US2843794A - Tuning means for reflex klystrons - Google Patents

Description

July 15, 1958 R. c. HERGENROTHER 2,843,794

TUNING MEANS FOR REFLEX KLYsTRoNs Filed oct. 14, 1954 2 sheet-sheet 1 Filed Oct. 14, 1954 July 15, 195s RQ C. HEGENROTHER 2,843,794

TUNING MEANS FOR REFLEX KLYSTRONS 2 Sheets-Sheet 2 /N VEN T01? PUDOLF C. MERGE/women Byffw-w A TTolPNL-V 2,843,794 Patented July 15, 1958 TUNING lVIEANS FOR REFLEX KLYSTRONS Rudolf C. Hergenrother, West Newton, Mass., assignor to Raytheon Manufacturing Company, Waltham, Mass., a corporation of Delaware Application October 14, 1954, Serial No. 462,353

4 Claims. (Cl. 315-5.22)

This invention relates to rapid mechanical tuning structures for rellex klystrons.

In some applications of radio frequency local osciland the anode block that provides a short circuit at the operating frequency while keeping the plunger free to move relative to the anode block. The radio frequency short is provided to prevent leakage of the energy past the plunger. This non-contacting short circuit can best be designed as described in an article entitled Broad band non-contacting short circuits for co- -axial lines, by William H. Huggins in the Proceedings of the I. R. E. for September 1947, at page 906i. A grid 25 is mounted across the bottom of an axial openl ing 26 in the plunger 20. A repeller electrode 27 is lators, such as in a search radar receiver, it is desirable to tune the oscillator over its entire usable frequency range in a short time interval. The conventional internal-cavity reflex klystron can be tuned over a relatively small part of its tuning range by means of its repeller voltage but a major change in frequency requires a change in the eiective cavity size.V This is accomplished by a mechanical tuning mechanism. Usually this tuning mechanism produces an elastic deformation of some component part of the cavity, and the tube is severely limited as to the speed of the tuning operation and the total number of tuning oper-ations which can he performed before the elastic fatigue causes mechanical failure.

This invention provides a tuning mechanism for an internal-cavity rellex klystron that permits the tube to be operated for more than 100,000,000 tuning cycles at speeds as high as 60 complete sweeps of the entire tuning frequency r-ange in one second. This is accomplished by the use of capacity tuning across an adjustable interaction-gap spacing. This gap spacing is made adjustable by forming the roof of the cavity as a non-contacting short-circuiting piston that carries the second interaction-gap grid and the repeller. The piston is sufticiently broad` band to cover the required tuning range.

Other and further objects and advantages of the invention will be apparent as the description thereof progresses, reference being had to the accompanying dr-awings wherein:

Fig. 1 lis a sectional view of a klystron constructed according to the invention;

Fig. 2 is an enlarged view of the tuning structure shown in Fig. l; and

Fig. 3 is a section taken along the line 3--3 of Fig. 1.

in Fig. l the reference numeral 10 designates the anode block formed from a piece of conductive material such, as copper, to which is attached a base 11, shown broken away, through which the different electrodes are connected to the outer circuit. A cathode sleeve 12 is mounted in a disc 13 that is insulatedly mounted on the anode block 10 by means of a dielectric disc 14. The cathode is formed with an inwardly curved spherical surface 15 which carries the emissive coating 16. A ilament 17 is mounted within the cathode sleeve 12 to provide the necessary heat. The anode proper is in the form of a irst grid 18 with the center portion bent upward away from the cathode 15. A plunger 20 is mounted within an opening 21 in the anode block 10 and is supported by a spring assembly 22 in such a manner that it may be moved axially within the opening without touching the walls of the opening 21. The lower end 24 of the plunger 20 is formed of two pieces so shaped as to provide a broad band non-contacting short circuit for the coaxial transmission line formed by the plunger 20 mounted within the opening 26 and insulated from the plunger 20 by a dielectric sleeve 28. The repeller electrode is preferably formed with a cup 30 at its lower end. The repeller is connected to a source of potential by means of a conductor 31 passing through an insulating bushing 31a in the plunger 20.

