US2502530A - Electron discharge device for ultra high frequencies - Google Patents

Description

2,502,530 ELECTRONDISCHARGE DEVICE FOR April 4, 1950 J A. MoRToN ET A1.

' Y ULTRA HIGH FREQUENCIES Filed Jan. 13, 1945 2 Sheets-Sheet l pJ. AMoRro/v Nm/Tiff' RL. 144A/CE v ATTORNEY April 4, 1950 J. A. MoRToN s-:T Al. 2,502,530

ELECTRON DISCHARGE DEVICE FOR ULTRA HIGH FREQUENCIES Filed Jan. 13, 1945 2 Sheets-Sheet 2 F/G. 2 F/G. 3

j w l van? J A. MORTO/v mlm/2059 R. L. VANCE A TTORNEV Patented pr. 4, 1950 ascesi UNITED STATES PATENT OFFICE ELECTRON DISCHARGE DEVICE FOR. ULTRA HIGH FREQUENCIES Application January 13, 1945, Serial No. 572,596

18 Claims.

This invention relates to electron discharge devices for ultra-high frequencies and more particularly to such devices including one or more grid electrodes between a cathode and an anode and especially suitable for operation at ultra-high frequencies, for example frequencies of the order of 3000 megacycles.

The performance of devices of the type noted above is dependent upon both the parameters of the elements deiining the interelectrode regions and those of the coupling or transducer system between the interelectrode regions and the external circuit associated with the device. More particularly, the operating characteristics, such as gain, band width and signal-to-noise ratio and the upper limit of the operating frequency range are dependent largely upon the magnitude 'and uniformity of the cathode to grid and grid to anode spacings, the fineness and regularity of the grid, and the magnitude of the variations, due to temperature effects, in the electrode relationships during the operation of the device. Desiderata for the interelectrode regions from the standpoint of high gain, wide band width and large signal to noise ratio and a high limit for the frequency range over which these obtain, are small, accurate and uniform electrode spacings and the close maintenance of such spacings during operation of the device.

The coupling or transducer system between the interelectrode regions and the terminals of the device, that is, the external portions of the cathode, grid and anode leading in conductors to which the external circuits are connected, is of import from the standpoint of performance of the device in that it largely determines the conditions at these terminals for any particular conditions at the electrode regions. That is to say, it determines, in effect, to what extent the desirable electronic conditions at the electrode regions within the device are or may be available or utilizable at the terminals. This coupling or transducer system, therefore, should be such that the losses therein and effect upon band width thereof are small and, further, that good impedance transformation between the electrode regions and the external terminals is provided.

One general object of this invention is to cbtain improved operating characteristics for electron discharge devices and particularly for ultrahigh frequency devices of the type having a control grid interposed between a cathode and an anode.

More specifically, objects of this invention are to:

Realize high gain, wide band width and large.

signal-to-noise ratio in ultra-high frequency electron discharge devices;

Attain extremely small, highly accurate and specifically between the cathode and grid and grid and anode, in such devices;

Minimize the effects of temperature upon these SPaCIlgS;

Facilitate the fabrication of electron discharge devices having closely spaced electrodes;

Enable substantially full utilization at the external terminals of an electron discharge device, of the desirable electronic characteristics at the interelectrode regions of the device; and

Minimize losses in and reactive transducer eiiects of a coupling system between the electron stream of an electron discharge device and an external circuit associated with the device.

In one illustrative embodiment of this invention, an electron discharge device comprises a cathode, control electrode or grid and anode, the effective surfaces of which are planar and parallel and of comparable over-all dimensions.

In accordance with one broad feature of this invention, the electrodes are constructed and arranged so that electronic conditions highly conducive to high gain, substantial band width and large signal-to-noise ratio are obtained at the interelectrode regions and the elements of the coupling or transducer system for associating the electrodes with external circuits are correlated to affect transformation without substantial degradation of the conditions mentioned to the external terminals of the device.

More speciically, in accordance with one feature of this invention, the effective electrode surfaces are constructed and mounted to provide extremely small and uniform spacings thereof which are maintained with high accuracy during the operation of the device, and the coupling system is constructed to provide a smooth geometrical and electrical transition from the electrode regions to the external circuit. In one particular construction, this system is constructed to define a double coaxial line terminating at one end in the electrode surfaces and characterized by low loss and parasitic capacitances, minimum reactive transducing eects and a very high surge impedance of the grid-anode region.

