Waveguide Connection Structure

Abstract

To provide a waveguide connection structure that suppresses leakage of radio waves even when waveguides are spaced apart from each other in the axial direction due to tolerance.SOLUTION: A waveguide connection structure includes a spigot waveguide 1 and a socket waveguide 2. The spigot waveguide 1 includes a flange 11 extending outward in the pipe radial direction RD. The socket waveguide 2 has a socket structure 21 into which the spigot waveguide 1 can be inserted, and a stub groove 22 arranged both on the outside of a socket pipe 20 in the tube radial direction RD. The socket structure 21 includes a socket end face 210 that extends in the pipe radial direction RD and faces the end face 12 of the flange 11, and an annular socket inner peripheral surface 211 extending from the socket end face 210 along the tube axial direction AD toward the spigot waveguide 1 side and arranged outside the flange 11 in the tube radial direction RD. The stub grooves 22 each have an open first end 22a and a closed second end 22b. The electrical length EL1 from the first end 22a to the second end 22b of each of the stub grooves 22 along the tube axis direction AD is half the guide wavelength λg of the stub groove 22.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a waveguide connection structure that connects waveguides that transmit high frequencies.

[0002] In devices that use high frequencies (e.g., microwaves), such as weather radars, waveguides are used as a transmission path for radio waves. When connecting a first waveguide to a second waveguide, the first and second waveguides must be connected without any gaps. If there is a gap between the first and second waveguides, radio waves will leak from the gap. Non-Patent Document 1 is an example of a waveguide connection structure. Waveguides are generally connected by bringing the flanges of the first and second waveguides into contact with each other without any gaps, and then fastening the flanges together with fasteners such as bolts, as shown in Figures 3 and 32 of Non-Patent Document 1.

[0003] However, a waveguide is made of metal and has tolerances as a mechanical part. Even if all the waveguides constituting the transmission line are connected without gaps, a gap will occur as a tolerance between the waveguides that are butted against each other at any of the waveguide connection parts in the transmission line. This tolerance can be reduced by fastening the flanges together with a fastener, but using the fastener adds stress to the flange. Furthermore, even if the flanges are fastened with a fastener, it may be difficult to completely eliminate the gap if the tolerance is large.

[0004] When using a waveguide with restrictions such as not allowing stress to be applied to the flange, a fastener cannot be used to fasten the flange, which can result in a gap being generated between the first waveguide, which has a flange restriction, and the second waveguide connected to the first waveguide, which can cause radio wave leakage. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Nippon Foundation Grant Project, June 2002, Japan Ship Electrical Equipment Association, Communication Training Course, Ship Electrical Equipment Technology Course [Radar] Equipment Maintenance Part, "Chapter 3 Special Tubes, Semiconductors and Microwave Transmission Circuits for Radar", "3.9 Microwave Transmission Circuits", "3.9.4 Waveguides", Figure 3.32, https: / / nippon.zaidan.info / seikabutsu / 2002 / 00403 / contents / 017.htm Summary of the Invention [Problem to be solved by the invention]

[0006] The present disclosure provides a waveguide connection structure that suppresses leakage of radio waves even in a state in which the waveguides are spaced apart from each other in the tube axis direction due to tolerances. [Means for solving the problem]

[0007] a receptacle waveguide having an inlet conduit for transmitting high frequency waves and a flange extending radially outward from an open end of the receptacle conduit; a receptacle waveguide having a receptacle structure into which the receptacle waveguide can be inserted, and stub grooves arranged on both radially outward sides of the receptacle conduit, wherein the receptacle structure has a receptacle end face extending radially in the pipe and facing an end face of the flange, and an annular receptacle inner circumferential surface extending from the receptacle end face along the pipe axial direction toward the receptacle waveguide and arranged radially outward of the flange, wherein the stub grooves each have a first end opening at the receptacle end face and a second end closed within the receptacle waveguide, and an electrical length from the first end to the second end along the pipe axial direction of each stub groove is half the pipe wavelength of the stub groove. [Brief description of the drawings]

