SWIVEL CONNECTION

Abstract

The rotary joint comprises a stationary body (10) arranged along an arc centered on a central axis and comprising a first split waveguide (11) with a flat opening (11A) on a first side, a first waveguide (13) whose one end is connected to an end of the first split waveguide (11) via a first coupling section (12A), and a second waveguide (14) whose one end is connected to the other end of the first split waveguide (11) via a second coupling section (12B), and a rotating body (20) comprising an annular second split waveguide (21) arranged along a circumference having the same diameter as the arc in which the first split waveguide (11) is arranged around the central axis and a flat opening (21A) facing an opening of the first split waveguide (11), and a plurality of third waveguides (23A,23B) comprises, which are arranged at intervals from one another on a second side facing the first side of the second split waveguide (21), and each is coupled to the second split waveguide (21) via a directional coupler (22A, 22B), and is rotatable about the central axis with respect to the stationary body (10), wherein the second split waveguide (21) forms a waveguide with the first split waveguide (11) at a position where the openings (11A, 21A) face each other.

Description

FIELD OF TECHNOLOGY

[0001] The present disclosure relates to a rotary joint having a stationary body and a rotating body, which is used for transmitting electromagnetic waves. TECHNICAL BACKGROUND

[0002] In a microwave communication system, Non-Patent Literature 1 discloses a rotary joint that forms a connection between a fixed portion and a movable portion.

[0003] The rotary joint shown in Non-Patent Literature 1 consists of coaxially stacked waveguide rings of the same diameter arranged in three planes, with the center ring half in-plane. An upper half of the center ring is brazed to an output ring and a lower half to an input ring, and the power is transferred from the input ring to the output ring through the center ring. REFERENCE LISTS NON-PATENT LITERATURE

[0004] Non-patent literature 1: K. Rambabu and Jens Bornemann. “Compact Single-Channel Rotary Joint Using Ridged Waveguide Sections for Phase Adjustment,” IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 51, NO. 8, AUGUST. 2003, pp. 1982-1986 SUMMARY OF THE INVENTIONTECHNICAL PROBLEM

[0005] The rotary joint disclosed in Non-Patent Literature 1 performs energy transfer from the input ring to the output ring via a ring resonance mode of the center ring, and therefore the rotary joint operates only in a frequency range of the ring resonance of the center ring, has a narrow working band, and has a problem in band expansion.

[0006] The present disclosure solves the above problem, and an object of the present disclosure is to obtain a rotary joint having broadband transmission characteristics. SOLUTION TO THE PROBLEM

[0007] A rotary joint according to the present disclosure comprises: a stationary body having a first split waveguide arranged along an arc centered on a central axis and having an opening that is flat on a first side of the stationary body, a first waveguide having a first end connected to a first end of the first split waveguide via a first coupling portion, and a second waveguide having a first end connected to a second end of the first split waveguide via a second coupling portion; and a rotating body having a second split waveguide having an annular shape arranged along a circumference with the same diameter as the arc along which the first split waveguide is arranged around the central axis, and having an opening,which is flat on the first side of the rotating body and faces the opening of the first split waveguide, and comprises a plurality of third waveguides arranged at intervals from one another on a second side of the rotating body opposite the first side of the rotating body of the second split waveguide, each coupled to the second split waveguide via a directional coupler, and which is rotatable about the central axis with respect to the stationary body, in which the second split waveguide forms a waveguide with the first split waveguide at a position where the opening of the first split waveguide and the opening of the second split waveguide face each other. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0008] According to the present disclosure, a rotary joint has broadband transmission characteristics. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic perspective view showing a rotary joint according to a first embodiment. Fig. 2 is a cross-sectional view taken along line A11-A11 in Fig. 1 of a stationary body in the rotary joint according to the first embodiment. Fig. 3 is a cross-sectional view taken along line A12-A12 in Fig. 1 of the stationary body in the rotary joint according to the first embodiment. Fig. 4 is a cross-sectional view taken along line A13-A13 in Fig. 3 of the stationary body in the rotary joint according to the first embodiment. Fig. 5 is a cross-sectional view taken along line A21-A21 in Fig. 1 of a rotating body in the rotary joint according to the first embodiment. Fig. 6 is a cross-sectional view taken along line A22-A22 in Fig. 1 of the rotating body in the rotary joint according to the first embodiment. Fig. 7 is a cross-sectional view taken along line A23-A23 in Fig. 6 of the rotating body in the rotary joint according to the first embodiment. Fig. 8 is a diagram for explaining the operating principle of the rotary joint according to the first embodiment. Fig. 9 is a diagram for explaining a transmission path in Example 1 of a first position in the rotary joint according to the first embodiment. Fig. 10 is a diagram for explaining a transmission path in Example 1 of a second position in the rotary joint according to the first embodiment. Fig. 11 is a schematic perspective view showing a rotary joint according to a second embodiment. Fig. 12 is a cross-sectional view taken along line A21-A21 in Fig. 11 of the rotating body in the rotary joint according to the second embodiment. Fig. 13 is a cross-sectional view taken along line A23-A23 in Fig. 12 of the rotating body in the rotary joint according to the second embodiment. Fig. 14 is a diagram for explaining a transmission path in Example 1 of a first position in the rotary joint according to the second embodiment. Fig. 15 is a diagram for explaining a transmission path in Example 1 of a second position in the rotary joint according to the first embodiment. DESCRIPTION OF THE EMBODIMENTSFirst embodiment.

[0009] A rotary joint according to a first embodiment is described with reference to Fig. 1 to 10 described.

[0010] As in Fig. 1, the rotary joint according to the first embodiment comprises a stationary body 10 and a rotating body 20.

[0011] The stationary body 10 is an input-side transmission body that transmits a transmission signal from the transmission circuit 30.

[0012] The rotating body 20 is an output-side transmission body which receives the transmission signal transmitted from the stationary body 10 and transmits it to the receiving circuits 41 and 42.

[0013] The transmission signal is a signal of an electromagnetic wave through microwaves or light and is hereinafter referred to as the transmitted signal.

[0014] The rotating body 20 is arranged to face the stationary body 10 with a central axis O as the same axis, and is rotatable about the central axis O.

[0015] The rotating body 20 is rotatable relative to the stationary body 10 by a ball bearing (not shown) arranged in a gap between opposing surfaces in the direction of the central axis O with respect to the stationary body 10.

[0016] Although the stationary body 10 is an input-side transmission body and the rotating body 20 is an output-side transmission body, the stationary body 10 may be an output-side transmission body and the rotating body 20 may be an input-side transmission body.

[0017] Furthermore, the relationship between the stationary body 10 and the rotating body 20 only needs to be relatively rotated, and therefore both the stationary body 10 and the rotating body 20 can rotate, and for the sake of simplicity, it is referred to as the stationary body 10.

[0018] As in the Fig. 1 and Fig. 4, the stationary body 10 includes a first divided waveguide 11, a first coupling portion 12A, a second coupling portion 12B, a first waveguide 13, and a second waveguide 14.

[0019] The first divided waveguide 11, the first coupling portion 12A, the second coupling portion 12B, the first waveguide 13, and the second waveguide 14 form an annular shape centered on the central axis O, with another end portion of the first waveguide 13 and another end portion of the second waveguide 14 facing each other.

[0020] That is, the first waveguide 13, the first coupling portion 12A, the first split waveguide 11, the second coupling portion 12B, and the second waveguide 14 are arranged in this order in a ring shape in one direction, clockwise in the first embodiment.

[0021] In the following, the position direction is referred to as clockwise.

