Coaxial-waveguide converter and waveguide

Abstract

To obtain a coaxial waveguide transducer and a waveguide including the same which suppress the residual and generation of foreign matter such as liquid droplet and dust and do not significantly affect electrical characteristics.SOLUTION: Disclosed is a coaxial waveguide transducer 101 which includes: an outer conductor 21 forming an internal space; a waveguide connection part 21J to which a waveguide 201 is connected; a coaxial connector 10 to which a coaxial line is connected; and a probe 22P connected to an inner conductor 12 of the coaxial connector 10 and protruding into the internal space. This transducer also performs transmission line conversion between the coaxial line and the waveguide. An opening 3A for drainage and dust discharge is provided at a position of the outer conductor 21 in a free fall direction in an installation state of the coaxial waveguide transducer 101.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a coaxial-waveguide converter in which a coaxial line and a waveguide are connected to convert a transmission mode, and to a waveguide including the same. [Background technology]

[0002] Coaxial-waveguide converters are used to convert the transmission mode between a coaxial line and a waveguide. Specifically, they convert the transmission mode between coaxial mode and waveguide mode and convert the impedance of the transmission line. Since the electromagnetic field distribution of the transmission wave differs between a coaxial line and a waveguide, the characteristic impedance, which indicates the ratio of electric field energy to magnetic field energy, differs depending on the transmission line. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 08-186410 Summary of the Invention [Problem to be solved by the invention]

[0004] In the discontinuous part of the characteristic impedance, a reflected wave occurs, which makes it impossible to transmit signals efficiently. In addition, the reflected wave generates a standing wave inside the waveguide, which causes fading in communication systems using waveguide antennas, significantly degrading the transmission characteristics of wireless communication.

[0005] In this way, the improvement of reflected waves is the core technology in communication systems using waveguide antennas. There are also problems when foreign objects are mixed into the coaxial waveguide converter and the waveguide. When metal pieces are mixed in, the current flows through the metal pieces, distorting the transmission mode of the waveguide, and the characteristic impedance also changes, resulting in significant reflected waves. In some cases, it may become a cutoff waveguide, resulting in total reflection. In addition, in the case of other foreign objects, those with a high ratio of air, such as foam, may not increase the reflected waves. However, foreign objects with a particularly high dielectric constant change the ratio of electric and magnetic energy in the coaxial waveguide converter and the waveguide, which also changes the characteristic impedance. In addition, in the case of liquid droplets, there is a problem of them accumulating.

[0006] 14(A) and 14(B) are partial perspective views showing the structure of the connection part between the coaxial line and the rectangular waveguide. As shown in FIG. 14(A), when the coaxial conversion part is located on the E or H plane of the waveguide, if water WA accumulates on the surface of the electric wall EW, the effective dimension from the coaxial conversion part to the electric wall EW changes because the dielectric constant of this water WA is higher than that of air. This affects the input / output characteristics between the coaxial conversion part and the waveguide, and a significant reflected wave occurs at the coaxial conversion part. Also, as shown in FIG. 14(B), when the coaxial conversion part is located on the electric wall EW, if water WA accumulates at the coaxial conversion part, the characteristic impedance changes significantly due to the presence of the water WA, and a more significant reflected wave occurs.

[0007] For this reason, it is necessary to design the coaxial-waveguide converter so that foreign matter such as water does not get inside in the first place. The area where water is most likely to get inside is the connection between the coaxial line and the waveguide. Normally, flanges are fixed together with screws to connect the waveguides, but waterproofing can be improved by inserting an O-ring between them.

[0008] However, in systems used in environments such as construction sites, it is difficult to install small screws with a screwdriver when joining flanges. In other words, on-site craftsmen routinely tighten bolts of about 10 mm (M10 bolts) in one go with an impact driver, and they have M10 bolt bits on their hands. If the flanges were designed to fit M10 bolts, they would be huge, difficult to handle, and expensive. On the other hand, they are not accustomed to handling small Phillips screws, do not have bits, and even if they are installed, they will have to tighten them in one go with an impact driver, and there is no guarantee that they will be tightened to the specified torque. When working at heights, small screws may be dropped during work, which could lead to accidents. They cannot be assembled in a factory and transported to the construction site, and it often rains during work at the construction site, and rainwater may get into the waveguide during work. The same environment is true inside tunnels and ships.

