HIGH-FREQUENCY TRANSMISSION LINE

Abstract

High-frequency transmission line (10) which has: a multilayered substrate (2, 2a to 2j) containing several dielectric layers (L1 to L6) stacked on top of each other; Signal lines (3, 3a, 3b, 4) are formed on two outer surfaces of the multilayer substrate (2, 2a to 2j); a signal contact hole (5) that couples the signal lines (3, 3a, 3b, 4) formed on the two outer surfaces; at least one earthing plane (6) arranged between the dielectric layers (L1 to L6), contained in the multilayer substrate (2, 2a to 2j) and surrounding a clearance area (61) arranged around the signal contact hole (5); and several grounding contact holes (7, 7a, 7b) that penetrate at least one of the dielectric layers (L1 to L6) in a layer stacking direction, surround the signal contact hole (5) and are electrically coupled to the grounding plane (6), wherein an interlayer transmission line (62) is defined through and between the signal contact hole (5) and the grounding contact holes (7, 7a, 7b), wherein a high-frequency signal is transmitted in the layer stack direction through the interlayer transmission line (62), a contact hole diameter of the signal contact hole (5) is set to a dimension that leads to propagation in the interlayer transmission line (62) by means of multimode transmission, and the high-frequency signal in multimode transmission forms a high-intensity region, which has a high-intensity electric field in one transmission direction, and a low-intensity region, which has a low-intensity electric field in the transmission direction, and at least one of the contact hole spacing between the signal contact hole (5) and the respective grounding contact holes (7, 7a, 7b), the contact hole diameter and a substrate thickness of the multilayer substrate (2, 2a to 2j) for introducing the high-frequency signal from the interlayer transmission line (62) into the signal lines (3, 3a, 3b, 4) in the high-intensity range of multimode transmission is set. the dielectric layers (L1 to L6) are three or more dielectric layers (L1 to L6) and there is at least one earthing plane (6) or several earthing planes (6), the grounding contact holes (7, 7a, 7b) contain interlayer contact holes (7b) that penetrate at least one of the dielectric layers (L1 to L6) excluding the dielectric layers (L1 to L6) on which the signal lines (3, 3a, 3b, 4) are formed, and electrically couple the grounding planes (6) together, and the interlayer contact holes (7b) each have a dimension that leads to mutual cancellation of a first electric field (E1) and a second electric field (E2), wherein the first electric field (E1) is an electric leakage field that leaks from the interlayer transmission line (62) to the interlayer contact holes (7b) and passes between the interlayer contact holes (7b) and the grounding plane (6) above the interlayer contact holes (7b) and between the interlayer contact holes (7b) and the grounding plane (6) below the interlayer contact holes (7b), and wherein the second electric field (E2) is an electric leakage field that leaks from the interlayer transmission line (62) to the interlayer contact holes (7b), passes through the interlayer contact holes (7b) and is reflected at the grounding plane (6) above or below the interlayer contact holes (7b).

Description

Technical field

[0001] The invention relates to a technique for transmitting a high-frequency signal through a multilayer substrate in a layer stacking direction. State of the art

[0002] JP 2015 - 50 680 A describes a technique for forming a high-frequency transmission line which has a coaxial conductor structure which includes a signal contact hole that couples signal conductor patterns formed on two sides of a multilayer wiring substrate, and ground contact holes arranged along a circle around the signal contact hole and having a ground potential or earth potential.

[0003] The publication “Li, Zhipeng, et al, Analysis of wideband multilayer LTCC vertical via transition for millimeter-wave System-in-package, 2017 18th International Conference on Electronic Packaging Technology, IEEE, 2017, pages 1039-1042, 16-19 Aug. 2017” discloses a high-frequency transmission line comprising: a multilayer substrate containing several dielectric layers stacked on top of each other; signal lines formed on two outer surfaces of the multilayer substrate; a signal contact hole coupling the signal lines formed on the two outer surfaces; at least one ground plane located between the dielectric layers, contained within the multilayer substrate, and surrounding a disposal area arranged around the signal contact hole; and multiple ground contact holes penetrating at least one of the dielectric layers in a layer stacking direction.the signal contact hole is surrounded and electrically coupled to the grounding plane, wherein an interlayer transmission line, which transmits a high-frequency signal in the layer stack direction, is formed between the signal contact hole and the grounding contact holes, a contact hole diameter of the signal contact hole is set to a dimension that leads to propagation in the interlayer transmission line by means of multimode transmission, and the high-frequency signal in multimode transmission forms a high-intensity region, which has a high-intensity electric field in one transmission direction, and a low-intensity region, which has a low-intensity electric field in the transmission direction, and at least one of an inter-contact hole spacing between the signal contact hole and the respective grounding contact holes,the contact hole diameter and substrate thickness of the multilayer substrate are set to introduce the high-frequency signal from the interlayer transmission line into the signal lines in the high-intensity range of multimode transmission.

[0004] JP 2015-50680A describes a high-frequency transmission line in which, on a top ground plane below several ground planes forming a multi-layered wiring plate, an extension part forming an end part of the ground plane is arranged, which extends in the direction of a high-frequency signal contact hole that is connected to a high-frequency signal line on the top layer.

[0005] US 2003 / 0 133 279 A1 describes a high-frequency printed circuit board where L > λ / 4 and π(A+B) <= λ are satisfied, where L is the length of a through conductor, A is the diameter of the through conductor, B is the shortest distances between the through conductor and a plurality of grounded through conductors, π is a circle ratio, and λ is the effective wavelength of a high-frequency signal carried by the through conductor. Several dielectric layers are stacked alternately to form ground layers, and an upper conduction layer and a lower conduction layer are connected via a contact hole. The ground layers are connected via respective ground contact holes that penetrate the dielectric layers and are spaced apart from the through conductor. Summary of the invention

[0006] In a high-frequency transmission line with a coaxial structure, a signal is transmitted via single-mode transmission to prevent or suppress transmission loss. To achieve single-mode transmission in the high-frequency transmission line, the contact hole diameter and similar parameters of the signal contact hole must be reduced as the frequency of the transmitted signal increases. Through detailed investigations, the inventor discovered that when a high-frequency transmission line, such as the one described above, is used for single-mode transmission of a high-frequency signal, the contact hole diameter and similar parameters of the signal contact hole must be relatively small, making it difficult to mass-produce the high-frequency transmission line.

[0007] The object of the invention is to create a mass-producible high-frequency transmission line that can reduce transmission loss. This object is achieved by a high-frequency transmission line with the features of claim 1. The dependent claims relate to advantageous embodiments of the invention.

