High-frequency circuit connection structure

Abstract

A radio-frequency line connection structure (1) includes microstrip lines (1-14, 1-15) and a junction (1-13) that bends a line extending direction at a position where the microstrip lines (1-14, 1-15) are connected to each other. Spaces (1-5, 1-6) where a base material (1-2) is removed are formed on the inner side and the outer side of the junction (1-13). The total volume of the space (1-5) on the inner side is less than the total volume of the space (1-6) on the outer side.

Description

Technical Field

[0001] The present invention relates to a high-frequency line connection structure for connecting high-frequency lines having different stretching directions.

Background Art

[0002] In an example of constructing an optical communication network characterized by high speed and wide bandwidth, a large number of modules such as broadband high-frequency amplifiers and optical transceivers are introduced. Inside and outside these modules, a large number of high-frequency lines capable of transmitting high-frequency signals with low loss and low reflection loss are mounted at relatively high density. These high-frequency lines are rarely composed only of a straight wiring shape without bending in the same horizontal plane. In recent years, with the acceleration of three-dimensional component mounting inside and outside modules, high-frequency lines have come to exhibit more complex wiring shapes.

[0003] On the other hand, in a conventionally used technique, when bending a high-frequency line formed in the same plane at a right angle, for example, chamfering of the right-angle bent portion of a microstrip line is widely performed (see Non-Patent Document 1). By the chamfering process, it becomes possible to suppress the effective impedance reduction of the high-frequency line due to the expansion of the metal area at the bent portion. Due to this impedance reduction suppression effect, low reflection loss characteristics of high-frequency signals at the bent portion are obtained, and it is widely known that desired impedance matching can be obtained over the entire high-frequency line including the bent portion.

[0004] In addition, high-frequency lines connecting between different modules or between components inside a module are not necessarily formed only in the same plane as described above. For the purpose of improving the degree of freedom in the wiring design of high-frequency lines, there are many cases where high-frequency lines are formed through connection structures between different layers. In the interlayer connection of a rigid substrate, many discussions have mainly been made about the stub structure. It is widely known that the high-frequency characteristics are improved by shortening the length of the stub (see Non-Patent Document 2).

[0005] If the thickness of the insulating layer forming the microstrip line is 30 μm or 100 μm, the width of the chamfered line finally obtained by the chamfering process will not approach the manufacturing limit. However, in recent high-density high-frequency wirings such as RDL (Re-Distributed Layer), the thickness of the insulating layer has been thinned to about several μm, and accordingly, the width of the microstrip line also tends to approach a region close to the manufacturing limit of several μm.

[0006] In high-density wirings such as RDL, it is assumed that introducing a chamfered structure for the bent portion of the high-frequency line exceeds the manufacturing limit. Therefore, it is not easy to match the characteristic impedance at the bent portion.

[0007] In the current product base using RDL, the bit rate of the high-frequency signal propagating through the high-frequency line is within several Gbps. Furthermore, the line length of the high-frequency line in RDL is currently short compared to the in-tube wavelength of the high-frequency signal. Therefore, the above-mentioned characteristic impedance mismatch has not been widely recognized as a problem at this stage. However, in the future with broadband expansion and the extension of the high-frequency line length due to the increase in the area of RDL, the characteristic impedance mismatch at the bent portion of the high-frequency line may become an inevitable issue.

[0008] Also, in the case of the interlayer connection structure, even if the length of the above stub is set to zero, it is not necessarily sufficient for future broadband expansion. The reason is that when the high-frequency line bends in different directions in the three-dimensional space, similar to the case of bending the microstrip line in the two-dimensional plane, effective capacitance appears in the bent region, resulting in a decrease in the characteristic impedance.

[0009] When bending a high-frequency line embedded in a multilayer insulator for connection between different layers, generally a pseudo coaxial line structure is introduced. When applying the chamfered structure introduced at the bend of a microstrip line in the same plane to the pseudo coaxial line structure, it becomes necessary to reduce the diameter of the center conductor of the pseudo coaxial line penetrating the layers. However, since there are manufacturing limitations in reducing the diameter of the center conductor, an ideal structure cannot always be obtained, and there are naturally limitations in characteristic impedance matching at the bend.

Prior Art Documents

Non-Patent Documents

[0010]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0011] The present invention has been made to solve the above problems, and in a high-frequency line connection structure that connects the tips of high-frequency lines whose extending directions are different from each other, it aims to achieve characteristic impedance matching and smoothly transmit high-frequency signals without reflection.

Means for Solving the Problems

[0012] The high-frequency line connection structure of the present invention includes a first high-frequency line formed on the surface of a base material made of an insulator or a semi-insulating semiconductor or in the base material, a second high-frequency line formed on the surface of the base material or in the base material and having a different extending direction from that of the first high-frequency line, and a connection portion that bends the extending direction of the line at a location where the first high-frequency line and the second high-frequency line are connected. Among the above-mentioned Spaces where the base material is removed are formed on both the inner peripheral side and the outer peripheral side of the connection portion, and the connection portion ones, when the number of the spaces on the inner peripheral side is M (M is an integer of 1 or more) and the number of the spaces on the outer peripheral side is N ( The total volume of the space on the inner peripheral side is smaller than the total volume of the space on the outer peripheral side. N is an integer of 1 or more), satisfying the relationship of M ≤ N is a first high-frequency line formed on the surface of a base material made of an insulator or a semi-insulating semiconductor or in the base material, a second high-frequency line formed on the surface of the base material or in the base material and having a different extending direction from that of the first high-frequency line, and a connection part that bends the extending direction of the line at a location where the first It is characterized by this.

