Rotary joint

Abstract

To provide a configuration capable of suppressing disturbance of a radio wave at a certain frequency caused by uneven reflection of the radio wave due to rotation in a rotary joint having a double coaxial structure.SOLUTION: A rotary joint 1 includes a first waveguide member 11, a second waveguide member 12, a center conductor, an inner tube conductor, and an outer tube conductor. A first waveguide path 91 and a second waveguide path 92 are formed in the first waveguide member 11, and a third waveguide path 93 and a fourth waveguide path 94 are formed in the second waveguide member 12. The inner tube conductor is disposed so as to cover the outside of the central conductor, forms an inner coaxial path that connects the first waveguide path 91 and the third waveguide path 93 together with the central conductor, and includes a first tube conductor and a second tube conductor that are arranged in the longitudinal direction, are rotatably coupled to each other, and are insulated from each other. The outer tube conductor is disposed so as to cover the outside of the inner tube conductor, and forms an outer coaxial path connecting the second waveguide path 92 and the fourth waveguide path 94 together with the inner tube conductor.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention primarily relates to a rotary joint having a waveguide path formed therein. [Background technology]

[0002] Rotary joints that rotatably connect two waveguides have been known for some time. The rotary joints disclosed in Patent Documents 1 and 2 have a single coaxial structure that is composed of an inner conductor and an outer conductor disposed outside the inner conductor.

[0003] In contrast, Non-Patent Document 1 discloses a rotary joint with a double coaxial structure consisting of a center conductor, an inner tubular conductor, and an outer tubular conductor. In the rotary joint with a double coaxial structure, an inner coaxial path is formed between the center conductor and the inner tubular conductor, and an outer coaxial path is formed between the inner tubular conductor and the outer tubular conductor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 63-49801 [Patent Document 2] Japanese Patent Application Publication No. 58-107034 [Non-patent literature]

[0005] [Non-Patent Document 1] George L. Ragan, "Microwave Transmission Circuits", (USA), MIT Radiation Laboratory Series, volume 9, pp. 451-455, 1948 Summary of the Invention [Problem to be solved by the invention]

[0006] In a rotary joint with a double coaxial structure, depending on the thickness of the conductor, the propagation modes can be TEM and TE. 11 Therefore, in these rotary joints, TE 11 In Non-Patent Document 1, a mode filter is realized by contacting the end of the inner pipe conductor with the wall surface. However, in Non-Patent Document 1, the mode filter does not work effectively because there is a choke near the end of the inner pipe conductor, and furthermore, in this configuration, the end of the inner pipe conductor is not in contact with the wall surface, which causes uneven reflection of radio waves during rotation. As a result of the uneven reflection of radio waves due to rotation, there is a possibility that the propagated radio waves will be disturbed at certain frequencies (i.e., depending on the frequency, the TEM mode and TE mode may be different). 11 Due to the different configuration of the modes, TE 11 (At frequencies where the proportion of modes is high, rotation irregularities occur.)

[0007] The present invention has been made in view of the above circumstances, and its main object is to provide a configuration that can suppress radio wave disturbance at a certain frequency caused by non-uniform reflection of radio waves due to rotation in a rotary joint having a double coaxial structure.

[0008] The problem to be solved by the present invention is as described above. Next, the means for solving this problem and the effects thereof will be explained.

[0009] According to an aspect of the present invention, there is provided a rotary joint having the following configuration. Specifically, the rotary joint comprises a first waveguide member, a second waveguide member, a center conductor, an inner ductor, and an outer ductor. The first waveguide member has a first waveguide path and a second waveguide path formed therein. The second waveguide member is rotatable relative to the first waveguide member and has a third waveguide path and a fourth waveguide path formed therein. The inner ductor is arranged to cover the outside of the center conductor and, together with the center conductor, forms an inner coaxial path connecting the first waveguide path and the third waveguide path. The inner ductor is composed of two or more rotatably connected and insulated ductors arranged in the longitudinal direction. The outer ductor is arranged to cover the outside of the inner ductor and, together with the inner ductor, forms an outer coaxial path connecting the second waveguide path and the fourth waveguide path.

