Waveguide

Abstract

To provide a waveguide having a second waveguide constructed by containing a resin molding, capable of suppressing the generation of a structure failure in a part between a second wave hole and a choke groove.SOLUTION: A first waveguide and a second waveguide 20 are assembled in a state where an electromagnetic wave can transmit in a first wave hole and a second wave hole 21. In the second wave hole 21, an open part of one surface 20a that faces the first waveguide from the second waveguide 20 has a round corner polygonal shape or a circular shape. The second waveguide 20 is constructed so that a metal skin film is arranged to a resin molding material. A choke groove 22 is formed to a circumference of the second wave hole 21. The choke groove 22 is formed so that a length L between a wall surface 21a of the second wave hole 21 and an inner wall surface 22a on the second wave hole 21 side in the choke groove 22 becomes constant along a peripheral direction of the second wave hole 21.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to waveguides. [Background technology]

[0002] Conventionally, for example, Patent Document 1 proposes a waveguide that transmits a high-frequency electromagnetic field. Specifically, this waveguide includes a first waveguide made of a wiring board or the like and having a first waveguide hole formed therein, and a second waveguide made of a metal and having a second waveguide hole formed therein. The waveguide is configured by joining the first waveguide and the second waveguide so that the first waveguide hole and the second waveguide hole communicate with each other.

[0003] Furthermore, in this waveguide, if a gap occurs between the first and second waveguides, a choke groove is formed in the first waveguide, substantially surrounding the first waveguide hole, so as to prevent the electromagnetic field from leaking through the gap. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5094871 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, in order to reduce the number of processing steps and the weight, the inventors have considered configuring the second waveguide to include a resin molded product such as plastic, and forming a choke groove in the second waveguide that substantially surrounds the second waveguide. However, according to the inventors' studies, it has been confirmed that, depending on the shape of the second waveguide and the shape of the choke groove, there is a possibility that a structural defect such as collapse of the portion located between the second waveguide and the choke groove may occur.

[0006] The present disclosure aims to provide a waveguide having a second waveguide including a resin molded product, which can suppress the occurrence of structural defects in a portion between a second waveguide hole and a choke groove. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, the waveguide comprises a first waveguide (10) having a first waveguide hole (11) formed therein, and a second waveguide (20) that is assembled to the first waveguide with a predetermined gap (g) therebetween and has a second waveguide hole (21) formed therein, the first and second waveguides being assembled in a state in which electromagnetic waves can be transmitted through the first and second waveguide holes, and the second waveguide hole is formed on one surface (2 The opening of the second waveguide (0a) is made into a rounded polygonal shape or a circle, the second waveguide is constructed by disposing a metal coating (201) on a resin molding (200), and a choke groove (22) is formed around the second waveguide, and the choke groove is formed such that the length (L) between a wall surface (21a) of the second waveguide and an inner wall surface (22a) of the choke groove on the second waveguide side is constant along the circumferential direction of the second waveguide.

[0008] According to this, when a resin molded product having a second waveguide and a choke groove is manufactured by pouring molten resin into a mold, the resin easily flows uniformly between the wall surface of the second waveguide and the inner wall surface of the choke groove, which makes it possible to suppress the occurrence of structural defects such as collapse of the portion between the wall surface of the second waveguide and the inner wall surface of the choke groove on the second waveguide side.

