JP4509956B2 - Rotary joint - Google Patents

Description

  The present invention relates to a rotary joint used for controlling rotation of an antenna.

  A rotary joint is usually used for the rotating part of the antenna device. In order to prevent characteristic deterioration due to rotation, in a conventional rotary joint, a circularly polarized wave converted by a rotationally symmetric mode such as a TEM mode, a TE01 mode, and a TM01 mode or a circularly polarized wave generator is used for a transmission wave. (For example, refer to Patent Documents 1 and 2).

Japanese Examined Patent Publication No. 56-51522 Japanese Utility Model Publication No. 1-53022

  However, the prior art has the following problems. Due to recent revisions to the Radio Law, there has been an increasing demand for unnecessary radiation suppression of antenna devices. In the conventional rotary joint, it is difficult to provide a filter function inside the rotary joint. Therefore, in order to meet such a demand, it is necessary to provide a filter separately from the rotary joint. Therefore, there are problems such as an increase in cost due to an increase in the number of parts and an enlargement of the structure.

  The present invention has been made to solve the above-described problems, and when it is necessary to suppress unnecessary waves of the antenna device, it is not necessary to install a filter, or even when a filter is used in combination. The object is to obtain a rotary joint that can be completed with a small filter with a simple structure.

A rotary joint according to the present invention includes an oversized circular waveguide having a rotation mechanism therein and a coaxial line constituting an input / output end. The coaxial line is interposed between the oversized circular waveguide. The coaxial line at the input end and the coaxial line at the output end are opposed to each other, and the inner conductors of the coaxial line at the input end and the coaxial line at the output end have a passband characteristic in which the stopband frequency is higher than the passband frequency. In the desired stopband, a length of about 1/4 wavelength of the higher-order mode of the coaxial line is extended into the oversized circular waveguide.

  According to the present invention, the inner conductor provided in the coaxial line is extended into the waveguide with a length of about ¼ wavelength of the higher-order mode of the coaxial line in the stop band of the pass characteristic, thereby functioning as a band stop filter. If it is necessary to suppress unwanted waves of the antenna device, it is possible to eliminate the need for a filter, or to use a small filter with a simple configuration even when using a filter. A rotary joint can be obtained.

  Hereinafter, preferred embodiments of the rotary joint of the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
1 is a cross-sectional view of a rotary joint according to Embodiment 1 of the present invention. The rotary joint shown in FIG. 1 includes coaxial lines 11a and 11b that are input / output terminals, oversized circular waveguides 12a and 12b, probes 13a and 13b, and a connecting portion 14. Further, the connecting portion 14 has a choke groove 14a and a bearing 14b. The rotary joint having such a configuration is rotatable via the connection portion 14.

  Here, each of the probes 13a and 13b, which are inner conductors of the coaxial lines 11a and 11b, has a configuration extending from the coaxial lines 11a and 11b into the oversized circular waveguides 12a and 12b as shown in FIG. is doing. Further, the lengths of the probes 13a and 13b are approximately ¼ wavelength of the coaxial line TM01 mode in a desired stop band.

  Next, the operation principle will be described. In the stop band, a part of the TEM mode of the radio wave incident on the coaxial line 11a as the input terminal in the TEM mode is coupled to the coaxial line TM01 mode at the tip of the probe 13a.

  When the input terminal side is viewed from the TM01 mode coaxial line, in the coaxial line TM01 mode, the coaxial line 13a that is the input terminal is cut off, so that most of the tip is electrically short-circuited by the outer conductor. It can be regarded as being in a state. From this, a series 1/4 wavelength tip short-circuit stub composed of TM01 mode is formed in the portions of the coaxial lines 13a and 13b extending into the oversized circular waveguides 12a and 12b. As a result, the anti-resonance of this series 1/4 wavelength tip short-circuited stub produces a band rejection characteristic, and the rotary joint can be operated as a band rejection filter.

