Directional coupler

Abstract

To provide a directional coupler that achieves lower cost and smaller size.SOLUTION: A directional coupler has a waveguide and a substrate including a ground layer, which is opposite the side of the waveguide and constitutes a stripline, on the side surface, two first holes are provided along the direction of propagation of radio waves in the waveguide, and in the ground layer, two second holes are provided, each opposite to the two first holes.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a directional coupler. [Background technology]

[0002] For example, Patent Document 1 (JP Patent Publication 4-150601A) discloses the following directional coupler: That is, in a waveguide directional coupler in which coupling holes are provided in a common wall in which first and second ridge waveguides are superimposed so as to be perpendicular to each other, the directional coupler has a plurality of coupling holes provided in any one of the sections of the common wall partitioned by the ridges of the first and second ridge waveguides, to provide a path difference for radio waves propagating from the first waveguide in a predetermined direction to the second waveguide. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 4-150601 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology described in Patent Document 1, the directional coupler is configured with two waveguides, which causes a problem that the directional coupler becomes large in size. In addition, the waveguide is expensive, which causes a problem that the cost of the directional coupler increases.

[0005] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a directional coupler that can be made smaller and less expensive. [Means for solving the problem]

[0006] (1) In order to solve the above problems, a directional coupler according to one aspect of the present invention comprises a substrate including a waveguide and a ground layer facing a side surface of the waveguide, the substrate constituting a stripline, wherein two first hole portions are provided on the side surface along a propagation direction of radio waves in the waveguide, and two second hole portions are provided in the ground layer facing the two first hole portions, respectively.

[0007] With this configuration, the number of waveguides constituting the directional coupler can be reduced compared to when the directional coupler is composed of two waveguides, making it possible to provide a directional coupler that is low-cost and compact.

[0008] (2) In the above (1), the substrate may further include a ground region provided on the opposite side of the ground layer to the surface facing the side surface and at a position corresponding to the two second hole portions.

[0009] With this configuration, it is possible to suppress external leakage of radio waves propagating from the waveguide through the first hole and the second hole to the strip line, thereby improving the degree of coupling in the directional coupler.

[0010] (3) In the above (1) or (2), the substrate may further include a signal line of the stripline provided on the side opposite to the side surface of the ground layer and extending along the propagation direction, and a width of the signal line at corresponding positions corresponding to the positions of each of the two second hole portions may be larger than a width of the signal line at positions other than the corresponding positions.

[0011] In this way, by configuring the stripline signal line so that the width of the signal line is adjusted taking into account its positional relationship with the hole provided in the ground layer, it is possible to easily adjust the impedance of the directional coupler when holes are provided in the ground layer and dielectric layer of the substrate.

[0012] (4) In any one of the above (1) to (3), the area of ​​each of the two second hole portions may be smaller than the area of ​​each of the two first hole portions.

[0013] With this configuration, the intensity of the radio wave propagating from the waveguide to the stripline can be reduced, compared to a configuration in which the area of ​​the second hole is the same as the area of ​​the first hole.

[0014] (5) In any of (1) to (4) above, when the electrical length of the transmission path between the two first holes is EL1, the electrical length of the transmission path between the two second holes is EL2, and the wavelength of the radio wave is λ, EL1 and EL2 may respectively satisfy the following equations (1) and (2). EL1=λ / 4 (1) EL2=(1 / 4+1 / 2×N)×λ ···(2) Here, N is an integer.

[0015] With this configuration, the phase of the radio waves traveling along one path can be made to be inverse to the phase of the radio waves traveling along the other path, depending on the difference between the electrical length of the path along which the radio waves branched in the waveguide pass through one of the two first holes and the corresponding second hole, propagate along the signal line of the stripline, and arrive at the other second hole, and the electrical length of the path along which the radio waves pass through the other of the two first holes and the corresponding second hole, propagate along the signal line, and arrive at one second hole. This allows the radio waves propagating in one direction along the signal line to be canceled out at the second hole, thereby achieving radio wave directionality in the directional coupler. Effect of the Invention