[0009] Note that the reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and specific components described in the embodiments described below. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a perspective view of a waveguide according to the first embodiment. [Figure 2A] FIG. 2 is a cross-sectional view taken along line IIA-IIA in FIG. [Figure 2B] FIG. 4 is an enlarged cross-sectional view of one surface side of a second waveguide. [Diagram 3] FIG. 4 is a plan view of one surface of a second waveguide. [Figure 4] 1 is a schematic cross-sectional view of a millimeter wave radar constructed using the waveguide of the first embodiment. FIG. [Diagram 5] FIG. 11 is a diagram illustrating the relationship between frequency and pass characteristics. [Figure 6] 13 is a diagram showing the relationship between the length between a second waveguide hole and an inner wall surface of a choke groove and the reflection characteristics. FIG. [Figure 7] 13 is a diagram showing the relationship between the length between a second waveguide hole and an inner wall surface of a choke groove and the reflection characteristics. FIG. [Figure 8] 13 is a diagram showing the relationship between the length between a second waveguide hole and an inner wall surface of a choke groove and transmission characteristics. FIG. [Figure 9] 13 is a diagram showing the relationship between the length between a second waveguide hole and an inner wall surface of a choke groove and the reflection characteristics. FIG. [Figure 10] 13 is a diagram showing the relationship between the sum of the length between a second waveguide hole and an inner wall surface of a choke groove and the depth of the choke groove, and the transmission characteristics. FIG. [Figure 11] FIG. 4 is a diagram for explaining dimensions of a second waveguide in the first embodiment. [Figure 12] FIG. 11 is a diagram for explaining dimensions of a second waveguide of the comparative example. [Figure 13] FIG. 11 is a plan view of one surface side of a second waveguide in a modified example of the first embodiment. [Figure 14] FIG. 11 is a plan view of one surface side of a second waveguide in a modified example of the first embodiment. [Figure 15] FIG. 11 is a plan view of one surface side of a second waveguide in a modified example of the first embodiment. [Figure 16] 13 is a plan view of one surface of a second waveguide in the second embodiment. [Figure 17] 11 is a diagram showing the relationship between the angle of the arc portion and the transmission characteristic. FIG. [Figure 18] FIG. 11 is a plan view of one surface side of a second waveguide in a modified example of the second embodiment. [Figure 19]FIG. 11 is a perspective view of a second waveguide in the third embodiment. [Figure 20] FIG. 11 is a cross-sectional view of a waveguide according to a third embodiment. [Figure 21] 6 is a diagram showing the relationship between the transmission characteristics and the length between the outer wall surface of the choke groove and the first end face ... second end face. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be denoted by the same reference numerals.

[0012] (First embodiment) A waveguide 1 according to a first embodiment will be described with reference to the drawings. The waveguide 1 according to the present embodiment is suitable for use in transmitting a high-frequency electromagnetic field, for example.

[0013] 1 and 2A, the waveguide 1 includes a first waveguide 10 and a second waveguide 20, which are assembled together. For ease of understanding, Fig. 1 shows a diagram in which the first waveguide 10 and the second waveguide 20 are widely separated from each other so that the shapes of a second waveguide hole 21 and a choke groove 22, which will be described later, can be seen.

[0014] The first waveguide 10 is composed of a printed circuit board, a wiring board, or the like having one surface 10a and the other surface 10b, and a first waveguide hole 11 is formed penetrating between the one surface 10a and the other surface 10b. The first waveguide hole 11 is formed by a drill or the like, and the opening has substantially the same shape as the opening of a second waveguide hole 21 described below. Although not shown in the figure, a metal coating of about 1 μm containing aluminum, copper, silver, or the like is disposed in the first waveguide hole 11.

[0015] The second waveguide 20 is in the form of a plate having one surface 20a and the other surface 20b, and is configured by coating a resin molding 200 with a metal film 201, as shown in Fig. 2B. As shown in Figs. 1 and 2A, the second waveguide 20 is formed with a second waveguide hole 21 penetrating between the one surface 20a and the other surface 20b, and a choke groove 22 is formed around the second waveguide hole 21 in the one surface 20a.

[0016] The resin molded product 200 is made of a resin material such as ABS (short for Acrylonitrile Butadiene Styrene) or PPE (short for Poly Phenylene-Ether). The metal coating 201 is made of aluminum, copper, silver, etc., and has a thickness of about 1 μm. The second waveguide 20 is made by pouring molten resin into a mold and solidifying it to form the resin molded product 200 in which the second waveguide hole 21 and the choke groove 22 are formed, and then disposing the metal coating 201 on the entire surface of the resin molded product 200 by sputtering, vapor deposition, etc. In FIG. 2A, the metal coating 201 is omitted because the thickness of the metal coating 201 is sufficiently thin compared to the resin molded product 200. The metal coating 201 in the second waveguide 20 of this embodiment is formed on the entire surface of the resin molded product 200. Therefore, each surface of the second waveguide 20, including the first surface 20a and the second surface 20b, is made of a metal coating 201.

[0017] Here, the shapes of the second waveguide hole 21 and the choke groove 22 of the second waveguide 20 in this embodiment will be described with reference to Fig. 3. In the following description, one direction along the planar direction of one face 20a of the second waveguide 20 is defined as the X-axis direction, a direction perpendicular to the X-axis direction and along the planar direction of one face 20a is defined as the Y-axis direction, and a normal direction to one face 20a is defined as the Z-axis direction.

