JP4659239B2 - Microwave electron tube input / output window structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an input / output window structure of a microwave electron tube, and more particularly to an input / output window structure of a microwave electron tube operating in a millimeter wave band having a high oscillation frequency.
[0002]
[Prior art]
Conventionally, various types of input or output windows for maintaining the degree of vacuum of a microwave electron tube and allowing microwave power to pass therethrough are known. The pill type window shown in FIG. 3 using a disk-shaped dielectric is a typical example of the prior art, and is widely used as an input / output window structure of a microwave electron tube from the viewpoint of broadband characteristics and power durability.
[0003]
FIG. 3 is a diagram showing an example in which a pill type window is used in a magnetron which is a microwave electron tube. Since the magnetron is an oscillation tube, there is no input window and only an output window. The output of the magnetron is taken out to a rectangular waveguide 56 through a ridge portion 55 of the waveguide through a slit 54 provided in the anode block 52. A cylindrical cavity 60 is provided in the rectangular waveguide 56, and a dielectric disk 61 is disposed in the center thereof. This structure is a so-called general pill type window, and ceramic is usually used for the dielectric. The pill type window is designed such that the cylindrical cavity 60 including the dielectric disk 61 resonates at a specific resonance mode of the cavity resonator at the operating frequency. Normally, the TE11 mode, which is a fundamental mode of a cylindrical waveguide, is used as this resonance mode, and the TE111 mode of a cylindrical cavity is generally used. Furthermore, when the operating frequency is increased, the thickness of the ceramic disk has to be reduced correspondingly in the conventional pill type window, for example, about 0.3 mm in the 35 GHz band, and this is reduced on the side surface, that is, the 0.3 mm portion. It was very difficult to braze.
[0004]
[Problems to be solved by the invention]
In the case of the input / output window as described above, in the case of a so-called millimeter-wave region microwave tube, strict dimensional accuracy is required for normal operation, and the size must be reduced according to the wavelength. Since this structure does not work, when the frequency is high and the dielectric disk is small, there is a problem that the reliability of the brazed portion is not good. An object of the present invention is to solve the above problems, and to provide an input / output window structure for a microwave electron tube that does not require much dimensional accuracy, is low in cost, and has high reliability.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, an input / output window structure of a microwave electron tube according to the present invention is a microwave electron tube having a waveguide input or a waveguide output for transmitting only a fundamental mode at an operating frequency. A metal sleeve is fitted to the outside of the wave tube so as to enclose the waveguide, and the end surface of the metal sleeve is covered with a dielectric plate, and the end surface of the metal sleeve and the planar portion of the dielectric plate are hermetically sealed. to joining, the waveguide abuts on the dielectric plate, the said metal sleeve and the waveguide dielectric plate Chi lifting choke function of the surrounding wall, the dielectric and the waveguide A cavity for matching impedance between body plates is formed, and the dielectric plate is dimensioned so that a resonance frequency at the dielectric plate portion caused by a transmission mode is a resonance frequency different from the operating frequency. .
[0006]
The outer shape of the waveguide is formed in a columnar shape having a stepped diameter by reducing the diameter of the end portion, the metal sleeve is formed in a cylindrical shape, and the end portion covers a part of the wall surface of the cavity. It is characterized by doing.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment in which the present invention is applied to a 35 GHz band operation magnetron output window. 1 is a shell, 2 is an anode block, 3 is a metal sleeve, 4 is a slit, 5 is a ridge waveguide, and 6 is a rectangular waveguide. A tube, 7 is a choke cavity, and 8 is a dielectric plate. 2 shows a coupling portion when the magnetron of FIG. 1 is attached to the output waveguide, 9 is a coupling flange, and 10 is an output waveguide.
[0008]
The output window of the magnetron is necessary for taking out the microwave power generated in the magnetron tube while keeping the inside of the magnetron vacuum, and the output is the slit 4, the ridge portion 5 of the waveguide, the rectangular shape The light is taken out from the output waveguide 10 through the waveguide 6 and the dielectric plate 8. The output waveguide 10 and the rectangular waveguide 6 have the same dimensions (7.11 mm × 3.556 mm) as the standard waveguide of WR-28. The rectangular waveguide 6 has a cylindrical shape with a diameter of φ12.6 mm, and the output side end portion is reduced to φ7.84 mm to form a step. The metal sleeve 3 has a cylindrical shape with an inner diameter of φ12.6 mm and an outer diameter of φ13.5 mm, and is fitted to the outside so as to enclose the rectangular waveguide 6.
The dielectric plate 8 is a ceramic disk having a diameter of 17.6 mm and a thickness of 1.3 mm.
[0009]
In order to obtain the vacuum tightness of the magnetron, the metal sleeve 3 is brazed to the shell 1 covering the outside of the tube, and the dielectric plate 8 is brazed so that the opening is covered at the other end. The rectangular waveguide 6 is abutted against the dielectric plate 8 and is not particularly brazed to the dielectric plate 8. Therefore, distortion due to the difference in thermal expansion coefficient between the dielectric plate and the rectangular waveguide does not occur, and good reliability can be obtained. The rectangular waveguide 6 has such a dimension that only the TE10 mode, which is the fundamental mode, is transmitted at the operating frequency. However, the dielectric plate portion has dimensions capable of transmitting various modes in addition to the fundamental mode. In designing the window of the present invention, the dimensions should be such that resonance in the dielectric plate portion caused by these transmission modes is avoided from the operating frequency.
[0010]