[0009] For these reasons, waterproof flanges cannot be used, and it is not possible to completely prevent the intrusion of rainwater, etc.

[0010] Furthermore, if the humidity inside the coaxial-waveguide converter and the waveguide becomes high, water droplets may form inside the coaxial-waveguide converter due to condensation.

[0011] An object of the present invention is to provide a coaxial-waveguide converter and a waveguide including the same, which suppresses the residue or generation of foreign matter such as droplets and dust and does not significantly affect electrical characteristics. [Means for solving the problem]

[0012] A coaxial-waveguide converter as an example of the present disclosure comprises an outer conductor forming an internal space, a waveguide connection portion to which a waveguide is connected, a coaxial connector to which a coaxial line is connected, and a probe connected to the inner conductor of the coaxial connector and protruding into the internal space, and performs transmission line conversion between the coaxial line and the waveguide, and comprises an opening for draining liquid and dust at a position of the outer conductor in the free fall direction when the coaxial-waveguide converter is installed.

[0013] A waveguide as an example of the present disclosure is composed of the coaxial-waveguide converter, a waveguide connected to the waveguide connection portion of the coaxial-waveguide converter, and a coaxial-waveguide converter connected to the waveguide.

[0014] According to this configuration, droplets and dust that have entered or are generated inside the coaxial-waveguide converter are discharged to the outside through the opening while the coaxial-waveguide converter is installed. Also, since the inside of the coaxial-waveguide converter is not sealed, condensation is unlikely to occur. Effect of the Invention

[0015] According to the present invention, it is possible to obtain a coaxial-waveguide converter and a waveguide including the same that suppress the residue or generation of foreign matter such as droplets and dust and does not significantly affect electrical characteristics. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view of a coaxial-waveguide converter 101 according to the first embodiment. [Diagram 2] FIG. 2 is a perspective view of the coaxial-waveguide converter 101 according to the first preferred embodiment. [Diagram 3] FIG. 3 is a perspective view showing a state in which the central conductor support 25 has been removed together with two screws and one nut from the state shown in FIG. [Figure 4] FIG. 4 is a perspective view showing a state in which the end plate 24 has been removed from the state shown in FIG. [Diagram 5] FIG. 5 is a perspective view showing a state in which the foam body 23 has been removed from the state shown in FIG. [Figure 6] FIG. 6 is a perspective view showing a state in which the outer conductor 21 has been removed from the state shown in FIG. [Figure 7] FIG. 7 is a cross-sectional view of a portion of the coaxial-waveguide converter 101 and the waveguide. [Figure 8]Fig. 8(A) is a diagram showing the electromagnetic field distribution in a plane perpendicular to the propagation direction of the TEM mode propagating through the coaxial line portion 1. Fig. 8(B) is a diagram showing the electromagnetic field distribution of the TM01 mode propagating through the waveguide 201, where the upper part shows the electromagnetic field distribution in a plane perpendicular to the propagation direction and the lower part shows the electromagnetic field distribution in a plane parallel to the propagation direction. [Figure 9] FIG. 9 is a front view showing the configuration of a waveguide 301 including the structure at the end of the waveguide 201 shown in FIG. [Figure 10] 10(A) and 10(B) are diagrams showing changes in the transmission efficiency S21 and the reflectance S11 over time in a state in which water is poured into the coaxial-waveguide converter 101 to thoroughly wet the inner surface and the water ingress prevention portion 27 of the coaxial-waveguide converter 101 and then the two coaxial-waveguide converters 101 are placed opposite each other. [Figure 11] 11(A) and 11(B) are diagrams showing changes in the transmission efficiency S21 and the reflectance S11 following FIG. 10(B). [Figure 12] FIG. 12 is a diagram showing changes in the transmission efficiency S21 and the reflectance S11 following FIG. 11(B). [Figure 13] FIG. 13 is a cross-sectional view showing a coaxial-waveguide converter 102 according to the second embodiment and a part of a waveguide 201 connected thereto. [Figure 14] 14(A) and 14(B) are partial perspective views showing the structure of a connection portion between a coaxial line and a rectangular waveguide. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] First Embodiment In the first embodiment, a coaxial-waveguide converter and a waveguide in which the electromagnetic wave propagation direction of the waveguide and the free fall direction are in a parallel relationship will be illustrated.

