Grounded coplanar waveguide and electronic apparatus

Abstract

A grounded coplanar waveguide (101) is configured from a laminate provided with a plurality of laminated insulator layers (11, 12, 13) and a conductor layer that is formed by being joined to a surface extending along the insulator layers (11, 13). The conductor layer includes a reference ground conductor layer (21), a signal line conductor layer (23) that overlaps the reference ground conductor layer (21) when the laminate is viewed in the lamination direction, and a side ground conductor layer (22) that extends along the extension direction of the signal line conductor layer (23) on the side of the signal line conductor layer (23) when the laminate is viewed in the lamination direction. One surface and the other surface of the conductor layer have different surface roughness. The surface of the signal line conductor layer (23) having the lower surface roughness faces the reference ground conductor layer (21). The surface of the side ground conductor layer (22) having the lower surface roughness does not face the reference ground conductor layer (21).

Description

Grounded coplanar waveguide and electronic device

[0001] The present invention relates to a grounded coplanar waveguide and an electronic device equipped with the grounded coplanar waveguide.

[0002] A transmission line for high-frequency signals formed on a laminated substrate generally has a structure including a reference ground conductor layer and a signal line conductor layer disposed opposite the reference ground conductor layer. As shown in Patent Document 1, a transmission line having additional ground conductor layers on the left and right of the signal line conductor layer along the extension direction is also used. A coplanar waveguide having side ground conductor layers on the left and right of the signal line conductor layer along the extension direction of the signal line conductor layer is also used.

[0003] Furthermore, a transmission line including a signal line conductor layer and a reference ground conductor layer facing the side ground conductor layer is also used. A waveguide utilizing the electric field generated between the signal line conductor layer and the side ground conductor layer, and the electric field generated between the signal line conductor layer and the reference ground conductor layer, is called a grounded coplanar waveguide. A grounded coplanar waveguide (G-CPW) is also called a conductor-backed coplanar waveguide (CB-CPW) or a grounded coplanar waveguide.

[0004] In general, in a grounded coplanar waveguide, the electric field generated between the signal line conductor layer and the reference ground conductor layer is as large as the electric field generated between the signal line conductor layer and the side ground conductor.

[0005] Japanese Patent Application Laid-Open No. 2018-121076

[0006] The grounded coplanar waveguide has the advantages of low-loss transmission, easy impedance setting, and the ability to be constructed on laminated substrates.

[0007] The inventors of the present invention have discovered further improvements in terms of transmission loss when constructing a grounded coplanar waveguide on a substrate having a plurality of insulator layers and conductor layers formed and bonded to surfaces along these insulator layers.

[0008] An object of the present invention is to provide a grounded coplanar waveguide that can easily reduce transmission loss, and an electronic device that includes this grounded coplanar waveguide.

[0009] When using conductor foil to form a conductor layer, it is difficult to ensure sufficient bonding strength between the conductor foil and the insulating sheet unless the conductor foil is roughened before bonding to the insulating sheet. On the other hand, if the conductor foil is roughened, an increase in skin resistance due to this roughening becomes a problem. The present invention provides a grounded coplanar waveguide with low transmission loss by reducing the loss due to the skin resistance of the conductor layer.

[0010] (1) A grounded coplanar waveguide as an example of the present disclosure is characterized in that a laminate is formed including a plurality of stacked insulator layers and conductor layers formed by bonding to surfaces of all or some of the insulator layers among the plurality of insulator layers, the conductor layers including a reference ground conductor layer, a signal line conductor layer overlapping the reference ground conductor layer when the laminate is viewed in the stacking direction, and a side ground conductor layer extending in an extension direction of the signal line conductor layer on a side of the signal line conductor layer when the laminate is viewed in the stacking direction, the conductor layer having different surface roughnesses on one side and the other side, the side of the signal line conductor layer with the smaller surface roughness facing the reference ground conductor layer, and the side of the side ground conductor layer with the smaller surface roughness facing the reference ground conductor layer.

[0011] (2) An electronic device as an example of the present disclosure includes an electronic circuit that uses the grounded coplanar waveguide as a signal transmission path.

[0012] According to the present invention, it is possible to obtain a grounded coplanar waveguide that ensures bonding strength between an insulator layer and a conductor layer and has low transmission loss, and an electronic device that includes this grounded coplanar waveguide.

[0013] FIG. 1A is a plan view showing the configuration of a grounded coplanar waveguide according to a first embodiment, before lamination of each layer. FIG. 1B is a cross-sectional view showing the configuration of a grounded coplanar waveguide according to the first embodiment, before lamination of each layer. FIG. 1C is a cross-sectional view of the grounded coplanar waveguide according to the first embodiment. FIG. 2A is a cross-sectional view taken along line Y1-Y1 in FIG. 1A, FIG. 2B is a cross-sectional view taken along line Y2-Y2 in FIG. 1A, FIG. 2C is a cross-sectional view taken along line Y3-Y3 in FIG. 1A, and FIG. 2D is a cross-sectional view taken along line Y4-Y4 in FIG. 1A. FIGS. 3A, 3B, 3C, and 3D are cross-sectional views of a grounded coplanar waveguide and its intermediate stages of manufacture. FIG. 4A is a partial plan view of the grounded coplanar waveguide shown in FIG. 1C, with components mounted on both ends. FIG. 4B is a cross-sectional view taken along line Y1-Y1 in FIG. 4A, and FIG. 4C is a cross-sectional view taken along line Y2-Y2 in FIG. 4A. FIG. 5 is a diagram showing the electric field intensity and its distribution (i.e., electric field density) between the signal line conductor layer and the reference ground conductor layer, and between the signal line conductor layer and the side ground conductor layer. FIG. 6A is a plan view showing the configuration of a grounded coplanar waveguide according to a second embodiment, before each layer is laminated. FIG. 6B is a cross-sectional view showing the configuration of a grounded coplanar waveguide according to the second embodiment, before each layer is laminated. FIG. 6C is a cross-sectional view of the grounded coplanar waveguide according to the second embodiment. FIG. 7 is a cross-sectional view taken along line Y1-Y1 in FIG. 6A. FIGS. 8A, 8B, and 8C are cross-sectional views of a grounded coplanar waveguide according to a third embodiment. Figures 9(A), 9(B), and 9(C) are cross-sectional views of a grounded coplanar waveguide according to a fourth embodiment. Figure 10 is a cross-sectional view of a grounded coplanar waveguide according to a fifth embodiment. Figures 11(A) and 11(B) are cross-sectional views of a grounded coplanar waveguide according to a sixth embodiment. Figures 12(A) and 12(B) are cross-sectional views of a grounded coplanar waveguide according to a seventh embodiment. Figure 13 is a cross-sectional view of a grounded coplanar waveguide according to an eighth embodiment.FIG. 14A is a plan view showing the configuration of a grounded coplanar waveguide according to a ninth embodiment, before layers are laminated. FIG. 14B is a cross-sectional view showing the configuration of a grounded coplanar waveguide according to the ninth embodiment, before layers are laminated. FIG. 14C is a cross-sectional view of the grounded coplanar waveguide according to the ninth embodiment. FIG. 15A is a cross-sectional view taken along line Y1-Y1 in FIG. 14A, FIG. 15B is a cross-sectional view taken along line Y2-Y2 in FIG. 14A, FIG. 15C is a cross-sectional view taken along line Y3-Y3 in FIG. 14A, and FIG. 15D is a cross-sectional view taken along line Y4-Y4 in FIG. 14A. FIG. 16 is a cross-sectional view of a grounded coplanar waveguide according to a tenth embodiment. FIGS. 17A, 17B, and 17C are cross-sectional views of grounded coplanar waveguides according to an eleventh embodiment. 18A, 18B, and 18C are plan views of three grounded coplanar waveguides according to a twelfth embodiment. Fig. 19 is a cross-sectional view of an electronic device according to a thirteenth embodiment. Fig. 20 is a scanning electron microscope photograph showing the difference in surface roughness between the upper and lower surfaces of a signal line conductor layer.