The choke cavity 7 is formed by surrounding the metal sleeve 3, the rectangular waveguide 6 and the dielectric plate 8 with surrounding walls, and has a choke function. The dimensions of the choke cavity 7 are appropriately selected by experiments or the like in advance so as not to cause impedance mismatch between the rectangular waveguide 6 and the dielectric plate 8. The choke cavity 7 of the present example has a ring shape with an outer diameter of φ12.6 mm (inner diameter of the metal sleeve) and an inner diameter of φ7.84 mm (diameter of the end of the rectangular waveguide 6), and its width is 2.38 mm. It is like. The width dimension of the choke cavity 7 is preferably adjusted within about 10% of the fluctuation width with the center value being approximately 1/4 of the microwave wavelength at the operating frequency.
[0011]
Since the present embodiment has such a structure, it can be easily manufactured. That is, if the rectangular waveguide 6 is small, the final shape can be obtained from a copper slag at a time by cold forging, and even a large one can be easily obtained by drawing and turning. Further, it is not necessary to use a milling process or the like to form the choke cavity 7, and the choke cavity 7 can be formed only by fitting the metal sleeve 3 to the rectangular waveguide 6. Since brazing can also be performed in a portion that can be seen from the outside without being performed inside the waveguide as in the prior art, workability is improved. Further, if the metal sleeve is a commercially available steel pipe, the cost can be reduced.
[0012]
Since this embodiment has been described with a magnetron as an oscillation tube, it has only an output function, but an amplifier tube such as a cross-field amplifier tube or traveling wave tube has both input and output functions. Can be taken. In this example, a ceramic disk is used for the dielectric plate 8, but it is also possible to use a dielectric such as glass, diamond, or sapphire as the material. In this example, the metal sleeve 3 has a cylindrical shape. However, it is not always necessary to have a cylindrical shape for ease of manufacture. The same applies to ceramic discs.
[0013]
As described above, the great difference in structure between the present embodiment and the conventional example is that the present embodiment does not have the cylindrical cavity 60. The cylindrical cavity 60 constitutes a cavity resonator and functions as a so-called band-pass filter that allows only a high frequency of a desired frequency to pass through depending on its size. Therefore, the thickness of the ceramic disk 61 incorporated therein is strictly determined in order to match the resonance frequency. In the case of this embodiment, the portion corresponding to the conventional cylindrical cavity 60 is formed at the joint portion of the rectangular waveguide 6, the dielectric plate 8, and the output waveguide 10. That is, mismatching occurring before and after the dielectric plate portion is eliminated by appropriately changing the dimensions of the choke cavity 7. In addition, since the window of the present embodiment is configured so as to be aligned as the window together with the coupling flange 9, the shape of the coupling flange 9 is a special shape unlike the normal standard flange, but the bat that is mounted on a plane is used. Either a flange or a choke flange provided with a choke structure can be used. By configuring in this way, the connection with the output waveguide is facilitated, and a highly efficient and highly efficient mounting structure is provided.
[0014]
【The invention's effect】
Since the input / output window of the present invention does not adjust the ceramic plate to a specific resonance frequency, it is only necessary to avoid the resonance frequency from the operating frequency. In addition, since the dielectric plate size can be increased with respect to the operating frequency, it is an input / output window that can be easily assembled even in a high-frequency microwave tube such as a millimeter wave band. The input / output window of the present invention is the same 35 GHz band and the thickness of the ceramic plate can be 1.3 mm, and brazing can be performed not on the side but on the flat surface, so that assembly is easy.
[0015]
In addition, the outer shape of the waveguide can be a columnar shape with a stepped portion, and a cylindrical metal sleeve can be externally fitted, and the space surrounded by these and a dielectric plate can be a cavity with a choke function. Thus, a microwave electron tube with further improved productivity can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an input / output window structure of a microwave electron tube according to an embodiment of the present invention.
2 is a cross-sectional view showing a structure for attaching the microwave electron tube of FIG. 1; FIG.
FIG. 3 is a cross-sectional view showing an input / output window structure of a conventional microwave electron tube.
[Explanation of symbols]
1: shell, 2: anode block, 3: metal sleeve, 4: slit, 5: ridge waveguide, 6: rectangular waveguide, 7: choke cavity, 8: dielectric plate, 9: coupling flange, 10 : Output waveguide, 51: Shell, 52: Anode block, 54: Slit, 55: Ridge waveguide, 56: Rectangular waveguide, 60: Cylindrical cavity, 61: Ceramic disc, 62: Output waveguide

Claims (2)

An input / output window structure of a microwave electron tube having a waveguide input or a waveguide output for transmitting only a fundamental mode at an operating frequency, wherein a metal sleeve is included outside the waveguide so as to enclose the waveguide. The end face of the metal sleeve is covered with a dielectric plate, and the end face of the metal sleeve and the planar portion of the dielectric plate are hermetically sealed and joined, and the waveguide is in contact with the dielectric plate. contact, together with the metal sleeve and the waveguide and the dielectric plate Chi lifting the choke function of the surrounding wall to form a cavity matching the impedance of the dielectric plates and the waveguide, the dielectric The input / output window structure of a microwave electron tube, wherein the body plate has a dimension such that a resonance frequency in the dielectric plate portion caused by a transmission mode is a resonance frequency different from the operation frequency .   The waveguide outer shape is formed in a columnar shape in which the diameter of the end portion is reduced to form a step, the metal sleeve is formed in a cylindrical shape, and the end portion forms part of the wall surface of the cavity. The input / output window structure of the microwave electron tube according to claim 1.

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