JPH01286232A - traveling wave tube - Google Patents

Abstract

PURPOSE:To suppress the propagation of unwanted modes by forming helix support bars in a fan shape with a stepped cross section, forming a cylindrical conducting layer on a step section and a side face, fitting it in a vacuum envelope, and bringing the support bars into contact with a helix. CONSTITUTION:Three helix support bars 7 made of a dielectric substance are formed in a fan shape with a step section 8 on the cross section, 4 conducting layer 9 is formed on the step section 8 and a side face. An electromagnetic wave attenuating film 10 made of a carbon film is formed on the surface of a protruded portion 7a not formed with the conducting layer 9 at the fixed position in the axial direction of the support bars 7 so that the resistance value is distributed to be gradually decreased, constant, and gradually increased in the axial direction. The portion with the lowest resistance value is electrically short-circuited to the conducting layer 9. The whole three support bars 7 are cylindrically formed and fitted in a vacuum envelope 4, tips 7a of the support bars 7 are brazed or closely stuck to a helix, outer peripheries of the support bars 7 are brought into face contact with the inner face of the envelope 4. The conducting layer for blocking the propagation of unwanted modes and the electromagnetic wave attenuating thin film are integrally fitted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention (Field of Industrial Application)] This invention relates to traveling wave tubes, and particularly to improvements in helical slow wave circuits thereof.

(Prior Art) Traveling wave tubes generally use electron beams to amplify and oscillate microwaves. Conventional traveling wave tubes are constructed as shown in FIG. , slow wave circuit 2
and a collector 3. And the slow wave circuit 2 is
Inside the pipe-shaped vacuum envelope 4, a plurality of helices 5 are supported and fixed by, for example, three dielectric helix support rods 6. In this case, the three helix support rods 6 are
Usually, they are arranged in contact with the inner surface of the vacuum envelope 4 at equal intervals of 120°.

By the way, in some traveling wave tubes, in order to prevent the propagation of unnecessary modes, a metal rod for preventing the propagation of unnecessary modes is provided between the three helix support rods 6 (Japanese Patent Publication No. 1983-
40527), and an electromagnetic wave attenuating film is formed on the helix support rod 6.

(Problems to be Solved by the Invention) However, the conventional traveling wave tube as described above has the following problems.

■ In the structure in which three helix support rods 6 and three metal rods for blocking unwanted mode propagation are inserted into the vacuum envelope 4,
Each part tends to have only line contact.

■ Therefore, thermal conductivity is low and thermal instability increases.

(2) Due to the dimensional problem as mentioned in item 0, deformation of the helix 5 and breakage of the helix support rod 6 during insertion are likely to occur.

This invention improves the tightness between the helix, helix support rod, and vacuum envelope to realize efficient heat diffusion, prevents deformation of the helix and breakage of the helix support rod, and prevents the propagation of unnecessary mode high frequencies. The purpose of the present invention is to provide a traveling wave tube that can suppress the [Structure of the Invention] (Means for Solving the Problems) In the present invention, a plurality of helix support rods each have a generally fan-shaped cross section with a stepped portion, and a conductive layer is formed on the stepped portion and the side surface. It is a traveling wave tube that has a cylindrical shape and is installed in a vacuum envelope, with the tips of each helix support rod contacting and holding the helix.

(Function) According to the present invention, since the conductive layer for blocking unwanted mode propagation is integrally applied to the helix support rod, the heat conductive parts of the helix, the helix support rod, and the vacuum envelope come into surface contact. A slow-wave circuit that achieves efficient heat dissipation, suppresses unnecessary mode propagation, and is easy to assemble can be obtained.

(Embodiment) Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings, but since this invention is an improved slow-wave circuit of a traveling wave tube, only the slow-wave circuit will be described. do.