[0008] One aspect of the invention comprises a multilayer substrate, signal lines, a signal contact hole, at least one grounding plane, and multiple grounding contact holes. The multilayer substrate contains several dielectric layers stacked on top of each other. The signal lines are formed on the two outer surfaces of the multilayer substrate. The signal contact hole couples the signal lines formed on the two outer surfaces to each other. The grounding plane is arranged between the dielectric layers, is contained within the multilayer substrate, and covers the area surrounding the signal contact hole. The grounding contact holes penetrate at least one of the dielectric layers in the layer stacking direction, are arranged around the signal contact hole, and are electrically coupled to the grounding plane.An interlayer transmission line, which carries the high-frequency signal in the layer stack direction, is formed between the signal contact hole and the ground contact holes. The signal contact hole has a diameter that allows the high-frequency signal to propagate through the interlayer transmission line via multimode transmission. Multimode transmission creates a high-intensity region, characterized by a high electric field intensity, and a low-intensity region, characterized by a low electric field intensity, in the transmission direction. At least one of the interlayer contact hole spacing between the signal contact hole and the respective ground contact holes, the contact hole diameter, and the thickness of the multilayer substrate is determined to introduce the high-frequency signal from the interlayer transmission line into the signal lines in the high-intensity region of the multimode transmission.

[0009] According to one aspect of the invention, the signal contact hole has a contact hole diameter that allows the high-frequency signal to propagate through the interlayer transmission line via multimode transmission. That is, the signal contact hole is designed such that it has a contact hole diameter larger than a contact hole diameter that allows the high-frequency signal to propagate through the interlayer transmission line via single-mode transmission. Therefore, the high-frequency transmission line can be mass-produced.

[0010] In general, transmission loss is greater in multimode transmission than in single-mode transmission. However, the electric field distribution in the input section of the high-frequency transmission line can be reproduced in the output section by appropriately matching the transmission line, thereby suppressing transmission loss. At least one of the parameters of the inter-contact hole spacing, the contact hole diameter, and the substrate thickness of the high-frequency transmission line is determined such that the high-frequency signal enters the signal lines from the inter-layer transmission line in the high-intensity region of the electric field. This suppresses transmission loss during the propagation of the high-frequency signal through the inter-layer transmission line.Therefore, a mass-producible high-frequency transmission line can be realized that can suppress transmission loss. Brief description of the drawings Fig. Figure 1 is a top view of a high-frequency transmission line according to a first example. Fig. 2 is a cross-section along line II-II of the Fig. 1. Fig. Figure 3 is a schematic cross-sectional view of a coaxial cable. Fig. Figure 4 is a cross-sectional view in one thickness direction showing an electric field distribution in the high-frequency transmission line when a signal propagates in one thickness direction via single-mode transmission. Fig. Figure 5 is a cross-sectional view in one thickness direction showing an electric field distribution in the high-frequency transmission line when a signal propagates via multimode transmission. Fig. Figure 6 represents the transmission loss as a function of frequency in single-mode transmission and multi-mode transmission over a coaxial cable. Fig. Figure 7 is a top view of a high-frequency transmission line according to a second example. Fig. 8 is a cross-sectional view along line VIII-VIII of the Fig. 7. Fig. Figure 9 is a top view of a high-frequency transmission line according to a third example. Fig. Figure 10 is a top view of a high-frequency transmission line according to a fourth example. Fig. Figure 11 is a top view of a high-frequency transmission line according to a fifth example. Fig. 12 is a cross-sectional view along line XII-XII of the Fig. 11. Fig. Figure 13 is a diagram representing a condition in which a signal contact hole and a ground contact hole are electrically connected due to cracks formed in a substrate between the signal contact hole and the ground contact holes. Fig. Figure 14 is a top view of the surface of a high-frequency transmission line according to a sixth example. Fig. Figure 15 is a top view of an inner surface of a high-frequency transmission line according to the sixth example. Fig. 16 is a cross-sectional view along line XVI-XVI of the Fig. 14. Fig. Figure 17 is a cross-sectional view in a thickness direction showing an electric field distribution in a high-frequency transmission line containing inner layer connection surfaces as a signal propagates through the high-frequency transmission line. Fig. Figure 18 is a cross-sectional view in one thickness direction showing an electric field distribution in a high-frequency transmission line that does not contain any inner layer termination surfaces as a signal propagates through the high-frequency transmission line. Fig. Figure 19 is a diagram showing transmission loss as a function of frequency in a high-frequency transmission line containing inner layer termination surfaces and in a high-frequency transmission line that does not contain inner layer termination surfaces. Fig. Figure 20 is a cross-sectional view of a high-frequency transmission line according to a seventh example. Fig. Figure 21 is a cross-sectional view of a high-frequency transmission line according to an eighth example. Fig. Figure 22 is a top view of a high-frequency transmission line according to a ninth example according to an embodiment of the invention. Fig. 23 is a cross-sectional view along line XXIII-XXIII of the Fig. 22. Fig. Figure 24 is a top view of an example of a conventional high-frequency transmission line. Fig. Figure 25 is a cross-sectional view of the example of the conventional high-frequency transmission line along line XXV-XXV of the Fig. 24. Fig. Figure 26 is a top view of another example of a conventional high-frequency transmission line. Fig. 27 is a cross-sectional view of the other example of the conventional high-frequency transmission line along line XXVII-XXVII of the Fig. 26. Fig. Figure 28 is a cross-sectional view in a thickness direction showing an electric field distribution in a high-frequency transmission line according to the embodiment. Fig. Figure 29 is a cross-sectional view in one thickness direction showing an electric field distribution in a high-frequency transmission line according to a comparative example. Fig. Figure 30 is a diagram showing a transmission loss as a function of frequency in a high-frequency transmission line according to the comparative example and embodiment. Fig. Figure 31 is a top view of a high-frequency transmission line according to a tenth example according to the embodiment of the invention. Fig. Figure 32 is a cross-sectional view in a thickness direction showing an electric field distribution in a high-frequency transmission line according to a further embodiment of the invention.

[0011] Examples and embodiments according to the invention are described below with reference to the drawings. 1. Examples 1-1. First example 1-1-1. Configuration

[0012] A high-frequency transmission line according to the invention is used for the transmission of high-frequency signals, in particular high-frequency signals having a frequency of 70 GHz or higher, and is specifically used for feeding an antenna with electrical power.

[0013] The configuration of a high-frequency transmission line 10 according to a first example is described with reference to the Fig. 1 and Fig. 2 described. The high-frequency transmission line 10 contains a multilayer substrate 2, signal lines 3 and 4, a signal contact hole 5 and six through contact holes 7.

[0014] The multilayer substrate 2 contains two dielectric layers L1 and L2 and three pattern layers P1 to P3, between which the respective dielectric layers L1 and L2 are arranged. Hereinafter, the pattern layers P1 and P3, which are arranged beneath the pattern layers P1 to P3 on the outer surfaces of the multilayer substrate 2, are referred to as the outer layers, and the pattern layer P2, which is arranged between the dielectric layers L1 and L2, is referred to as the intermediate layer.

[0015] On the outer layers P1 and P3, the respective signal lines 3 and 4 are formed to serve as waveguides for the transmission of high-frequency signals. Signal line 3 is a conductor pattern formed on outer layer P1, and signal line 4 is a conductor pattern formed on outer layer P3. Signal lines 3 and 4 consist, for example, of a copper foil deposited by etching. The end sections of signal lines 3 and 4 are arranged at positions facing the two dielectric layers L1 and L2 and are coupled to each other via the signal contact hole 5, which penetrates the multilayer substrate 2. The signal contact hole 5 is a metal conductor.

[0016] An earthing plane 6 is formed in the intermediate layer P2. The earthing plane 6 is a conduction pattern formed in the intermediate layer P2 with a copper foil or similar material and is coupled to a ground potential. The earthing plane 6 covers the entire contact area of ​​the dielectric layer L1 and the dielectric layer L2, except for an eliminated area 61. The eliminated area 61 is a circular area around the signal contact hole. In other words, the signal contact hole 5 is not electrically coupled to the earthing plane 6.

[0017] The six through-contact holes 7 are each a metal conductor that penetrates the multilayer substrate 2 in the layer stacking direction and are electrically coupled to the grounding plane 6. That is, the through-contact holes 7 are grounding contact holes. Hereinafter, the through-contact holes 7 will also be referred to as grounding contact holes 7. In this example, the contact hole diameter of each through-contact hole 7 is the same as the contact hole diameter r1 of the signal contact hole 5. The six through-contact holes 7 are arranged along the circumference of a circle C around the signal contact hole 5 such that the through-holes of the through-contact holes 7 are tangential to the outside of the circle C. An interlayer transmission line 62 for transmitting a high-frequency signal in the layer stacking direction is formed between the signal contact hole 5 and the six through-holes 7.The cross-section of the interlayer transmission line 62 along a direction orthogonal to the layer stacking direction has a ring-shaped form, i.e. a so-called donut shape, which is defined by two concentric circles.

[0018] Circle C is defined by the outer circumferential edge of the elimination area 61. The radius of circle C is determined such that the position of an outer conductor of a coaxial line, which contains the signal contact hole 5 as an inner conductor, coincides with circle C. In this way, the high-frequency transmission line 10 has a quasi-coaxial line containing the signal contact hole 5, which serves as the inner conductor, and the six through-contact holes 7, which serve as the outer conductor. The radius of circle C is determined based on the frequency of the high-frequency signal propagating through the interlayer transmission line 62, the impedance of the interlayer transmission line 62, the permittivity of the dielectric layers L1 and L2, and similar factors. 1-1-2. Transmission mode

[0019] The transmission mode of the coaxial cable is described below. Fig. Figure 3 is a schematic view of the coaxial cable. As shown in Fig. As shown in Figure 3, the critical frequency fc of the coaxial transmission line is determined using equation (1). In equation (1), d is the outer diameter of the inner conductor, D is the inner diameter of the outer conductor, εr is the relative permittivity of the dielectrics between the inner and outer conductors, and c is the speed of light. Equation 1 fc=cπεrD+d2

[0020] A signal with a frequency equal to or lower than the critical frequency fc propagates through the coaxial cable via single-mode transmission. In single-mode transmission, a signal is transmitted only in one transverse electromagnetic mode (TEM mode), which is the basic mode. Fig. Figure 4 represents the electric field intensity distribution when a high-frequency signal propagates through the interlayer transmission line via single-mode transmission. If the frequency of the high-frequency signal is equal to or less than the critical frequency fc, a high-intensity region exhibiting a high electric field intensity is continuously formed near the signal contact hole along the layer stack direction, as shown in Figure 4. Fig. Figure 4 illustrates this. Thus, transmission loss in the connection sections of the waveguide and the intermediate layer transmission line, in particular the output sections from the intermediate layer transmission line to the signal line, is suppressed.

[0021] To increase the critical frequency fc according to equation (1), the outer diameter d or the inner diameter D must be decreased. For reliability, the inner diameter D, i.e., the inter-contact hole spacing Rd between the side wall of the signal contact hole and the side wall of a respective ground contact hole, must be relatively large so that the signal contact hole and the ground contact holes are not electrically coupled. Therefore, to increase the critical frequency fc, the inter-contact hole spacing Rd is set to a predetermined value, and the outer diameter d, i.e., the contact hole diameter r1 of the signal contact hole, is decreased. If a 77 GHz high-frequency signal is to be transmitted, the critical frequency fc must be equal to or greater than 81 GHz or the maximum frequency of the 77 GHz band.To achieve a critical frequency fc of 81 GHz or greater, the contact hole diameter r1 must be 0.2 mm or less. In the example shown in . Fig. As shown in Figure 4, the contact hole diameter r1 is 0.15 mm.

[0022] However, if the contact hole diameter r1 is too small, mass production of the high-frequency transmission line becomes difficult. To enable mass production of the high-frequency transmission line, it is desirable to set the contact hole diameter r1 to 0.3 mm or larger. That is, if the high-frequency transmission line used to transmit a 77 GHz high-frequency signal has a size that allows for mass production, the interlayer transmission line does not meet the condition for single-mode transmission. Thus, several higher-order modes, in addition to the base mode, are excited in the interlayer transmission line. The high-frequency signal then propagates through the interlayer transmission line while resonating between the excited modes.The high-frequency signal propagates through the interlayer transmission line via multimode transmission (multimode interference transmission).

[0023] When the high-frequency signal propagates through the interlayer transmission line via multimode transmission, high-intensity regions, which have a high electric field intensity, and low-intensity regions, which have a low electric field intensity that is lower than that in the high-intensity region, are formed in the transmission direction. Fig. Figure 5 represents the electric field intensity distribution when the contact hole diameter is 0.7 mm and a high-frequency signal is transmitted through an interlayer transmission line using multimode transmission (multimode interference transmission). As shown in Fig. As shown in Figure 5, the high-intensity and low-intensity regions alternate in the intermediate layer transmission line along the transmission direction. A low-intensity region in the output section of the intermediate layer transmission line increases transmission loss, whereas a high-intensity region in the output section reduces transmission loss. In multimode transmission, the mode of the input section from the signal line to the intermediate layer transmission line can be reproduced in the output section from the intermediate layer transmission line to the signal line by adjusting the length and width of the intermediate layer transmission line. That is, a high-intensity region can be created in the output section from the intermediate layer transmission line to the signal line.

