PILLBOX VACUUM WINDOW

Abstract

A pillbox vacuum window of the present invention has a first metal part and a second metal part. The first metal part includes a ceramic disk formed with a metallization layer in a peripheral area thereof, a larger diameter cylindrical portion, and a smaller diameter cylindrical portion having an inner diameter smaller than that of the larger diameter cylindrical portion, and coupled to the larger diameter cylindrical portion to form a step section at a joint, where the ceramic disk is fitted into the step section. The second metal part includes a cylindrical portion, where the cylindrical portion is inserted into the step section of the first metal part while the ceramic disk is placed in the step section of the first metal part.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating the structure of a general microwave tube;

FIG. 2A is a longitudinal sectional view illustrating an exemplary configuration of a conventional pillbox vacuum window;

FIG. 2B is a cross-sectional view illustrating an exemplary configuration of the conventional pillbox vacuum window;

FIG. 3A is a longitudinal sectional view illustrating another exemplary configuration of a conventional pillbox vacuum window;

FIG. 3B is a cross-sectional view illustrating another exemplary configuration of the conventional pillbox vacuum window;

FIG. 4 is a graph for describing the VSWR characteristics of the pillbox vacuum window illustrated in FIGS. 2A and 2B;

FIG. 5A is a longitudinal sectional view illustrating the configuration of a pillbox vacuum window according to one embodiment of the present invention;

FIG. 5B is a cross-sectional view illustrating the configuration of the pillbox vacuum window according to the embodiment of the present invention;

FIG. 6A is a cross-sectional view illustrating a method of manufacturing a pillbox vacuum window illustrated in FIGS. 5A and 5B;

FIG. 6B is a cross-sectional view illustrating a method of manufacturing a pillbox vacuum window illustrated in FIGS. 5A and 5B;

FIG. 6C is a cross-sectional view illustrating a method of manufacturing a pillbox vacuum window illustrated in FIGS. 5A and 5B;

FIG. 6D is a cross-sectional view illustrating a method of manufacturing a pillbox vacuum window illustrated in FIGS. 5A and 5B; and

FIG. 7 is a graph for describing the VSWR characteristics of the pillbox vacuum window illustrated in FIGS. 5A and 5B.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 5A is a longitudinal sectional view illustrating the configuration of a pillbox vacuum window according to one embodiment of the present invention, and FIG. 5B is a cross-sectional view illustrating the configuration of the pillbox vacuum window according to the embodiment of the present invention.

Referring to FIGS. 5A and 5B, the pillbox vacuum window of this embodiment comprises ceramic disk 1, metallization layer 2, metal part 3 which is a first metal part, and metal part 4 which is a second metal part.

Ceramic disk 1 is positioned at the center of the pillbox vacuum window.

Metallization layer 2 is formed on the peripheral side surface of ceramic disk 1 and on the peripheral areas of both plane surfaces of the same.

Metal part 3 has a portion which defines square waveguide 6a and the other portion which defines cylindrical waveguide 5. The portion which defines cylindrical waveguide 5 includes larger diameter cylindrical portion 3a which has an inner diameter substantially identical to the outer diameter of ceramic disk 1, and smaller diameter portion 3b which has an inner diameter smaller than that of larger diameter cylindrical portion 3a, is coupled to larger diameter cylindrical portion 3a, and is formed at a joint with portion 3a to form step section 3c. Ceramic disk 1 is fitted into this step section 3c.

Metal part 4 has a portion which defines square waveguide 6b, and the other portion which defines cylindrical waveguide 5. The portion which defines cylindrical waveguide 5 includes cylindrical portion 4a which has an outer diameter substantially identical to the outer diameter of ceramic disk 1. This cylindrical portion 4a is inserted into step section 3c of metal part 3 while ceramic disk 1 is placed in step section 3c of metal part 3.

Now, a description will be given of a method of manufacturing the pillbox vacuum window of this embodiment.

Referring to FIG. 6A, first, metal part 3 is provided.

Referring to FIG. 6B, next, ceramic disk 1 that is formed with metallization layer 2 around the periphery is fitted into step section 3c of metal part 3, and ceramic disk 1 is bonded to metal part 3 by brazing through metallization layer 2.

Referring to FIG. 6C, next, metal part 4 is provided.

Referring to FIG. 6D, subsequently, while ceramic disk 1 is placed in step section 3c of metal part 3, cylindrical portion 4a of metal part 3 is inserted into step section 3c of metal part 3, and metal part 3 is bonded to ceramic disk 1 by brazing through metallization layer 2.