[0010] This makes it possible to suppress the disturbance of radio waves at certain frequencies caused by uneven reflection of radio waves due to rotation, and also to improve TE 11 A rotary joint having a mode filter of the above can be realized. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is an external perspective view of a rotary joint according to an embodiment of the present invention; [Figure 2] A side cross-sectional view of a rotary joint (cross-section AA in Figure 1). [Figure 3] FIG. 2 is an enlarged cross-sectional view of a rotary joint (enlarged view of the dashed line portion in FIG. 2). [Figure 4] FIG. 4 is a diagram illustrating the rotation angle of a rotary joint. [Figure 5] 10 is a graph comparing the reflection coefficient (S11 characteristics) according to the rotation angle of the rotary joint between a conventional example and this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Next, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is an external perspective view of a rotary joint 1 according to an embodiment of the present invention. Fig. 2 is a side cross-sectional view of the rotary joint 1 (a cross-sectional view taken along line AA in Fig. 1). Fig. 3 is an enlarged cross-sectional view of the rotary joint 1 (an enlarged view of the dashed line portion in Fig. 2). In the following description, terms describing positional relationships, size, shape, etc. are intended to include not only configurations in which the meaning of the term is completely valid, but also configurations in which the meaning of the term is approximately valid.

[0013] The rotary joint 1 is used in radar antennas for transmitting and receiving radio waves such as microwaves for meteorological or marine use, etc., to connect a waveguide between an antenna section (movable section) configured to be able to change its orientation and a support member (fixed section) that supports the antenna section. The rotary joint 1 has two paths formed therein, allowing the propagation of two types of radio waves (for example, radio waves with different polarization directions).

[0014] 1, rotary joint 1 includes first waveguide member 11, second waveguide member 12, and connecting portion 13. Second waveguide member 12 and connecting portion 13 are configured to be rotatable relative to first waveguide member 11.

[0015] 1 and 2, the first waveguide member 11 is formed with a first waveguide path 91 and a second waveguide path 92. The second waveguide member 12 is formed with a third waveguide path 93 and a fourth waveguide path 94. The coupling portion 13 is formed with an inner coaxial path 95 and an outer coaxial path 96. The inner coaxial path 95 connects the first waveguide path 91 and the third waveguide path 93. The outer coaxial path 96 connects the second waveguide path 92 and the fourth waveguide path 94.

[0016] The first waveguide 11, the second waveguide 12, and the connecting portion 13 will be described in detail below. The first waveguide 11 is a metallic (conductive) member having a substantially rectangular parallelepiped shape. The first waveguide 91 and the second waveguide 92 are spaces formed in the first waveguide 11. The second waveguide 92 is formed closer to the connecting portion 13 (the second waveguide 12) than the first waveguide 91. The first waveguide 91 and the second waveguide 92 have the same path length direction. The first waveguide 91 and the second waveguide 92 are rectangular holes (rectangular waveguides), and corresponding openings are formed on the same surface of the first waveguide 11. The first waveguide 91 and the second waveguide 92 may have different shapes, and the openings may be formed at different locations. Radio waves input to the first waveguide 91 and the second waveguide 92 via the connecting portion 13 are output from these openings. Furthermore, the radio waves input through these openings are output to the connecting portion 13 through the first waveguide path 91 and the second waveguide path 92. The first waveguide member 11 may be configured to only input or output radio waves.

[0017] Furthermore, a connecting portion 13 is attached to one surface of the first waveguide 11 (the surface facing the second waveguide 12). The first waveguide 11 has a bearing 71 and an outer cylindrical portion 72 as parts for attaching the connecting portion 13. The connecting portion 13 (more specifically, the outer expanded diameter portion 52) is attached to the inside of the bearing 71. The outer cylindrical portion 72 is formed inside the bearing 71 and is a cylindrical portion that protrudes toward the second waveguide 12. The axial direction of the outer cylindrical portion 72 is the same as the axial direction of the connecting portion 13. The connecting portion 13 (more specifically, the outer expanded diameter portion 52 and the tubular conductor 51 described below) is attached so as to cover the outer cylindrical portion 72.