That is, the slow wave circuit according to the present invention is configured as shown in FIG. 1, and the same parts as in the conventional example (FIG. 6) are denoted by the same symbols. A helix 5 is provided, and this helix 5 is supported and fixed by a plurality of dielectric helix support rods 7, for example, three.

In this case, the three dielectric helix support rods 7 are made of, for example, beryllia ceramics, and as is clear from FIG. (The thick line in each figure represents the conductive layer 9, and the terminal end in the cross-sectional view is 9).
8). This conductive layer 9 is metallized and then has a copper coating formed thereon by sputtering, plating, or the like.

Furthermore, as shown in FIG. 3, at a predetermined axial position of this helix support rod 7, an electromagnetic wave attenuating film 10 made of a carbon film is axially extended on the surface of the protruding portion 7a where the conductive layer 9 is not formed. It is formed with a distribution in which the resistance value gradually decreases, remains constant, and gradually increases. The part with the lowest resistance value is the conductive layer 9
is electrically shorted.

Also, although it is not clear in the figure, there are holes on the outer periphery of both ends of the helix support rod 7 in order to make it a container for insertion into the vacuum envelope 4.
It has a rounded feel.

The helix 5 is supported and fixed by these three helix support rods 7 and is inserted into the vacuum envelope 4, but as shown in the figure, the three helix support rods 7 form a cylindrical shape to prevent vacuum. It is installed in the envelope 4, the tips 7a of each helix support rod 7 are brazed or in close contact with the helix, and the outer peripheral surface of each helix support rod 7 is in close surface contact with the inner surface of the vacuum envelope 4. ing.

As described above, the helix support rod 7 of the present invention has a structure in which a conductive layer for blocking unwanted mode propagation and an electromagnetic wave attenuation thin film are integrally attached.

The traveling wave tube of the present invention has the same structure as the conventional example (FIG. 6) except for the slow wave circuit, so a detailed explanation will be omitted.

(Other Embodiments) FIGS. 4 and 5 show other embodiments of the helix support rod used in the present invention, which provide the same effects as the above embodiments.

That is, in the case of FIG. 4, stepped portions 8 are provided on both sides of the helix support rod 6, and in the case of FIG. 5, smoothly curved stepped portions 8 are provided on both sides.

[Effects of the Invention 1 As described above, according to the present invention, the following excellent effects can be obtained.

■Since the conductive material for blocking unwanted mode propagation is integrally attached to the helix support rod, the number of parts inserted into the vacuum envelope is reduced, and the adhesion between each part is improved, resulting in high precision. Assembly is possible. Then, propagation of unnecessary modes is suppressed.

■At the same time as assembling the three helix support rods and the helix, it is possible to position the helix.

When the three helix support rods are combined, they form a cylindrical shape and can be easily inserted into the vacuum envelope.

■The fan-shaped cross-section of the helix support rod provides strong mechanical strength and provides a wide area of contact with the vacuum envelope, providing efficient heat dissipation.

[Brief explanation of the drawing]

FIG. 1 is a radial sectional view showing the main part (slow wave circuit) of a traveling wave tube according to an embodiment of the present invention, and FIGS. 2 and 3 show a helix support rod used in the present invention. 4 and 5 are side views showing other embodiments of the helix support rod used in the present invention, and FIG. 6 is an axial sectional view showing the entire conventional traveling wave tube. be. 4... Vacuum envelope, 5... Helix, 7... Helix support rod, 8... Step portion, 9... Conductive layer, 10
...Electromagnetic wave attenuation film. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2 q Figure 3 Figure 5 j I 6

Claims (1)

[Claims] In a traveling wave tube equipped with a slow wave circuit in which a helix is supported and fixed by a plurality of dielectric helix support rods inside a pipe-shaped vacuum envelope, each of the plurality of helix support rods has a stepped section. A conductive layer is formed on the step part and the side surface, and the plurality of helix support rods are installed in the vacuum envelope in a cylindrical shape, and each tip of each helix support rod contacts and holds the helix. A traveling wave tube characterized by: