JP2560638B2 - Multi-cavity klystron - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicavity klystron, and more particularly to a multicavity klystron having a harmonic cavity in an intermediate cavity.

[0002]

2. Description of the Related Art In general, a multi-cavity klystron is a high-frequency circuit section comprising an electron gun for emitting and forming an electron beam and a plurality of cavity resonators for amplifying the high-frequency signal by interacting the electron beam with the high-frequency signal. And a collector that collects an electron beam and converts electron kinetic energy into heat energy to radiate heat. However, in such a multi-cavity klystron, it has been conventionally practiced to use the second harmonic cavity for higher efficiency. By using the second harmonic cavity, the second harmonic group voltage is superimposed on the fundamental frequency group voltage, and a periodic sawtooth waveform is generated to increase the group voltage and enhance the grouping effect.

Such a method is disclosed in Japanese Examined Patent Publication No. 56-12987.
As disclosed in the publication, in order to improve electron bunching of an electron beam, a pair of fundamental wave cavity resonators and a subsequent harmonic cavity resonator are included in an intermediate cavity, so that electron bunching is performed. The bunching effect is enhanced by rearranging the electrons from the inter-bunching area without the tendency to debundle. Figure 3 is Japanese Examined Sho 56
This is a conventional example described in JP-A-12987. In FIG. 3, an electron beam 26 emitted from the electron gun 25
Interacts with a high frequency signal in the high frequency circuit section 27, amplifies the high frequency signal, and is collected by the collector. The high frequency circuit 27 includes an input cavity 31 and two second harmonic cavities 28.
And an intermediate cavity 30 composed of three fundamental wave cavities 29, and an output cavity 32. An output circuit 33 is connected to the output cavity 32 of the multi-cavity klystron, and a coupling loop 22 is provided in the input cavity 31. The coupling loop 22 is placed in parallel with the electron beam 26 and has a function of propagating an input RF signal in the input cavity as an electromagnetic wave of TM01 mode. That is, the input RF signal is coupled to the input cavity in the magnetic field mode in the coupling loop and is guided to the high frequency circuit section 27 of the multicavity klystron.

[0004]

In the conventional multi-cavity klystron using the harmonic cavity, the second harmonic cavity voltage is superimposed on the fundamental harmonic group voltage by using the second harmonic cavity. Since the clustering voltage is increased and the clustering effect is enhanced, the second harmonic output with respect to the fundamental wave output is increased.

Load VSW of a normal multi-cavity klystron
R is suppressed to a low level with respect to the fundamental wave output, but becomes worse with respect to harmonics. Therefore, if the second harmonic output is large, the reflected power of the second harmonic output from the load circuit increases. The reflected power of the second harmonic adversely affects the operation of the multi-cavity klystron, increases the body current and decreases the output, and sometimes causes an RF discharge in the load circuit to damage the multi-cavity klystron. There was a fear that it hindered the practical application of the multi-cavity klyslon using the harmonic cavity.

[0006]

A multi-cavity klystron of the present invention comprises an electron gun for injecting and forming an electron beam, a high frequency circuit section for interacting the high frequency signal with the electron beam and amplifying the high frequency signal, and an electron beam. The high-frequency circuit section is composed of an input fundamental wave cavity, an intermediate cavity composed of at least one harmonic cavity and a plurality of fundamental wave cavities, and an output cavity. The fundamental wave cavity of the barrel has a coupling loop connected to an external load whose maximum dimension in the direction parallel to the electron beam axis of the aperture is smaller than the height dimension of the cavity wall of the harmonic cavity. The coupling loop is in a vacuum tube and at least one coupling loop is placed. Some coupling loops are placed perpendicular to the electron beam, and impedance adjusting means is provided between the coupling loop and the external load.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a multi-cavity klystron of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a multi-cavity klystron according to a first embodiment of the present invention. In FIG. 1, the electron beam 2 ejected and formed from the electron gun 1 interacts with the high frequency signal in the high frequency circuit section 3 to amplify the high frequency signal and is collected by the collector 24. High frequency circuit section 3
Is composed of an input cavity 4, an intermediate cavity 7 made up of a fundamental wave cavity 5 and a harmonic cavity 6 and an output cavity 8, and the fundamental cavity 5 of the intermediate cavity 7 has a coupling loop. 14 are provided. This coupling loop 14 forms an opening by bending a flat plate or a wire, and the maximum dimension l of the aperture of this opening in the direction parallel to the electron beam axis is as shown in FIG. It is smaller than the height dimension l'of the wall. Therefore, the coupling loop 14 has a small amount of coupling with the fundamental waveform component of the fundamental wave cavity, but has a large coupling with the harmonic component. Further, the coupling loop 14 is connected to the external load 11 via the line 9 and the impedance adjusting means 10.
The impedance adjusting means 10 changes the amount of coupling of the coupling loop 14 with respect to the higher harmonic wave, and enables adjustment of the amount of higher harmonic wave output.

