JPH0582034A - Electron beam tube with imput cavity - Google Patents

Abstract

PURPOSE: To resolve problems caused by the application of a high voltage to a cathode and a grid by keeping an inner body part at high voltage to an outer body part, and forming no conductive connection between both body parts. CONSTITUTION: Direct electrical contact does not exist between any part of an inner body part 40 and flanges 44, 46, and an insulating dielectric material 52 is molded between them. Thereby, the outer body part 42 is insulated from very high voltage applied to the inner body part 40 during use. The piled up region of both body parts 40, 42 shows very high impedance to direct current, and the low voltage (ground) of the outer body part 42 is made possible. Very low impedance to high frequency is realized, and leakage of high frequency component from a cavity is obstructed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to electron beam tube arrays, and more particularly to an input resonant cavity for applying high frequency energy to the array.

[0002]

2. Description of the Related Art The present invention relates to Christ Road (Varian
It is particularly applicable to inductive power tetrode devices (IOTs) such as Associates®. Inductive output tetrodes (hereinafter abbreviated as IOT) are well known, but previously proposed designs have been designed for the entire frequency range of television (eg
In order to obtain the required instantaneous bandwidth (for example 8 MHz) over 70-860 MHz, it is necessary to use several tubes, each tube having to be used with several different cavities. there were. Nowadays, in the case of klystrons, this requirement is met by staggering the various cavities arranged along the electron beam path and adding the output of different frequencies to obtain the required bandwidth. There is. However, this is not possible with normal IOT designs.

Another problem caused by high voltages of the order of 30 kV, which must be applied to the cathode and the grid, should also be noted in normal use, especially since the input cavity can be the outer part of the IOT.

[0004]

SUMMARY OF THE INVENTION The present invention provides an apparatus that eliminates or alleviates some or all of the problems associated with maintaining high cathode and grid voltages while keeping the IOT suitable for television applications. The electron beam tube arrangement according to the present invention comprises a resonant cavity at least partially defined by an inner body portion and an outer body portion, the inner body portion being maintained at a high voltage with respect to the outer body portion, Have no conductive connection between them.

"High voltage" means a voltage of about several tens of kV. Although the present invention is described with respect to an IOT device, it will be apparent that it is applicable to other forms of electron beam tube arrangements having an input resonant cavity such as a klystron. The outer body portion is typically at a very low voltage and is usually grounded. Both body parts are preferably physically connected to each other by a dielectric insulator part, which is advantageous to mold. Both body parts may also be provided with interengaging means to assist in joining the body parts.
These means make it possible to maintain the required voltage difference between the outer body part and the inner body part by limiting the path of extremely high impedance to direct current, while at the coupling part to high frequencies. It is advantageous to dimension so that it exhibits a very low impedance and prevents high frequencies from leaking out of the cavity.

It would be preferable to provide electrical connections through an insulator material between the outside of the cavity and the inner body portion. Advantageously, the input resonant cavity is a primary cavity and comprises a secondary resonant cavity coupled to this primary cavity.
It is preferred that each of these cavities be tuned to a different frequency to allow for greater bandwidth usage than if only one cavity were used.

The resonant frequencies of the primary and secondary cavities are tunable. The tuning may be done independently, or may be linked, for example, such that changing the resonant frequency of one cavity causes the resonant frequency of the other cavity to change accordingly. The volume of the primary cavity can be varied by means included in the outer body portion to tune the resonant frequency.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The IOT shown in FIG.
And an output section 16 in combination with drift tubes 18, 20. The input assembly including the electron gun 10, the cathode 12 and the grid 14 is the primary input cavity 2
Surrounded by two. The primary input cavity 22 is coupled to a secondary input cavity 24 having an output coupler 26. The output section 16 is surrounded by a primary output cavity 28, which is coupled to a secondary output cavity 30 having an output coupler 32.

During use, a high frequency voltage of several hundred volts is generated between the cathode 12 and the grid 14, and both are maintained at about 30 kV. Further, it is necessary to maintain a negative DC bias voltage of about several hundreds V with respect to the cathode 12 in the grid 14. More particularly, the invention relates to the primary input cavity 22 of the illustrated device.
The inner body portion 40 includes an upper annular metal plate 70 and a lower annular metal plate 71, which are separated by a dielectric material 73 to define an annular channel. Upper plate 7
0 is electrically connected to the cathode 12 and the lower plate 71 is the grid 1
4 is electrically connected. The open portion of this channel faces outward and surrounds the open portion of another annular channel that includes the metallic outer body portion 42 (the input cavity 22 is defined by portions 40 and 42).

Angled flanges 44,46 are provided on opposite sides of the outer body portion 42 to provide additional annular channels 48,
Limited to 50. The free edges of the inner body portion 40 project into these channels. However, there is no direct electrical contact between any portion of the inner body portion 40, any portion of the outer body portion 42, and the flanges 44, 46, and there is an insulating dielectric between them. The material 52 is molded. This serves to insulate the outer body portion 42 from the inner body portion 40 and thus from the very high voltages applied during use. The use of the dielectric 52 electrically insulates the body portions 40, 42 while forming a potential path for high frequency leakage through the dielectric 52. Therefore, the dimensions of the overlapping passages of the portions 40, 42 should be chosen to present a very low impedance to high frequencies to prevent as much high frequency leakage as possible.

The capacitance of the cavity 22, and thus the resonant frequency, can be varied by conventional techniques, such as by using a tuning door as shown at 94. A modification of the primary input cavity 22 is shown in FIG. In this example, the outer body portion 42 extends axially to form an elongated annular region 90 (which region is defined by the elongated cylindrical wall 91.92 of the body portion). The effective capacity of the region 90 can be varied by means of a sliding plate 93 which can be moved axially by any suitable means.

