JPH05315801A - Microwave vacuum air-tight window - Google Patents

Abstract

PURPOSE:To prevent a change in an electric characteristic due to dispersion in the dimension of a metallized part. CONSTITUTION:The inner diameter of a cylindrical metallic component 3 with a flange joined to a metallized part 2 with brazing is designed to be smaller than the inner diameter of the metallized part 2 applied to an outer circumference of a ceramic disk 1. As a result, even when the inner diameter of the metallized part 2 is changed, since the change is masked by the inner diameter of the metallic component 3, the change gives almost less effect onto the electric characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a microwave vacuum hermetic window used for an input / output section of a microwave tube.

[0002]

2. Description of the Related Art A microwave vacuum hermetic window is used for vacuum sealing and at the same time transmitting microwaves, and the conventional one has a structure shown in a sectional view in FIG. is doing. In the microwave vacuum airtight window shown in FIG. 5, usually, a disc-shaped ceramic 41 such as limina or beryllia and a cylindrical metal part 44 brazed to a metallized portion 42 provided on the circumferential portion of the disc-shaped ceramic 41 are provided. The microwave vacuum hermetic window is composed of metal parts 46 for connecting to circular or rectangular waveguides 45 located on both sides of the window. The microwave transmitted from one of the waveguides 45 passes through the disc-shaped ceramic 41, is transmitted to the other waveguide 45, and is vacuum-tightened on both sides of the disc-shaped ceramic 41.

FIG. 6 shows another example of a conventional microwave vacuum airtight window, which is a disc-shaped ceramic 51 and flanges brazed to both sides of a metallized portion 52 provided on the outer peripheral portion of the disc-shaped ceramic 51. It is composed of an attached cylindrical metal part 53 and a metal part 56 for connecting the waveguide 55.
In FIG. 6 as well, microwaves transmitted through the waveguide 55 are transmitted, and at the same time, vacuum sealing is performed on both sides of the disk-shaped ceramic 51. The microwave vacuum airtight window shown in FIG. 6 has a sufficient brazing area with the cylindrical metal part 53 with a flange even if the thickness of the disk-shaped ceramic 51 is reduced, so that the overall shape is It is often used in a high frequency band of 14 GHz or higher, which is inevitable.

FIG. 7 shows an example of a conventional microwave vacuum hermetic window having a coaxial structure. In this microwave vacuum airtight coaxial window,
Cylindrical ceramic 61 such as normal alumina or beryllia
And a rod-shaped metal part 63 brazed to the metallized layer 62 provided on the inner peripheral part of the cylindrical ceramic 61, and a cylindrical metal part brazed to the metallized layer 62 provided on the outer peripheral part of the cylindrical ceramic 61. 64 is a main component. The rod-shaped metal part 63 and the cylindrical metal part 64 are respectively
It is joined to the inner conductor 65 and the outer conductor 66 of the coaxial line connected before and after the microwave vacuum airtight coaxial window. The microwave transmitted from one of the coaxial lines passes through the cylindrical ceramic 61 and is transmitted to the other, and the microwave is input to a microwave tube that is vacuum-tight on both sides of the cylindrical ceramic 61 and operates in vacuum. Alternatively, it has a function of enabling the extraction of microwaves from the microwave tube.

FIG. 8 shows another example of the microwave vacuum airtight coaxial window, which is a cylindrical ceramic 71 and a cylindrical ceramic 7.
1. A rod-shaped metal part 73 brazed to the metallization layer 72 formed on the inner peripheral portion of 1 and a cylindrical cylinder with a flange brazed to another metallization layer 72 annularly formed on both end faces of the cylindrical ceramic 71. The metal component 77 is the main constituent element. Also in FIG. 8, the microwave transmitted from one of the coaxial lines passes through the cylindrical ceramic 71, is transmitted to the other, and is vacuum-tight on both sides of the cylindrical ceramic 71. In the microwave vacuum airtight coaxial window shown in FIG. 8, since the inner diameter of the cylindrical metal part 77 with a flange can be freely selected, that is, the characteristic impedance of this portion as a coaxial line can be varied, the cylindrical ceramic 71 It has a feature that it is possible to reduce the deterioration of the reflection loss characteristic in a portion.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the high frequency band of Hz or higher, the microwave vacuum hermetic window structure as shown in FIG. 6 is adopted, but there are the following problems particularly in the millimeter wave region of 30 GHz or higher. For example, in the case of 30 GHz band, when the waveguide 55 is a rectangular waveguide, the inner diameter dimension is 7.11 mm × 3.56 m.
m, the inner diameter of the cylindrical metal part 53 is about 9 mm in diameter, and the thickness of the disk-shaped ceramic 51 is
It will be about 0.3 mm. These metal parts can be machined to have a dimensional accuracy of ± 0.01 mm or less, and the thickness of the disk-shaped ceramic 51 can be maintained at the same size by polishing, so that the electrical accuracy depending on the machining accuracy can be maintained. The deterioration of the characteristics can be ignored. However,
The dimensional accuracy of the application range of the metallized portion 52 formed on the disk-shaped ceramic 51 is usually limited to about ± 0.1 mm. In particular, the error in the inner diameter of the metallized portion 52 is 0.1 m.
Even if the thickness is about m, there is a problem that the electrical characteristics such as the reflection loss characteristics are greatly affected.