[0018] 3, the second waveguide hole 21 has an opening on the one surface 20a side in a polygonal shape with rounded corners. In other words, the opening on the one surface 20a side of the second waveguide hole 21 has a shape that has no corners. In other words, the opening on the one surface 20a side of the second waveguide hole 21 has a shape in which the corners of the polygonal shape have curvature. Examples of the rounded polygonal shape include a rectangular shape with rounded corners and a hexagonal shape with rounded corners.

[0019] In this embodiment, the opening of the second waveguide hole 21 is rectangular with rounded corners, with its long side parallel to the X-axis direction and its short side parallel to the Y-axis direction, and with the ends of two opposing sides along the X-axis direction connected by an arc. Below, an example will be described in which the opening of the second waveguide hole 21 is polygonal with rounded corners, but the second waveguide hole 21 may have any shape without corners, such as a circle. In this case, a circle includes not only a perfect circle, but also an ellipse.

[0020] In this embodiment, the choke groove 22 is formed in a frame shape so as to surround the second waveguide 21. The choke groove 22 is formed so that the length L between the wall surface 21a of the second waveguide 21 and the inner wall surface 22a of the choke groove 22 on the second waveguide 21 side is constant along the circumferential direction of the second waveguide 21. In other words, the choke groove 22 is formed so that the inner wall surface 22a is a surface obtained by uniformly translating the wall surface 21a of the second waveguide 21 outward. In other words, if the portion between the second waveguide 21 and the choke groove 22 is the wall portion 23, the choke groove 22 is formed so that the thickness of the wall portion 23 is constant along the circumferential direction of the second waveguide 21. Note that "along the circumferential direction of the second waveguide 21" can also be referred to as "along the axis passing through the center of the second waveguide 21." In addition, the reason why the second waveguide hole 21 has a shape without corners as described above is to ensure that the length L between the wall surface 21a of the second waveguide hole 21 and the inner wall surface 22a of the choke groove 22 is constant along the circumferential direction of the second waveguide hole 21.

[0021] The above is the shape of the second waveguide 21 and the choke groove 22 in this embodiment. When manufacturing the resin molded product 200 in which the second waveguide 21 and the choke groove 22 are formed, a mold in which protrusions or the like are arranged at the portions corresponding to the second waveguide 21 and the choke groove 22 is prepared, and molten resin is poured into this mold and solidified. In this case, in this embodiment, the length L between the wall surface 21a of the second waveguide 21 and the inner wall surface 22a of the choke groove 22 is constant along the circumferential direction of the second waveguide 21. Therefore, when pouring the molten resin, the resin is more likely to flow uniformly between the wall surface 21a of the second waveguide 21 and the inner wall surface 22a of the choke groove 22, compared to a case in which the length L between the wall surface 21a of the second waveguide 21 and the inner wall surface 22a of the choke groove 22 varies along the circumferential direction of the second waveguide 21. Therefore, it is possible to prevent structural defects such as the collapse of the portion between the wall surface 21a of the second waveguide hole 21 and the inner wall surface 22a of the choke groove 22 (that is, the wall portion 23).

[0022] 2A, the first waveguide 10 and the second waveguide 20 are assembled in a state in which the other surface 10b of the first waveguide 10 and the one surface 20a of the second waveguide 20 face each other in the Z-axis direction. Specifically, the first waveguide 10 and the second waveguide 20 are assembled in a state in which a predetermined gap g is formed in advance between the other surface 10b of the first waveguide 10 and the one surface 20a of the second waveguide 20 in order to deal with warping due to differences in thermal expansion between the first waveguide 10 and the second waveguide 20. The first waveguide 10 and the second waveguide 20 are assembled in a state in which electromagnetic waves can be transmitted to the first waveguide hole 11 and the second waveguide hole 21, for example, so that the center of the other surface 10b side of the first waveguide hole 11 faces the center of the one surface 20a side of the second waveguide hole 21. The first waveguide 10 and the second waveguide 20 are assembled, for example, in a cross section different from that shown in Fig. 2, by forming an engaging recess in the first waveguide 10 and forming an engaging protrusion in the second waveguide 20, and inserting the engaging protrusion into the engaging recess. In this case, the first waveguide 10 and the second waveguide 20 are assembled with the length of the gap g adjusted by appropriately adjusting the depth of the engaging recess and the height of the engaging protrusion.

[0023] The above is the configuration of the waveguide 1 in this embodiment. Next, a more detailed configuration and effects will be described while explaining how to use the waveguide 1.