[0013] Also, the high-frequency line connection structure of the present invention high-frequency line and the second high-frequency line are connected, and a space where the above-mentioned base material is removed is formed only on the outer peripheral side of the connection part or on both the inner peripheral side and the outer peripheral side of the connection part. When the spaces are formed on both the inner peripheral side and the outer peripheral side of the connection part, the total volume of the spaces on the inner peripheral side is smaller than the total volume of the spaces on the outer peripheral side. is a first high-frequency line formed on the surface of a base material made of an insulator or a semi-insulating semiconductor or in the base material, a second high-frequency line formed on the surface of the base material or in the base material and having a different extending direction from that of the first high-frequency line, and a connection part that bends the extending direction of the line at a location where the first high-frequency line and the second high-frequency line are connected, and a space where the above-mentioned base material is removed is formed only on the outer peripheral side of the connection part or on both the inner peripheral side and the outer peripheral side of the connection part. When the spaces are formed on both the inner peripheral side and the outer peripheral side of the connection part, the total volume of the spaces on the inner peripheral side is smaller than the total volume of the spaces on the outer peripheral side. is a first high-frequency line formed on the surface of a base material made of an insulator or a semi-insulating semiconductor or in the base material, a second high-frequency line formed on the surface of the base material or in the base material and having a different extending direction from that of the first high-frequency line, and a connection part that bends the extending direction of the line at a location where the first high-frequency line and the second high-frequency line are connected, and a space where the above-mentioned base material is removed is formed only on the outer peripheral side of the connection part or on both the inner peripheral side and the outer peripheral side of the connection part. When the spaces are formed on both the inner peripheral side and the outer peripheral side of the connection part, the total volume of the spaces on the inner peripheral side is smaller than the total volume of the spaces on the outer peripheral side. Both the first high-frequency line and the second high-frequency line are formed in the base material having a multilayer structure. The first high-frequency line is formed in a specific layer in the base material, and the second high-frequency line is formed so as to penetrate a plurality of layers in the base material. It is characterized by this. Also, in one configuration example of the high-frequency line connection structure of the present invention, the space is formed so as to be in contact with a ground plane formed in the base material around at least one of the signal lines of the first high-frequency line and the second high-frequency line, or is formed at a position adjacent to the ground plane through the base material and functions as a capacitive adjustment portion. It is characterized by this. Also, the high-frequency line connection structure of the present invention When the spaces are formed on both the inner peripheral side and the outer peripheral side of the connection part, is a first high-frequency line formed on the surface of a base material made of an insulator or a semi-insulating semiconductor or in the base material, a second high-frequency line formed on the surface of the base material or in the base material and having a different extending direction from that of the first high-frequency line, and the first high-frequency line and a second high-frequency line formed on the surface of the base material or in the base material and having a different extending direction from that of the first high-frequency line, and the first ​ ​ ​The space is formed so as to be in contact with at least one of the signal lines of the first high-frequency line and the second high-frequency line around the signal line, or is formed at a position adjacent to the signal line via the base material, and functions as an inductive adjustment unit.

[0014] Also, in one configuration example of the high-frequency line connection structure of the present invention, the first high-frequency line and the second high-frequency line are any one of a microstrip line, a coplanar line, and a strip line. Also, the high-frequency line connection structure of the present invention ​ ​ ​ ​ ​ ​ ​ The first high-frequency line is a strip line, and the second high-frequency line is a pseudo coaxial line composed of a signal via formed to penetrate a plurality of layers in the base material, a ground plane formed to surround the signal via, and the base material filling the space between the signal via and the ground plane. Also, in one configuration example of the high-frequency line connection structure of the present invention, ​ ​ The space on the inner peripheral side of the connection part is formed so as to be in contact with the ground plane formed in the base material around the signal lines of both the first high-frequency line and the second high-frequency line, or is formed at a position adjacent to the ground plane via the base material, and the space on the outer peripheral side of the connection part is formed so as to be in contact with the signal line of the first high-frequency line and is formed at a position adjacent to the signal line of the second high-frequency line via the base material.

[0015] Also, the high-frequency line connection structure of the present invention ​ ​ ​ a connection that bends the extending direction of the line at the location where the high-frequency line and the second high-frequency line are connected and includes a connection portion, and spaces from which the base material is removed are formed on both the inner peripheral side and the outer peripheral side of the connection portion and the total volume of the space on the inner peripheral side of the connection portion is smaller than the total volume of the space on the outer peripheral side and an insulator having a relative dielectric constant smaller than that of the base material, or a semi-insulating semiconductor having a relative dielectric constant smaller than that of the base material is filled inside the spaces on the inner peripheral side and the outer peripheral side of the connection portion

Figure 1

Figure 2A

Figure 2B

Advantages of the Invention

[0016] According to the present invention, at the location where the first high-frequency line and the second high-frequency line are connected, a connection portion that bends the extending direction of the line is provided. A space where the base material is removed is formed only on the outer peripheral side of the connection portion, or on both the inner peripheral side and the outer peripheral side of the connection portion. When spaces are formed on both the inner peripheral side and the outer peripheral side of the connection portion, the total volume of the space on the inner peripheral side is made smaller than the total volume of the space on the outer peripheral side. Thereby, in the present invention, impedance matching can be achieved at the connection portion connecting the first high-frequency line and the second high-frequency line and in the vicinity thereof, and the transmission of high-frequency signals can be performed smoothly without reflection.

Brief Description of the Drawings

[0017]

Figure 2C

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Figure 4B

Figure 4C

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Figure 14

Figure 15

Figure 16

[0018] Hereinafter, a high-frequency line connection structure according to an embodiment of the present invention will be described.

[0019] [First Embodiment] First, the high-frequency line connection structure 1 according to the first embodiment of the present invention will be described with reference to FIGS. 1, 2A, 2B, and 2C. FIG. 1 is a plan view of the high-frequency line connection structure 1, FIG. 2A is a cross-sectional view taken along line A-A' of FIG. 1, FIG. 2B is a cross-sectional view taken along line B-B' of FIG. 1, and FIG. 2C is a cross-sectional view taken along line C-C' of FIG. 1.