Although the dielectric is shown as smooth in the drawings, it may have, for example, a knurled edge or a groove.
The withstand voltage capability can be further improved by shaping the surface. Power leads 54 are conducted through the dielectric 52 to maintain the electrical insulation of the outer body portion 42 while maintaining the grid 14 at the proper bias voltage. The connection is made between the lead 54 and the plate 71.

Inside the primary input cavity 22 is a coupling loop 6
0, 62 linked to the secondary input cavity 24. The internal volume of the secondary input cavity 24, and thus its resonance frequency, can be adjusted by a movable plunger 64 projecting from the hole member 66. In this embodiment of the invention, the volumes of the primary cavity 22 and the secondary cavity 24 are independently variable, but they may be linked to move together. The primary cavity 22 and the secondary cavity 24 have different resonance frequencies.

At the output of the IOT, the primary output cavity 2
8 surrounds the output section 16 and the cavity is tunable in the usual way. Cavity 28 is coupled to secondary output cavity 30 by coupling loop 80. The connection to the secondary cavity 30 includes a dome structure 82 provided on its inner wall. Tuning the secondary cavity 30 can be done by conventional techniques. FIG. 3 is another embodiment of the invention in which only one input cavity is included in the array. The input cavity of this particular array is similar to that shown in FIG.

[Brief description of drawings]

1 is a side cross-sectional view of an IOT according to the present invention, some of which have been omitted for clarity,

FIG. 2 shows a modification of the primary input cavity,

FIG. 3 shows another embodiment according to the present invention.

[Explanation of symbols]

 10 Electron Gun 12 Cathode 14 Lattice 16 Output Sections 18, 20 Drift Tube 22 Primary Input Cavity 24 Secondary Input Cavity 26 Output Coupler 28 Primary Output Cavity 30 Secondary Output Cavity 32 Output Coupler 40 Inner Body Part 42 Outer Body Part 44 , 46 Square flanges 48, 50 Annular channel 52 Insulation dielectric material 54 Power leads 60, 62 Coupling loop 64 Plunger 66 Hole member 70 Upper annular metal plate 71 Lower annular metal plate 73 Dielectric material 80 Coupling loop 82 Dome structure 90 Annular region 91, 92 Wall of body part 42 93 Sliding plate 94 Tuning door

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mark Britzsey's United Kingdom Essex's C2 28 WHICH ELMS FOOD Garry Wouts de Sheerpington Close 19 (72) Inventor Edward Stanislaus Sovier AZKI British CHERMSFOOD Great Badordo Sit Avenyu 38 ( 72) Inventor Stephen Badell United Kingdom Essets CM 61 Nef Burnston High Easter Road Bissyops Green 3

Claims (22)

[Claims] 1. A resonant cavity at least partially defined by an inner body portion and an outer body portion,
An electron beam tube arrangement characterized in that the inner body part is maintained at a high voltage with respect to the outer body part and no conductive connection is provided between both body parts. 2. The array of claim 1, wherein the outer body portion has a relatively low voltage. 3. The array of claim 2, wherein the outer body portion is grounded. 4. The arrangement according to claim 1, wherein both body parts are physically connected to each other by a dielectric insulator part. 5. The array of claim 4, wherein an electrical connection is provided through an insulator portion between the outside of the cavity and the inner body portion. 6. The arrangement according to claim 1, wherein the resonant cavity has a substantially annular cross section and surrounds the electron gun. 7. The array of claim 6 wherein one portion of the resonant cavity has a greater radial extent than another portion of the resonant cavity. 8. The array of claim 7, wherein the other portion extends more than one portion in a direction perpendicular to the annular radius. 9. A method according to any one of the preceding claims, wherein both body parts are interleaved with each other and the coupling of both body parts presents a very low impedance to high frequencies to prevent high frequency leakage from the cavity. Sequence described in. 10. Both body parts alternate with each other by a first annular disc extending from the inner body part and second and third annular discs extending from the outer body part and overlapping the first annular disc. And a region between the second disc and the first disc and a region between the first disc and the third disc are filled with a dielectric material capable of withstanding a high voltage. The sequence according to Item 9. 11. The arrangement according to claim 10, when dependent on claim 7 or 8, wherein the further part is defined by an outer body part. 12. Arrangement according to any of the preceding claims, wherein the outer body part comprises means for varying the volume of the cavity. 13. An array according to any of the preceding claims, wherein the input resonant cavity is the primary cavity and includes a secondary resonant cavity coupled to the primary resonant cavity. 14. The array of claim 13, wherein the primary cavity and the secondary cavity are tuned to different frequencies. 15. The arrangement according to claim 13, wherein the primary cavity and the secondary cavity are connected by a loop provided in each cavity and the loops are electrically connected to each other. 16. The loop is movable, and the coupling degree can be controlled by the movement of one or both loops.
The sequence described in 5. 17. The array according to claim 13, wherein the resonance frequency of the primary cavity is tunable. 18. The array according to claim 13, wherein the resonance frequency of the secondary cavity is tunable. 19. The array of claim 18, wherein the resonant frequency of the secondary cavity is adjusted by a plunger adapted to project from the hole into the secondary cavity to change the volume of the secondary cavity. 20. The arrangement according to claim 19, wherein the position of the plunger is adjusted by an adjusting screw. 21. The array according to claim 17, wherein the primary cavity and the secondary cavity are independently tunable. 22. An arrangement according to any of the preceding claims, wherein the electron beam tube is an inductive power tetrode.