[0018] 1 and 2 are perspective views of a coaxial-waveguide converter 101 according to a first embodiment of the present invention. Figures 3 to 6 are explanatory perspective views of the coaxial-waveguide converter 101 with components thereof sequentially removed.

[0019] The coaxial-waveguide converter 101 includes an outer conductor 21 and a coaxial connector 10. The outer conductor 21 includes a waveguide connection portion 2C to which a waveguide is connected. The coaxial-waveguide converter 101 also includes an end plate 24 and a central conductor support 25 fixed to the end plate 24.

[0020] In this embodiment, the coaxial connector 10 is a coaxial plug (female contact), and a coaxial jack (male contact) provided at the end of a coaxial line (not shown) is connected to this coaxial plug. A flange portion 21F is formed on the waveguide connection portion 2C, and a flange portion formed at the end of a waveguide (not shown) is connected to this flange portion 21F.

[0021] The coaxial-waveguide converter 101 performs transmission line conversion between a coaxial line connected to the coaxial connector 10 and a waveguide connected to the waveguide connection portion 2C.

[0022] 1 with the central conductor support 25 removed together with two screws and one nut. As will be described in detail later, one end of the central conductor 22 is supported by the central conductor support 25. An opening 3A having an inner diameter larger than the diameter of the central conductor 22 is formed in the center of the end plate 24.

[0023] Fig. 4 is a perspective view showing a state in which end plate 24 has been removed from the state shown in Fig. 3. Choke groove 21C is formed in the end face of outer conductor 21. Insulating resin foam 23 is provided in choke groove 21C.

[0024] Fig. 5 is a perspective view of the connector with foam 23 removed from the state shown in Fig. 4. Foam 23 is a member that fills choke groove 21C, and prevents water droplets and the like from entering choke groove 21C. Foam 23 is an insulator or dielectric material, and radio waves can propagate through it.

[0025] The foam 23 does not fill the entire choke groove 21C, but is partially hollowed out. In this example, four places are hollowed out in a fan shape. This makes it possible to lower the effective dielectric constant of the choke groove 21C. In other words, the provision of the foam 23 does not increase the effective dielectric constant in the choke groove 21C, and the foam 23 does not have a negative effect on the electromagnetic field.

[0026] FIG. 6 is a perspective view of the state shown in FIG. 5 with the outer conductor 21 removed. The center of the central conductor 22 is connected to the inner conductor 12 of the coaxial connector 10 via a screw 26. The outer conductor 21 is formed with an air hole for inserting a screwdriver for screwing the screw 26 into the inner conductor 12 of the coaxial connector 10. The cap 28 is a member for closing the air hole after the screw 26 is screwed into the inner conductor 12 of the coaxial connector 10. The cap 28 is a member that is breathable but blocks water droplets. A part of the central conductor 22 is a probe 22P that is tapered toward the waveguide connection part. A water ingress prevention part 27 is provided around the inner conductor 12 of the coaxial connector 10.

[0027] 7 is a cross-sectional view of a portion of the coaxial-waveguide converter 101 and the waveguide. The outer conductor 11 of the coaxial connector 10 is connected to the outer conductor 21 of the coaxial-waveguide converter 101. A flange portion 21F is formed at the waveguide connection portion 21J of the coaxial-waveguide converter 101. With a flange portion 201F formed at the end of the waveguide 201 facing this flange portion 21F, the flange portion 21F and the flange portion 201F are screwed together with bolts and nuts (not shown).