[0008] [Figure 1] 3A and 3B are perspective views showing the waveguide connection structure before and after connection in the first embodiment. [Diagram 2] 2 is a cross-sectional view taken along the line II-II in FIG. 1 and FIG. [Diagram 3]A front view of the receiving waveguide seen from a line of sight parallel to the tube axis. [Figure 4] FIG. 2 is a cross-sectional view perpendicular to the axis of a rectangular waveguide. [Diagram 5] FIG. 11 is a front view of a modified example of the inlet waveguide of the first embodiment, seen from a line of sight parallel to the tube axis. [Figure 6] FIG. 11 is a front view of a waveguide according to still another modified example of the first embodiment, as viewed in a direction parallel to the axis of the waveguide. [Figure 7] 13A and 13B are perspective views showing a waveguide connection structure according to a second embodiment before and after connection. [Figure 8] 8 is a cross-sectional view taken along line VIII-VIII in FIG. [Figure 9] FIG. 11 is a front view of the inlet waveguide of the second embodiment, seen from a line of sight parallel to the tube axis. [Figure 10] FIG. 13 is a perspective view showing another waveguide connection structure. [Figure 11] 11 is a cross-sectional view taken along the line XI-XI in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [First embodiment] Hereinafter, a waveguide connection structure according to a first embodiment of the present disclosure will be described with reference to the drawings.

[0010] As shown in Figs. 1 to 3, the waveguide connection structure of the first embodiment has an inlet waveguide 1 and a receiving waveguide 2. When the inlet waveguide 1 is inserted into the receiving waveguide 2, the positional relationship between the inlet waveguide 1 and the receiving waveguide 2 is fixed. The inlet waveguide 1 has an inlet pipe 10 for transmitting high frequency waves. The receiving waveguide 2 has a receiving pipe 20 for transmitting high frequency waves. In a connected state, the receiving pipe 20 and the inlet pipe 10 are butted against each other. In the connected state, the positional relationship between the inlet waveguide 1 and the receiving waveguide 2 is fixed. The inlet waveguide 1 and the receiving waveguide 2 are hollow metal pipes and made of conductors. The inlet waveguide 1 and the receiving waveguide 2 are electrically shorted and set to ground. The high frequency waves are transmitted through the inlet waveguide 1 and the receiving waveguide 2 from one side to the other side in the tube axis direction AD. The high frequency in this specification is radio waves of 300 MHz or more, preferably radio waves of 2 GHz or more, and more preferably radio waves of 3 GHz or more. As an upper limit, the high frequency may be, for example, radio waves of 50 GHz or less. More preferably, it may be radio waves of 40 GHz or less. The high frequency may be microwaves or millimeter waves. In this embodiment, aluminum or stainless steel is used as the conductor, but it is not limited to these as long as it is a conductor.

[0011] The pipes (insertion pipe 10, inlet pipe 20) of the first embodiment are rectangular waveguide pipes 3 having long sides 31 and short sides 32 in pipe cross section as shown in FIG. 4. The long sides 31 are parallel to each other, and the short sides 32 are parallel to each other. FIG. 2 is a cross-sectional view of the II-II portion in FIG. 1. The II-II portion cross-section is a cross section passing through the center 31s of the long sides 31 and the tube axis A1. In the pipes, an oscillating electric field is generated by a traveling wave and a reflected wave. FIG. 4 is a schematic cross-sectional view perpendicular to the tube axis A1, which is a portion where the oscillating electric field is strong in the tube axis direction AD. As shown in FIG. 4, the oscillating electric field E becomes an antinode at the portion connecting the centers 31s of the long sides 31, and is most dominant. On the other hand, the oscillating electric field E is not generated on the short sides 32. A high frequency wave is transmitted in the rectangular waveguide pipe 3 in a TE10 mode (Transverse Electric Mode), which is a fundamental mode of such a rectangular waveguide pipe 3. In the TE10 mode, the electric field is not generated in a direction parallel to the long side 31, but in a direction parallel to the short side 32. Note that modes other than the fundamental mode (TE10 mode) are not limited to this, and it is also possible to use a mode other than TE10.

[0012] As shown in Figs. 1 and 2, the inlet waveguide 1 has a flange 11 extending outward in the pipe radial direction RD from the open end of the inlet pipe 10. The flange 11 is continuously connected in the pipe circumferential direction and is annular. The flange 11 in the first embodiment is disk-shaped with the pipe axis A1 as its center, but is not limited thereto and can be modified in various ways. The end face 12 of the flange 11 in the first embodiment is parallel to the pipe radial direction RD. The end face 12 is the face of the flange 11 facing the inlet waveguide 2, and may hereinafter be simply referred to as the flange end face 12.

