US3059139A - Tunable high frequency tube - Google Patents

Description

Oct. 16, 1962 J. I. SOLOMON TUNABLE HIGH FREQUENCY TUBE Filed Aug. 22, 1960 INV EN TOR.

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3,059,139 TUNABLE HIGH FREQUENCY TUBE Jack I. Solomon, Redwood City, Calif assignor to Varian Associates, Palo Alto, Calif a corporation of California Filed Aug. 22, 1960, Ser. No. 51,045 Clm'ms. (Cl. 315-522) This invention relates generally to ultra-high frequency devices and has reference, more particularly, to novel, tunable, ultra-high frequency reflex klystrons.

Ultra-high frequency reflex klystrons employing a cavity resonator and electron beam reflector as heretofore constructed have utilized external tuning cavities where environments were severe and extreme frequency stability was required, as for example, for use in missile, airborne radar and similar applications. The conventional gn'd gap tuned klystrons have a somewhat wider mechanical tuning range than external cavity tuned tubes; however, they were not as stable as the external cavity tuned tubes.

It is, therefore, the principal object of the present invention to provide a novel reflex klyston tube which is grid gap tuned yet has the frequency stability in severe conditions of environment as does a fixed tuned klystron employing an external tuning cavity.

The main feature of the present invention is to provide a compressible main body portion which acts upon the grid headers to change the relative position of the grids and thereby cause the frequency to shift.

Another feature of the present invention is the provision of a rugged external tuning device which provides fine tuning and positive locking.

Other features and advantages of the present invention will become apparent from a perusal of the following specification taken in connection with the following drawings wherein the invention is embodied.

In the drawings, FIG. 1 is a perspective view of a reflex klystron showing the external tuning means as utilized,

FIG. 2 is a part longitudinal sectional view of a reflex klystron of the type utilized in the present invention,

FIG. 3 is a part sectional view taken along lines 33 of FIG. 2, and

FIG. 4 is an enlarged sectional view showing the utilization of the present invention in the cavity resonator of a reflex klystron.

Referring now to the drawings, the reference number 11 designates a housing or bulb portion of the novel tube incorporating this invention within which the cathode 12 is contained. Surrounding cathode 12 is a support assembly 13 which also serves as a focus electrode for the electron beam emitted from the cathode 12.

A hollow cylindrical anode drift tube 14 having a slightly conical or dished, washer-like header 15 assembled thereon as by brazing is inserted within a main body member 16, a U-shaped metal member having an aperture bored through the base of the U to form the central body portion of the present klystron. Housing portion 11 for the cathode assembly is secured as by brazing into one end of the aperture in main body portion member 16.

One end of the hollow drift tube 14 is provided with an accelerating grid 14' and the other end has a resonator grid 17 mounted thereon and spaced from an opposed grid 18 mounted on a conical dish-shaped header ring 19 secured to the inner end of a reflector housing portion 21 and further secured to the inside of the aperture through the main body member '16. The inner end of reflector housing portion 21 is secured as by brazing into the other end of the aperture through main body member 16 so that a resonator cavity is formed within the main body member defined by the conical dish 15, drift tube 14, grid 17, ring 19, grid 18, and the inside or side wall 10 of the aperture through main body portion 16. The

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reflector button 22 is supported by a cylinder 23 positioned within reflector housing 21. The main body member 16 is provided with an iris opening 26 and vacuum seal window 26' to provide an exit into a resonator 25 for energy developed by the klystron. A flange 27 is provided on resonator 25 for connection to the load circuit.

Positioned within a pair of aligned internally threaded apertures in the legs L and R of U-shaped body member 16, as best seen in FIG. 3, is a threaded tuning stud 31. Tuning stud 31 is captured within =leg L of main body member 16 by the threaded aperture therein and captured within leg R by an internally and externally threaded dif ferential tuning nut 32 which is in turn captured by the threaded aperture in leg R.

When it is desired to change the oscillation frequency of the present tube the mechanics of tuning are as follows. The tuning screw 31 is locked to the left leg of the body by a lock or jam nut 33. Then the differential screw 32 is turned thereby pulling together the legs of main body member 16. As this pressure is applied to the legs of body the round cavity is distorted due to a weakening of the base at 16' caused by aperture therethrough and becomes elliptical or egg shaped. This deformation, as best seen in FIGS. 3 and 4 in turn forces the anode header 15 and the reflector header 19 to become more conical or to bow more due to inward pressure and in turn moves the grid 17 away from grid 18 as shown greatly exaggerated in phantom by FIG. 4. As the gap between the grids 17 and 18 increases, the capacitance therebetween decreases, causing the frequency to increase. By turning the differential nut 32 in the opposite direction the frequency may, of course, be lowered. It is further noted that the volume of the cavity will decrease slightly when distorted thereby causing a decrease in inductance. The eflect of this will be to decrease the frequency and somewhat oflset the increase in frequency effected by increasing gap spacing. However, the increase in frequency due to the increased gap spacing will greatly overcome the change in inductance due to the reduced inductance and the reduction may be neglected.

