Intersection structure of transmission line and butler matrix having the same

Abstract

To provide an intersection structure of a transmission line that enables the formation of intersection while maintaining good isolation and suppressing the overall thickness of the multilayer substrate, and a butler matrix having the same.SOLUTION: In an intersection 23 of an intersection structure of a transmission line, where a first strip conductor and a second strip conductor cross, four square waveguides 29 are formed in which a third dielectric layer 16 fills the space formed by a second grounding conductor portion 15, a third grounding conductor portion 17, and a through-hole portion 25, and the cutoff frequency of the square waveguide 29 is higher than the maximum frequency of the operating frequency band.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a transmission line intersection structure and a Butler matrix including the same, and more particularly to a transmission line intersection structure for the frequency band of a 5G wireless communication system and a Butler matrix including the same. [Background technology]

[0002] The wireless communication terminal (User Equipment: UE) used in 5G wireless communication systems is equipped with multiple antennas and uses a communication technology called MIMO (Multiple Input Multiple Output), which uses these multiple antennas simultaneously. Furthermore, the UE also uses a technology that increases maximum transmission capacity by simultaneously transmitting and receiving signals at multiple frequencies. When testing such UE, it is necessary to input arbitrary signals from the measurement system to the multiple antennas, which requires reconnecting the connection cables to each antenna every time a test is performed. To simplify testing by eliminating this connection work, a method using a distribution circuit with a Butler matrix is ​​known.

[0003] There are several methods for realizing a Butler matrix. Patent Document 1 discloses a structure in which two 4x4 Butler matrices are formed on either side of a ground layer, and a hybrid circuit of the 4x4 Butler matrix on one layer is connected to a hybrid circuit of the 4x4 Butler matrix on the other layer via a through hole.

[0004] Non-Patent Document 1 discloses a hybrid circuit using strip lines. The hybrid circuit disclosed in Non-Patent Document 1 is a 3 dB quadrature hybrid coupler that splits one input signal into two output signals with a phase difference of 90 degrees from each other. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-92377 [Non-patent literature]

[0006] [Non-Patent Document 1] F. FARZANEH, et al., "Broadside Coupler Channels 1 To 10 GHz", Microwaves&RF magazine, pp.68-77, Jan. 2012 Summary of the Invention [Problem to be solved by the invention]

[0007] To realize a Butler matrix, there is a problem of how to fabricate the crossover, as shown in the problem in Patent Document 1. In Patent Document 1, this problem is solved by making the board multilayered and connecting the layers with through holes.

[0008] However, Patent Document 1 does not disclose a method for fabricating a hybrid circuit, and therefore, when adopting a hybrid circuit configuration such as that of Non-Patent Document 1, it is not clear what layer configuration should be used to construct the crossover of the Butler matrix.

[0009] For example, a common method for fabricating a crossover using two strip conductors on different layers, as disclosed in Non-Patent Document 1, is the configuration shown in Figure 10. The L3 and L4 layers are strip conductors of the strip line, and the L2 and L5 layers are ground layers of the strip line.

[0010] The strip conductor of the L3 layer is connected to the strip conductor of the microstrip line of the L1 layer through a through hole at the point where it intersects with the strip conductor of the L4 layer, and the strip conductor of the L1 layer is connected to the L3 layer through a through hole as before at the point where it passes through the strip conductor of the L4 layer. In this way, a crossover can be created while maintaining isolation between the strip conductor of the L3 layer and the strip conductor of the L4 layer.

[0011] Also, although not shown in the cross section of Figure 10, the strip conductor of the L4 layer is connected to the strip conductor of the microstrip line of the L6 layer through a through hole at the point where it intersects with the strip conductor of the L3 layer, and the strip conductor of the L6 layer is connected to the L4 layer through a through hole at the point where it passes through the strip conductor of the L3 layer, as before.

[0012] However, the configuration shown in Fig. 10 requires additional layers just to form the crossover bridge structure above and below the strip conductors of the L3 and L4 layers, which increases the thickness of the entire multilayer board, resulting in increased costs. Furthermore, such a bridge structure is undesirable because it degrades the high-frequency characteristics of the circuit.