[0020] The high-frequency line connection structure 1 includes two microstrip lines 1-14 and 1-15. The microstrip line 1-14 (the first high-frequency line) is composed of a base material 1-2 made of an insulator, a signal line 1-1a made of a conductor formed on the surface of the base material 1-2, and a ground plane 1-3 made of a conductor formed on the back surface of the base material 1-2. Examples of the material of the base material 1-2 include alumina ceramics.

[0021] The microstrip line 1-15 (the second high-frequency line) is composed of the base material 1-2, a signal line 1-1b made of a conductor formed on the surface of the base material 1-2, and the ground plane 1-3.

[0022] Since the extending direction of the signal line 1-1a is different from that of the signal line 1-1b, a connection portion 1-13 for bending the extending direction of the line is required at the location where the signal line 1-1a and the signal line 1-1b are connected.

[0023] In this embodiment, the extending direction of the line bends at a right angle at the connection portion 1-13. However, in the base material 1-2 on the inner peripheral side and the outer peripheral side of the connection portion 1-13, spaces 1-5 and 1-6 are formed where the base material 1-2 is removed from the surface to the ground plane 1-3. The interiors of the spaces 1-5 and 1-6 are filled with air or an inert gas such as N2. Also, as will be described later, the interiors of the spaces 1-5 and 1-6 may be filled with an insulator or a semi-insulating semiconductor.

[0024] The total volume of the inner peripheral space 1-5 is formed to be smaller than the total volume of the outer peripheral space 1-6. Thus, in this embodiment, by providing the spaces 1-5 and 1-6, it is possible to suppress the reduction in impedance due to the increase in the electrical capacitance expressed at the connection portion 1-13 of the signal lines 1-1a and 1-1b, and to achieve the matching of the characteristic impedance over the entire microstrip lines 1-14 and 1-15. As a result, in the high-frequency line connection structure 1, it becomes possible to transmit high-frequency signals without loss between the signal line ends 1-4a and 1-4b of the microstrip lines 1-14 and 1-15.

[0025] On the other hand, as a method for characteristic impedance matching that does not rely on this embodiment, a method of physically processing the structure of the vertex of the connection portion (bending portion) has been proposed and is publicly known, and is widely used in various application destinations. A plan view of a conventional microstrip line disclosed in Non-Patent Document 1 is shown in FIG. 3. FIG. 4A is a cross-sectional view taken along line A-A' of FIG. 3, FIG. 4B is a cross-sectional view taken along line B-B' of FIG. 3, and FIG. 4C is a cross-sectional view taken along line C-C' of FIG. 3.

[0026] As shown in FIG. 3, according to Non-Patent Document 1, by chamfering the vertex 1-7 of the connection portion of the signal lines 1-1a and 1-1b, it is possible to suppress the increase in electrical capacitance. However, the wiring width on the RDL where the thickness of the base material 1-2 is several μm or on the package substrate where the thickness is several tens of μm is already close to the manufacturing limit, and even if a photomask that enables chamfering is used, it is difficult to process the vertex of the connection portion into a desired shape.

[0027] In addition, there is also a problem that disconnection of the signal line may occur in some cases due to the chamfering of the connection portion. Therefore, it can be said that it is not always appropriate to apply the technology disclosed in Non-Patent Document 1 to advanced fields such as RDL in the future.

[0028] On the one hand, according to this embodiment, by providing spaces 1-5 and 1-6 in the base materials 1-2 on the outer peripheral side and the inner peripheral side of the connection part 1-13 of the signal lines 1-1a and 1-1b, with a very simple and easily implementable structure, impedance matching can be achieved for all of the microstrip lines 1-14 and 1-15, and high-frequency signals can be transmitted without loss.

[0029] In this embodiment, the microstrip lines 1-14 and 1-15 are taken as examples for explanation. However, this embodiment may also be applied to a coplanar line in which a ground plane is formed around the signal lines 1-1a and 1-1b.

[0030] [Second Embodiment] Next, the high-frequency line connection structure 2 according to the second embodiment of the present invention will be described with reference to FIGS. 5 to 7. FIG. 5 is a cross-sectional view of the high-frequency line connection structure 2, and FIG. 6 is a cross-sectional view of the high-frequency line connection structure 2 cut along a plane parallel to the layer in which the signal line 2-1 is formed (the layer at the position of the D-D' line in FIG. 5). FIG. 7 is a bottom view of the high-frequency line connection structure 2. FIG. 5 shows a cross-section of the high-frequency line connection structure 2 cut at the position of the E-E' line in FIG. 6.

[0031] The above-described first embodiment was an example of the bending structure of the high-frequency line in the same two-dimensional plane, but this embodiment is an example in three-dimensional space. The high-frequency line connection structure 2 includes two high-frequency signal lines, specifically, a coplanar strip line 2-14 (the first high-frequency line) and a quasi-coaxial line 2-15 (the second high-frequency line).

[0032] The coplanar strip line 2-14 is composed of a signal line 2-1 made of a conductor formed in a base material 2-12 made of an insulator, a ground plane 2-2-1 made of a conductor formed in the base materials 2-12 on the left and right of the signal line 2-1, ground planes 2-2-4, 2-2-2 made of a plurality of layers of conductors formed in the base materials 2-12 above and below the signal line 2-1, a ground via 2-3-1 made of a conductor formed in the base material 2-12 so as to connect the plurality of layers of ground planes 2-2-1, 2-2-4, and a ground via 2-3-2 made of a conductor formed in the base material 2-12 so as to connect the plurality of layers of ground planes 2-2-1, 2-2-2. As the material of the base material 2-12, for example, there is alumina ceramics.