[0024] The above-described waveguide 1 is used, for example, to configure a millimeter wave radar in which a plurality of antennas are arranged, and as shown in Fig. 4, one surface 10a of the first waveguide 10 is joined to a semiconductor module 30 having an antenna portion 31 via a joining member 40 such as solder. Note that the semiconductor module 30 is configured to include, for example, a wiring board 32 on which the antenna portion 31 is formed, and a molded resin 33 that seals the wiring board 32 so that the antenna portion 31 is exposed.

[0025] In this embodiment, the first waveguide 10 and the second waveguide 20 are assembled in a state where a predetermined gap g is maintained, and therefore, there is a possibility that an electromagnetic field may leak from this gap g. However, the second waveguide 20 is formed with the choke groove 22 as described above. This makes it possible to suppress deterioration of the transmission characteristics.

[0026] Specifically, the inventors have conducted extensive research into the pass characteristic S21 as a transmission characteristic of the waveguide 1, and obtained the results shown in Fig. 5. Fig. 5 is a diagram showing the relationship between frequency and pass characteristic S21, in which the input side is the first waveguide 10 and the output side is the second waveguide 20. Note that the pass characteristic S21 and reflection characteristic S11 described below each have the input side as the first waveguide 10 and the output side as the second waveguide 20.

[0027] Fig. 5 shows the results when the electrically effective wavelength λ is 3.92 mm (i.e., λ = 3.92 mm). As shown in Fig. 3, Fig. 5 shows the results when the length L (i.e., the thickness of the wall portion 23) between the wall surface 21a of the second waveguide hole 21 and the inner wall surface 22a of the choke groove 22 is 0.3 mm ≒ 0.0765 λ, and the width W between the inner wall surface 22a and the outer wall surface 22b of the choke groove 22 is 0.475 mm ≒ 0.121 λ. Fig. 5 shows the results when the depth d of the choke groove 22 is 1.4 mm ≒ 0.35 λ, and the gap g is 0.1 mm. In the following, the length between wall surface 21a of second waveguide hole 21 and inner wall surface 22a of choke groove 22 (i.e., thickness of wall portion 23) is simply referred to as length L, and the width between inner wall surface 22a and outer wall surface 22b of choke groove 22 is simply referred to as width W. The comparative example waveguide in Fig. 5 is a waveguide in which second waveguide 20 is made of metal and the length L and width W are 1 / 4 of the effective wavelength λ (i.e., 3.92 mm). The waveguide without a choke groove in Fig. 5 is a waveguide in which second waveguide 20 is made of metal and no choke groove 22 is formed.

[0028] 5, in the case of a waveguide without choke grooves 22, it is confirmed that energy leaks of about -0.5 dB at an operating frequency of 76.5 GHz, which is generally used in millimeter wave radar. However, in the waveguide 1 of this embodiment, it is confirmed that there is almost no leakage at 76.5 GHz, and it is confirmed that it is possible to obtain a transmission characteristic S21 that is almost the same as that of the waveguide of the comparative example. In other words, it is confirmed that even if the second waveguide 20 is configured to include the resin molding 200, it is possible to obtain a transmission characteristic S21 that is the same as that when the second waveguide 20 is configured from metal.

[0029] According to the study by the present inventors, as shown in Figs. 6 to 9, it has been confirmed that even if the width W is changed, the influence on the reflection characteristic S11 and the transmission characteristic S21 is small. Therefore, the width W may be appropriately changed depending on the ease of molding the resin molding 200 constituting the second waveguide 20. However, the wider the width W, the wider the band of the region where the reflection characteristic S11 is small. Therefore, it is preferable that the width W is appropriately changed depending on the application. It is said that the reflection characteristic S11 can fully meet the current requirements if it is -20 dB or less.

[0030] The inventors further conducted extensive research into the relationship between the sum of the length L and the depth d and the transmission characteristic S21, and obtained the results shown in Fig. 10. Note that Fig. 10 shows the results when the representative operating frequency is 76.5 GHz and the electrically effective wavelength λ is 3.92 mm (i.e., λ=3.92 mm).

