JP5957305B2 - Waveguide - Google Patents

Description

  Embodiments of the invention relate to a waveguide.

  In the field of cellular phone base stations, broadcast systems, weather radars, and other fields that use radio waves, superconducting filters capable of realizing steep characteristics have attracted attention. Waveguides are used to input / output radio waves to this type of low-temperature operating device. Since the temperature difference between the high temperature side and the low temperature side of the device reaches 200 K [Kelvin], it is necessary to cut off the heat transfer between them. In view of this, a split waveguide has been proposed in which a physical gap (gap) is provided between the high temperature side and the low temperature side, and the thermal contact between the two is interrupted.

JP 2010-154392 A

As is well known, the waveguide can be reduced in size by loading a dielectric inside the tube. When the dielectric constant of the dielectric is ε, the size of the waveguide loaded with the dielectric can be approximately 1 / √ε of the hollow waveguide. However, since the dielectrics are arranged opposite to each other in the split waveguide, heat conduction due to heat radiation between the dielectrics occurs even if heat conduction due to contact is interrupted. In particular, a device that functions at an ultra-low temperature, such as a superconducting filter, has a large temperature difference between the high-temperature side and the low-temperature side.
An object is to provide a split-type waveguide that prevents heat conduction due to heat radiation.

  According to the embodiment, the waveguide includes first and second waveguides each having an opening, and a heat shield member. The opening of the first waveguide and the opening of the second waveguide are arranged to face each other with a gap. The heat shield member is formed in the opening of the second waveguide, and blocks radiation heat from the first waveguide to the second waveguide.

FIG. 1 is a perspective view illustrating an example of a split waveguide according to the embodiment. FIG. 2 is a cross-sectional view showing the vicinity of the gap 105 of the split waveguide according to the first embodiment. FIG. 3 is a cross-sectional view schematically showing an example of the structure of the dielectric multilayer film 201. FIG. 4 is a schematic diagram for explaining the reflection characteristics of the dielectric multilayer film 201. FIG. 5 is a diagram illustrating an example of a black body radiation spectrum at a temperature of 300K. FIG. 6 is a cross-sectional view showing the vicinity of the gap 105 of the split waveguide according to the second embodiment. FIG. 7 is a cross-sectional view schematically showing another example of the dielectric multilayer film 201.

  FIG. 1 is a perspective view illustrating an example of a split waveguide according to the embodiment. In FIG. 1, the opening of the waveguide 101 and the opening of the waveguide 102 are arranged to face each other with a gap 105 interposed therebetween. The radio wave travels in a direction perpendicular to the openings of the waveguides 101 and 102. That is, the waveguides 101 and 102 are arranged with the openings perpendicular to the traveling direction of the radio wave facing each other. Both of the waveguides 101 and 102 are tubular. Although a prismatic tube is shown in FIG. 1, other shapes such as a cylindrical tube are also possible.

  The inside of the waveguide 101 is filled with a dielectric 103, and the inside of the waveguide 102 is filled with a dielectric 104. As a result, the size of the waveguide can be reduced as compared with the case where there is no filler.

  The waveguide 102 is attached to the superconducting device 106 in a state enclosed in a vacuum chamber, for example. The superconducting device 106 is, for example, a superconducting filter that filters radio waves input from the waveguide 102. The waveguide 102 functions as an input waveguide for the superconducting device 106.

  The waveguide 102 can also function as an output waveguide for the superconducting device 106. In this case, the superconducting device 106 is, for example, a superconducting filter that filters input radio waves and outputs them to the waveguide 102.

  The superconducting device 106 includes a superconductor (not shown) such as an yttrium oxide. The superconductor is cooled to below the critical temperature of the superconducting state by the refrigerator 107. Therefore, the temperature of the superconducting device 106 and the waveguide 102 connected thereto is also near the temperature of the superconductor. The superconducting device 106 is an example of a device to be cooled.