[0013] The present invention has been made to solve the above-mentioned conventional problems, and aims to provide a transmission line crossing structure that can reduce the overall thickness of a multilayer board and form a crossing section while maintaining good isolation, and a Butler matrix equipped with the same. [Means for solving the problem]

[0014] In order to solve the above problems, the crossing structure of the transmission line according to the present invention includes a first ground conductor (11), a first strip conductor (13) provided on a layer (L1-2, L2-1) below at least a part of the first ground conductor via a first dielectric layer (12), a second ground conductor (15) provided below the first strip conductor via a second dielectric layer (14), a third ground conductor (17) provided below the second ground conductor via a third dielectric layer (16), a second strip conductor (19) provided on a layer (L1-5, L2-4) below the third ground conductor via a fourth dielectric layer (18), and a fourth ground conductor (19) at least a part of which is provided below the second strip conductor via a fifth dielectric layer (20). The crossing structure of transmission lines (1, 2) includes a ground conductor (21) and a conductive connection portion (25) that conductively connects the first ground conductor portion, the second ground conductor portion, the third ground conductor portion, and the fourth ground conductor portion by penetrating at least the third dielectric layer, and transmits signals in a predetermined operating frequency band using the first strip conductor and the second strip conductor, and at an intersection portion (23) where the first strip conductor and the second strip conductor intersect, four waveguides (29) are formed by filling the third dielectric layer in spaces formed by the second ground conductor portion, the third ground conductor portion, and the conductive connection portion, and the cutoff frequency of each of the waveguides is higher than the maximum frequency of the operating frequency band.

[0015] That is, in the crossing structure of transmission lines according to the present invention, the first strip conductor is provided on only one layer, and the second strip conductor is provided on only another layer. Also, in the crossing structure of transmission lines according to the present invention, four waveguides are formed at the crossing portion.

[0016] With these configurations, the crossing structure of transmission lines according to the present invention can reduce the overall thickness of the multilayer board and can configure the crossing portion while maintaining good isolation.

[0017] Furthermore, the intersection structure of the transmission line according to the present invention may be configured such that the width of the first strip conductor and the second strip conductor at the intersection is narrower than the width of the first strip conductor and the second strip conductor at other locations outside the intersection, the thickness of the first dielectric layer facing the first strip conductor at the intersection is thinner than the thickness of the first dielectric layer at other locations outside the intersection that face the first strip conductor, and the thickness of the fifth dielectric layer at the intersection that faces the second strip conductor is thinner than the thickness of the fifth dielectric layer at other locations outside the intersection that face the second strip conductor.

[0018] With this configuration, the crossing structure of the transmission line according to the present invention has a structure in which the thicknesses of the first dielectric layer and the fifth dielectric layer are changed according to the widths of the first strip conductor and the second strip conductor, and it is possible to realize optimal impedance throughout the entire transmission line, including the crossing portion.

[0019] Furthermore, the crossing structure of transmission lines according to the present invention may be configured such that the first dielectric layer and the fifth dielectric layer are air layers.

[0020] With this configuration, the crossing structure of the transmission lines according to the present invention can reduce the insertion loss of the transmission lines by using an air layer with a low dielectric constant and dielectric loss tangent.

[0021] Furthermore, the transmission line crossing structure according to the present invention may further include a metal housing (120) that houses a multilayer substrate (40) consisting of the first strip conductor, the second dielectric layer, the second ground conductor portion, the third dielectric layer, the third ground conductor portion, the fourth dielectric layer, and the second strip conductor, and the first ground conductor portion and the fourth ground conductor portion may be configured to be part of the metal housing.

[0022] With this configuration, the crossing structure of transmission lines according to the present invention can easily provide air layers between the first dielectric layer and the fifth dielectric layer using a metal housing.

[0023] Furthermore, the crossing structure of transmission lines according to the present invention may be configured such that the operating frequency band is 600 MHz to 7.125 GHz.

[0024] A Butler matrix according to the present invention has any one of the above crossing structures of transmission lines. [Effects of the Invention]

