JP7625352B2 - Choke Structure - Google Patents

Description

This invention relates to a choke structure, and to a technology suitable for application to a two-channel waveguide rotary joint used, for example, to connect waveguides in satellite communication antennas and weather radars.

Conventionally, as a mechanism for connecting waveguides within equipment used, for example, in satellite communication antennas and weather radars, a waveguide two-channel rotary joint is known that includes a first waveguide having a circular or rectangular cross section and a hollow central partition area extending in a cylindrical shape, with a first propagation path on one side and a second propagation path on the other side arranged within a single tube, and a coaxial tube that extends perpendicularly to the first waveguide and is connected to the first waveguide and supported rotatably about the perpendicular axis, with first and second transmission lines in the coaxial line that are connected to the first and second propagation paths, respectively, at the perpendicular axis for mode conversion, and in the partition area of the first waveguide, a short-circuit plate that extends obliquely with multiple steps to partition it, a first transmission line of the coaxial tube that is connected to the short-circuit plate and connects to the first propagation path side, and a second transmission line of the coaxial tube that extends around the periphery of the first transmission line and connects to the second propagation path side (see Patent Document 1).

JP 2013-255200 A

However, in a composite coaxial structure that transmits two signals separately, it is necessary to ensure good isolation.

The purpose of this invention is to provide a choke structure that can realize a structure that ensures good isolation in a waveguide two-channel rotary joint and can solve problems that arise with the structure.

In order to solve the above problems, the choke structure according to the present invention is a choke structure in a waveguide two-channel rotary joint having a rotating waveguide section including a first waveguide and a second waveguide, a fixed body that rotatably supports the rotating waveguide section, and a fixed waveguide section including a third waveguide and a fourth waveguide, and further comprising a first choke section provided on the side of a communicating section between a hollow hole of the fixed body into which a coaxial tube of the rotating waveguide section is inserted and the fourth waveguide, and a second choke section provided on the side of a communicating section between the hollow hole and the third waveguide. The coaxial tube has a second choke section provided on the side of the first choke section, a partition member interposed between the first choke section and the second choke section and having an inner tube through hole through which the inner tube of the coaxial tube passes, and a bearing member housed inside the first choke section or the second choke section and supporting the inner tube of the coaxial tube so that it can rotate freely around its axis. The partition member has a through hole for draining liquid that connects the first choke section and the second choke section.

The choke structure according to the present invention may be such that the dimensions of each part of the first choke section and each part of the second choke section are different from each other so that the first choke section and the second choke section have similar electrical characteristics by absorbing the change in wavelength caused by the accommodation of the bearing member.

The choke structure according to the present invention may be configured so that the partition member has two to four through holes for draining liquid.

The choke structure of this invention has two choke sections, a first choke section and a second choke section, making it possible to realize a structure that reliably ensures sufficient isolation in a waveguide two-channel rotary joint.

The choke structure of the present invention also has a through hole for draining liquid that connects the first choke section and the second choke section to the partition member interposed between the first choke section and the second choke section, so that cleaning liquid that has entered the second choke section can be drained to the outside, solving problems that arise with a structure having two choke sections, a partition member, and a bearing member.

The choke structure of the present invention can improve isolation between channels in the same frequency band if the dimensions of each part of the first choke section and each part of the second choke section are made different from each other so that the change in wavelength caused by the housing of the bearing member is absorbed and the first choke section and the second choke section have similar electrical characteristics.

When the partition member is provided with multiple through holes for draining the liquid, the choke structure of this invention makes it possible to more easily and appropriately drain the cleaning liquid that has entered the second choke portion to the outside.