[0014] Hereinafter, several specific examples will be given with reference to the drawings to illustrate several embodiments for carrying out the present invention. The same reference numerals are used for the same parts in each drawing. To facilitate explanation and understanding of the main points, the embodiments for carrying out the present invention are shown divided into several embodiments for the sake of convenience. However, partial omission, substitution, or combination of the configurations shown in different embodiments is possible. From the second embodiment onwards, descriptions of matters common to the first embodiment will be omitted, and only the differences will be described. In particular, similar effects resulting from similar configurations will not be mentioned in each embodiment.

[0015] In the present invention and in this embodiment, "resin" means a synthetic resin unless otherwise specified.

[0016] First Embodiment Fig. 1(A) is a plan view showing the configuration of a grounded coplanar waveguide according to a first embodiment before layers are laminated. Fig. 1(B) is a cross-sectional view of each layer before lamination, showing the configuration of the grounded coplanar waveguide according to the first embodiment. Fig. 1(C) is a cross-sectional view of a grounded coplanar waveguide 101 according to the first embodiment. Both Fig. 1(B) and Fig. 1(C) are cross-sectional views taken along the line X-X in Fig. 1(A).

[0017] Fig. 2(A) is a cross-sectional view taken along line Y1-Y1 in Fig. 1(A), Fig. 2(B) is a cross-sectional view taken along line Y2-Y2 in Fig. 1(A), Fig. 2(C) is a cross-sectional view taken along line Y3-Y3 in Fig. 1(A), and Fig. 2(D) is a cross-sectional view taken along line Y4-Y4 in Fig. 1(A). Of course, all of these are cross-sectional views after the layers have been stacked to form a laminate (in a state where the grounded coplanar waveguide 101 has been constructed).

[0018] In each cross-sectional view, lines that appear in the cross section (appearing due to cutting) are drawn, and lines that exist behind the cross section are not shown. This also applies to each embodiment described later. Furthermore, the directional symbols X, Y, and Z in each view merely indicate the direction from which each view is taken, and are not symbols that indicate the origin of the three orthogonal axes.

[0019] Although each figure shows a single grounded coplanar waveguide, in the intermediate stage of manufacturing such a single grounded coplanar waveguide, the continuous grounded coplanar waveguide is singulated by cutting the continuous grounded coplanar waveguide at the final stage of the manufacturing process or just before the final stage. This relationship between the continuous grounded coplanar waveguide and the singulation is the same in the other figures.

[0020] In the first embodiment, the grounded coplanar waveguide 101 includes three insulator layers 11, 12, and 13. Various conductor layers are bonded to one surface of the insulator layers 11, 12, and 13. Each conductor layer has a first main surface S1 and a second main surface S2 opposite to the first main surface S1. The surface roughness of the first main surface S1 of each conductor layer is different from the surface roughness of the second main surface S2. In each figure, a surface with a relatively rough surface is represented as a surface with simple, fine, rectangular protrusions dispersed (arranged in a cross section).

[0021] As shown in Fig. 1B, a signal line conductor layer 23 is provided on the insulator layer 13. As shown in Fig. 1A, the signal line conductor layer 23 is a conductor pattern that extends in the X direction with a constant width. Both ends of this signal line conductor layer 23 act as signal electrodes. This signal electrode will be described in detail later. In this specification, the term "signal line conductor layer" does not refer to a layer on which the signal line conductor is formed or a layer on which the signal line conductor is to be formed, but refers to the signal line conductor itself.

[0022] 1A and 1B , a reference ground conductor layer 21 is provided on the insulator layer 11. Furthermore, a side ground conductor layer 22 is provided on the insulator layer 12. The reference ground conductor layer 21 is a conductor layer formed substantially over one entire surface of the insulator layer 11. The side ground conductor layer 22 is provided on the side of the signal line conductor layer 23 in a position parallel to and along the signal line conductor layer 23 when viewed in the stacking direction (Z direction) of the laminate. In the example shown in FIG. 1A , the side ground conductor layer 22 has a shape that surrounds the peripheries of multiple openings 12H. This shape keeps the side ground conductor layers parallel to and along the signal line conductor layer 23 on both sides of the signal line conductor layer 23 at the same potential (ground potential).

[0023] The insulator layer 12 has a plurality of openings 12H arranged along the extending direction of the signal line conductor layer 23. In this example, the openings 12H are cylindrical openings that penetrate the insulator layer 12 in its thickness direction.

[0024] The openings 12H (see FIGS. 1A and 1B) formed in the insulator layer 12 form hollow spaces HS (see FIGS. 1C and 2B) in the laminated state of the insulator layers 11, 12, and 13 on which various conductor layers are formed. That is, each hollow space HS is a cylindrical space filled with air.

[0025] As shown in Fig. 1A, a plurality of openings 13H (eight in the example shown in Fig. 1A) are formed in the insulator layer 13. Of these openings 13H, two openings 13H expose both ends of the signal line conductor layer 23, and six openings 13H expose portions of the side ground conductor layer 22. These exposed portions form electrodes for mounting components. These mounted components will be described in detail later.

[0026] The openings 12H and 13H are resin removal portions. A resist mask pattern is formed in the portions where resin removal is not to be performed, and the resin is removed by, for example, irradiating the resist mask with laser light, immersing the resist mask in an alkaline solution, or by drilling or punching, thereby forming the openings 12H and 13H.

[0027] The signal line conductor layer 23 faces the main ground conductor layer 21 in the thickness direction of the insulator layer 12. In the first embodiment, the signal line conductor layer 23 and the main ground conductor layer 21 face each other with the insulator layer 12 interposed therebetween.

[0028] The side ground conductor layer 22 faces the main ground conductor layer 21 in the thickness direction of the insulator layer 12. In the first embodiment, the side ground conductor layer 22 and the main ground conductor layer 21 face each other with the insulator layer 12 interposed therebetween.

[0029] The side ground conductor layers 22 are arranged at a predetermined distance in the left-right direction (Y direction) from the signal line conductor layer 23 and along the extending direction (X direction) of the signal line conductor layer 23 .

[0030] The conductor layers 21, 22, and 23 have different surface roughnesses between a first main surface S1 bonded to the insulator layers 11, 12, and 13 and a second main surface S2 opposite the first main surface S1. The first main surface S1 of the main ground conductor layer 21, the side ground conductor layer 22, and the signal line conductor layer 23 is rougher than the second main surface S2. This increases the bonding strength of the main ground conductor layer 21 to the insulator layer 11, the side ground conductor layer 22 to the insulator layer 12, and the signal line conductor layer 23 to the insulator layer 13.

[0031] As shown in Figures 1(B), 1(C), 2(A), 2(B), 2(C), and 2(D), the positional relationship of the surface roughness of each conductor layer is as follows:

[0032] (a) The surface of the signal line conductor layer 23 with the small surface roughness (the second main surface S2 of the signal line conductor layer 23) is the surface facing the main ground conductor layer 21.

[0033] (b) The surface of the side ground conductor layer 22 with the small surface roughness (the second main surface S2 of the side ground conductor layer 22) does not face the main ground conductor layer 21.

[0034] (c) The surface of the main ground conductor layer 21 with the greatest surface roughness (the first main surface S1 of the main ground conductor layer 21 ) is the surface that does not face the signal line conductor layer 23 .

[0035] 3A, 3B, and 3C are cross-sectional views of the grounded coplanar waveguide 101 during its manufacture. Fig. 3D is a cross-sectional view of the grounded coplanar waveguide 101. All of these are cross-sectional views taken along the line Y2-Y2 in Fig. 1A.

[0036] 3A , first, a conductor layer bonded to the insulator layer 11 is formed to form the reference ground conductor layer 21. A conductor layer bonded to the insulator layer 12 is formed to form the side ground conductor layer 22. A conductor layer bonded to the insulator layer 13 is formed to form the signal line conductor layer 23. The insulator layers 11, 12, and 13 are made of a thermoplastic resin such as LCP, which has a low dielectric constant and dielectric loss tangent. The conductor layers 21, 22, and 23 are made of a metal foil, such as copper foil or aluminum foil.

[0037] The first main surfaces S1 (see FIG. 1) of the main ground conductor layer 21, the side ground conductor layer 22, and the signal line conductor layer 23 are roughened surfaces formed by roughening the surfaces of the metal foils.

[0038] Next, as shown in FIG. 3B , the insulator layer 12 having the side ground conductor layer 22 formed thereon is stacked on the insulator layer 11 having the main ground conductor layer 21 formed thereon, and the bonding surfaces are bonded together by applying pressure and heat.

[0039] 3C, an opening 12H is formed in the insulator layer 12. For example, the opening 12H can be formed by laser cutting or wet etching. At this stage, an interlayer connection conductor (the interlayer connection conductor 4 shown in FIGS. 2A and 2C) that electrically connects the main ground conductor layer 21 and the side ground conductor layer 22 is formed by electroplating or the like.

[0040] Thereafter, as shown in FIG. 3D, the insulator layer 13 on which the signal line conductor layer 23 is formed is laminated on the insulator layer 12, and the bonding surfaces are bonded by applying pressure and heat.

[0041] 1C, 2C, and 2D, an opening 13H is formed in the insulator layer 13. For example, the opening 13H is formed by cutting using a laser or removing using a wet etching process. As a result, the exposed portion of the signal line conductor layer 23 is formed as the signal electrode 23E. Also, the exposed portion of the side ground conductor layer 22 is formed as the ground electrode 22E.

[0042] In this manner, the grounded coplanar waveguide 101 is manufactured.

[0043] Here, examples of the surface roughness of each surface of the main ground conductor layer 21, the side ground conductor layer 22, and the signal line conductor layer 23 are shown. Fig. 20 is a scanning electron microscope photograph showing the difference in surface roughness between the top and bottom surfaces of the signal line conductor layer 23.

[0044] The signal line conductor layer 23, the reference ground conductor layer 21, and the side ground conductor layer 22 are all made of Cu foil, but the glossiness of the glossy surface and the roughness of the roughened surface are different. In the example shown in Figure 20, the lower surface (glossy surface) of the signal line conductor layer 23 has a smaller difference in elevation over a short period (per short distance along the surface) and a higher glossiness than the upper surface (roughened surface) of the signal line conductor layer 23. The "difference in elevation over a short period" here does not refer to, for example, the difference between the maximum height (maximum thickness) and the minimum height (minimum thickness) over the entire range of the line width of the signal line conductor layer, but rather refers to the difference in elevation in increments of 10 μm. When considering this difference in elevation in increments of 10 μm, the surface with the smaller difference in elevation is the glossy surface, and the surface with the larger difference in elevation is the roughened surface.

[0045] In this way, the glossy surfaces of the signal line conductor layer and the glossy surface of the reference ground conductor layer 21 effectively increase the transmission loss of high frequency signals due to the skin resistance of the conductor layers.

[0046] On the other hand, the lower surfaces (roughened surfaces) of the main ground conductor layer 21 and the side ground conductor layers 22 have a rougher surface than the upper surfaces (roughened surfaces) of the signal line conductor layers 23. This results in strong adhesion between the main ground conductor layer 21 and the insulator layer 11. Similarly, the side ground conductor layers 22 have strong adhesion between the insulator layer 12. Furthermore, the upper surfaces (glossy surfaces) of the main ground conductor layer 21 and the side ground conductor layers 22 have a certain degree of roughness. This results in strong adhesion between the main ground conductor layer 21 and the insulator layer 12. Similarly, the side ground conductor layers 22 have strong adhesion between the insulator layer 13.

[0047] These scanning electron microscope (SEM) photographs were taken in the following manner.

[0048] (1) The cross section is mechanically polished until the hollow portion HS appears as shown in FIG. 2(B).

[0049] (2) The hollow portion HS is filled with resin.

[0050] (3) After the resin has hardened, the cross section is again mechanically polished.

[0051] (4) The observation surface is subjected to CP processing (ion milling) using an ion milling device (Hitachi High-Tech IM4000).

[0052] (5) A conductor coating is applied to the observation surface using a conductor film coater.

[0053] (6) SEM photographs are taken using a scanning electron microscope (Hitachi High-Tech FlexSEM1000).

[0054] The interlayer connection conductors 4 are arranged at predetermined intervals in the extension direction of the signal line conductor layer 23. It is preferable that these intervals be narrow enough to prevent electromagnetic waves in the frequency band of high-frequency signals propagating through the grounded coplanar waveguide from leaking sideways (in the Y direction).

[0055] Fig. 4A is a partial plan view showing the state in which components 9 are mounted on both ends of the grounded coplanar waveguide 101 shown in Fig. 1C. Fig. 4B is a cross-sectional view taken along line Y1-Y1 in Fig. 4A, and Fig. 4C is a cross-sectional view taken along line Y2-Y2 in Fig. 4A.

[0056] The mounting component 9 is, for example, one side of a connector. The mounting component 9 has three protruding ground terminals 9G and one signal terminal 9S. This connector is, for example, a coaxial connector, but the electrodes of the connector are not shown in Figure 4(A).

[0057] 4B, a ground electrode 22E is an exposed portion of the side ground conductor layer 22. A ground terminal 9G of the mounted component is joined to the ground electrode 22E with solder S.

[0058] 4C, the exposed portion of the signal line conductor layer 23 is a signal electrode 23E. A signal terminal 9S of the mounted component is joined to the signal electrode 23E with solder S.

[0059] To explain the features of the grounded coplanar waveguide of this embodiment, a typical electric field density distribution in a grounded coplanar waveguide will first be described with reference to FIG. 5 . FIG. 5 is a diagram showing the electric field intensity and its distribution (i.e., electric field density) between the signal line conductor layer 23 and the reference ground conductor layer 21, and between the signal line conductor layer 23 and the side ground conductor layer 22. The arrows in the diagram indicate the electric field direction, and the length of the arrows indicates the electric field intensity. The signal line conductor layer 23, the reference ground conductor layer 21, and the side ground conductor layer 22 are disposed within a dielectric. The reference ground conductor layer 21 and the side ground conductor layer 22 are electrically connected by a plurality of interlayer connection conductors 4.

[0060] The signal line conductor layer 23 and the reference ground conductor layer 21 face each other at a relatively short distance, resulting in a high electric field density therebetween. The signal line conductor layer 23 and the side ground conductor layer 22 are located on the same or substantially the same layer at a relatively short distance, resulting in a high electric field density within the same or substantially the same layer. The reference ground conductor layer 21 extends below the side ground conductor layer 22, resulting in a low electric field density on the bottom surface of the side ground conductor layer 22 (the surface facing the reference ground conductor layer 21). On the other hand, the electric field flows around the top surface of the side ground conductor layer 22 (the surface not facing the reference ground conductor layer 21), resulting in a high electric field density between the top surface of the signal line conductor layer 23 and the top surface of the side ground conductor layer 22. Therefore, the electric field density is higher near the top surface of the side ground conductor layer 22 than near the bottom surface of the side ground conductor layer 22.

[0061] Although FIG. 5 shows a cross section in which there is no hollow portion between the signal line conductor layer 23 and the reference ground conductor layer 21, even if there is a hollow portion (hollow portion HS shown in FIG. 2B ), the relationship in which the electric field density is higher near the top surface of the side ground conductor layer 22 than near the bottom surface remains the same.

[0062] The effects of the surface roughness structure of each conductor layer of the grounded coplanar waveguide 101 in the first embodiment are as follows.

[0063] (a) In the grounded coplanar waveguide 101 of this embodiment, the surface of the signal line conductor layer 23 with the small surface roughness (the second principal surface S2) is the surface facing the reference ground conductor layer 21. Although the electric field density is high near the second principal surface S2 of the signal line conductor layer 23, the surface roughness of this surface is small, so that the transmission loss of high-frequency signals due to skin resistance is small on the first principal surface S1 of the signal line conductor layer 23. Conversely, the electric field density is low near the first principal surface S1 of the signal line conductor layer 23, so that the transmission loss of high-frequency signals due to skin resistance is small on the first principal surface S1 of the signal line conductor layer 23.

[0064] (b) The surface with the small surface roughness (the second principal surface S2) of the side ground conductor layer 22 is the surface that does not face the reference ground conductor layer 21. Therefore, although the electric field density near this second principal surface S2 is higher than that near the first principal surface S1, the transmission loss of high-frequency signals due to the skin resistance on the second principal surface S2 of the side ground conductor layer 22 is small.

[0065] (c) The surface of the main ground conductor layer 21 with the greatest surface roughness is the surface (first principal surface S1) that does not face the signal line conductor layer 23. Therefore, the transmission loss of high-frequency signals on the first principal surface S1 of the main ground conductor layer 21 due to skin resistance is small.

[0066] According to the first embodiment, a grounded coplanar waveguide with low transmission loss due to the skin resistance of the conductor layers can be obtained while maintaining the bonding strength of the laminate due to the conductor layers having high surface roughness. Furthermore, since the hollow space HS between the signal line conductor layer 23 and the reference ground conductor layer 21 is filled with air, the dielectric constant between the signal line conductor layer 23 and the reference ground conductor layer 21 is low, and the dielectric loss tangent is small, resulting in a grounded coplanar waveguide with low transmission loss due to dielectric loss. Furthermore, since the signal line conductor layer 23 is formed on the insulator layer 13, an interlayer connection conductor that is electrically connected to the signal line conductor layer 23 is not required. It is sufficient to provide the interlayer connection conductor only on the insulator layer 12. This reduces the number of processing steps and reduces manufacturing costs. Furthermore, since the current flowing (propagating) through the signal line conductor layer 23 is conducted without passing through the interlayer connection conductor, there is no loss in the interlayer connection conductor, thereby reducing transmission loss.

[0067] Second Embodiment In a second embodiment, a grounded coplanar waveguide without a hollow portion will be exemplified.

[0068] Fig. 6(A) is a plan view showing the configuration of a grounded coplanar waveguide according to a second embodiment before layers are laminated. Fig. 6(B) is a cross-sectional view of each layer before layers are laminated, showing the configuration of a grounded coplanar waveguide according to the second embodiment. Fig. 6(C) is a cross-sectional view of a grounded coplanar waveguide 102 according to the second embodiment. Both Fig. 6(B) and Fig. 6(C) are cross-sectional views taken along the line X-X in Fig. 6(A).

[0069] 7 is a cross-sectional view taken along the line Y1-Y1 in FIG. 6A. Of course, this is a cross-sectional view after lamination (after the grounded coplanar waveguide 102 has been formed).

[0070] The grounded coplanar waveguide 102 according to the second embodiment differs from the grounded coplanar waveguide 101 shown in the first embodiment in that the insulator layer 12 does not have an opening 12H. In other words, no hollow portion HS is formed inside the grounded coplanar waveguide 102. The other configurations are the same as those shown in the first embodiment.

[0071] According to the second embodiment, similarly to the first embodiment, a grounded coplanar waveguide can be obtained that has low transmission loss due to the skin resistance of the conductor layer while maintaining the bonding strength of the laminate due to the conductor layer having a large surface roughness.

[0072] Third Embodiment In a third embodiment, a grounded coplanar waveguide in which the roughened surface of the reference ground conductor layer 21 is different from that in the first and second embodiments will be described as an example.

[0073] FIG. 8A is a cross-sectional view of a grounded coplanar waveguide 103A according to the third embodiment, FIG. 8B is a cross-sectional view of a grounded coplanar waveguide 103B according to the third embodiment, and FIG. 8C is a cross-sectional view of a grounded coplanar waveguide 103C according to the third embodiment.

[0074] FIG. 8A is a cross-sectional view of a grounded coplanar waveguide 103A at a position corresponding to the cross-sectional position of the grounded coplanar waveguide 101 shown in FIG. 2B in the first embodiment.

[0075] In the grounded coplanar waveguide 103A shown in Fig. 8A, conductor foils are bonded to both sides of the insulator layer 12, forming the respective conductor foils. A side ground conductor layer 22 is formed by forming (patterning) the conductor foil on the upper surface of the insulator layer 12. Furthermore, a reference ground conductor layer 21 is formed by patterning the conductor foil on the lower surface of the insulator layer 12. No conductor layer is present on the insulator layer 11, at least at the cross-sectional position shown in Fig. 8A.

[0076] A grounded coplanar waveguide 103B shown in FIG. 8B is an example in which the insulator layer 11 shown in FIG. 8A does not exist.

[0077] In the grounded coplanar waveguide 103C shown in FIG. 8C, there is no insulator layer of the same material on the surface of the insulator layer 12 (the bottom surface in FIG. 8C), and the bottom surface of the insulator layer 12 is coated with a protective film 3 of a different material.

[0078] According to the third embodiment, a double-sided conductor foil-clad substrate is used in part, so that the main ground conductor layer 21 and the side ground conductor layers 22 can be formed on fewer insulating layers overall, thereby reducing processing costs.

[0079] Fourth Embodiment In a fourth embodiment, a grounded coplanar waveguide in which a plurality of insulating layers exist between the reference ground conductor layer 21 and the signal line conductor layer 23 will be exemplified.

[0080] 9A is a cross-sectional view of a grounded coplanar waveguide 104A according to the fourth embodiment, FIG. 9B is a cross-sectional view of a grounded coplanar waveguide 104B according to the fourth embodiment, and FIG. 9C is a cross-sectional view of a grounded coplanar waveguide 104C according to the fourth embodiment, all of which are cross-sectional views taken at a position corresponding to the cross-sectional position of the grounded coplanar waveguide 101 shown in FIG. 2B in the first embodiment.

[0081] 9A, similarly to the grounded coplanar waveguide 101 shown in the first embodiment, a reference ground conductor layer 21 is formed on the upper surface of the insulator layer 11, a side ground conductor layer 22 is formed on the upper surface of the insulator layer 12, and a signal line conductor layer 23 is formed on the lower surface of the insulator layer 13. Unlike the grounded coplanar waveguide 101 shown in the first embodiment, the grounded coplanar waveguide 104A additionally has an insulator layer 14 inserted between the insulator layer 11 and the insulator layer 12.

[0082] 9B , similarly to the grounded coplanar waveguide 101 shown in the first embodiment, a reference ground conductor layer 21 is formed on the upper surface of the insulator layer 11, a side ground conductor layer 22A is formed on the upper surface of the insulator layer 12, and a signal line conductor layer 23 is formed on the lower surface of the insulator layer 13. Unlike the grounded coplanar waveguide 101 shown in the first embodiment, the grounded coplanar waveguide 104B further includes an insulator layer 14 between the insulator layer 11 and the insulator layer 12. A side ground conductor layer 22B is formed on the upper surface of this insulator layer 14. The reference ground conductor layer 21 and the side ground conductor layers 22A and 22B are electrically connected via the interlayer connection conductor 4.

[0083] 9C , a reference ground conductor layer 21 is formed on the lower surface of the insulator layer 11, a side ground conductor layer 22 is formed on the upper surface of the insulator layer 12, and a signal line conductor layer 23 is formed on the lower surface of the insulator layer 13. Unlike the grounded coplanar waveguide 101 shown in the first embodiment, the grounded coplanar waveguide 104C has the reference ground conductor layer 21 formed on the lower surface of the insulator layer 11, and an insulator layer 14 is added to the lower surface of this insulator layer 11. The reference ground conductor layer 21 and the side ground conductor layer 22 are electrically connected via the interlayer connection conductor 4.

[0084] According to the fourth embodiment, the number of insulator layers between the signal line conductor layer 23 and the reference ground conductor layer 21 is large, so that the thickness of the insulator layers between the signal line conductor layer 23 and the reference ground conductor layer 21 can be increased to a predetermined thickness even when using only thin insulator layers. Furthermore, since it is possible to form a conductor pattern on each insulator layer and bond this conductor pattern to the insulator layer, a predetermined circuit can be configured by forming a conductor pattern on the insulator layer. Furthermore, as shown in the example in FIG. 9B , by electrically connecting the multiple side ground conductor layers 22A, 22B using the interlayer connection conductor 4 that passes through the insulating layers, the ground conductor is expanded in the thickness direction (the stacking direction of the insulator layers), thereby improving the shielding performance for the signal line conductor layer 23.

[0085] Furthermore, by increasing the thickness of the insulator layer between the signal line conductor layer 23 and the reference ground conductor layer 21 to a predetermined thickness, the electric field density between the signal line conductor layer 23 and the reference ground conductor layer 21 is reduced, reducing the dielectric loss therebetween and effectively reducing transmission loss. Furthermore, the line width of the signal line conductor layer 23 is increased to optimize the capacitance between the signal line conductor layer 23 and the reference ground conductor layer 21, thereby reducing the conductor loss of the signal line conductor layer 23 and effectively reducing transmission loss.

[0086] Fifth Embodiment In a fifth embodiment, a grounded coplanar waveguide in which insulator layers adjacent in the stacking direction are bonded together via an adhesive layer will be exemplified.

[0087] 10 is a cross-sectional view of a grounded coplanar waveguide 105 according to the fifth embodiment. The cross-sectional position corresponds to the cross-sectional position of the grounded coplanar waveguide 101 shown in FIG. 2B in the first embodiment.

[0088] In the grounded coplanar waveguide 105, similarly to the grounded coplanar waveguide 101 shown in the first embodiment, a reference ground conductor layer 21 is formed on the upper surface of the insulator layer 11, a side ground conductor layer 22 is formed on the upper surface of the insulator layer 12, and a signal line conductor layer 23 is formed on the lower surface of the insulator layer 13.

[0089] The insulator layer 11 on which the main ground conductor layer 21 is formed and the insulator layer 12 on which the side ground conductor layer 22 is formed are bonded together via an adhesive layer 51. The insulator layer 12 on which the side ground conductor layer 22 is formed and the insulator layer 13 on which the signal line conductor layer 23 is formed are bonded together via an adhesive layer 52.

[0090] The grounded coplanar waveguide 105 is manufactured, for example, as follows.

[0091] First, the main ground conductor layer 21 is formed on the insulator layer 11 , and the side ground conductor layer 22 is formed on the insulator layer 12 .

[0092] Next, the insulator layer 11 on which the main ground conductor layer 21 is formed and the insulator layer 12 on which the side ground conductor layer 22 is formed are bonded together via an adhesive layer 51 .

[0093] Next, an opening for forming the hollow portion HS is formed in the insulator layer 12. Also, a via hole is opened and the inside of the via hole is plated to form the interlayer connection conductor 4.

[0094] Thereafter, the insulator layer 12 on which the side ground conductor layer 22 is formed and the insulator layer 13 are bonded together via the adhesive layer 52 .

[0095] At an initial stage when the adhesive layers 51 and 52 are in a film state, openings for forming part of the hollow portion HS may be formed in the adhesive layers 51 and 52 .

[0096] The insulator layers 11, 12, and 13 are made of a resin with a low dielectric constant and dielectric loss tangent, such as LCP, MPI, PI, or PTFE. The adhesive layers 51 and 52 are made of a thermosetting resin, such as an epoxy resin or an acrylic resin. While the adhesive layers 51 and 52 may be applied to the surfaces of the insulator layers, it is preferable to heat the layers after laminating them in film form. This facilitates uniform spacing between the main ground conductor layer 21 and the signal line conductor layer 23, and between the main ground conductor layer 21 and the side ground conductor layer 22.

[0097] As described above, in the fifth embodiment, the insulating layers 11, 12, and 13 are laminated via the adhesive layers 51 and 52 made of a material different from that of the insulating layers 11, 12, and 13.

[0098] According to the fifth embodiment, the pressure required for bonding the conductor layer and the insulator layer or the insulator layers together is small, so deformation of the hollow space HS is small, which makes it easier to stabilize the electrical characteristics of the waveguide.

[0099] Sixth Embodiment In a sixth embodiment, a grounded coplanar waveguide in which the hollow portion does not reach the reference ground conductor layer will be exemplified.

[0100] 11A is a cross-sectional view of a grounded coplanar waveguide 106A according to the sixth embodiment, and FIG. 11B is a cross-sectional view of a grounded coplanar waveguide 106B according to the sixth embodiment, both of which are cross-sectional views taken at a position corresponding to the cross-sectional position of the grounded coplanar waveguide 101 shown in FIG. 2B according to the first embodiment.

[0101] 11A , similar to the grounded coplanar waveguide 104A described in the fourth embodiment, a reference ground conductor layer 21 is formed on the upper surface of the insulator layer 11, a side ground conductor layer 22 is formed on the upper surface of the insulator layer 12, and a signal line conductor layer 23 is formed on the lower surface of the insulator layer 13. An insulator layer 14 is laminated between the insulator layer 11 and the insulator layer 12. However, no opening is formed in the insulator layer 14. With this structure, the hollow space HS exists only midway between the signal line conductor layer 23 and the reference ground conductor layer 21. In other words, the hollow space HS does not reach from the signal line conductor layer 23 to the reference ground conductor layer 21.

[0102] 11B , a reference ground conductor layer 21 is formed on the upper surface of the insulator layer 11, a side ground conductor layer 22 is formed on the upper surface of the insulator layer 12, and a signal line conductor layer 23 is formed on the lower surface of the insulator layer 13. A non-penetrating opening is formed in the insulator layer 12, and a hollow space HS is formed by laminating the insulator layers 12 and 13. In other words, the hollow space HS does not reach from the signal line conductor layer 23 to the reference ground conductor layer 21.

[0103] In this way, even in a grounded coplanar waveguide in which the hollow portion HS does not reach the reference ground conductor layer 21, the hollow portion HS exists in the portion with high electric field density, and therefore the loss reduction effect of the hollow portion HS can be utilized.

[0104] According to the sixth embodiment, the main ground conductor layer 21 is covered with an insulating layer, and therefore the main ground conductor layer 21 has high corrosion resistance.

[0105] Furthermore, in the grounded coplanar waveguide 106B shown in FIG. 11B, the number of self-adhesive layers between the insulating layers is small, so high-temperature, high-pressure press processing is not required, and in that respect processing is easy.

[0106] Seventh Embodiment In the seventh embodiment, a grounded coplanar waveguide including a plurality of signal line conductor layers will be illustrated.

[0107] FIG. 12A is a cross-sectional view of a grounded coplanar waveguide 107A according to the seventh embodiment, and FIG. 12B is a cross-sectional view of a grounded coplanar waveguide 107B according to the seventh embodiment.

[0108] 12A shows a grounded coplanar waveguide 107A having a reference ground conductor layer 21 formed on the upper surface of the insulator layer 11, side ground conductor layers 22A, 22B, and 22C formed on the upper surface of the insulator layer 12, and two signal line conductor layers 23A and 23B formed on the lower surface of the insulator layer 13. In this grounded coplanar waveguide 107A, the side ground conductor layer 22C is disposed between the signal line conductor layer 23A and the signal line conductor layer 23B. That is, the signal line conductor layer 23A and the signal line conductor layer 23B are shielded by the side ground conductor layer 22C therebetween. In this way, a plurality of signal line conductor layers may be provided while shielding the spaces between adjacent signal line conductor layers.