Further, even in the structure of the microwave vacuum airtight coaxial window shown in FIG. 8, there are the following problems when it is necessary to reduce the entire structure, particularly the radial dimension, such as when it is used in the millimeter wave region. For example, when the outer diameter of the rod-shaped metal part 73 is 0.5 mm and the inner diameter of the cylindrical metal part 77 with a flange is 2.5 mm, the dimensional accuracy of these diameters may be ± 0.01 mm or less by machining. It is possible, and the characteristic impedance is 9 for a change of 0.01 mm.
The change from 6.5 ohm to ± 0.2 ohm is suppressed, and the change in the reflection loss characteristic can be ignored. However, the metallization layer 7
The dimensional accuracy of the application range of No. 2 is usually about ± 0.1 mm, and the inner diameter of the metallized layer 72 applied to the ring is 0.
When changed by 1 mm, the characteristic impedance changes from 96.5 ohms to ± 2.5 ohms, and the voltage standing wave ratio representing the reflection loss characteristic changes greatly from 1.05 to 1.21, for example. As described above, since the dimensional accuracy of the metallized layer 72 cannot be maintained, there is a problem that electrical characteristics are deteriorated.

[0008]

A microwave vacuum hermetic window according to the present invention comprises a disk-shaped ceramic, a flanged cylindrical metal part joined by brazing to a metallized portion formed on the disk-shaped ceramic, and a micro. The main components are metal parts for connecting to the waveguides located on both sides of the wave vacuum airtight window, but in particular, the inner diameter of the flanged cylindrical metal part is smaller than the inner diameter of the metallized part. I am trying.

The microwave vacuum airtight coaxial window according to the present invention comprises a cylindrical ceramic, a rod-shaped metal part joined by brazing to a metallized layer formed on the inner peripheral portion of the cylindrical ceramic, and both end faces of the cylindrical ceramic. The main component is a cylindrical metal part with a flange joined by brazing to an annular metallized layer, but with a flange due to the inner diameter of the annular metallized layer on both ends of the cylindrical ceramic. The inner diameter of the cylindrical metal part is small.

[0010]

The present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of the first embodiment of the present invention. The microwave vacuum airtight window includes a disc-shaped ceramic 1 and a metallized portion 2 provided on both sides of an outer peripheral portion of the disc-shaped ceramic 1.
A flanged cylindrical metal component 3 having a flange portion brazed to the metallized portion 2, a metal component 6 brazed to the flanged cylindrical metal component 3, and a waveguide connected to the metal component 6 by brazing. 5, the inner diameter of the cylindrical portion of the flanged cylindrical metal component 3 is smaller than the inner diameter of the metallized portion 2.

In this microwave vacuum airtight window, the microwave transmitted from one of the waveguides 5 passes through the disk-shaped ceramic 1 and is transmitted to the other waveguide 5. Waveguide 5
And cylindrical metal part 3 with flange and disk-shaped ceramic 1
In order to avoid the reflection and absorption of the transmitted microwaves at the impedance discontinuity, the dimensions of each part are determined so that the characteristics are optimum in the frequency band used. Further, both sides of the disk-shaped ceramic 1 are vacuum-tightly used, and are used for an input / output circuit section of a microwave tube operating in vacuum.

FIG. 2 is a sectional view of the second embodiment of the present invention. The microwave vacuum airtight window is a disk-shaped ceramic 11
A metallized portion 12 provided on the outer peripheral portion of the disk-shaped ceramic 11, a cylindrical metal component 13 with a flange in which flange portions are brazed to both sides of the disk-shaped ceramic 11 via the metallized portion 12, and a flange It is composed of an annular metal part 16 for connecting the attached cylindrical metal part 13 and the waveguide 15, and the inner diameter of the flange part of the flanged cylindrical metal part 13 is smaller than the inner diameter of the metallized part 12. The microwave vacuum airtight shown in FIG. 2 has the same function as the microwave vacuum airtight window shown in FIG.

FIG. 3 is a sectional view of the third embodiment of the present invention. Microwave vacuum airtight coaxial window is a cylindrical ceramic 2
1, a rod-shaped metal part 23 brazed to the metallized layer 22 provided on the inner peripheral portion of the cylindrical ceramic 21, and another metallized layer 22 provided on the outer peripheral portion including both end faces of the cylindrical ceramic 21. A cylindrical metal part 27 with a flange having a brazed flange part, etc., and the inner diameter of the cylindrical part of the cylindrical metal part 27 with a flange is a metallized layer formed in an annular shape on both ends of the cylindrical ceramic 21. It is smaller than the inner diameter of 22.