[0025] The present invention provides a transmission line crossing structure that can reduce the overall thickness of a multilayer board and form a crossing section while maintaining good isolation, and a Butler matrix equipped with the same. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a diagram showing an example of a circuit configuration of a Butler matrix having a crossing structure of transmission lines according to a first embodiment of the present invention; [Figure 2] FIG. 1A is a cross-sectional view taken along line AA of the crossing structure of transmission lines according to the first embodiment of the present invention, and FIG. 1B is a plan view showing the positional relationship of metal patterns of the crossing structure of transmission lines according to the first embodiment of the present invention. [Figure 3] FIG. 1A is a cross-sectional view at the position of the BB line of the crossing structure of transmission lines according to the first embodiment of the present invention, and FIG. 1B is a plan view showing a rectangular waveguide in the crossing structure of transmission lines according to the first embodiment of the present invention. [Figure 4] FIG. 10 is a partial cross-sectional view showing the structure of a Butler matrix having a crossing structure of transmission lines according to a second embodiment of the present invention. [Figure 5] 10A to 10D are plan views showing the configuration of each layer of the crossing structure of transmission lines according to the second embodiment of the present invention, where (a) shows the configuration of the L2-1 layer, (b) shows the configuration of the L2-2 layer, (c) shows the configuration of the L2-3 layer, and (d) shows the configuration of the L2-4 layer. [Figure 6] 5(a) is a cross-sectional view of the crossing structure of the transmission lines at the position of the CC line in FIG. 5(a), and FIG. 5(b) is a cross-sectional view of the crossing structure of the transmission lines at the position of the DD line in FIG. 5(a). [Figure 7] FIG. 6 is a cross-sectional view of the crossing structure of the transmission lines at the position of the EE line in FIG. 5(a). [Figure 8] 10 is a graph showing a simulation result of the transmission coefficient of the crossing structure of the transmission lines according to the second embodiment of the present invention. [Figure 9] 10 is a graph showing a simulation result of isolation of a crossing structure of transmission lines according to the second embodiment of the present invention. [Figure 10] FIG. 1 is a cross-sectional view of a conventional transmission line crossing structure. DETAILED DESCRIPTION OF THE INVENTION

[0027] (First embodiment) First, an embodiment of a crossing structure of transmission lines and a Butler matrix including the same according to a first embodiment of the present invention will be described with reference to the drawings. Note that the dimensional ratios of the components in the drawings do not necessarily match the actual dimensional ratios.

[0028] 1 is a diagram showing an example of the circuit configuration of a Butler matrix 100 having a crossing structure of transmission lines according to this embodiment. The Butler matrix 100 shown in FIG. 1 is an 8×8 Butler matrix.

[0029] Butler matrix 100 has eight input terminals 1L-4L and 1R-4R for inputting signals and eight output terminals 111-118 for outputting signals. Butler matrix 100 also has hybrid circuits 201-212 and phase shifters 301-308.

[0030] The Butler matrix 100 distributes input signals from the input terminals 1L to 4L and 1R to 4R to the output terminals 111 to 118 at the same level and with a predetermined phase difference that differs for each input terminal.

[0031] The hybrid circuits 201 to 212 divide a signal input to an input terminal A1 or A2 into two output signals having a phase difference of 90 degrees, and output the two signals from output terminals B1 and B2.

[0032] Phase shifters 301 and 304 shift the phase of the signal passing through them by -67.5°. Phase shifters 302 and 303 shift the phase of the signal passing through them by -22.5°. Phase shifters 305 to 308 shift the phase of the signal passing through them by -45°.

[0033] Furthermore, transmission lines connect the input terminals 1L to 4L, 1R to 4R to the hybrid circuits 201 to 204, the hybrid circuits 201 to 204 to the subsequent hybrid circuits 205 to 208 or the phase shifters 301 to 304, the hybrid circuits 205 to 208 to the subsequent hybrid circuits 209 to 212 or the phase shifters 305 to 308, and the hybrid circuits 209 to 212 to the output terminals 111 to 118. The transmission lines are, for example, planar lines such as microstrip lines, coplanar lines, or strip lines (triplate lines).

[0034] It is also possible to cut out the bold framed portion of FIG. 1 from the Butler matrix 100 and use it as a 4×4 Butler matrix.

[0035] 1 are intersections 23 where two transmission lines intersect. In order to configure an 8x8 Butler matrix, multiple intersections 23 must be provided.

[0036] As shown in Fig. 2(a), the crossing structure of the transmission line 1 of this embodiment includes a multilayer substrate 30 consisting of six parallel layers, L1-1 to L1-6. Fig. 2(a) is a cross-sectional view taken along line AA in Fig. 2(b), and shows the cross-section of the transmission line 1 near a crossing point 23 where the first strip conductor 13 and the second strip conductor 19 cross each other.