[0013] 1, 2 and 3, the receiving waveguide 2 has a receiving structure 21 into which the insertion waveguide 1 can be inserted. The receiving structure 21 has a receiving end face 210 extending in the pipe radial direction RD and facing the end face 12 of the flange 11, and an annular receiving inner peripheral surface 211 extending from the receiving end face 210 along the pipe axis direction AD toward the insertion waveguide 1. The receiving end face 210 extends from the open end of the receiving pipe 20 outward in the pipe radial direction and is continuously connected in the pipe circumferential direction. The receiving inner peripheral surface 211 is disposed outside the flange 11 in the pipe radial direction RD. In this way, the end face 12 of the flange 11 of the insertion waveguide 1 and the receiving end face 210 of the receiving waveguide 2 are parallel, so that both faces (12, 210) can be butted against each other and brought into surface contact. In addition, since the receiving inner peripheral surface 211 is parallel to the tube axis direction AD, the insertion waveguide 1 and the receiving waveguide 2 can be slid in parallel to the tube axis direction AD, and the end face 12 of the insertion waveguide 1 and the receiving end face 210 of the receiving waveguide 2 can be brought into contact or separated. As a result, the cumulative value of the tolerances of the multiple mechanical parts constituting the transmission line is the distance D1 between the flange end face 12 and the receiving end face 210. From the viewpoint of suppressing radio wave leakage, this distance D1 is preferably 10 mm or less. In other words, since the tolerance of the mechanical parts is a very large value of 10 mm, the degree of freedom in mechanical design of the waveguide is improved and the assembly work is facilitated.

[0014] Most of the high frequency waves passing through the inlet pipe 10 shown in FIG. 2 pass through the inlet pipe 20, but a part of the high frequency waves enters the gap S1 between the end face 12 of the flange of the inlet waveguide 1 and the inlet end face 210 of the inlet waveguide 2, and travels outward in the pipe radial direction. However, the inlet inner circumferential surface 211 covers (envelops) the flange 11 from the outside in the pipe radial direction, so that leakage of the high frequency waves toward the outside in the pipe radial direction can be suppressed. Even if there is a gap between the pipe radial outer surface 13 of the flange 11 and the inlet inner circumferential surface 211, the components of the radio waves passing through the gap S1 that travel toward the outside in the pipe radial direction RD are dominant, so that radio wave leakage from the gap between the pipe radial outer surface 13 of the flange 11 and the inlet inner circumferential surface 211 is limited. The gap between the pipe radial outer surface 13 of the flange 11 and the inlet inner circumferential surface 211 is preferably 0 mm or more and 2.0 mm or less. If this gap exceeds 2.0 mm, radio wave leakage becomes a problem, and the deterioration of the waveguide performance due to the axial misalignment of the waveguide becomes a problem. When one of the tube radial outer side surfaces 13 on both sides of the flange 11 in the tube radial direction contacts the socket inner circumferential surface 211, it is preferable that the gap between the other tube radial outer side surface 13 and the socket inner circumferential surface 211 is 2.0 mm or less. When the tube radial outer side surfaces 13 on both sides of the flange 11 in the tube radial direction are each spaced apart from the socket inner circumferential surface 211, it is preferable that the gap between each tube radial outer side surface 13 and the socket inner circumferential surface 211 is 1.0 mm or less. This is to reduce the axial misalignment of the waveguide and ensure the waveguide performance.

