conductor 35b extends in the −Y direction from the other side edge (−Y side) of the other end (+X side) of the ground conductor 12, bends in the +X direction after a predetermined distance, and continues in the +X direction to a position on the +X side of one end (−X side) of the ground conductor 22b in the Y direction. Then, the ground connection conductor 35b bends in the +Y direction from that position, bends in the −X direction after a predetermined distance, bends in the −X direction again after extending in the −X direction to one end (−X side) of the ground conductor 22b in the Y direction, and is connected to the other side edge (−Y side) of one end (−X side) of the ground conductor 22b.

[0051] According to the first modification described above, the lengths of the ground connecting conductors 35a and 35b can be made longer than in the transmission line 1 according to the embodiment described with reference to Figures 1 to 3. This allows the magnitude of the inductance component of the ground connecting conductors 35a and 35b, which serve as the return path of the transmission line 1, to be increased.

[0052] <Second Modification> Fig. 5 is a plan view showing a portion of a transmission line according to a second modification. In Fig. 5, components corresponding to those shown in Figs. 1 to 3 are denoted by the same reference numerals. The transmission line according to the second modification shown in Fig. 5 has a configuration in which the shape of the signal line narrow portion 31 is changed. Although the signal line narrow portion 31 shown in Figs. 1 to 3 has a shape that extends linearly in the X direction, the shape may be any shape.

[0053] 5, the signal line conductor 11 bends in the +Y direction at a position extending a first distance in the +X direction from the other end E12, then bends in the +X direction at a position extending a second distance from that position. Then, the signal line conductor 11 bends in the -Y direction at a position extending a third distance from that position, then bends in the +X direction at a position extending a second distance from that position, and is connected to the upper pad 32. In other words, the signal line narrow section 31 has a shape that bends in the Y direction, which intersects with the X direction. It should be noted that the example shown in FIG. 5 is merely an example.

[0054] According to the second modification described above, the length of the signal line narrow section 31 can be made longer or the shape of the signal line narrow section 31 can be made half-looped, as compared with the transmission line 1 according to the embodiment described with reference to Figures 1 to 3. This makes it possible to increase the magnitude of the inductance component of the signal line narrow section 31 that forms part of the signal line of the transmission line 1.

[0055] <<Third Modification>> Fig. 6 is a side view showing a portion of a transmission line according to a third modification. In Fig. 6, components corresponding to those shown in Figs. 1 to 3 are denoted by the same reference numerals. Also, Fig. 6 shows only components necessary for explanation, and components not necessary for explanation are omitted. The transmission line according to the third modification shown in Fig. 6 has a signal line narrow portion 31 provided in a layer different from the layer on which the signal line conductor 11 is formed.

[0056] 6, the signal line narrow section 31 is formed on a layer (referred to as the "fifth layer") that is formed on the +Z side of the fourth layer on which the signal line conductor 11 is formed. As shown in Fig. 6, one end (-X side) of the signal line narrow section 31 is connected to the other end (+X side) of the signal line conductor 11 via a connection via 15, and the other end (+X side) of the signal line narrow section 31 is connected to the upper pad 32 via a connection via 36.

[0057] The signal line narrow section 31 does not necessarily have to be formed on the fifth layer immediately above the fourth layer on which the signal line conductor 11 is formed. For example, the signal line narrow section 31 may be formed on a layer (referred to as the "sixth layer") formed on the +Z side of the fifth layer. Alternatively, the signal line narrow section 31 may be formed on a layer (referred to as the "seventh layer") formed on the +Z side of the sixth layer. In other words, the signal line narrow section 31 may be connected to the signal line conductor 11 and the upper pad 32 via one layer or multiple layers.

[0058] According to the third modification described above, the signal line narrow section 31 is formed in a layer different from the fourth layer on which the signal line conductor 11 is formed. This makes it possible to add the inductance component of the connection via 15 connecting the signal line conductor 11 and the signal line narrow section 31, and the inductance component of the connection via 36 connecting the signal line narrow section 31 and the upper pad 32, thereby making it possible to freely adjust the magnitude of the inductance component of the signal line narrow section 31.

[0059] <<Fourth Modification>> Fig. 7 is a perspective view showing the configuration of the main parts of a transmission line according to a fourth modification. In Fig. 7, components corresponding to those shown in Figs. 1 to 3 are denoted by the same reference numerals. The transmission line according to the fourth modification shown in Fig. 7 is configured such that signal line narrow portion 31 of connection portion 30 is omitted and a signal line narrow portion 37 is provided.