In accordance with another feature of vthis invention, the cathode or anode, or both, is mounted on a support member having a seating surface accurately coplanar with a face of the 55 respective electrode, whereby each surface may f very uniform spacings between the electrodes,-

be utilized as a reference for determining the spacing between a pair of electrodes. In a specific and illustrative construction, the support member is of a material, such as a low loss ceramic, having a low temperature coecient, the electrode, i. e., anode or cathode, is fixed upon the support as by molding therein, and the electrode face and one face of the support member are lapped simultaneously to make them accurately coplanar, for example within the order of 0.2 of a mil.

In accordance with another feature of this invention, the grid assembly comprises a frame of prescribed thickness to one'face of which a planar grid, formed of extremely ne wires, is aixed, and the aforenoted surface of the anode sup-port is seated upon the other face of the frame whereby the thickness of the frame determines the spacing between the anode and the grid.

In accordance with a further feature of this invention, the grid frame is seated upon a spacci' resting upon the lapped face of the cathode support, the spacer being of a thickness to provide the desired spacing between the grid and a fiat thermionic coating upon the lapped face of the cathode.

In accordance with still another feature of this invention, theA electrodes, the supports therefor and the spacer aforenoted are fabricated as a unitary assembly wherein the elements are in stacked relation and are locked together by rivets of a material, such as a low loss ceramic, having a low temperature coeii'icient.

In accordance with a still4 further feature of this invention, the unitary assembly above mentioned is provided with a cylindrical metallic member having a glaze or coating upon its outer face and. adapted to rit slidablyv/ithin a metallic cylindrical wall portion of the enclosing vessel of the device, the cylindrical member being connected electrically to the cathode and together with the glaze or coating and the cylindrical wall portion dening a by-pass condenser.

The invention and the above noted and other features thereof will be understood more clearly and fully from the following detailed description with reference to the accompanying drawing in which:

Fig. 1, is an elevational View mainly in section of an electron dischargey device illustrative of one embodiment of this invention;

Fig. 2 is a perspective view showing details of the cathode assembly included in the device shown in Fig. l;

Fig. 3 is a perspective View illustrating the grid electrode construction and one method of fabricating this construction;

Fig. 4 is another perspective View showing the construction of the cathode to grid spacer member;

Fig. 5 is a detail View in perspective illustrating the retainer ring and associated resilient member forming a part of the electrode. assembly in the device shown in Fig. l;

Fig. 6 is an enlarged, fragmentary sectional view showing details of the by-pass condenser included in the device illustrated in Fig. l; and

Fig. 7 is a detail view in section of a modification of the anode assembly. v

Referring now to the drawing, the electron discharge device illustrated in Fig. l comprises a highlyV evacuated enclosing vessel including a base l0 through which there extend' a plurality of leading-in conductors Il which are sealed units.

hermetically to the base by vitreous beads l. The vessel comprises also a flanged, metallic cylindrical portion I3, the flange on which is sealed to the base ill, as by welding or brazing, and the other end of which isy closed in part by a dielectric, such as a glass or ceramic disc lil hermetically sealed to the cylindrical portion i3 along the adjoining surfaces as at l5, by metallic or vitreous bonding material.

Mounted Within theA enclosing vessel is a unitary electrode assembly comprising a flanged, cylindrical metallic member i6 having an annular, concentrically corrugated, metallic diaphragm Il aiiixed thereto, the diaphragm advantageouslybeing of. a material, such as Invaig having a very small thermal expansion and conduction coefficient. The cylindrical member V3 has thereon a thin glaze or coating lil of a ceramic, and the coating has thereon a thin metal-lic coating i9., for example of silver. The outer diameter of the coating I9 is such as to fit closely against the inner wall of the cylindrical portion i3 of the enclosing vessel. The cylindrical member lli, coating i8 and portion I3 constitute a cylindrical condenser the function of which will be pointed outhereinafter.

