US2797349A - Ultra high frequency electron discharge devices - Google Patents

Description

L. PENSAK June 25, 1957 ULTRA HIGH FREQUENCY ELECTRON DISCHARGE DEVICES Original Filed Aug. 15, 1944 2 Sheets-Sheet 1 ury: 1 v3 1. 1.

I Em June; 25, 19 57 p s K 2,797,349

ULTRA HIGH FREQUENCY ELECTRON DISCHARGE DEVICES Original Filed Aug. 15, 1944 2 Sheets-Sheet 2 Lows FEMS/47K ULTRA HIGH FREQUENCY ELECTRON DISCHARGE nnvrcss Louis Pensak, Princeton Township, Mercer County, N. 1., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Army Application April 23, 1948, Serial No. 22,753, which is a division of application Serial No. 549,313, August 15, 1944, now Patent No. 2,481,026, dated September 26, 1949. Divided and this application October 31, 1951, Serial No. 254,077

Ciaims. (Cl. 313-263) My invention relates to electron discharge devices particularly useful at ultra high frequencies, and more particularly to such devices having high power output and which can be utilized with tunable cavity resonator circuits.

This application is a division of a copending application, Serial No. 22,753, filed April 23, 1948, filed in the names of Russell R. Law and myself, now Patent No. 2,599,263, issued June 3, 1952, and assigned to the same assignee as the present application, which, in turn, is a division of a copending application, Serial No. 549,513, filed August 15, 1944, now Patent No. 2,481,026, issued September 26, 1949.

Certain types of triode electron discharge devices having cathode, grid and anode electrodes provided with planar surfaces of disc-shape have been found satisfactory for moderate power at moderately high frequencies. However, as the power is raised the overall size of the tube and circuit, usually of the cavity resonator type, must diminish, thus bringing about a reduction in the power output. For example, inasmuch as the tube elements must be relatively small compared to a wavelength, at 3000 megacycles it would be inadvisable to use a cathode much smaller than one centimeter in diameter. Thus at 3000 megacycles, such a tube would be limited to peak power outputs of ten kilowatts.

While elongated electrode structures such as described and claimed in a copending application of Russell R, Law, Serial No. 542,717, filed June 29, 1944 now Patent No. 2,471,037, issued May 24, 1949, and assigned to the same assignee as the present application, permit extension of the dimensions of the circuit and tube elements along a longitudinal axis without affecting the frequency, the higher frequencies require smaller transverse cross sections, resulting in difiiculties of assembly and operation. As pointed out in a copending application of Russell R. Law, Serial No. 549,514, filed August 15, 1944, now Patent No. 2,501,181, issued March 31, 1950, and assigned to the same assignee as the present application, external circuits of satisfactory size and operated at a harmonic mode may be utilized, such circuits being of desirable size and tunable. For such operation, electron discharge devices having envelopes and suitable electrode connecting leads to be engaged by the cavity resonator circuits are required. Conducting flanges supporting and connected to the electrodes and sealed through the envelope of the tube oifer the most satisfactory low loss connecting means which can be merged into the cavity resonator circuit Walls. It is desirable to employ standard technique for the manufacture of such tubes if possible. It is also desirable to have the voltage nodes of the generated radio frequency voltages at the seals between the leads and the envelope to avoid voltage breakdown at the seals.

To eliminate or substantially reduce electron transit time difficulties, close spacing of the electrodes is necessary, introducing construction difficulties and increasing.

the problem of heat dissipation with its inherent deformation of electrodes due to temperature changes. Where long electrodes are utilized it is essential that cathode heating power be conserved, and to provide large power outputs a large cathode area is necessary.

It is, therefore, an object of my invention to provide an electron discharge device of improved design useful at ultra high frequencies.

A further object of my invention is to provide such a device capable of large power outputs.

A still further object of my invention is to provide such a device utilizing cavity resonators and in which electrodes are suitably supported from leads which can be merged into the cavity resonator walls.

More specifically, it is an object of my invention to provide such an electron discharge device which will operate in a mode such that at least one of the dimensions of the electrodes is independent of the frequency at which the device is to be operated.

A further object of my invention is to provide an electron discharge device which will permit the use of external circuits operated in a harmonic mode and which is so designed that the voltage nodes occur at the seals.

A still further specific object of my invention is to provide such a device in which close electrode spacing is possible but in which rigid support is obtained.

A still further object of my invention is to provide a cathode of comparatively large emitting area. These and other objects will appear hereinafter.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which: Fig. 1 is a section transverse to the longitudinal axis of an electron discharge device and its associated circuit claimed in said copending application Serial No. 549,513; Fig. 2 is a section taken along the line 2-2 of the electron discharge device shown in Fig. 1; Fig. 3 is a section taken transverse to the longitudinal axis of a modification of the electron discharge 'device shown in Fig. 1 and embodying my invention; Fig. 4 is a section taken along the line 4-4 of Fig. 3; and Fig. 5 is an exploded view of a cathode-grid arrangement embodying my invention.