[0060] The narrow signal line portion 37 is a linear strip-shaped conductor that is narrower than the signal line conductor 21 of the coplanar line 20, has approximately the same thickness as the signal line conductor 21, and has a predetermined length extending in the X direction. The narrow signal line portion 37 is formed on the third layer. The narrow signal line portion 37 is formed to extend in the −X direction from one end E21 of the signal line conductor 21. If the signal line conductor 21 of the coplanar line 20 and the narrow signal line portion 37 of the connection portion 30 are considered to be a single signal line, then this signal line can be said to be a line formed so that its width narrows in a step-like manner at the end E21 of the signal line conductor 21. Like the narrow signal line portion 31, the narrow signal line portion 37 is provided to reduce the reflection loss of the transmission line 1 by introducing an inductance component into the signal line of the transmission line 1.

[0061] The upper pad 32 and the lower pad 34 are formed to overlap in plan view, similar to the transmission line 1 shown in Fig. 1, but are positioned on the -X side relative to their positions in the transmission line 1 shown in Fig. 1. The upper pad 32 is connected to the other end E12 (+X side) of the signal line conductor 11 of the microstrip line 10, and the lower pad 34 is connected to one end E21 (-X side) of the signal line narrow portion 37.

[0062] In this modification, the upper pad 32 and the lower pad 34 may also be formed so that their long sides extend in the X direction and their short sides extend in the Y direction. The upper pad 32 and the lower pad 34 may also be connected by only one connection via 33. When the signal line narrow portion 31 and the signal line conductor 11 of the microstrip line 10 are directly connected by the connection via 33, the upper pad 32 and the lower pad 34 may be omitted.

[0063] According to the fourth modification described above, the signal line narrow section 31 connected to the signal line conductor 11 of the microstrip line 10 is omitted, and instead a signal line narrow section 37 is provided connected to the signal line conductor 21 of the coplanar line 20. This increases the degree of freedom in designing the signal line narrow section in the connection section 30.

[0064] <Fifth Modification> Fig. 8 is a perspective view showing the configuration of the main parts of a transmission line according to a fifth modification. In Fig. 8, components corresponding to those shown in Figs. 1 to 3 and 7 are denoted by the same reference numerals. The transmission line according to the fifth modification shown in Fig. 8 is configured such that connection portion 30 is provided with signal line narrow portion 31 and signal line narrow portion 37.

[0065] 1 and 7, the upper pad 32 and the lower pad 34 are formed to overlap in plan view, but are positioned such that their positions in the X direction are approximately midway between the other end E12 of the signal line conductor 11 and one end E21 of the signal line conductor 21. The upper pad 32 is connected to the other end (+X side) of the signal line narrow portion 31, similar to the upper pad 32 shown in Fig. 1, and the lower pad 34 is connected to one end (-X side) of the signal line narrow portion 37, similar to the lower pad 34 shown in Fig. 7.

[0066] In this modification, the upper pad 32 and the lower pad 34 may also be formed so that their long sides extend in the X direction and their short sides extend in the Y direction. The upper pad 32 and the lower pad 34 may also be connected by only one connection via 33. When the signal line narrow portion 31 and the signal line narrow portion 37 are directly connected by the connection via 33, the upper pad 32 and the lower pad 34 may be omitted.

[0067] According to the fifth modification described above, the signal line narrow section 37 is provided to connect to the signal line conductor 21 of the coplanar line 20, in addition to the signal line narrow section 31 connected to the signal line conductor 11 of the microstrip line 10. This increases the degree of freedom in designing the signal line narrow section in the connection section 30.

[0068] <<Sixth Modification>> Fig. 9 is a side view showing a portion of a transmission line according to a sixth modification. In Fig. 9, components corresponding to those shown in Figs. 1 to 4B are denoted by the same reference numerals. In Fig. 9, only components necessary for the explanation are shown, and components not necessary for the explanation are omitted.

[0069] 9 has a configuration in which the structure of the ground connection conductors 35a, 35b of the connection portion 30 is changed. Specifically, while the ground connection conductors 35a, 35b shown in FIGS. 1 to 4B are formed on a single layer (the third layer), in this modification, the ground connection conductors 35a, 35b are formed across multiple layers. Note that, for ease of understanding, the following description will be given using the ground connection conductor 35b as an example, and a description of the ground connection conductor 35a will be omitted.

[0070] 9 , the ground connection conductor 35b includes a first conductor portion 51, a second conductor portion 52, a third conductor portion 53, a first via 61, and a second via 62. The first conductor portion 51 is a linear strip conductor connected to the ground conductor 12 and extending in the +X direction. One end (−X side) of the first conductor portion 51 is connected to the other end (+X side) of the ground conductor 12 on the −Y side of the other end (+X side). The first conductor portion 51 is formed on the same third layer as the ground conductor 12.