[0028] The coaxial-waveguide converter 101 includes a coaxial connector 10, a coaxial line section 1 to which the coaxial connector 10 is connected, a transmission mode conversion section 2 that converts the transmission mode between the coaxial line section 1 and a waveguide connection section 2C, and a choke structure section 3.

[0029] The main part of the coaxial line section 1 is composed of a cylindrical portion of the outer conductor 21 and a central conductor 22 disposed at the center of the outer conductor 21. The lower end 21H2 of the coaxial line section 1 is horn-shaped and tapers toward the opening 3A. The coaxial line section 1 has an opening 3A for draining liquid and dust at a position in the free fall direction when the coaxial-waveguide converter 101 is installed (in the choke structure section shown later).

[0030] In the coaxial line portion 1, the connection position of the inner conductor 12 of the coaxial connector relative to the central conductor 22 (the distance from the lower end portion 21H2 of the coaxial line portion 1) may be determined so that the impedance of the line of the coaxial line portion 1 matches the characteristic impedance of the coaxial connector 10 and the coaxial cable connected thereto.

[0031] The transmission mode converter 2 is composed of an inner surface 21H1 of an outer conductor 21 and a probe 22P. The inner surface 21H1 of the outer conductor 21 of the transmission mode converter 2 has a horn shape whose inner diameter gradually tapers toward the opening 3A. The probe 22P also has a shape that tapers toward the waveguide connection portion.

[0032] The main portion of the choke structure 3 is composed of an opening 3A formed in the outer conductor 21, a choke groove 21C formed in the outer conductor 21, and an end plate .

[0033] The central conductor 22 is supported at two points, that is, the central conductor support 25 and the inner conductor 12 of the coaxial connector. As a result, the central conductor 22 is disposed at the center of the coaxial line portion 1 and the transmission mode converter 2.

[0034] The electrical length from the coaxial line section 1 to the short-circuit end (depth end) A of the choke groove 21C of the choke structure 3 is approximately λg / 2, where λg is the in-guide wavelength. In this example, the electrical length from the coaxial line section 1 to the choke groove 21C of the choke structure 3 is approximately λg / 4, and the electrical length from the center of the choke groove 21C to the outer periphery is also approximately λg / 4. Waves ride on the above-mentioned λg / 2 length portion, but because it is short-circuited at the short-circuit end A of the choke groove 21C, the lower end 21H2 of the coaxial line section 1 acts as an equivalent short-circuit end C (electrical wall).

[0035] A water-repellent surface treatment layer is formed on the inner surfaces (the inner surface of the outer conductor 21) of the transmission mode conversion section 2, the coaxial line section 1, and the choke structure section 3. This surface treatment layer is, for example, a water-repellent film with a contact angle of water of 90° or more. This surface treatment layer is also a layer in which a fine uneven pattern is formed by roughening.

[0036] In addition, a corrosion prevention treatment layer is formed on the inner surfaces (inner surface of the outer conductor 21) of the transmission mode converter 2, the coaxial line portion 1, and the choke structure portion 3. The outer conductor 21 is made of copper, and the corrosion prevention treatment layer is, for example, a zinc plating film, a tin plating film, or the like. The surface treatment layer is formed on the surface of the corrosion prevention treatment layer.

[0037] Even if foreign matter such as droplets or dust remains or is generated inside the waveguide 201 or the coaxial-waveguide converter 101 for some reason, these foreign matter will naturally fall and be discharged to the outside from the opening 3A. Since there are no places where foreign matter can accumulate in the waveguide 201, the transmission mode converter 2, the coaxial line section 1, and the choke structure 3, the foreign matter will quickly fall and be discharged to the outside from the opening 3A.

[0038] In particular, since a water-repellent surface treatment layer is formed on the inner surface of the outer conductor 21, liquid droplets such as water droplets slide off and are quickly discharged to the outside. Also, since a corrosion prevention treatment layer is formed on the inner surface of the outer conductor 21, corrosion caused by liquid droplets such as water droplets is prevented.

