US2481026A

US2481026A - Ultra high frequency electron discharge device having elongated electrodes

Info

Publication number: US2481026A
Application number: US549513A
Authority: US
Inventors: Russell R Law; Pensak Louis
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1944-08-15
Filing date: 1944-08-15
Publication date: 1949-09-06
Anticipated expiration: 1966-09-06

Description

ET AL Sept- 6, R R LAW ULTRA HIGH FREQUENCY ELECTRON DISCHARG DEVICE HAVING BLONGATED ELECTRODES 2 Sheets-Sheet 1 Filed Aug. 15. 1944 m mn fmww

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Sept. 6, 1949. R. R. LAW ErAl. 2,481,026

ULTRA HIGH FREQUENCY ELECTRON DISCHARGE DEVICE HAVING ELONGATED ELECTRODES 2 Sheets-Sheet 2 Filed Aug. 15, 1944 ATTORNEY Patented Sept. 6, 1949 UNITED STATES PATENT OFFICE ULTRA HIGH FREQUENCY ELECTRON DIS- CHARGE DEVICE HAVING ELONGATED ELECTBODES Russell R. Law and Louis Penlak, Princeton, N. J..

ignore to Radio Corporation of America, a corporation, of Delaware Our 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.

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, flied June 29, 1944, now U. S. Patent No. 2,471,037 granted 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 aecting the frequency, the higher frequencies require smaller transverse cross sections, resulting in diiculties of assembly and operation. As pointed out in a copending application of Russell R. Law, Serial No. 549,514. filed August 15, 1944, 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 offer 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 rf 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 diiiiculties, 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 our invention to provide an electron discharge device of improved design useful at ultra high frequencies, more specifically in the range above 1000 megacycles.

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

A still further object of our 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 our invention to provide auch an electron discharge device which will operate in a mode such that at least one of the dimensions of the electrodes is independent oi' the frequency at which the device is to be operated.

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

The novel features which we believe to be characteristic oi' our 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 Figure 1 is a section transverse to the longitudinal axis of an electron discharge device made according to our invention and its associated circuit. Figure 2 is a section taken along the line 2-2 of the electron discharge device shown in Figure 1. Figure 3 is a section taken transverse to the longitudinal axis of a modification of the electron discharge device shown in Figure 1, Figure 4 is a section taken along the line 4 4 of Figure 3, and Figure 5 is an exploded view of the unit cathode-grid arrangement made according to our invention.

An electron discharge device made according U6 to our invention includes elongated linear elec- `with the transverse lip or flange IB.

trodes provided with conducting leads and flanges which readily merge into the cavity resonator walls of cavity resonator circuits coupled to the electrodes.

Referring to Figures 1 and 2, the electrode system comprises an indirectly heated cathode I having a cathode heater Il, an oppositely disposed anode I2 and an intermediate grid I3. The cathode is supported by means of conducting fingers or rods I5 from the cathode support I4 for reducing heat conduction from the cathode. The cathode I0 and support I4 are mounted in an elongated trough-shaped element I6 having secured to it a collar-member I1 provided Tubular elements I9, and 2| extend through the elements I4 and I6 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 21. The sealed-off tubular extension 20 serves as the exhaust tube.

The grid I3 is supported from the elongated grid collar 2S and in turn is supported from the grid flange and lead 39 by means of the conducting iingers 3|. The anode is supported Within the elongated collar element 32 provided with the flange 33. Elongated

collar members

34 and 35. preferably of glass, are sealed between the lips 33, and I9 to provide an envelope for the electrode elements I0, I3 and I2, 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 Figure 1, a cathode-grid cavity resonator 36 is coupled between the grid and the cathode and an output cavity resonator 31 is coupled between the grid and the anode. The walls of the resonators are flat sheet-

like elements

44, 33 and 45 closed at their ends by means of the sliding closure members- 5I, 49, 4B and 50. Coupling between the resonators is accomplished by means of the coupling loop 49 and the output taken by means of the coaxial line and loop 41.

The grid flange 30 is directly connected to the intermediate wall portion of the cavity reso-` nators 38 by means of the spring i'lngers 39. The wall 44 is capacitively coupled to the spring fingers 43 contacting the flange I9 through the insulating collar 40 and the anode flange 33 is contacted by the spring fingers 42 coupled to the wail 45 through the insulating collar 4I, 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 oi the circuit associated with the electron discharge device shown in Figures 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.