[0016] According to the present invention, it is possible to provide a directional coupler that realizes low cost and small size. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view illustrating a schematic configuration of a directional coupler according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a plan view illustrating a schematic configuration of a waveguide according to an embodiment of the present invention. [Diagram 3] FIG. 3 is a cross-sectional view showing a cross section of the waveguide according to the embodiment of the present invention taken along line III-III in FIG. [Figure 4] FIG. 4 is a plan view that illustrates a schematic configuration of a substrate according to an embodiment of the present invention. [Diagram 5] FIG. 5 is a cross-sectional view showing a cross section along the line VV in FIG. 4 of the substrate according to the embodiment of the present invention. [Figure 6] FIG. 6 is a plan view showing a schematic configuration of a first ground layer of a board according to an embodiment of the present invention. [Figure 7] FIG. 7 is a diagram for explaining the shape of a signal line conductor included in the substrate according to the embodiment of the present invention. [Figure 8] FIG. 8 is a diagram for explaining the directionality of radio waves in a directional coupler according to an embodiment of the present invention. [Figure 9] FIG. 9 is a diagram for explaining the directionality of radio waves in a directional coupler according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference characters and their description will not be repeated. In addition, at least some of the embodiments described below may be arbitrarily combined.

[0019] Fig. 1 is a perspective view showing a schematic configuration of a directional coupler according to an embodiment of the present invention. Referring to Fig. 1, directional coupler 101 includes a waveguide 11 and a substrate 21. Substrate 21 is fixed to waveguide 11 by a fixing member such as a screw.

[0020] The directional coupler 101 is provided, for example, in a radar device that monitors a water-based moving object such as a ship. Specifically, for example, the directional coupler 101 is provided in the radar device to extract a part of the radio wave E transmitted from a transmitter as a radio wave for power monitoring.

[0021] [Waveguide] Fig. 2 is a plan view showing a schematic configuration of a waveguide according to an embodiment of the present invention. Fig. 3 is a cross-sectional view showing a cross section of the waveguide according to the embodiment of the present invention taken along line III-III in Fig. 2. With reference to Figs. 1 to 3, waveguide 11 propagates radio waves E. Specifically, for example, waveguide 11 propagates radio waves in the X-band (X-band: 8 GHz to 12 GHz).

[0022] The waveguide 11 is, for example, a rectangular waveguide. The waveguide 11 has a first end 11a, a second end 11b, and a hollow portion 11c. The hollow portion 11c extends in the longitudinal direction of the waveguide 11.

[0023] The first end 11a and the second end 11b have an opening 11d and an opening 11e, respectively. The opening 11d and the opening 11e form a part of the hollow portion 11c.

[0024] Here, the axis parallel to the longitudinal direction of the waveguide 11 and pointing in the direction from the second end 11b to the first end 11a of the waveguide 11 is defined as the y-axis. The axis perpendicular to the y-axis is defined as the x-axis. The x-axis points vertically upward, for example. The axis perpendicular to the x-axis and y-axis is defined as the z-axis. The z-axis is oriented such that the x-axis, y-axis, and z-axis form a right-handed coordinate system.

[0025] For example, the cross section of waveguide 11 is rectangular in a plane perpendicular to the longitudinal direction of waveguide 11, i.e., in the xz plane. In waveguide 11, the side surface including the long side of the rectangle is H-plane 11f, and the side surface including the short side of the rectangle is E-plane 11g.

[0026] For example, on the H-plane 11f of the waveguide 11, two first holes 12a and 12b are provided along the propagation direction of the radio wave in the waveguide 11, that is, along the y-axis direction.

[0027] For example, the first holes 12a and 12b have a rectangular shape that is long in the z-axis direction in plan view. The first holes 12a and 12b may have another shape, such as a circular shape, in plan view.

[0028] In this embodiment, for example, the size and shape of the first hole 12a are the same as the size and shape of the first hole 12b, but the size and shape of the first hole 12a may be different from the size and shape of the first hole 12b.

[0029] If the electrical length of the transmission path between the first hole 12a and the first hole 12b is EL1 and the wavelength of the radio wave E propagating through the waveguide 11 is λ, the relationship between the electrical length EL1 and the wavelength λ is expressed by the following equation (1). EL1=λ / 4 (1)

[0030] For example, the electrical length EL1 is set by adjusting the length of the waveguide 11 in the longitudinal direction.