[0015] Furthermore, in order to reduce high frequencies in the gap between the flange end face 12 and the receiving end face 210, a stub groove 22, which will be described below, may be provided. As shown in FIG. 1 and FIG. 2, the receiving waveguide 2 has stub grooves 22 arranged on both radially outer sides of the receiving pipe 20. Each of the stub grooves 22 has a first end 22a that opens at the receiving end face 210 and a second end 22b that closes in the receiving waveguide 2. In the first embodiment, the stub grooves 22 are linearly arranged along the pair of long sides 31 of the rectangular waveguide 3. The multiple stub grooves 22 are arranged at positions sandwiching the receiving pipe 20 in a cross section where the pair of long sides 31 appear. In the first embodiment, the length of the stub groove 22 along the long side 31 is longer than the long side of the rectangular waveguide 3, but is not limited thereto. As shown in Fig. 4, since the area between the centers 31s of the long sides 31 is most dominant, it is preferable that the pair of stub grooves 22 sandwich the center 31s of the long sides 31 and its vicinity. Specifically, it is preferable that the stub grooves 22 sandwich an area Ar1 that is 24% of the maximum width W1 of the long sides 31 from at least the outer side in the tube radial direction, with the center 31s of the long sides 31 as the center. This is because 60% of the power is distributed in this 24% area Ar1. Furthermore, it is preferable that the stub grooves 22 sandwich an area Ar1 that is 36% of the maximum width W1 of the long sides 31 from at least the outer side in the tube radial direction, with the center 31s of the long sides 31 as the center. This is because 81% of the power is distributed in this 36% area Ar1.

[0016] 2, the electrical length EL1 from the first end 22a to the second end 22b of each stub groove 22 along the tube axis direction AD is half the tube wavelength λg of the stub groove 22. The tube wavelength λg of the stub groove 22 is determined according to the long side of the waveguide in a cross section perpendicular to the tube axis direction of the stub groove 22. As a result, the oscillating electric field in the stub groove 22 becomes a node (short) at the first end 22a and the second end 22b, and a portion where the oscillating electric field becomes a node (short) is formed in the gap S1 between the flange end face 12 and the receiving end face 210. As a result, it is possible to suppress leakage of the electric field toward the outside in the tube radial direction through the gap S1. Moreover, it is preferable that the stub grooves 22 are disposed closer to the inlet pipe 20 than the middle P1 between the inlet pipe 20 and the inlet inner circumferential surface 211 in the pipe radial direction RD. This is because leakage of the electric field can be suppressed more effectively when the portion where the oscillating electric field becomes a node (short) in the gap S1 between the flange end face 12 and the inlet end face 210 is closer to the inlet pipe 20. In other words, it is preferable that the stub grooves 22 are as close to the inlet pipe 20 as possible.

[0017] Furthermore, as shown in FIG. 2, even if the electrical length EL2 along the pipe diameter direction RD from the inner peripheral surface of the inlet pipe 10 to the socket inner peripheral surface 211 is an integer multiple of 1 / 2 of the free space wavelength λ0. Since it is an integer multiple, the electrical length EL2=λ0×1 / 2, λ0×2 / 2, λ0×3 / 2, ..., λ0×N / 2. N is a natural number of 1 or more. The gap S1 in the first embodiment is formed in a disk shape. The cross-sectional area of ​​the gap S1 perpendicular to the pipe axis direction AD is larger than the cross-sectional area of ​​the inlet pipe 10 perpendicular to the pipe axis direction AD, and it spreads in the pipe diameter direction, so it can be evaluated as a free space. As a result, the oscillating electric field becomes a node (short) at the socket inner peripheral surface 211 in the gap S1. In addition, the oscillating electric field becomes a node (short) near the inner peripheral surface of the inlet pipe 10 in the gap S1 (extension of the inner peripheral surface). It is possible to further suppress the leakage of radio waves through the gap S1. Furthermore, since the vicinity of the inner peripheral surface of the conduit (the inlet conduit 10, the inlet conduit 20) becomes a node (short circuit) of the oscillating electric field, deterioration of the waveguide characteristics can be suppressed.

[0018] The flange 11 of the first embodiment is restricted from being subjected to stress, and therefore the flange 11 and the inlet waveguide 2 are not fastened together with fasteners such as bolts. Instead, the pipe body forming the inlet conduit 10 is fixed to a base (not shown) with fasteners, and the inlet waveguide 2 is fixed to a base (not shown) with a fastener. This fixes the positional relationship between the inlet waveguide 1 and the inlet waveguide 2, resulting in a connected state.