[0031] As shown in FIG. 10, it is confirmed that the deterioration of the transmission characteristic S21 can be sufficiently suppressed if the sum of the length L1 and the depth d is within the range of 0.2 to 0.7 λ of the operating frequency. Here, in the past, the length L was generally set to ¼ λ and the depth d was set to ¼ λ. However, according to the study by the present inventors, it was confirmed that the deterioration of the transmission characteristic S21 can be sufficiently suppressed if the sum of the length L1 and the depth d is within the range of 0.2 to 0.7 λ of the operating frequency, as described above. Therefore, in the second waveguide 20 of this embodiment, the values ​​of the length L and the depth d can be appropriately changed as long as the sum of the length L and the depth d is within the range of 0.2 to 0.7 λ of the operating frequency.

[0032] For example, as shown in FIG. 11 and FIG. 12, the second waveguide hole 21 has a short side length a of 1.55 mm at the opening and a width W of 0.475 mm. As shown in FIG. 11, the second waveguide hole 21 of the present embodiment has a rounded rectangular opening. On the other hand, as shown in FIG. 12, the second waveguide hole 21 of the comparative example has a rectangular opening. In the present embodiment, the length L is 0.3 mm (i.e., 0.07 λ) as shown in FIG. 11, and the length L of the comparative example waveguide is 0.98 mm (i.e., 1 / 4 λ). However, in the present embodiment, the depth d is appropriately adjusted so that the sum of the length L and the depth d is 0.2 to 0.7 λ. In this case, the length of the outer wall surfaces 22b facing each other in the Y-axis direction in the choke groove 22 is 3.1 mm in FIG. 11 and 4.4 mm in FIG. 12. That is, in this embodiment, the length in the Y-axis direction can be shortened by approximately 30%, and the size in the Y-axis direction can be reduced.

[0033] Although not particularly shown, choke groove 22 can also be designed to have a longer length L, so long as the sum of length L and depth d is 0.2 to 0.7λ. When choke groove 22 is formed so that length L is longer, wall portion 23 becomes thicker. For this reason, when length L is increased, the strength of wall portion 23 can be improved and the manufacturing process can be simplified.

[0034] According to the present embodiment described above, the second waveguide 20 includes the resin molded product 200. The choke groove 22 is formed such that the length L between the wall surface 21a of the second waveguide 21 and the inner wall surface 22a of the choke groove 22 is constant along the circumferential direction of the second waveguide 21. For this reason, when the resin molded product 200 in which the second waveguide 21 and the choke groove 22 are formed is manufactured by pouring molten resin into a mold, the resin easily flows uniformly between the wall surface 21a of the second waveguide 21 and the inner wall surface 22a of the choke groove 22. Therefore, it is possible to suppress the occurrence of structural defects such as collapse of the portion between the wall surface 21a of the second waveguide 21 and the inner wall surface 22a of the choke groove 22 on the second waveguide 21 side (i.e., the wall portion 23).

[0035] (1) In the present embodiment, the choke groove 22 is formed in a frame shape so as to surround the second waveguide hole 21. This makes it easier to prevent electromagnetic waves from leaking from the gap g.

[0036] (2) In this embodiment, the sum of the length L and the depth d of the second waveguide 20 is set to 0.2 to 0.7λ of the operating frequency. Therefore, when the length L is shortened within a range in which the sum of the length L and the depth d is 0.2 to 0.7λ of the operating frequency, the size of the second waveguide 20 can be reduced. On the other hand, when the length L is lengthened within a range in which the sum of the length L and the depth d is 0.2 to 0.7λ of the operating frequency, the strength of the wall portion 23 can be improved and the manufacturing process can be simplified.

[0037] (Modification of the first embodiment) A modified example of the first embodiment will be described. As described in the first embodiment, the second waveguide hole 21 can be appropriately modified in detail as long as the opening on the one surface 20a side does not have corners and the thickness of the wall portion 23 is constant. For example, as shown in FIG. 13, the second waveguide hole 21 may be rectangular with rounded corners, have two opposing sides along the X-axis direction and two opposing sides along the Y-axis direction, and be shaped such that these sides are connected by arcs. Also, as shown in FIG. 14, the second waveguide hole 21 may be circular. In these cases, the choke groove 22 is formed around the second waveguide hole 21 so that the thickness of the wall portion 23 is constant.

[0038] As described in the first embodiment above, since the width W of the choke groove 22 is unlikely to affect the transmission characteristics, the choke groove 22 may have a shape in which the outer wall surface 22b bulges toward the opposite side to the second waveguide hole 21, as shown in FIG. 15.

[0039] Second embodiment A second embodiment will be described. This embodiment is different from the first embodiment in that the shape of the choke groove 22 is changed. As the rest is similar to the first embodiment, a description thereof will be omitted here.