[0031] At least one of the first holes 12a and 12b may be provided on the H surface 11f, shifted in the z-axis direction. In addition, in the waveguide 11, the two first holes 12a and 12b may be provided on the E surface 11g instead of the H surface 11f.

[0032] [substrate] Fig. 4 is a plan view showing a configuration of a substrate according to an embodiment of the present invention. Fig. 5 is a cross-sectional view showing a cross section along line VV in Fig. 4 of the substrate according to the embodiment of the present invention. With reference to Figs. 1, 4 and 5, substrate 21 is, for example, a printed wiring board. Substrate 21 has a first main surface 21a facing waveguide 11 and a second main surface 21b provided on the opposite side to first main surface 21a.

[0033] The substrate 21 includes a first ground layer 31, a dielectric layer 32, and a second ground layer 33. The first ground layer 31, the dielectric layer 32, and the second ground layer 33 are laminated in this order from the first main surface 21a side of the substrate 21.

[0034] The first ground layer 31 faces the H-plane 11f of the waveguide 11 in the stacking direction. A surface 31a of the first ground layer 31 facing the H-plane 11f (hereinafter also referred to as the "facing surface") constitutes the first main surface 21a of the substrate 21. The first ground layer 31 is provided over substantially the entire substrate 21 in a plan view of the yz plane seen from above (hereinafter also simply referred to as the "plan view"). The first ground layer 31 is a thin conductor such as copper foil.

[0035] Fig. 6 is a plan view showing a schematic configuration of a first ground layer of a board according to an embodiment of the present invention. With reference to Figs. 5 and 6, first ground layer 31 is provided with two second holes 41a and 41b that face two first holes 12a and 12b shown in Fig. 2, respectively.

[0036] Specifically, for example, in the first ground layer 31, the two second holes 41a and 41b are provided at positions overlapping with the two first holes 12a and 12b, respectively, in a plan view. The second holes 41a and 41b penetrate the first ground layer 31.

[0037] For example, the second holes 41a and 41b have a rectangular shape that is long in the z-axis direction in plan view. The second holes 41a and 41b may have another shape, such as a circular shape, in plan view.

[0038] In this embodiment, for example, the size and shape of the second hole 41a are the same as the size and shape of the second hole 41b. Note that the size and shape of the second hole 41a may be different from the size and shape of the second hole 41b.

[0039] 2 and 6, the area A2 of each of the two second hole portions 41a, 41b is smaller than the area A1 of each of the two first hole portions 12a, 12b.

[0040] Specifically, for example, the length L2 in the z-axis direction of each of the two second holes 41a, 41b is smaller than the length L1 in the z-axis direction of each of the two first holes 12a, 12b. As a result, the area A2 is smaller than the area A1. The area A2 may be the same as the area A1.

[0041] 5, the dielectric layer 32 is disposed between the first ground layer 31 and the second ground layer 33, and insulates the first ground layer 31 from the second ground layer 33. The dielectric layer 32 is provided over substantially the entire area of ​​the substrate 21 in a plan view. The material of the dielectric layer 32 is, for example, glass epoxy resin.

[0042] The second ground layer 33 is located on a surface 31b side opposite to the opposing surface 31a of the first ground layer 31. The second ground layer 33 constitutes the second main surface 21b of the substrate 21. The second ground layer 33 is provided over substantially the entire area of ​​the substrate 21 in a plan view. The second ground layer 33 is a thin conductor such as copper foil.

[0043] Referring again to FIG. 5, first ground layer 31, dielectric layer 32 and second ground layer 33 in substrate 21 form a stripline.

[0044] In this embodiment, a signal line conductor 51 which is a stripline signal line S is formed inside the dielectric layer 32. That is, the substrate 21 includes the signal line conductor 51 provided on the side opposite to a surface 31a of the first ground layer 31 which faces the H-plane 11f (hereinafter also referred to as the "facing surface").

[0045] FIG. 7 is a diagram for explaining the shape of a signal line conductor included in the substrate according to the embodiment of the present invention.

[0046] 7, the signal line conductor 51 extends along the propagation direction of the radio wave E in the waveguide 11, that is, along the y-axis direction. The signal line conductor 51 has a first end 51a and a second end 51b.