[0071] The second conductor portion 52 is an L-shaped conductor connected to the ground conductor 22b. One end (-X side) of the second conductor portion 52 is located a predetermined distance in the +X direction from the other end (+X side) of the first conductor portion 51. The second conductor portion 52 extends in the +X direction from that position and bends in the +Y direction at one end (-X side) of the ground conductor 22b in the Y direction. The second conductor portion 52 is connected to the other side edge (-Y side) of the one end (-X side) of the ground conductor 22b. The second conductor portion 52 is formed on the same third layer as the ground conductor 22b.

[0072] The third conductor portion 53 is a linear strip conductor extending from the other end (+X side) of the first conductor portion 51 to one end (−X side) of the second conductor portion 52 on the +Z side of the first conductor portion 51 and the second conductor portion 52. The third conductor portion 53 is formed on the same fourth layer as the ground conductor 13b. The first via 61 provides an interlayer connection between the other end (+X side) of the first conductor portion 51 and one end (−X side) of the third conductor portion 53. The second via 62 provides an interlayer connection between the one end (−X side) of the second conductor portion 52 and the other end (+X side) of the third conductor portion 53. Note that while FIG. 9 illustrates an example in which one first via 61 and one second via 62 are provided, multiple first vias 61 and multiple second vias 62 may be provided.

[0073] As described above, in this modification, parts of the ground connection conductors 35a, 35b (the first conductor portion 51 and the second conductor portion 52) are formed on the same layer as the third layer on which the ground conductor 12 and the ground conductors 22a, 22b are formed. Furthermore, other parts of the ground connection conductors 35a, 35b (the third conductor portion 53) are formed on the same layer as the fourth layer on which the ground conductor 13b is formed. The parts of the ground connection conductors 35a, 35b and the other parts of the ground connection conductors 35a, 35b are connected to each other via the first vias 61 and the second vias 62.

[0074] 4A and 4B, according to the sixth modification described above, the lengths of the ground connecting conductors 35a and 35b can be made longer than in the transmission line 1 according to the embodiment described with reference to Figures 1 to 3. This makes it possible to increase the magnitude of the inductance component of the ground connecting conductors 35a and 35b, which serve as the return path of the transmission line 1.

[0075] <<Seventh Modification>> Fig. 10 is a side view showing a portion of a transmission line according to a seventh modification. In Fig. 10, components corresponding to those shown in Figs. 1 to 4B and 9 are denoted by the same reference numerals. In Fig. 10, as in Fig. 9, only components necessary for explanation are shown, and components not necessary for explanation are omitted.

[0076] The transmission line according to the seventh modification shown in Fig. 10 has a configuration in which the ground connection conductors 35a, 35b are formed across multiple layers, similar to the transmission line according to the sixth modification shown in Fig. 9. However, while the third conductor portion 53 is formed on the fourth layer as part of the ground connection conductors 35a, 35b in the sixth modification shown in Fig. 9, the ground conductors 13a, 13b formed on the fourth layer are used as part of the ground connection conductors 35a, 35b in this modification. Note that, as with the sixth modification, the following description will be given using the ground connection conductor 35b as an example, and a description of the ground connection conductor 35a will be omitted.

[0077] 10 , the ground connection conductor 35b includes a second conductor portion 52 and a third via 63, and includes a part of the ground conductor 13b and the via 14. The second conductor portion 52 is the same as the second conductor portion 52 described in the sixth modification and is an L-shaped conductor connected to the ground conductor 22b. The second conductor portion 52 is formed on the same third layer as the ground conductor 22b.

[0078] The ground conductor 13b has an extension portion EX that is formed on the +Z side of the ground conductor 12 and the second conductor portion 52 and extends from the other end (+X side) of the ground conductor 12 to one end (−X side) of the second conductor portion 52. The ground conductor 13b that has such an extension portion EX is connected to the ground conductor 12 through a plurality of vias 14 that are provided at a plurality of locations in the X direction.

[0079] The width of the extension portion EX may be the same as or different from that of the ground conductor 13b. However, similar to the width W3 of the ground connecting conductors 35a and 35b shown in FIG. 3 , the width of the extension portion EX is preferably narrower than the width W1 of the ground conductors 13a and 13b and the width W2 of the ground conductors 22a and 22b of the coplanar line 20. Furthermore, the width of the extension portion EX is more preferably narrower than half the narrower of the width W1 of the ground conductors 13a and 13b and the width W2 of the ground conductors 22a and 22b. Narrowing the width of the extension portion EX introduces an inductance component into the ground connecting conductors 35a and 35b, which serve as the return path of the transmission line 1, thereby reducing the reflection loss of the transmission line 1.

[0080] The third via 63 provides interlayer connection between one end (-X side) of the second conductor portion 52 and the other end (+X side) of the extension portion EX of the ground conductor 13 b. Note that, although an example in which only one third via is provided is illustrated in Fig. 10, multiple third vias 63 may be provided.