  On the other hand, in the pass band, the radio wave incident on the coaxial line 11a as the input terminal in the TEM mode is coupled to the circular waveguide TM01 mode at the tip of the probe 13a and propagates through the oversized circular waveguides 12a and 12b. . Further, the radio wave propagated to the oversized circular waveguide 12b is coupled to the TEM mode again at the tip of the probe 13b, and is output in the TEM mode to the coaxial line 11b which is the output end. Here, the circular waveguide TM01 mode is an axially symmetric mode, and does not deteriorate the pass characteristic due to rotation in the connection portion 14, and thus operates as a rotary joint.

  This effect is shown by a numerical calculation example using the finite element method. FIG. 2 is a diagram showing the relationship between the reflection characteristics and the pass characteristics of the rotary joint according to Embodiment 1 of the present invention. The solid line indicates the pass characteristic (S21), and the dotted line indicates the reflection characteristic (S11). As shown in FIG. 2, the band rejection characteristic is observed in the vicinity of the frequency fc where the length of the probe is about ¼ wavelength of the TM01 mode of the coaxial line. From this, it can be seen that the rotary joint having the configuration of FIG. 1 operates as a band rejection filter.

  As described above, according to the first embodiment, the inner conductor provided in the coaxial line is extended into the waveguide with a length of approximately ¼ wavelength of the higher-order mode of the coaxial line in the stop band of the pass characteristic. By doing so, the rotary joint can be operated as a band rejection filter with a rotating function. Thereby, even when it is necessary to suppress unnecessary waves of the antenna device, it is not necessary to install a filter, and a rotary joint that can be reduced in cost and size by reducing the number of components can be realized.

Embodiment 2. FIG.
FIG. 3 is a cross-sectional view of the rotary joint according to the second embodiment of the present invention. The rotary joint in FIG. 3 includes coaxial lines 21 a and 21 b that are input / output terminals, oversized circular waveguides 22 a and 22 b, probes 23 a and 23 b, and a connection portion 24. Further, the connecting portion 24 has a choke groove 24a and a bearing 24b. The rotary joint having such a configuration can be rotated via the connecting portion 24.

  Here, the probes 23a and 23b, which are the inner conductors of the coaxial lines 21a and 21b, have a configuration extending from the coaxial lines 21a and 21b into the oversized circular waveguides 22a and 22b, respectively, as shown in FIG. is doing. Further, the lengths of the probes 23a and 23b are approximately ¼ wavelength of the coaxial line TM01 mode in a desired stop band.

  Further, as shown in FIG. 3, the rotary joint in the second embodiment is further provided with steps 25a and 25b on the discontinuous surfaces of the coaxial lines 21a and 21b and the oversized circular waveguides 22a and 22b. It is a feature.

  The rotary joint according to the second embodiment has the same structure as the rotary joint according to the first embodiment except that the steps 25a and 25b are included. Acts as a filter.

  Furthermore, the rotary joint according to the second embodiment has steps 25a and 25b to reduce the amount of change in impedance at the connection surface between the coaxial lines 21a and 21b and the oversized circular waveguides 22a and 22b. Thus, the reflection characteristics of the band rejection filter can be improved.

  As described above, according to the second embodiment, by providing a step shape on the connection surface (discontinuous surface) of the input / output coaxial line and the oversized circular waveguide, the rotary joint can be mounted in a state having a rotation function. While being able to operate as a band rejection filter, it is possible to improve the reflection characteristics of the band rejection filter. Thereby, even when it is necessary to suppress unnecessary waves of the antenna device, it is not necessary to install a filter, and a rotary joint that can be reduced in cost and size by reducing the number of components can be realized.

  In the above description, the case where the step shape is provided on the discontinuous surface connecting the input / output coaxial line and the oversized circular waveguide has been described. However, the amount of change in impedance can be reduced by using the tapered shape. Such a shape can also improve the reflection characteristics.

Embodiment 3 FIG.
FIG. 4 is a cross-sectional view of the rotary joint according to Embodiment 3 of the present invention. The rotary joint shown in FIG. 4 includes coaxial lines 31a and 31b, which are input / output terminals, an oversized circular waveguide 32, probes 33a and 33b, and a connection portion 34. Further, the connecting portion 34 has a choke groove 34a and a bearing 34b. The rotary joint having such a configuration can be rotated via the connecting portion 34.