[0047] When the width of the signal line conductor 51 at a position corresponding to each of the two second hole portions 41a, 41b (hereinafter also referred to as "corresponding position P1") is W1 and the width of the signal line conductor 51 at a position P2 other than the corresponding position P1 is W2, the width W1 is larger than the width W2.

[0048] Specifically, for example, the corresponding position P1 corresponds to the positions of regions 51c and 51d in the signal line conductor 51 that overlap with the second holes 41a and 41b, respectively, in a plan view. The position P2 corresponds to the position of a region 51e in the signal line conductor 51 other than the regions 51c and 51d, i.e., the region 51e that does not overlap with the second holes 41a and 41b in a plan view.

[0049] 4 and 5, for example, substrate 21 includes a ground area 61 provided on the side opposite opposing surface 31a of first ground layer 31 and at a position corresponding to two second hole portions 41a, 41b. In the present embodiment, ground area 61 constitutes a part of second ground layer 33.

[0050] Specifically, for example, in the second ground layer 33, the ground area 61 is provided at a position overlapping with the two second hole portions 41a and 41b in a plan view.

[0051] [Electrical length of the transmission path between the second holes 41a and 41b] When the electrical length of the transmission path between the second hole 41a and the second hole 41b is EL2, the relationship between the electrical length EL2 and the wavelength λ of the radio wave E is expressed by the following formula (2): In formula (2), N is an integer. EL2=(1 / 4+1 / 2×N)×λ ···(2)

[0052] For example, the electrical length EL2 is set by adjusting the dielectric constant of the dielectric layer 32. Alternatively, for example, the electrical length EL2 is set by providing a meander line between the second holes 41a and 41b. In this embodiment, the electrical length EL2 is set to 3λ / 4.

[0053] [Direction of radio waves] 8 and 9 are diagrams for explaining the directionality of radio waves in a directional coupler according to an embodiment of the present invention.

[0054] 8 and 9, in waveguide 11, opening 11d at first end 11a constitutes an input port of directional coupler 101, and opening 11e at second end 11b constitutes an output port of directional coupler 101.

[0055] FIG. 8 is a diagram for explaining the phase difference between a path length T11 when radio wave E branched in waveguide 11 travels along path R11 and a path length T12 when radio wave E travels along path R12.

[0056] Path R11 is a path along which the radio wave E propagating from the first end 11a to the second end 11b branches, passes through the first hole 12b in the waveguide 11 and the second hole 41b in the first ground layer 31, and propagates in the negative direction of the y-axis through the signal line conductor 51 shown in Fig. 7. Path R12 is a path along which the radio wave E propagating from the first end 11a to the second end 11b branches, passes through the first hole 12a and the second hole 41a, and propagates in the negative direction of the y-axis through the signal line conductor 51.

[0057] The path length T11 when the radio wave E travels along the path R11 is the sum of the electrical length EL0 of the transmission path between the opening d in the waveguide 11 and the first hole 12a, the electrical length EL1 of the transmission path between the two first holes 12a, 12b, and the electrical length EL10 of the transmission path between the region 51d and the second end 51b of the signal line conductor 51 shown in FIG. 7.

[0058] When the radio wave E travels along the route R12, the route length T12 is the sum of the electrical length EL0, the electrical length EL2 of the transmission path between the two second holes 41a, 41b, and the electrical length EL10.

[0059] As expressed by the above-mentioned formula (1) and formula (2), the electrical length EL1 and the electrical length EL2 are λ / 4 and 3λ / 4, respectively. Therefore, the absolute value of the difference between the path length T11 and the path length T12, that is, the phase difference between the phase of the radio wave E traveling along the path R11 and the phase of the radio wave E traveling along the path R12, is λ / 2. In this case, the radio wave E traveling along the path R11 and the radio wave E traveling along the path R12 cancel each other out, so the radio wave E is not extracted from the directional coupler 101.

[0060] FIG. 9 is a diagram for explaining the phase difference between a path length T21 when radio wave E branched in waveguide 11 travels along path R21 and a path length T22 when radio wave E travels along path R22.

[0061] Path R21 is a path along which the radio wave E propagating from the first end 11a to the second end 11b branches, passes through the first hole 12b in the waveguide 11 and the second hole 41b in the first ground layer 31, and propagates in the positive direction of the y-axis through the signal line conductor 51 shown in Fig. 7. Path R22 is a path along which the radio wave E propagating from the first end 11a to the second end 11b branches, passes through the first hole 12a and the second hole 41a, and propagates in the positive direction of the y-axis through the signal line conductor 51.