In this microwave vacuum airtight coaxial window, the microwave transmitted from one coaxial line composed of the inner conductor 25 and the outer conductor 26 passes through the cylindrical ceramic 21 and is transmitted to the other coaxial line. In addition, the cylindrical ceramic 21
It is vacuum-tight on both sides and is used for the input and output parts of microwave tubes operating in vacuum. In FIG. 3, for example, the outer diameter of the rod-shaped metal part 23 is 0.5 mm, the inner diameter of the cylindrical part of the cylindrical metal part 27 with a flange is 2.5 mm, and the annular metallized layer 2 applied to both ends of the cylindrical ceramic 21.
If the inner diameter of 2 is 2.7 mm and the thickness of the metallized layer 22 is 0.05 mm or less, even if the inner diameter of the metallized layer 22 changes from 2.7 mm to 2.6 mm due to a dimensional error, Since the inner diameter is larger than 2.5 mm, it is masked by this. For example, the voltage standing wave ratio is 1.05 when the inner diameter is 2.7 mm, but becomes 1.07 when the inner diameter is 2.6 mm, and the reflection loss characteristic changes. Can be ignored.

FIG. 4 is a sectional view of the fourth embodiment of the present invention. Microwave vacuum airtight coaxial window is a cylindrical ceramic 3
1, a rod-shaped metal part 33 brazed to the metallized layer 32 formed on the inner peripheral portion of the cylindrical ceramic 31, and another metallized layer 3 formed on both end surfaces of the cylindrical ceramic 31.
2 is composed of a cylindrical metal part 37 with a flange having a brazed flange part, and the inner diameter of the cylindrical part of the cylindrical metal part 37 with a flange is the inner diameter of the annular metallized layer 32 at both ends of the cylindrical ceramic 31. It is getting smaller. Further, the flange portion of the flanged cylindrical metal component 37 has a minute step with a height of about 0.1 mm, and is brazed to the metallized layer 32 outside the step. As a result, the innermost end of the metallized layer 32 does not become a brazed portion, and therefore peeling of the metallized layer 32 due to stress concentration when brazing is prevented.

[0016]

As described above, in the microwave vacuum hermetic window according to the present invention, the inner diameter of the metallized portion formed on the disk-shaped ceramic or the cylindrical ceramic is compared with that of the flange portion or the cylindrical portion of the flanged cylindrical metal part. The inner diameter is small. As a result, when the overall size of the microwave vacuum-tight window is reduced, the dimensional accuracy is
It is necessary to make it as small as 0.01 mm or less, but only the dimensional accuracy of the coating range of the metallized layer is ± 0.1.
Only the accuracy of about mm can be maintained, and in the conventional structure, the variation in the size of the metallization layer had a great influence on the electrical characteristics. It is masked by the inner diameter of the component and has little effect on the electrical properties. In this way, the operating frequency is as high as 30 GHz or higher, and even if the overall size of the microwave vacuum hermetic window is reduced, the microwave vacuum hermeticity with stable electric characteristics can be produced.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment of the present invention.

FIG. 2 is a sectional view of a second embodiment of the present invention.

FIG. 3 is a sectional view of a third embodiment of the present invention.

FIG. 4 is a sectional view of a fourth embodiment of the present invention.

FIG. 5 is a sectional view of an example of a conventional microwave vacuum hermetic window.

FIG. 6 is a cross-sectional view of another example of a conventional microwave vacuum hermetic window.

FIG. 7 is a cross-sectional view of an example of a conventional microwave vacuum hermetic coaxial window.

FIG. 8 is a cross-sectional view of another example of a conventional microwave vacuum hermetic coaxial window.

[Explanation of symbols]

1,11,41,51 Disc-shaped ceramic 2,12,22,32,42,52,62,72 Metallized part 3,13,27,37,53,77 Flanged cylindrical metal part 5,15,45 , 55 Waveguide 6, 16, 46, 56 Metal parts 21, 31, 61, 71 Cylindrical ceramics 23, 33, 63, 73 Rod-shaped metal parts 25, 35, 65, 75 Inner conductor 26, 36, 66, 76 Outer conductor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H01P 3/06

Claims (2)

[Claims] 1. A disc-shaped ceramic, a cylindrical metal component with a flange brazed to a metallized layer formed on the outer periphery of the disc-shaped ceramic, and the cylindrical metal component and the waveguide are connected to each other. A microwave vacuum hermetic window having a metal part for forming a microwave vacuum hermetic window, wherein the inner diameter of the cylindrical metal part with a flange is smaller than the inner diameter of the metallized layer. 2. A cylindrical ceramic, a rod-shaped metal part brazed to a metallized layer formed on an inner peripheral portion of the cylindrical ceramic, and an annular metallized layer formed on both end surfaces of the cylindrical ceramic. In a microwave vacuum hermetic coaxial window having a flanged cylindrical metal part brazed to the above, the inner diameter of the flanged cylindrical metal part is smaller than the inner diameter of the annular metallized layer. Microwave vacuum airtight window.