[0040] 16, the choke groove 22 of this embodiment has a notch 220 formed therein. Specifically, as in the first embodiment, the opening of the second waveguide hole 21 on one surface 20a has a rounded rectangular shape with its longer side in the X-axis direction. The choke groove 22 is formed in a portion facing the second waveguide hole 21 in the Y-axis direction, but is not formed in a portion facing the second waveguide hole 21 in the X-axis direction. In other words, the cutout 220 is formed so that the choke groove 22 does not have a portion facing the second waveguide hole 21 in the X-axis direction.

[0041] The above is the configuration of the waveguide 1 in this embodiment. Such a waveguide 1 is used to configure a millimeter wave radar, for example, as in the first embodiment. In this case, it is known that when a transmission wave is transmitted to the waveguide 1 in Te10 mode, the transmission wave is likely to leak in the gap g between the first waveguide 10 and the second waveguide 20 along the Y-axis direction (i.e., a direction perpendicular to the long side direction of the second waveguide hole 21). For this reason, the choke groove 22 in this embodiment is formed in a portion facing the second waveguide hole 21 in the Y-axis direction, which is a portion from which the transmission wave is likely to leak.

[0042] The inventors have thoroughly studied the size of the notch 220 and the transmission characteristic S21, and obtained the results shown in Fig. 17. Fig. 17 shows the results when the representative operating frequency is 76.5 GHz and the electrically effective wavelength λ is 3.92 mm (i.e., λ = 3.92 mm). Fig. 17 also shows the results when, as shown in Fig. 16, the long side length X along the X-axis direction of the second waveguide hole 21 is 1.4 mm, the short side length Y along the Y-axis direction is 1.15 mm, and the radius A of the arc connecting the two opposing sides extending along the X-axis direction is 0.575 mm. 17 shows the results when the width W is 0.475 mm ≒ 0.121λ, the length L is 0.3 mm ≒ 0.0765λ, and the length R between the center between the ends of two opposing sides along the X-axis direction in second waveguide hole 21 and the center between inner wall surface 22a and outer wall surface 22b of the portion that forms an arc along the arc shape in second waveguide hole 21 is 1.1125 mm ≒ 0.283λ, as shown in Fig. 16. Fig. 17 shows the results when the angle θ of the portion that forms an arc along the arc in second waveguide hole 21 in choke groove 22 is set to angle θ.

[0043] 17, the larger the angle θ, the closer the pass characteristic S21 is to 0. That is, the closer the pass characteristic S21 is to 0, the larger the portion of the choke groove 22 that surrounds the second waveguide hole 21. Since the pass characteristic S21 is −0.5 dB when there is no choke groove as described above with reference to FIG. 5, it is preferable to select an angle θ at which the pass characteristic S21 is −0.5 dB or greater according to the depth d.

[0044] According to the present embodiment described above, the second waveguide 20 is configured to include the resin molding 200, and the thickness of the wall portion 23 is constant, so that the same effects as those of the first embodiment can be obtained.

[0045] (1) As in this embodiment, the choke groove 22 does not have to be shaped to completely surround the second waveguide hole 21. In such a case, it is preferable that the choke groove 22 is formed in a portion where the transmission wave is likely to leak from the gap g. Furthermore, in such a second waveguide 20, the choke groove 22 is not formed to completely surround the second waveguide hole 21. Therefore, when forming the resin molding 200 that constitutes the second waveguide 20, the flow of resin can be easily controlled, and the manufacturing process can be simplified.

[0046] (Modification of the second embodiment) A modified example of the second embodiment will be described below. In the second embodiment, the choke groove 22 may be formed only in one portion facing the second waveguide hole 21 in the X-axis direction, in addition to the portion facing the second waveguide hole 21 in the Y-axis direction, as shown in Fig. 18 .

[0047] Third embodiment A third embodiment will be described. In this embodiment, a recess is formed in the second waveguide 20 in comparison with the first embodiment. As the rest is similar to the first embodiment, a description thereof will be omitted here.

[0048] As shown in Fig. 19 and Fig. 20, in the waveguide 1 of this embodiment, a recess 24 is formed on one surface 20a of the second waveguide 20 at a portion located on the opposite side to the second waveguide hole 21 with the choke groove 22 in between. The second waveguide hole 21 and the choke groove 22 are formed so as to open at a protrusion 25 on the inner edge side constituted by the formation of the recess 24. In this embodiment, the recess 24 is formed in a rectangular frame shape, and the protrusion 25 has a rectangular tip surface. Specifically, the recess 24 is formed so that the protrusion 25 has an end surface along the X-axis direction.

