JP2005192038A - Heat insulation waveguide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a small heat insulation waveguide with satisfactory insulation performance, short length in the transmitting direction and the weight of which is reduced. <P>SOLUTION: A radio wave through hole 14 is opened in the board thickness direction of a dielectric board 13. A metal layer 16 is supported on an internal surface of the radio wave through hole 14 of the dielectric board 13 and all the surfaces of both board surfaces of the dielectric board 13. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heat insulating waveguide used for heat insulation in a microwave or millimeter wave waveguide circuit.

  In a waveguide circuit that feeds high-power microwaves such as radar, the microwaves are converted into heat when passing through a lossy circuit, so the circuits that are thermally limited are placed close together At times, “cooling” for heat-generating circuits and “heat insulation” to prevent heat from adversely affecting adjacent circuits are indispensable technologies.

  For example, FIGS. 16 to 18 show the configuration of a conventional waveguide circuit, FIG. 16 is a circuit diagram of the conventional waveguide circuit, FIG. 17 is a perspective view of the conventional waveguide circuit, and FIG. These are the perspective views of the heat insulation waveguide used as the conventional connection waveguide.

  In this waveguide circuit, as shown in FIG. 16, a waveguide type microwave amplifier 3 and a waveguide circulator 4 are connected in cascade via a connection waveguide 5 between terminals 1 and 2 at both ends. ing. In this case, the heat generated by the microwaves consumed by the dummy load 6 of the waveguide circulator 4 due to the loss of the waveguide circulator 4 and the reflection from the terminal 2 is generated in the waveguide microwave amplifier 3. Since this is transmitted to cause an increase in thermal noise, gain fluctuations, and life deterioration, for example, forced cooling such as water cooling or air cooling is usually applied to a circuit that generates heat (in this case, the waveguide circulator 4 and the dummy load 6). A mechanism was provided.

  However, when the forced cooling mechanism is provided, there is a problem that not only the apparatus becomes large, such as the installation of a water pipe and a cooling fan, but also disadvantageous in terms of cost.

  Therefore, as shown in FIG. 17, it has been proposed to use a heat insulating waveguide 5A made of a material having a heat insulating effect as the connection waveguide 5 for the purpose of thermally blocking the heat generating circuit and the adjacent circuit. Yes. The heat insulating waveguide 5A has a length L in the transmission direction. On one side of the heat insulating waveguide 5A, a waveguide type microwave amplifier 3 having a rectangular radio wave passage hole 7 having a long side A and a short side B is connected. A waveguide circulator 4 is connected to the opposite side of the heat insulating waveguide 5A.

 The effect of such a heat insulating waveguide 5A will be described. Here, in order to simplify the description, the reflected wave from the terminal 2 in FIG. The waveguide circulator 4 generates heat due to its high-frequency loss, but this heat is transmitted to the waveguide-type microwave amplifier 3 via the heat insulating waveguide 5A made of stainless steel having low thermal conductivity. Is done.

  As an example, the effect of the heat insulating waveguide 5A made of 3 GHz stainless steel will be described with reference to FIG. The long side A of the radio wave passage hole 8 of the heat insulating waveguide 5A is 96 mm, the short side B is 27 mm, and the external dimensions of the waveguide are the long side X is 130 mm, the short side Y is 60 mm, and the length L is 70 mm. When the thermal conductivity of stainless steel is 27 [W / (m · K)] and the heat transfer amount is 100 W, a temperature difference of 50 K can be provided by the heat insulating waveguide 5A. That is, when the temperature of the end surface of the heat insulating waveguide 5A on the waveguide circulator 4 side is 80 ° C., the temperature of the end surface of the heat insulating waveguide 5A on the side of the waveguide type microwave amplifier 3 can be suppressed to 30 ° C.

  As described above, although the thermal effect can be obtained by using the heat insulating waveguide 5A, the stainless steel or the like constituting the heat insulating waveguide 5A is difficult to process, is costly, and is large and heavy. Have the following problems.

  As described above, the heat insulating waveguide 5A according to the conventional technique has the following problems because it is made of a metal having low thermal conductivity.

(A) As a metal having low thermal conductivity, an iron-based material is generally selected from its availability, but the workability is poor and the cost is high.

(B) A metal having low thermal conductivity generally has a large specific gravity and is heavy.