The modication shown in Figures 3, 4 and 5 provides greater cathode area and utilizes unit construction. Such an arrangement facilitates construction of the electrodes and assembly of the device. The elongated hyperbolic transverse section of the electrode elements insures that any bowing which occurs in the grid will not cause shorting.

In the arrangement shown in Figures 3 to 5, inclusive, nested electrodes are utilized, an indirectly heated cathode 69 and grid 9| being positioned within the inverted V-shaped anode 62.

The indirectly heated cathode and grid shown in the exploded view in Figure 5 can be assembled as a unit and then assembled on the cathode support before being inserted within the tube envelope. Referring to Figure 5, the cathode includes the tent-shaped shell 93 which is assembled over the heater 34 and secured to the transverse conducting enclosure member 63. 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 61 extending through both elements 6B and G9, the conductor 65 being electrically connected to the cathode lead 31', insulatingly supported from the under side of the element 69. the element 39 being supported by means oi' the conducting fingers 69' from the member 69. The conductor 93 is connected to the member B9 which is provided with a pair o! ribbon-like connecting leads 1I! and 1i. The cathode and cathode heater support include an insulating member 12 having U-shaped supporting elements 13 and 14 and provided with end supporting elements 15 and 19. Th'e members 13 and 14 are secured to the member 69. The grid BI provided with strengthening rib 11 and end rib 13 is supported from the box-like shield 19 having conducting legs 3D and 9| which are fastened to the elements 15 and 19 to provide a unitary cathode-grid structure. In assembly the conductors 'lil and 1i are welded to the elongated cathode supporting element 39 provided with collar 9| and ilange 92. Tubular members 83 and 33 provide apertures through the member 30 through which the cathode heater and leads 94 and 31 extend and are sealed, the tube l5 providing the exhaust tube which is sealed after exhaust. The conductor 94 is electrically connected to longitudinally extending conductor 3l to which each of the cathode heater leads 91' is connected. The conductor 91 by means of conductor 99 may be connected to one of the cathode elements 69, all o! which are connected through the straps 11| and 1I to the conductor 99, thus providing a circuit through all of the heaters in parallel. The grid is connected to the grid lead and aange by means o! the conducting rlngers 9| and the anode is supported from the elongated anode conducting element 99 provided with the collar 93 and flange 94. The insulating collars 95 and 9|. preferably of glass, are sealed between the flanges to provide an envelope for the elements within the envelope.

The electrical length or the cathode is a cross sectional length and should not be more than one-quarter wavelength 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 oi' s ection. The broad base for the cathode eliminates the necessity for support at the top of the cathode. This is also true or the grid. A mesh grid is preferably utilized to obtain proper lateral support. The grid supporting wires can provide the necessary grid strength.

In our izo-pending application Serial No. 22,753, tiled April 23, i948, which application is a division of the present application and assigned to the same assignee, we have made claims to the subject matter of Figures 3, 4 and 5.

With the electron discharge device shown in Figures l and 2 and utilizing the circuit shown in Figure 1, it is possible to operate the tube and circuit between a range oi' 1320 and l2050 megacycles, a peak power output of 26 kilowatts being obtained at 1300 megacycles at about six kilovolt anode potential, the output being limited only by radio frequency spark-over.

While we have indicated the preferred embodiments oi' our invention or which we are now aware and have also indicated only one specic application for which our invention may be employed, it will be apparent that our 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 ior which it is employed without departing from the scope ot our invention as set forth in the appended claims.

What we claim as new is:

l. An electron discharge device having cathode, grid and anode electrodes with elongated active surfaces in opposed relationship. each of said electrodes being provided with an elongated supporting conductor disposed with its longitudinal axis parallel to the longitudinal axes of said grid, cathode and anode electrodes, and elongated insulating collar elements hermetically sealed between said flange-supporting conductors to provide an envelope for said cathode, grid and anode electrodes.

2. An electron discharge device having elongated cathode, grid and anode electrodes in superimposed relationship, each of said electrodes being provided with flange-shaped supporting conductors parallel to the longitudinal axes o! said grid, cathode and anode electrodes. insulating collar-like elements hermetically sealed between said iiange-shaped supporting conductors to provide an envelope i'or said cathode, grid and anode electrodes, said cathode electrode comprising a plurality of adjacent indirectly -heated units electrically connected together by one of said flange-shaped supporting conductors.