1 is a longitudinal sectional view showing a schematic internal structure of a waveguide two-channel rotary joint (particularly, a fixed waveguide portion) in an embodiment having a choke structure according to the present invention; FIG. FIG. 2 is an enlarged vertical cross-sectional view of a choke structure in the waveguide two-channel rotary joint of FIG. 1 . 13 is a vertical cross-sectional view of the fixed waveguide portion, illustrating a state in which cleaning liquid remains in the second choke portion (when no liquid drainage through-hole is provided in the partition member). FIG. FIG. 2 is a perspective view showing the structure of a partition member in the choke structure of the waveguide two-channel rotary joint of FIG. 1 . 11 is a vertical cross-sectional view of a fixed waveguide portion illustrating the discharge of cleaning liquid from within a second choke portion to the outside. FIG. 1 is a model of a waveguide two-channel rotary joint 1 used in a simulation in a verification example, and is a simulation model for a case in which a through hole for liquid drainage is not provided in a partition member. 1 is a model of a waveguide two-channel rotary joint 1 used in a simulation in a verification example, and is an example of a simulation model in which two liquid drainage through holes are provided in a partition member. 11 is a graph showing a comparison of S parameter S11 (return loss) for cases in which a partition member has a through hole for liquid drainage and for cases in which the through hole has a different shape. 13 is a graph showing a comparison of S parameter S33 (return loss) for cases in which a partition member has a through hole for liquid drainage and for cases in which the through hole has a different shape. 11 is a graph showing a comparison of S parameter S21 (insertion loss) for cases in which a partition member has a through hole for liquid drainage and for cases in which the through hole has a different shape. 11 is a graph showing a comparison of S parameter S43 (insertion loss) for cases in which a partition member has a through hole for liquid drainage and for cases in which the through hole has a different shape. 11 is a graph showing a comparison of S parameter S13 (isolation) for cases in which a partition member has a through hole for liquid drainage and for cases in which the through hole has a different shape. 13 is a graph showing a comparison of S parameter S14 (isolation) for cases in which a partition member has a through hole for liquid drainage and for cases in which the through hole has a different shape. 13 is a graph showing a comparison of S parameter S23 (isolation) for cases in which a partition member has a through hole for liquid drainage and for cases in which the through hole has a different shape. 13 is a graph showing a comparison of S parameter S24 (isolation) for cases in which a partition member has a through hole for liquid drainage and for cases in which the through hole has a different shape.

The present invention will be described below based on the illustrated embodiment. In the following description, as shown in the figure, a vertical axis and a horizontal axis that are mutually perpendicular to the waveguide two-channel rotary joint 1 are defined, and the vertical axis direction corresponds to top and bottom, while the horizontal axis direction corresponds to right and left.

Figure 1 is a vertical cross-sectional view showing the schematic internal structure of a two-channel waveguide rotary joint 1 (particularly, a fixed waveguide section 10) having a choke structure 30 according to an embodiment of the present invention. Figure 2 is an enlarged vertical cross-sectional view of the choke structure 30 in the two-channel waveguide rotary joint 1.

This waveguide two-channel rotary joint 1 has a function of mode conversion from the TE mode (Transverse Electric mode), which is the fundamental transmission mode of a hollow rectangular waveguide with a rectangular cross section, to the TEM mode (Transverse Electromagnetic mode) of a rotatable coaxial line, and mainly has a fixed waveguide section 10 that is fixed and installed on a rotating table of a weather radar, for example, and a rotating waveguide section that is supported rotatably on the upper part of this fixed waveguide section 10.

This invention relates to the fixed waveguide section 10, and the structure of the rotating waveguide section is not limited to a specific form as long as it has a coaxial tube 23 that is inserted into the fixed waveguide section 10. Therefore, a detailed explanation of the structure of the rotating waveguide section will be omitted here.

The rotating waveguide section is generally considered to have, for example, a first waveguide 21 that is fixed to a rotating body that is rotatably supported on the upper part of the fixed waveguide section 10 and is a port that outputs a vertically polarized wave (CH2), a second waveguide 22 that is fixed to the rotating body and is a port that outputs a horizontally polarized wave (CH1), and a coaxial tube 23 that transmits the vertically polarized wave (CH2) to the first waveguide 21 and the horizontally polarized wave (CH1) to the second waveguide 22. As a specific structure of such a rotating waveguide section, for example, the structure disclosed in JP 2013-255200 A (including the structure disclosed as the background art and the structure disclosed as the mode for carrying out the invention) can be adopted.