[0033] The pseudo coaxial line 2-15 is composed of a signal pad 2-4-1 made of a conductor formed in the base material 2-12 so as to connect to the signal line 2-1 and a plurality of layers of conductors below it, a signal via 2-5 made of a conductor formed in the base material 2-12 so as to connect the plurality of layers of signal pads 2-4-1, a ground plane 2-6 made of a plurality of layers of conductors formed in the base material 2-12 around the signal pad 2-4-1 in the same layer as the plurality of layers of ground planes 2-2-1, 2-2-2, an anti-pad region 2-7 which is a region where the ground plane 2-6 is selectively removed and filled by the base material 2-12, and a ground via 2-3-3 made of a conductor formed in the base material 2-12 so as to connect the plurality of layers of ground planes 2-6. The signal via 2-5 that vertically penetrates the base material 2-12 corresponds to the center conductor of the pseudo coaxial line 2-15.

[0034] Here, the pseudo coaxial line means a structure similar to a coaxial line, which includes a ground plane 2-6 having an insulator (base material 2-12) on the outer periphery of the signal via 2-5 and a circular shape at the boundary with the insulator, and a ground via 2-3-3 that electrically connects each ground plane 2-6.

[0035] The coplanar strip line 2-14 extends in the horizontal direction, and the pseudo coaxial line 2-15 extends in the vertical direction. Therefore, when electrically and physically connecting the end of the coplanar strip line 2-14 and the end of the pseudo coaxial line 2-15, a connection portion 2-13 that bends the extending direction of the line is required at the location where the signal line 2-1 and the signal via 2-5 are connected.

[0036] At the connection portion 2-13, the direction of the line will bend at a right angle. In the base material 2-12 on the inner peripheral side of the connection portion 2-13, a space 2-8 where the base material 2-12 is removed is formed. Also, in the base material 2-12 on the outer peripheral side of the connection portion 2-13, a space 2-9 where the base material 2-12 is removed is formed. The interiors of the spaces 2-8 and 2-9 are filled with air or an inert gas such as N2. Also, as will be described later, the interiors of the spaces 2-8 and 2-9 may be filled with an insulator or a semi-insulating semiconductor.

[0037] The total volume of the inner peripheral side space 2-8 is formed to be smaller than the total volume of the outer peripheral side space 2-9. The diameter of the signal via 2-5 forming the pseudo coaxial line 2-15 is sufficiently larger than the conductor thickness of the signal line 2-1 forming the coplanar strip line 2-14. Therefore, in this embodiment, it is possible to suppress the impedance reduction due to the increase in electrical capacitance occurring at the connection portion 2-13.

[0038] Furthermore, the inner peripheral side space 2-8 of the connection portion 2-13 functions as an inductance adjustment portion of the signal line 2-1 of the coplanar strip line 2-14, and functions as a wideband adjustment portion of the reflection frequency of the high-frequency signal due to the LC resonance occurring at the connection portion 2-13.

[0039] Therefore, in this embodiment, it is possible to suppress the impedance reduction due to the increase in the capacitance expressed at the connection portion 2-13, and at the same time, it is possible to realize the broadbanding of the reflection frequency of the high-frequency signal due to the LC resonance occurring at the connection portion 2-13, and to achieve the characteristic impedance matching over the entire coplanar strip line 2-14, connection portion 2-13, and quasi-coaxial line 2-15. As a result, in the high-frequency line connection structure 2, it is possible to transmit the high-frequency signal without loss between the signal line end 2-4a of the coplanar strip line 2-14 and the signal line end 2-4b of the quasi-coaxial line 2-15.

[0040] On the other hand, as a method of characteristic impedance matching that does not depend on this embodiment, a method of physically processing the structure of the vertex of the connection portion has been proposed and is known, and is widely used in various applications. FIG. 8 shows a cross-sectional view of a conventional high-frequency line connection structure disclosed in Non-Patent Document 2. FIG. 9 is a cross-sectional view of the high-frequency line connection structure of FIG. 8 cut along a plane parallel to the layer in which the signal line 2-1 is formed (the layer at the position of the D-D' line in FIG. 8). FIG. 10 is a bottom view of the high-frequency line connection structure of FIG. 8. FIG. 8 shows a cross-section of the high-frequency line connection structure cut at the position of the E-E' line in FIG. 9.

[0041] As shown in FIG. 8, according to Non-Patent Document 2, the signal via 2-5 and signal pad 2-4-1 of the quasi-coaxial line are removed by machining from the outside to suppress the expression of capacitance and inductance. The presence of the space 2-10 due to the backdrill mark and the partially remaining stub region 2-11 is a feature of the technology disclosed in Non-Patent Document 2.

[0042] Even if the machining accuracy disclosed in Non-Patent Document 2 is improved, it is not easy to make the stub region 2-11 zero. Due to the existence of the electrical length in the stub region 2-11, signal reflection at a frequency corresponding to 1 / 4 of the in-tube signal wavelength cannot be avoided. For this reason, in optical communication applications using baseband frequencies from near DC (Direct Current) to over 100 GHz, which are increasing in recent years, cases where the technology disclosed in Non-Patent Document 2 is difficult to apply are emerging.

[0043] On the other hand, according to this embodiment, by providing spaces 2-8 and 2-9 in the base materials 2-12 on the outer peripheral side and the inner peripheral side of the connection part 2-13, a very simple and easily implementable structure enables characteristic impedance matching to be obtained across all of the coplanar strip line 2-14 and the quasi-coaxial line 2-15, and high-frequency signals can be transmitted without loss.

[0044] [Third Embodiment] Next, the high-frequency line connection structure 3 according to the third embodiment of the present invention will be described with reference to FIGS. 11 to 13. FIG. 11 is a cross-sectional view of the high-frequency line connection structure 3, FIG. 12 is a cross-sectional view of the high-frequency line connection structure 3 cut along a plane parallel to the layer in which the signal line 3-1 is formed (the layer at the position of the D-D' line in FIG. 11), and FIG. 13 is a bottom view of the high-frequency line connection structure 3. FIG. 11 shows a cross-section of the high-frequency line connection structure 3 cut at the position of the E-E' line in FIG. 12.