[0062] When the radio wave E travels along the route R21, the route length T21 is the sum of the electrical lengths EL1 and EL2, that is, λ. When the radio wave E travels along the route R22, the route length T22 is the wavelength λ of the radio wave E.

[0063] The phase difference between path length T21 and path length T22 is 0. In this case, the radio wave E traveling along path R21 and the radio wave E traveling along path R22 are in phase, so that the radio wave E is extracted from directional coupler 101.

[0064] Referring again to FIG. 4, on a surface 33b of the second ground layer 33 opposite to a surface 33a facing the dielectric layer 32, two signal line conductors 71a, 71b and two via holes 72a, 72b are provided.

[0065] In this embodiment, the signal line conductor 71 a constitutes the coupled port of the directional coupler 101 , and the signal line conductor 71 b constitutes the isolated port of the directional coupler 101 .

[0066] The via hole 72a electrically connects the signal line conductor 51 and the signal line conductor 71a. The via hole 72b electrically connects the signal line conductor 51 and the signal line conductor 71b. The radio wave E propagating through the signal line conductor 51 propagates to the signal line conductor 71a through the via hole 72a. The signal line conductor 71a propagates the radio wave E acquired by the directional coupler 101 to a monitoring device (not shown).

[0067] In a radar device, in order to monitor the power of radio waves E transmitted from a transmitter, for example, a radio wave for power monitoring may be extracted through a pin fixed to a waveguide. However, in this case, the directionality of the radio waves extracted by the pin is not ensured, so there is a problem that the power value being monitored varies due to load fluctuations. In addition, there is a problem that the cost of a coaxial connector including a pin is high.

[0068] In addition, in a radar device, a directional coupler having two waveguides may be used to extract radio waves for power monitoring. In this case, since the directional coupler is composed of two waveguides, there is a problem that the directional coupler becomes large in size. In addition, since the cost of the waveguide is high, there is a problem that the cost of the directional coupler increases.

[0069] In contrast, directional coupler 101 according to the embodiment of the present invention can achieve low cost and small size due to the above-mentioned configuration.

[0070] The above-described embodiments should be considered as illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0071] 11 Waveguide 11a First end 11b Second end 11c Hollow part 11d opening 11e opening 11f H side 11g E side 12a,12b 1st hole 21 Substrate 31 First Ground Layer 31a,31b,33a,33b side 32 Dielectric layer 33 Second Ground Layer 41a,41b 2nd hole 51, 71a, 71b Signal line conductor 72a, 72B Via holes 101 Directional coupler E Radio Waves EL1,EL2 electrical length λ wavelength

Claims

1. A waveguide; a ground layer facing a side surface of the waveguide, the substrate including said ground layer forming a strip line; Two first holes are provided on the side surface along a propagation direction of radio waves in the waveguide, a first hole portion and a second hole portion, the first hole portion being opposed to each other, the first hole portion being opposed to each other, the first hole portion being opposed to each other, the second ...

2. The substrate further comprises:

2. The directional coupler according to claim 1, further comprising a ground region provided on a surface of the ground layer opposite to the surface facing the side surface and at positions corresponding to the two second holes.

3. The substrate further comprises: a signal line of the strip line provided on a surface of the ground layer opposite to the surface facing the side surface and extending along the propagation direction; 3. The directional coupler according to claim 1, wherein a width of the signal line at corresponding positions that correspond to the positions of the two second holes is greater than a width of the signal line at positions other than the corresponding positions.

4. 3. The directional coupler according to claim 1, wherein an area of ​​each of the two second holes is smaller than an area of ​​each of the two first holes.

5. 3. The directional coupler according to claim 1, wherein, when an electrical length of a transmission path between the two first holes is EL1, an electrical length of a transmission path between the two second holes is EL2, and a wavelength of the radio wave is λ, EL1 and EL2 respectively satisfy the following formulas (1) and (2). EL1=λ / 4...(1) EL2=(1 / 4+1 / 2×N)×λ...(2) Here, N is an integer.

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