[0022] In the stationary body 10, a side orthogonal to the central axis O and facing the rotating body 20 is called a first side, a side located on a side opposite to the first side is called a second side, a side located on an inner periphery is called an inner peripheral surface, and a side located on an outer periphery is called an outer peripheral surface in the first embodiment.

[0023] The first split waveguide 11 is arranged along an arc centered on the central axis O and has a flat opening 11A on the first side.

[0024] As in Fig. 2, the cross-sectional shape of the first split waveguide 11 is a shape having three sides of a rectangle except for the opening 11A.

[0025] That is, the first split waveguide 11 is formed by an arc-shaped metallic conductor having the second side wall, an inner peripheral wall, and an outer peripheral wall.

[0026] The cross-sectional shape here refers to a cross-sectional shape in a direction along the central axis O, in other words, a cross-sectional shape in a plane passing through the central axis O and parallel to the central axis O.

[0027] In the following description, the terms “cross-sectional shape of a waveguide” and “cross-sectional shape of a waveguide path” refer to the cross-sectional shape in a direction along the central axis O.

[0028] One end of the first waveguide 13 is connected to one end of the first divided waveguide 11 via the first coupling portion 12A, and its other end is connected to the transmission circuit 30, which outputs a transmission signal.

[0029] As in Fig. 3, the cross-sectional shape of the first waveguide 13 is rectangular.

[0030] The first waveguide 13 is arranged along an arc centered on the central axis O and is formed by an arc-shaped metallic conductor having the first side wall, the second side wall, an inner peripheral wall and an outer peripheral wall.

[0031] The first waveguide 13 has a tubular shape, and its inner side serves as a waveguide path.

[0032] The cross-sectional shape of the waveguide path in the first waveguide 13 is also rectangular, and the length of a side a in the direction of the central axis O, ie, a side a parallel to the central axis O, is longer than the length of a side perpendicular to the central axis O.

[0033] The length of the side a in the direction of the central axis O in the cross-sectional shape of the waveguide path in the first waveguide 13 is longer than 1 / 2 wavelength of the guide wavelength of the transmitted signal.

[0034] It should be noted that the first waveguide 13 has a shape along an arc centered on the central axis O, but may also be a straight line.

[0035] One end of the second waveguide 14 is connected to another end of the first split waveguide 11 via the second coupling portion 12B, and its other end is connected to a terminating resistor 50.

[0036] The other end of the second waveguide 14 can be short-circuited instead of being connected to the terminating resistor 50.

[0037] The cross-sectional shape of the second waveguide 14 is a rectangle with the same size as the first waveguide 13.

[0038] The second waveguide 14 is arranged along an arc centered on the central axis O and is formed by an arc-shaped metallic cylindrical conductor having the first side wall, the second side wall, an inner peripheral wall and an outer peripheral wall.

[0039] It should be noted that the second waveguide 14 has a shape along the arc centered on the central axis O, but may also be a straight line.

[0040] In a state where the first split waveguide 11 is coupled to the first waveguide 13 and the second waveguide 14 via the first coupling portion 12A and the second coupling portion 12B, respectively, the second side of the first split waveguide 11 is in the same plane as the second side of the first waveguide 13 and the second side of the second waveguide 14, and the opening of the first split waveguide 11 is in a plane shorter than the first side of the first waveguide 13 and the first side of the second waveguide 14 by a thickness of the first side wall of the first waveguide 13, or is in the same plane as the first side of the first waveguide 13 and the first side of the second waveguide 14.

[0041] A length of a side b in the direction of the central axis O in the cross-sectional shape serving as a waveguide path in the first split waveguide 11, that is, a length of a side b parallel to the central axis O is 1 / 2 of the length of the side a in the direction of the central axis O in the cross-sectional shape of the waveguide path in the first waveguide 13.

[0042] It should be noted that 1 / 2 does not just refer to 1 / 2, but 1 / 2 is within a range allowed in the design.

[0043] A thickness of the second sidewall in the first split waveguide 11 is larger than a thickness of the second sidewall in the first waveguide 13, and the thicknesses of the inner peripheral wall and the outer peripheral wall in the first split waveguide 11 are the same as the thicknesses of the inner peripheral wall and the outer peripheral wall in the first waveguide 13.

[0044] As in the Fig. 1 and Fig. 7, the rotating body 20 includes a second divided waveguide 21 and a plurality of third waveguides 23A, 23B.

[0045] In the rotating body 20, a side orthogonal to the central axis O and facing the stationary body 10 is called a first side, a side located on a side opposite to the first side is called a second side, a side located on an inner periphery is called an inner peripheral surface, and a side located on an outer periphery is called an outer peripheral surface in the first embodiment.

[0046] As in the Fig. 1 and Fig. 7, the second split waveguide 21 is arranged along a circumference having the same diameter as the arc in which the first split waveguide 11 is arranged with the central axis O as the center, and has a shallow opening 21A facing the opening 11A of the first split waveguide 11, the first side of the first waveguide 13, and the first side of the second waveguide 14 on the first side.

[0047] As in Fig. 5, the cross-sectional shape of the second split waveguide 21 is a shape having three sides of a rectangle except for the opening 21A.

[0048] That is, the second split waveguide 21 is formed by a ring-shaped metallic conductor having the second side wall, an inner peripheral wall and an outer peripheral wall and connected all around.

[0049] The first split waveguide 11 and the second split waveguide 21 form a waveguide at a position where the opening 11A of the first split waveguide 11 and the opening 21A of the second split waveguide 21 face each other.

[0050] At the position where the opening 11A of the first split waveguide and the opening 21A of the second split waveguide 21 face each other, an end face of the outer peripheral wall of the first split waveguide 11 and an end face of the outer peripheral wall of the second split waveguide 21, and an end face of the inner peripheral wall of the first split waveguide 11 and an end face of the inner peripheral wall of the second split waveguide 21 are arranged close to each other by using a choke structure in such a manner that an electromagnetic field due to an electromagnetic wave that is a transmitted signal does not leak.

[0051] It should be noted that the end face of the outer peripheral wall of the first split waveguide 11 and the end face of the outer peripheral wall of the second split waveguide 21, as well as the end face of the inner peripheral wall of the first split waveguide 11 and the end face of the inner peripheral wall of the second split waveguide 21, may be arranged in direct contact with each other and in an electrically conductive state.

[0052] A length of a side c in the direction of the central axis O in the cross-sectional shape serving as a waveguide path in the second split waveguide 21, ie, a length of a side c parallel to the central axis O is equal to the length of the side b in the direction of the central axis O in the cross-sectional shape serving as a waveguide path in the first split waveguide 11.

[0053] That is, the cross-sectional shape of the waveguide path in the waveguide formed by the first split waveguide 11 and the second split waveguide 21 is rectangular, and one side (b + c) in the direction of the central axis O in the cross-sectional shape of the waveguide is longer than the length of the side perpendicular to the central axis O and longer than 1 / 2 wavelength of the guide wavelength of the transmitted signal.

[0054] It should be noted that although side b and side c have the same length, the lengths of side b and side c can be different as long as side (b + c) has a length greater than 1 / 2 wavelength of the guide wavelength of the transmitted signal.

[0055] However, the length of side c is equal to or less than 1 / 2 wavelength of the guide wavelength of the transmitted signal.

[0056] The second split waveguide 21 and the first waveguide 13 form a pseudo waveguide at a position where the opening 21A of the second split waveguide 21 and the first side of the first waveguide 13 face each other.

[0057] The length of the side c in the direction of the central axis O in the cross-sectional shape serving as a pseudo-waveguide path in the pseudo-waveguide formed by the second split waveguide 21 and the first waveguide 13 is the same as the length of the side c in the direction of the central axis O in the cross-sectional shape serving as a waveguide path in the second split waveguide 21, and is equal to or less than 1 / 2 wavelength of the guide wavelength of the transmitted signal.