[0081] As described above, in this modification, parts (second conductor portions 52) of the ground connection conductors 35a, 35b are formed on the same layer as the third layer on which the ground conductor 12 and the ground conductors 22a, 22b are formed. Furthermore, in this modification, the via 14 and a portion of the ground conductor 13b, which is formed on the fourth layer and includes the extension portion EX, are used as other parts of the ground connection conductors 35a, 35b. The parts of the ground connection conductors 35a, 35b and the other parts of the ground connection conductors 35a, 35b are connected to each other through the third via 63.

[0082] According to the seventh modification described above, similarly to the sixth modification described with reference to Fig. 9, the lengths of the ground connecting conductors 35a and 35b can be made longer than in the transmission line 1 according to the embodiment described with reference to Fig. 1 to Fig. 3. This allows the magnitude of the inductance component of the ground connecting conductors 35a and 35b, which serve as the return path of the transmission line 1, to be increased.

[0083] <Eighth Modification> Fig. 11 is a side view showing a portion of a transmission line according to an eighth modification. In Fig. 11, components corresponding to those shown in Figs. 1 to 4B and 10 are denoted by the same reference numerals. In Fig. 11, as in Figs. 9 and 10, only components necessary for explanation are shown, and components not necessary for explanation are omitted.

[0084] The transmission line according to the eighth modification shown in Fig. 11 has a configuration in which the ground connection conductors 35a, 35b are formed across multiple layers, similar to the transmission lines according to the sixth and seventh modifications shown in Fig. 9 and Fig. 10. However, while the ground connection conductors 35a, 35b are formed across two layers, the third and fourth layers, in the sixth and seventh modifications shown in Fig. 9 and Fig. 10, the ground connection conductors 35a, 35b are formed across three layers, the second to fourth layers, in this modification. Note that, as with the sixth and seventh modifications, the following description will be given taking the ground connection conductor 35b as an example, and a description of the ground connection conductor 35a will be omitted.

[0085] 11 , the ground connection conductor 35b includes a relay pad Pd (second relay pad), a fourth conductor portion 54, a fourth via 64, and a fifth via 65, and includes a relay pad 25 (first relay pad) and the via 24 on the +Z side of the relay pad 25 in addition to a part of the ground conductor 13b and the via 14. The relay pad Pd is formed on the third layer. Specifically, the relay pad Pd is formed at one end (−X side) of the second conductor portion 52 shown in FIG. 10 . The other end (+X side) of the second conductor portion 52 shown in FIG. 10 is connected to the ground conductor 22b, but the relay pad Pd is not connected to the ground conductor 22b.

[0086] The fourth conductor portion 54 is an L-shaped conductor connected to the relay pad 25. The fourth conductor portion 54 is formed on the same second layer as the relay pad 25. One end (-X side) of the fourth conductor portion 54 is located on the -Z side of the relay pad Pd. The fourth conductor portion 54 extends in the +X direction from that position and bends in the +Y direction at one end (-X side) of the ground conductor 22b in the Y direction. The fourth conductor portion 54 is then connected to the other side edge (-Y side) of the one end (-X side) of the relay pad 25.

[0087] The fourth via 64 provides interlayer connection between the other end (+X side) of the extension portion EX of the ground conductor 13b and the relay pad Pd. The fifth via 65 provides interlayer connection between the relay pad Pd and one end (-X side) of the fourth conductor portion 54. While FIG. 11 illustrates an example in which one fourth via 64 and one fifth via 65 are provided, multiple fourth vias 64 and multiple fifth vias 65 may be provided. The relay pad 25 is connected to the ground conductor 22b via the via 24 on the +Z side.

[0088] As described above, in this modification, a portion (fourth conductor portion 54) of the ground connection conductors 35a, 35b is formed on the same layer as the second layer on which the relay pad 25 is formed, and is connected to the relay pad 25. Furthermore, in this modification, the relay pad 25 and the via 24 are used as a portion of the ground connection conductors 35a, 35b. Furthermore, in this modification, the via 14 and a portion of the ground conductor 13b, which is formed on the fourth layer and includes the extension portion EX, are used as another portion of the ground connection conductors 35a, 35b. The portions of the ground connection conductors 35a, 35b and the other portions of the ground connection conductors 35a, 35b are connected to each other via the fourth via 64, the relay pad Pd formed on the third layer, and the fifth via 65.

[0089] According to the eighth modification described above, similarly to the sixth and seventh modifications described with reference to Figures 9 and 10, the lengths of the ground connecting conductors 35a and 35b can be made longer than in the transmission line 1 according to the embodiment described with reference to Figures 1 to 3. This makes it possible to increase the magnitude of the inductance component of the ground connecting conductors 35a and 35b, which serve as the return path of the transmission line 1.

[0090] <Ninth Modification> Fig. 12 is a side view showing a portion of a transmission line according to a ninth modification. In Fig. 12, components corresponding to those shown in Figs. 1 to 4B and 9 to 11 are denoted by the same reference numerals. In Fig. 12, as in Figs. 9 to 11, only components necessary for explanation are shown, and components not necessary for explanation are omitted.