[0024] Therefore, in this example, the contact hole diameter r1 of the signal contact hole 5 of the high-frequency transmission line 10 is set to a value that enables mass production, i.e., propagation by multimode transmission (multimode interference transmission). Furthermore, in this example, at least one of the substrate thickness Ho of the multilayer substrate 2, the inter-contact hole spacing Rd, and the contact hole diameter r1 is designed to introduce the high-frequency signal from the interlayer transmission line 62 into the signal line 4 in the high-intensity range of the electric field.In the following, the matching of at least one of the substrate thickness Ho of the multilayer substrate, the inter-contact hole spacing Rd and the contact hole diameter r1 for introducing the high-frequency signal from the intermediate transmission line 62 into the signal line 4 in the high-intensity range of the electric field is referred to as electric field distribution matching. 1-1-3. Analytical result

[0025] Fig. Figure 6 shows the transmission loss as a function of frequency for a case where the contact hole diameter r1 is 0.15 mm and a case where the electric field distribution is matched to obtain a contact hole diameter of 0.7 mm. When the contact hole diameter r1 is 0.15 mm and the frequency is within the range of 70 to 80 GHz, the transmission loss is lower than when the contact hole diameter is 0.7 mm, as shown in Fig. Figure 6 is shown. However, the transmission loss increases suddenly when the frequency exceeds 80 GHz.

[0026] This shows that when the contact hole diameter is 0.15 mm, the interlayer transmission line fulfills the single-mode condition within a frequency range of 70 to 80 GHz, but does not fulfill the single-mode condition when the frequency exceeds 80 GHz. That is, when the contact hole diameter r1 is 0.15 mm, the high-frequency signal exceeding 80 GHz propagates through the interlayer transmission line via multimode transmission. However, the transmission loss increases sharply because the electric field distribution is not matched. When the contact hole diameter is 0.7 mm and the electric field distribution is matched, the transmission loss is suppressed or reduced to approximately 1 dB or less within a frequency range of 70 to 80 GHz, thus achieving a satisfactory transmission loss. 1-2. Second example

[0027] A high-frequency transmission line 10a according to a second example is described below with reference to the Fig. 7 and Fig. 8 described. The high-frequency transmission line 10a contains a multilayer substrate 2a, signal lines 3 and 4, one signal contact hole 5, six through contact holes 7 and two intermediate layer contact holes 7a.

[0028] The multilayer substrate 2a contains three dielectric layers L1 to L3 and four pattern layers P1 to P4, between which the respective dielectric layers L1 to L3 are arranged. Hereinafter, the pattern layers P1 and P4, which are arranged beneath the pattern layers P1 to P4 on the outer surfaces of the multilayer substrate 2a, are referred to as the outer layers, and the other pattern layers P2 and P3 are referred to as the intermediate layers.

[0029] Signal lines 3 and 4 are formed on the respective outer layers P1 and P4. Grounding planes 6 are formed in the intermediate layers P2 and P3. The two intermediate layer contact holes 7a are formed in the multilayer substrate 2a. The two intermediate layer contact holes 7a penetrate the dielectric layer L2, which is a dielectric layer beneath the three dielectric layers L1 to L3 and is not the one on which signal lines 3 and 4 are formed, and electrically couple the two grounding planes 6 formed in the intermediate layers P2 and P3. That is, the intermediate layer contact holes 7a are grounding contact holes formed within the layers. Thus, the grounding contact holes of the high-frequency transmission line 10a contain the six through-contact holes 7 and the two intermediate layer contact holes 7a.In the following, the interlayer contact holes 7a will also be referred to as grounding contact holes 7a.

[0030] One of the two interlayer contact holes 7a is located at a position that overlaps with the signal line 3 in the layer stack direction, and the other is located at a position that overlaps with the signal line 4. That is, the interlayer contact holes 7a are formed at positions that do not completely penetrate the multilayer substrate 2a, since the signal lines 3 and 4 are formed on the respective outer layers P1 and P4.

[0031] Therefore, the high-frequency transmission line 10a, which has the same configuration as the high-frequency transmission line 10 except for the two additional interlayer contact holes 7a which serve as grounding contact holes, can reduce the transmission loss more than the high-frequency transmission line 10.

[0032] In the high-frequency transmission line 10a, for example, the substrate thickness Ho can be 1 mm, the length L1 from the center of the signal contact hole 5 to the end of the respective signal lines 4 can be 4.5 mm, the thickness of the dielectric layers L1, L2 and L3 can be 0.1 mm, 0.8 mm and 0.1 mm respectively, the contact hole diameter r1 of the signal contact hole 5, the through-contact holes 7 and the intermediate layer contact holes 7a can be 0.7 mm each, the contact surface diameter r2 of the signal contact hole 5 and the through-contact holes 7 can be 0.95 mm each, and the width of the signal lines 3 and 4 can be 0.3 mm each.

[0033] Note that the two interlayer contact holes 7a can penetrate the outer layers in the layer stacking direction on the sides where the interlayers and the signal lines 3 and 4 are not coupled, and can be exposed on the corresponding outer surfaces of the multilayer substrate 2a. That is, of the two interlayer contact holes 7a, the interlayer contact hole 7a located at a position overlapping with the signal line 3 can penetrate the dielectric layers L2 and L3 and be exposed on the outer layer P4. Similarly, of the two interlayer contact holes 7a, the interlayer contact hole 7a located at a position overlapping with the signal line 4 can penetrate the dielectric layers L2 and L1 and be exposed on the outer layer P1. 1-3. Third example

[0034] A high-frequency transmission line 10b according to a third example is described with reference to Fig. 9 described. The high-frequency transmission line 10b contains a multilayer substrate 2b, signal lines 3 and 4, one signal contact hole 5 and eight interlayer contact holes 7a. That is, the high-frequency transmission line 10b differs from the high-frequency transmission line 10a in that it contains six interlayer contact holes 7a instead of the six through contact holes 7, i.e. that all ground contact holes are interlayer contact holes 7a. 1-4. Fourth example

[0035] A high-frequency transmission line 10c according to a fourth example is described with reference to Fig. The high-frequency transmission line 10c is described in Figure 10. It contains a multilayer substrate 2c, signal lines 3 and 4, one signal contact hole 5, four through-contact holes 7, and two interlayer contact holes 7a. That is, the high-frequency transmission line 10c has two fewer through-contact holes 7 than the high-frequency transmission line 10a. Any number of grounding contact holes can be arranged, as long as the high-frequency signal can be sufficiently confined within an interlayer transmission line 62. 1-5. Fifth example

[0036] A high-frequency transmission line 10d according to a fifth example is described with reference to the Fig. 11 and Fig. The high-frequency transmission line 10d is described in Figure 12. It contains a multilayer substrate 2d, signal lines 3a, 3b, and 4, a signal contact hole 5, six through-contact holes 7, and two interlayer contact holes 7a. The multilayer substrate 2d has the same configuration as the multilayer substrate 2a. That is, the high-frequency transmission line 10d differs from the high-frequency transmission line 10a in that it contains a signal line 3a and a signal line 3b instead of the signal line 3.

[0037] Signal lines 3a and 3b are conductor patterns formed on the outer layer P1. Signal line 3b is positioned in a direction aligned with signal line 4 in the layer stacking direction. Signal lines 3a and 3b are connected to signal contact hole 5 and run along a straight line through it. This allows a high-frequency signal input from signal line 4 into the interlayer transmission line 62 to be branched and output to signal lines 3a and 3b. 1-6. Beneficial effects

[0038] According to the examples described above, the following beneficial effects are achieved.

