JPS5842578B2 - Takuudougata Klystron - Google Patents

Description

[Detailed Description of the Invention] A high-power klystron, which is a type of microwave electron tube, has various features such as high gain, high efficiency, and easy handling, so it is useful for non-line-of-sight communications, satellite communications, UHF-TV broadcasting, etc. It is widely used as the final stage amplifier of transmitters in the field of

Generally, high-power klystrons consist of multiple cavity resonators (
In order to operate a high-power klystron in the fields mentioned above, the resonant frequency of the cavity must be changed in some way to match the operating frequency or a frequency close to it. There is a need.

Various methods for changing the resonant frequency of the cavity have been considered and actually employed in the prior art.

Examples thereof are shown in FIGS. 1 to 3, and the prior art will be explained below with reference to the figures.

FIG. 1 shows what is generally called the C tuning method.

That is, the cavity has a cavity outer wall 1, a drift 2, a capacitive plate 3,
It is composed of a bellows 4, a tuning nut 5, a tuning screw 6, a support 7, etc.

By turning the tuning screw 6 clockwise or counterclockwise, the air volume plate 3 approaches or moves away from the drift tube 2.

That is, the electrical capacitance between the drift tube 2 and the capacitive plate 30 changes, and as a result, the resonant frequency of the cavity changes.

FIG. 2 shows what is generally called the L tuning method.

That is, the cavity is composed of a cavity outer wall 1, a drift tube 2, a tuning nut 5, a tuning screw 6, a support 7, a diaphragm 8, and the like.

By turning the tuning screw 6 clockwise or counterclockwise, the diaphragm 8 will move in or out of the cavity.

That is, since the internal cavity volume changes, the resonant frequency of the cavity changes as a result.

The method shown in FIG. 3 is called a dielectric tuning method, and there are examples of it being used in low-power microwave electron tubes such as reflective klystrons.

The cavity is composed of a cavity outer wall 1, a drift 2, a bellows 4, a tuning nut 5, a tuning screw 6, a support 7, a dielectric 9, and the like.

By turning the tuning screw 6 clockwise or counterclockwise, the dielectric 9
will move closer to or away from the drift tube 2.

In other words, the electric field strength inside the cavity is strongest at the drift tube 2, so the electric capacitance inside the cavity changes due to the polarization effect of the dielectric 90, and as a result, the resonant frequency of the cavity changes. Become.

In addition to the methods described above, there are various other methods such as the combined method of FIG. 1 and FIG. 2, but all of the conventional methods have drawbacks.

That is, in the method shown in FIG. 1, a part of the high frequency current flowing through the inner wall surface of the cavity flows through the surface of the bellows 4, which is a part of the vacuum capacity, and in this case, the bellows may be burnt out.

This phenomenon becomes more pronounced as the power increases and the frequency increases due to the skin effect.

As a measure to prevent this, although not shown, a structure is provided in which the bellows 4 is provided outside the cavity instead of inside the cavity, and a spring is provided between the tuning nut 5 and the outer wall 10 of the cavity to allow the high frequency current to pass through. There is.

However, with this structure, the operation of the high-power klystron tends to become unstable due to poor electrical contact in the spring portion.

A disadvantage of the method of FIG. 2 is that the diaphragm 8 is generally made of thin metal and is therefore mechanically weak, thereby limiting the distance that the diaphragm 8 can move.

That is, the range in which the resonant frequency of the cavity can be changed is limited.

Another drawback of this method is that the resonant frequency of the cavity does not always have a constant value with respect to the number of rotations of the tuning screw 6.

That is, since the way the diaphragm 8 deforms is not always constant, the internal volume of the cavity also changes and the resonance frequency shifts.

A disadvantage of the method shown in FIG. 3 is that the dielectric 91 is located in a portion of the cavity where the electric field strength is relatively strong and moves near this portion.

Therefore, the dielectric loss of the dielectric 9 becomes not negligible, but becomes extremely large, making it unsuitable for the cavity resonator of a high-power klystron that generally handles high power.

In addition, since the dielectric 9 is located quite close to the drift electrode, metals and other substances from the drift tube 2 are transferred to the dielectric 9, which may cause changes in the electrical capacitance inside the cavity. , even a spark may occur.

The object of the present invention is to provide a multi-cavity talistron which completely eliminates the above-mentioned drawbacks of the prior art.

The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 4 shows a cross-sectional view of the cavity of a multi-cavity klystron using the present invention.

In FIG. 4, an elongated groove 10 having a semicircular cross-sectional shape is provided along the inner wall surface of the resonant cavity formed by the cavity envelope 1 and the drift tube 2. dielectric object 9
is inserted, and one end of the dielectric object 9 is connected to a bellows 4 as a vacuum container and a tuning nut 5 for supporting the dielectric object 9.

Further, one end of the tuning nut 5 is connected to a tuning screw 6, a support 7, etc.

In such a cavity, if the tuning screw 6 is turned clockwise or counterclockwise, the dielectric object 9 will slide in the groove 10, thereby reducing the capacitance component inside the cavity. will change.

That is, the resonant frequency of the cavity changes.

Now, the more the dielectric object 9 is pushed into the groove 10, the lower the resonant frequency of the cavity will be.

The cross-sectional shape of the symmetry 10 may be any shape.

FIG. 5 shows the insertion length l of the dielectric object 9 made of a ceramic round bar of 4.4φ into the groove 10 obtained in the cavity of a multi-cavity klystron employing the present invention, and the resonance frequency of the cavity. The curve shows the relationship that the dielectric constant εr of the dielectric body 9 is used as a parameter, and that as the insertion length becomes longer, the resonant frequency decreases.

As described above, according to the present invention, the groove through which the dielectric object 9 enters and exits is provided in a place where the electric field generated inside the cavity is extremely weak, so that metals and other substances are prevented from sputtering from the drift tube 2. ;do not have.

Furthermore, it is possible to change the resonant frequency of the cavity without electrical contact failure.

Furthermore, by appropriately selecting the dielectric constant εr, the range in which the resonance frequency can be changed can be freely changed, thereby facilitating the design of the multi-cavity klystron.

[Brief explanation of the drawing]

1, 2, and 3 are cross-sectional views of a cavity of a conventional multi-cavity klystron, and FIG. 4 is a cross-sectional view of a cavity employing the present invention. FIG. 5 is a diagram showing changes in resonance frequency experimentally obtained in a cavity employing the present invention. Referring to the figure, 1... Cavity envelope, 2... Drift tube, 3... Capacity plate, 4... Bellows, 5... Tuning nut, 6... Tuning screw, 7...Support, 8...
Diaphragm, 9... dielectric object, 10... groove.

Claims (1)

[Claims] 1. Equipped with a cavity resonator in which an elongated groove is provided along the inner wall surface of the cavity envelope, a dielectric object is inserted into this groove, and the dielectric object can be taken in and out along the groove. Multi-cavity Talistron 0 featuring