[0018] The second waveguide 12 is a substantially rectangular parallelepiped member made of metal (conductive), similar to the first waveguide 11. The fourth waveguide 94 is formed closer to the coupling portion 13 (first waveguide 11) than the third waveguide 93. The third waveguide 93 and the fourth waveguide 94 have the same configuration as the first waveguide 91 and the second waveguide 92, and therefore their description will be omitted. The coupling portion 13 is attached to the second waveguide 12 so as not to rotate relative to it.

[0019] The coupling section 13 mechanically couples the first waveguide member 11 and the second waveguide member 12, and also connects the waveguide paths formed in the first waveguide member 11 and the second waveguide member 12, as described above. The coupling section 13 comprises, in order from the inside in the axial direction, a cylindrical center conductor 30, a cylindrical inner conductor 40, and a cylindrical outer conductor 50. The center conductor 30, the inner conductor 40, and the outer conductor 50 have the same axial position. An inner coaxial path 95 is formed in the space between the center conductor 30 and the inner conductor 40, with the center conductor 30 as the inner conductor and the inner conductor 40 as the outer conductor. An outer coaxial path 96 is formed in the space between the inner conductor 40 and the outer conductor 50, with the inner conductor 40 as the inner conductor and the outer conductor 50 as the outer conductor.

[0020] The central conductor 30 extends from the first waveguide 91 of the first waveguide 11 to the third waveguide 93 of the second waveguide 12. In this embodiment, a spherical conductor is connected to one end of the central conductor 30. This spherical conductor is attached to the wall of the first waveguide 91 (more specifically, the wall farther from the second waveguide 12) by an insulating spherical conductor support member. The other end of the central conductor 30 is similarly attached to the wall of the third waveguide 93 (more specifically, the wall farther from the first waveguide 11) via the spherical conductor and the spherical conductor support member. The central conductor 30 may be attached to each wall via a conductor other than a sphere, or may be attached to each wall via an insulator that directly supports the central conductor 30 (for example, an insulator arranged to be inserted into a hole formed in the central conductor 30).

[0021] As shown in Fig. 3, the central conductor 30 includes a first rod-shaped conductor 31 and a second rod-shaped conductor 35. The first rod-shaped conductor 31 and the second rod-shaped conductor 35 have the same diameter and are arranged side by side in the longitudinal direction (axial direction). The second rod-shaped conductor 35 is arranged closer to the second waveguide 12 than the first rod-shaped conductor 31. The first rod-shaped conductor 31 and the second rod-shaped conductor 35 are connected inside the first waveguide 11 and closer to the second waveguide 12 than the second waveguide path 92, but may be connected at a different position.

[0022] As shown in FIG. 3 , a cylindrical portion 32 is formed (includes a cylindrical portion 32) at the axial end of the first rod-shaped conductor 31 (more specifically, the end connected to the second rod-shaped conductor 35). In this specification, the term "end" is a concept that includes not only the end but also the vicinity thereof. The cylindrical portion 32 has the same axial position as the first rod-shaped conductor 31 and is formed to protrude from the first rod-shaped conductor 31 in the axial direction (more specifically, toward the second waveguide member 12 and the second rod-shaped conductor 35). The diameter of the cylindrical portion 32 is smaller than that of the first rod-shaped conductor 31.

[0023] Furthermore, a circular hole 36 is formed in the axial end of the second rod-shaped conductor 35 (more specifically, the end connected to the first rod-shaped conductor 31). The circular hole 36 has the same axial position as the second rod-shaped conductor 35, and is formed so that its depth direction and axial direction from the second rod-shaped conductor 35 (more specifically, the first waveguide member 11 side and the first rod-shaped conductor 31 side) are the same. The inner diameter of the circular hole 36 is smaller than that of the second rod-shaped conductor 35 and larger than that of the cylindrical portion 32.