[0019] <Modification> (1) In the first embodiment shown in Figs. 1 to 4, one stub groove 22 is arranged on one side of the inlet pipe 20, but this is not limited thereto. For example, as shown in Fig. 5, a plurality of (two) stub grooves 22 may be arranged on each of the outer sides of the inlet pipe 20 in the pipe radial direction RD. Two stub grooves 22 are arranged on each side of the inlet pipe 20, for a total of four stub grooves 22. This makes it possible to enhance the effect of suppressing radio wave leakage by the stub grooves. In this case, at least one stub groove 22 may be disposed closer to the inlet conduit 20 than a middle point P1 between the inlet conduit 20 and the inlet inner circumferential surface 211 in the pipe radial direction RD.

[0020] (2) In the embodiment shown in Figures 1 to 5, the socket inner circumferential surface 211 is arranged in a circular shape when viewed in a line of sight parallel to the tube axis A1, but is not limited thereto. For example, as shown in Figure 6, the socket inner circumferential surface 211 may be polygonal when viewed in a line of sight parallel to the tube axis A1.

[0021] (3) In the above embodiment, the stub groove 22 is disposed closer to the inlet pipe 20 than the middle P1 between the inlet pipe 20 and the inlet inner circumferential surface 211 in the pipe radial direction RD, but is not limited thereto. The stub groove 22 may be disposed at the middle P1, or the stub groove 22 may be disposed outside the middle P1 in the pipe radial direction RD. The closer the stub groove 22 is to the inlet pipe 20, the better the waveguide performance. The farther the stub groove 22 is from the inlet pipe 20, the slightly worse the waveguide performance. In any case, the stub groove 22 exerts the effect of reducing radio wave leakage.

[0022] (4) In the above embodiment, the electrical length EL2 is an integral multiple of 1 / 2 the free space wavelength λ0, but is not limited to this. When radio wave leakage is a concern rather than waveguide performance, the electrical length EL2 does not have to be an integral multiple of 1 / 2 the free space wavelength λ0.

[0023] [Second embodiment] (3) In the first embodiment and its modified examples shown in Figs. 1 to 6, the pipe is a rectangular waveguide 3 having a long side 31 and a short side 32 in pipe cross section, but is not limited thereto. For example, as shown in Figs. 7 to 9, a circular waveguide 103 having a circular pipe cross section may be used. As shown in Fig. 9, the stub grooves 22 are formed at positions that are symmetrical with respect to the pipe axis A1 of the receiving pipe 20 as the axis of symmetry. In a cross section (Fig. 8) passing through the pipe axis A1, each pair of stub grooves 22 is disposed at a position sandwiching the receiving pipe 20. In the example shown in Fig. 9, the stub grooves 22 are formed to be curved in an arc shape so as to follow the arc-shaped inner peripheral surface of the receiving pipe 20 when viewed from a line of sight parallel to the pipe axis A1, but are not limited thereto. The stub grooves 22 may be formed in a straight line when viewed from a line of sight parallel to the pipe axis A1, as shown in Fig. 3.

[0024] As described above, as in the embodiment shown in Figs. 1 to 9, the waveguide connection structure includes an inlet waveguide 1 having an inlet pipe 10 for transmitting high frequency waves and a flange 11 extending from an open end of the inlet pipe 10 outward in the pipe radial direction RD, a receiving pipe 20 abutting against the inlet pipe 10, a receiving structure 21 into which the inlet pipe 1 can be inserted, and a receiving waveguide 2 having stub grooves 22 arranged on both sides of the receiving pipe 20 outward in the pipe radial direction RD, and the receiving structure 21 extends in the pipe radial direction RD and is in contact with an end face 12 of the flange 11. and an annular receiving end face 210 extending from the receiving end face 210 along the tube axis direction AD toward the insertion waveguide 1 side and disposed outside the tube diameter direction RD of the flange 11, and each of the stub grooves 22 has a first end 22a opening at the receiving end face 210 and a second end 22b closed within the receiving waveguide 2, and an electrical length EL1 from the first end 22a to the second end 22b along the tube axis direction AD of each of the stub grooves 22 is half the tube wavelength λg of the stub groove 22.