An experiment was conducted on the presence or absence of a coupling loop at an output of 30 kW, and it was found that -30 dBc was obtained without the loop.
The harmonics were -45dB when the loop was attached.
It was improved to c or less and a reduction of 15 dB or more was achieved. In this embodiment, the case where two coupling loops are provided is shown, but the number may be increased or decreased, and the position, shape, etc. may be changed.

FIG. 2A is a sectional view of a second embodiment of the multicavity klystron of the present invention. In this second embodiment, coupling loops 14, 1 are provided in the fundamental wave cavity 13 of the intermediate cavity 12.
5, the coupling loop 14 is connected to the external load 21 via the line 16 and the impedance adjusting means 10,
On the other hand, the coupling loop 15 is placed perpendicular to the electron beam 19 and connected to the external load 21 via the line 20, as shown in FIG. In this case, the coupling loop 15 is not coupled with the TM mode but is coupled with the unnecessary higher TE mode. Therefore, in the second embodiment, not only the harmonic components can be reduced, but also the higher-order TE mode which is an unstable factor can be attenuated, so that a more stable multicavity klystron can be obtained.

[0010]

As described above, according to the present invention, the fundamental wave cavity is formed by providing the coupling loop for coupling the harmonic wave to the fundamental waveform cavity of the intermediate cavity composed of the harmonic cavity and the fundamental cavity. It is possible to reduce the harmonic components in the output and reduce the harmonic output included in the output. Therefore, the harmonic reflected power from the output load circuit can be suppressed, the occurrence of RF discharge in the output circuit can be suppressed, and the multi-cavity klystron can be operated stably. It goes without saying that the harmonic components in the fundamental wave cavity are so-called secondary by-products generated as a result of the electron beam bunching and have almost no effect on the electron beam bunching.

[Brief description of drawings]

FIG. 1 is a sectional view of a multi-cavity klystron according to a first embodiment of the present invention.

2A is a sectional view of a multi-cavity klystron according to a second embodiment of the present invention, and FIG. 2B is a diagram showing an arrangement of a coupling loop 15.

FIG. 3 is a sectional view of a conventional multi-cavity klystron.

[Explanation of symbols]

 1,25 Electron gun 2,19,26 Electron beam 3,23,27 High frequency circuit section 4,31 Input cavity 5,13,29 Fundamental wave cavity 6,28 Harmonic cavity 7,12,30 Intermediate cavity 14,15 Coupling loop 9,20 Line 10 Impedance adjusting means 11,21 External load 22 RF input loop 24 Collector 8,32 Output cavity 33 Output load circuit

Claims (3)

(57) [Claims] 1. An electron gun for emitting and forming an electron beam,
It has a high-frequency circuit unit that amplifies the high-frequency signal by interacting the electron beam with the high-frequency signal, and a collector that collects the electron beam, the high-frequency circuit unit being an input fundamental wave cavity and at least one harmonic cavity. In a multi-cavity klystron composed of an intermediate cavity composed of a plurality of fundamental cavities and an output cavity, at least one fundamental cavity of the intermediate cavity has a coupling loop connected to an external load. The multi-cavity klystron is characterized in that the maximum dimension in the direction parallel to the electron beam axis of the aperture portion of the coupling loop is smaller than the height dimension of the cavity wall of the harmonic cavity. 2. An impedance adjusting means is provided between the coupling loop and an external load.
Multi-cavity klystron described. 3. An electron gun for emitting and forming an electron beam,
It has a high-frequency circuit unit that amplifies the high-frequency signal by interacting the electron beam with the high-frequency signal, and a collector that collects the electron beam, the high-frequency circuit unit being an input fundamental wave cavity and at least one harmonic cavity. In a multi-cavity klystron composed of an intermediate cavity composed of a plurality of fundamental wave cavities and an output cavity, an electron beam connected to an external load to at least one of the intermediate cavity cavities and having an electron beam of a diameter portion. It has a coupling loop whose maximum dimension parallel to the axis is smaller than the height dimension of the cavity wall of the harmonic cavity, and one of the remaining fundamental wave cavities of the intermediate cavity is perpendicular to the electron beam. A multi-cavity klystron having a coupling loop placed on.