(C) Even if a metal having low thermal conductivity is used, in order to obtain a sufficient heat insulating effect, it is necessary to sufficiently lengthen the heat insulating waveguide 5A, and an increase in size is inevitable.

(D) When impedance matching is performed using the heat insulating waveguide 5A, it is necessary to prepare a metal post or metal iris as a matching element in the heat insulating waveguide 5A. Not going to.

 As a heat insulating waveguide 5A for solving such problems, a structure shown in FIG. 19 has been proposed (see Patent Document 1).

 In this heat insulating waveguide 5A, a metal layer 10 is supported on the inner surface of a dielectric tube 9 such as plastic or ceramics, and the end surface of the flange portion 11 at the end of the dielectric tube 9 is also connected to the metal layer 10 to be metal. The layer 12 is provided.

The heat insulating waveguide 5A using such a dielectric tube 9 has an advantage that the heat insulating performance is remarkably improved as compared with the heat insulating waveguide 5A using a metal having low thermal conductivity.
JP 59-74704 (FIG. 2)

  However, the heat insulating waveguide 5A using the dielectric tube 9 also has a problem in that the length in the transmission direction is increased, the size is increased, a large installation area is required, and the weight is increased.

  An object of the present invention is to provide a small heat-insulating waveguide that has good heat insulating performance, is short in the transmission direction, and is lightweight.

  The configuration of the present invention that achieves the above object is as follows.

  In the heat insulating waveguide of the present invention, a radio wave passage hole is formed in the thickness direction of the dielectric plate, and both of the inner surface of the radio wave passage hole and the entire surface of both plates of the dielectric plate or a part of the radio wave passage hole are connected. A metal layer is supported on the plate surface.

  In this case, the size of the radio wave passage hole can be made smaller than the diameter of the waveguide to be connected.

  The heat insulating waveguide of the present invention has a radio wave passage hole in the thickness direction of the dielectric plate, and a metal layer on the entire plate surface of the dielectric plate or a part of both plate surfaces connected to the radio wave passage hole. The dielectric plate is provided with a plurality of through holes in the thickness direction at predetermined intervals in the peripheral portion along the inner wall of the radio wave passage hole, and both plate surfaces of the dielectric plate are formed by conductors in each through hole. The metal layers are electrically connected so as to have the same potential.

  Furthermore, in the heat insulating waveguide according to the present invention, the metal layer is supported on the peripheral portion of the dielectric plate excluding the corresponding void portions on both plate surfaces, and the dielectric plate is provided on the peripheral portion of the void portion. A large number of through holes are provided in the plate thickness direction at predetermined intervals, and the metal layers on both surfaces of the dielectric plate are electrically connected by conductors in each through hole so as to equalize the potential. To do.

  In this case, it is preferable that an impedance matching metal pattern is provided on the plate surface of the dielectric plate in the void portion so as to be connected to the metal layer on the plate surface of the dielectric plate.

  Moreover, it is preferable that the metal layer of each heat insulation waveguide has the thickness of 5 times or more with respect to the penetration thickness of the high frequency current of a use frequency band.

  As described above, the heat insulating waveguide of the present invention uses a dielectric plate and has a radio wave passage hole in its thickness direction, and the entire inner surface of the radio wave passage hole and both surfaces of the dielectric plate or the radio wave. Since the metal layer is supported on a part of both plate surfaces connected to the passage hole, it is possible to obtain a small heat-insulating waveguide with good heat insulation performance, short length in the transmission direction, and light weight. Further, since the heat insulating waveguide can be manufactured by diverting a normal printed circuit board manufacturing technique, the processability is easy and the cost can be greatly reduced.

  In this case, if the size of the radio wave passage hole is made smaller than the diameter of the connected waveguide, a matching portion is added to the heat insulating waveguide itself when impedance matching with the connected waveguide is required. Can be easily matched.

  Further, the heat insulating waveguide of the present invention uses a dielectric plate, opens a radio wave passage hole in the thickness direction of the dielectric plate, and covers both plate surfaces of the dielectric plate or a part of both plate surfaces connected to the radio wave passage hole. The dielectric plate is provided with a large number of through holes in the thickness direction at predetermined intervals around the inner wall of the radio wave passage hole in the dielectric plate, and both conductors of the dielectric plate are formed by conductors in each through hole. Since the metal layers on the plate surfaces are electrically connected so as to have the same potential, it is possible to obtain a small heat-insulating waveguide with good heat insulation performance, short length in the transmission direction, and light weight. Further, since the heat insulating waveguide can be manufactured by diverting a normal printed circuit board manufacturing technique, the processability is easy and the cost can be greatly reduced.