The fixed waveguide section 10 has a fixed body 11 that is fixedly installed, for example, on a rotating base of a weather radar and rotatably supports the rotating waveguide section, a third waveguide 12 that is a port for inputting a vertically polarized wave (CH2) transmitted from the rotating base to a coaxial tube 23 disposed within the fixed body 11, and a fourth waveguide 13 that is a port for inputting a horizontally polarized wave (CH1).

The fixed body 11 is formed with an opening (reference numeral 111) at the upper end, and houses the coaxial tube 23 extending downward from the rotary waveguide section and arranged along the vertical direction, and has a hollow hole 112 communicating with the third waveguide 12 and the fourth waveguide 13. A rotating member (not shown) such as a bearing is attached to the fixed body 11 at a position near the upper end, and the rotary waveguide section is rotatably supported via this rotating member (for example, see JP 2013-255 A mentioned above).
(See the structure disclosed in Publication No. 200).

The first to fourth waveguides 21, 22, 12, and 13 are each a TE mode waveguide, which is the fundamental transmission mode of a hollow rectangular waveguide having a rectangular cross section, and communicate with a TEM mode coaxial tube 23 of a rotatable coaxial line that extends into the hollow hole 112 of the fixed body 11.

The coaxial tube 23 has a composite coaxial structure that transmits two polarized waves separately, and is a two-channel coaxial tube in which two transmission lines are formed, using the TEM mode of a rotatable coaxial line, and is housed in the hollow hole 112 of the fixed body 11.

The coaxial tube 23 has a long inner tube 231 that extends in an elongated cylindrical shape so as to cover the periphery of the rod-shaped central conductor 24, and a short cylindrical outer tube 232 that covers the outside of the upper end portion of the inner tube 231. Note that the coaxial tube 23 and the central conductor 24 are not shown in Figures 2, 3, and 5.

The coaxial tube 23 also includes a first transmission line 233 formed between the center conductor 24 and the inner tube 231 to transmit a vertically polarized wave (CH2), and a second transmission line 234 formed between the inner tube 231 and the outer tube 232 to transmit a horizontally polarized wave (CH1).

In the coaxial tube 23, the upper end of the first transmission line 233 communicates with the first waveguide 21 of the rotating waveguide section, and the lower end of the first transmission line 233 communicates with the third waveguide 12, and the upper end of the second transmission line 234 communicates with the second waveguide 22 of the rotating waveguide section, and the lower end of the second transmission line 234 communicates with the fourth waveguide 13 through the hollow hole 112 of the fixed body 11. That is, the first waveguide 21 and the third waveguide 12 communicate with each other through the inner tube 231 of the coaxial tube 23 (i.e., the first transmission line 233), and the second waveguide 22 and the fourth waveguide 13 communicate with each other through the outer tube 232 of the coaxial tube 23 (i.e., the second transmission line 234).

Here, in order to ensure sufficient isolation between the vertically polarized wave (CH2) input and transmitted from the third waveguide 12 and the horizontally polarized wave (CH1) input and transmitted from the fourth waveguide 13, i.e., isolation between channels, a choke structure 30 is provided between the communication part between the coaxial tube 23 and the third waveguide 12 and the communication part between the coaxial tube 23 and the fourth waveguide 13.

The choke structure 30 has two choke sections, a first choke section 31 provided on the side (i.e., the upper side) of the communication section (called the "first communication section 131") between the hollow hole 112 of the fixed body 11 and the fourth waveguide 13, and a second choke section 32 provided on the side (i.e., the lower side) of the communication section (called the "second communication section 121") between the hollow hole 112 of the fixed body 11 and the third waveguide 12, in order to reliably ensure sufficient isolation between the channels. The first choke section 31 and the second choke section 32 are provided between the first communication section 131 and the second communication section 121 as hollow spaces that communicate with the hollow hole 112 of the fixed body 11.