[0109] 12B , a grounded coplanar waveguide 107B has a reference ground conductor layer 21 formed on the lower surface of the insulator layer 11, a side ground conductor layer 22A formed on the lower surface of the insulator layer 12A, and a signal line conductor layer 23A formed on the upper surface of the insulator layer 13A. Furthermore, a side ground conductor layer 22B is formed on the upper surface of the insulator layer 12B, and a signal line conductor layer 23B is formed on the lower surface of the insulator layer 13B. An insulator layer 14 is laminated between the insulator layer 12A and the insulator layer 11.

[0110] Openings are formed in the insulator layers 12A and 14, and these openings form a hollow space HSA between the reference ground conductor layer 21 and the insulator layer 13A. Also, an opening is formed in the insulator layer 12B, and this opening forms a hollow space HSB between the insulator layer 11 and the insulator layer 13B.

[0111] In this way, the signal line conductor layers may be arranged in the stacking direction of the insulating layers, and adjacent signal line conductor layers in the stacking direction may be shielded by the reference ground conductor layer therebetween.

[0112] According to the seventh embodiment, a transmission path capable of transmitting a plurality of signals can be configured, and a differential signal waveguide that transmits opposite phase signals using two signal line conductor layers can be configured.

[0113] Eighth Embodiment In the eighth embodiment, a grounded coplanar waveguide having a side ground conductor layer on only one side of a signal line conductor layer will be exemplified.

[0114] FIG. 13 is a cross-sectional view of a grounded coplanar waveguide 108 according to the eighth embodiment.

[0115] The grounded coplanar waveguide 108 has a reference ground conductor layer 21 formed on the upper surface of its insulator layer 11, a side ground conductor layer 22 formed on the upper surface of its insulator layer 12, and a signal line conductor layer 23 formed on the lower surface of its insulator layer 13.

[0116] The grounded coplanar waveguide 108 according to the eighth embodiment differs from the grounded coplanar waveguide 101 according to the first embodiment shown in FIG. 2B in that a side ground conductor layer 22 is formed only on one side of the signal line conductor layer 23.

[0117] In this way, the present invention can also be applied to a grounded coplanar waveguide in which the side ground conductor layers are arranged along the extension direction of the signal line conductor layers, either to the left or right of the signal line conductor layers.

[0118] Ninth Embodiment In the ninth embodiment, a grounded coplanar waveguide having a signal line conductor layer with a different thickness will be illustrated, compared to the grounded coplanar waveguide shown in the first embodiment.

[0119] Fig. 14(A) is a plan view showing the configuration of a grounded coplanar waveguide according to the ninth embodiment before layers are laminated. Fig. 14(B) is a cross-sectional view of each layer before layers are laminated, showing the configuration of a grounded coplanar waveguide according to the ninth embodiment. Fig. 14(C) is a cross-sectional view of a grounded coplanar waveguide 109 according to the ninth embodiment. Both Fig. 14(B) and Fig. 14(C) are cross-sectional views taken along the line X-X in Fig. 14(A).

[0120] 15(A) is a cross-sectional view taken along Y1-Y1 in FIG. 14(A), FIG. 15(B) is a cross-sectional view taken along Y2-Y2 in FIG. 14(A), FIG. 15(C) is a cross-sectional view taken along Y3-Y3 in FIG. 14(A), and FIG. 15(D) is a cross-sectional view taken along Y4-Y4 in FIG. 14(A).

[0121] The basic structure of the grounded coplanar waveguide 109 of the ninth embodiment is similar to that of the grounded coplanar waveguide 101 of the first embodiment, except for the relative relationship between the thickness of the signal line conductor layer 23 and the thicknesses of the side ground conductor layer 22 and the reference ground conductor layer 21.

[0122] The signal line conductor layer 23 of the grounded coplanar waveguide 109 is thicker than the side ground conductor layer 22. The signal line conductor layer 23 of the grounded coplanar waveguide 109 is also thicker than the reference ground conductor layer 21.

[0123] According to this embodiment, even though the thickness of the grounded coplanar waveguide (product thickness) is the same, the thicker signal line conductor layer 23 reduces conductor loss and allows the waveguide to be used as a waveguide with low transmission loss. Furthermore, the thicker signal line conductor layer effectively suppresses deformation of the signal line conductor layer portion, making it easier to obtain a waveguide with stable electrical characteristics.

[0124] Tenth Embodiment In the tenth embodiment, a grounded coplanar waveguide having a signal line conductor layer with a different thickness will be illustrated, compared to the grounded coplanar waveguide shown in the first embodiment.

[0125] 16 is a cross-sectional view of a grounded coplanar waveguide 110 according to the tenth embodiment. The cross-sectional position shown in this Fig. 16 corresponds to the cross-sectional position along Y2-Y2 shown in Fig. 14 in the ninth embodiment.

[0126] In the grounded coplanar waveguide 110, not only is the signal line conductor layer 23 thicker than the side ground conductor layer 22, but the reference ground conductor layer 21 is also thicker than the side ground conductor layer 22. In other words, the side ground conductor layer 22 is thinner than the signal line conductor layer 23 and the reference ground conductor layer 21.

[0127] According to this embodiment, a transmission line with a thin overall thickness can be obtained due to the thin thickness of the side ground conductor layer 22. Furthermore, by ensuring the thickness of the reference ground conductor layer 21, which has a high current density, electrical characteristics such as conductor loss can be maintained.

[0128] Eleventh Embodiment In the eleventh embodiment, a grounded coplanar waveguide is illustrated in which the distance in the thickness direction between the signal line conductor layer and the side ground conductor layer is greater than in the examples shown so far. The eleventh embodiment also illustrates a grounded coplanar waveguide having a resin sheet with conductor layers formed on both sides of an insulating layer. The eleventh embodiment also illustrates a grounded coplanar waveguide having portions where resin sheets are bonded together with an adhesive.

[0129] Fig. 17A is a cross-sectional view of a grounded coplanar waveguide 111A according to the eleventh embodiment, Fig. 17B is a cross-sectional view of another grounded coplanar waveguide 111B according to the eleventh embodiment, and Fig. 17C is a cross-sectional view of another grounded coplanar waveguide 111C according to the eleventh embodiment.

[0130] The grounded coplanar waveguide 111A includes four insulator layers 11, 12, 13, and 14. Various conductor layers are bonded to one surface of the insulator layers 11, 13, and 14. Each conductor layer has a first main surface S1 and a second main surface S2 opposite to the first main surface S1. The surface roughness of the first main surface S1 of each conductor layer is different from the surface roughness of the second main surface S2.

[0131] 17A, a grounded coplanar waveguide 111A has a reference ground conductor layer 21 formed on the top surface of the insulator layer 11, a signal line conductor layer 23 formed on the bottom surface of the insulator layer 13, and a side ground conductor layer 22 formed on the bottom surface of the insulator layer 14. No conductor layers are formed on the top and bottom surfaces of the insulator layer 12. An opening is formed in the insulator layer 12, and a hollow space HS is formed in the opening by laminating other insulator layers and conductor layers thereon.

[0132] The insulating layers 11, 13, and 14 on which the various conductor layers are formed are stacked on the insulating layer 12, and the stack is formed by applying pressure and heat.

[0133] An interlayer connection conductor 4 is formed between the main ground conductor layer 21 and the side ground conductor layer 22 .

[0134] 17(B), a grounded coplanar waveguide 111B has a reference ground conductor layer 21 formed on the top surface of the insulator layer 11, a side ground conductor layer 22A formed on the top surface of the insulator layer 12, a signal line conductor layer 23 formed on the bottom surface of the insulator layer 13, and a side ground conductor layer 22B formed on the top surface of the insulator layer 13. An opening is formed in the insulator layer 12, and a hollow portion HS is formed in the opening by laminating other insulator layers and conductor layers thereon.

[0135] The insulating layers 11, 12, 13, and 14 on which the various conductor layers are formed are stacked, and then pressurized and heated to form a laminate.

[0136] An interlayer connection conductor 4 is formed between the main ground conductor layer 21 and the side ground conductor layers 22A and 22B.