  On the other hand, at least a part of the waveguide 101 is exposed to room temperature. The normal temperature is, for example, the outside of the vacuum chamber, a space where radio waves propagate, or a coaxial waveguide converter. Alternatively, at least a part of the waveguide 101 is in contact with a room temperature member (such as an outer wall of a vacuum chamber). In short, the temperature of the waveguide 101 is approximately room temperature. That is, the temperature of the waveguide 102 connected to the superconducting device 106 is lower than the temperature of the waveguide 101. The temperature difference extends to the order of 200-300K. Next, a plurality of embodiments will be described based on the above configuration.

[First Embodiment]
FIG. 2 is a cross-sectional view showing the vicinity of the gap 105 of the split waveguide according to the first embodiment. In the first embodiment, a reflection film as a heat shielding member is formed in an opening in contact with the gap 105 in the waveguide on the low temperature side, that is, the waveguide 102. The heat shield member blocks the radiant heat from the waveguide 101 to the waveguide 102 by reflecting a light beam that mediates thermal radiation. Infrared rays are typical as light rays, but visible light or ultraviolet rays can also be considered. As an example of the reflection film, a dielectric multilayer film is taken and denoted by reference numeral 201.

  FIG. 3 is a cross-sectional view schematically showing an example of the structure of the dielectric multilayer film 201. The dielectric multilayer film 201 is formed by laminating the multilayer films 201a, 201b, 201c, and 201d in this order, for example.

  The multilayer films 201a, 201b, 201c, and 201d are formed by alternately stacking a high refractive index single layer film and a low refractive index single layer film. By controlling the thickness of the single layer film, the center wavelength in the reflection spectrum of the multilayer film can be changed. That is, the thicker the single layer film, the more the central wavelength in the reflection spectrum of the multilayer film moves to the longer wavelength side.

  The high refractive index film can be mainly composed of In2O3, Nd2O3, Sb2O3, ZrO2, CeO2, TiO2, ZnS, Bi2O3, Ta2O5, ZnSe, CdS, Sb2S3, CdTe, Si, Ge, Te, PbTe and the like.

  The low refractive index film can be mainly composed of CaF2, NaF, Na3AlF6, LiF, MgF2, Si2, LaF3, NdF3, Al2O3, CeF3, PbF3, MgO, ThO2, SnO2, La2O3, SiO and the like. In addition, SiO2 can be included in the composition.

  The dielectric multilayer film 201 is a natural oxidation method in which oxygen gas is simply introduced into the chamber of the film formation apparatus, or ion-assisted oxidation in which ions such as argon and nitrogen are irradiated while oxygen gas is introduced into the chamber of the film formation apparatus. A thin film having the above composition is stacked by an (oxynitriding) method, an ion beam irradiation oxidation method in which oxygen or nitrogen ions are irradiated.

  In FIG. 3, a dielectric multilayer film 201 having a total of 16 layers, in which a multilayer film in which four single-layer films are stacked in four layers, is stacked is shown. This configuration is an example and does not limit the total number of films or the laminated structure.

  FIG. 4 is a schematic diagram for explaining the reflection characteristics of the dielectric multilayer film 201. In the graph of FIG. 4, the horizontal axis indicates the wavelength, and the vertical axis indicates the reflectance of the multilayer films 201a to 201d. Reference numerals 301 to 304 denote reflection spectra of the multilayer films 201a, 201b, 201c, and 201d, respectively. That is, the dielectric multilayer film 201 is formed by laminating a plurality of dielectric films (multilayer films) having different reflection spectra.

  In the first embodiment, the design center wavelength of the multilayer film 201a is 5.7 μm. The design center wavelength of the multilayer film 201b is 9.7 μm. The design center wavelength of the multilayer film 201c is 16.6 μm. The design center wavelength of the multilayer film 201d is 28.5 μm. Then, the reflection spectrum of each multilayer film is designed so as to cover a spectrum range of about 4 to 34 μm as a whole.