Seated against the diaphragm il is an insulating disc 20, advantageously of a ceramic, which mounts a cathode assembly comprising, as shown clearly in Fig. 2, a metallic disc 2i, for example of platinum,A a stem `2,.for example of molybdenum, suitably securedV to the disc 2 l, and having an enlarged head portion 23, and a disc Zt, for example of nickel, Welded to the head portion 23.. In the fabrication of the cathode assembly, the disc 2l is molded in the disc 20, the surfaces 25 and 25 of the insulating and cathode discs 20 and 2d respectively are lapped simultaneously by a suitable abrasive, for example silicon carbide,

to be essentially coplanar, for example within .00.02 inch, and a thermionic material subsequently is applied to the lapped surface 2E to form a coating of prescribed and uniform thickness, e. g. of the order of 1/2 to l mil.

The cathode assembly includes also a cylindrical metallic heat shield assembly 27 which is joined to the disc 2l and to a cylindrical, metallic member 28 depending from the diaphragm i?. The cathode stem'22" is closely encompassed by a helical. heater filament 29, such as a tungsten wire coated with an insulating material, the ends of the heater filament being joined to conductors 3.0' in turn joined to certain of the leading-in conductors Il. The conductors 30 mount a metallic heat reecting shield 3l, which is provided with oversize apertures through which these conductors extend and is mounted from the base l0 by a support 32.

Opposite the coated cathode surface 25. and parallel` thereto is a grid 330i substantially parall'el coplanar wires which are affixed to a frame 34, e. g. of molybdenum, and extend across a central.` circular aperture 35 therein. As illustrated inFig. 3, the grid 33 is fabricated by winding a fine wire, for example of .00033 inch tungsten, l00'0 turns per inch, upon a pair of frames 34, for example ofthe order of 5 to 10 mils thick, separated by a suitable spacer 36. The grid wires after winding are amxed to the frames, as by gold brazing in an atmosphere of hydrogen, along the edges 31 of the frames and are severed adjacent these edges to form two grid-frame During the winding of the grid, they wire is maintained under a constant tension to facilitate the realization of uniformity of pitch and of conditions for securing the wires during the brazing operation. After the brazing, arcuatel tained. In the completed unit, the grid wiresA are continuously under tension and the desired parallel coplanar relation thereof is maintained despite the temperature variations in the wires during operation of the device in which the grid is included.

- The frame 34 is seated upon an annular metal- K- lic spacer 38v with the aperture 35 in coaxial alignment with the cathode disc 24 and with the face of the frame on which the grid wires lie.-

toward the cathode disc 24, whereby the cathode to grid spacing is determined by the difference between the thickness of the spacer 38 `and the height of the thermionic coating above the lapped surface of the cathode support 23. The spacer 36 is provided with an annular corrugation in which a channeled metallic ring 39 is secured, as by a ring 4I) of solder or brazing material, the inner surface of the ring 39 being tinned for a purpose which will appear presently. The spacer 38 is provided also vwith a plurality of depending sockets 4I which extend into apertures 42 in the ceramic disc 26, only one of which apertures is shown in the drawing. ,These sockets function to prevent the leakage of high-frequency energythrough the holes in the grid frame from the output region to the input region.

Seated upon the grid frame 34 is a cup-shaped anode support 43 of an insulating, e. g. ceramic, material in which the anode 44, e. g. of stainless steel or copper is fixedly mounted. The lower surface of the anode, in Fig. 1, and the rim face of the support 43 are lapped simultaneously by a suitable abrasive, such as silicon carbide, to be essentially coplanar, whereby, as will be apparent, the anode to grid spacing is determined by the thickness of the grid frame 34. provided with an extension 45 which fits into a recess in the split inner end of a leading-in con-l ductor 46 internally tinned as indicated at 52. The conductor 46 is sealed to an insulating, e. g. ceramic or glass member 41, along the adjoining surfaces at 48, and the member 41 in turn is sealed along the adjoiningsurfaces at 49, toa cylindrical leading-in conductor` coaxial with the conductor. 46 and sealed to the glass or ceramic disc I4 along the adjoining surfaces at 5I.