[0039] As shown in Fig. 4, since insulating resin foam 23 is provided in choke groove 21C, the above-mentioned foreign matter does not spread and remain inside choke groove 21C. As already described, foam 23 does not fill the entire inside of choke groove 21C, but is composed of a central portion surrounding central conductor 22, an outer peripheral portion in contact with the outer periphery of choke groove 21C, and spoke-like portions connecting the central portion and the outer peripheral portion. Therefore, the inside of choke groove 21C can be kept at a low effective dielectric constant.

[0040] The water ingress prevention portion 27 provided between the inner conductor 12 of the coaxial connector 10 and the outer conductor 21 of the coaxial-waveguide converter 101 is an insulating resin foam. In this manner, since the water ingress prevention portion 27 is formed between the inner conductor 12 of the coaxial connector 10 and the outer conductor 21 of the coaxial-waveguide converter 101, water is prevented from entering the inside of the coaxial-waveguide converter 101 through this portion. Conversely, water temporarily accumulated inside the coaxial-waveguide converter 101 is prevented from leaking from the mounting portion of the coaxial connector 10 to the coaxial connector side.

[0041] Moreover, the ventilation hole 21V formed in the outer conductor 21 of the coaxial-waveguide converter 101 functions not only as an opening for inserting a screwdriver for screwing the screw 26 into the inner conductor 12 of the coaxial connector 10, but also as a ventilation hole. In other words, the ventilation hole 21V is provided with the cap 28, which is a member that is breathable but blocks water droplets, and therefore functions effectively to dehumidify the internal space 21S of the coaxial-waveguide converter 101 and the waveguide 201.

[0042] Fig. 8(A) is a diagram showing the electromagnetic field distribution in a plane perpendicular to the propagation direction of the TEM mode propagating through the coaxial line section 1. Fig. 8(B) is a diagram showing the electromagnetic field distribution of the TM01 mode propagating through the waveguide 201, where the upper part shows the electromagnetic field distribution in a plane perpendicular to the propagation direction, and the lower part shows the electromagnetic field distribution in a plane parallel to the propagation direction. In these figures, the solid lines show the direction and distribution of the electric field, and the dashed lines show the direction and distribution of the magnetic field.

[0043] The transmission mode conversion unit 2 shown in FIG. 7 converts between the TEM mode and the TM01 mode.

[0044] Here, the change in electrical characteristics depending on the presence or absence of the choke structure 3 and the gap size of the opening 3A is shown. In Table 1, "with choke structure" is the characteristic of the coaxial-waveguide converter 101 of this embodiment shown in FIG. 7, and "without choke structure" is the characteristic of a coaxial-waveguide converter as a comparative example having a structure without choke groove 21C shown in FIG. 7. Table 1 also shows the actual measured values ​​of the transmission efficiency (S21 of S parameters) when two coaxial-waveguide converters 101 are connected facing each other and the gap size of the opening 3A is changed. In Table 1, the minimum gap value is represented by standard value d.

[0045] As shown in Table 1, without the choke structure, the larger the gap dimension of opening 3A, the greater the leakage of radio waves, but with the choke structure 3, the leakage of radio waves from opening 3A is reduced, and even if the gap dimension is increased, the decrease in transmission efficiency is small. Therefore, the gap dimension of opening 3A can be increased, resulting in high liquid and dust discharge performance.

[0046] [Table 1]

[0047] Fig. 9 is a front view showing the configuration of waveguide 301 including the structure at the end of waveguide 201 shown in Fig. 7. Waveguide 201 has flange portions 201F at both ends, with coaxial-waveguide converter 101 connected to one end and coaxial-waveguide converter 102 connected to the other end. This waveguide is placed vertically, for example, inside a building under construction or inside a ship.

[0048] The structure of the other coaxial-waveguide converter 102 is basically the same as that of the coaxial-waveguide converter 102. However, the coaxial-waveguide converter 102 does not have an opening corresponding to the opening 3A of the coaxial-waveguide converter 101, and is waterproofed. Therefore, no foreign matter will enter the inside of the coaxial-waveguide converter 102 through the opening.

[0049] 9, a waveguide antenna is configured by forming a slot array in a waveguide 201. This antenna is used for wireless communication, for example, in buildings at construction sites or on ships.

