US2508473A - Electron discharge device - Google Patents

Description

y 3, 1950 w. E. SHOUPP 2,508,473

ELECTRON DISCHARGE DEVICE Filed May 10, 1947 INVENTOR 74 .5. SHOUPP.

BY WWW ATTORNEY fiatented May 23,

UNITED STATE- T T crass ELECTRON DISCHARGE DEVICE William E. Shoupp, Wilkinsburg, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 10, 1947,- Serial No. 747,254

4 Claims. (01. 250-275) This invention relates to electron discharge devices generally referred to as magnetrons, and more particularly to tuning means for the same.

Even though improved manufacturing processes have attained more accurate fabrication of magnetrons, the tolerances necessarily allowed, or other causes, introduce frequency differences in 'magnetrons, which are even more aggravated in connection with production of oscillations of extremely short wave length, especially where the wave length is measured by not more than one digit in centimeters. Tuning of the magnetron to an intended precise or narrow band frequency after the magnetron is entirely assembled, on test or in use, is highly desirable. It is likewise desirable to be able to tune a magnetron while in use, from one precise frequency to another. Attempts have been made heretofore to obtain tuning by mechanical means within the magnetron operated by external control.

The present invention relates to and has for its object the tuning of a magnetron by electronic means, and more definitely, tuning by injecting electrons into the capacitative elements of a magnetron thereby altering resonant frequency of the operating element or elements. According to my invention this may be done by placing a special or auxiliary cathode above the oscill'ating elements of the magnetron anode and putting a modulation voltage between said cathode and the magnetron anode. The electrons from the auxiliary cathode will be drawn toward the anode and will enter the oscillating cavities and,

if the frequency is somewhat less than the Larmor frequency, the electrons will have small radial amplitude due to the very strong magnetic field applied for magnetron operation and will travel in tight helices the general directions of which are roughly straight paths. I propose using the presence of these electrons between the capacitative elements of the inherent resonant circuits to cause the desired change in resonant frequency of the magnetron due to alterations of the dielectric constant and thereby obtain a frequency shift or tuning.

In .addition to the broad object of obtaining electronic tuning, the invention contemplates obtaining frequency shift in proportion to electron current and readily controlled modulation power supply therefor.

Other objects of the invention will appear to those skilled in the art to which it appertains, as the description proceeds, both by direct recitation thereof and by implication from the context.

Referring to the accompanying drawing in 2 which like numerals of reference indicate similar parts throughout the several views:

Figure. 1 is an axially longitudinal section of a 1, but with the cover or end plate removed, as on line IIII of Figure 1;

Figure 3 is an enlarged detail section of a portion of the auxiliary or tuning cathode at one electron emitting area and showing an associated portion of the anode, as on line III--III of Figure 5.;

Figure 4 is a detail sectional view of a portion of the anode on the same scale as Figure 3 taken on line IV-IV of Figure 3; and

Figure 5 is an underneath view of the auxiliary cathode showing the several emitting areas thereof.

In the specific embodiment of the invention illustrated in the several figures of the drawing, the reference numeral l0 designates a cylindrical metallic magnetron body, the ends whereof have cover or end plates ll sealed thereon that the interior may be evacuated. Within and as an integral part of said body is the usual'magnetron anode structure l2 of generally cylindrical shape but shorter than the outer part of the body so as toprovide end spaces l3 between th anode and said end plates l I. The anode structure is axially hollow to provide a cathode cavity and radiating from this cathode cavity are a plurality of cavities l4 constituting cavity resonators each having, in. the form shown, a cylindrical portion parallel to.

the cathode cavity and each cylindrical portion having a longitudinal constricted capacitative slot:

spaces l3. The ends of the cathode cavity and. the ends of said resonant cavities likewise open 1 into the end spaces l3.

An indirectly heated cathode l6 passes axially through the cathode cavity, adequately spaced from the anode and supported as usual fromlead-in rods ll entering the end cavities at the An output loop I8 is situated in sides thereof. one of the resonant cavities l4, passing out through the side wall of the body II] in accordance with usual practice. The size and. shape of the magnetron body, the end spaces, anode, cathode and leads above described are preferably all substantially in accordance with prior art pracoxides, are examples.

tice,.in consequence of which the pole pieces of the magnet, not shown, will have the same relation to the magnetron and its anode as exists in magnetrons as heretofore used. 7 In carrying out the present invention an auxiliary cathode IQ, of generally ring or doughnut stitute the capacitative elements and said slots shape, is shown concentrically situated in one of said end spaces l3, and in this instance, is located in the upper one of said spaces. The said auxiliary cathode occupies a position overlying the upper ends of the anode slots and preferably" has a radial width substantially equalize: the radial length of said slots. Thus, while the auxiliary cathode overlies those" portions of "the anode intervening between the slotsgitdoes niot overlie other portions of the anodenor'does'it overlie the generally cylindrical portion of thecavities constituting the cavity resonators. V

Said auxiliary cathode is shown as acasing comprising a substantially flat, washer-like under wallzllv and a flanged toroidal upper wall 2|, the flanges 22 of which are secured to the upper flat: marginal surfaces of the under wall; The toroidal wall is split radially. at one part thereof so as to provide separated ends 23 therefore which face towardeach other. Coaxially within said toroidal wall 2| and spaced abovethe-I flat under wall is a heater 24,. here shown as. a

. or auxiliary cathode casing contain a suitable electrical insulation material 26 for maintaining desired electrical isolation of the heater, except where attached at its one end, from saidcasing of the auxiliary cathode.