The cathode, anode and grid are constructed as a unitary assembly, including also an insulating, e. g. ceramic, body 53, wherein the parts are clamped together in stacked, coaxial relation by a plurality, for example three, of ceramic posts 54 having vitreous beads 55 fused to the ends thereof and extending through the several parts. The beads 55 at one end of the assembly are seated upon the anode support 43; thebeads 55 at the other end of the assembly are fused into sockets 56 upon a metallic retaining ring 51,- shown clearly in Fig. 5, which bears against a dished metallic spring 58 bearing in turn against the body 53.

In the manufacture of the device, the cylinder I3, the conductors 46 and 5I! and the glass or ceramic discs I4 and 41 are fabricated as a unitary assembly. The unitary electrode assembly described hereinabove and including the cylinder I6 and coatings I8 and I9 thereon is inserted into .the cylinder I-3fso .that the conductor 50. is

The anode is the performance of the device.

seated in the channeled ring 39 and the anode extension extends into the conductor 46. By-

. between two of the leading-in conductors I I may be provided and flashed during the evacuation treatment of the device. To enable outgassing of inner parts of the electrode assembly, radially extending grooves 10, 14 and I5 are provided in the cathode support 20, the anode support 43, and the base insulator 53 respectively, and aper tures 'II and 'I2 are provided in the disc 2I and anode support 43, respectively. Apertures 13 may be provided also in the grid conductor 50.

Electrically, the anode and grid constitute parallel plane electrode faces at the ends of the coaxial line constituted by the conductors 46 and 5I). rlhe effective cathode surface is parallel to the anode and grid and is connected conductively to the cylinder I6 in turn connected to one of the leading-in conductors II by a tie wire 6I. For alternating currents, the cathode is connected to the cylinder I3, which is coaxial with the conductorsrllii and 5I), by the condenser defined by the cylinders I3 and I6 and dielectric coating I8. Thus, coaxial input and output systems terminating in parallel plane electrode surfaces are provided.

Because of the construction and association of the electrodes as described heretofore, it will be appreciated that extremely accurate parallel plane relationship of the effective electrode sur faces is attained and that this relationship is maintained during the operation of the device.

. Further, extremely small electrode spacings, for

example of the order of 1/2 to 1 mil between cathode and grid and of the order of 5 to 10 vmils between grid and anode, are achieved where by electron transit times are minimized and high transconductance'and good signal-to-noise ratio and band width are obtained.

As has been pointed out heretofore, the coupling between the electron stream and the external circuit is of major importance in determining In the device disclosed, the parameters 0f the elements con stituting this coupling are correlated t0 produce optimum performance over the operating range, specifically at frequencies in the microwave region. It will be noted that because of the coaxial relation of the cylinder I3 and conductors 46' and 50, the parallel plane relation of the electrode surfaces and the form and relation of the connections between the electrodes and the conductors, a geometrically and electrically smooth transition between the interelectrode spaces and an external double coaxial line coupled to the coaxial conductors I3, 46 and 5I) is obtained. Further, inasmuch as the diameter of the conductor 46 associated with the anode is small in comparison to that of the conductor associated with the grid, the surge impedance of the gridanode region is very high. Also, because of the form vand substantially equal diameters of the electrodes and the mounting thereof, parasitic.,

axe-negano.;

in the device shown.` in Eig; lv is. illustrated in. Eig. '7. and'comprises. asupport 62 of ceramiciin.

which a disc 63. is embedded; asv byzmoulding.v The disc mounts a stem lid-to. which antanode.- discs65, for eXample-ofzirconium is .aixed The surfacesz andxl of the;anode. disc 651and supporti.' 62.; respectively,.are lapped to make. them accurately coplanar.

Although a specicembndiment yof theinvention. hasbeen shown and described, itWill bev understood that. it. is butv illustrative. and. that.

various .modifications-may be made therein .without departing from the scope.. and. spirit of. this invention as definedin the appended claims.

What is claimed is: 1. An electron. dischargezdevice comprisingza first support member having a planeseating-surfa'ce,.a cathode mounted by saidsupportmember and having a face coplanar with said surface, ia'.

second support. member having a plane seating surface, an anode. mounted by saidsecond support member and having a face coplanar with saidseating surface thereof,.a plane grid, meansy spacing said cathode face, anode faceand'gridl in aligned parallel relation `comprising spacer meansibetween .said grid andthezseating surfaces.

of said rst and second support members. and means separate from said first and second support members: locking said support members against said spacer means.`

2. An electron discharge device in accordance with claim l wherein said spacer-'means comprises a plane frame mounting said. ,grid andi.

seated against said seating surface of saidy sec.- ond support member.