For ease of molding and assembly, the fixed waveguide section 10 is constructed by combining multiple pieces, and in relation to the choke structure 30, the side on which the first choke section 31 is provided and the side on which the second choke section 32 is provided are each formed as separate pieces (the symbol BS in Figures 1, 3, and 5 indicates the joint surface between the pieces).

The choke structure 30 according to the embodiment is a choke structure in a waveguide two-channel rotary joint 1 having a rotating waveguide section including a first waveguide 21 and a second waveguide 22, a fixed body 11 that rotatably supports the rotating waveguide section, and a fixed waveguide section 10 including a third waveguide 12 and a fourth waveguide 13. The choke structure 30 includes a first choke section 31 provided on the side of a communication section between a hollow hole 112 of the fixed body 11 into which a coaxial tube 23 of the rotating waveguide section is inserted and the fourth waveguide 13, and a second choke section 32 provided on the side of a communication section between the hollow hole 112 of the fixed body 11 and the third waveguide 12. The coaxial tube 23 includes a second choke portion 32 provided on the side of the communication portion with the waveguide 12, a partition member 33 interposed between the first choke portion 31 and the second choke portion 32 and having an inner tube through hole 331 through which the inner tube 231 of the coaxial tube 23 passes, and a bearing member 34 housed inside the second choke portion 32 and supporting the inner tube 231 of the coaxial tube 23 so as to be freely rotatable about its axis, and a liquid drain through hole 332 is provided around the inner tube through hole 331 of the partition member 33, connecting the first choke portion 31 and the second choke portion 32.

The first choke portion 31 is provided as a hollow space having a first choke portion space 311 and a first choke groove 312, and the second choke portion 32 is provided as a hollow space having a second choke portion space 321 and a second choke groove 322.

A first choke space 311 is formed on the side of the first communication portion 131 in the fixed body 11 as a hollow space that is circular in plan view and has a predetermined height, in other words, as a cylindrical hollow space.

The first choke groove 312 is formed as an annular groove that is recessed upward from the periphery of the upper surface/top surface of the first choke space 311 and is therefore open on the bottom surface.

A second choke space 321 is formed on the side of the second communication portion 121 in the fixed body 11 as a hollow space that is circular in plan view and has a predetermined height, in other words, as a cylindrical hollow space.

The second choke groove 322 is formed as an annular groove that is recessed downward from the peripheral edge of the lower surface/bottom surface of the second choke space 321 and is therefore open at the top.

The bearing member 34 is a member that supports the inner tube 231 of the coaxial tube 23 so that the inner tube 231 can rotate freely about its axis. The bearing member 34 has a disk-shaped base, a through hole 341 in the center in a plan view for passing the inner tube 231 of the coaxial tube 23 through, and an annular protrusion that protrudes downward from the peripheral portion of the lower surface/bottom surface.

The bearing member 34 is housed in the second choke portion 32 with the downward annular protrusion inserted into the second choke groove 322.

The material of the bearing member 34 is not limited to a specific type, but examples include polytetrafluoroethylene (PTFE).

Here, by accommodating the bearing member 34 in the second choke section 32, a change in wavelength occurs in the second choke section 32 due to the difference in dielectric constant between the material constituting the bearing member 34 and the metal material constituting the fixed waveguide section 10. For example, if the bearing member 34 is made of a material (specifically, for example, polytetrafluoroethylene (PTFE)) with a higher dielectric constant than the metal material constituting the fixed waveguide section 10, accommodating the bearing member 34 in the second choke section 32 causes a wavelength shortening in the second choke section 32.

Therefore, in order to ensure good isolation between channels in the same frequency band, first choke portion 31 and second choke portion 32 are provided as hollow spaces having different sizes (i.e., the dimensions of each portion of choke portion spaces 311, 321 and choke grooves 312, 322). That is, the dimensions of the choke structures of first choke portion 31 and second choke portion 32 are adjusted and set to each other so that the change in wavelength caused by accommodating bearing member 34 is absorbed and first choke portion 31 and second choke portion 32 have similar electrical characteristics, thereby improving isolation between channels in the same frequency band.