  Therefore, the reflection spectrum of the entire 16-layer dielectric multilayer film 201 is substantially equal to the sum of the reflection spectra 301, 302, 303, and 304. For example, a reflectance of 80% or more is set in the wavelength range of 4 μm to 34 μm. be able to.

  FIG. 5 is a diagram illustrating an example of a black body radiation spectrum at a temperature of 300K. In the graph of FIG. 5, the horizontal axis indicates the wavelength and the vertical axis indicates the light intensity. According to the graph of FIG. 5, it can be seen that about 80% of the radiant energy exists in the wavelength range of about 4 μm to 30 μm (reference numeral 401).

  Therefore, if the temperature of the waveguide 101 is about 300K, by providing the dielectric multilayer film 201, 64% (80% × 80%) of thermal energy transferred from the waveguide 101 to the waveguide 102 via radiation. The above can be reflected to the waveguide 101 side.

  Since the radiation coefficients of the dielectrics 103 and 104 occupying most of the cross sections of the waveguides 102 and 103 are generally 0.9 or more, most of the thermal energy reflected by the dielectric multilayer film 201 is the waveguide 101. The re-reflection is less than 10%. As described above, according to the first embodiment, it is possible to suppress the transfer of thermal energy due to thermal radiation, and it is possible to suppress the heat conduction through the gap.

  In the existing dielectric-loaded split waveguide, heat conduction occurs due to heat radiation between the dielectrics, and it is difficult to reduce the heat conduction between the high temperature side and the low temperature side. Therefore, there is a dilemma that the merit of dividing the waveguide is lost as the size is reduced.

  On the other hand, in the first embodiment, a reflective film such as a dielectric multilayer film is provided on the surface of the dielectric loaded on the waveguide on the low temperature side so as to block heat conduction due to heat radiation between the dielectrics. did. Thereby, the heat (infrared rays) radiated from the high temperature side dielectric is reflected by the reflection film on the low temperature side dielectric surface. Since the emissivity (= absorption rate) of the dielectric is as high as 0.8 to 0.9, the reflected infrared light is almost absorbed by the high temperature side dielectric.

  Therefore, heat conduction by heat radiation between the high temperature side waveguide and the low temperature side waveguide can be cut off, and low heat conduction, which is an original merit of the split waveguide, can be realized. For these reasons, according to the first embodiment, it is possible to provide a split-type waveguide that prevents heat conduction due to thermal radiation.

[Second Embodiment]
FIG. 6 is a cross-sectional view showing the vicinity of the gap 105 of the split waveguide according to the second embodiment. The parts common to FIG. 2 are denoted by the same reference numerals, and only the parts different from the first embodiment will be described below.

  In the second embodiment, a heat absorbing member as a heat shielding member is formed in the opening of the waveguide 102 that is in contact with the gap 105. The heat-absorbing member blocks the radiant heat from the waveguide 101 to the waveguide 102 by absorbing a light beam that mediates thermal radiation.

  The heat absorbing member includes a heat conductor 501 attached to the waveguide 102 with a spacer 502 as a heat insulating material interposed therebetween, a heat transfer member 503 that transfers heat of the heat conductor 501, and a Peltier element 504. The Peltier element 504 is supplied with power from the power source 505 to cool itself, whereby the heat of the heat conductor 501 moves to the Peltier element 504.

  In the second embodiment, the infrared absorption film 601 is formed on the side of the thermal conductor 501 facing the waveguide 101. Unlike the dielectric multilayer film 201 shown in FIG. 2, the infrared absorption film 601 absorbs infrared rays. Infrared rays are an example of light rays that mediate thermal radiation. By providing the infrared absorption film 601, radiant heat from the waveguide 101 is efficiently captured by the heat conductor 501, and the heat insulation effect can be enhanced.