[0037] The L1-1 layer is provided with a first ground conductor 11. The L1-2 layer is provided with a first strip conductor 13 below at least a portion of the first ground conductor 11 with a first dielectric layer 12 interposed therebetween.

[0038] On the L1-3 layer, a second ground conductor 15 is provided below the first strip conductor 13 with a second dielectric layer 14 in between. On the L1-4 layer, a third ground conductor 17 is provided below the second ground conductor 15 with a third dielectric layer 16 in between.

[0039] A second strip conductor 19 is provided on the L1-5 layer below the third ground conductor 17 with a fourth dielectric layer 18 interposed therebetween. A fourth ground conductor 21 is provided on the L1-6 layer. At least a portion of the fourth ground conductor 21 is provided below the second strip conductor 19 with a fifth dielectric layer 20 interposed therebetween.

[0040] That is, as shown in Figures 2(a) and (b), at the intersection 23, a second ground conductor portion 15 and a third ground conductor portion 17 are added between the first strip conductor 13 and the second strip conductor 19 provided on the L1-2 layer and the L1-5 layer.

[0041] At the intersection 23, a strip line consisting of the first ground conductor portion 11, the first strip conductor 13, and the fourth ground conductor portion 21 is connected to a strip line consisting of the first ground conductor portion 11, the first strip conductor 13, and the second ground conductor portion 15.

[0042] Similarly, at the intersection 23, a strip line consisting of the first ground conductor portion 11, the second strip conductor 19, and the fourth ground conductor portion 21 is connected to a strip line consisting of the third ground conductor portion 17, the second strip conductor 19, and the fourth ground conductor portion 21.

[0043] The first ground conductor portion 11, the second ground conductor portion 15, the third ground conductor portion 17, the fourth ground conductor portion 21, the first strip conductor 13, and the second strip conductor 19 are all metal patterns having a thickness of, for example, about 1 μm to 20 μm and made of a metal with a relatively low resistivity such as gold, copper, or aluminum.

[0044] The first ground conductor 11, the second ground conductor 15, the third ground conductor 17, and the fourth ground conductor 21 are conductively connected to a high frequency ground (RF ground).

[0045] The first to fifth dielectric layers 12, 14, 16, 18, and 20 are each formed of a substrate such as a semiconductor substrate made of GaAs, GaN, InP, or Si, an alumina ceramic substrate, a resin substrate, or a quartz glass substrate. The first to fifth dielectric layers 12, 14, 16, 18, and 20 may be formed by bonding together a plurality of resin substrates, or may be a single-layer resin substrate. For example, MEGTRON7 (registered trademark) manufactured by Panasonic Corporation can be suitably used as the first to fifth dielectric layers 12, 14, 16, 18, and 20.

[0046] When the first to fifth dielectric layers 12, 14, 16, 18, 20 are all made of a substrate material such as MEGTRON7, for example, the first dielectric layer 12 between the L1-1 and L1-2 layers may be made of a core material-prepreg, the second dielectric layer 14 between the L1-2 and L1-3 layers may be made of a core material, the third dielectric layer 16 between the L1-3 and L1-4 layers may be made of a prepreg (or a prepreg-core material-prepreg), the fourth dielectric layer 18 between the L1-4 and L1-5 layers may be made of a core material, and the fifth dielectric layer 20 between the L1-5 and L1-6 layers may be made of a prepreg-core material.

[0047] Since the first dielectric layer 12 and the fifth dielectric layer 20 are relatively thick, they may be constructed by laminating multiple layers of core materials and prepregs. The areas of the L1-2, L1-3, L1-4, and L1-5 layers where no metal patterns are provided are filled with prepregs.

[0048] The transmission line 1 of this embodiment transmits signals in a predetermined operating frequency band using the strip line configured as above. Here, the operating frequency band is, for example, 600 MHz to 7.125 GHz, which is the frequency band of FR1 (Frequency Range 1) used in 5G NR.

[0049] As already mentioned, the second dielectric layer 14 between the L1-2 layer and the L1-3 layer and the fourth dielectric layer 18 between the L1-4 layer and the L1-5 layer are made of core material, so unless a prepreg is used for the third dielectric layer 16 between the L1-3 layer and the L1-4 layer, the core material of the second dielectric layer 14 and the fourth dielectric layer 18 cannot be bonded together.