[0025] In this way, since the insertion waveguide 1 can be inserted into the socket structure 21 having the socket end face 210 and the socket inner peripheral surface 211, both a state in which the socket end face 210 and the flange 11 are in contact and a state in which they are separated are permissible. Therefore, since the separated state is permissible, the tolerances of the mechanical parts that constitute the waveguides 1 and 2 can be absorbed. Furthermore, since the receiving port inner surface 211 of the receiving port waveguide 2 is structured to enclose the flange 11 of the insertion port waveguide 1 from the outside in the pipe diameter direction RD, even if a tolerance occurs between the receiving port end face 210 and the flange end face 12, leakage of radio waves toward the outside in the pipe diameter direction RD through the gap S1 can be suppressed. Furthermore, by setting the electrical length EL1 of the stub groove 22 to half the tube wavelength λg of the stub groove 22, the oscillating electric field E generated in the stub groove 22 becomes a node (short circuit) at the receptacle end face 210. By forming a portion where the oscillating electric field E becomes a node (short circuit) in the gap S1 between the receptacle end face 210 and the flange end face 12, it is possible to suppress leakage of radio waves toward the outside in the tube radial direction RD through the gap S1.

[0026] Although not particularly limited, as in the embodiment shown in Figures 1 to 9, the stub grooves 22 may each be positioned closer to the inlet pipe 20 than the midpoint P1 between the inlet pipe 20 and the inlet inner surface 211 in the pipe radial direction RD. In this way, a portion where the oscillating electric field E becomes a node (short circuit) is formed near the receiving pipe 20 in the gap S1 between the receiving end face 210 and the flange end face 12, making it possible to suppress leakage of radio waves toward the outside in the pipe diameter direction RD.

[0027] Although not particularly limited, as in the embodiment shown in Figures 1 to 9, the electrical length EL2 along the pipe diameter direction RD from the inner surface of the inlet pipe 10 to the receiving port inner surface 211 may be an integer multiple of half the free space wavelength λ0. According to this configuration, a node (short circuit) of the oscillating electric field E that may occur in the gap S1 between the inlet end face 210 and the flange end face 12 can be generated near the inner circumferential surface of the inlet conduit 10, making it possible to further suppress leakage of radio waves through the gap S1. Furthermore, because the nodes (short circuits) of the oscillating electric field E are near the inner circumferential surfaces of the inlet conduit 10 and the inlet conduit 20, deterioration of the waveguide characteristics can be suppressed.

[0028] Although not particularly limited, as in the embodiment shown in FIG. 5, a plurality of stub grooves 22 may be disposed on both outer sides of the receiving pipe 20 in the pipe radial direction RD. According to this configuration, it is possible to enhance the effect of suppressing radio wave leakage by the stub grooves 22.

[0029] Although not particularly limited, as in the embodiment shown in Figures 1 to 6, the inlet pipe 20 may be a rectangular waveguide pipe 3 having a pipe cross section with long sides 31 and short sides 32, and the stub grooves 22 may be arranged along each of the pair of long sides 31. According to this configuration, leakage of high frequency waves from the rectangular waveguide 3 can be appropriately suppressed.

[0030] Although not particularly limited thereto, as in the embodiment shown in Figures 7 to 9, the inlet pipe 20 may be a circular waveguide pipe 103 having a circular pipe cross section, and the stub grooves 22 may be formed at positions that are symmetrical with respect to the pipe axis A1 of the inlet pipe 20. According to this configuration, in the circular waveguide 103, the electric field is strongest along an arbitrary tube diameter direction RD passing through the tube axis A1, so that leakage of high frequency waves can be appropriately suppressed.

[0031] Although the embodiments of the present disclosure have been described above based on the drawings, the specific configurations should not be considered to be limited to these embodiments. The scope of the present disclosure is indicated not only by the description of the above-mentioned embodiments but also by the claims, and further includes all modifications within the meaning and scope equivalent to the claims.

[0032] The structures employed in each of the above embodiments can be employed in any of the other embodiments.

[0033] The specific configuration of each part is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present disclosure.