  Further, in the second embodiment, the heat radiation fin 506 may be attached to the Peltier element 504, and the fan 507 may send air to the heat radiation fin 506 to radiate the heat of the Peltier element 504, thereby cooling the heat absorbing member. Even in this case, the heat conduction by the heat radiation between the high temperature side waveguide and the low temperature side waveguide can be cut off, and the second embodiment also prevents the heat conduction by the radiation. It becomes possible to provide a type of waveguide.

The present invention is not limited to the above embodiments. For example, the configuration of the dielectric multilayer film 201 is not limited to FIG.
FIG. 7 is a cross-sectional view schematically showing another example of the dielectric multilayer film 201. As shown in FIG. 7, the order of stacking the multilayer films 201a to 201d in the dielectric multilayer film 201 is arbitrary. In addition, as described in the explanation of FIG. 3, the number of layers included in each of the multilayer films 201a to 201d is not limited to four.

  As mentioned above, although embodiment was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 101,102 ... Waveguide, 103, 104 ... Dielectric, 105 ... Gap, 106 ... Superconducting device, 107 ... Refrigerator, 201 ... Dielectric multilayer, 201a, 201b, 201c, 201d ... Multi-layer film, 301 ... Reflection spectrum of multilayer film with central wavelength of 5.7 μm, 302 ... Reflection spectrum of multilayer film with central wavelength of 9.7 μm, 303 ... Reflection spectrum of multilayer film with central wavelength of 16.6 μm, 304 ... Reflection spectrum of multilayer film with central wavelength of 16.6 μm ,..., A heat conductor, 502... Spacer, 503... Heat transfer member, 504. Peltier element, 505... Power source, 506. 507 ... Fan, 601 ... Infrared absorbing film

Claims (16)

A first waveguide having an opening;
A second waveguide having an opening disposed opposite to the opening of the first waveguide with a gap therebetween;
A waveguide comprising: a heat shielding member formed at an opening of the second waveguide that blocks radiation heat from the first waveguide to the second waveguide.   The waveguide according to claim 1, wherein the first waveguide and the second waveguide include a dielectric filled therein.   The waveguide according to any one of claims 1 and 2, wherein the heat shield member is a reflective film that reflects a light beam that mediates thermal radiation.   The waveguide according to claim 3, wherein the reflective film is a dielectric multilayer film.   The waveguide according to claim 4, wherein the dielectric multilayer film is formed by laminating a plurality of dielectric films each having a different reflection spectrum.   3. The waveguide according to claim 1, wherein the heat shield member is a heat absorbing member that absorbs a light beam that mediates thermal radiation. 4.   The waveguide according to claim 6, further comprising a cooling unit that cools the heat absorbing member.   2. The waveguide according to claim 1, wherein the opening of the first waveguide and the opening of the second waveguide face each other perpendicular to the propagation direction of the radio wave.   The waveguide according to claim 1, wherein the second waveguide is attached to a cooled device.   The waveguide according to claim 9, wherein the device to be cooled is a superconducting device.   The waveguide according to claim 10, wherein the superconducting device is a superconducting filter that filters radio waves input from the second waveguide.   The waveguide according to claim 10, wherein the superconducting device is a superconducting filter that filters input radio waves and outputs the filtered radio waves to the second waveguide. The first waveguide is at least partially exposed to room temperature,
The waveguide according to claim 1, wherein the second waveguide is sealed in a vacuum chamber. A first waveguide having an opening;
A second waveguide having an opening disposed opposite to the opening of the first waveguide with a gap therebetween;
A heat shielding member that is formed in the opening of the second waveguide and blocks radiation heat from the first waveguide to the second waveguide;
The heat shielding member is a waveguide, which is a heat absorbing member that absorbs a light beam that mediates thermal radiation. The waveguide according to claim 14, wherein the first waveguide and the second waveguide include a dielectric filled therein. The waveguide according to claim 14, further comprising a cooling unit that cools the heat absorbing member.

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