[0049] First waveguide 10 and second waveguide 20 are assembled in a state in which a predetermined gap g is maintained between other surface 10b of first waveguide 10 and the tip surface of protruding portion 25 of second waveguide 20.

[0050] According to this, by forming the recess 24, the amount of resin required for the resin molding 200 for forming the second waveguide 20 can be reduced.

[0051] Here, the inventors of the present invention have studied the transmission characteristic S21 of such a waveguide 1 as follows. That is, the end face of the protrusion 25 along the X-axis direction is defined as the first end face 25a, and the end face along the Y-axis direction is defined as the second end face 25b. The length between the outer wall surface 22b of the choke groove 22 and the first end face 25a is defined as the length by, and the length between the outer wall surface 22b of the choke groove 22 and the second end face 25b is defined as the length bx. The inventors of the present invention have studied the lengths bx and by and the transmission characteristic S21 in detail, and obtained the results shown in FIG. 21. Note that FIG. 21 shows the results when a typical operating frequency is 76.5 GHz, the electrically effective wavelength λ is 3.92 mm (i.e., λ=3.92 mm), and the transmission wave is transmitted in the Te10 mode. Note that, as described above, it is known that when the transmission wave is in the Te10 mode, the transmission wave is likely to leak in the Y-axis direction.

[0052] As shown in Fig. 21, it is confirmed that the pass characteristic S21 does not change much when the length bx is changed, but the pass characteristic S21 improves as the length by is longer. When the operating frequency is 76.5 GHz, the pass characteristic S21 in the absence of the choke groove 22 is -0.5 dB as described above with reference to Fig. 5, so it is preferable that the length by is 0.2λ or more, which is closer to 0 than -0.5 dB.

[0053] According to the present embodiment described above, the second waveguide 20 is formed using the resin molding 200, and the thickness of the wall portion 23 is constant, so that the same effects as those of the first embodiment can be obtained.

[0054] (1) In this embodiment, a recess 24 is formed on one surface 20a of second waveguide 20 at a portion located on the opposite side of second waveguide hole 21 across choke groove 22. This makes it possible to reduce the amount of resin required for resin molding 200 for forming second waveguide 20. Also, in this embodiment, length by is set to 0.2λ or more. This makes it possible to suppress deterioration of pass characteristic S21.

[0055] (Modification of the third embodiment) A modified example of the third embodiment will be described. In the third embodiment, the configuration in which the amount of resin is reduced by forming the recess 24 has been described. In this case, the amount of resin may be further reduced by removing other portions. For example, the second waveguide 20 may be configured to have excess portions hollowed out (i.e., removed) so that the amount of resin in the portion located around the second waveguide hole 21 along the axial direction of the second waveguide hole 21 is constant. In such a configuration, the resin flow can be more easily controlled when the resin molded product 200 is manufactured by pouring molten resin into a mold.

[0056] (Other embodiments) Although the present disclosure has been described based on the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also encompasses various modifications and modifications within the equivalent range. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure.

[0057] For example, in the first to third embodiments, the first waveguide 10 may be formed with a choke groove 22 similar to that in the second waveguide 20.

[0058] In the first to third embodiments, the first waveguide 10 may be configured in the same manner as the second waveguide 20, by arranging the metal coating 201 on the resin molding 200.

[0059] The above-described embodiments may be combined as appropriate. For example, the second embodiment may be combined with the third embodiment, and the second waveguide 20 may have the protrusion 25 formed by forming the recess 24.

[0060] [Disclosure of the Invention] The present disclosure described above can be understood from the following viewpoints, for example. [First viewpoint] A waveguide comprising: A first waveguide (10) having a first waveguide hole (11) formed therein; a second waveguide (20) that is assembled to the first waveguide with a predetermined gap (g) therebetween and that has a second waveguide hole (21) formed therein; the first waveguide and the second waveguide are assembled in a state in which electromagnetic waves can be transmitted through the first waveguide hole and the second waveguide hole, The second waveguide hole has an opening in a surface (20a) of the second waveguide facing the first waveguide, the opening having a rounded polygonal shape or a circular shape, The second waveguide is configured by disposing a metal film (201) on a resin molding (200), and a choke groove (22) is formed around the second waveguide hole, The choke groove is a waveguide formed such that a length (L) between a wall surface (21a) of the second waveguide hole and an inner wall surface (22a) of the choke groove on the second waveguide hole side is constant along the circumferential direction of the second waveguide hole.