[0039] (1) The contact hole diameter r1 is determined such that propagation of a high-frequency signal through an interlayer transmission line 62 via multimode transmission (multimode interference transmission) is possible. That is, the contact hole diameter r1 is set to a value larger than the contact hole diameter that allows propagation of a high-frequency signal through the interlayer transmission line 62 via single-mode transmission. Therefore, the high-frequency transmission lines 10 and 10a to 10d can be mass-produced. At least one of the substrate thickness Ho, the inter-contact hole spacing Rd, and the contact hole diameter r1 of the respective high-frequency transmission lines 10 and 10a to 10d is designed to introduce a high-frequency signal from the interlayer transmission line 62 into the signal line 3 or 4 in the high-intensity range of the electric field.This suppresses transmission loss during propagation of the high-frequency signal through the interlayer transmission line 62. Therefore, high-frequency transmission lines 10 and 10a to 10d can be realized that can be mass-produced and suppress transmission loss.

[0040] (2) The high-frequency transmission lines 10a to 10d according to the respective second to fourth examples each contain interlayer contact holes 7a, which are arranged at positions above or below the signal lines 3 and 4. This can enable an even more effective limitation of a high-frequency signal to or within the interlayer transmission line 62 of the respective high-frequency transmission lines 10a to 10d and thus even better suppress or reduce the transmission loss. 2. Further Examples 2-1. Sixth Example 2-1-1. Difference from the previous examples

[0041] The basic configuration of the subsequent examples is the same as that of the examples above. Therefore, the subsequent examples are described primarily in terms of their differences from the examples above, and the description of the common configurations is not repeated. Note that the reference symbols, which are the same as in the examples above, denote the same configurations. Therefore, reference is also made to the description above.

[0042] The high-frequency transmission line according to the further examples differs from that of the examples above in that it contains several inner layer connection surfaces to reduce the width of the interlayer transmission line.

[0043] In the examples above, at least one of the substrate thickness Ho, the inter-contact hole spacing Rd, and the contact hole diameter r1 is adjusted to modify the electric field distribution. Here, the substrate thickness Ho cannot be freely adjusted due to limitations imposed by the device in which the high-frequency transmission line is to be used. In this case, the substrate thickness Ho can remain constant, and the inter-contact hole spacing Rd can be reduced to modify the electric field distribution. Reducing the inter-contact hole spacing Rd reduces the area in which the electric field of the high-frequency signal is distributed between the signal contact hole 5 and the grounding contact holes 7 and 7a, and thus reduces the number of higher-order modes excited in the interlayer transmission line 62.Therefore, a high-intensity area of ​​the electric field distribution can be more easily formed in the output section of the interlayer transmission line 62.

[0044] However, a reduction in the inter-contact hole spacing Rd can increase the probability that the signal contact hole 5 and the grounding contact holes 7 and 7a become electrically coupled, as described in Fig. Figure 13 illustrates this. The grounding contact holes 7 and 7a are formed by drilling holes in the dielectric layers and then plating them. When the holes are formed by drilling, fractures or cracks C1 and C2 can occur, and the plating can sink into these cracks. If the inter-contact hole spacing Rd is small, this sinking of the plating into cracks C1 and C2 can cause the signal contact hole 5 and the grounding contact holes 7 and 7a to become electrically coupled. Therefore, for reliability, the inter-contact hole spacing Rd should be greater than or equal to a predetermined value. For example, it is desirable for the inter-contact hole spacing Rd to be equal to or greater than 0.45 mm.

[0045] Therefore, according to the further examples, the high-frequency transmission line contains several inner layer connection surfaces. In the high-frequency transmission line, the inner layer connection surfaces define quasi-walls that project further into the intermediate layer transmission line 62 than at least one of the side walls of the signal contact hole 5 and the side walls of the grounding contact holes 7 and 7a, resulting in a reduction of the width of the intermediate layer transmission line 62.

[0046] The configuration of a high-frequency transmission line 10e according to a sixth example is described below with reference to the Fig. described in sections 14 to 16. The high-frequency transmission line 10e contains a multilayer substrate 2e, signal lines 3 and 4, a signal contact hole 5, six through holes 7, two intermediate layer contact holes 7a, three first inner layer connection surfaces 6a and three second inner layer connection surfaces 6b.

[0047] The multilayer substrate 2e contains four dielectric layers L1 to L4 and five pattern layers P1 to P5, between which the respective dielectric layers L1 to L4 are arranged. Hereinafter, the pattern layers P1 and P5, which are arranged beneath the pattern layers P1 to P5 on the outer surfaces of the multilayer substrate 2e, are referred to as outer layers, and the other pattern layers P2 to P4 are referred to as intermediate layers.

[0048] Signal lines 3 and 4 are formed on the respective outer layers P1 and P5. A grounding plane 6, a first inner layer connection surface 6a, and a second inner layer connection surface 6b are formed on each of the intermediate layers P2 to P4. That is, in each of the intermediate layers P2 to P4, one section of a conductor pattern serves as grounding plane 6, another section of the conductor pattern serves as the first inner layer connection surface 6a, and yet another section of the conductor pattern serves as the second inner layer connection surface 6b.

[0049] The first inner layer connection surfaces 6a are conductor patterns that are coupled to the eight earthing contact holes 7 and 7a and are integrated with the earthing levels 6, or form a unit. As shown in Fig. As shown in Figure 15, the first inner layer connection surfaces 6a are annular conductor patterns coupled to the side walls of the eight grounding contact holes 7 and 7a, facing the signal contact hole 5 and projecting towards the signal contact hole 5. The second inner layer connection surfaces 6b are annular conductor patterns coupled to the signal contact hole 5 and projecting from the side wall of the signal contact hole 5 towards the eight grounding contact holes 7 and 7a. The first inner layer connection surfaces 6a and the second inner layer connection surfaces 6b are annular conductor patterns defined by two concentric circles arranged around the signal contact hole 5.