[0024] The cylindrical portion 32 of the first rod-shaped conductor 31 is inserted into the circular hole 36 of the second rod-shaped conductor 35. This configuration allows the second rod-shaped conductor 35 to rotate relative to the first rod-shaped conductor 31. Furthermore, since the cylindrical portion 32 and the inner wall of the circular hole 36 are not in contact with each other, the first rod-shaped conductor 31 and the second rod-shaped conductor 35 are insulated from each other. To ensure insulation more reliably, the cylindrical portion 32 is covered with an insulator (insulator tube 38 shown in FIG. 3), for example.

[0025] The inner pipe conductor 40 is disposed between the center conductor 30 and the outer pipe conductor 50. The inner pipe conductor 40 is formed from the vicinity of the first waveguide 91 of the first waveguide member 11 (specifically, a position where it does not protrude into the first waveguide 91 and where no gap is formed between it and the second waveguide 92) to the vicinity of the third waveguide 93 of the second waveguide member 12 (the exact position is the same as the first waveguide 91). With this configuration, an inner coaxial path 95 formed by the center conductor 30 and the inner pipe conductor 40 connects the first waveguide 91 and the third waveguide 93. In other words, the inner pipe conductor 40 divides the space so that the inner coaxial path 95 is not connected to the second waveguide 92 and so that the inner coaxial path 95 is not connected to the fourth waveguide 94. In addition, a TE is formed around the inner pipe conductor 40 on the wall surface of the second waveguide 92 (the wall surface on the first waveguide 91 side). 11 A recess (mode filter) is formed to set the mode to 0. Similarly, a TE is formed around the inner conductor 40 on the wall surface of the fourth waveguide 94 (the wall surface on the third waveguide 93 side). 11 A recess (mode filter) is formed to set the mode to 0. The central conductor 30 and the inner tube conductor 40 may connect the first waveguide path 91 and the third waveguide path 93 via separate members.

[0026] As shown in Fig. 3, the inner tubular conductor 40 includes a first tubular conductor 41 and a second tubular conductor 45. The first tubular conductor 41 and the second tubular conductor 45 have the same tubular diameter and are arranged side by side in the longitudinal direction (axial direction). The second tubular conductor 45 is arranged closer to the second waveguide member 12 than the first tubular conductor 41. The connection position between the first tubular conductor 41 and the second tubular conductor 45 is the same as the connection position between the first rod-shaped conductor 31 and the second rod-shaped conductor 35, but may be different.

[0027] 3, the inner tubular conductor 40 has an inner cylindrical portion 42 at the axial end of the first tubular conductor 41 (more specifically, the end on the side connected to the second tubular conductor 45). The inner cylindrical portion 42 has the same axial position as the first tubular conductor 41 and is formed so as to protrude from the first tubular conductor 41 in the axial direction (more specifically, toward the second waveguide member 12 and the second tubular conductor 45). The inner cylindrical portion 42 protrudes in the axial direction from the radially outer side of the first tubular conductor 41. In other words, the inner diameter of the inner cylindrical portion 42 is larger than the outer diameter of the first tubular conductor 41.

[0028] An inner expanded diameter portion 46 is formed at the axial end of the second tubular conductor 45 (more specifically, the end on the side connected to the first tubular conductor 41). The inner expanded diameter portion 46 has the same axial position as the second tubular conductor 45. The inner expanded diameter portion 46 is composed of a disk-shaped portion having a hole formed therein for inserting the second tubular conductor 45, and a cylindrical portion protruding from the edge of the disk-shaped portion toward the first waveguide member 11. With this configuration, an inner annular groove 47 is formed in the second tubular conductor 45.

[0029] The inner cylindrical portion 42 of the first tubular conductor 41 is inserted into the inner annular groove 47 of the second tubular conductor 45. This configuration allows the second tubular conductor 45 to rotate relative to the first tubular conductor 41. Furthermore, since the inner cylindrical portion 42 and the inner wall of the inner annular groove 47 are not in contact with each other, the first tubular conductor 41 and the second tubular conductor 45 are insulated from each other. To ensure insulation more reliably, the inner cylindrical portion 42 is covered with an insulator (insulator tube 48 shown in FIG. 3), for example.