[0050] Therefore, a dielectric layer (here, the third dielectric layer 16) exists between the second ground conductor portion 15 of the L1-3 layer and the third ground conductor portion 17 of the L1-4 layer, and electromagnetic waves may be transmitted through this third dielectric layer 16, which may deteriorate the isolation.

[0051] In order to avoid this problem of deterioration of isolation, the crossing structure of the transmission line 1 of this embodiment has a conductive connection portion that conductively connects the first ground conductor portion 11, the second ground conductor portion 15, the third ground conductor portion 17, and the fourth ground conductor portion 21 by penetrating at least the third dielectric layer 16.

[0052] The conductive connection portion is actually made up of a plurality of through holes that penetrate all layers from the L1-1 layer to the L1-6 layer. Hereinafter, the conductive connection portion will also be referred to as a "penetrating through-hole portion 25."

[0053] Fig. 2(b) is a plan view showing the positional relationship between the penetrating through-hole portion 25 and the first strip conductor 13, second ground conductor portion 15, third ground conductor portion 17, and second strip conductor 19 provided on layers L1-2 to L1-5. However, in Fig. 2(b), the individual through-holes and dielectric layers are not shown.

[0054] That is, the penetrating through-hole portion 25 is arranged so as to overlap a portion of the second ground conductor portion 15 of the L1-3 layer and the third ground conductor portion 17 of the L1-4 layer, thereby conductively connecting the second ground conductor portion 15 and the third ground conductor portion 17 to the first ground conductor portion 11 and the fourth ground conductor portion 21.

[0055] FIG. 3(a) is a cross-sectional view taken along line BB in FIG. 3(b), showing the cross section of the transmission line 1 near the intersection 23 where the first strip conductor 13 and the second strip conductor 19 intersect.

[0056] 3(b) is a plan view showing the positional relationship between the penetrating through-hole portion 25, the third dielectric layer 16 provided between the L1-3 layer and the L1-4 layer, and the third ground conductor portion 17. In FIG. 3(b) as well, the individual through-holes constituting the penetrating through-hole portion 25 are not shown.

[0057] 3(a) and 3(b), at the intersection 23, four rectangular waveguides 29 are formed by filling the spaces formed by the second ground conductor 15, the third ground conductor 17, and the penetrating through-holes 25 with the third dielectric layer 16. The portions surrounded by ellipses in FIG. 3(a) indicate the cross sections of the rectangular waveguides 29.

[0058] With this structure, the four rectangular waveguides 29 become dielectric-filled waveguides, and if the length of the long side dimension a of these rectangular waveguides 29 is set to a length that gives a cutoff frequency higher than the maximum frequency of the frequency band being used, it becomes possible to block electromagnetic waves that pass through the third dielectric layer 16 between the L1-3 layer and the L1-4 layer, and the intersection 23 can be configured while maintaining good isolation. For example, if the long side dimension a of the rectangular waveguide 29 is set to 15 mm or less, the cutoff frequency can be set to 10 GHz or higher.

[0059] As described above, in the crossing structure of the transmission line 1 according to this embodiment, the first strip conductor 13 is provided only on the L1-2 layer, and the second strip conductor 19 is provided only on the L1-5 layer. Moreover, the crossing structure of the transmission line 1 according to this embodiment has four rectangular waveguides 29 at the crossing portion 23 where the first strip conductor 13 and the second strip conductor 19 cross, each of which is formed by filling the third dielectric layer 16 in spaces formed by the second ground conductor portion 15, the third ground conductor portion 17, and the penetrating through-hole portion 25.

[0060] The crossing structure of the transmission line 1 according to this embodiment configured in this manner can reduce the overall thickness of the multilayer substrate 30 and can configure the crossing portion 23 while maintaining good isolation.

[0061] (Second embodiment) Next, a transmission line crossing structure and a Butler matrix including the same according to a second embodiment of the present invention will be described with reference to the drawings. Note that the same components as those in the first embodiment are denoted by the same reference numerals and their description will be omitted as appropriate, and the following mainly describes the differences from the first embodiment. Note that the dimensional ratios of the components in each drawing do not necessarily match the actual dimensional ratios.

[0062] Fig. 4 is a partial cross-sectional view of a Butler matrix 110 having a crossing structure of transmission lines according to this embodiment. As shown in Fig. 4, the Butler matrix 110 includes a rectangular parallelepiped metal housing 120 and a multilayer substrate 40, with the multilayer substrate 40 housed inside the metal housing 120. The circuit configuration of the Butler matrix 110 is similar to that of the Butler matrix 100 according to the first embodiment.

[0063] Metal housing 120 is made up of lid portion 121 and main body portion 124. Fig. 4 shows a state in which lid portion 121 is removed from main body portion 124. Main body portion 124 has a bottom wall 125 and four side walls 126 that stand perpendicular to bottom wall 125. Of the four side walls 126, two side walls 126a and 126b extend in the width direction of metal housing 120 and face each other.

[0064] The lid 121 has an edge 122 that contacts the upper surfaces of the four side walls 126, and a protrusion 123 that fits into the main body 124 with a predetermined gap between it and two side walls 126a, 126b. The lid 121 is fixed to the metal housing 120 with the edge 122 in contact with the upper surfaces of the side walls 126 by screw holes and screws (not shown). For example, the edge 122 is attached to the upper surfaces of the side walls 126 with a conductive adhesive. Alternatively, conductive rubber, a gasket, or the like is placed between the edge 122 and the upper surfaces of the side walls 126 to ensure contact between the edge 122 and the side walls 126.

[0065] The entire metal housing 120 may be made of metal, or at least the bottom wall 125 of the main body 124 and the protrusion 123 of the lid 121 may be made of metal. The metal portion of the metal housing 120 is conductively connected to a high-frequency ground (RF ground). The metal constituting the entire metal housing 120 or the metal portion of the metal housing 120 may be, for example, aluminum, brass, or another metal that is plated with gold or silver.

[0066] A plurality of coaxial connectors 128, 129 are attached to the side walls 126a, 126b, and are conductively connected to the strip conductors of the multilayer substrate 40 fixed on the bottom wall 125 of the metal housing 120, forming input terminals 1L to 4L, 1R to 4R and output terminals 111 to 118.

[0067] The center pins of the coaxial connectors 128, 129 shown in FIG. 4 are conductively connected to the strip conductors of the multilayer substrate 40 by, for example, soldering, to form a coaxial-strip line transition section.

[0068] Coaxial connector 128 is adapted to be connected, for example, via a coaxial cable, to a signal source that outputs a high-frequency signal, while coaxial connector 129 is adapted to be connected, for example, via a coaxial cable, to an antenna of a UE such as a wireless communication terminal.

[0069] The multilayer substrate 40 is made up of four parallel layers, L2-1 to L2-4, as shown in Figures 5(a) to 5(d). Figure 6(a) is a cross-sectional view of the transmission line 2 near the intersection 23 at the position of the CC line in Figure 5(a). Figure 6(b) is a cross-sectional view of the transmission line 2 near the intersection 23 at the position of the DD line in Figure 5(a). Figure 7 is a cross-sectional view of the transmission line 2 near the intersection 23 at the position of the EE line in Figure 5(a).

[0070] The L2-1 layer is provided with a first strip conductor 13. The L2-2 layer is provided with a second ground conductor 15 below the first strip conductor 13 with a second dielectric layer 14 in between. The L2-3 layer is provided with a third ground conductor 17 below the second ground conductor 15 with a third dielectric layer 16 in between. The L2-4 layer is provided with a second strip conductor 19 below the third ground conductor 17 with a fourth dielectric layer 18 in between.

[0071] In this embodiment, the first ground conductor 11 is, for example, a protrusion 123 of a lid 121 of a metal housing 120. On the other hand, the fourth ground conductor 21 is a bottom wall 125 of a main body 124 of the metal housing 120.

[0072] That is, in this embodiment, the first dielectric layer 12 between the multilayer substrate 40 and the protruding portion 123 of the lid portion 121 is an air layer. Similarly, the fifth dielectric layer 20 between the multilayer substrate 40 and the bottom wall 125 of the main body portion 124 is an air layer.

[0073] 5 and other figures, in this embodiment, the conductive connection portion has penetrating through-hole portion 25 consisting of a plurality of through-holes that penetrate all layers from layer L2-1 to layer L2-4, non-penetrating through-hole portion 26 consisting of a plurality of through-holes that penetrate layers from layer L2-1 to layer L2-2, and non-penetrating through-hole portion 27 consisting of a plurality of through-holes that penetrate layers from layer L2-3 to layer L2-4. In addition, ground patterns 28 that are conductively connected to penetrating through-hole portion 25 are appropriately arranged on each of layers L2-1 to layer L2-4.