[0050] The three first inner layer contact surfaces 6a and the three second inner layer contact surfaces 6b are arranged along the layer stack direction at intervals equal to or less than 1 / 4 of the wavelength λg of the high-frequency signal propagating through the interlayer transmission line 62. That is, the thickness of the dielectric layers L2 and L3 is equal to or less than λg / 4. In this way, a quasi-side surface is formed by the edges of the three first inner layer contact surfaces 6a at a position closer to the signal contact hole 5 than the side walls of the eight grounding contact holes 7 and 7a, as shown in Fig. Figure 16 shows that a quasi-side surface is formed by the edges of the three second inner layer connection surfaces 6b at a position closer to the grounding contact holes 7 and 7a than the side wall of the signal contact hole 5. An interlayer transmission line 62, having a width smaller than the inter-contact hole spacing Rd, is formed between the two quasi-side surfaces. 2-1-2. Analytical result

[0051] Fig. Figure 17 presents the analytical result of the electric field distribution in a cross-section in the layer stack direction of the high-frequency transmission line 10e, which contains the inner layer connection surfaces. As a comparative example, Fig. 18 represents the analytical result of the electric field distribution in a cross-section in the layer stack direction of a high-frequency transmission line that does not contain any inner layer connection surfaces, which is the same as the high-frequency transmission line 10e without the first inner layer connection surfaces 6a and the second inner layer connection surfaces 6b. As is shown in Fig. As shown in Figure 17, the electric field distribution in the interlayer transmission line 62 of the high-frequency transmission line 10e is narrow compared to the comparison example. Fig. Figure 19 illustrates the transmission loss as a function of frequency in the high-frequency transmission line 10e and in the comparison example. As shown in Fig. As shown in Figure 19, the transmission loss within the frequency range of 74 to 82 GHz in the high-frequency transmission line 10e is smaller than in the comparison example. 2-2. Seventh example

[0052] A high-frequency transmission line 10f according to a seventh example is described below with reference to Fig. The high-frequency transmission line 10f is described in Figure 20. It contains a multilayer substrate 2f, signal lines 3 and 4, a signal contact hole 5, six through-contact holes 7 (not shown), two inner-layer contact holes 7a, and first inner-layer contact surfaces 6a. That is, the high-frequency transmission line 10f differs from the high-frequency transmission line 10e in that it does not contain the second inner-layer contact surfaces 6b. Instead, the length of the first inner-layer contact surfaces 6a of the high-frequency transmission line 10f, which project towards the signal contact hole 5, is greater than that of the first inner-layer contact surfaces 6a of the high-frequency transmission line 10e. In other words, the ring of the respective first inner-layer contact surfaces 6a has a greater width.In the high-frequency transmission line 10f, which has such a configuration, the width of the inner layer transmission line 62 can be reduced to a level similar to that of the high-frequency transmission line 10e. 2-3. Eighth example

[0053] A high-frequency transmission line 10g according to an eighth example is described below with reference to Fig. 21 described. The high-frequency transmission line 10g contains a multilayer substrate 2g, signal lines 3 and 4, one signal contact hole 5, six through-contact holes 7 (not shown), two intermediate-layer contact holes 7a, and second inner-layer contact pads 6b. That is, the high-frequency transmission line 10g differs from the high-frequency transmission line 10e in that it does not contain the first inner-layer contact pads 6a. Instead, the lengths of the second inner-layer contact pads 6b of the high-frequency transmission line 10g, which project towards the eight grounding contact holes 7 and 7a, are greater than those of the second inner-layer contact pads 6b of the high-frequency transmission line 10e. In other words, the ring of the respective second inner-layer contact pads 6b has a greater width.In the high-frequency transmission line 10g, which has such a configuration, the width of the inner layer transmission line 62 can be reduced to a level similar to that of the high-frequency transmission line 10e. 2-4. Beneficial effects

[0054] According to the further examples described above, the following beneficial effects are achieved in addition to the beneficial effects (1) and (2) of the examples described before.

[0055] (3) Since the high-frequency transmission lines 10e to 10g each contain at least one of the first inner layer contact surfaces 6a and one of the second inner layer contact surfaces 6b, the number of higher-order modes of the high-frequency signal excited by the intermediate layer transmission lines 62 of the respective high-frequency transmission lines 10e to 10g is reduced, and the influence of higher-order modes is suppressed. As a result, high-intensity regions of the electric field distribution are formed in the output section of the intermediate layer transmission line 62, and thereby transmission losses of the high-frequency transmission lines 10e to 10g are suppressed. That is, the high-frequency transmission lines 10e to 10g achieve the same advantageous effects as in a case where the inter-contact hole spacing Rd is small.

[0056] (4) In each of the high-frequency transmission lines 10e to 10g, the intervals of the first interlayer contact surfaces 6a and the second interlayer contact surfaces 6b in the layer stack direction are equal to or less than λg / 4. As a result, the quasi-side surface that protrudes closer to the grounding contact holes 7 and 7a than the side wall of the signal contact hole 5, and / or the quasi-side surface that protrudes closer to the signal contact hole 5 than the grounding contact holes 7 and 7a, is achieved. Therefore, the high-frequency transmission lines 10e to 10g achieve the same advantageous effects as in a case where the inter-contact hole spacing Rd is small.

[0057] (5) The first inner layer connection surfaces 6a and the second inner layer connection surfaces 6b may be formed in the same layer as the earthing level 6. 3. Embodiment according to the invention 3-1. Ninth example 3-1-1. Difference from the examples above

[0058] The basic configuration of this embodiment is the same as in the second example. Therefore, this embodiment is described mainly in terms of its differences from the second example, and the description of the common configurations is not repeated. Note that the reference numerals, which are the same as in the examples above, denote the same configurations. Therefore, reference is made to the description above.

[0059] A high-frequency transmission line according to the embodiment differs from that of the second example in that the interlayer contact holes have a so-called butt structure or stub line structure.

[0060] The configuration of a high-frequency transmission line 10h according to a ninth example of the embodiment is described below with reference to the Fig. 22 and Fig. 23 described. The high-frequency transmission line 10h contains a multilayer substrate 2h, signal lines 3 and 4, one signal contact hole 5, six through contact holes 7 and two interlayer contact holes 7b. The high-frequency transmission line 10h is subjected to an electric field distribution matching as in the examples above.

[0061] The multilayer substrate 2h contains six dielectric layers L1 to L6 and seven pattern layers P1 to P7, between which the respective dielectric layers L1 to L6 are arranged. Hereinafter, the pattern layers P1 and P7, which are arranged beneath the pattern layers P1 to P7 on the outer surfaces of the multilayer substrate 2h, are referred to as the outer layers, and the other pattern layers P2 to P6 are referred to as the intermediate layers.

[0062] Signal lines 3 and 4 are formed on the respective outer layers P1 and P7. Grounding planes 6 are formed in the intermediate layers P2 to P6. The two intermediate layer contact holes 7b penetrate the dielectric layers L3 and L4 in the middle beneath the six dielectric layers L1 to L6 and electrically couple the two grounding planes 6, which are formed in the respective intermediate layers P3 and P5.

[0063] The dielectric layer L2 is arranged above the interlayer contact holes 7b, and one of the grounding planes 6 is arranged above dielectric layer L2. The dielectric layer L5 is arranged below the interlayer contact holes 7b, and another of the grounding planes 6 is arranged below dielectric layer L5. The dielectric layers L2 and L5 serve as adhesives for mounting the grounding planes 6. That is, dielectric layers are always arranged above and below the interlayer contact holes 7b. The through-holes of the interlayer contact holes 7b are filled with the same dielectric material that comprises the dielectric layers L1 to L6.