[0030] The outer tube conductor 50 is disposed outside the inner tube conductor 40. The outer tube conductor 50 is formed from the vicinity of the second waveguide 92 of the first waveguide member 11 (more specifically, a position not projecting into the second waveguide 92) to the vicinity of the fourth waveguide 94 of the second waveguide member 12 (more specifically, a position not projecting into the fourth waveguide 94). With this configuration, an outer coaxial path 96 formed by the inner tube conductor 40 and the outer tube conductor 50 connects the second waveguide path 92 and the fourth waveguide path 94.

[0031] The outer tubular conductor 50 includes a tubular conductor 51 and an outer expanded diameter portion 52 formed at the axial end of the tubular conductor 51 (the end on the first waveguide member 11 side). The outer expanded diameter portion 52 has substantially the same shape as the inner expanded diameter portion 46. The outer cylindrical portion 72 described above is inserted into the annular groove 53 formed by the tubular conductor 51 and the outer expanded diameter portion 52. The outer side of the outer expanded diameter portion 52 is attached to a bearing 71. With the above configuration, the outer tubular conductor 50 is rotatable with respect to the first waveguide member 11. The outer tubular conductor 50 (tubular conductor 51) is attached to the second waveguide member 12 so as not to rotate relative to it.

[0032] Furthermore, depending on the length of the connecting portion 13 (specifically, the electrical length, which is the length taking into consideration the dielectric constants of the inner coaxial path 95 and the outer coaxial path 96), the TE of the radio wave may be increased in the target frequency band. 11 There is a possibility that resonance in the TE mode may occur. To prevent this resonance, in the rotary joint 1 of this embodiment, a plurality of foam materials as dielectrics are arranged in the inner coaxial path 95 and the outer coaxial path 96. Since the dielectric constant of the foam material (the overall dielectric constant including the air in the cellular portion) is different from the dielectric constant of air, the electrical length can be adjusted by arranging the foam material. Therefore, the TE 11 This can prevent the occurrence of mode resonance.

[0033] Since the electrical length can be adjusted by using a material with a different dielectric constant than air, resonance can be prevented even when a dielectric other than foam is used. However, when using a material with a higher dielectric constant than air, a slight difference in length significantly changes the electrical length, so high precision is required for the shape of the dielectric. In contrast, the dielectric constant of foam varies depending on the material and foaming degree, but is, for example, 1.05 to 1.2, which is slightly higher than the dielectric constant of air. Therefore, resonance can be prevented without high precision in the shape. Therefore, it is preferable to use a foam with a low dielectric constant.

[0034] In the following, the placement of the foam materials will be described by referring to the foam material placed in the inner coaxial path 95 as inner foam material 81 and the foam material placed in the outer coaxial path 96 as outer foam material 82. Note that the amount of change in electrical length is the same regardless of the position of the foam material on the path, so it may be placed in a position different from the positions described below.

[0035] The inner foam material 81 is disposed at one end of the first tubular conductor 41 (the end connected to the second tubular conductor 45), and is also disposed at both ends of the second tubular conductor 45. The outer foam material 82 is disposed at one end of the tubular conductor 51 (the end on the second waveguide member 12 side), and is also disposed at a position of the tubular conductor 51 where it contacts the inner expanded diameter portion 46. Generally, foam materials are easily deformable, so by forcing the inner foam material 81 into the inner coaxial path 95, the inner foam material 81 takes on the same annular shape as the inner coaxial path 95 (the same applies to the outer foam material 82).

[0036] Next, the effects achieved by the connection structure of the conductors (particularly the inner tube conductor 40) of the rotary joint 1 of this embodiment will be described with reference to Figures 4 and 5. Figure 4 is a diagram illustrating the rotation angle of the rotary joint 1. Figure 5 is a graph comparing the reflection coefficient (S11 characteristics) as a function of the rotation angle of the rotary joint between a conventional example and this embodiment.

[0037] As described above, the second waveguide member 12 and the connecting portion 13 can be rotated relative to the first waveguide member 11. As shown in FIG. 4, the angle of rotation at this time is referred to as the rotation angle θ. In a conventional rotary joint (with an undivided inner conductor, etc.), the end of the inner conductor is configured as a choke so that it does not come into contact with the wall surface. 11 This makes it impossible to realize a mode filter, and the rotation can cause uneven reflection of radio waves, resulting in radio wave disturbance.