3. An electron discharge deviceY inaccordance. with claim l comprising :a planeframe mounting. said grid and wherein saidspacer means, com'- prises a plane spacer member between. andv en.- gaged by one face of said frame and said seating, surface of saidrstsupport member.

4..An electron discharge device .comprising a. plane frame, a grid extending acrossy one-faces of said frame and substantially coplanar'therewith, a cathode assemblyI comprising. a. disc having a plane seating surface yand a cathode-member mounted by said1diso-and having aface coplanar with said .surface and ,opposite saidgrid, electron emissive material on said face'of said: cathode member, a plane disc between saidz-face` of said frame andsaid seatingssurface and de-` termining the spacing therebetween, andanzan.- odeA opposite said grid.

5. An electron discharge device comprising-a. rst electrode assembly including a member having. a plane seating surface and an electrode. mounted by. said member and substantially co.- planar with said surface, a second: electrode as sembly comprising a. second. member having af plane seating surface. and any electrode-mounted. by said second member. and havingwa. facebo-` planar with said seating surface thereon. said electrodes being in juxtapositiomplanan spacen means between said seating surfaces; and-means-` clamping said first and. second:members.V against opposite faces of said spacer means.

6. An electron discharge devicercomprisingan.

Ul i

insulating disc. having: a planev seating. surface, 75

ane. electrode member, embedded inv saidydisc and havingone face coplanar with said'seating. surface, a support having; a plane seatingsurface, an electrode mounted'by said support andsub- 1 stantially coplanar with said seating surfaceV thereof, said.- electrode and-electrodermember be ing in. juxtaposedl relation, and planar spacer means between said seating surfaces.

y'7; vAn electron discharge device comprising a firstinsulating disc having a plane seatingY surface, a cathode member mounted by said disc and having. a. face-coplanar with said seating surface, a plane spacer member seatedonv said surface, av planev frame. member seated on said spacer. member, a grid mounted by said frame and substantiallyfcoplanar: with. one face thereof;y asecond insulating dischaving a plane surfacelseatedl on said frame, `and anvanode mounted by-saidsecond disccand having-a plane face coplanar. with said` plane surface thereof, said cathode member, gridand anode being inalignment.

8. An electron discharge device comprising a.

unitary assembly including-a first insulating disc having a plane surface, a cathode mounted by said' disc and having a face substantially ccplanar with said surface', a plane frame seated onsaidv surface, a gridmounted by said frame, substantially coplanarwith one. face thereof and in alignment with said cathode, a second insulating disc havingraplane: surface seated on .said frame, an anode'l mounted by said Second disc and having a..face...coplanar with said sul'- face thereof andv in alignment with said grid,

f.' and means clamping said firstand. second discs and said frame together comprisingv rivets of ceramic material extending therethrough, a disc spring member interposedv between one end of said rivets .and the-insulating disc opposite said one end and a` retainer member. bearing against said spring member and locked to said one end ofsaid rivets.

9i A cathode assemblyfor electron discharge deviccscomprising a ceramic member having an aperture therein andhaving also a plane face, a metallic disc embedded insaid insulating membei' and extending.. across 4said aperture, ametallic stem extending through said'discl andxanxed thereto', a cathodel disc joined to onek end of said1 1 stem andihaving-a face coplanar with said plane face,- and a heater filament. encompassing said stem.

10. An electron discharge device comprising an' enclosing vessel havingA a cylindrical inner wall, a unitary electrode assembly within said vessel, and means separate from said vessel mounting saidassembly comprising a cylindrical member" coupled to said assembly and coaxial with and slidably fitted within said cylindrical wall;

1'1 An electron discharge device comprising an enclosing lvessel having a cylindrical, metallic inner' wall, a unitary electrode assembly within saidvessel including al pair of cooperative electrodes, andv means mounting said electrode assembly within said vessel' including a cylindrical metallic member connected' electrically to one of said electrodes and having a coating of dielectric material' upon the outer surface therecf," saidcoating being immediatelyadjacent said cylindricalA wall and' definingv a condenserV therewith and with said cylindrical member.