[0064] A high-frequency transmission line 20a, which has no interlayer contact holes, is in the Fig. 24 and Fig. Figure 25 shows that the high-frequency transmission line 20a does not contain any grounding contact holes at positions that overlap with the signal lines 30 and 40. Therefore, an electric field Ea of the high-frequency signal leaks in the high-frequency transmission line 20a from an intermediate layer transmission line 62 to the dielectric layers L2 to L5 below the signal line 30 and above the signal line 40.

[0065] A high-frequency transmission line 20b, which has interlayer contact holes 70a, is in the Fig. 26 and Fig. Figure 27 shows that in the high-frequency transmission line 20b, an electric field Eb leaks from an interlayer transmission line 62 to the dielectric layers L2 to L5, which are arranged above and below the interlayer contact holes 70a. When the electric field leaks from the interlayer transmission line 62, the transmission loss increases by a corresponding amount. Therefore, it is desirable to suppress the leakage of the electric field.

[0066] Therefore, in this embodiment, the interlayer contact holes 7b have a so-called butt structure to suppress electric field leakage and reduce transmission loss. That is, the interlayer contact holes 7b have dimensions such that a first electric field E1 and a second electric field E2 leak from the interlayer transmission line 62 towards the interlayer contact holes 7b and cancel each other out. The first electric field E1 is an electric leakage field that passes through the dielectric layers L2 and L5, which are arranged between the interlayer contact holes 7b and the grounding plane 6 above the interlayer contact holes 7b, and between the interlayer contact holes 7b and the grounding plane 6 below the interlayer contact holes 7b, respectively.The second electric field E2 is an electric leakage field that enters one of the interlayer contact holes 7b. The second electric field E2 enters the interlayer contact hole 7b and is reflected at the grounding plane 6 above or below the interlayer contact hole 7b.

[0067] In particular, the width W of the interlayer contact hole 7b, orthogonal to the layer stacking direction in the cross-section passing through the central axes of the interlayer contact hole 7b and the signal contact hole 5, is equal to λg / 2, thus generating a standing wave in the interlayer contact hole 7b. Furthermore, the height H of the interlayer contact hole 7b in the cross-section is equal to λg / 4, so that the phase of the second electric field E2 is shifted by 180 degrees with respect to the phase of the first electric field E1. That is, the interlayer contact hole 7b is designed as a cylinder having a diameter of λg / 2 and a height of λg / 4. 3-1-2. Analytical result

[0068] Fig. Figure 28 presents the analytical result of the electric field distribution of the high-frequency transmission line 10h in a cross-section in the layer stack direction. As a comparative example, Fig. 29 in a cross-section in the layer stack direction represents the analytical result of the electric field distribution of a high-frequency transmission line containing interlayer contact holes with a height H of λg / 4 and a width W of λg / 6. A comparison of the sections formed by the ovals in the Fig. 28 and Fig. 29 are surrounded, shows that in the comparative example the electric field leaks to the dielectric layers between the interlayer contact holes and the grounding plane 6, which is located above the interlayer contact holes, and the contact holes and the grounding plane 6, which is located below the interlayer contact holes, while the leakage of the electric field in the high-frequency transmission line 10h is suppressed. Fig. Figure 30 represents the transmission loss as a function of frequency in the high-frequency transmission line 10h and in the comparison example. As shown in Fig. As shown in Figure 30, the transmission loss of the high-frequency transmission line 10h within the frequency range of 63 to 83 GHz is lower than that of the comparison example. In particular, the transmission loss of the high-frequency transmission line 10h is 0.5 dB better at 77 GHz compared to the comparison example. 3-2. Tenth example

[0069] A high-frequency transmission line 10i according to a tenth example according to the embodiment is below referred to as Fig. 31. The high-frequency transmission line 10i contains a multilayer substrate 2i, signal lines 3 and 4, a signal contact hole 5, six through-contact holes 7, and six interlayer contact holes 7b. That is, the high-frequency transmission line 10i contains four more interlayer contact holes 7b than the high-frequency transmission line 10h. The additional four interlayer contact holes 7b are located further away from the signal contact hole 5 than the six through-contact holes 7 and further radially outward than the six through-contact holes 7. The high-frequency transmission line 10i, which has such a configuration, can suppress electric field leakage better than the high-frequency transmission line 10h and thereby reduce transmission loss. 3-3. Beneficial Effects

[0070] According to the embodiment of the invention described above, the following advantageous effects are achieved in addition to the advantageous effects (1) and (2) of the examples described above.

[0071] (6) Since the interlayer contact holes 7b have dimensions that cause the first electric field E1 and the second electric field E2 to cancel each other out, the leakage of the electric fields from the interlayer transmission line 62 to the dielectric layers can be suppressed. This can suppress the transmission loss of the high-frequency signal.

[0072] (7) Since the width W of the interlayer contact holes 7b is equal to λg / 2, the second electric field E2 entering the interlayer contact holes 7b becomes a standing wave, and since the height H of the interlayer contact holes 7b is equal to λg / 4, the phase of the second electric field E2, which is a standing wave, is shifted by 180 degrees with respect to the first electric field E1 passing through the dielectric layers. This causes the first electric field E1 and the second electric field E2 to cancel each other out, and electric field leakage can be suppressed. 4. Further embodiment 4-1. Difference from the embodiment above

[0073] The basic configuration of the further embodiment is the same as that of the sixth example. A high-frequency transmission line 10j according to the further embodiment includes a multilayer substrate 2j having the same configuration as the multilayer substrate 2i. The high-frequency transmission line 10j has a configuration in which the interlayer contact holes 7a of the high-frequency transmission line 10e are replaced by the interlayer contact holes 7b of the high-frequency transmission line 10h according to the ninth example. That is, the high-frequency transmission line 10j undergoes electric field matching and includes in-layer contact surfaces and in-layer contact holes having a butt-joint structure.

[0074] Fig. Figure 32 presents the analytical result of the electric field distribution of the high-frequency transmission line 10j in a cross-section in the layer stack direction. A comparison of the electric field of the high-frequency transmission line 10j, which in Fig. 32 is shown, and the electric field of the high-frequency transmission line 10e, which is in Fig.Figure 18 shows that the leakage of the electric field to the dielectric layers between the interlayer contact holes and the grounding planes above and below the interlayer contact holes is suppressed more in the high-frequency transmission line 10j than in the high-frequency transmission line 10e. That is, in the high-frequency transmission line 10j, the extent of the electric field distribution in an interlayer transmission line is suppressed, and leakage of an electric field to the dielectric layers between the interlayer contact holes and the grounding planes above and below the interlayer contact holes is suppressed. 4-2. Beneficial Effects