[0038] FIG. 5 shows the results of a simulation comparing the reflection coefficients (S11 characteristics) of a conventional rotary joint and the rotary joint 1 of this embodiment when the rotation angle θ is 0° and 90° for three frequencies A, B, and C between 9 GHz and 10 GHz. As shown in FIG. 5, it can be seen that in the conventional rotary joint, the reflection coefficient decreases as the rotation angle θ is changed. In contrast, in the rotary joint 1 of this embodiment, the reflection coefficient remains almost unchanged even when the rotation angle θ is changed. Furthermore, even when comparing the reflection coefficient values, the rotary joint 1 of this embodiment often exhibits a reflection coefficient that is superior to that of the conventional rotary joint. As described above, the rotary joint 1 of this embodiment has stable characteristics regardless of the rotation angle θ.

[0039] As described above, the rotary joint 1 of this embodiment includes a first waveguide 11, a second waveguide 12, a center conductor 30, an inner tube conductor 40, and an outer tube conductor 50. The first waveguide 11 is formed with a first waveguide path 91 and a second waveguide path 92. The second waveguide 12 is rotatable relative to the first waveguide 11, and is formed with a third waveguide path 93 and a fourth waveguide path 94. The inner tube conductor 40 is disposed so as to cover the outside of the center conductor 30, and together with the center conductor 30, forms an inner coaxial path 95 that connects the first waveguide path 91 and the third waveguide path 93. The inner tube conductor 40 is composed of two or more tube conductors (the first tube conductor 41 and the second tube conductor 45) that are aligned longitudinally, rotatably connected, and insulated. The outer conductor 50 is disposed so as to cover the outside of the inner conductor 40 , and together with the inner conductor 40 forms an outer coaxial path 96 that connects the second waveguide path 92 and the fourth waveguide path 94 .

[0040] This makes it possible to suppress the disturbance of radio waves at certain frequencies caused by uneven reflection of radio waves due to rotation, and also to improve TE 11 A rotary joint 1 having the above mode filter can be realized.

[0041] In addition, in the rotary joint 1 of this embodiment, the central conductor 30 is composed of two or more rod-shaped conductors (a first rod-shaped conductor 31 and a second rod-shaped conductor 35) that are aligned in the longitudinal direction, rotatably connected, and insulated.

[0042] As a result, the above-described effects can be achieved even in a rotary joint 1 configured to rotate the central conductor 30 as in this embodiment.

[0043] In addition, in the rotary joint 1 of this embodiment, a dielectric is disposed between the center conductor 30 and the inner tubular conductor 40 and / or between the inner tubular conductor 40 and the outer tubular conductor 50 (more specifically, both).

[0044] This allows the electrical lengths of the inner coaxial path 95 and the outer coaxial path 96 to be adjusted, thereby preventing resonance.

[0045] In rotary joint 1 of this embodiment, the dielectric material is foam material (inner foam material 81 and outer foam material 82).

[0046] As a result, since the dielectric constant of the foam material is close to that of air, resonance can be prevented without increasing the precision of the shape of the foam material.

[0047] In the rotary joint 1 of this embodiment, the inner conductor 40 is composed of a first conductor 41 and a second conductor 45 that are arranged side by side in the longitudinal direction and are insulated from each other. The first conductor 41 has an inner cylindrical portion 42 that protrudes toward the second conductor 45 at the end connected to the second conductor 45. The second conductor 45 has an inner annular groove 47 formed at the end connected to the first conductor 41, into which the inner cylindrical portion 42 of the first conductor 41 is inserted.

[0048] This allows the inner tube conductor 40 to be configured with a simple structure.

