JPH0213415B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a structure of an output extraction section of a helical traveling wave tube using a periodic permanent magnet as an electron beam focusing device.

A helical traveling wave tube consists of an electron gun that emits an electron beam, a collector that captures the electron beam, a microwave amplification section that amplifies the circuit wave through continuous interaction with the electron beam, and a circuit wave that enters the microwave amplification section. It consists of an input coupling section, an output coupling section for transmitting the circuit wave from the microwave amplification section to the load, a focusing device that provides a magnetic field for focusing the electron beam, a tube support mechanism, etc.

As a recent general trend, there is a demand for higher output from high-power microwave tubes, and periodic permanent magnets (PPM)
Helical traveling wave tubes that are used as electron beam focusing devices are also expected to have higher output than conventional ones.

However, since the helical traveling wave tube has a relatively heat-resistant structure, high output cannot be achieved without special measures.

FIG. 1 shows a cross section of a high frequency circuit section and a PPM at a high frequency output section of a helical traveling wave tube having a conventional structure. The figure will be briefly explained.

1 is a helix, 2 is an insulator, and a helix support rod 3 is a helix 1 and a helix support rod 2.
4 is a central convex portion of the pole piece, 5 is a magnet, 6 is a coaxial circuit, 7 is a vacuum sealing ceramic, and 8 is a waveguide. In some traveling wave tubes, the inner conductor of the coaxial circuit is not joined to the opposing surface of the waveguide, and there are also structures in which the inner conductor of the coaxial circuit is suddenly connected to the waveguide from the helix without passing through the coaxial circuit. However, in the former case, as the output of the traveling wave tube increases, the temperature of the inner conductor (particularly the tip) increases, which significantly reduces the stable operation of the traveling wave tube, resulting in problems with reliability. In the latter case, it becomes extremely difficult to secure the magnetic field necessary for beam focusing in the relevant portion, which may cause trouble in beam transmission.

A problem in increasing the output of a helical traveling wave tube having a structure in which the tip of the inner conductor is fixed to the waveguide as shown in FIG. 1 is that the temperature of the inner conductor of the coaxial circuit increases. In other words, as the frequency of the traveling wave tube becomes higher, the vacuum sealing ceramic and the coaxial circuit 6 become smaller, and as the output becomes higher, the heat generated in the inner conductor of the coaxial circuit 6 also increases, and the thermal expansion of the inner conductor causes the vacuum sealing to become smaller. There is a risk that unreasonable force will be applied to the ceramic ceramic 7 and the stable operation of the traveling wave tube will be disturbed.

An object of the present invention is to provide a helical traveling wave tube equipped with a new output extraction mechanism that can improve the drawbacks of the conventional structure and operate stably at high frequencies and even at high outputs.

The present invention provides a helical traveling wave tube using a periodic permanent magnet as a beam focusing device, in which the output extraction part is connected from the helix to the waveguide via a coaxial circuit, and the coaxial circuit and the waveguide are connected to each other. The waveguide is characterized in that the wall thickness of the waveguide at the junction is made sufficiently thin to absorb thermal deformation due to temperature rise of the inner conductor.

The present invention will be explained below using the drawings.

FIG. 2 shows an embodiment of the output extraction mechanism of the helical traveling wave tube according to the present invention.

In the present invention, the waveguide 8 is
The feature is that the joint surface with the coaxial circuit 6 is made sufficiently thin. This is due to the higher frequency of the traveling wave tube,
The inner conductor of the coaxial circuit 6 expands due to the heat generated in the coaxial circuit 6 as the output increases, and at this time, the force applied to the vacuum sealing ceramic 7 is transferred to the coaxial circuit 6 of the waveguide 8.
This is to reduce the force applied to the vacuum sealing ceramic 7 by absorbing the force at the joint surface with the vacuum sealing ceramic 7. At this time, by making the distance between the vacuum sealing ceramic 7 and the bonding surface of the waveguide 8 and coaxial circuit 6 as short as possible, the elongation due to thermal expansion of the inner conductor of the coaxial circuit 6 can be reduced, and as a result, Needless to say, the force applied to the vacuum sealing ceramic 7 can be reduced.

Moreover, as shown in FIG. 3, the waveguide 8 and the coaxial circuit 6
Even if it is necessary to provide multiple impedance adjustment screws 9 at short intervals on the joint surface with It goes without saying that effects similar to those of the present invention can be expected by providing thin grooves in the shape of tracks.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a high-frequency circuit and PPM of a helical traveling wave tube with a conventional structure, and FIGS. 2 and 3 a are cross-sectional views showing an output extraction mechanism of a helical traveling wave tube according to the present invention. Figure 3b is Figure 3a
FIG. 1... Helix, 2... Helix support rod,
3... Tubular envelope, 4... Pole piece, 5...
Magnet, 6... Coaxial circuit, 7... Vacuum sealing ceramic, 8... Waveguide, 9... Impedance adjustment screw.

Claims (1)

[Claims] 1. In a helix-shaped traveling wave tube having a configuration in which an output extraction part is connected from a helix to a waveguide via a coaxial circuit, the tip of the inner conductor of the coaxial circuit is joined to the waveguide, and the tip of the inner conductor of the coaxial circuit is connected to the waveguide, and A helical-shaped progression characterized in that at least a portion of the opposing surface of the tip of the inner conductor is made thinner than other wall surfaces to an extent that can absorb thermal deformation due to temperature rise of the inner conductor of the coaxial circuit. Wave tube.