  Here, each of the probes 33a and 33b, which are inner conductors of the coaxial lines 31a and 31b, has a configuration extending from the coaxial lines 31a and 31b into the oversized circular waveguide 32 as shown in FIG. Yes. Further, the lengths of the probes 33a and 33b are approximately ¼ wavelength of the coaxial line TM01 mode in a desired stop band.

  The rotary joint according to the third embodiment is characterized in that at least one or more grooves 35 having a length of approximately ¼ wavelength at a desired frequency are provided on the tube wall of the oversized circular waveguide 32. It is said.

  The rotary joint shown in the third embodiment basically has the same structure as the rotary joint in the first embodiment, and operates as a band rejection filter as in the first embodiment.

  Furthermore, the rotary joint according to the third embodiment has the groove 35 on the tube wall of the oversized circular waveguide 32, so that the depth of the groove 35 is set to ¼ wavelength in a desired band, for example. In this case, near the entrance of the groove 35, it looks like a magnetic wall in a pseudo manner, and thus acts as a stop band in that band. As a result, the stop band can be increased.

  As described above, according to the third embodiment, by providing a groove on the tube wall of the oversized circular waveguide, the rotary joint can be operated as a band rejection filter with a rotation function. Compared with the rotary joint in the first embodiment, the stop band can be increased. Thereby, when it is necessary to suppress unnecessary waves in a plurality of frequency bands, it is possible to realize a rotary joint that can further reduce the number of parts and cost.

Embodiment 4 FIG.
FIG. 5 is a cross-sectional view of a rotary joint according to Embodiment 4 of the present invention. The rotary joint in FIG. 5 includes coaxial lines 41 a and 41 b that are input / output terminals, an oversized circular waveguide 42, probes 43 a and 43 b, and a connection portion 44. Further, the connecting portion 44 has a choke groove 44a and a bearing 44b. The rotary joint having such a configuration can be rotated via the connecting portion 44.

  Here, each of the probes 43a and 43b, which are inner conductors of the coaxial lines 41a and 41b, has a configuration extending from the coaxial lines 41a and 41b into the oversized circular waveguide 42 as shown in FIG. Yes. Further, the lengths of the probes 43a and 43b are approximately ¼ wavelength of the coaxial line TM01 mode in a desired stop band.

  The rotary joint according to the fourth embodiment is characterized in that at least one or more protrusions 45 are provided on the circumference of the oversized circular waveguide 42 toward the inside of the oversized circular waveguide 42. It is said.

  The rotary joint shown in the fourth embodiment basically has the same structure as the rotary joint in the first embodiment, and operates as a band rejection filter as in the first embodiment.

  Further, the rotary joint according to the fourth embodiment has a protrusion 45 protruding into the oversized circular waveguide 32, and this protrusion has a corrugated structure. Therefore, the desired corrugated structure in the waveguide has a filter characteristic such as a low-pass type.

  As described above, according to the fourth embodiment, by providing a protrusion inside the oversized circular waveguide, the rotary joint can be operated as a band rejection filter with a rotation function. Compared with the rotary joint in the form 1, the stop band can be increased. Thereby, when it is necessary to suppress unnecessary waves in a plurality of frequency bands, it is possible to realize a rotary joint that can further reduce the number of parts and cost.

Embodiment 5 FIG.
FIG. 6 is a cross-sectional view of the rotary joint according to the fifth embodiment of the present invention. The rotary joint shown in FIG. 6 includes coaxial lines 51a and 51b, which are input / output terminals, an oversized circular waveguide 52, probes 53a and 53b, and a connection portion 54. Further, the connecting portion 54 has a choke groove 54a and a bearing 54b. The rotary joint having such a configuration is rotatable via the connection portion 54.

  Here, each of the probes 53a and 53b, which are inner conductors of the coaxial lines 51a and 51b, has a configuration extending from the coaxial lines 51a and 51b into the oversized circular waveguide 52 as shown in FIG. Yes. Further, the lengths of the probes 53a and 53b are approximately ¼ wavelength of the coaxial line TM01 mode in a desired stop band.

  In addition, the rotary joint according to the fifth embodiment is characterized in that the thickness of the probes 53a and 53b becomes thinner toward the tip in the oversized circular waveguide 52, as shown in FIG. .