[0061] [Second viewpoint] The waveguide according to the first aspect, wherein the choke groove is in the shape of a frame surrounding the second waveguide hole.

[0062] [Third Perspective] the second waveguide hole has an opening on one surface facing the first waveguide in a rounded polygonal shape, and has a shape whose long side direction is one direction in a planar direction of the one surface, The waveguide according to a first aspect, wherein the choke groove is formed to face the second waveguide hole in a direction intersecting the long side direction in a planar direction of the one surface.

[0063] [Fourth viewpoint] The waveguide according to any one of the first to third aspects, wherein a sum of a length between a wall surface of the second waveguide hole and an inner wall surface (22a) of the choke groove facing the second waveguide hole, and a depth (d) of the choke groove is 0.2 to 0.7λ, where λ is the wavelength of the electromagnetic wave to be transmitted.

[0064] [Fifth viewpoint] a recess (24) is formed in a portion of a surface of the second waveguide facing the first waveguide on the opposite side to the second waveguide hole across the choke groove, and a portion of an inner edge side of the recess is formed as a protrusion (25); the second waveguide hole has an opening on one surface facing the first waveguide in a rounded polygonal shape, and has a shape whose long side direction is one direction in a planar direction of the one surface, The protrusion has an end surface (25a) extending along the long side direction, The waveguide according to any one of the first to fourth aspects, wherein a length (by) between the end face and an outer wall surface (22b) of the choke groove located on the opposite side to the second waveguide hole side is 0.2λ or more, where λ is the wavelength of the electromagnetic wave to be transmitted. [Explanation of symbols]

[0065] 10 First Waveguide 11 First waveguide hole 20 Second Waveguide 20a one side 21 Second waveguide hole 21a Wall 22 Choke groove 22a Inner wall 200 Resin moldings 201 Metallic Film

Claims

1. A waveguide comprising: A first waveguide (10) having a first waveguide hole (11) formed therein; a second waveguide (20) that is assembled to the first waveguide with a predetermined gap (g) therebetween and has a second waveguide hole (21) formed therein; the first waveguide and the second waveguide are assembled in a state in which electromagnetic waves can be transmitted through the first waveguide hole and the second waveguide hole, The second waveguide hole has an opening in a surface (20a) of the second waveguide facing the first waveguide, the opening being shaped like a rounded polygon or a circle, The second waveguide is configured by disposing a metal film (201) on a resin molding (200), and a choke groove (22) is formed around the second waveguide hole, The choke groove is a waveguide formed such that a length (L) between a wall surface (21 a) of the second waveguide hole and an inner wall surface (22 a) of the choke groove on the second waveguide hole side is constant along a circumferential direction of the second waveguide hole.

2. The waveguide according to claim 1 , wherein the choke groove is formed in a frame shape surrounding the second waveguide hole.

3. the second waveguide hole has an opening on one surface facing the first waveguide in a rounded polygonal shape, and has a shape whose long side direction is one direction in a planar direction of the one surface, The waveguide according to claim 1 , wherein the choke groove is formed so as to face the second waveguide hole in a direction intersecting with the long side direction in a planar direction of the one surface.

4. 4. The waveguide according to claim 1, wherein a sum of a length between a wall surface of the second waveguide hole and an inner wall surface of the choke groove on the second waveguide hole side, and a depth (d) of the choke groove is set to 0.2 to 0.7λ, where λ is the wavelength of the electromagnetic wave to be transmitted.

5. a recess (24) is formed in a portion of a surface of the second waveguide facing the first waveguide, the portion being opposite the second waveguide hole across the choke groove, and a portion of an inner edge side of the recess is formed as a protrusion (25); the second waveguide hole has an opening on one surface facing the first waveguide in a rounded polygonal shape, and has a shape whose long side direction is one direction in a planar direction of the one surface, The protrusion has an end surface (25a) extending along the long side direction, 4. The waveguide according to claim 1, wherein a length (by) between the end face and an outer wall surface (22b) of the choke groove located on the opposite side to the second waveguide hole side is set to be 0.2λ or more, where λ is the wavelength of the electromagnetic wave to be transmitted.

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