Here is shown a rugged tunable reflex klystron suitable for utilization in most severe conditions of environment. It is rugged enough to prevent any change in frequency, or 'l megacycles stability) and further is sufficiently rugged to greatly reduce rnicrophonics generally found in gap-tuned reflex klystrons.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In an electron discharge device, a cavity resonator including an interaction gap defined by a pair of mutually opposing grid members, support means supporting said grid members, said cavity resonator including side walls to which said support means are secured, means mounted on said electron discharge device for distorting portions of the side walls of said cavity resonator thereby distorting said support means in such a manner that the spatial relation between said opposing grid members is changed thereby effecting a frequency change of the cavity resonator.

2. The apparatus according to claim 1 wherein said support means include at least one outwardly dished member, said outwardly dished member bowing outwardly in variable accordance with the amount of distorting on said side walls.

3. The apparatus according to claim 2 further including an apertured, U-shaped member, the wall portions of said ferential tuning screw 'is'threadedly captured by apertures in the legs of the U-shaped main body member to provide means for applying force to the lever arms for distorting the side walls of the cavity resonator.

5. In a high frequency apparatus including a tunable cavity resonator, said cavity resonator having a re-entrant portion and including a gap spacing for electromagnetic interaction with a beam of electrons passable therethrough, said cavity having side walls and end walls, at least one end wall being provided with an outwardly dished portion, said outwardly dished portions supported by the side walls of said cavity resonator, means for applying a force on the side walls to distort said side walls, the distortion in said side walls acting on said outwardly, dished portion causing them to bow in such a manner that the gap spacing is varied in variable accordance with amount of distortion in the side walls.

6. In an electron discharge device, a U-shaped member including an apertured base portion, the walls of the aperture within said base portion defining side walls of a cavity resonator, saidcavity resonator including an interaction gap defined bya pair of mutually opposing grid members, support means for supporting said grid members, said support means including at least one outwardly dished member, said outwardly dished member being supported by the walls of said cavity resonator, the legs of said U-shaped member including a dilferential tuning screw threadably captured by aperatures therein, said differential tuning screw providing means to apply force to the U-shaped arms, said U-shaped arms acting as lever arms to distort the side walls of said cavity resonator, the distortion in the side walls of said cavity resonator applying force to said outwardly dished member thereby causing said outwardly dished member to bow in variable accordance with the amount of distortion in said side walls thereby changing the spatial relation between opposing grid members, said spatial relation efiecting a frequency change of the cavity resonator.

7. In a tunable high frequency electron discharge device, a tunable cavity resonator, said cavity resonator being defined by a pair of spaced end portions interconnected by side wall portions, said end portions having a pair of aligned apertures for passage of a beam of electrons through said cavity resonator for electromagnetic interaction with the electric fields of said cavity resonator,

said cavity resonator having a reentrant wall portion projection generally inwardly of said resonator to concentrate the electric fields of said resonator and define an electromagnetic beam-field interaction gap in the path of the electron beam passable through said resonator, means coupled directly to the side wall portions of said cavity resonator for applying force on the side wall portions of said cavity resonator to distort said side wall portions, the

distortion'in said wall portions movably acting on said re-entrant wall portion causing said re-entrant wall portion to move in such a mannerthat the gap spacing is varied in variable accordance with the amount of distortion in the side wall portions.

8. The apparatus according to claim 7 wherein said means coupled to said side wall portions includes a pair of lever arms secured on the external portion of said cavity resonator to which force. is applied to distort said side walls.

9. The apparatus according to claim 8 wherein screw means are threadedly captured by threaded apertures in the free ends of said lever arms to provide means for applying force to the lever arms for distorting the side walls of the cavity resonator.

-10. The apparatus according to claim 9 wherein portions of said side walls are relatively thin with respect to adjacent portions of said side walls to allow distortion ofsaid side walls at the thin portions thereof.

References Cited in the file of this patent UNITED STATES PATENTS Canada Jan. 30, 1948

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