[0034] [Other waveguide connection structures] Other waveguide connection structures are shown in Figures 10 and 11. This waveguide connection structure is a connection structure between a pipe 503 of a first waveguide 501 and a pipe 504 of a second waveguide 502. Both the first waveguide 501 and the second waveguide 502 have screw holes 510 for connection formed in the end faces in the tube axis direction AD. Female waveguides 501 and 502 having screw holes 510 in their end faces cannot be connected together as they are. Therefore, a first spacer 521 is attached to the axial end surface of the first waveguide 501. The first spacer 521 is fastened to a screw hole 510 of the first waveguide 501 with a headed bolt. The first spacer 521 is formed with a counterbore 511 (recess) for accommodating the head of the headed bolt. The counterbore 511 is set to a depth that allows the head of the bolt to be completely accommodated. Further, a second spacer 522 is attached to an end face in the tube axis direction AD of the second waveguide 502. The second spacer 522 is fastened to a screw hole 510 of the second waveguide 502 with a headed bolt. The second spacer 522 is formed with a counterbore 511 (recess) for accommodating the head of the headed bolt. The counterbore 511 is set to a depth that allows the head of the bolt to be completely accommodated. The first spacer 521 and the second spacer 522 both have protruding parts 521a, 522a that protrude outward in the pipe radial direction RD beyond the first waveguide 501 and the second waveguide 502. Each of the protruding parts 521a, 522a has a bolt hole 512 for fastening the first spacer 521 and the second spacer 522 together. The bolt hole 512 may be a through hole or a threaded hole. The first spacer 521 and the second spacer 522 are fastened together by a fastener such as a bolt. This allows connection even with female type waveguides 501 and 502. Also, as shown in FIG. 11, when the sizes of the ducts of the first waveguide 501 and the second waveguide 502 are different, at least one of the first waveguide 501 or the second spacer 522 may be provided with a high frequency circuit conversion section. The high frequency conversion section is a step provided on the inner surface of the duct so that a duct with a cross-sectional area between the ducts 503 and 504 is interposed. This step has a λ / 4 matching structure. The electrical length along the axial direction of the step is set to one-fourth of the duct wavelength of the conversion source. The long side length in the cross section perpendicular to the axial direction of the tube is determined to be √(Z1*Z2), where Z1 is the impedance of the conversion source and Z2 is the impedance of the conversion destination. The short side length in the cross section perpendicular to the axial direction of the tube is determined according to the aspect ratio of the conversion source waveguide. [Explanation of symbols]

[0035] 1. Insertion waveguide 10 Inlet conduit 103 Circular Waveguide 11 Flange 12 Flange end face 2 Receptacle waveguide 20 Socket pipe 21 Socket structure 210 Socket end face 211 Inner surface of socket 22 Stub groove 22a 1st end 22b 2nd end 3 Rectangular waveguide λg Intra-tube wavelength λ0 free space wavelength

Claims

1. an inlet waveguide having an inlet pipe for transmitting high frequency waves and a flange extending radially outward from an open end of the inlet pipe; a receiving pipe that is abutted against the receiving pipe, a receiving structure into which the receiving pipe can be inserted, and a stub groove that is disposed on both outer sides of the receiving pipe in a pipe diameter direction; Equipped with the receiving port structure has a receiving port end surface extending in a pipe radial direction and facing an end surface of the flange, and an annular receiving port inner peripheral surface extending from the receiving port end surface along a pipe axial direction toward the insertion waveguide and disposed on the outer side of the flange in the pipe radial direction, each of the stub grooves has a first end that opens at the receiving end face and a second end that closes within the receiving waveguide; a waveguide connection structure, wherein an electrical length from the first end to the second end of each of the stub grooves along a tube axis direction is half a guide wavelength of the stub groove.

2. 2. The waveguide connection structure according to claim 1, wherein the stub grooves are each disposed on the receiving pipe side relative to a midpoint between the receiving pipe and the receiving inner peripheral surface in a pipe radial direction.

3. 3. The waveguide connection structure according to claim 1, wherein an electrical length along a pipe diameter direction from an inner peripheral surface of the insertion pipe to an inner peripheral surface of the receiving pipe is an integral multiple of half a free space wavelength.

4. 4. The waveguide connection structure according to claim 1, wherein a plurality of the stub grooves are arranged on both radially outer sides of the receiving pipe.

5. The inlet pipe is a rectangular waveguide pipe having a pipe cross section having long sides and short sides, 5. The waveguide connection structure according to claim 1, wherein the stub grooves are arranged along the long sides of the pair, respectively.

6. The inlet pipe is a circular waveguide pipe having a circular pipe cross section, 5. The waveguide connection structure according to claim 1, wherein the stub grooves are formed at positions that are symmetrical with respect to a pipe axis of the receiving pipe.

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