US2633556A

US2633556A - Millimeter wave generator

Info

Publication number: US2633556A
Application number: US240023A
Authority: US
Inventors: Beverly D Kumpfer
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-08-02
Filing date: 1951-08-02
Publication date: 1953-03-31
Anticipated expiration: 1970-03-31

Description

March 31, 1-953 B. D. KUMPFER 2,633,556

. MILLIMETER WAVE GENERATOR Filed Aug. 2, 1951 FIG. I

INVENTOR.

BEVERLY D. KUMPER Patented Mar. 31, 1953 MILLIMETER WAVE GENERATOR Beverly D. Kumpfer, Spring Lake Heights, N. J., assignor to the United States of America as represented by the Secretary of the Army Application August2, 1951, SeriallNo. 240,023

Claims. (Cl. 315-40) Thejinvention described herein may be manufactured and'used by or for the Government for governmental purposes, without the payment of any royalty thereon.

.The present invention relates to electron discharge devices of the magnetron type and more particularly to magnetrons for generating electrical oscillation having a wavelength of a few millimeters or less.

In a recent electronic development, the use of a metallic resonant structure in the amplifying mechanism of travelling wave amplifier tubes have been eliminated by employing two interacting electron streams travelling at different velocities. For a description and illustration of this development, reference is made to the publication of Proceedings of the I. R. E. of January 1949 and to the article entitled The Electron-WaveTube by Andrew V. Haefi'.

The most serious obstacle for employing magnetrons for generating oscillations of millimeter wavelength is the apparent necessity to use a plurality of metallic resonant structures of very small dimensions. This requirement arises from the fact that magnetron anode structures have to be arranged so that kinetic energy of electrons can be efliciently converted into the energy of the high frequency electric fields which are supported by these resonant structures. Because of the. required reduction in size when operating-at millimeter wavelength, the useful output power at millimeter wavelengths of conventional mag- .netrons is greatly reduced even when maximum emission current densities are approached. j "The. present invention contemplates and has as a primary object the provision of a magnetron tube of novel design capable of generating electrica1 oscillations of millimeter wavelength by utilizing two interacting electron streams travelling at different angular velocities. f It is a further object of my invention to provide a magnetron wherein the usual plurality .of resonant circuits is effectively replaced by a system of two rotating electron streams which interact with each other. --In accordance with the invention, a magnetron generator comprises a cylindrical anode anda pair ofcathodes centrally and axially positioned .within said anode.

For a better understanding of. the invention,

together with other and further objects thereof,

Each cathode isat a discretepotential with respect to the anode to produce two admixed rotating space clouds traLvel- (Granted under Title 35, U. S. Code (1952),

sec. 266) reference is had to the following description taken in connection with the accompanying drawing in which:

Figure 1 is a longitudinal sectional view taken substantially through the center of a magnetron made in accordance with the principles of my present invention.

Figure 2 is a transverse sectional view taken along line 22 of Figure 1;

Figure 3 illustrates another embodiment of the cathode structure employed in Figure 1; and

Figure 4 is a fragmentary view in cross section illustrating another embodiment of the single resonant structure employed in Figure 1.

Referring now to Figures 1 and 2 of the drawing, there is shown a magnetron 2 comprising an evacuated tubular anode structure 4 made of a cylinder of conducting material, such as copper. The upper and lower ends of cylindrical anode 4 are closed by upper and lower annular end plates 6 and 8 respectively. The end plates are formed of a suitable conducting material such as copper and are hermetically sealed into the. ends of anode 4. Depending outwardly from the inner periphery of upper end plate 6 and rigidly brazed thereto, is tubular sleeve I0, the upper end of which is provided with a glass seal l2 for sealing the discharge device after evacuation. Similarly, tubular sleeve [4 depends outwardly from the inner periphery of lower end plate 8 and is provided with glass seal 16.

Centrally and axially positioned within cylin} indirectly heated type, which are identical in construction and axially aligned. Cathode l8, hereinafter referred to as the upper cathode, comprises a cylindrical electronically conductive sleeve 22, preferably made of nickel," Said sleeve is coated externally with an electron emissive material as at 24. Disc-like end shield 26, here'- in conveniently integral with cathode sleeve 22, is provided proximal end plate 6, to'prevent emitted electrons from being DrQject'ed outwardly toward said end plate. As a means for supporting upper cathode I8 in position within the tube, there is provided a tubular Kovar{ member 28 whichisaxially aligned with tubular sleeve Ill. As illustrated, one end of tubular member ZLis .welded to end shield 26.