[0045] The high-frequency line connection structure 3 includes two high-frequency signal lines, specifically, a coplanar strip line 3-14 (second high-frequency line) and a quasi-coaxial line 3-15 (second high-frequency line).

[0046] The coplanar strip line 3-14 includes a signal line 3-1 made of a conductor formed in a base material 3-12 made of an insulator, ground planes 3-2-1 made of conductors formed in the base materials 3-12 on the left and right of the signal line 3-1, ground planes 3-2-4 and 3-2-2 made of multiple layers of conductors formed in the base materials 3-12 above and below the signal line 3-1, a ground via 3-3-1 made of a conductor formed in the base material 3-12 to connect the multiple layers of ground planes 3-2-1 and 3-2-4, and a ground via 3-3-2 made of a conductor formed in the base material 3-12 to connect the multiple layers of ground planes 3-2-1 and 3-2-2. Examples of the material of the base material 3-12 include alumina ceramics.

[0047] The pseudo coaxial line 3-15 includes a signal pad 3-4-1 composed of a conductor formed in the base material 3-12 so as to be connected to the signal line 3-1 and a plurality of layers of conductors below it, a signal via 3-5 composed of a conductor formed in the base material 3-12 so as to connect the plurality of layers of signal pads 3-4-1, a ground plane 3-6 composed of a plurality of layers of conductors formed in the base material 3-12 around the signal pad 3-4-1 in the same layer as the plurality of ground planes 3-2-1, 3-2-2, an anti-pad region 3-7 which is a region where the ground plane 3-6 is selectively removed and filled by the base material 3-12, and a ground via 3-3-3 composed of a conductor formed in the base material 3-12 so as to connect the plurality of layers of ground planes 3-6. The signal via 3-5 vertically penetrating the base material 3-12 corresponds to the center conductor of the pseudo coaxial line 3-15.

[0048] The coplanar strip line 3-14 extends in the horizontal direction, and the pseudo coaxial line 3-15 extends in the vertical direction. Therefore, when electrically and physically connecting the end of the coplanar strip line 3-14 and the end of the pseudo coaxial line 3-15, a connection portion 3-13 for bending the extending direction of the line is required at the location where the signal line 3-1 and the signal via 3-5 are connected.

[0049] In the above-described second embodiment, the upper part of the region from the coplanar strip line 3-14 to the connection portion 2-13 was filled with the base material 2-12 and had no space. In contrast, in this embodiment, a space 3-8 where the base material 3-12 is removed is formed in the base material 3-12 on the inner peripheral side of the connection portion 3-13. Also, a space 3-9 where the base material 3-12 is removed is formed in the base material 3-12 on the outer peripheral side of the connection portion 3-13.

[0050] Furthermore, in this embodiment, a space 3-10 is formed in which the base material 3-12 above the signal pad 3-4-1 connected to the signal line 3-1 is removed. A part of the signal pad 3-4-1 is exposed in the space 3-10. The interiors of the spaces 3-8 to 3-10 are filled with air or an inert gas such as N2. Also, as will be described later, the interiors of the spaces 3-8 to 3-10 may be filled with an insulator or a semi-insulating semiconductor.

[0051] The total volume of the inner peripheral space 3-8 is formed to be smaller than the total volume of the outer peripheral spaces 3-9 and 3-10. In the examples of FIGS. 11 and 12, the spaces 3-9 and 3-10 are formed to communicate with each other, but they may not communicate with each other.

[0052] In this embodiment, by removing not only the base material 3-12 around the signal via 3-5 but also the base material 3-12 above the signal pad 3-4-1 connected to the signal line 3-1, it is possible to further suppress the impedance reduction due to the increase in the electrical capacitance expressed at the connection portion 3-13. At the same time, it is possible to realize the broadening of the reflection frequency band of the high-frequency signal due to the LC resonance occurring at the connection portion 3-13, and to achieve the characteristic impedance matching over the entire coplanar strip line 3-14, connection portion 3-13, and quasi-coaxial line 3-15. As a result, in the high-frequency line connection structure 3, it is possible to transmit a high-frequency signal without loss between the signal line end 3-4a of the coplanar strip line 3-14 and the signal line end 3-4b of the quasi-coaxial line 3-15.

[0053] [Fourth Embodiment] Next, the high-frequency line connection structure 4 according to the fourth embodiment of the present invention will be described with reference to FIGS. 14 to 16. FIG. 14 is a cross-sectional view of the high-frequency line connection structure 4, FIG. 15 is a cross-sectional view of the high-frequency line connection structure 4 cut along a plane parallel to the layer in which the signal line 4-1 is formed (the layer at the position of the D-D' line in FIG. 14), and FIG. 16 is a bottom view of the high-frequency line connection structure 4. FIG. 14 shows a cross-section of the high-frequency line connection structure 4 cut at the position of the E-E' line in FIG. 15.

[0054] The high-frequency line connection structure 4 includes two high-frequency signal lines, specifically, a coplanar strip line 4-14 (the first high-frequency line) and a pseudo coaxial line 4-15 (the second high-frequency line).

[0055] The coplanar strip line 4-14 is composed of a signal line 4-1 made of a conductor formed in a base material 4-12 made of an insulator, a ground plane 4-2-1 made of a conductor formed in the left and right base materials 4-12 of the signal line 4-1, ground planes 4-2-4 and 4-2-2 made of a plurality of layers of conductors formed in the upper and lower base materials 4-12 of the signal line 4-1, a ground via 4-3-1 made of a conductor formed in the base material 4-12 to connect the plurality of layers of ground planes 4-2-1 and 4-2-4, and a ground via 4-3-2 made of a conductor formed in the base material 4-12 to connect the plurality of layers of ground planes 4-2-1 and 4-2-2. As the material of the base material 4-12, for example, there is alumina ceramics.