[0049] Furthermore, in the rotary joint 1 of this embodiment, the central conductor 30 is composed of a first rod-shaped conductor 31 and a second rod-shaped conductor 35 that are arranged side by side in the longitudinal direction and are insulated from each other. The first rod-shaped conductor 31 has a cylindrical portion 32 that protrudes toward the second rod-shaped conductor 35 at the end connected to the second rod-shaped conductor 35. The second rod-shaped conductor 35 has a circular hole 36 formed at the end connected to the first rod-shaped conductor 31, into which the cylindrical portion 32 of the first rod-shaped conductor 31 is inserted.

[0050] This allows the central conductor 30 to be configured with a simple structure.

[0051] The preferred embodiment of the present invention has been described above, but the above configuration can be modified, for example, as follows.

[0052] In the above embodiment, the directions of the first waveguide path 91 to the fourth waveguide path 94 are all parallel to each other, but for example, the directions of the first waveguide path 91 and the second waveguide path 92 and the directions of the third waveguide path 93 and the fourth waveguide path 94 may be different (for example, perpendicular).

[0053] The connection structure of the central conductor 30 and the inner tube conductor 40 in this embodiment is an example, and other structures may be used. In this embodiment, the central conductor 30 and the inner tube conductor 40 are configured to include two conductors connected in the longitudinal direction, but more conductors may be connected in the longitudinal direction.

[0054] In this embodiment, the central conductor 30 is configured to rotate in conjunction with the rotation of the second waveguide member 12 (the connecting portion 13), but the central conductor 30 may not be configured to rotate. [Explanation of symbols]

[0055] 1 rotary joint 30 Center conductor 31 First rod-shaped conductor (rod-shaped conductor) 35 Second rod-shaped conductor (rod-shaped conductor) 40 Inner tube conductor 41 First pipe conductor 42 Inner cylindrical part (cylindrical part) 45 Second pipe conductor 46 Inner enlarged diameter section 47 Inner annular groove (annular groove) 50 outer tube conductor 81 Inner foam 82 outer foam 91 First waveguide path 92 Second waveguide path 93 Third waveguide 94 Fourth waveguide 95 inner coaxial path 96 Outer coaxial path

Claims

1. a first waveguide member in which a first waveguide path and a second waveguide path are formed; a second waveguide member that is rotatable relative to the first waveguide member and that has a third waveguide path and a fourth waveguide path formed therein; A center conductor; an inner tubular conductor arranged to cover the outside of the central conductor, forming an inner coaxial path together with the central conductor, connecting the first waveguide path and the third waveguide path, the inner tubular conductor being composed of two or more tubular conductors that are aligned in a longitudinal direction, rotatably connected, and insulated; an outer tubular conductor arranged to cover the outside of the inner tubular conductor and forming, together with the inner tubular conductor, an outer coaxial path connecting the second waveguide path and the fourth waveguide path; A rotary joint comprising:

2. 2. The rotary joint according to claim 1, A rotary joint characterized in that the central conductor is composed of two or more rod-shaped conductors that are aligned in the longitudinal direction, rotatably connected, and insulated.

3. 3. A rotary joint according to claim 1 or 2, A rotary joint characterized in that a dielectric is disposed at least either between the center conductor and the inner conductor or between the inner conductor and the outer conductor.

4. 4. The rotary joint according to claim 3, A rotary joint characterized in that the dielectric material is a foam material.

5. 3. A rotary joint according to claim 1 or 2, The inner conductor is composed of a first conductor and a second conductor that are arranged side by side in a longitudinal direction and are insulated from each other, the first tubular conductor has a cylindrical portion that protrudes toward the second tubular conductor at an end portion connected to the second tubular conductor, A rotary joint characterized in that the second pipe conductor has an annular groove formed at the end connected to the first pipe conductor, into which the cylindrical portion of the first pipe conductor is inserted.

6. 3. The rotary joint according to claim 2, the central conductor is composed of a first rod-shaped conductor and a second rod-shaped conductor that are arranged side by side in a longitudinal direction and are insulated from each other; the first rod-shaped conductor includes a cylindrical portion that protrudes toward the second rod-shaped conductor at an end portion connected to the second rod-shaped conductor, A rotary joint characterized in that the second rod-shaped conductor has a circular hole formed at the end connected to the first rod-shaped conductor, into which the cylindrical portion of the first rod-shaped conductor is inserted.

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