[0137] 17C , a grounded coplanar waveguide 111C has a reference ground conductor layer 21 formed on the bottom surface of the insulator layer 11, and a side ground conductor layer 22A formed on the top surface of the insulator layer 11. Furthermore, a side ground conductor layer 22B is formed on the top surface of the insulator layer 13, and a signal line conductor layer 23 is formed on the bottom surface of the insulator layer 13.

[0138] For example, the insulator layer 11 is a resin sheet having a copper foil clad resin sheet on both sides thereof, with a main ground conductor layer 21 and a side ground conductor layer 22A made of copper foil or the like formed on both sides thereof. Similarly, the insulator layer 13 is a resin sheet having a copper foil clad resin sheet on both sides thereof, with a side ground conductor layer 22B and a signal line conductor layer 23 made of copper foil or the like formed on both sides thereof.

[0139] The two double-sided copper foil-laminated resin sheets are joined together via an adhesive layer 50. This adhesive layer 50 is formed in a position that avoids the vicinity of the signal line conductor layer 23. This adhesive layer 50 is an insulating layer, and a hollow section HS is formed in the area where this adhesive layer 50 is not present.

[0140] An interlayer connection conductor 4 is formed between the main ground conductor layer 21 and the side ground conductor layers 22A and 22B.

[0141] In the grounded coplanar waveguide 111A according to the eleventh embodiment, the distance in the thickness direction between the signal line conductor layer 23 and the side ground conductor layer 22 is greater than in the examples shown so far, and therefore the signal line conductor layer 23 is disposed at a position recessed from the side ground conductor layer 22. This improves the shielding effect of the signal line conductor layer 23 due to the presence of the side ground conductor layer 22.

[0142] Similarly, in the grounded coplanar waveguide 111B, the distance in the thickness direction between the signal line conductor layer 23 and the side ground conductor layer 22A is greater than in the examples shown so far, so that the signal line conductor layer 23 is positioned further back than the side ground conductor layer 22B, thereby improving the shielding effect of the signal line conductor layer 23 due to the presence of the side ground conductor layer 22B.

[0143] In the grounded coplanar waveguide 111B, the outer surface of the side ground conductor layer 22B close to the surface of the laminate has a large surface roughness. As in the side ground conductor layer 22B, among the multiple side ground conductor layers, the side ground conductor layer with the large surface roughness may be the surface that does not face the main ground conductor layer 21.

[0144] According to the grounded coplanar waveguide 111C, the surface of the signal line conductor layer 23 with low surface roughness and the surface of the side ground conductor layer 22A with low surface roughness are close to each other, which effectively increases the transmission loss of high-frequency signals due to the skin resistance of the signal line conductor layer 23 and the side ground conductor layer 22A.

[0145] Twelfth Embodiment In the twelfth embodiment, a grounded coplanar waveguide is illustrated which includes a plurality of parallel signal line conductor layers and is characterized by the periodic arrangement of the signal line conductor layers and the hollow portions.

[0146] 18A is a partial plan view of a grounded coplanar waveguide 112A, FIG. 18B is a partial plan view of a grounded coplanar waveguide 112B, and FIG. 18C is a partial plan view of a grounded coplanar waveguide 112C.

[0147] Like the grounded coplanar waveguides described in the first embodiment and the like, the grounded coplanar waveguides 112A, 112B, and 112C include a reference ground conductor layer, a signal line conductor layer 23 facing the reference ground conductor layer in the thickness direction of the insulator layers, and side ground conductor layers 22 facing the reference ground conductor layer in the thickness direction of the insulator layers and disposed on the left and right sides along the extension direction of the signal line conductor layer 23. That is, when viewed in the stacking direction of the multiple insulator layers (Z direction), the signal line conductor layer 23 overlaps the reference ground conductor layer. Also, when viewed in the stacking direction of the multiple insulator layers (Z direction), the grounded coplanar waveguides 112A, 112B, and 112C include side ground conductor layers 22 on both sides of the signal line conductor layer 23 and along the extension direction of the signal line conductor layer 23.

[0148] The grounded coplanar waveguides 112A, 112B, and 112C have a hollow portion HS in an insulator layer that is present between the signal line conductor layer 23 and the reference ground conductor layer, among a plurality of insulator layers.

[0149] The grounded coplanar waveguides 112A, 112B, and 112C have three parallel signal line conductor layers 23. The hollow spaces HS are periodically arranged along the extending direction of the three signal line conductor layers 23.

[0150] The hollow portions HS are rectangular in shape and are elongated in the extension direction (X direction) of the signal line conductor layer 23. When viewed in the thickness direction (Z direction) of the insulator layer, the corners of each hollow portion HS are rounded. The hollow portions HS are also arranged at equal intervals in the X direction.

[0151] In the example of the grounded coplanar waveguide 112A, the hollow portions HS are arranged at the same position in the parallel direction (Y direction) of the signal line conductor layers 23.

[0152] On the other hand, in the example of the grounded coplanar waveguide 112B, the hollow portions HS adjacent to each other in the parallel direction (Y direction) of the signal line conductor layers 23 are arranged at different positions (two positions) in the extension direction (X direction) of the signal line conductor layers 23.

[0153] Also in the example of the grounded coplanar waveguide 112C, the hollow portions HS adjacent to each other in the parallel direction (Y direction) of the signal line conductor layers 23 are arranged at different positions, but the positions of the hollow portions HS are different for each signal line conductor layer 23. In this example, there are three possible positions for arranging the hollow portions HS.

[0154] In a structure such as the grounded coplanar waveguide 112A in which a plurality of signal line conductor layers 23 are arranged in parallel with one another and hollow portions HS are present periodically along the extension direction (X direction) of the plurality of signal line conductor layers 23 and at the same position in the parallel direction (Y direction) of the plurality of signal line conductor layers 23, the portions of the insulator layer that are not hollow portions HS are aligned at the same positions, so that the strength against stress in the parallel direction (Y direction) of the plurality of signal line conductor layers 23 is high.

[0155] On the other hand, in a structure such as the grounded coplanar waveguides 112B and 112C in which a plurality of parallel signal line conductor layers 23 are configured and hollow portions HS are present periodically along the extension direction (X direction) of the plurality of signal line conductor layers 23 and at different positions in the parallel direction (Y direction) of the plurality of signal line conductor layers 23, the locations where the hollow portions HS are formed and the locations where the hollow portions HS are not formed are offset in the extension direction (X direction) for each signal line conductor layer 23, so that unwanted coupling of the electromagnetic field between adjacent signal line conductor layers is small and isolation between the transmission paths is high.

[0156] Furthermore, when the position of the hollow portion HS differs for each signal line conductor layer 23, as in the grounded coplanar waveguide 112C, the hollow-formed portion and the non-hollow-formed portion are misaligned for the three transmission paths, so that isolation is high not only between adjacent signal line conductor layers but also between signal line conductor layers beyond the adjacent signal line conductor layers.

[0157] Thirteenth Embodiment In a thirteenth embodiment, an electronic device according to the present invention will be illustrated.

[0158] 19 is a cross-sectional view of an electronic device 401 according to the thirteenth embodiment. The electronic device 401 includes substrates 201A and 201B, a battery 202, a grounded coplanar waveguide 101, a housing 203, and the like.

[0159] A mounting component 9 serving as a connector is mounted on the grounded coplanar waveguide 101. This connector is connected to each of the substrates 201A and 201B. A battery 202 is disposed between the substrates 201A and 201B, and the grounded coplanar waveguide 101 is disposed in the gap between the outer surface of the battery 202 and the inner surface of the housing 203.

[0160] The positional relationship between the grounded coplanar waveguide 101 and nearby objects such as the battery 202 and the housing 203 is important. That is, it is preferable to determine the arrangement of the grounded coplanar waveguide 101 so that the amount of change in the electrical characteristics relative to the amount of change in the proximity distance of the object is small.