  The rotary joint shown in the fifth embodiment basically has the same structure as the rotary joint in the first embodiment, and operates as a band rejection filter as in the first embodiment.

  Further, the rotary joint according to the fifth embodiment is so thin that the probes 53a and 53b extended from the input / output coaxial lines 51a and 51b are directed toward the tip, so that the impedance of the coaxial line TM01 mode is increased. Therefore, the coupling from the TEM mode to the coaxial line TM01 mode, which is a factor of the stop characteristic, is increased, and a wide stop band can be realized.

  This effect is shown by a numerical calculation example using the finite element method. FIG. 7 is a diagram showing a comparison of pass characteristics due to differences in probe shape according to the fifth embodiment of the present invention. As shown in FIG. 6, the passage characteristics of a rotary joint in which the probes 53a and 53b are tapered are shown by solid lines. Further, as shown in FIG. 1, the passage characteristics of a rotary joint in which the probes 53a and 53b are linearly extended are indicated by broken lines.

  Comparing these two pass characteristics, by making the probes 53a and 53b taper, the stop band in the vicinity of the frequency fc where the length of the probes 53a and 53b is approximately ¼ wavelength of the TM01 mode of the coaxial line is obtained. You can see that it is spreading.

  As described above, according to the fifth embodiment, by reducing the probe shape into a tapered shape, the rotary joint can be operated as a band rejection filter with a rotation function, and the band rejection filter is blocked. The bandwidth can be increased. This makes it unnecessary to install a filter even when it is necessary to suppress unwanted waves from the antenna device, or even when using a filter, a small filter with a simple configuration can be used. A rotary joint that can be reduced in cost and size can be realized.

  In the above description, the effect when the shape of the probes 53a and 53b is tapered is shown. However, the same effect can be obtained when the probe 53a and 53b is tapered.

It is sectional drawing of the rotary joint in Embodiment 1 of this invention. It is a figure which shows the relationship between the reflection characteristic of the rotary joint in Embodiment 1 of this invention, and the frequency of a passage characteristic. It is sectional drawing of the rotary joint in Embodiment 2 of this invention. It is sectional drawing of the rotary joint in Embodiment 3 of this invention. It is sectional drawing of the rotary joint in Embodiment 4 of this invention. It is sectional drawing of the rotary joint in Embodiment 5 of this invention. It is the figure which showed the comparison of the passage characteristic by the difference in the probe shape in Embodiment 5 of this invention.

Explanation of symbols

  11a, 21a, 31a, 41a, 51a Input coaxial line, 11b, 21b, 31b, 41b, 51b Output coaxial line, 12a, 12b, 22a, 22b, 32, 42, 52 Oversized circular waveguide, 13a, 13b, 23a, 23b, 33a, 33b, 43a, 43b, 53a, 53b Probe (inner conductor), 14, 24, 34, 44, 54 Connection part, 14a, 24a, 34a, 44a, 54a Choke groove, 14b, 24b, 34b 44b, 54b Bearing, 25a, 25b Step, 35 Groove, 45 Protrusion.

Claims (5)

An oversized circular waveguide having a rotation mechanism inside;
In a rotary joint equipped with a coaxial line constituting the input / output end,
In the coaxial line, the coaxial line at the input end and the coaxial line at the output end are arranged to face each other via the oversized circular waveguide, and the inner conductors of the coaxial line at the input end and the coaxial line at the output end are arranged. Is a structure that extends into the oversized circular waveguide with a length of approximately ¼ wavelength of the higher-order mode of the coaxial line in a desired stopband with a passband frequency higher than that of the passband. A rotary joint characterized by having. The rotary joint according to claim 1,
The oversized circular waveguide and the coaxial line have a step shape or a tapered shape at a discontinuous surface between the oversized circular waveguide and the coaxial line. The rotary joint according to claim 1 or 2,
The oversized circular waveguide has at least one circumferential groove on an inner tube wall. The rotary joint according to claim 1 or 2,
The oversized circular waveguide has at least one circumferential protrusion on an inner tube wall. The rotary joint according to any one of claims 1 to 4,
In the coaxial line, the shape of the inner conductor of the coaxial line extended to the oversized circular waveguide is tapered or stepped.

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