[0074] The surfaces of non-penetrating through-hole portion 26 and penetrating through-hole portion 25 that face the lower surface of protrusion 123 of lid portion 121 are attached, for example, with a conductive adhesive, to a part of the lower surface of protrusion 123. Similarly, the surfaces of non-penetrating through-hole portion 27 and penetrating through-hole portion 25 that face the upper surface of bottom wall 125 of main body portion 124 are attached, for example, with a conductive adhesive, to a part of the upper surface of bottom wall 125.

[0075] 5(b) and 5(c) and 7, four rectangular waveguides 29 are formed at the intersections 23, with the third dielectric layer 16 filling the spaces formed by the second ground conductor 15, the third ground conductor 17, and the penetrating through-holes 25. The oval portions in Fig. 7 indicate the cross sections of the rectangular waveguides 29.

[0076] 5(a) and 5(d), the width of the first strip conductor 13 and the second strip conductor 19 at the intersection 23 is narrower than the width of the first strip conductor 13 and the second strip conductor 19 at any other location than the intersection 23. This configuration allows the long side dimension a of the four rectangular waveguides 29 to be reduced, making it easy to set the cutoff frequencies of these rectangular waveguides 29 higher than the maximum frequency of the operating frequency band. Here, the operating frequency band is, for example, 600 MHz to 7.125 GHz, which is the FR1 frequency band.

[0077] Also, as shown in Figure 6(a), the thickness of the portion of the first dielectric layer 12 facing the first strip conductor 13 at the intersection 23 is thinner than the thickness of the portion of the first dielectric layer 12 other than the portion facing the first strip conductor 13 at the intersection 23.

[0078] Similarly, as shown in Figure 6(b), the thickness of the portion of the fifth dielectric layer 20 facing the second strip conductor 19 at the intersection 23 is thinner than the thickness of the portion of the fifth dielectric layer 20 other than the portion facing the second strip conductor 19 at the intersection 23.

[0079] That is, the crossing structure of the transmission line 2 is configured such that the thickness of the air layer of the first dielectric layer 12 and the fifth dielectric layer 20 is adjusted by gradually changing the height of the convex portion 123 of the lid portion 121 of the metal casing 120 and the bottom wall 125 of the main body portion 124 in accordance with the gradually changing width of the first strip conductor 13 and the second strip conductor 19.

[0080] In this way, by gradually changing the widths of the first strip conductor 13 and the second strip conductor 19 and the thicknesses of the air layers of the first dielectric layer 12 and the fifth dielectric layer 20, the line impedance at the intersection 23 and other than the intersection 23 is matched to, for example, 50 Ω. With this structure, the reflection loss at the intersection 23 can be suppressed.

[0081] 8 and 9 show the results of confirming the frequency characteristics near the intersection 23 of the transmission line 2 of this embodiment by electromagnetic field simulation.

[0082] Fig. 8 shows the transmission coefficient near the intersection 23 of a strip line including the first strip conductor 13 (or the second strip conductor 19). The simulation results in Fig. 8 show that the insertion loss at the intersection 23 is sufficiently small in the frequency band of FR1.

[0083] Fig. 9 shows the isolation between the first strip conductor 13 and the second strip conductor 19 near the intersection 23. The simulation results in Fig. 9 show that sufficient isolation is obtained at the intersection 23 in the frequency band of FR1.

[0084] As described above, in the crossing structure of the transmission line 2 according to this embodiment, the first strip conductor 13 is provided only on the L2-1 layer, and the second strip conductor 19 is provided only on the L2-4 layer. Moreover, the crossing structure of the transmission line 2 according to this embodiment has four rectangular waveguides 29 at the crossing portion 23 where the first strip conductor 13 and the second strip conductor 19 cross, each of which is formed by filling the third dielectric layer 16 in spaces formed by the second ground conductor portion 15, the third ground conductor portion 17, and the penetrating through-hole portion 25.

[0085] The crossing structure of the transmission lines 2 according to this embodiment configured in this manner can reduce the overall thickness of the multilayer substrate 40 and form the crossing portion 23 while maintaining good isolation.

[0086] Furthermore, the crossing structure of the transmission line 2 according to this embodiment is configured such that the thickness of the air layer of the first dielectric layer 12 and the fifth dielectric layer 20 is changed depending on the width of the first strip conductor 13 and the second strip conductor 19, thereby realizing optimal impedance for the entire transmission line 2 including the crossing portion 23.