A'hea'ter so, which is positioned within ,u'pper cathode l8 and which is' energized by means of a heating battery 32, serves to maintain coated surface 24 at an emitting temperature. One terminal of the cathode heating element is connected to Kovar member 28 by being connected to .cathode sleeve 22 and the other terminal is connected to lead-in conductor 34 which extends through aperture 36 of end shield 25, and through "Kovar tubular member 28. A glass seal 3 between lead-in conductor 34 and tubular member 23 maintains the structure vacuum tight.

Cathode 2%, hereinafter referred to as the lowor cathode, is identical in construction with up per cathode l8 and is similarly provided with a cylindrical conductive sleeve 4% which is terminated proximal end plate 8 by disc-like end shield 42. Like upper cathode l8, sleeve 43 is coated with an electron emissive material as at- A 44. Tubular Kovar member 43 is provided to support lower cathode 2G in position and maintain it in spaced relationship with upper cathode I 8. As shown, tubular member 45 is axially plate 8. A heater 41, which is similar to heater 30 supra, is positioned within lower cathode 28 to maintain coated surface 44 at an "emitting temperature and is energized by means of heating battery 48 through lead-in conductor 58. Glass seal 52 between lead-in conductor 5!! and tubular member 46 maintains the structure vacuum tight.

Cathode i3 is maintained at a negative potentialEi with respect to-anode 4 by means of an appropriate voltage source 54 which is applied to cathode is by tubular member 28 through glass seal l2. Similarly, cathode 26 is maintained at a negative potential E2 with respect to anode 4 by means of voltage source 58 which is applied to cathode 2% through tubular member 55 and glassseal iii. B; may be slightly higher than E2, or vice versa. Cylindrical anode 4 is provided with a slot '58 open at both ends and axially parallel to the axis of said cylindrical anode; The depth of slot 58 radially fromthe inner periphery of anode 4 is preferably chosen to be eifectively one-quarter wavelength of the operating frequency so as to provide a resonant cavity therefor. If desirable, slot 58 may be a closed end resonator as shown at 58' in Figure 4, the axial length thereof being effectively one-half wavelength to form a resonantwaveguide sectionat the operating frequency.

In order to take power from the magnetron,

cylindrical anode 4 is. provided with a] second, radially disposed, coupling. slot 60, which is coupled and suitably matched to waveguide 182. The depth of slot E0 outwardly from the inner .pe-

riphery of anode 4 is preferably chosen to be effectively one-half wavelength of the operating 'frequency' As shown, coupling slot 50 is open .at both ends and is axially parallelto the axis .of cylindricalanode 4. A glass Window 64 sealed into the waveguide maintains the structure vacuum tight. Resonant slot 58 and output slot Bil may be positioned, relative to each other along '65 and 66 which maybe energized by any of the :means well known in the art not shown, Preferably, the flux lines should be concentrated in the interaction space 68, between cathodes l8 and 20 and cylindrical anode 4.

4 In operation, the discrete electron space clouds from the two cathodes are propagated in the interaction space at discrete angular velocities which may be calculated from the formula wherein E is the intensity of the electric field in the space between the anode and the cathode and B the value of the constant magnetic field. Thus the' electron space cloud from upper cathode [8 travels with an angular velocity and the electron space cloud from lower cathode 20 travels with an angular velocity Both electron streams are bunched or. density modulated by the single resonant circuit 58 in anode 4 in accordance with conventional'mag-J- netron operation. The admixed bunched streams then rotate around the interaction space and interact with each other. As ex lained by Haefi in the hereinabove mentioned article, the lower velocity stream gains energy from. the higher velocity stream in'the process of the space charge interaction without the use of a continuous resonant structure. A portion of the am:- plified energy is coupled out by output coupling slot 65 and theresidual energy in the two interacting streams is allowed to feed back around the anode structure to provide regeneration. Since only one resonant structure is required rather than a plurality thereof, the power output at millimeter wavelength operation is greatly increased. i Y Figure 3 illustrates two .identical helically wound filaments and 12 of the directly heated type which may be utilized in place ofthe cylindrical cathodes [8' and 20. Filaments Ill and 12 are insulated with respect to each other and may be coaxially mounted within and axially aligned ,with cylindrical anode 4. Voltage E1 isapplied between cathode ill and cylindrical anode 4 and voltage E2 is applied between cathode 12 and said anode. The windings of the helically-shaped filaments are so arranged that corresponding windings such as M and 16 are superimposed.