[0091] The transmission line according to the ninth modification shown in Fig. 12 has a configuration in which the ground connection conductors 35a, 35b are formed across multiple layers, similar to the transmission lines according to the sixth to eighth modifications shown in Fig. 9 to Fig. 11. Specifically, in this modification, the ground connection conductors 35a, 35b are formed across two layers, the second and third layers. Note that, as with the sixth to eighth modifications, the following description will be given taking the ground connection conductor 35b as an example, and a description of the ground connection conductor 35a will be omitted.

[0092] 12 , the ground connection conductor 35b includes a first conductor portion 51, a fourth conductor portion 54, and a sixth via 66, and also includes a relay pad 25 (first relay pad) and a via 24 on the +Z side of the relay pad 25. The first conductor portion 51 is similar to the first conductor portion 51 shown in FIG. 9 , and is a linear band-shaped conductor connected to the ground conductor 12 and extending in the +X direction.

[0093] 11 , and is an L-shaped conductor connected to the relay pad 25. However, in this embodiment, one end (−X side) of the fourth conductor 54 is located on the −Z side of the other end (+X side) of the first conductor 51. The fourth conductor 54 is formed in the same second layer as the relay pad 25.

[0094] The sixth via 66 provides interlayer connection between the other end (+X side) of the first conductor portion 51 and one end (-X side) of the fourth conductor portion 54. Although Fig. 12 illustrates an example in which only one sixth via 66 is provided, multiple sixth vias 66 may be provided. The relay pad 25 is connected to the ground conductor 22b via the via 24 on the +Z side.

[0095] As described above, in this modification, parts (first conductor portions 51) of the ground connection conductors 35a, 35b are formed on the same layer as the third layer on which the ground conductor 12 and the ground conductors 22a, 22b are formed, and are connected to the ground conductor 12. Furthermore, other parts (fourth conductor portions 54) of the ground connection conductors 35a, 35b are formed on the same layer as the second layer on which the relay pad 25 is formed, and are connected to the relay pad 25. Furthermore, in this modification, the relay pad 25 and the via 24 are used as other parts of the ground connection conductors 35a, 35b. Furthermore, parts of the ground connection conductors 35a, 35b and other parts of the ground connection conductors 35a, 35b are connected to each other through the sixth via 66.

[0096] According to the ninth modification described above, similarly to the sixth to eighth modifications described with reference to Figures 9 to 11, the lengths of the ground connecting conductors 35a and 35b can be made longer than in the transmission line 1 according to the embodiment described with reference to Figures 1 to 3. This allows the magnitude of the inductance component of the ground connecting conductors 35a and 35b, which serve as the return path of the transmission line 1, to be increased.

[0097] <<Tenth Modification>> Fig. 13 is a side view showing a portion of a transmission line according to a tenth modification. In Fig. 13, components corresponding to those shown in Figs. 1 to 4B and 9 to 12 are denoted by the same reference numerals. In Fig. 13, as in Figs. 9 to 12, only components necessary for explanation are shown, and components not necessary for explanation are omitted.

[0098] The transmission line according to the tenth modification shown in Fig. 13 has a configuration in which the ground connection conductors 35a, 35b are formed across multiple layers, similar to the transmission lines according to the sixth to ninth modifications shown in Fig. 9 to Fig. 12. Specifically, in this modification, the ground connection conductors 35a, 35b are formed across three layers, the first to third layers. Note that, as with the sixth to ninth modifications, the following description will be given taking the ground connection conductor 35b as an example, and a description of the ground connection conductor 35a will be omitted.

[0099] 13 , the ground connection conductor 35b includes a first conductor portion 51, a fifth conductor portion 55, a sixth conductor portion 56, a seventh via 67, and an eighth via 68, and also includes a part of the ground conductor 23, a relay pad 25 (first relay pad), and vias 24 on the ±Z sides of the relay pad 25. The first conductor portion 51 is similar to the first conductor portion 51 shown in FIGS. 9 and 12 , and is a linear band-shaped conductor connected to the ground conductor 12 and extending in the +X direction.

[0100] The fifth conductor portion 55 is a linear band-shaped conductor that extends a predetermined distance in the +X direction from a position on the −Z side of the other end (+X side) of the first conductor portion 51. The fifth conductor portion 55 is formed on the same second layer as the relay pad 25, but is not connected to the relay pad 25.