The electron discharge devices disclosed include elongated linear electrodes provided with conducting leads and flanges which readily merge into the cavity resonator walls of cavity resonator circuits coupled to the electrodes.

Referring to Figs. 1 and 2, the electrode system comprises an indirectly heated cathode 10 having a cathode heater 11, an oppositely disposed anode 12 and an intermediate grid 13. The cathode is supported by means of conducting fingers or rods 15 from the cathode support 14 for reducing heat conduction from the cathode. The cathode 10 and support 14 are mounted in an elongated trough-like element 16 having secured to it a collar-member 17 provided with the transverse lip or fiange 18. Tubular elements 19, 20 and 21 extend through the elements 14 and 16 and provide apertures through which the cathode heater leads 22 and 24 extend, being sealed in by cup-shaped elements 23 and 25. The lead 22 is connected to one end of the cathode heater by loop 28 and the other end of the cathode heater is connected by means of the conductor 26 to lead 24, the cathode proper being connected to the lead 24 by means of the conducting loop 27. The sealed-off tubular extension 20 serves as the exhaust tube.

The grid 13 is supported from the elongated grid collar 29 and in turn is supported from the grid flange and lead 30 by means of the conducting fingers 31. The anode is supported within the elongated collar-like element 32 provided with the flange 33. Elongated collar members 34 and 35, preferably of glass are sealed between the lips 33, 30 and 18 to provide an envelope for the electrode elements 10, 13 and 12. The cathode and grid electrodes and the flanges connected to the electrodes have rounded ends, so that the outlines of these elements represent elongated ellipses.

' As shown in Fig. l, a cathode-grid cavity resonator 36 is coupled between the grid and the cathode and an output cavity resonator 37 is coupled between the grid and the anode. The walls of the resonators are flat sheetlike elements 44, 38 and 45 closed at their ends by means of the sliding closure members 51, 49, 48 and 50. Conpling between the resonators is accomplished by means of the coupling loop 46 and the output taken by means of the coaxial line and loop 47.

The grid flange 30 is directly connected to the intermediate Wall portion of the cavity resonators 38 by means of the spring fingers 39. The wall 44 is capacitively coupled to the spring fingers 43 contacting the flange 18 through the insulating collar 40 and the anode flange 33 is contacted by the spring fingers 42 coupled to the wall 45 through the insulating collar 41 preferably of mica. By this means it is possible to provide biasing voltages between the various electrodes by providing closed paths for the radio frequency currents flowing within the resonators. The mode of operation of the circuit associated with the electron discharge device shown in Figs. 1 and 2 is described in detail and claimed in the copending application of Law above referred to, Serial No. 549,514.

The cathode is made in a plurality of sections, as shown, to permit expansion and contraction of the various parts of the cathode without causing buckling and shorting between the electrode elements. The elements have curved surfaces to insure the expansion of the electrode surfaces in the same direction, thus avoiding shorts.

My invention i embodied in the modification shown in Figs. 3, 4, and 5, which provides greater cathode area and also utilizes unit construction. Such an arrangement facilitates construction of the eelctrodes and assembly of the device. The elongated hyperbolic transverse section of the electrode elements, which forms a part of my invention, insures that any bowing which occurs in the grid during operation will not cause shorting.

In the arrangement shown in Figs. 3 to 5, inclusive, nested electrodes are utilized, a wedge-shaped indirectly heated cathode 60 and a Vshaped foraminous grid 61 being positioned within a Vshaped channel in an anode The cathode, heater and grid elements shown in the exploded view in Fig. can be assembled as a unit and then assembled on the cathode support before being inserted together with similar units Within the tube envelope. Referring to Fig. 5, each cathode element includes a wedge-shaped shell 63 having outwardly bowed side surfaces connected by flat end surfaces, the shell being assembled over the heater 64 and secured to the transverse conducting enclosure member 66 of U-shaped cross section. One side of the cathode heater is connected to the support rod 65 and the other to the support rod 68. The support rod 65 is provided with an insulating collar 67 extending through member 66 and a second U-shaped conducting member 69, the conductor 65' being electrically connected to the cathode lead 67', insulating supported from the under side of the element 69, the element 66 being supported by means of the rod-like conducting finger 66 from the member 69. The conductor 68 is connected to the member 69 which is pro vided with a pair of ribbon-like supporting and connecting tabs or leads 70 and 71. The cathode and cathode heater support include an insulating member 72 having U-shaped supporting elements 73 and 74 and provided with end supporting elements 75 and 76. The members 73 and 74 are secured to the member 69, 7