While there have been described what at pres.- ent are considered to be the preferred embodimerits of the invention, it will be understood by those'slcilled in the art that various changes and modifications may be made herein without de xparting' from the invention, and it is, therefore, aimed in the appended claims to cover all such modifications and changes as fall within the spirit and scope of the invention.

What is claimed is: v

1". An electron discharge device of the magnetron type comprising acylindrical anode including a pair of radical slots, a cathode assembly centrally positioned within said anode comprisiing axially spaced and electrically independent first and second electron emitting surfaces; said electron emitting surfaces being axially aligned with said anode for supplying electrons to the space between saidanode and said first and second electron emitting surfaces to produce aflrst and second electron space cloud, means supporting said electron'emitting surfaces in said axial spaced relationship, magnetic means adjacent said anode for producing a constant axial mag netic field in the space between said electron emitting surfaces and said anode, means in cir cuit with said anode and said first electron emitting surface for establishing a first electric field perpendicular to and cooperable with said magnetic field whereby said first electron space cloud is rotated at a first predetermined angular velocity, means in circuit with said anode and said second electron emitting surface for establishing a second electric field perpendicular to and cooperable with said magnetic field whereby said second electron space cloud is rotated at a second predetermined angular velocity.

2. An electron discharge device of the magnetron type comprising a cylindrical anode including a pair of radial slots, said slots being open at both ends and longitudinally parallel to the axis of said anode, a cathode assembly centrally positioned within said anode comprising axially spaced and electrically independent first and second conductive cylindrical sleeves, each of said sleeves being coaxial with said cylindrical anode, means supporting said sleeves in said axial spaced relationship, magnetic means ad =jacent said anode for producing a constant axial magnetic field in the space between said anode and said cathode assembly, means included in said cathode assembly for supplying electrons to the space between said anode and said first and second sleeves to produce a first and second electron space cloud, means connected between said first sleeve and said anode for establishing a first electric field perpendicular to and cooperable with said magnetic field whereby said first electron space'cloud is rotated at a first predetermined angular velocity, means connected between said second sleeve and said anode for establishing asecond electric field perpendicular to and cooperable with said magnetic field Whereby said secondelectron space cloud is rotated at a second predetermined angular velocity.

3. A magnetron device comprising a cylindrical anode including a pair of radial slots, said slots being open at both ends and longitudinally parallel to the axis of said anode, a cathode assembly centrally positioned within said anode comprising axially spaced and electrically independent first and second conductive cylindrical sleeves,

each of said sleeves being coaxial with said anode. means supporting said sleeves in said axial spaced relationship, magnetic means adjacent said anode for producing a constant axial magnetic field in the space between said anode and said cathode assembly, means included in said cathode assembly for supplying electrons to the space between said first and second sleeves and said anode to produce a first and second electron space cloud, 2. first source of direct-current potential coupled between said first sleeve and said anode to establish an electric field perpendicular to and cooperable with said magnetic field whereby said first space cloud is rotated at a first predetermined angularly velocity, and a second source of direct-current potential coupled between said second sleeve and said anode to establish an electric field perpendicular to and cooperable with said magnetic field whereby said second space cloud is rotated at a second predetermined angular velocity.

4. The electron discharge device set forth in claim 1 wherein the radial depth of one of said slots is substantially wavelength of the operating frequency and the radial depth of the other of said slots is substantially wavelength of the operating frequency.

5. The electron discharge device set forth in claim 1 wherein said slots are closed at both ends and are substantially wavelength of the operating frequency.

BEVERLY D. KUMPFER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,409,038 Hansell Oct. 8, 1946 2,423,716 McArthur July 8, 1947 2,429,291 Okress Oct. 21, 1947 2,438,194 Steele, Jr. et a1 Mar. 23, 1948 2,443,179 Beniofi June 15, 1948 2,452,077 Spencer Oct. 26, 1948 2,493,423 Spooner et al Jan. 3, 1950 2,513,933 Gurewitsch July 4, 1950