[0101] The sixth conductor portion 56 is formed on the same first layer as the ground conductor 23. The sixth conductor portion 56 is generally similar to the fourth conductor portion 54 shown in FIG. 12 and is an L-shaped conductor connected to the ground conductor 23. One end (−X side) of the sixth conductor portion 56 is located on the −Z side of the other end (+X side) of the fifth conductor portion 55. The sixth conductor portion 56 extends in the +X direction from that position and bends in the +Y direction at one end (−X side) of the ground conductor 23 in the Y direction. The sixth conductor portion 56 is then connected to the other side edge (−Y side) of the one end (−X side) of the ground conductor 23.

[0102] The seventh via 67 provides interlayer connection between the other end (+X side) of the first conductor portion 51 and one end (-X side) of the fifth conductor portion 55. The eighth via 68 provides interlayer connection between the other end (+X side) of the fifth conductor portion 55 and one end (-X side) of the sixth conductor portion 56. While FIG. 13 illustrates an example in which one seventh via 67 and one eighth via 68 are provided, multiple seventh vias 67 and multiple eighth vias 68 may be provided. The relay pad 25 is connected to the ground conductor 22b via the via 24 on the +Z side and to the ground conductor 23 via the via 24 on the -Z side.

[0103] As described above, in this modification, parts (first conductor portions 51) of the ground connection conductors 35a and 35b are formed on the same layer as the third layer on which the ground conductor 12 and the ground conductors 22a and 22b are formed, and are connected to the ground conductor 12. Another parts (fifth conductor portions 55) of the ground connection conductors 35a and 35b are formed on the same layer as the second layer on which the relay pad 25 is formed. Another parts (sixth conductor portions 56) of the ground connection conductors 35a and 35b are formed on the same layer as the first layer on which the ground conductor 23 is formed.

[0104] In this modification, a portion of the ground conductor 23, the relay pad 25, and the via 24 are used as other portions of the ground connection conductors 35a, 35b. The portions of the ground connection conductors 35a, 35b and other portions of the ground connection conductors 35a, 35b are connected to each other via a seventh via 67. The other portions of the ground connection conductors 35a, 35b and other portions of the ground connection conductors 35a, 35b are connected to each other via an eighth via 68.

[0105] According to the tenth modification described above, similarly to the sixth to ninth modifications described with reference to Figures 9 to 12, the lengths of the ground connecting conductors 35a and 35b can be made longer than in the transmission line 1 according to the embodiment described with reference to Figures 1 to 3. This makes it possible to increase the magnitude of the inductance component of the ground connecting conductors 35a and 35b, which serve as the return path of the transmission line 1.

[0106] In the sixth to tenth modified examples, both of the ground connection conductors 35a, 35b may have the structures shown in Figures 9 to 13, or only one of the ground connection conductors 35a, 35b may have the structure shown in Figures 9 to 13. In other words, it is sufficient that at least one of the ground connection conductors 35a, 35b has the structure shown in Figures 9 to 13.

[0107] <Comparison between the embodiment and the comparative example> Fig. 14 is a perspective view showing the configuration of a main part of a transmission line according to the comparative example. A transmission line 100 according to the comparative example shown in Fig. 14 includes a microstrip line 10, a coplanar line 20, and a connection portion 40 that connects the microstrip line 10 and the coplanar line 20 between layers. The microstrip line 10 and the coplanar line 20 have the same configurations as the microstrip line 10 and the coplanar line 20 included in the transmission line 1 according to the embodiment of the present invention shown in Fig. 1. However, the signal line conductor 21 of the coplanar line 20 extends further in the -X direction than the transmission line 1 shown in Fig. 1.

[0108] The connection portion 40 includes an upper pad 41, a connection via 42, a lower pad 43, and ground connection conductors 44a and 44b. The upper pad 41 is connected to the other end (+X side) of the signal line conductor 11 of the microstrip line 10, and is a tapered flat conductor whose width gradually narrows toward the +X side. The upper pad 41 is formed on the fourth layer. Note that the transmission line 100 according to the comparative example does not have a configuration equivalent to the signal line narrow portion 31 shown in FIG. 1 .

[0109] The lower pad 43, like the lower pad 34 shown in FIG. 1 , is a rectangular flat conductor connected to one end (−X side) of the signal line conductor 21 of the coplanar line 20. The longer side of the lower pad 43 extends in the Y direction, and the shorter side of the lower pad 43 extends in the X direction. The lower pad 43 is formed on the third layer. The upper pad 41 and the lower pad 43 are formed so as to overlap in a plan view. The connection via 42 provides interlayer connection between the upper pad 41 formed on the fourth layer and the lower pad 43 formed on the third layer.

[0110] 1 , the ground connection conductor 44a connects the ground conductor 12 of the microstrip line 10 to the ground conductor 22a of the coplanar line 20. Similar to the ground connection conductor 35b shown in Fig. 1 , the ground connection conductor 44b connects the ground conductor 12 of the microstrip line 10 to the ground conductor 22b of the coplanar line 20. The ground connection conductors 35a and 35b are formed on the third layer.