[0058] Therefore, the transmitted signal is not transmitted to the pseudo waveguide formed at the position where the opening 21A of the second split waveguide 21 and the first side of the first waveguide 13 face each other.

[0059] It should be noted that even if the first waveguide 13 is straight, a pseudo waveguide is formed at a position where the first side of the first waveguide 13 faces the opening 21A of the second split waveguide 21 at an end portion connected to the first coupling portion 12A.

[0060] The second split waveguide 21 and the second waveguide 14 form a pseudo waveguide at a position where the opening 21A of the second split waveguide 21 and the first side of the second waveguide 14 face each other.

[0061] The length of the side c in the direction of the central axis O in the cross-sectional shape serving as a pseudo-waveguide path in the pseudo-waveguide formed by the second split waveguide 21 and the second waveguide 14 is the same as the length of the side c in the direction of the central axis O in the cross-sectional shape serving as a waveguide path in the second split waveguide 21, and is equal to or less than 1 / 2 wavelength of the guide wavelength of the transmitted signal.

[0062] Therefore, the transmitted signal is not transmitted to the pseudo waveguide formed at the position where the opening 21A of the second split waveguide 21 and the first side of the second waveguide 14 face each other.

[0063] It should be noted that even if the second waveguide 14 is straight, a pseudo waveguide is formed at a position where the first side of the second waveguide 14 faces the opening 21A of the second split waveguide 21 at an end portion connected to the second coupling portion 12B.

[0064] As in Fig. 1 and Fig. 7, the plurality of third waveguides 23A and 23B are arranged at equal intervals on the second side opposite to the first side of the second split waveguide 21 and coupled to the second split waveguide 21 via directional couplers 22A and 22B.

[0065] In the first embodiment, the plurality of third waveguides consists of two third waveguides 23A, 23B, which will be described below.

[0066] It should be noted that even in the case of three or more third waveguides, each of the three or more third waveguides has the same configuration.

[0067] The third waveguide 23A and the third waveguide 23B are each arranged to be separated from each other by 180° along an arc centered on the central axis O, and have the second side wall, an inner peripheral wall, and an outer peripheral wall, as shown in a cross-sectional shape of the third waveguide 23A in Fig. 6, and the first side wall is formed by an arc-shaped metallic conductor serving as the second side wall of the second split waveguide 21.

[0068] The cross-sectional shape of the third waveguide 23A is rectangular, as shown in Fig. 6 shown.

[0069] The cross-sectional shape of a waveguide path in the third waveguide 23A is also rectangular, and the length of a side d in the direction of the central axis O is longer than the length of the side perpendicular to the central axis O.

[0070] The length of the side d in the direction of the central axis O in the cross-sectional shape of the waveguide path in the third waveguide 23A is greater than 1 / 2 wavelength of the guide wavelength of the transmitted signal.

[0071] The cross-sectional shape of the third waveguide 23B is also a rectangle with the same size as the cross-sectional shape of the third waveguide 23A.

[0072] The cross-sectional shape of a waveguide path in the third waveguide 23B is also rectangular, and the length of the side d in the direction of the central axis O is longer than the length of the side perpendicular to the central axis O.

[0073] The length of the side d in the direction of the central axis O in the cross-sectional shape of the waveguide path in the third waveguide 23B is longer than 1 / 2 wavelength of the guide wavelength of the transmitted signal.

[0074] The two directional couplers 22A and 22B are arranged at positions separated by 180° on the second side of the second split waveguide 21.

[0075] The first directional coupler 22A and the second directional coupler 22B are each formed by one or more coupling holes formed in the second side wall of the second split waveguide 21, and transmit a transmitted signal in one direction.

[0076] The third waveguide 23A is coupled to the second split waveguide 21 at one end portion through the first directional coupler 22A and is arranged to extend in a direction along the second side of the second split waveguide 21.

[0077] One end of the third waveguide 23A is terminated or short-circuited, the other end is connected to the receiving circuit 41.

[0078] The third waveguide 23B is coupled to the second split waveguide 21 through the second directional coupler 22B at one end portion and arranged to extend in a direction along the second side of the second split waveguide 21.

[0079] One end of the third waveguide 23B is terminated or short-circuited, the other end is connected to the receiving circuit 42.

[0080] The functional principle and operation of the rotary joint according to the first embodiment will be described below with reference to the Fig. 8 to 10 described.

[0081] In Fig. 8, as indicated by X1 and X2, at the position where the opening 21A of the second split waveguide 21 and the first side of the second waveguide 14 face each other, the length of the side c in the direction of the central axis O in the pseudo-waveguide path in the pseudo-waveguide formed by the second split waveguide 21 and the second waveguide 14 is equal to or less than 1 / 2 wavelength of the guide wavelength of the transmitted signal, and thus the pseudo-waveguide path in the pseudo-waveguide is sealed from the transmitted signal.

[0082] That is, the transmitted signal is not transmitted in the pseudowaveguide path in the pseudowaveguide formed by the second split waveguide 21 and the second waveguide 14.

[0083] Similarly, in Fig. 8 at the position where the opening 21A of the second split waveguide 21 and the first side of the first waveguide 13 face each other, the length of the side c in the direction of the central axis O in the pseudo-waveguide path of the pseudo-waveguide formed by the second split waveguide 21 and the first waveguide 13 is equal to or less than 1 / 2 wavelength of the guide wavelength of the transmitted signal, and thus the pseudo-waveguide in the pseudo-waveguide is sealed from the transmitted signal.

[0084] That is, in the pseudo waveguide path in the pseudo waveguide formed by the second divided waveguide 21 and the first waveguide 13, a transmission path in an arrow direction of Y2 shown in Fig. 8 is not formed with respect to the transmitted signal, and the transmitted signal is not transmitted.

[0085] On the other hand, as shown by X3 and X4 in Fig. 8, at the position where the opening 11A of the first split waveguide 11 and the opening 21A of the second split waveguide 21 face each other, the length of the side (b + c) in the direction of the central axis O in the waveguide path of the waveguide formed by the first split waveguide 11 and the second split waveguide 21 is longer than 1 / 2 wavelength of the guide wavelength of the transmitted signal, and thus the inside of the waveguide path of the waveguide formed by the first split waveguide 11 and the second split waveguide 21 becomes a transmission path that can transmit the transmitted signal in an arrow direction of Y1 shown in Fig. 8 is shown.

[0086] That is, at the position where the opening 21A of the second split waveguide 21 faces the opening 11A of the first split waveguide 11, a transmission path through which the transmission signal transmitted from the transmission circuit 30 can be transmitted in one direction is formed by the waveguide path of the waveguide formed by the first split waveguide 11 and the second split waveguide 21, but at the position where the first side of the first waveguide 13 and the first side of the second waveguide 14 face each other, the transmission path is not formed, so that the transmission signal transmitted from the transmission circuit 30 passes through the reception circuit 41 or the reception circuit 42 one-way.

[0087] Since the transmission signal transmitted from the transmission circuit 30 is transmitted unilaterally to the reception circuit 41 or the reception circuit 42, there is no possibility of the ring resonance mode being excited, and the transmission signal can have a wide band.

[0088] As in Fig. 9, in Example 1 in which the positional relationship between the stationary body 10 and the rotating body 20 is a first position, when the transmission signal from the transmission circuit 30 is input to the first waveguide 13, the transmission signal is transmitted in the waveguide path of the first waveguide 13 as indicated by arrows Y11 and Y12 in the drawing, and is transmitted in the waveguide path of the waveguide formed by the first divided waveguide 11 and the second divided waveguide 21 at the position where the openings 11A and 21A face each other via the first coupling portion 12A as indicated by arrow Y13 in the drawing, that is, in a direction in the transmission path, clockwise in the first embodiment, as indicated by arrow Y14 in the drawing.