[0075] According to the further embodiment described above, the advantageous effects described above (1) to (7) are achieved. Further embodiments (a) In the embodiments described above, the number of layers stacked in the multilayer substrates 2 and 2a to 2j is not limited. The number of layers stacked in the multilayer substrates 2 and 2a to 2j can be suitably determined. The number of grounding contact holes 7 and 7a can also be suitably determined. (b) The structure of the through-contact holes 7 is not limited to one containing a through-hole. The through-contact holes 7 can be metal walls arranged around the signal contact hole 5 and coupled to the grounding planes. For example, the through-contact holes 7 can be arc-shaped metal walls arranged along the circumference of circle C. The through-contact holes 7 can be metal grooves, each having a rectangular cross-section orthogonal to the layer stacking direction and arranged around the signal contact hole 5. In the high-frequency transmission line 10, for example, one of the three through-contact holes 7 can be a metal groove, or two metal grooves can be arranged between which the signal lines 3 and 4 are arranged. (c) In the above embodiments, the height H and width W of the respective interlayer contact holes 7b need not be exactly λg / 2 and λg / 4, respectively. The interlayer contact holes 7b need not completely cancel the first electric field E1 and the second electric field E2, but may cancel them to an extent that leads to a reduction in transmission loss. The height H of the interlayer contact holes 7b can satisfy 0 < Ho < λg and is preferably (λg / 4) × 0.8 < Ho < (λg / 4) × 1.2. The width W of the interlayer contact holes 7b can satisfy 0 < Wo < λg and is preferably (λg / 2)×0.8 <wo<(λg 2)×1,2.(d) Several functions of a single component in the embodiments described above can alternatively be achieved by several components, or a single function of a single component can alternatively be achieved by several components. Several functions of several components can alternatively be achieved by a single component, or a single function achieved by several components can alternatively be achieved by a single component. Part of the configuration of the embodiments described above can be omitted. Alternatively, at least part of the configuration of the embodiments described above can be added to or replaced by a configuration of another embodiment described above. (e) In addition to the high-frequency transmission line described above, the invention can be implemented in various modes, for example as a system which includes the high-frequency transmission line as a component, and as a method for manufacturing the high-frequency transmission line.

Claims

High-frequency transmission line (10) comprising: a multilayer substrate (2, 2a to 2j) containing several dielectric layers (L1 to L6) stacked on top of each other; signal lines (3, 3a, 3b, 4) formed on two outer surfaces of the multilayer substrate (2, 2a to 2j); a signal contact hole (5) coupling the signal lines (3, 3a, 3b, 4) formed on the two outer surfaces; at least one grounding plane (6) arranged between the dielectric layers (L1 to L6), contained in the multilayer substrate (2, 2a to 2j), and surrounding a clearance area (61) arranged around the signal contact hole (5); and several grounding contact holes (7, 7a, 7b) that penetrate at least one of the dielectric layers (L1 to L6) in a layer stacking direction, surround the signal contact hole (5) and are electrically coupled to the grounding plane (6),wherein an interlayer transmission line (62) is defined through and between the signal contact hole (5) and the grounding contact holes (7, 7a, 7b), wherein a high-frequency signal is transmitted in the layer stack direction through the interlayer transmission line (62), a contact hole diameter of the signal contact hole (5) is set to a dimension that results in propagation in the interlayer transmission line (62) by means of multimode transmission, and the high-frequency signal in multimode transmission forms a high-intensity region, which has a high-intensity electric field in one transmission direction, and a low-intensity region, which has a low-intensity electric field in the transmission direction, and at least one of an inter-contact hole spacing between the signal contact hole (5) and the respective grounding contact holes (7, 7a, 7b),the contact hole diameter and substrate thickness of the multilayer substrate (2, 2a to 2j) for introducing the high-frequency signal from the interlayer transmission line (62) into the signal lines (3, 3a, 3b, 4) in the high-intensity range of multimode transmission, the dielectric layers (L1 to L6) are three or more dielectric layers (L1 to L6) and the at least one grounding plane (6) are several grounding planes (6), the grounding contact holes (7, 7a, 7b) contain interlayer contact holes (7b) that penetrate at least one of the dielectric layers (L1 to L6) excluding the dielectric layers (L1 to L6) on which the signal lines (3, 3a, 3b, 4) are formed, and electrically couple the grounding planes (6) to each other, and the interlayer contact holes (7b) each have a dimension that allows for mutual cancellation of a first electric field (E1) and a second electric field (E2) leads towherein the first electric field (E1) is an electric leakage field leaking from the interlayer transmission line (62) to the interlayer contact holes (7b) and passing between the interlayer contact holes (7b) and the ground plane (6) above the interlayer contact holes (7b) and between the interlayer contact holes (7b) and the ground plane (6) below the interlayer contact holes (7b), and wherein the second electric field (E2) is an electric leakage field leaking from the interlayer transmission line (62) to the interlayer contact holes (7b), passing through the interlayer contact holes (7b) and being reflected at the ground plane (6) above or below the interlayer contact holes (7b). High-frequency transmission line (10) according to claim 1, wherein the interlayer transmission line (62) is a ring-shaped line arranged around the signal in a plane perpendicular to the layer stacking direction, and the multilayer substrate (2, 2a to 2j) contains in an inner layer several line patterns (6a, 6b) which are coupled to at least one of the signal contact hole (5) and the grounding contact holes (7, 7a, 7b) and project from the signal contact hole (5) to the grounding contact holes (7, 7a, 7b) and / or from the grounding contact holes (7, 7a, 7b) to the signal contact hole (5). High-frequency transmission line (10) according to claim 2, wherein the line patterns (6a, 6b) are arranged in the layer stack direction at intervals of 1 / 4 or less of a wavelength of the high-frequency signal propagating through the interlayer transmission line (62). High-frequency transmission line (10) according to claim 2 or 3, wherein a respective pattern layer of several pattern layers (P2 to P4) is arranged between each of the two dielectric layers (L1 to L6), each of the line patterns (6a, 6b) is integrated with a respective grounding plane (6) of the grounding planes (6) and is formed in a respective pattern layer of the pattern layers (P2 to P4). High-frequency transmission line (10) according to claim 1, wherein the interlayer contact holes (7b) in a cross-section passing through the center of the signal contact hole (5) and the center of the corresponding interlayer contact hole (7b) each have a height which is 1 / 4 of a wavelength of the high-frequency signal in the interlayer transmission line (62) and have a width which is 1 / 2 of the wavelength of the high-frequency signal which propagates through the interlayer transmission line (62). High-frequency transmission line (10) according to one of claims 1 to 5, wherein the contact hole diameter of the signal contact hole (5), which leads to transmission of the high-frequency signal through the interlayer transmission line (62) in multimode transmission, fc < c π ε r D + d 2 fulfilled where d is an outer diameter of the signal contact hole (5), D is a diameter of a circle (C) around the signal contact hole (5), wherein the grounding contact holes (7, 7a, 7b) are externally tangential to the circle (C), εr is a relative permittivity of a dielectric body arranged between the signal contact hole (5), which serves as an inner conductor, and the grounding contact holes (7, 7a, 7b), which serve as an outer conductor, c is the speed of light, and fc is a critical frequency of a coaxial transmission line formed by the inner conductor and the outer conductor.

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