[0056] The pseudo coaxial line 4-15 is composed of a signal pad 4-4-1 made of a conductor formed in the base material 4-12 to connect to the signal line 4-1 and a plurality of layers of conductors thereunder, a signal via 4-5 made of a conductor formed in the base material 4-12 to connect the plurality of layers of signal pads 4-4-1, a ground plane 4-6 made of a plurality of layers of conductors formed in the base material 4-12 around the signal pad 4-4-1 in the same layer as the ground planes 4-2-1 and 4-2-2, an anti-pad region 4-7 which is a region where the ground plane 4-6 is selectively removed and filled by the base material 4-12, and a ground via 4-3-3 made of a conductor formed in the base material 4-12 to connect the plurality of layers of ground planes 4-6. The signal via 4-5 that vertically penetrates the base material 4-12 corresponds to the center conductor of the pseudo coaxial line 4-15.

[0057] The coplanar strip line 4-14 extends horizontally, and the pseudo coaxial line 4-15 extends vertically. Therefore, when electrically and physically connecting the end of the coplanar strip line 4-14 and the end of the pseudo coaxial line 4-15, a connection portion 4-13 that bends the extending direction of the line is required at the location where the signal line 4-1 and the signal via 4-5 are connected.

[0058] In the above-described second embodiment, the upper part of the region from the coplanar strip line 4-14 to the connection portion 2-13 was filled with the base material 2-12, and there was no space. In contrast, in this embodiment, a space 4-8 in which the base material 4-12 is removed is formed in the base material 4-12 on the inner peripheral side of the connection portion 4-13. Also, a space 4-9 in which the base material 4-12 is removed is formed in the base material 4-12 on the outer peripheral side of the connection portion 4-13.

[0059] Furthermore, in this embodiment, a space 4-10 is formed in which the base material 4-12 above the signal pad 4-4-1 connected to the signal line 4-1 and the base material 4-12 above the signal line 4-1 are removed. The signal line 4-1 and the signal pad 4-4-1 on the signal via 4-5 side are exposed in the space 4-10. The interiors of the spaces 4-8 to 4-10 are filled with air or an inert gas such as N2. Also, an insulator or a semi-insulating semiconductor may be filled in the interiors of the spaces 4-8 to 4-10 as described later.

[0060] The total volume of the space 4-8 on the inner peripheral side is formed to be smaller than the total volume of the spaces 4-9 and 4-10 on the outer peripheral side. In the examples of FIGS. 14 and 15, the space 4-9 and the space 4-10 are formed to communicate, but they may also be in a non-communicating form.

[0061] Furthermore, in this embodiment, a tapered portion 4-1-2 whose width gradually increases as it approaches the signal via 4-5 is provided in the middle of the signal line 4-1, so that the signal line 4-1 on the side closer to the signal via 4-5 is wider than the signal line 4-1 on the side farther from the signal via 4-5. The reason for widening the width of the signal line 4-1 on the side closer to the signal via 4-5 is for characteristic impedance matching.

[0062] With the above configuration, in this embodiment, it is possible to further suppress the impedance reduction due to the increase in capacitance expressed at the connection portion 4-13, and at the same time, it is possible to realize the broadband of the reflection frequency of the high-frequency signal due to the LC resonance occurring at the connection portion 4-13.

[0063] Note that in the electromagnetic field distribution that can propagate in the quasi-coaxial line 4-15, it is not always the case that only the fundamental mode propagates through the signal via 4-5. There is also a waveguide propagation mode when the ground plane 4-6 and the ground via 4-3-3 constituting the quasi-coaxial line 4-15 are regarded as metal walls.

[0064] Since the signal pad 4-4-1 and the ground plane 4-6 are spatially far apart, the signal line 4-1 in the anti-pad region 4-7, which is the extension of the coplanar strip line 4-14, easily electromagnetically couples with the surrounding ground plane in the vicinity, and this coupling can cause an unwanted waveguide propagation mode. Suppressing this electromagnetic coupling is also possible in this embodiment. That is, in this embodiment, it is possible to suppress the excitation of the higher-order waveguide mode in the quasi-coaxial line 4-15 and suppress the leakage of the electromagnetic field to the outer peripheral side by forming the space 4-10.

[0065] Therefore, in this embodiment, it is possible to achieve the characteristic impedance matching over the entire coplanar strip line 4-14, the connection portion 4-13, and the quasi-coaxial line 4-15 without generating the waveguide propagation mode in the quasi-coaxial line 4-15 which is originally unnecessary. As a result, in the high-frequency line connection structure 4, it is possible to transmit the high-frequency signal without loss between the signal line end 4-4a of the coplanar strip line 4-14 and the signal line end 4-4b of the quasi-coaxial line 4-15.

[0066] Note that the present invention is not limited to the first to fourth embodiments described above, and it is obvious that many modifications and combinations can be implemented by those with ordinary knowledge in the art within the technical idea of the present invention.

[0067] For example, the connecting portions 1-13, 2-13, 3-13, 4-13 that bend the extending direction of the circuit may be in a stepped shape instead of a shape where the extending direction bends at a right angle, or may be in a shape having one or more non-right-angled vertices.

[0068] Also, for the pseudo coaxial circuits 2-15, 3-15, 4-15, the signal pads 2-4-1, 3-4-1, 4-4-1, the signal vias 2-5, 3-5, 4-5, and the anti-pad regions 2-7, 3-7, 4-7 are circular in plan view, and the centers of the signal pads 2-4-1, 3-4-1, 4-4-1, the centers of the signal vias 2-5, 3-5, 4-5, and the centers of the anti-pad regions 2-7, 3-7, 4-7 coincide. However, it goes without saying that there is no need to be bound by these structures.