[0089] The transmission signal transmitted from the first coupling portion 12A to the transmission path is not transmitted to the pseudo waveguide formed by the second split waveguide 21 and the first waveguide 13.

[0090] When the transmission signal transmitted on the transmission path reaches the second directional coupler 22B, the transmission signal is transmitted to the third waveguide 23B as indicated by the arrow Y15 in the drawing, transmitted to the receiving circuit 42 as indicated by the arrows Y16 and Y17 in the drawing, and received by the receiving circuit 42.

[0091] The transmission signal transmitted through the transmission path indicated by the arrow Y14 in the drawing is not transmitted to the pseudo waveguide formed by the second divided waveguide 21 and the second waveguide 14.

[0092] The first position is a section from a position where the second directional coupler 22B in the rotating body 20 is located at an output end of the first coupling portion 12A in the stationary body 10 to a position where the rotating body 20 is rotated by 180° in one direction.

[0093] Further, the second position is a section from a position where the first directional coupler 22A of the rotating body 20 is located at the output end of the first coupling portion 12A in the stationary body 10 to the position where the rotating body 20 is rotated 180 degrees in one direction.

[0094] It should be noted that the position of Example 1 in the first in Fig. 9 is assumed, in which the positional relationship between the stationary body 10 and the rotating body 20 is 0° for the sake of simplicity of description.

[0095] In short, when the positional relationship between the stationary body 10 and the rotating body 20 is the first position, the rotary joint according to the first embodiment forms a first transmission path in which the transmission signal from the transmission circuit 30 is transmitted from the first waveguide 13 (arrow Y11 and arrow Y12) to the first coupling portion 12A (arrow Y13), the waveguide path of the waveguide formed by the first split waveguide 11 and the second split waveguide 21 (arrow Y14), the second directional coupler 22B (arrow Y15), and the third waveguide 23B (arrow Y16 and arrow Y17).

[0096] The transmission signal transmitted to the first transmission path at this time is one-sided, and the ring resonance mode is not excited.

[0097] From Example 1 in which the positional relationship between the stationary body 10 and the rotating body 20 is the first position, it is next assumed that the rotating body 20 is rotated in one direction by 90° with respect to the stationary body 10.

[0098] This position corresponds to the position of Example 1 in the second position and is in Fig. 10 shown.

[0099] As in Fig. 10, in Example 1 in which the positional relationship between the stationary body 10 and the rotating body 20 is the second position, when the transmission signal from the transmission circuit 30 is input to the first waveguide 13, the transmission signal is transmitted in the waveguide path of the first waveguide 13 as indicated by arrows Y21 and Y22 in the drawing, and transmitted in the waveguide path of the waveguide formed by the first divided waveguide 11 and the second divided waveguide 21 at the position where the openings 11A and 21A face each other via the first coupling portion 12A as indicated by arrow Y23 in the drawing, that is, the transmission path in one direction as indicated by arrow Y24 in the drawing.

[0100] The transmission signal transmitted from the first coupling portion 12A to the transmission path is not transmitted to the pseudo waveguide formed by the second split waveguide 21 and the first waveguide 13.

[0101] When the transmission signal transmitted on the transmission path reaches the first directional coupler 22A, the transmission signal is transmitted to the third waveguide 23A as indicated by the arrow Y25 in the drawing, transmitted to the receiving circuit 41 as indicated by the arrows Y26 and Y27 in the drawing, and received by the receiving circuit 41.

[0102] The transmission signal transmitted through the transmission path indicated by the arrow Y24 in the drawing is not transmitted to the pseudo waveguide formed by the second divided waveguide 21 and the second waveguide 14.

[0103] In short, when the positional relationship between the stationary body 10 and the rotating body 20 is the first position, the rotary joint according to the first embodiment forms a second transmission path in which the transmission signal from the transmission circuit 30 is transmitted from the first waveguide 13 (arrow Y21 and arrow Y22) to the first coupling portion 12A (arrow Y23), the waveguide path of the waveguide formed by the first split waveguide 11 and the second split waveguide 21 (arrow Y24), the first directional coupler 22A (arrow Y25), and the third waveguide 23A (arrow Y26 and arrow Y27).

[0104] The transmission signal transmitted to the second transmission path at this time is one-sided, and the ring resonance mode is not excited.

[0105] In the above description, in the rotary joint according to the first embodiment, the transmission signal is transmitted through the first transmission path in Example 1 in which the positional relationship between the stationary body 10 and the rotating body 20 is the first position, and the transmission signal is transmitted through the second transmission path in Example 1 in which the positional relationship between the stationary body 10 and the rotating body 20 is the second position.

[0106] However, at a transition angle at which the rotating body 20 switches from the first transmission path to the second transmission path with respect to the stationary body 10, there are transmission paths of both the first and second transmission paths.

[0107] In short, the rotary joint according to the first embodiment can transmit the transmission signal from the transmission circuit 30 to the reception circuits of the reception circuit 41, the reception circuit 42, or both the reception circuit 41 and the reception circuit 42 via three transmission paths of the first transmission path, the second transmission path, or both the first transmission path and the second transmission path in accordance with the positional relationship between the stationary body 10 and the rotating body 20.

[0108] That is, the transmission signal may be transmitted with the positional relationship of the rotating body 20 with respect to the stationary body 10, that is, the rotation angle of the rotating body 20 at the entire rotation angle, and the output signal of the receiving circuit 41 and the output signal of the receiving circuit 42 may be switched and output, or the power may be combined and output by controlling the positional relationship of the rotating body 20 with respect to the stationary body 10 or switching the output signal of the receiving circuit 41 and the output signal of the receiving circuit 42 by a switch.

[0109] Furthermore, the transmission signal to be transmitted is unidirectional in both the first and second transmission paths, and the ring resonance mode is not excited.

[0110] Therefore, a transmission signal to be transmitted can have a wide band.

[0111] It should be noted that in the rotary joint according to the first embodiment, the number of the third waveguides is two, but in the case where it is three, three directional couplers are arranged at equal intervals, ie, at intervals of 120°, and each of the three third waveguides is coupled to the second divided waveguide 21 through a corresponding directional coupler.

[0112] The positional relationship between the stationary body 10 and the rotating body 20 in this case is the first position, the second position, and the third position in units of 120°, and the rotary joint forms the first transmission path, the second transmission path, and the third transmission path corresponding to each of the three third waveguides.

[0113] As described above, the rotary joint according to the first embodiment comprises the stationary body 10 having the arcuate first split waveguide 11 having the flat opening 11A on the first side and the first waveguide 13, one end of which is connected to one end of the first split waveguide 11 via the first coupling portion 12A, and the rotating body 20 including the annular second split waveguide 21 having the flat opening 21A facing the opening 11A of the first split waveguide 11 on the first side, and the plurality of third waveguides 23A and 23B arranged at intervals on the second side of the second split waveguide 21, which are respectively coupled to the second split waveguide 21 via the directional couplers 22A and 22B and are rotatable about the central axis O with respect to the stationary body 10.in which the second split waveguide 21 forms a waveguide with the first split waveguide 11 at a position where the openings 11A and 21A face each other, so that a first transmission path can be formed by the first waveguide 13, the first coupling section 12A, the waveguide formed by the first split waveguide 11 and the second split waveguide 21, the directional coupler 22A, and the third waveguide 23A, and a second transmission path can be formed by the first waveguide 13, the first coupling section 12A, the waveguide formed by the first split waveguide 11 and the second split waveguide 21, the directional coupler 22B, and the third waveguide 23B.