[0161] For example, when comparing the housing 203 made of metal with the battery 202 containing a large amount of conductive material, if the electrical characteristics of the grounded coplanar waveguide are more strongly affected by the portion of the housing 203 that is close to the grounded coplanar waveguide, it is better to arrange the grounded coplanar waveguide 101 so that the reference ground conductor layer 21 (see FIG. 1 ) faces the inner surface of the housing 203. In this arrangement, it is even better to provide a gap between the signal line conductor layer 23 (see FIG. 1 ) of the grounded coplanar waveguide 101 and the battery 202 to reduce the influence of the battery 202.

[0162] Conversely, if the electrical characteristics of the grounded coplanar waveguide are more strongly affected by the battery 202, it is better to arrange the grounded coplanar waveguide 101 so that the reference ground conductor layer 21 faces the battery 202. In this arrangement, it is even better to provide a gap between the signal line conductor layer 23 of the grounded coplanar waveguide 101 and the housing 203 to reduce the influence of the housing 203.

[0163] In the example shown in FIG. 19, substrates 201A and 201B are connected to both ends of the grounded coplanar waveguide via connectors, but it is also possible to use a structure in which one end is connected to the antenna.

[0164] The grounded coplanar waveguide 101 transmits a high-frequency signal between a circuit configured on the substrate 201A and a circuit configured on the substrate 201B. This high-frequency signal is, for example, a signal in the 1 GHz to 1 THz band.

[0165] Various embodiments of the present invention have been presented so far, but these are all examples and are not intended to limit the scope of the present invention. Various omissions, substitutions, and modifications can be made to the embodiments of the present invention without departing from the spirit of the invention. Embodiments with such omissions, substitutions, and modifications are included within the scope and spirit of the present invention, and are also included in the scope of the invention and its equivalents as set forth in the claims of this application.

[0166] For example, the interlayer connection conductor 4 that electrically connects the main ground conductor layer 21 and the side ground conductor layer 22 may be formed by a method other than the electroplating method described above. For example, the interlayer connection conductor 4 may be formed by filling the resin-removed portion with a conductive paste or solder paste and heating it.

[0167] 4A, 4B, and 4C show examples in which the grounded coplanar waveguide is provided with a mounted component 9 as a connector, but the mounted component is not limited to a connector. For example, it may be a semiconductor element or a circuit element.

[0168] In the example shown in FIG. 19, both ends of grounded coplanar waveguide 101 are connected to substrates 201A and 201B via connectors, but it is also possible to adopt a structure in which the grounded coplanar waveguide is directly connected to a substrate (mother substrate), that is, a structure in which the grounded coplanar waveguide is mounted on a substrate.

[0169] 1A, 1B, and 1C, a cylindrical opening 12H is provided, and in the examples shown in FIGS. 18A, 18B, and 18C, a rectangular hollow portion HS is provided, but the shapes of the opening and hollow portion are not limited to these. For example, they may be polygonal other than rectangular when viewed in the thickness direction of the insulator layer, or may have rounded corners.

[0170] In the examples shown in FIGS. 1A, 1B, and 1C, the openings 12H are arranged so as to be dispersed in the extension direction of the signal line conductor layer 23, but the openings may have a shape that is continuous in the direction along the signal line conductor layer 23.

[0171] Furthermore, the signal propagating through the grounded coplanar waveguide may be an analog signal or a digital signal.

[0172] In addition, in each embodiment, an example has been shown in which an opening 12H or the like is formed in the insulator layer to form the hollow portion HS. The opening 12H or the like may be formed by processing the insulator layer, or the insulator layer having the opening may be formed during the insulator layer formation stage. For example, a porous insulator layer may be formed, and some of the pores may be used as the opening. In other words, the hollow portion HS may be formed in the portion of the insulator layer that overlaps the opening.

[0173] DESCRIPTION OF SYMBOLS HS, HSA, HSB...Hollow portion S...Solder S1...First principal surface S2...Second principal surface 3...Protective film 4...Interlayer connection conductor 9...Mounted component 9G...Ground terminal 9S...Signal terminal 11, 12, 12A, 12B, 13, 13A, 13B, 14...Insulator layer 12H, 13H...Opening 21...Reference ground conductor layer 22, 22A, 22B, 22C...Side ground conductor layer 22E...Ground electrode 23, 23A, 23B...Signal line conductor layer 23E...Signal electrode 50, 51, 52...Adhesive layer 101, 102, 103A, 103B, 103C, 104A, 104B, 104C, 105, 106A, 106B, 107A, 107B, 108, 109, 110, 111A, 111B, 111C, 112A, 112B, 113A, 113B, 113C...Grounded coplanar waveguide 201A, 201B...Substrate 202...Battery 203...Housing 401...Electronic device

Claims

1. A grounded coplanar waveguide comprising a laminate comprising a plurality of stacked insulator layers and conductor layers formed by bonding to surfaces of all or some of the insulator layers of the plurality of insulator layers, wherein the conductor layers include a reference ground conductor layer, a signal line conductor layer overlapping the reference ground conductor layer when the laminate is viewed in the stacking direction, and a side ground conductor layer on either side of the signal line conductor layer and along the extension direction of the signal line conductor layer when the laminate is viewed in the stacking direction, wherein the conductor layer has different surface roughnesses on one side and the other side, wherein the side of the signal line conductor layer with the smaller surface roughness is the side facing the reference ground conductor layer, and the side of the side ground conductor layer with the smaller surface roughness is the side not facing the reference ground conductor layer.

2. The grounded coplanar waveguide according to claim 1, wherein the surface of the reference ground conductor layer with the large surface roughness is the surface not facing the signal line conductor layer.

3. The grounded coplanar waveguide according to claim 1, wherein the surface of the reference ground conductor layer with the greater surface roughness is the surface facing the signal line conductor layer.

4. The grounded coplanar waveguide according to claim 1, wherein the signal line conductor layer is thicker than the side ground conductor layer.

5. A grounded coplanar waveguide according to any one of claims 1 to 4, wherein a hollow portion is formed in an insulator layer, of the plurality of insulator layers, that is present between the signal line conductor layer and the reference ground conductor layer.

6. The grounded coplanar waveguide according to claim 5, wherein at least a portion of said signal line conductor layer is exposed to said hollow portion.

7. The grounded coplanar waveguide according to claim 5 or 6, wherein at least a portion of the reference ground conductor layer is exposed to the hollow portion.

8. A grounded coplanar waveguide according to any one of claims 5 to 7, wherein the signal line conductor layer is made up of a plurality of signal line conductor layers arranged in parallel to one another, and the hollow portions are periodically present along the extension direction of the plurality of signal line conductor layers and are present at the same position in the parallel direction of the plurality of signal line conductor layers.

9. A grounded coplanar waveguide according to any one of claims 5 to 7, wherein the signal line conductor layer is made up of a plurality of signal line conductor layers arranged in parallel to one another, and the hollow portions are periodically arranged along the extension direction of the plurality of signal line conductor layers and are arranged at different positions in the parallel direction of the plurality of signal line conductor layers.

10. A grounded coplanar waveguide according to any one of claims 1 to 9, comprising a ground electrode that is electrically connected to the side ground conductor layer and a signal electrode that is electrically connected to the signal line conductor layer, the ground electrode and the signal electrode being formed on an insulator layer that is located on the surface of the plurality of insulator layers.

11. A grounded coplanar waveguide according to any one of claims 1 to 10, wherein the material of the plurality of insulator layers is a thermoplastic resin, and adjacent insulator layers among the plurality of insulator layers in the stacking direction are bonded to each other without an adhesive layer therebetween.

12. The grounded coplanar waveguide according to any one of claims 1 to 10, wherein the plurality of insulator layers are stacked with a material different from that of the plurality of insulator layers interposed therebetween.

13. A grounded coplanar waveguide according to any one of claims 1 to 12, wherein a single insulator layer or multiple insulator layers among the multiple insulator layers are provided with an interlayer connection conductor that provides electrical continuity between the side ground conductor layer and the reference ground conductor layer.

14. An electronic device comprising an electronic circuit that uses the grounded coplanar waveguide according to any one of claims 1 to 13 as a signal transmission path.

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