[0069] For example, it is not necessary to make the centers of the signal pads 2-4-1, 3-4-1, 4-4-1 and the centers of the signal vias 2-5, 3-5, 4-5 coincide with the centers of the anti-pad regions 2-7, 3-7, 4-7, and they can be changed to desired positions within the anti-pad regions 2-7, 3-7, 4-7 from the viewpoint of characteristic impedance matching.

[0070] Also, the anti-pad regions 2-7, 3-7, 4-7 do not have to be a perfect circle in plan view. For example, the anti-pad regions 2-7, 3-7, 4-7 may be in an elliptical shape in plan view, or may be in an angular rounded rectangular shape in plan view.

[0071] Also, in the first to fourth embodiments, the materials of the base materials 1-2, 2-12, 3-12, 4-12 are alumina ceramics, but it goes without saying that there is no need to be limited to this. For example, ceramics materials such as aluminum nitride and zirconia can also be used, and inorganic materials such as quartz glass and low melting point glass may be used. Also, as the materials of the base materials 1-2, 2-12, 3-12, 4-12, organic materials such as resin and Teflon (registered trademark) may be used. Furthermore, semi-insulating semiconductors can also be used, for example, high-resistance Si, semi-insulating GaAs, and InP may be used.

[0072] In addition, in the first to fourth embodiments, spaces 1-5, 1-6, 2-8, 2-9, 3-8 to 3-10, and 4-8 to 4-10 are formed on both the inner peripheral side and the outer peripheral side of the connection parts 1-13, 2-13, 3-13, and 4-13. However, spaces may be formed only on the outer peripheral side.

[0073] In addition, when spaces are formed on both the inner peripheral side and the outer peripheral side of the connection parts 1-13, 2-13, 3-13, and 4-13, if the number of spaces on the inner peripheral side is M (M is an integer of 1 or more) and the number of spaces on the outer peripheral side is N (N is an integer of 1 or more), the relationship M ≤ N may be satisfied. Also, as described above, when spaces are formed on both the inner peripheral side and the outer peripheral side of the connection parts 1-13, 2-13, 3-13, and 4-13, the total volume of the spaces on the inner peripheral side may be made smaller than the total volume of the spaces on the outer peripheral side.

[0074] In addition, in the first to fourth embodiments, it is assumed that the interiors of the spaces 1-5, 1-6, 2-8, 2-9, 3-8 to 3-10, and 4-8 to 4-10 are filled with air or an inert gas such as N2. As another configuration example, the interiors of the spaces 1-5, 1-6, 2-8, 2-9, 3-8 to 3-10, and 4-8 to 4-10 may be filled with a material having a relative permittivity lower than that of the base materials 1-2, 2-12, 3-12, and 4-12. Such materials include insulators or semi-insulating semiconductors.

[0075] In addition, when spaces are formed on both the inner peripheral side and the outer peripheral side of the connection parts 1-13, 2-13, 3-13, and 4-13, it is desirable that the relative permittivity of the insulator or semi-insulating semiconductor filled in the space on the outer peripheral side be smaller than the relative permittivity of the insulator or semi-insulating semiconductor filled in the space on the inner peripheral side.

[0076] In addition, in the third embodiment, the spaces 3-9 and 3-10 on the outer peripheral side of the connection part 3-13 are formed to communicate with each other. However, the spaces 3-9 and 3-10 may be formed separately. Similarly, in the fourth embodiment, the spaces 4-9 and 4-10 on the outer peripheral side of the connection part 4-13 are formed to communicate with each other. However, the spaces 4-9 and 4-10 may be formed separately.

[0077] In addition, in the first to fourth embodiments, the shapes of the spaces 1-5, 1-6, 2-8, 2-9, 3-8 to 3-10, and 4-8 to 4-10 were described by taking the shapes of arcs and polyhedrons as examples, but these shapes are not essential. Needless to say, shapes reflecting various manufacturing processes can be applied as the shapes of the spaces 1-5, 1-6, 2-8, 2-9, 3-8 to 3-10, and 4-8 to 4-10.

[0078] In addition, in the first to fourth embodiments, the spaces in the base materials 1-2, 2-12, 3-12, and 4-12 may be formed around at least one of the signal lines of the first high-frequency line and the second high-frequency line so as to be in contact with the ground plane (formed so that the ground plane is exposed in the space). Further, the space may be formed at a position adjacent to the ground plane via the base materials 1-2, 2-12, 3-12, and 4-12. These spaces function as capacitive adjustment units.

[0079] In addition, in the first to fourth embodiments, the spaces in the base materials 1-2, 2-12, 3-12, and 4-12 may be formed around at least one of the signal lines of the first high-frequency line and the second high-frequency line so as to be in contact with the signal line (formed so that the signal line is exposed in the space). Further, the space may be formed at a position adjacent to the signal line via the base material. These spaces function as inductive adjustment units.

Industrial Applicability

[0080] The present invention can be applied to a technique for connecting high-frequency lines having different extending directions.

Explanation of Signs

[0081] 1, 2, 3, 4… High-frequency circuit connection structure, 1-1a, 1-1b, 2-1, 3-1, 4-1… Signal lines, 1-13, 2-13, 3-13, 4-13… Connection parts, 1-2, 2-12, 3-12, 4-12… Substrates, 1-3, 2-2-1, 2-2-2, 2-2-4, 2-6, 3-2-1, 3-2-2, 3-2-4, 3-6, 4-2-1, 4-2-2, 4-2-4, 4-6… Ground planes, 1-5, 1-6, 2-8, 2-9, 3-8~3-10, 4-8~4-10… Spaces, 1-14, 1-15… Microstrip lines, 2-4-1, 3-4-1, 4-4-1… Signal pads, 2-5, 3-5, 4-5… Signal vias, 2-7, 3-7, 4-7… Anti-pad regions, 2-3-1, 2-3-2, 2-3-3, 3-3-1, 3-3-2, 3-3-3, 4-3-1, 4-3-2, 4-3-3… Ground vias, 2-14, 3-14, 4-14… Coplanar strip lines, 2-15, 3-15, 4-15… Quasi-coaxial lines, 4-1-2… Tapered parts.