[0111] The ground connection conductor 44a is an L-shaped conductor in a planar view, similar to the ground connection conductor 35a shown in Fig. 1, and the ground connection conductor 44b is an L-shaped conductor in a planar view, similar to the ground connection conductor 35b shown in Fig. 1. However, the widths of the ground connection conductors 44a and 44b are wider than the widths of the ground connection conductors 35a and 35b shown in Fig. 1. Specifically, the widths of the ground connection conductors 44a and 44b are wider than the width W1 of the ground conductors 13a and 13b of the microstrip line 10 (see Fig. 3) and the width W2 of the ground conductors 22a and 22b of the coplanar line 20 (see Fig. 3).

[0112] As described above, the connection portion 40 of the transmission line 100 according to the comparative example differs significantly from the connection portion 30 of the transmission line 1 shown in Fig. 1 in the following two respects. The first difference is that the connection portion 40 does not have a configuration equivalent to the signal line narrow portion 31 shown in Fig. 1. The second difference is that the widths of the ground connection conductors 44a and 44b provided in the connection portion 40 are not narrower than the widths of the ground connection conductors 35a and 35b shown in Fig. 1.

[0113] 15 is a diagram showing the reflection characteristics of the transmission line according to one embodiment of the present invention and the transmission line according to the comparative example. As shown in Fig. 15, both the transmission line 1 according to one embodiment of the present invention and the transmission line 100 according to the comparative example have a characteristic in which the reflection coefficient increases (the return loss increases) as the frequency of the high-frequency signal increases.

[0114] However, referring to Fig. 15, it can be seen that the transmission line 1 according to one embodiment of the present invention has a smaller reflection coefficient (return loss) in a frequency band of approximately 6 GHz or higher than the transmission line 100 according to the comparative example. Also referring to Fig. 15, it can be seen that the transmission line 1 according to one embodiment of the present invention has a gentler slope of the graph showing the increase in reflection coefficient relative to an increase in frequency than the transmission line 100 according to the comparative example, and that the frequency dependency of the return loss is suppressed.

[0115] The above describes a transmission line according to one embodiment of the present invention and a transmission line according to a modification thereof. However, the present invention is not limited to the above embodiment and modifications, and can be freely modified within the scope of the present invention. For example, the above-described embodiments and modifications can be combined as appropriate. For example, the signal line narrow section 37 of the transmission line according to the fifth modification shown in FIG. 7 can be shaped like the signal line narrow section 31 of the transmission line according to the second modification shown in FIG. 5.

[0116] Furthermore, the signal line narrow section 37 of the transmission line according to the fifth modification shown in Fig. 7 can be provided in a layer different from the layer on which the signal line conductor 21 is formed, like the signal line narrow section 31 of the transmission line according to the third modification shown in Fig. 6. In this case, the signal line narrow section 37 provided in the layer different from the layer on which the signal line conductor 21 is formed is connected to the signal line conductor 21 and the lower pad 34 through vias (not shown) (vias corresponding to the connection vias 15 and 36 shown in Fig. 6).

[0117] In the above-described embodiment and modified examples, when the signal line conductor 11 of the microstrip line 10 and the signal line narrow portion 31 of the connection unit 30 are considered to be a single signal line, the shape of the signal line is such that the width narrows in a step-like manner at the other end E12 of the signal line conductor 11. Also, when the signal line conductor 21 of the coplanar line 20 and the signal line narrow portion 37 of the connection unit 30 are considered to be a single signal line, the shape of the signal line is such that the width narrows in a step-like manner at the one end E21 of the signal line conductor 21. However, the above-described signal line does not necessarily have to have a step-like narrowing shape, and may have, for example, a tapered shape in which the width gradually narrows.

[0118] In the above-described embodiment and modified examples, the microstrip line 10 includes the signal line conductor 11, the ground conductor 12, and the ground conductors 13 a and 13 b, but the ground conductors 13 a and 13 b may be omitted. In addition, by omitting the ground conductors 13 a and 13 b, the vias 14 connecting the ground conductors 13 a and 13 b to the ground conductor 12 may also be omitted.

[0119] In the above-described embodiment and modified example, the coplanar line 20 includes the signal line conductor 21, the ground conductors 22a and 22b, and the ground conductor 23. However, the ground conductor 23 may be omitted. In addition, the vias 24 and the relay pads 25 that connect the ground conductor 23 to the ground conductors 22a and 22b may also be omitted.

[0120] However, from the viewpoint of stabilizing the electric field distribution and reducing unwanted radiation, it is desirable to provide ground conductors 13 a and 13 b on the microstrip line 10. Furthermore, from the viewpoint of preventing the occurrence of unwanted modes, it is desirable to provide a ground conductor 23 on the coplanar line 20.

[0121] According to the present invention, it is possible to reduce reflection loss when connecting the first transmission line and the second transmission line between layers.