[0050] Next, we will show the recovery characteristics of the transmission efficiency over time after the coaxial-waveguide converter is submerged in water.

[0051] 10(A), 10(B), 11(A), 11(B) and 12 are diagrams showing the changes in transmission efficiency (S-parameter S21) and reflectivity (S-parameter S11) over time in a state in which water is poured into the coaxial-waveguide converter 101 to thoroughly wet the inner surface and water ingress prevention portion 27 of the coaxial-waveguide converter 101 and then two coaxial-waveguide converters 101 are placed opposite each other.

[0052] Figure 10(A) shows the characteristics before immersion in water, and Figure 10(B) shows the characteristics immediately after 20 ml of water was poured in to thoroughly wet the inner surface of coaxial-waveguide converter 101 and water intrusion prevention portion 27. Figure 11(A) shows the characteristics 12 hours after immersion in water, and Figure 11(B) shows the characteristics 24 hours after immersion in water. Figure 12 shows the characteristics 36 hours after immersion in water. The following can be seen from these results.

[0053] Immediately after entering the water, the reflectivity S11 is -1.7 dB (total reflection state), making communication impossible. After 12 hours have passed, the transmission efficiency S21 becomes -3 dB and communication becomes possible. After 24 hours, the transmission efficiency S21 becomes -0.6 dB, which is almost the normal state. After 36 hours, the transmission efficiency S21 becomes -0.4 dB and returns to the normal state.

[0054] The results of this experiment show that the time during which communication is not possible (total reflection) is limited, and that communication is restored once the rainfall stops.

[0055] Furthermore, even if an experiment is conducted with the water ingress prevention section 27 (foam) fully wet, the electrical characteristics of the coaxial-waveguide converter return to the specified characteristics, so if the water ingress prevention section 27 is water-repellent, the recovery time will be even shorter.

[0056] In the figures shown above, the circles and arcs are shown as polygons for convenience of data processing, but in reality they are circular. Alternatively, they may be polygonal.

[0057] Second Embodiment In the second embodiment, a coaxial waveguide converter in which the electromagnetic wave propagation direction in the waveguide and the free fall direction are perpendicular to each other will be illustrated.

[0058] FIG. 13 is a cross-sectional view showing a coaxial-waveguide converter 102 according to the second embodiment and a part of a waveguide 201 connected thereto.

[0059] The coaxial-waveguide converter 102 includes an outer conductor 21 that defines an internal space 21S, a waveguide connection portion 21J to which a waveguide 201 is connected, a coaxial connector 10 to which a coaxial line is connected, and a probe 22P that is connected to the inner conductor of the coaxial connector 10 and protrudes into the internal space 21S.

[0060] A flange portion 21F is formed at waveguide connection portion 21J of coaxial-waveguide converter 102. With flange portion 201F formed at the end of waveguide 201 facing this flange portion 21F, flange portion 21F and flange portion 201F are screwed together with bolts and nuts (not shown).

[0061] The coaxial-waveguide converter 102 includes a choke structure 3. The outer conductor 21 includes an opening 3A for draining liquid and dust at a position in the direction of free fall when the coaxial-waveguide converter 102 is installed.

[0062] In the choke structure 3, a choke groove 21C is formed by an opening having a conical surface 21H on the lower surface of the internal space 21S of the outer conductor 21, and a disk-shaped space expanding radially from that position. The electrical length from the midpoint of the conical surface 21H to the short-circuit end (depth end) A of the choke groove 21C is approximately λg / 2. A wave rides on this λg / 2 length portion, but since it is short-circuited at the short-circuit end A of the choke groove 21C, the midpoint of the conical surface 21H acts as an equivalent short-circuit end C (electrical wall).

[0063] The conical surface 21H is a tapered portion that tapers toward the opening 3A. In this embodiment, the center line of the conical surface 21H overlaps with the center line of the probe 22P.

[0064] The opening 3A is provided at the position of an equivalent open end B that prevents leakage of radio waves.

[0065] As in the example shown in the first embodiment, the inner surface of the outer conductor is provided with a water-repellent surface treatment layer and a corrosion prevention treatment layer.