[0114] A rectangle is defined in which the length of the side parallel to the central axis O in the cross-sectional shape of the pseudo-waveguide path in the pseudo-waveguide formed by the first waveguide 13 and the second split waveguide 21 at the position where the first side of the first waveguide 13 and the opening 21A of the second split waveguide 21 face each other is equal to or less than 1 / 2 wavelength of the guide wavelength of the transmitted signal, and a rectangle is defined in which the length of the side parallel to the central axis O in the cross-sectional shape of the pseudo-waveguide path in the pseudo-waveguide formed by the second waveguide 14 and the second split waveguide 21 at the position where the first side of the second waveguide 14 and the opening 21A of the second split waveguide 21 face each other,is equal to or less than 1 / 2 wavelength of the guide wavelength of the transmitted signal, so that the transmitted signal is not transmitted into the pseudo-waveguide and the transmitted signal is transmitted in a one-way direction in the waveguide path of the waveguide formed by the first split waveguide 11 and the second split waveguide 21.

[0115] This prevents the ring resonance mode from being excited and allows the transmitted signal to have a broad band.

[0116] In addition, since both the stationary body 10 and the rotating body 20 have a hollow portion in the center including the central axis O, various control lines can be wired in the hollow portion in the center. Second embodiment.

[0117] A rotary joint according to a second embodiment is described with reference to the Fig. 11 to 15.

[0118] The rotary joint according to the second embodiment differs in that while the rotary joint according to the first embodiment is a rotating body 20 with a plurality of third waveguides, it is a rotating body 20 with a third waveguide and the other points are the same.

[0119] In the Fig. 11 to 15 denote the same reference numerals as in the Fig. 1 to 10 the same or corresponding parts.

[0120] The stationary body 10 is the same as the stationary body 10 in the rotary joint according to the first embodiment, and therefore the rotating body 20 will be mainly described below.

[0121] As in Fig. 11 and Fig. 13, the rotating body 20 comprises a second split waveguide 21 and a third waveguide 23.

[0122] As in the Fig. 11 and Fig. 13, the second split waveguide 21 is arranged along a circumference having the same diameter as the arc in which the first split waveguide 11 is arranged with the central axis O as the center, and has a shallow opening 21A facing the opening 11A of the first split waveguide 11, the first side of the first waveguide 13, and the first side of the second waveguide 14 on the first side.

[0123] As in Fig. 12, the cross-sectional shape of the second split waveguide 21 is a shape having three sides of a rectangle except for the opening 21A.

[0124] That is, the second split waveguide 21 is formed by a ring-shaped metallic conductor having the second side wall, an inner peripheral wall and an outer peripheral wall and connected all around.

[0125] The first split waveguide 11 and the second split waveguide 21 form a waveguide at a position where the opening 11A of the first split waveguide 11 and the opening 21A of the second split waveguide 21 face each other.

[0126] At the position where the opening 11A of the first split waveguide and the opening 21A of the second split waveguide 21 face each other, an end face of the outer peripheral wall of the first split waveguide 11 and an end face of the outer peripheral wall of the second split waveguide 21, and an end face of the inner peripheral wall of the first split waveguide 11 and an end face of the inner peripheral wall of the second split waveguide 21 are arranged close to each other by using a choke structure in such a manner that an electromagnetic field due to an electromagnetic wave that is a transmitted signal does not leak.

[0127] It should be noted that the end face of the outer peripheral wall of the first split waveguide 11 and the end face of the outer peripheral wall of the second split waveguide 21, as well as the end face of the inner peripheral wall of the first split waveguide 11 and the end face of the inner peripheral wall of the second split waveguide 21, may be arranged in direct contact with each other and in an electrically conductive state.

[0128] The length of a side c in the direction of the central axis O in the cross-sectional shape serving as a waveguide path in the second split waveguide 21 is the same as the length of a side b in the direction of the central axis O in the cross-sectional shape serving as a waveguide path in the first split waveguide 11.

[0129] That is, the cross-sectional shape of the waveguide path in the waveguide formed by the first split waveguide 11 and the second split waveguide 21 is rectangular, and one side (b + c) in the direction of the central axis O in the cross-sectional shape of the waveguide is longer than the length of the side perpendicular to the central axis O and longer than 1 / 2 wavelength of the guide wavelength of the transmitted signal.

[0130] It should be noted that although side b and side c have the same length, the lengths of side b and side c can be different as long as side (b + c) has a length greater than 1 / 2 wavelength of the guide wavelength of the transmitted signal.

[0131] However, the length of side c is equal to or less than 1 / 2 wavelength of the guide wavelength of the transmitted signal.

[0132] The second split waveguide 21 and the first waveguide 13 form a pseudo waveguide at a position where the opening 21A of the second split waveguide 21 and the first side of the first waveguide 13 face each other.

[0133] The length of the side c in the direction of the central axis O in the cross-sectional shape serving as a pseudo-waveguide path in the pseudo-waveguide formed by the second split waveguide 21 and the first waveguide 13 is the same as the length of the side c in the direction of the central axis O in the cross-sectional shape serving as a waveguide path in the second split waveguide 21, and is equal to or less than 1 / 2 wavelength of the guide wavelength of the transmitted signal.

[0134] Therefore, the transmitted signal is not transmitted to the pseudo waveguide formed at the position where the opening 21A of the second split waveguide 21 and the first side of the first waveguide 13 face each other.

[0135] It should be noted that even if the first waveguide 13 is straight, a pseudo waveguide is formed at a position where the first side of the first waveguide 13 faces the opening 21A of the second split waveguide 21 at an end portion connected to the first coupling portion 12A.

[0136] The second split waveguide 21 and the second waveguide 14 form a pseudo waveguide at a position where the opening 21A of the second split waveguide 21 and the first side of the second waveguide 14 face each other.

[0137] The length of the side c in the direction of the central axis O in the cross-sectional shape serving as a pseudo-waveguide path in the pseudo-waveguide formed by the second split waveguide 21 and the second waveguide 14 is the same as the length of the side c in the direction of the central axis O in the cross-sectional shape serving as a waveguide path in the second split waveguide 21, and is equal to or less than 1 / 2 wavelength of the guide wavelength of the transmitted signal.

[0138] Therefore, the transmitted signal is not transmitted to the pseudo waveguide formed at the position where the opening 21A of the second split waveguide 21 and the first side of the second waveguide 14 face each other.

[0139] It should be noted that even if the second waveguide 14 is straight, a pseudo waveguide is formed at a position where the first side of the second waveguide 14 faces the opening 21A of the second split waveguide 21 at an end portion connected to the second coupling portion 12B.

[0140] As in Fig. 11 and Fig. 13, the third waveguide 23 is arranged annularly along the second side of the second split waveguide 21 and coupled to the second split waveguide 21 via a plurality of directional couplers 22A and 22B arranged on the second side of the second split waveguide 21 at equal intervals from each other along the circumference.

[0141] As in a cross-sectional shape in Fig. 12, the third waveguide 23 includes the second side wall, an inner peripheral wall and an outer peripheral wall, and is formed by an annular metallic conductor having the first side wall as the second side wall of the second split waveguide 21.

[0142] The cross-sectional shape of the third waveguide 23 is rectangular, as shown in Fig. 12 shown.

[0143] The cross-sectional shape of the waveguide path in the third waveguide 23 is also rectangular, and the length of a side d in the direction of the central axis O is longer than the length of the side perpendicular to the central axis O.

[0144] The length of the side d in the direction of the central axis O in the cross-sectional shape of the waveguide path in the third waveguide 23 is greater than 1 / 2 wavelength of the guide wavelength of the transmitted signal.