  Furthermore, the heat insulating waveguide of the present invention uses a dielectric plate to support a metal layer on the peripheral portion of the dielectric plate excluding the corresponding voids on both plate surfaces. A large number of through-holes are provided in the plate thickness direction at predetermined intervals around the void, and the metal layers on both sides of the dielectric plate are electrically connected by the conductor in each through-hole so that the potentials are equal. Therefore, it is possible to obtain a small heat-insulating waveguide that has good heat insulating performance, is short in the transmission direction, and is lightweight. Further, since the heat insulating waveguide can be manufactured by diverting a normal printed circuit board manufacturing technique, the processability is easy and the cost can be greatly reduced.

  In this case, if a metal pattern for impedance matching is projected on the plate surface of the dielectric plate in the void portion and connected to the metal layer on the plate surface of the dielectric plate, impedance matching to the connected waveguide is required. When this is done, a matching portion can be added to the heat insulating waveguide itself, and matching can be easily achieved.

  In the present invention, the metal layer preferably has a thickness of 5 times or more the penetration thickness of the high-frequency current in the operating frequency band.

  In the present invention, a dielectric plate is used as the heat insulating waveguide material. The superiority of this dielectric plate will be described.

  The heat insulating effect of the heat insulating waveguide can be evaluated by the temperature difference at the connection end of the heat insulating waveguide. Equations (1) and (2) are well known to show the system between the physical constants, dimensions, and heat transfer amount of the heat insulating waveguide.

ΔT = Q · R [K] ...... Equation 1
R = L / (λ · S) [K / W] ...... Formula 2
Here, ΔT is the temperature difference [K] at the connection end of the adiabatic waveguide, Q is the heat transfer amount [W], R is the thermal resistance of the adiabatic waveguide [K / W], and L is the adiabatic waveguide. The length [m], λ is the thermal conductivity [W / (m · K)] of the heat insulating waveguide, and S is the surface area of the connection surface of the heat insulating waveguide.

  3 formulas are derived from 1 formula and 2 formulas to make the explanation easy to understand.

ΔT = (Q · L) / (λ · S) [K] ...... Equation 3
When the heat insulation effect is evaluated, when a certain amount of heat transfer is allowed, it can be said that the larger the temperature difference between the connection ends of the heat insulation waveguide, the better. From Equation 3, the following becomes clear.

(A) The smaller the thermal conductivity λ, the better.

(B) The smaller the surface area S, the better.

(C) The longer the length L, the better. (However, it causes an increase in size.)
First, low thermal conductivity is realized by changing from metal to dielectric, and the small surface area is dominated by the cross-sectional area of the metal conductor that participates in most heat conduction, so the thickness of the metal conductor should be reduced. Can be realized.

By determining the above two constants, the temperature difference ΔT at the connection end of the heat insulating waveguide becomes sufficiently large, so that a commercially available dielectric substrate having a highly available length L can be used.

  Next, a specific example will be described.

  1 and 2 show a first example of the best mode of the heat insulating waveguide according to the present invention. FIG. 1 is a longitudinal sectional view of the heat insulating waveguide of this example in use, and FIG. It is a perspective view of the example heat insulation waveguide. Note that portions corresponding to those in FIGS. 17 and 18 described above are denoted by the same reference numerals.

  A dielectric plate 13 is used for the heat insulating waveguide 5A. The material of the dielectric plate 13 is glass epoxy in this example, and the dimensions of the long side (horizontal direction) and the short side (vertical direction) are X and Y, and the plate thickness is L. The dielectric plate 13 has a rectangular radio wave passage hole 14 in the thickness direction. Metal layers 15 and 16 made of a copper conductive film are attached to and supported by the inner surface of the radio wave passage hole 14 and the entire surface of both plates of the dielectric plate 13 or a part of both plate surfaces connected to the radio wave passage hole 14. ing. The long side dimension (horizontal dimension) and the short side dimension (vertical dimension) of the radio wave passage hole 14 are A and B, and the thicknesses of the metal layers 15 and 16 are T.