The construction ofthe plunger 20 and the repeller 27 are best seen in Fig. 2. The manner in which the plunger 20 is mounted on the anode block 10 by means of the spring assembly 22 is best seen in Fig. 3. The plunger 20 is brought out to the outside through a bushing 32 and is attached to a sylphon bellows 33 by means of a collar 33a. The bellows is in turn attached to the cylindrical housing 34 of the spring assembly 22. This housing is in turn attached to the anode `block 10 by means of a series of vacuum tight seals formed in any of the well-known ways. The plunger20 is driven axially by a coil 35 attached to its upper end and mounted in the field of a magnet 36. The coil 35 is supplied with an alternating current at the desired modulating frequency which may conveniently be cycles per second from a source 37. The driving means shown is intended to operate like that of a loud speaker. However, any convenient means for producing a reciprocating axial motion of the plunger may be used. The output of the klystron oscillator is most vconveniently obtained through a wedge-shaped opening 38 in the anode block 10 with the apex of the wedgeshaped opening 38 at the space between the grids 18 and 25. This opening 38 is sealed hermetically by a glass window 40 in an iris 41 formed in a metallic cap 42. A groove 43 is formed in the anode block 10 about the openingl 38 and so dimensioned as to Vform a choke at the operating frequency of the oscillator so that a wave guide may be attached to the iris to transmit the oscillator output to other equipment where it may be used.

The spring assembly 22 shown in Fig. 3 is composed of a series of S-shaped springs 44 attached at their midportion to the plunger 20 by means of rings 45 and at their outer ends to a cylindrical shell 46 by means of rings 47. This mounting structure is designed as an elastic system having a high compliance along the axis of the tube and Va low compliance in the perpendicular direction. The elastic limit should, of course, exceed the expected displacement of the plunger which, in a representative case, is of the order of one thousandths of an inch. The resonant frequency of the structure should exceed the expected highest modulation rate. As the springs 44 form part of the heat conduction path from the second grid to the anode block, the total crosssectional area of the springs should be as large as required to transmit the expected heat. However, the crosssectional area of a single spring also affects the compliance of the spring. The two factors can he balanced to disspate the required heat through a spring structure of the required compliance.

This invention is not limited to the particular details of construction, materials and processes described, as many equivalents will suggest themselves to those skilled in the art. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

1. A mechanically tunable klystron oscillator comprising a cathode, an anode, first and second grids, a reflector, a plunger movably mounted in an opening in said anode, the inner end of said plunger being formed with a cavity' opening tothe outer surface of the plunger and so diminished as to form a non-contacting short across the opening in the anode, said reflector being insulatedly mounted on said plunger, said second grid beingV mounted on said plunger, and means for causing axial movement of said plunger so as to move the second grid with respect to the trst grid to vary the operating frequency. i 2. A mechanically tunable klystron oscillator comprising a cathode,4 and anode, iirst and second grids, a reflector, a plunger movably mounted in an opening in said anode, the inner end of said plunger being formed with a cavity opening to the outer surface of the plunger and so diminished as to form a non-contacting short across the opening in the anode, said reflector being insulatedly mounted on said plunger, said second grid being mounted on said plunger, and means for causing axial movement of said plunger so as to move the second grid with respect to the first grid to vary the operating frequency comprising a coil attached to said plunger and mounted within the field of a magnet and supplied with alternating eurent.

3. A mechanically tunable klystron oscillator comprising a cathode, and anode, iirst and second grids, a

reflector, a plunger movably mounted in an opening in said anode by means of at least one S-shaped spring, the inner end of said plunger being formed with a cavity opening to the outer surface of the plunger and so diminished as to form a non-contacting short across the opening in the anode, said reector being insulatedly mounted on said plunger, said second grid being mounted on said plunger, and means for causing axial movement of said plunger so as to move the second gridfwith respect to the irst grid to vary the operating frequency.

4. A mechanically tunable klystron oscillator comprising a cathode, an anode, first and second grids, a reflector, a plunger movably mounted in an opening in said anode by means of at least one S-shaped spring, the inner end of said plunger being constructed to form a non-contacting short with said opening, said reflector being insulatedly mounted on said plunger, said second grid being mounted on said plunger, and means for causing axial movement of said plunger so as to move the second grid with respect to the irst grid to vary the operating frequency comprising a coil attached to said plunger and mounted within the iield of a magnet and supplied With alternating current.

References` Cited in the iile of this patent UNITED STATES PATENTS 2,419,121 Clilord Apr. 15, 1947 2,429,243 Snow et al. Oct. 21, 1947 2,513,277 Best July 4, 1950 2,651,738 Ebers Sept. 8, 1953

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