The partition member 33 is interposed between the first choke portion 31 and the second choke portion 32, and separates the first choke portion space 311 from the second choke portion space 321.

The partition member 33 has a disk-shaped base and has an inner tube through hole 331 in the center in a plan view for passing the inner tube 231 of the coaxial tube 23 through it.

Here, when assembling the fixed waveguide section 10, multiple pieces are combined and soldered to the joint surfaces BS between the pieces to ensure airtightness. In order to remove the flux after soldering, it is practically impossible to wipe it off using, for example, alcohol-soaked absorbent cotton and tweezers, since the mechanical structure of the assembled fixed waveguide section 10 is complex, and it is necessary to dissolve the assembled fixed waveguide section 10 by immersing it in a specified cleaning solution.

When the flux is dissolved by immersion in a cleaning solution, the flux will not dissolve unless it is immersed in the cleaning solution at a high temperature, so the assembled fixed waveguide section 10 is immersed in the cleaning solution at a high temperature. In this case, the temperature of the assembled fixed waveguide section 10 drops rapidly when immersed in the cleaning solution, so the cleaning solution that has penetrated into the hollow hole 112 of the fixed body 11 enters the second choke section 32 from the boundary between the bearing member 34 and the surrounding metal material (specifically, the second choke section 32). On the other hand, even if the assembled fixed waveguide section 10 is taken out of the cleaning solution after a predetermined time of immersion, the cleaning solution is not discharged from the boundary between the bearing member 34 and the surrounding metal material, and the cleaning solution remains in the second choke section 32 (see FIG. 3).

Therefore, two liquid drainage through holes 332 are provided in the partition member 33 at positions around the inner tube through hole 331 that overlap at least partially with the second choke portion 32 in a plan view (in other words, in the vertical direction) (see Figures 1, 2, and 4). Note that the number of liquid drainage through holes 332 provided in the partition member 33 is not limited to two, and may be one, or may be three or more.

The liquid drainage through hole 332 is provided to connect the first choke portion 31 and the second choke portion 32, and further to connect the hollow hole 112 of the fixed body 11 and the second choke portion 32.

As a result, the cleaning liquid that has entered the second choke section 32 passes through the liquid drainage through hole 332 of the partition member 33, the first choke section 31, and the hollow hole 112 of the fixed body 11, and is discharged to the outside through the opening 111 at the upper end of the fixed waveguide section 10 (see Figure 5).

To allow the cleaning liquid that has entered the second choke portion 32 to be more easily and appropriately discharged to the outside, it is preferable that multiple drainage through holes 332 be provided in the partition member 33. Furthermore, in order to appropriately control the effect on the electrical characteristics of the rotary joint, it is preferable that about two to four drainage through holes 332 be provided in the partition member 33.

According to the choke structure 30 of the embodiment, since it has two choke portions, the first choke portion 31 and the second choke portion 32, it is possible to realize a structure that reliably ensures sufficient isolation in a waveguide two-channel rotary joint.

According to the choke structure 30 of the embodiment, the partition member 33 interposed between the first choke portion 31 and the second choke portion 32 is provided with a liquid drainage through hole 332 that connects the first choke portion 31 and the second choke portion 32. This allows the cleaning liquid that has entered the second choke portion 32 to be discharged to the outside of the fixed waveguide portion 10, thereby solving problems that arise with a structure having two choke portions 31 and 32, the partition member 33, and the bearing member 34.

In addition, according to the choke structure 30 of the embodiment, the dimensions of each part of the first choke part 31 and each part of the second choke part 32 are made different from each other so that the change in wavelength caused by the accommodation of the bearing member 34 is absorbed and the first choke part 31 and the second choke part 32 have similar electrical characteristics, so that it is possible to improve the isolation between channels in the same frequency band.