[0145] One end of the third waveguide 23 is connected to the receiving circuit 40, the other end is short-circuited or terminated 60.

[0146] The plurality of directional couplers are two directional couplers 22A and 22B arranged 180° apart from each other in the second embodiment, and the two directional couplers 22A and 22B are described below.

[0147] One end of the third waveguide 23 to which the receiving circuit 40 is connected and the other end of the third waveguide 23 which is short-circuited or terminated 60 are arranged at intermediate positions between the first directional coupler 22A and the second directional coupler 22B.

[0148] It should be noted that even if there are three or more directional couplers, the directional couplers have the same configuration and are arranged at intervals of 120°.

[0149] The operation of the rotary joint according to the second embodiment is described below with reference to the Fig. 14 and Fig. 15 described.

[0150] As in Fig. 14, in Example 1 in which the positional relationship between the stationary body 10 and the rotating body 20 is the first position, when a transmission signal from the transmission circuit 30 is input to the first waveguide 13, the transmission signal is transmitted in the waveguide path of the first waveguide 13 as indicated by arrows Y31 and Y32 in the drawing, and is transmitted in the waveguide path of the waveguide formed by the first divided waveguide 11 and the second divided waveguide 21 at the position where the openings 11A and 21A face each other via the first coupling portion 12A as indicated by arrow Y33 in the drawing, that is, in a direction of the transmission path, clockwise in the second embodiment as indicated by arrow Y34 in the drawing.

[0151] The transmission signal transmitted from the first coupling portion 12A to the transmission path is not transmitted to the pseudo waveguide formed by the second split waveguide 21 and the first waveguide 13.

[0152] Therefore, in the first directional coupler 22A located on the second side of the first waveguide 13, the transmission signal is not transmitted to the pseudo-waveguide path formed by the second split waveguide 21 and the first waveguide 13, and thus the first directional coupler 22A does not operate.

[0153] When the transmission signal transmitted in the transmission path reaches the second directional coupler 22B, the transmission signal is transmitted to the third waveguide 23 as indicated by the arrow Y35 in the drawing, transmitted to the receiving circuit 40 as indicated by the arrows Y36 and Y37 in the drawing, and received by the receiving circuit 40.

[0154] A transmission signal transmitted through a transmission path indicated by the arrow Y34 in the drawing is not transmitted to the pseudo waveguide formed by the second divided waveguide 21 and the second waveguide 14.

[0155] The first position is a section from a position where the second directional coupler 22B in the rotating body 20 is located at an output end of the first coupling portion 12A in the stationary body 10 to a position where the rotating body 20 is rotated by 180° in one direction.

[0156] Further, the second position is a section from a position where the first directional coupler 22A of the rotating body 20 is located at the output end of the first coupling portion 12A in the stationary body 10 to the position where the rotating body 20 is rotated 180 degrees in one direction.

[0157] It should be noted that the position of Example 1 in the first in Fig. 14 is assumed, in which the positional relationship between the stationary body 10 and the rotating body 20 is 0° for the sake of simplicity of description.

[0158] In short, when the positional relationship between the stationary body 10 and the rotating body 20 is the first position, the rotary joint according to the second embodiment forms a first transmission path in which the transmission signal from the transmission circuit 30 passes from the first waveguide 13 (arrow Y31 and arrow Y32) to the first coupling portion 12A (arrow Y33), the waveguide path of the waveguide formed by the first split waveguide 11 and the second split waveguide 21 (arrow Y34), the second directional coupler 22B (arrow Y35), and the third waveguide 23 (arrow Y36 and arrow Y37).

[0159] The transmission signal transmitted to the first transmission path at this time is one-sided, and the ring resonance mode is not excited.

[0160] Next, assume that the rotating body 20 is rotated in one direction by 135° with respect to the stationary body 10 of Example 1 in which the positional relationship between the stationary body 10 and the rotating body 20 is the first position.

[0161] This position corresponds to the position of Example 1 in the second position is in Fig. 15 shown.

[0162] As in Fig.15, in Example 1 in which the positional relationship between the stationary body 10 and the rotating body 20 is the second position, when the transmission signal from the transmission circuit 30 is input to the first waveguide 13, the transmission signal is transmitted in the waveguide path of the first waveguide 13 as indicated by arrows Y41 and Y42 in the drawing, and in the waveguide path of the waveguide formed by the first divided waveguide 11 and the second divided waveguide 21 at the position where the openings 11A and 21A face each other via the first coupling portion 12A as indicated by arrow Y43 in the drawing, that is, the transmission path in one direction as indicated by arrow Y44 in the drawing.

[0163] The transmission signal transmitted from the first coupling portion 12A to the transmission path is not transmitted to the pseudo waveguide formed by the second split waveguide 21 and the first waveguide 13.

[0164] When the transmission signal transmitted in the transmission path reaches the first directional coupler 22A, the transmission signal is transmitted to the third waveguide 23 as indicated by the arrow Y45 in the drawing, transmitted to the receiving circuit 40 as indicated by the arrows Y46 and Y47 in the drawing, and received by the receiving circuit 40.

[0165] The transmission signal transmitted through the transmission path indicated by the arrow Y44 in the drawing is not transmitted to the pseudo waveguide formed by the second divided waveguide 21 and the second waveguide 14.

[0166] Since the length of the side c in the direction of the central axis O in the pseudowaveguide path of the pseudowaveguide formed by the second split waveguide 21 and the second waveguide 14 is equal to or less than 1 / 2 wavelength of the guide wavelength of the transmitted signal, the transmission signal transmitted via the second directional coupler 22B located on the second side of the second waveguide 14 is transmitted to the third waveguide 23 without being influenced by the second directional coupler 22B.

[0167] In short, when the positional relationship between the stationary body 10 and the rotating body 20 is the second position, the rotary joint according to the second embodiment forms a second transmission path in which the transmission signal from the transmission circuit 30 is transmitted from the first waveguide 13 (arrow Y41 and arrow Y42) to the first coupling portion 12A (arrow Y43), the waveguide path of the waveguide formed by the first split waveguide 11 and the second split waveguide 21 (arrow Y44), the first directional coupler 22A (arrow Y45), and the third waveguide 23A (arrow Y46 and arrow Y47).

[0168] The transmission signal transmitted to the second transmission path at this time is one-sided, and the ring resonance mode is not excited.

[0169] In the above description, for the rotary joint according to the second embodiment, it was described that the transmission signal is transmitted through the first transmission path in Example 1 when the positional relationship between the stationary body 10 and the rotating body 20 is the first position, and the transmission signal is transmitted through the second transmission path in Example 1 when the positional relationship between the stationary body 10 and the rotating body 20 is the second position.

[0170] However, at a transition angle at which the rotating body 20 switches from the first transmission path to the second transmission path with respect to the stationary body 10, there are transmission paths of both the first and second transmission paths.

[0171] In short, the rotary joint according to the second embodiment can transmit the transmission signal from the transmission circuit 30 to the reception circuit 40 via three transmission paths, the first transmission path, the second transmission path, or both the first and second transmission paths, depending on the positional relationship between the stationary body 10 and the rotating body 20.

[0172] That is, the transmission signal can be transmitted with the positional relationship of the rotating body 20 with respect to the stationary body 10, that is, the rotation angle of the rotating body 20 at the entire rotation angle, and by controlling the positional relationship of the rotating body 20 with respect to the stationary body 10, the output signal from the receiving circuit 40 can be switched and output to the first transmission path or the second transmission path, or the power can be combined and output from both the first transmission path and the second transmission path.

[0173] Furthermore, the transmission signal to be transmitted is unidirectional in both the first and second transmission paths, and the ring resonance mode is not excited.