Support for and electrical connection to the auxiliary cathode casing is obtainedby anotherradially disposed lead-in rod or Wire 2?; For n that purpose a partial sleeve'28 is shown integral with and projecting radially from said torus and this sleeve i in turn soldered or otherwise se cured on the end portion'of the 'lead-inrod or wire: 21. This lead-in rod l'lv constitutes electrical connection b'oth'for the auxiliary cathodeand for one end of the heater. The other oi" first-mentioned'lead-in' rod 'connects onlywith theother end of the heater so'as to obtain a complete heater circuit to the exterior. Insu lative mounting and passage of both leadin wires is alike and accords with prior art practice for lead-in Wires as to construction, so requires no elaboration herein. V

On the under face of the flat under wall 20 of. the auxiliary cathode, at the areas directly, overlying the upper ends of the 'slots' I5 of-the anode, are electron emissive patches 29. These patches may be of any appropriate material for copious emission of electrons, of which alkaline earths, such as barium andstrontium or their By virtue of the focusing ofthe magnetic field and the fact that the re.-' stricted emissive areas or patches are directly. over the slots of the anode, emissionis beamed. into said slots with negligible spreading of the beam or scattering of the electrons. The elec-' trons will be collected'at, the far end of anode block. The parallel, walls forming thefslots contd'the fact that while electrons are emitted from the main cathode IS in a direction radially of the anode body, the electrons from the auxiliary cathode" l9- are emitted in an axial direction of the anodehbody, 7

"Frequency modulation is, therefore, in consequence of; the structure described above, produced electronically by means of a separate modulation power supply used in conjunction with the auxiliary cathode, and without need for any moving mechanical parts; in the magnetron.

I: claim:

1. A magnetron having an anode providing. a cathode cavity and a series of cavity resonators radiating therefrom: and having end spaces at. op,- posite ends'of. said anode, said resonators having: substantially parallel. capacitative elements radir.

ating from and next the parts thereof toward;

said cathode cavity, amain cathode in said oath-1 ode cavity, and an auxiliary ring-shaped cathode.

in one of: said end spacescoaxial with saidcath ode cavity and. overlying said anode only. to ex-v tend from the said cathodecavity to substantially;

the most distant part therefrom of: said parallel capacitative elements, the endsof the resonators:

being otherwise open tosai'd end-spaces.

' 2.A magnetron having. an anode providing a.

the-parts thereof toward said cathode cavity,- a.

main cathode in said cathode cavity, and an aux ili'ary ring-shaped cathode in one of said end.

spaces coaxial with said cathode cavity and overlying said anode only to an extent from the said; cathodecavity tozsubstantially the most distant part therefrom of said capacitative elements, the;

endsof the resonators being otherwise open. to.

said end spaces, andssaid auxiliary: cathode have inga plurality of equallyspaced electron emissive; patches equal'in number to the number of. cavity" resonators in saidseries; i

3; A magnetron having an anodevproviding a. cathode cavity and a circular series of" evenly' spaced cavity resonatorsradiating therefrom:and having end'spaces at opposite ends of said anode,

said resonators having'capacitativaelements'nexti. the parts thereoftowardi'sa-id cathode Icavity, a1:

main cathode insaid cathode cavity, and anauxiliary ring-shapedi cathode one of" said' end ends or the resonatorsbeing. otherwis'eopenzto said end spaces, and said auxiliary cathode have ing aplurality of. equally spaced electronemis'e .sive patches equal in number tothelnumben'oii; cavity resonators in said series, saidlpatches each:

directly overlying. a pair; of said capacitative;'elements;

4. A magnetron having-an anode providing-4a; cathode cavity, and, a. circular sejriesiof ;eyenlylspaced cavity resonators; each-10f said resonators asoaua REFERENCES CITED The following references are of record in the me of this patent:

UNITED STATES PA'I'ENTS Number Name Date 2,411,953 Brown Dec. 3, 1946 2,413,385 Schmidt Dec. 31, 1946 2,438,194 Steele, Jr., et a1. Mar. 23, 1948 2,446,531 Derby Aug. 10, 1948 2,468,243 Spencer Apr. 26, 1949 OTHER REFERENCES Frequency Modulation and Control by Electron Beams, 8, paper presented on March 4, 1947,

at the I. R. E. National Convention and later found on pages 644-657 of Proceedings of the I. R. E. for July 1947.

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