In addition, according to the embodiment of the choke structure 30, the partition member 33 is provided with a plurality of through holes 332 for draining liquid, so that the cleaning liquid that has entered the second choke portion 32 can be more easily and appropriately discharged to the outside.

A verification example of the choke structure according to the present invention is described below with reference to Figures 8 to 15.

In this verification example, a simulation was performed using a model of the waveguide two-channel rotary joint 1 to determine the S-parameters, thereby understanding and verifying the effect on the electrical characteristics of the rotary joint due to the provision of the liquid drainage through-hole 332 in the partition member 33.

The model of the waveguide two-channel rotary joint 1 used in the simulation of this verification example is shown in Figures 6 and 7. Figure 6 is a simulation model in which the partition member 33 is not provided with a through hole 332 for liquid drainage. Figure 7 is an example of a simulation model in which the partition member 33 is provided with a through hole 332 for liquid drainage, specifically, an example of a simulation model in which two through holes 332 for liquid drainage are provided.

In this verification example, the ports 1 to 4 in the simulation were associated with the first to fourth waveguides 21, 22, 12, and 13, respectively, as follows:
Port 1: second waveguide 22 (port that outputs horizontally polarized wave (CH1))
Port 2: Fourth waveguide 13 (port for inputting horizontally polarized wave (CH1))
Port 3: First waveguide 21 (port for outputting vertically polarized wave (CH2))
Port 4: Third waveguide 12 (port for inputting vertically polarized wave (CH2))

In this verification example, in order to understand and verify the effect on the electrical characteristics of the rotary joint due to the provision of the liquid drainage through holes 332 in the partition member 33, the S parameters were compared for the cases where the liquid drainage through holes 332 were provided and where they were not provided. In addition, in order to understand and verify the effect of differences in the number and diameter of the liquid drainage through holes 332, cases (called "shape cases") were set for the provision of the liquid drainage through holes 332, with two holes at diameters of φ2 mm, φ3 mm, φ4 mm, φ5 mm, φ6 mm, and φ7 mm, and with four holes at diameters of φ7 mm.

Figure 8 shows the results of a comparison of S-parameter S11 (i.e., return loss) for cases with and without the liquid drainage through-hole 332 in the partition member 33 and for different shapes of the liquid drainage through-hole 332, and Figure 9 shows the results of a comparison of S-parameter S33 (i.e., return loss).

From the results shown in Figures 8 and 9, it was confirmed that the presence or absence of the liquid drainage through-holes 332 does not significantly change the behavior or degree of the return loss by frequency. From the results shown in Figures 8 and 9, it was also confirmed that the number and diameter of the liquid drainage through-holes 332 do not significantly change the behavior or degree of the return loss by frequency, at least within the range of the shape cases set in this verification example. In both cases, the return loss standard is met in a specified frequency band (approximately 9 to 10 GHz) including the center frequency of 9.5 GHz specified in the simulation here.

The results of a comparison of S-parameter S21 (i.e., insertion loss) for the presence or absence of the liquid drainage through-hole 332 in the partition member 33 and for the shape of the liquid drainage through-hole 332 are shown in FIG. 10, and the results of a comparison of S-parameter S43 (i.e., insertion loss) are shown in FIG. 11. Note that, for the comparison of S-parameters S21 and S43, no four shape cases with a diameter of φ7 mm were set for the way in which the liquid drainage through-hole 332 is provided.

From the results shown in Figures 10 and 11, it was confirmed that the presence or absence of the liquid drainage through-holes 332 does not significantly affect the behavior or degree of the insertion loss by frequency. From the results shown in Figures 10 and 11, it was also confirmed that the number and diameter of the liquid drainage through-holes 332 do not significantly affect the behavior or degree of the insertion loss by frequency, at least within the range of the shape cases set in this verification example. In either case, the insertion loss standard is met in a specified frequency band (approximately 9 to 10 GHz) that includes the center frequency of 9.5 GHz in the specifications in the simulation here.