3. An electron discharge device having elongated cathode, grid and anode electrodes in superimposed relationship, each of said electrodes being provided with Bange-shaped supporting conductors parallel to the longitudinal axes of -said grid, cathode and anode electrodes, insulating collar elements hermetically sealed between said flange-shaped supporting conductors to provide an envelope for said cathode, grid and anode electrodes, said cathode electrode comprising a plurality of indirectly lheated units, each unit being supported by a plurality of conducting eiements of small transverse cross section compared to said unit and conducting means parallel to the longitudinal axis ci said electrodes positioned between the harige-shaped conducting member for supporting said cathode and electrically connected .to all of the conducting elements of small transverse cross-section.

4. An electron discharge device having elongated cathode, grid and anode electrodes in superimposed relationship, each oi said electrodes being provided with flange-shaped supporting conductors transverse to a plane passing through the longitudinal axes o! said grid. cathode and anode electrodes, insulating collar elements hermetically sealed between said flange-shaped supporting conductors to provide an envelope ior said cathode, grid and anode electrodes, said anode electrode comprising an elongated troughshaped conducting element extending within the envelope toward the grid and cathode.

5. An electron discharge device having elongated cathode, grid and anode electrodes in superimposed relationship. each of said electrodes being provided with flange-shaped supporting conductors transverse to ya plane passing through the longitudinal axes of said grid, cathode and anode electrodes, insulating collar elements hermetically sealed between said ii-ange-shaped supporting conductors to provide an envelope for said cathode, grid and anode electrodes, said grid electrode including a collar member closed adjacent the anode by mesh material fixed to one edge and having along its other edge a plurality of conducting ribbons securing said collar member to the grid flange.

6. An electron discharge device having a plurality of elongated electrodes in superimposed relationship, each of said electrodes being provided with iiange-shaped supporting conductors parallel to the longitudinal axes of said electrodes, an insulating collar element hermetically sealed between a pair of flange-shaped supporting conductors to provide an envelope for said electrodes, one of said electrodes being a cathode, and a conducting element supported by said cathode `iiangeshaped supporting conductors and forming part oi' the envelope wall, said conducting element being provided with tubular members opening into lthe interior of said envelope and extending outwardly therefrom and cathode heater leads insulatingly and hermetically sealed through said tubular members.

7. An electron discharge device having elongated cathode, grid and anode electrodes mounted in superimposed relationship, said anode being of trough-shaped formation extending inwardly of said device, the bottom of said troughshaped anode serving as the active surface of said anode, said cathode comprising a plurality oi' like elements and a common heater extending through all of said elements. an elongated collar member positioned parallel to said cathode and conductors extending between one edge oi said collar element and said cathode elements for supporting said cathode elements, said grid electrode having a ioraminous portion between said cathode and the active surface of said anode, said anode, grid, and cathode electrodes having Bange-shaped supporting conductors extending parallel to the longer axes of said electrodes and insulating collar elements hermetically sealed between a pair o! flange-shaped supporting conductors to provide an envelope for said electrodes.

8. An electron discharge device having a plurality of elongated electrodes mounted in superimposed relationship, each of said electrodes being provided with flange-shaped supporting conductors parallel to the longer axes of said electrodes, an insulating collar element hermeticali! sealed between a pair of flange-shaped supporting conductors to -provide an envelope for said electrodes, one of said electrodes being the cathode. and a danse-shaped supporting conductor forming part of the envelope wall connected to said cathode, said conductor being provided with tubul-ar members opening into the interior oi said envelope and extending outwardly 7 therefrom and cathode heater leads lnsulatlnsly and hermetlcally sealed through said tubular members, said cathode comprising a plurality of like elements each of which is supported from said conductor by rod-shaped conductors extending between the cathode elements and the The following references are of record ln the 111e of this patent:

8 UNITED STATES PATENTS Number 2,411,194 a ma mu Name Debe Knoll Sept. 13. 1038 Haal! et al Dec. 1'7, 1040 Hue!! Mar. 19, 1041 Huet! Apr. 22, 1941 McArthur July 10, 1044 Bondley Jan. 16, 1945 Begerntrom, Jr. Jan. 1, 1946 Heen May 21, 1946 Whlnnery July 18, 1946 Gurewltsch Oct. 0, 1946 Bessa Nov. 10, 1948 Rhin. TIM- !I'I 194'!