[0066] The probe 22P also serves as the inner conductor of the coaxial connector 10. A water ingress prevention portion 27 having water repellency and preventing water ingress is provided around the probe 22P.

[0067] In the internal space 21S, transmission mode conversion between the TEM mode and the TM01 mode occurs in the vicinity of the probe 22P and at the probe 22P.

[0068] The equivalent short-circuit end C on the upper surface of the choke structure 3 is equivalent to the same potential as the inner surface of the outer conductor 21 and is a short-circuit surface, so that the opening 3A does not affect the TEM mode and the TM01 mode.

[0069] Even if, for some reason, foreign matter such as droplets or dust remains or is generated inside the waveguide 201 or the coaxial-waveguide converter 102, these foreign matter will naturally fall and be discharged to the outside from the opening 3A. Even if water droplets naturally fall due to condensation on the probe 22P, the water droplets will be quickly discharged to the outside from the opening 3A.

[0070] Finally, the present invention is not limited to the above-described embodiment. Appropriate modifications and changes are possible by those skilled in the art. The scope of the present invention is indicated by the claims, not the above-described embodiment. Furthermore, the scope of the present invention includes modifications and changes from the embodiments within the scope of the claims and the equivalent scope.

[0071] For example, the "circular waveguide" in the present invention refers to a waveguide in which an electromagnetic field in a circular waveguide mode is generated, and is not necessarily limited to a perfect circle. For example, the cross section of a plane perpendicular to the axis may be a polygon.

[0072] In addition, in each of the figures shown above, a coaxial-waveguide converter that connects a waveguide that propagates electromagnetic waves in TM01 mode and a waveguide that is configured with this coaxial-waveguide converter and a waveguide are shown, but the electromagnetic waves that propagate through the waveguide are not limited to the TM01 mode. For example, a rectangular waveguide may be used to propagate electromagnetic waves in various modes such as the TE10 mode, TE11 mode, and TM11 mode. [Explanation of symbols]

[0073] A…Short circuit end B…Equivalent open end C: Equivalent short circuit end EW…Electric wall WA...Water 1…Coaxial line section 2...Transmission mode conversion section 3. Choke structure 3A…Opening 10...Coaxial connector 11...Outer conductor of coaxial connector 12...Inner conductor of coaxial connector 21...Outer conductor 21C…Choke groove 21F…Flange section 21H…conical surface 21H1: Inner surface of the outer conductor 21 of the transmission mode conversion unit 2 21H2: Lower end of coaxial line portion 1 21J…Waveguide connection 21S…interior space 21V…Ventilation port 22...Center conductor 22P…Probe 23...Foam 24...End plate 25...Center conductor support 26...Bis 27…Water entry prevention part 28…Cap 101, 102... Coaxial waveguide converter 201...Waveguide 201F…Flange part 301...waveguide

Claims

1. A coaxial-waveguide converter comprising: an outer conductor that defines an internal space; a waveguide connection portion to which a waveguide is connected; a coaxial connector to which a coaxial line is connected; and a probe that is connected to an inner conductor of the coaxial connector and protrudes into the internal space, the coaxial-waveguide converter performing transmission line conversion between the coaxial line and the waveguide, an opening for draining liquid and dust is provided at a position of the outer conductor in a free fall direction when the coaxial-waveguide converter is installed, and a water-repellent surface treatment layer is provided on an inner surface of the outer conductor; Coaxial waveguide converter.

2. A coaxial-waveguide converter comprising: an outer conductor forming an internal space; a waveguide connection portion to which a waveguide is connected; a coaxial connector to which a coaxial line is connected; and a probe connected to the inner conductor of the coaxial connector and protruding into the internal space, the coaxial-waveguide converter performing transmission line conversion between the coaxial line and the waveguide, the outer conductor has an opening for draining liquid and dust at a position in a free fall direction when the coaxial-waveguide converter is installed, and has a vent hole on a surface other than the free fall direction that allows air to pass but not water to pass, Coaxial waveguide converter.