Each element of the grid 61 is open at each end and has side surfaces which are bowed outwardly, like the bowed surfaces of the cathode 60. Each grid element is provided with strengthening ribs 77 and end ribs 78 and is supported from the box-like shield 79 having conducting legs 79 which are fastened to the eelments 75 and 76 to provide a unitary cathode-grid structure. In assembly the conductors 70 and 71 are welded to the elongated cathode supporting structure made up of central ele' ment 80 provided with collar 81 and flange 82. Tubular members 83 and 86 provide apertures through the element 80 through which the cathode heater and leads 84 and 87 extend and are sealed, the tube providing the exhaust tube which is sealed after exhaust. The conduc tor 84 is electrically connected to longitudinally extending conductor 88 to which each of the cathode heater leads 67' is connected. The conductor 87 by means of conductor 89 may be connected to one of the cathode elements 69, all of which are connected through the straps 70 and 71 to the flange 82, thus providing a circuit through all of the heaters in parallel. The grid is connected to the grid lead and flange 90 by means of the conducting fingers 91. The anode 62 is made up of a series of anode elements, each having a channel of Vshaped cross section open at each end, placed end-to-end to provide an openended elongated Vshaped channel. The opposed inner surfaces of the Vshaped channel of each element of anode 62 are bowed outwardly like the bowed surfaces of cathode 60 and grid 61. Since the surfaces of the cathode, grid and anode are all bowed, the danger of shorting of the electrodes during operation, due to unequal distortion upon thermal expansion, is minimized. The anode elements are supported from the elongated anode conducting element 92 provided with the collar 93 and flange 94. The insulating collars 95 and 96, preferably of glass, are sealed between the flanges 94, 90 and 82 to provide an envelope for the elements within the envelope.

The electrical length of the cathode is a transverse cross sectional length as shown in Fig. 3 and should not be more than one-quarter wave-length long to prevent nodes on the cathode proper. For 1200 megacycles a length of cathode of approximately six centimeters folded in the middle is the proper transverse length of section. The broad base for the cathode eliminates the necessity for support at the top of the cathode. This is also true of the grid. A mesh grid is preferably utilized to obtain proper lateral support. The grid supporting wires can provide the necessary grid strength.

While I have indicated the preferred embodiments of my invention of which I am now aware and have also indicated only one specific application for which my invention may be employed, it will be apparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of my invention as set forth in the appended claims.

What is claimed is:

1. An electron discharge device having a plurality of electrodes in superimposed relationship including a cath ode, the active surfaces of said electrodes having substantial length in one direction and similar Vshaped cross sections transverse to said direction, said surfaces being bowed outwardly, each of said electrodes being provided with a flange-like conductor, insulating means sealed between said flange-like conductors and providing part of an envelope for said electrodes.

2. An electron discharge device having cathode, grid and anode electrodes in superimposed relationship, the active surfaces of said electrodes having substantial length in one direction and similar Vshaped cross sections transverse to said direction, said surfaces being bowed outwardly, each of said electrodes being provided with a flange-like conductor, insulating collars sealed between said flange-like conductors and providing part of an envelope for said cathode, grid and anode electrodes.

3. An electron discharge device having cathode, grid and anode electrodes in superimposed relationship, the active surfaces of said electrodes having substantial length in one direction and similar V-shaped cross sections transverse to said direction, said surfaces being bowed outwardly, each of said electrodes being provided with a flange-like conductor, insulating collars sealed between said flange-like conductors and providing part of an envelope for said cathode, grid and anode electrodes, said electrodes, conductors and collars being elongated in said direction.

4. An electrode for an electron discharge device comprising a member having substantial length in one direction, open ends in said direction, and a V-shaped cross section in a direction transverse to said one direction, the sides of said V-shaped cross section being bowed outwardly.

5. A cathode for an electron discharge device comprising a sheet metal member having substantial length in one direction and a V-shaped cross section in a direction transverse to said one direction, the sides of said V-shaped cross section being bowed outwardly.

6. A grid for an electron discharge device comprising a forarninous member having substantial length in one direction, open ends in said direction and a V-shaped cross section in a direction transverse to said one direction, the sides of said V-shaped cross section being bowed outwardly.

7. An anode for an electron discharge device comprising a member having an open-ended elongated channel of V-shaped transverse cross section, the sides of said channel being bowed outwardly.

8. An electron discharge device having elongated cathode, grid and anode electrodes in superimposed relationship, said anode electrode having an elongated channel of V-shaped transverse cross section the sides of which are bowed outwardly, said grid and cathode electrodes being positioned in said channel and having V-shaped transverse cross Sections conforming to the bowed shape of said channel walls.

9. An electron dis-charge device having elongated cathode and grid electrodes in close-spaced superimposed relationship, the active surfaces of said electrodes having substantial length in one direction and similar V-shaped cross sections transverse to said direction, said surfaces being bowed outwardly.

10. An electrode for an electron discharge device comprising a series of open-ended V-shaped electrode elements having outwardly-bowed sides, said elements being arranged end-to-end to form an elongated member of V-shaped cross-section.

References Cited in the file of this patent UNITED STATES PATENTS 1,565,708 Bullimore Dec. 15, 1925 1,628,982 Hulsizer May 17, 1927 1,718,632 Bullimore June 25, 1929 2,197,945 Hull et al. Feb. 8, 1938 2,235,414 White Mar. 18, 1941 2,599,263 Law June 3, 1952 FOREIGN PATENTS 217,256 Great Britain June 4, 1924 237,053 Great Britain July 23, 1925 251,073 Great Britain Apr. 29, 1926 253,668 Great Britain June 24, 1926 889,003 France Sept. 20, 1943

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