12;.An electron discharge device comprising anienclosingivesselrhaving.:a cylindrical, metallic inner wall, a; unita-ry; electrode assembly within trodes, a cylindrical layer of dielectric material upon vthe outer surface of said cylindrical member, and a cylindrical coating of electrically conductive material upon said layer of dielectric pin connected to one of said electrodes and iittedin said recess, and a conductive member connected to the other of lsaid electrodes and having an annular portion engaging the inner end of said cylindrical leading-in conductor.

14. An electron discharge device comprising an evacuated enclosing vessel, a pair of coaxial leading-in conductors extending through one endl of said vessel and sealed hermetically thereto, a unitary electrode assembly within said vessel including a cathode, grid and anode, electrical extensions of said grid and anode forming a part of said assembly and each engaging a respective one of said coaxial leading-in conductors, and means separate from said conductors mounting said assembly within said vessel.

15. An electron discharge device in accordance with claim 14 wherein said mounting means comprises a metallic member connected electrically to said cathode, a dielectric coating on the outer surface of said metallic member and an electrically conductive coating on the outer surface of said dielectric coating and adjoining an inner wall of said enclosing vessel.

16. An electron discharge device comprising an enclosing vessel having a cylindrical metallic portion, insulating means extending across one end of. said portion, a leading-in conductor coaxial with said portion and extending through said insulating means, said conductor having a recess in the inner end thereof, a cylindrical leading-in conductor coaxial with said first conductor and extending through said insulating means, a unitary assembly within said vessel and including a cathode and a pair of electrodes in cooperative relation therewith, an electricalextension of one of said electrodes iitted in said recess, an annular, channeled metallic member electrically integral with the other of said electrodes, the inner end of said cylindrical con--r ductor iitting within said channeled member, va

cylindrical metallic member coaxial and adjacent said cylindrical portion and connected electrically to said cathode, and a dielectric material between said cylindrical metallic member and said cylindrical portion.

17. An electron discharge device comprising a cathode having a plane emissive surface, an anode having a plane surface parallel to and in align- `ment with said emissive surface, a plane control electrode between, parallel to and in alignment with said anode and cathode surfaces, an enclosing vessel having a cylindrical conductive portion encompassing said cathode, anode and control electrode and axially aligned therewith, means including a substantially plane metallic member extending parallel to said emissive surface, electrically coupling said anode tosaid cylindrical portion, a cylindrical conductor extending within said portion and coaxial therewith, means including a substantially plane conductive member parallel to said plane metallic member coupling said control electrode to said cylindrical conductor, and a cylindrical conductorco-nnected to said anode and coaxial with said cylindrical portion.

18. An electron discharge device comprising an enclosing vessel having fa cylindrical conductive portion, dielectric disc meansk extending transversely of said portion and sealed thereto, a cylindrical 'rod coaxial with said portion ex tending through said disc means and sealed thereto, a cylindrical conductor coaxial with and encompassing said rod, extending through said disc means and sealed thereto, an anode joined to the inner end of said rod and having its eiective surface plane and substantially normal to the axis of said rod, a cathode having a plane, emissive face opposite and parallel to said surface of said anode, means including a metallic disc coupling said cathode to said cylindrical portion, a substantially plane grid in cooperative relation with said cathode and anode and parallel to said emissive face, and means including a metallic disc parallel to said first disc connecting said grid to said cylindrical conductor.

JACK A. MORTON. ROBERT L. VAN CE.

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

l UNITED STATES PATENTS Number Name Date 2,128,236 Dallenbach Aug.30, 1938 2,270,638 Llewellyn Jan. 20, 1942 2,289,846 Litton July 14, 1942 2,353,742 McArthur July 18, 1944 2,402,601 Chevigny et al June 25, 1946 2,407,974 Clifford et al Sept.` 24, 1946 2,408,927 Gurewitsch Oct. 8, 1946 2,414,785 Harrison et al. Jan. 21, 1947

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