[0174] Therefore, a transmission signal to be transmitted can have a wide band.

[0175] Note that in the rotary joint according to the first embodiment, the number of directional couplers is two, but it may be coupled to the second split waveguide 21 by directional couplers, wherein three directional couplers are arranged at equal intervals, ie, at intervals of 120°, and the third waveguides 23 are arranged at equal intervals.

[0176] The positional relationship between the stationary body 10 and the rotating body 20 in this case is the first position, the second position, and the third position in units of 120°, and the rotary joint forms the first transmission path, the second transmission path, and a third transmission path corresponding to each of the three directional couplers.

[0177] As described above, the rotary joint according to the second embodiment includes the stationary body 10 having the arcuate first split waveguide 11 with the flat opening 11A on the first side and the first waveguide 13, one end of which is connected to one end of the first split waveguide 11 via the first coupling portion 12A, and the rotating body 20 having the annular second split waveguide 21 with the flat opening 21A facing the opening 11A of the first split waveguide 11 on the first side, and the third waveguide 23 arranged along a circumference of the second side opposite to the first side of the second split waveguide 21 and connected to the second split waveguide 21 via the plurality of directional couplers 22A and 22B arranged at intervals from each other along the circumference of the second split waveguide 21.is coupled and is rotatable about the central axis O with respect to the stationary body 10, wherein the second split waveguide 21 forms a waveguide with the first split waveguide 11 at a position where the openings 11A and 21A face each other, so that a first transmission path formed by the first waveguide 13, the first coupling section 12A, the waveguide formed by the first split waveguide 11 and the second split waveguide 21, the directional coupler 22A, and the third waveguide 23, and a second transmission path formed by the first waveguide 13, the first coupling section 12A, the waveguide formed by the first split waveguide 11 and the second split waveguide 21, the directional coupler 22B, and the third waveguide 23 can be formed.

[0178] A rectangle is defined in which the length of the side parallel to the central axis O in the cross-sectional shape of the pseudo-waveguide path in the pseudo-waveguide formed by the first waveguide 13 and the second split waveguide 21 at the position where the first side of the first waveguide 13 and the opening 21A of the second split waveguide 21 face each other is equal to or less than 1 / 2 wavelength of the guide wavelength of the transmitted signal, and a rectangle is defined in which the length of the side parallel to the central axis O in the cross-sectional shape of the pseudo-waveguide path in the pseudo-waveguide formed by the second waveguide 14 and the second split waveguide 21 at the position where the first side of the second waveguide 14 and the opening 21A of the second split waveguide 21 face each other,is equal to or less than 1 / 2 wavelength of the guide wavelength of the transmitted signal, so that the transmitted signal is not transmitted into the pseudo-waveguide and the transmitted signal is transmitted in a one-way direction in the waveguide path of the waveguide formed by the first split waveguide 11 and the second split waveguide 21.

[0179] This prevents the ring resonance mode from being excited and allows the transmitted signal to have a broad band.

[0180] It should be noted that free combinations of the individual embodiments, modifications of components of each of the embodiments, or omissions of components in each of the embodiments are possible. INDUSTRIAL APPLICABILITY

[0181] A rotary joint according to the present disclosure is suitable for a rotary joint used for a communication system and a microwave communication system for controlling a hand part of a robot arm. LIST OF REFERENCE SYMBOLS

[0182] 10: stationary body, 11: first split waveguide, 11A: aperture, 12A: first coupling section, 12B: second coupling section, 13: first waveguide, 14: second waveguide, 20: rotating body, 21: second split waveguide, 21A: aperture, 22A: first directional coupler, 22B: second directional coupler, 23, 23A, 23B: third waveguide, 30: transmission circuit, 40, 41, 42: reception circuit, 50: termination resistor or short circuit, 60: termination resistor or short circuit QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited non-patent literature

[0000] K. Rambabu and Jens Bornemann. “Compact Single-Channel Rotary Joint Using Ridged Waveguide Sections for Phase Adjustment,” IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 51, NO. 8, AUGUST. 2003, pp. 1982-1986

[0004]