3. A coaxial-waveguide converter comprising: an outer conductor forming an internal space; a waveguide connection portion to which a waveguide is connected; a coaxial connector to which a coaxial line is connected; and a probe connected to the inner conductor of the coaxial connector and protruding into the internal space, the coaxial-waveguide converter performing transmission line conversion between the coaxial line and the waveguide, an opening for draining liquid and dust is provided at a position of the outer conductor in a free fall direction when the coaxial-waveguide converter is installed, and a tapered portion is provided on an inner surface of the outer conductor which is tapered in a direction toward the opening; Coaxial waveguide converter.

4. A coaxial-waveguide converter comprising: an outer conductor forming an internal space; a waveguide connection portion to which a waveguide is connected; a coaxial connector to which a coaxial line is connected; and a probe connected to the inner conductor of the coaxial connector and protruding into the internal space, the coaxial-waveguide converter performing transmission line conversion between the coaxial line and the waveguide, an opening for draining liquid and dust is provided at a position of the outer conductor in a free fall direction when the coaxial-waveguide converter is installed; a coaxial line section to which the coaxial connector is connected, and a transmission mode conversion section for converting a transmission mode between the coaxial line section and the waveguide connection section, the coaxial line section being composed of a central conductor and the outer conductor which are electrically connected to the probe, the transmission mode conversion section being composed of the probe and the outer conductor, and the outer conductor of the transmission mode conversion section being provided with a tapered portion; Coaxial waveguide converter.

5. A coaxial-waveguide converter comprising: an outer conductor forming an internal space; a waveguide connection portion to which a waveguide is connected; a coaxial connector to which a coaxial line is connected; and a probe connected to the inner conductor of the coaxial connector and protruding into the internal space, the coaxial-waveguide converter performing transmission line conversion between the coaxial line and the waveguide, an opening for draining liquid and dust is provided at a position of the outer conductor in a free fall direction when the coaxial-waveguide converter is installed; a coaxial line section to which the coaxial connector is connected, and a transmission mode conversion section for converting a transmission mode between the coaxial line section and the waveguide connection section, the coaxial line section being composed of a central conductor and the outer conductor which are conductive to the probe, the transmission mode conversion section being composed of the probe and the outer conductor, and the probe being tapered in a direction toward the waveguide connection section, Coaxial waveguide converter.

6. A coaxial-waveguide converter comprising: an outer conductor forming an internal space; a waveguide connection portion to which a waveguide is connected; a coaxial connector to which a coaxial line is connected; and a probe connected to the inner conductor of the coaxial connector and protruding into the internal space, said coaxial-waveguide converter performing transmission line conversion between the coaxial line and the waveguide, an opening for draining liquid and dust is provided at a position of the outer conductor in a free fall direction when the coaxial-waveguide converter is installed; The upper part of the opening is an equivalent open end that prevents leakage of radio waves, a coaxial line section to which the coaxial connector is connected, a transmission mode conversion section for converting a transmission mode between the coaxial line section and the waveguide connection section, and a central conductor support for supporting a central conductor, the coaxial line section being composed of the central conductor and the outer conductor which are electrically connected to the probe, the transmission mode conversion section being composed of the probe and the outer conductor, and the central conductor support being provided at the equivalent open end, Coaxial waveguide converter.

7. 6. The coaxial-waveguide converter according to claim 1, wherein an upper portion of the opening is an equivalent open end that prevents leakage of radio waves.

8. 8. The coaxial-waveguide converter according to claim 6, wherein the equivalent open end is formed of a choke structure having a short-circuited end at a position approximately ½ guide wavelength away from the inner surface of the outer conductor.

9. 9. The coaxial-waveguide converter according to claim 1, wherein an inner surface of the outer conductor has a corrosion prevention treatment layer.

10. 10. The coaxial-waveguide converter according to claim 1, further comprising a water-repellent water-blocking portion that blocks water from entering around an inner conductor of the coaxial connector.

11. A waveguide comprising: the coaxial-waveguide converter according to claim 1 ; and a waveguide connected to the waveguide connection portion of the coaxial-waveguide converter.

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