  In this example, the waveguides of the waveguide type microwave amplifier 3 and the waveguide circulator 4 are connected to both plate surfaces of the heat insulating waveguide 5A via flanges 3F and 4F. The rectangular radio wave passage hole 14 of the dielectric plate 13 has the same size as the rectangular radio wave passage hole of each waveguide of the waveguide type microwave amplifier 3 and the waveguide circulator 4 on both sides.

  In order to obtain the temperature difference ΔT when the diameter of the heat insulating waveguide 5A is A and B, the thickness of the metal layers 15 and 16 is T, and the heat transfer amount is Q, Expression 4 is shown.

ΔT = (Q · L1) / (λ1 · S1 + λ2 · S2) [K].
Here, L1 is the thickness of the dielectric plate 13, λ1 is the thermal conductivity of the dielectric plate 13, S1 is the surface area of the connecting surface of the dielectric plate 13, λ2 is the thermal conductivity of the metal layers 15 and 16, and S2 is the metal It is a cross-sectional area of the layers 15 and 16.

  Equation 3 is the temperature difference ΔT when using the conventional heat insulating waveguide 5A, and Equation 4 is the temperature difference ΔT when using the heat insulating waveguide 5A of the present invention. The effect of the present invention can be understood by comparing the lengths L and L1 of the heat insulating waveguide 5A necessary for obtaining the same temperature difference ΔT and heat transfer amount Q by comparing the two.

  At this time, the microwave passing between the waveguides of the waveguide type microwave amplifier 3 and the waveguide circulator 4 can pass through the waveguide formed of the metal layer 15 without loss. The property is not adversely affected.

  When the heat insulation effect at this time is obtained by Equation 4, the thickness L of the dielectric plate necessary for obtaining the temperature difference ΔT of 50K is 3.5 mm, and the length L of the conventional heat insulation waveguide 5A is L = 70 mm. On the other hand, the size can be greatly reduced.

  The physical property constants, dimensions, and heat transfer used for the calculation are as follows.

λ1 = 0.4 [W / (m · K)],
λ2 = 398 [W / (m · K)],
S1 = 0.0052m ² ,
S2 = 0.0000123 m ² ,
T = 50 μm,
Q = 100W
3 to 5 show a second example of the best mode of the heat insulating waveguide according to the present invention. FIG. 3 is a longitudinal sectional view of the heat insulating waveguide of this example in use, and FIG. FIG. 5 is a perspective view of the heat insulating waveguide of the example, and FIG. 5 is an equivalent circuit of the heat insulating waveguide of the present example. The parts corresponding to those in FIGS. 1 and 2 described above are denoted by the same reference numerals.

  The difference between the heat insulating waveguide 5A of this example and the heat insulating waveguide 5A of the first example is that the short side dimension (vertical dimension) of the waveguide diameter of the heat insulating waveguide 5A of this example is reduced to C. The other is the same.

  In this way, when the short side dimension of the waveguide diameter is partially reduced and an electromagnetic discontinuity is generated with respect to the TE10 mode, which is the fundamental transmission mode, an equivalent circuit is shown in FIG. It is well known that the circuit becomes a branch-connected circuit. The purpose of loading this capacitive reactance is to match the impedance of each waveguide of the waveguide type microwave amplifier 3 and the waveguide circulator 4.

  6 to 8 show a third example of the best mode of the heat insulating waveguide according to the present invention. FIG. 6 is a longitudinal sectional view of the heat insulating waveguide of this example in use, and FIG. FIG. 8 is a perspective view of the heat insulating waveguide of the example, and FIG. 8 is an equivalent circuit of the heat insulating waveguide of the present example. The parts corresponding to those in FIGS. 1 and 2 described above are denoted by the same reference numerals.

  The difference between the heat insulation waveguide 5A of this example and the heat insulation waveguide 5A of the first example is that the long side dimension (lateral dimension) of the waveguide diameter of the heat insulation waveguide 5A of this example is reduced to D. The other is the same.

  In this way, when the long side dimension of the waveguide diameter is partially reduced and an electromagnetic discontinuity is generated with respect to the TE10 mode, which is a fundamental transmission mode, an equivalent circuit is shown in FIG. It is well known that the circuit becomes a branch-connected circuit. The purpose of loading this inductive reactance is to match the impedance of each waveguide of the waveguide type microwave amplifier 3 and the waveguide circulator 4.

  9 and 10 show a fourth example of the best mode of the heat insulating waveguide according to the present invention. FIG. 9 is a longitudinal sectional view of the heat insulating waveguide of this example in use, and FIG. It is a perspective view of the example heat insulation waveguide. The parts corresponding to those in FIGS. 1 and 2 described above are denoted by the same reference numerals.

  The difference between the heat insulation waveguide 5A of the first example and the heat insulation waveguide 5A of the present example is that the metal layer 15 is not provided on the inner surface of the radio wave passage hole 14, but instead of the radio wave passage hole 14 of the dielectric plate 13. A large number of through holes 17 are provided in the plate thickness direction at predetermined intervals around the inner wall, and the metal layers 16 on both plate surfaces of the dielectric plate 13 are equal in potential with the conductors 18 in each through hole 17. To be electrically connected. That is, the conductor 18 in the through-hole 17 connects the metal layers 16 stretched on both sides of the dielectric plate 13 with each other at the shortest to make the ground potential the same in terms of high frequency.

  For this reason, since the guide wavelength is long at a relatively low frequency, the microwave characteristics can be transmitted without any practical problem. Note that the pitch (interval) of the through holes 17 may be optimized according to the required electrical performance, such as finer according to the frequency band used, or double or triple around the radio wave passage hole 14.

  11 and 12 show a fifth example of the best mode of the heat insulating waveguide according to the present invention. FIG. 11 is a longitudinal sectional view of the heat insulating waveguide of this example in use, and FIG. It is a perspective view of the example heat insulation waveguide. The parts corresponding to those in FIGS. 1 and 2 described above are denoted by the same reference numerals.

  The difference between the heat insulating waveguide 5A of the first example and the heat insulating waveguide 5A of the present example is that the radio wave passage hole 14 is not provided in the dielectric plate 13, but instead corresponds to the both plate surfaces of the dielectric plate 13. A metal layer 16 made of a copper conductive film is supported on the peripheral portion excluding the rectangular void portion 19. The dielectric plate 13 is provided with a large number of through holes 17 at predetermined intervals around the void portion 19 in the plate thickness direction, and the conductors 18 in each through hole 17 are provided on both plate surfaces of the dielectric plate 13. The metal layer 16 is electrically connected so as to have the same potential. In this case, the dielectric plate 13 is made of, for example, tetrafluoroethylene having a small dielectric loss.

  In such a heat insulating waveguide 5A, when the dielectric plate 13 is made of a material having a small dielectric loss such as tetrafluoroethylene, the impedance is not reduced if the dielectric thickness L is sufficiently smaller than the in-tube wavelength of the operating frequency. The continuity can be ignored in practice. At this time, L may be about 1/30 of the guide wavelength.

  FIGS. 13 to 15 show a sixth example of the best mode of the heat insulating waveguide according to the present invention. FIG. 13 is a longitudinal sectional view of the heat insulating waveguide of this example in use, and FIG. The perspective view of the heat insulation waveguide of an example and FIG. 15 are the equivalent circuits of the heat insulation waveguide of this example. Note that portions corresponding to those in FIGS. 11 and 12 showing the fifth example of the present invention described above are denoted by the same reference numerals.

  The difference between the heat insulating waveguide 5A of the fifth example and the heat insulating waveguide 5A of the present example is that the space 19 on one side (or both sides) of the both surfaces of the dielectric plate 13 is formed on the metal layer 16. A rectangular impedance matching metal pattern 20 made of a metal layer is continuously provided.

  The equivalent circuit when the protruding portion of the impedance matching metal pattern 20 made of this metal layer generates an electromagnetic discontinuity with respect to the TE10 mode which is the basic transmission mode has a capacitive reactance branching as shown in FIG. It is well known to be a connected circuit. The purpose of loading this capacitive reactance is to match the impedance of each waveguide of the waveguide type microwave amplifier 3 and the waveguide circulator 4.

  When the dielectric plate 13 described above is used as a normal printed circuit board as it is, the outer shape processing, through-hole formation, pattern formation, etc. can be handled by the conventional printed circuit board manufacturing technology. Is unnecessary.

  In each of the above-described examples, a rectangular radio wave passage hole 14 is formed in the dielectric plate 13 or a rectangular void portion 19 is provided in the metal layer 16 on both plate surfaces of the dielectric plate 13. However, the structure is not limited to this. For example, a structure in which a circular radio wave passage hole 14 is formed in the dielectric plate 13 or a circular void portion 19 is provided in the metal layers 16 on both plate surfaces of the dielectric plate 13. The present invention can also be applied to other heat insulating waveguides.

It is a longitudinal cross-sectional view of the use condition in the 1st example of the heat insulation waveguide which concerns on this invention. It is a perspective view of the heat insulation waveguide of the 1st example. It is a longitudinal cross-sectional view of the use condition in the 2nd example of the heat insulation waveguide which concerns on this invention. It is a perspective view of the heat insulation waveguide of the 2nd example. It is an equivalent circuit schematic of the heat insulation waveguide of the 2nd example. It is a longitudinal cross-sectional view of the use condition in the 3rd example of the heat insulation waveguide which concerns on this invention. It is a perspective view of the heat insulation waveguide of the 3rd example. It is an equivalent circuit schematic of the heat insulation waveguide of the 3rd example. It is a longitudinal cross-sectional view of the use condition in the 4th example of the heat insulation waveguide which concerns on this invention. It is a perspective view of the heat insulation waveguide of the 4th example. It is a longitudinal cross-sectional view of the use condition in the 5th example of the heat insulation waveguide which concerns on this invention. It is a perspective view of the heat insulation waveguide of the 5th example. It is a longitudinal cross-sectional view of the use condition in the 6th example of the heat insulation waveguide which concerns on this invention. It is a perspective view of the heat insulation waveguide of the 6th example. It is an equivalent circuit schematic of the heat insulation waveguide of the 6th example. It is a circuit diagram of the conventional waveguide circuit. It is a perspective view of the conventional waveguide circuit. It is a perspective view of the conventional heat insulation waveguide. It is a longitudinal cross-sectional view of the other conventional heat insulation waveguide.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Terminal 3 Waveguide type | mold microwave amplifier 4 Waveguide circulator 5 Connection waveguide 5A Thermal insulation waveguide 6 Dummy load 7 Radio wave passage hole 8 Radio wave passage hole 9 Dielectric tube 10 Metal layer 11 Flange part 12 Metal Layer 13 Dielectric plate 14 Radio wave passage hole 15, 16 Metal layer 17 Through hole 18 Conductor 19 Cavity 20 Metal pattern for impedance matching

Claims (6)

   A radio wave passage hole is formed in the thickness direction of the dielectric plate, and metal layers are formed on the inner surface of the radio wave passage hole and the entire surface of both plates of the dielectric plate or on a part of both plate surfaces connected to the radio wave passage hole A heat-insulating waveguide characterized by being supported.    2. The heat insulating waveguide according to claim 1, wherein a dimension of the radio wave passage hole is smaller than a diameter of the waveguide to be connected.    A radio wave passage hole is formed in the thickness direction of the dielectric plate, and a metal layer is supported on the entire surface of both plate surfaces of the dielectric plate or a part of both plate surfaces connected to the radio wave passage hole, and the dielectric plate Has a plurality of through holes provided in the plate thickness direction at a predetermined interval in a peripheral portion along the inner wall of the radio wave passage hole, and the metal layers on both plate surfaces of the dielectric plate are conductors in the through holes. Are electrically connected so as to equalize the electric potential.    A metal layer is supported on a peripheral portion of the dielectric plate excluding the corresponding void portions on both plate surfaces, and the dielectric plate has a plurality of through holes at predetermined intervals in the peripheral portion of the void portion. A heat-insulating waveguide provided in the plate thickness direction, wherein the metal layers on both plate surfaces of the dielectric plate are electrically connected by conductors in the through holes so as to equalize the potential. .   5. The impedance matching metal pattern projects from the plate surface of the dielectric plate in the void portion so as to connect to the metal layer on the plate surface of the dielectric plate. Insulated waveguide. 6. The heat insulating waveguide according to claim 1, wherein the metal layer has a thickness that is five times or more the penetration thickness of a high-frequency current in a use frequency band. .

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