Claims

1. A first high-frequency line formed on the surface of a base material made of an insulator or a semi-insulating semiconductor or in the base material, and a second high-frequency line formed on the surface of the base material or in the base material, the second high-frequency line having a different extending direction from that of the first high-frequency line, and a connection portion that bends the extending direction of the line at a location where the first high-frequency line and the second high-frequency line are connected, wherein spaces from which the base material is removed are formed on both the inner peripheral side and the outer peripheral side of the connection portion, the total volume of the space on the inner peripheral side of the connection portion is smaller than the total volume of the space on the outer peripheral side, and when the number of the spaces on the inner peripheral side is M (M is an integer of 1 or more) and the number of the spaces on the outer peripheral side is N (N is an integer of 1 or more), a high-frequency line connection structure characterized by satisfying the relationship M≦N.

2. A first high-frequency line formed on the surface of a base material made of an insulator or a semi-insulating semiconductor or in the base material, and a second high-frequency line formed on the surface of the base material or in the base material, the second high-frequency line having a different extending direction from that of the first high-frequency line, and a connection portion that bends the extending direction of the line at a location where the first high-frequency line and the second high-frequency line are connected, wherein spaces from which the base material is removed are formed only on the outer peripheral side of the connection portion or on both the inner peripheral side and the outer peripheral side of the connection portion, when the spaces are formed on both the inner peripheral side and the outer peripheral side of the connection portion, the total volume of the space on the inner peripheral side is smaller than the total volume of the space on the outer peripheral side, the first high-frequency line and the second high-frequency line are both formed in the base material having a multilayer structure, the first high-frequency line is formed in a specific layer in the base material, and the second high-frequency line is formed so as to penetrate a plurality of layers in the base material, a high-frequency line connection structure characterized thereby.

3. In the high-frequency line connection structure according to Claim 2, the space is formed so as to be in contact with a ground plane formed in the base material around at least one of the signal lines of the first high-frequency line and the second high-frequency line, or is formed at a position adjacent to the ground plane through the base material, and functions as a capacitive adjustment portion, a high-frequency line connection structure characterized thereby.

4. A first high-frequency line formed on the surface of a base material made of an insulator or a semi-insulating semiconductor or in the base material, and a second high-frequency line formed on the surface of the base material or in the base material, the second high-frequency line having a different extending direction from that of the first high-frequency line, a connection portion that bends the extending direction of the line at a location where the first high-frequency line and the second high-frequency line are connected; a space where the base material is removed is formed only on the outer peripheral side of the connection portion, or on both the inner peripheral side and the outer peripheral side of the connection portion; when the spaces are formed on both the inner peripheral side and the outer peripheral side of the connection portion, the total volume of the space on the inner peripheral side is smaller than the total volume of the space on the outer peripheral side; the space is formed around at least one of the signal lines of the first high-frequency line and the second high-frequency line so as to be in contact with the signal line, or is formed at a position adjacent to the signal line via the base material, and functions as an inductive adjustment unit. A high-frequency line connection structure characterized by this.

5. In the high-frequency line connection structure according to any one of Claims 1 to 4, the first high-frequency line and the second high-frequency line are any one of a microstrip line, a coplanar line, and a strip line. A high-frequency line connection structure characterized by this.

6. A first high-frequency line formed on the surface of a base material made of an insulator or a semi-insulating semiconductor or in the base material, and a second high-frequency line formed on the surface of the base material or in the base material, the extending direction of which is different from that of the first high-frequency line, and a connection portion that bends the extending direction of the line at a location where the first high-frequency line and the second high-frequency line are connected; a space where the base material is removed is formed only on the outer peripheral side of the connection portion, or on both the inner peripheral side and the outer peripheral side of the connection portion; when the spaces are formed on both the inner peripheral side and the outer peripheral side of the connection portion, the total volume of the space on the inner peripheral side is smaller than the total volume of the space on the outer peripheral side; the first high-frequency line is a strip line; the second high-frequency line is a pseudo coaxial line composed of a signal via formed so as to penetrate a plurality of layers in the base material, a ground plane formed so as to surround the signal via, and the base material filling the space between the signal via and the ground plane. A high-frequency line connection structure characterized by this.

7. In the high-frequency line connection structure according to Claim 6, When the space is formed on both the inner peripheral side and the outer peripheral side of the connection portion, the space on the inner peripheral side of the connection portion is formed so as to be in contact with the ground plane formed in the base material around the signal lines of both the first high-frequency line and the second high-frequency line, or is formed at a position adjacent to the ground plane through the base material, The space on the outer peripheral side of the connection portion is formed so as to be in contact with the signal line of the first high-frequency line and is formed at a position adjacent to the signal line of the second high-frequency line through the base material. A high-frequency line connection structure characterized by this.

8. A first high-frequency line formed on the surface of a base material made of an insulator or a semi-insulating semiconductor or in the base material, and A second high-frequency line formed on the surface of the base material or in the base material, the second high-frequency line having a different extending direction from that of the first high-frequency line, and A connection portion that bends the extending direction of the line at the location where the first high-frequency line and the second high-frequency line are connected, Spaces from which the base material is removed are formed on both the inner peripheral side and the outer peripheral side of the connection portion, The total volume of the space on the inner peripheral side of the connection portion is smaller than the total volume of the space on the outer peripheral side, and an insulator having a relative permittivity smaller than that of the base material or a semi-insulating semiconductor having a relative permittivity smaller than that of the base material is filled inside the spaces on the inner peripheral side and the outer peripheral side of the connection portion, A high-frequency line connection structure characterized in that the relative permittivity of the insulator or semi-insulating semiconductor filled in the space on the outer peripheral side is smaller than the relative permittivity of the insulator or semi-insulating semiconductor filled in the space on the inner peripheral side.

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