[0087] Furthermore, in the intersection structure of the transmission line 2 according to this embodiment, the widths of the first strip conductor 13 and the second strip conductor 19 at the intersection 23 are narrower than the widths of the portions other than the intersection 23, so that the long side dimension a of the four rectangular waveguides 29 can be reduced, and an optimal cutoff frequency according to the frequency band to be used can be realized.

[0088] Furthermore, in the crossing structure of the transmission line 2 according to this embodiment, the first dielectric layer 12 and the fifth dielectric layer 20 are air layers with low dielectric constants and dielectric tangents, and therefore the insertion loss of the transmission line 2 can be reduced.

[0089] Furthermore, the crossing structure of the transmission line 2 according to this embodiment makes it possible to easily provide an air layer between the first dielectric layer 12 and the fifth dielectric layer 20 by configuring the first ground conductor portion 11 and the fourth ground conductor portion 21 as part of the metal housing 120. [Explanation of symbols]

[0090] 1,2 Transmission lines 11 First ground conductor portion 12 First dielectric layer 13 First strip conductor 14 Second dielectric layer 15 Second ground conductor part 16 Third dielectric layer 17 Third ground conductor 18 Fourth Dielectric Layer 19 Second strip conductor 20 Fifth dielectric layer 21 Fourth ground conductor part 23 Intersection 25 Through-hole part (conductive connection part) 26,27 Non-penetrating through-hole section 29 Rectangular waveguide 30,40 Multilayer board 100,110 Butler Matrix 120 Metal Case 121 Lid 122 Edge 123 Convex 124 Main body 125 bottom wall 126,126a,126b side wall

Claims

1. a first ground conductor portion (11); a first strip conductor (13) provided on a layer (L1-2, L2-1) below at least a part of the first ground conductor portion via a first dielectric layer (12); a second ground conductor portion (15) provided below the first strip conductor via a second dielectric layer (14); a third ground conductor (17) provided below the second ground conductor via a third dielectric layer (16); a second strip conductor (19) provided on a layer (L1-5, L2-4) below the third ground conductor portion via a fourth dielectric layer (18); a fourth ground conductor portion (21) at least a portion of which is provided below the second strip conductor via a fifth dielectric layer (20); a conductive connection portion (25) that conductively connects the first ground conductor portion, the second ground conductor portion, the third ground conductor portion, and the fourth ground conductor portion by penetrating at least the third dielectric layer, A crossing structure of transmission lines (1, 2) that transmit signals in a predetermined operating frequency band using the first strip conductor and the second strip conductor, At an intersection (23) where the first strip conductor and the second strip conductor intersect, four waveguides (29) are formed by filling the third dielectric layer in spaces formed by the second ground conductor portion, the third ground conductor portion, and the conductive connecting portion, A transmission line crossing structure, characterized in that the cutoff frequency of each of said waveguides is higher than the maximum frequency of said frequency band.

2. a width of the first strip conductor and the second strip conductor at the intersection is narrower than a width of the first strip conductor and the second strip conductor at a portion other than the intersection, a thickness of the first dielectric layer at the intersection, the thickness being opposite the first strip conductor, is thinner than a thickness of the first dielectric layer at other than the intersection, the thickness being opposite the first strip conductor; 2. The transmission line crossing structure according to claim 1, wherein a thickness of the fifth dielectric layer at the crossing portion facing the second strip conductor is thinner than a thickness of the fifth dielectric layer at other portions than the crossing portion facing the second strip conductor.

3. 3. The crossing structure of transmission lines according to claim 1, wherein the first dielectric layer and the fifth dielectric layer are air layers.

4. The multilayer substrate (40) may further include a metal housing (120) that houses the multilayer substrate (40) including the first strip conductor, the second dielectric layer, the second ground conductor portion, the third dielectric layer, the third ground conductor portion, the fourth dielectric layer, and the second strip conductor; 4. The transmission line crossing structure according to claim 3, wherein the first ground conductor portion and the fourth ground conductor portion are formed as part of the metal housing.

5. 3. The crossing structure of transmission lines according to claim 1, wherein the frequency band used is 600 MHz to 7.125 GHz.

6. A Butler matrix comprising the crossover structure of transmission lines according to claim 1 or 2.

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