The results of a comparison of S-parameter S13 (i.e., isolation) for the presence or absence of the through-hole 332 for draining liquid in the partition member 33 and for the shape of the through-hole 332 for draining liquid are shown in FIG. 12, the results of a comparison of S-parameter S14 (i.e., isolation) are shown in FIG. 13, the results of a comparison of S-parameter S23 (i.e., isolation) are shown in FIG. 14, and the results of a comparison of S-parameter S24 (i.e., isolation) are shown in FIG. 15.

The results shown in Figures 12 to 15 confirm that the isolation standards are met in all cases, at least within the range of shape cases set in this verification example.

The results of the above verification example confirmed that even if an inner tube through hole 331 is provided in the partition member 33, which is interposed between the first choke portion 31 and the second choke portion 32 and separates the first choke portion space 311 and the second choke portion space 321, there is no significant effect on the electrical characteristics of the rotary joint, and that performance that satisfies the isolation standards can be achieved.

The above describes an embodiment of the present invention, but the specific configuration is not limited to the above embodiment, and even if there are design changes within the scope of the invention that do not deviate from the gist of the invention, they are still included in the invention.

Specifically, in the above embodiment, the choke structure according to the present invention is applied to a two-channel waveguide rotary joint 1 whose schematic structure is shown in FIG. 1, but the structure of the two-channel waveguide rotary joint to which the choke structure according to the present invention can be applied is not limited to the two-channel waveguide rotary joint 1 whose schematic structure is shown in FIG. 1, and the choke structure according to the present invention may be applied to a two-channel waveguide rotary joint of another structure.

Furthermore, although in the above embodiment, bearing member 34 is accommodated in second choke portion 32, bearing member 34 may be accommodated in first choke portion 31. In this case, cleaning liquid remains in first choke portion 31, and cleaning liquid that has entered first choke portion 31 passes through liquid drainage through hole 332 of partition member 33, second choke portion 32, and hollow hole 112 of fixed body 11, and is discharged to the outside from opening 111 at the upper end of fixed waveguide portion 10.

LIST OF SYMBOLS 1 Waveguide two-channel rotary joint 10 Fixed waveguide section 11 Fixed body 111 Opening 112 Hollow hole 12 Third waveguide 121 Second communication section 13 Fourth waveguide 131 First communication section 21 First waveguide 22 Second waveguide 23 Coaxial tube 231 Inner tube 232 Outer tube 233 First transmission line 234 Second transmission line 24 Central conductor 30 Choke structure 31 First choke section 311 First choke section space 312 First choke groove 32 Second choke section 321 Second choke section space 322 Second choke groove 33 Partition member 331 Through hole for inner tube 332 Through hole for liquid drainage 34 Bearing member 341 Through hole BS Joint surface

Claims (3)

A choke structure in a waveguide two-channel rotary joint having a rotating waveguide section including a first waveguide and a second waveguide, a fixed body that rotatably supports the rotating waveguide section, and a fixed waveguide section that includes a third waveguide and a fourth waveguide,
a first choke portion provided on a side of a communication portion between a hollow hole of the fixed body into which a coaxial tube of the rotary waveguide portion is inserted and the fourth waveguide;
a second choke portion provided on a side of a communicating portion between the hollow hole and the third waveguide;
a partition member interposed between the first choke portion and the second choke portion and including an inner tube through hole through which an inner tube of the coaxial tube passes;
a bearing member that is accommodated in the first choke portion or the second choke portion and supports the inner tube of the coaxial tube so as to be rotatable about an axis thereof,
a through hole for draining liquid that communicates with the first choke portion and the second choke portion is provided around the through hole for the inner tube of the partition member;
A choke structure characterized by: the dimensions of each portion of the first choke portion and each portion of the second choke portion are different from each other so that the first choke portion and the second choke portion have similar electrical characteristics by absorbing a change in wavelength caused by accommodating the bearing member;
2. The choke structure according to claim 1 . The partition member has two to four liquid drainage through holes.
3. The choke structure according to claim 1 or 2.