In this embodiment, ceramic disk 1 has thickness t of 0.2 mm, cylindrical waveguide 5 has a cylindrical cavity, the inner diameter R of which is 4 mm, and square waveguides 6a, 6b each have a long side a of 7.11 mm and a short side b of 3.56 mm.

FIG. 7 is a graph for describing the VSWR characteristics of the pillbox vacuum window of this embodiment.

In the configuration of the pillbox vacuum window according to this embodiment, the inner diameter of larger diameter cylindrical portion 3a which forms step section 3c of metal part 3, and the outer diameter of cylindrical portion 4a of metal part 4 are substantially the same as the outer diameter of ceramic disk 1, and cylindrical portion 4a of metal part 4 is inserted into step section 3c of metal part 3 while ceramic disk 1 is placed in step section 3c of metal part 3.

Consequently, the leak path, which extends along the length of portions of ceramic disk 1 and metal parts 3, 4 which are bonded to each other through metallization layer 2, can be shorted. Specifically, the leak path can be sized to have length L of 0.22 mm in the radial direction and length T of 0.22 mm in the thickness direction. In this way, metallization layer 2 can be sized to have a minimum length of 0.22 mm in the radial direction and a minimum length of 0.22 in the thickness direction, and therefore the lengths can be reduced in the radial and thickness directions, thus making it possible to avoid resonance which would otherwise occur in a peripheral area of ceramic disk 1 within an available frequency band (26.5 to 40.0 GHz), as shown in FIG. 7.

Also, since the lengths of metallization layer 2 can be reduced in the radial and thickness directions, ceramic disk 1 need not be increased in diameter and thickness more than is necessary. This can reduce the proportion of dielectric material which occupies the overall pillbox vacuum window, leading to the avoidance of an increase in VSWR within the available frequency range, due to the influence of the dielectric material, as shown in FIG. 7.

As a result, stable VSWR characteristics can be achieved around a value of 1.18 or less within the available frequency range of the pillbox vacuum window.

Further, since the pillbox vacuum window of this embodiment is configured such that cylindrical portion 4a of metal part 4 is inserted into step section 3C of metal part 3 while ceramic disk 1 is placed in step section 3C of metal part 3, thin ceramic disk 1 can be fixed with high accuracy. In addition, since metal part 4 is also accurately inserted into metal part 3, an appropriate dimensional accuracy can be maintained for each part.

While preferred embodiments of the present invention have been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.

Claims

1. A pillbox vacuum window for use in a microwave tube as input/output windows, comprising: a ceramic disk having a metallization layer formed in a peripheral area thereof;a first metal part including a larger diameter cylindrical portion, and a smaller diameter cylindrical portion having an inner diameter smaller than that of said larger diameter cylindrical part, and coupled to said larger diameter cylindrical part to form a step section at a joint, said ceramic disk being fitted into the step section; anda second metal part including a cylindrical portion being inserted into the step section of said first metal part while said ceramic disk is placed in the step section of said first metal part.

2. The pillbox vacuum window according to claim 1, wherein said larger diameter cylindrical portion of said first metal part has an inner diameter substantially identical to the outer diameter of said ceramic disk.

3. The pillbox vacuum window according to claim 1, wherein said cylindrical portion of said second metal part has an outer diameter substantially identical to the outer diameter of said ceramic disk.

4. A method of manufacturing a pillbox vacuum window for use in a microwave tube as input/output windows, comprising the steps of: providing a first metal part which includes a larger diameter cylindrical portion having an inner diameter substantially identical to the outer diameter of a ceramic disk formed with a metallization layer in a peripheral area thereof, and a smaller diameter cylindrical portion having an inner diameter smaller than that of said larger diameter cylindrical portion, and coupled to said larger diameter cylindrical portion to form a step section at a joint;providing a second metal part which includes a cylindrical portion having an outer diameter substantially identical to the outer diameter of said ceramic disk; andinserting the cylindrical portion of said second metal part into the step section of said first metal part so as to sandwich said ceramic disk.

5. The method according to claim 4, wherein said step of inserting the cylindrical portion of said second metal part into the step section of said first metal part includes the step of fitting said ceramic disk into the step section of said first metal part, and bonding said ceramic disk to said first metal part.

6. The method according to claim 5, wherein, in said step of bonding said ceramic disk to said first metal part, said first metal part is bonded to said ceramic disk by brazing through said metallization layer.

7. The method according to claim 4, wherein said step of inserting the cylindrical portion of said second metal part into the step section of said first metal part includes the step of inserting the cylindrical portion of said second metal part into the step section of said first metal part, and bonding said second metal part to said ceramic disk.

8. The method according to claim 7, wherein, in said step of bonding said second metal part to said ceramic disk, said second metal part is bonded to said ceramic disk by brazing through said metallization layer.