[0122] DESCRIPTION OF SYMBOLS 1...transmission line, 10...microstrip line, 11...signal line conductor, 12...ground conductor, 13a, 13b...ground conductor, 14...via, 15...connection via, 20...coplanar line, 21...signal line conductor, 22a, 22b...ground conductor, 23...ground conductor, 24...via, 25...relay pad, 30...connection portion, 31...signal line narrow portion, 33...connection via, 35a, 35b...ground connection Conductor, 36...connection via, 37...signal line narrow portion, 51...first conductor portion, 52...second conductor portion, 53...third conductor portion, 54...fourth conductor portion, 55...fifth conductor portion, 56...sixth conductor portion, 61...first via, 62...second via, 63...third via, 64...fourth via, 65...fifth via, 66...sixth via, 67...seventh via, 68...eighth via, E12...other end portion, E21...one end portion, EX...extension portion, Pd...relay pad

Claims

1. A transmission line comprising: a first transmission line having a first signal line conductor; a second transmission line having a second signal line conductor formed on a layer different from that of the first signal line conductor; and a connection portion having a connection via that electrically connects the first signal line conductor and the second signal line conductor between layers, wherein the first transmission line is a microstrip line having the first signal line conductor and a first ground conductor; the second transmission line is a coplanar line having the second signal line conductor and two second ground conductors formed to sandwich the second signal line conductor; and the connection portion comprises two ground connection conductors electrically connected to the first ground conductor and two of the second ground conductors, respectively, so as to surround at least a portion of the first signal line conductor and the second signal line conductor and the connection via in a planar view.

2. The transmission line according to claim 1, wherein at least one of the two ground connection conductors comprises: a first conductor portion connected to the first ground conductor; a second conductor portion connected to the second ground conductor; a third conductor portion formed on a different layer from the first conductor portion and the second conductor portion; a first via connecting the first conductor portion and the third conductor portion; and a second via connecting the second conductor portion and the third conductor portion.

3. The transmission line according to claim 1, wherein the first transmission line comprises two third ground conductors that are formed on the same layer as the first signal line conductor so as to sandwich the first signal line conductor and are connected to the first ground conductor through vias, and the two third ground conductors are electrically connected to two of the second ground conductors, respectively.

4. The transmission line according to claim 3, wherein at least one of the two third ground conductors has an extension portion formed to extend toward the second transmission line, and at least one of the two ground connection conductors has: a second conductor portion connected to the second ground conductor; a third via connecting the second conductor portion and the extension portion; and the extension portion.

5. The transmission line according to claim 3, wherein at least one of the two third ground conductors has an extension portion formed to extend toward the second transmission line, and at least one of the two ground connection conductors comprises: a first relay pad formed on a layer opposite to the layer on which the second ground conductor is formed, and connected to the second ground conductor through a via, the extension portion; a second relay pad formed on the same layer as the second ground conductor; a fourth conductor portion formed on the same layer as the first relay pad and connected to the first relay pad; a fourth via connecting the extension portion and the second relay pad; and a fifth via connecting the second relay pad and the fourth conductor portion.

6. The transmission line according to claim 1, wherein at least one of the two ground connection conductors is formed on a layer on the opposite side of the layer on which the second ground conductor is formed from the layer on which the first signal line conductor is formed, and comprises: a first relay pad connected to the second ground conductor through a via; a first conductor portion connected to the first ground conductor; a fourth conductor portion connected to the first relay pad; and a sixth via connecting the first conductor portion and the fourth conductor portion.

7. The transmission line according to claim 1, wherein at least one of the two ground connection conductors comprises: a first relay pad formed on a layer on the opposite side of the layer on which the second ground conductor is formed from the layer on which the first signal line conductor is formed, and connected to the second ground conductor through a via; a fourth ground conductor formed on a layer different from the layer on which the second ground conductor and the layer on which the first relay pad are formed, and connected to the first relay pad through a via; a first conductor portion connected to the first ground conductor; a fifth conductor portion formed on the same layer as the first relay pad; a sixth conductor portion formed on the same layer as the fourth ground conductor and connected to the fourth ground conductor; a seventh via connecting the first conductor portion and the fifth conductor portion; and an eighth via connecting the fifth conductor portion and the sixth conductor portion.

8. The transmission line according to claim 3, wherein the width of the ground connection conductor is smaller than half the narrower of the width of the second ground conductor and the width of the third ground conductor.

9. A transmission line as claimed in any one of claims 1 to 8, wherein the connection portion comprises a signal line narrow portion connected to at least one of the other end of the first signal line conductor and one end of the second signal line conductor, the signal line narrow portion being narrower than the first signal line conductor and the second signal line conductor, and the connection via electrically connects the first signal line conductor and the second signal line conductor between layers via the signal line narrow portion.

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