Claims

[1] Slewing ring, comprising: a stationary body having a first split waveguide arranged along an arc centered on a central axis and having an opening that is flat on a first side of the stationary body, a first waveguide having a first end connected to a first end of the first split waveguide via a first coupling portion, and a second waveguide having a first end connected to a second end of the first split waveguide via a second coupling portion; and a rotating body having a second split waveguide of an annular shape arranged along a circumference having the same diameter as the arc along which the first split waveguide is arranged around the central axis, and having an opening that is flat on the first side of the rotating body facing the opening of the first split waveguide, and comprising a plurality of third waveguides arranged at intervals from one another on a second side of the rotating body opposite the first side of the rotating body of the second split waveguide, each of which is coupled to the second split waveguide via a directional coupler, and which is rotatable with respect to the stationary body about the central axis, in which the second split waveguide forms a waveguide with the first split waveguide at one position,at which the opening of the first split waveguide and the opening of the second split waveguide face each other., [2] Rotary joint according to claim 1, wherein the majority of the third waveguides comprises two third waveguides, wherein a third waveguide of the two third waveguides is coupled to the second split waveguide through a directional coupler of two directional couplers arranged at positions separated by 180 degrees from the second side of the rotating body of the second split waveguide, and is arranged to extend in a direction along a circumference of the second split waveguide, and another third waveguide of the two third waveguides is coupled to the second split waveguide through another directional coupler of the two directional couplers and is arranged to extend in one direction along the circumference of the second split waveguide. [3] Rotary joint according to claim 2, wherein a second end of the first waveguide is connected to a transmission circuit that outputs a signal, a second end of the second waveguide is short-circuited or terminated, a first end of the one third waveguide of the two third waveguides, which is located on one side of the one directional coupler, is short-circuited or terminated, and a second end, which extends in the one direction from the first end, is connected to a receiving circuit, and a first end of the other third waveguide of the two third waveguides, which is located on one side of the other directional coupler, is short-circuited or terminated, and a second end, which extends in one direction from the first end, is connected to a receiving circuit. [4] Rotary joint according to claim 3, wherein at a positional relationship between the stationary body and the rotating body which is a first position, a transmission path is formed in which a signal input from the transmission circuit to the first waveguide is transmitted through a first coupling section, is transmitted through a waveguide formed by the first split waveguide and the second split waveguide at a position where the opening of the first split waveguide and the opening of the second split waveguide face each other, is transmitted from the one directional coupler to the one third waveguide of the two third waveguides, and is transmitted to a second end of the one third waveguide of the two third waveguides, and when the positional relationship between the stationary body and the rotating body is a second position, a transmission path is formed in which a signal inputted from the transmission circuit to the first waveguide is transmitted through a first coupling portion transmitted through a waveguide formed by the first split waveguide and the second split waveguide at a position where the opening of the first split waveguide and the opening of the second split waveguide face each other, is transmitted from the other directional coupler to the other third waveguide of the two third waveguides, and is transmitted to a second end of the other third waveguide of the two third waveguides. [5] A rotary joint according to claim 3, wherein a signal from the receiving circuit connected to the second end of the one third waveguide of the two third waveguides and a signal from the receiving circuit connected to the second end of the other third waveguide of the two third waveguides are output in a switched or power-combined manner. [6] A rotary joint according to any one of claims 1 to 5, wherein the rotary joint has a rectangular shape in which a length of a side in the direction of the central axis is longer than a length of a side perpendicular to the central axis in a cross-sectional shape in the direction of the central axis of a waveguide path in the waveguide formed by the first divided waveguide and the second divided waveguide at a position where the opening of the first divided waveguide and the opening of the second divided waveguide face each other. [7] A rotary joint according to claim 6, wherein a length of one side in the direction of the central axis of a cross-sectional shape of the waveguide path formed by the first split waveguide and the second split waveguide is longer than 1 / 2 wavelength of a guide wavelength of a transmitted signal. [8] Rotary joint according to one of claims 1 to 5, wherein the first waveguide is arranged along an arc centered on the central axis, and the first side of the stationary body of the first waveguide faces the opening of the second split waveguide, a cross-sectional shape in a direction of the central axis of a pseudo-waveguide path in a pseudo-waveguide formed by the first waveguide and the second split waveguide at a position where the first side of the stationary body of the first waveguide and the opening of the second split waveguide face each other is a rectangle in which a length of one side in the direction of the central axis is equal to or less than 1 / 2 wavelength of a guide wavelength of a transmitted signal, the second waveguide is arranged along an arc centered on the central axis and the first side of the stationary body of the second waveguide faces the opening of the second split waveguide, and a cross-sectional shape in a central axis direction of a pseudo-waveguide path in a pseudo-waveguide formed by the second waveguide and the second split waveguide at a position where the first side of the stationary body of the second waveguide and the opening of the second split waveguide face each other is a rectangle in which a length in the central axis direction is equal to or less than 1 / 2 wavelength of a guide wavelength of a transmitted signal. [9] Rotary joint according to claim 6, wherein the first waveguide is arranged along an arc centered on the central axis, and the first side of the stationary body of the first waveguide faces the opening of the second split waveguide, a cross-sectional shape in a direction of the central axis of a pseudo-waveguide path in a pseudo-waveguide formed by the first waveguide and the second split waveguide at a position where the first side of the stationary body of the first waveguide and the opening of the second split waveguide face each other is a rectangle in which a length of one side in the direction of the central axis is equal to or less than 1 / 2 wavelength of a guide wavelength of a transmitted signal, the second waveguide is arranged along an arc centered on the central axis and the first side of the stationary body of the second waveguide faces the opening of the second split waveguide, and a cross-sectional shape in the direction of the central axis of a pseudo-waveguide path in a pseudo-waveguide formed by the second waveguide and the second split waveguide at a position where the first side of the stationary body of the second waveguide and the opening of the second split waveguide face each other is a rectangle in which a length in the direction of the central axis is equal to or less than 1 / 2 wavelength of a guide wavelength of a transmitted signal. [10] Slewing ring, comprising: a stationary body arranged along an arc centered on a central axis and including a first split waveguide having an opening that is flat on a first side of the stationary body, a first waveguide having a first end connected to a first end of the first split waveguide via a first coupling portion, and a second waveguide having a first end connected to a second end of the first split waveguide via a second coupling portion; and a rotating body comprising a second split waveguide having an annular shape, which has a shallow opening along a circumference of the same diameter as the arc in which the first split waveguide is arranged around the central axis, facing the opening of the first split waveguide on the first side of the rotating body, and a third waveguide arranged along a circumference of the second side of the rotating body facing the first side of the rotating body of the second split waveguide, and which is coupled to the second split waveguide via a plurality of directional couplers arranged at intervals along the circumference of the second split waveguide, and which is rotatable about the central axis with respect to the stationary body, in which the second split waveguide forms a waveguide with the first split waveguide at one position,at which the opening of the first split waveguide and the opening of the second split waveguide face each other., [11] The rotary joint according to claim 10, wherein the plurality of directional couplers comprises two directional couplers arranged at positions separated by 180 degrees from each other on the second side of the rotating body of the second split waveguide. [12] Rotary joint according to claim 11, wherein the second end of the first waveguide is connected to a transmission circuit that outputs a signal, the second end of the second waveguide is short-circuited or terminated, and a first end of the third waveguide is connected to a receiving circuit, and a second end of the third waveguide is short-circuited or terminated. [13] Rotary joint according to claim 12, wherein at a positional relationship between the stationary body and the rotating body which is a first position, a transmission path is formed in which a signal input from the transmission circuit to the first waveguide is transmitted through a first coupling section, is transmitted through a waveguide formed by the first split waveguide and the second split waveguide at a position where the opening of the first split waveguide and the opening of the second split waveguide face each other, and is transmitted from the one directional coupler to the first end of the third waveguide, and at the positional relationship between the stationary body and the rotating body, which is a second position, a transmission path is formed in which a signal input from the transmission circuit to the first waveguide is transmitted via a first coupling portion, is transmitted via a waveguide formed by the first split waveguide and the second split waveguide at a position where the opening of the first split waveguide and the opening of the second split waveguide face each other, and is transmitted from the other directional coupler to the first end of the third waveguide. [14] Rotary joint according to claim 12, wherein a signal from the receiving circuit connected to the first end of the third waveguide at the first position and a signal from the receiving circuit connected to the first end of the third waveguide at the second position are output in a switched manner or are output in a power-combined manner. [15] A rotary joint according to any one of claims 10 to 14, wherein the rotary joint has a rectangular shape in which a length of a side in a direction of the central axis is longer than a length of a side perpendicular to the central axis in a cross-sectional shape in the direction of the central axis of a waveguide path in the waveguide formed by the first divided waveguide and the second divided waveguide at a position where the opening of the first divided waveguide and the opening of the second divided waveguide face each other. [16] The rotary joint according to claim 15, wherein a length of one side in the direction of the central axis in a cross-sectional shape of the waveguide path formed by the first split waveguide and the second split waveguide is longer than 1 / 2 wavelength of a guide wavelength of a transmitted signal. [17] Rotary joint according to one of claims 10 to 14, wherein the first waveguide is arranged along an arc centered on the central axis, and the first side of the stationary body of the first waveguide faces the opening of the second split waveguide, a cross-sectional shape in a direction of the central axis of a pseudo-waveguide path in a pseudo-waveguide formed by the first waveguide and the second split waveguide at a position where the first side of the stationary body of the first waveguide and the opening of the second split waveguide face each other is a rectangle in which a length of one side in the direction of the central axis is equal to or less than 1 / 2 wavelength of a guide wavelength of a transmitted signal, the second waveguide is arranged along an arc centered on the central axis and the first side of the stationary body of the second waveguide faces the opening of the second split waveguide, and a cross-sectional shape in the direction of the central axis of a pseudo-waveguide path in a pseudo-waveguide formed by the second waveguide and the second split waveguide at a position where the first side of the stationary body of the second waveguide and the opening of the second split waveguide face each other is a rectangle in which a length in the direction of the central axis is equal to or less than 1 / 2 wavelength of a guide wavelength of a transmitted signal. [18] Rotary joint according to claim 15, wherein the first waveguide is arranged along an arc centered on the central axis, and the first side of the stationary body of the first waveguide faces the opening of the second split waveguide, a cross-sectional shape in a direction of the central axis of a pseudo-waveguide path in a pseudo-waveguide formed by the first waveguide and the second split waveguide at a position where the first side of the stationary body of the first waveguide and the opening of the second split waveguide face each other is a rectangle in which a length of one side in the direction of the central axis is equal to or less than 1 / 2 wavelength of a guide wavelength of a transmitted signal, the second waveguide is arranged along an arc centered on the central axis and the first side of the stationary body of the second waveguide faces the opening of the second split waveguide, and a cross-sectional shape in the direction of the central axis of a pseudo-waveguide path in a pseudo-waveguide formed by the second waveguide and the second split waveguide at a position where the first side of the stationary body of the second waveguide and the opening of the second split waveguide face each other is a rectangle in which a length in the direction of the central axis is equal to or less than 1 / 2 wavelength of a guide wavelength of a transmitted signal.

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