US2508346A - Ultra high frequency electron discharge device - Google Patents

Description

May 16, 1950 J. M. LAFFERTY ULTRA HIGH FREQUENCY ELECTRON DISCHARGE DEVICE Filed June 22, 1945 2 Sheets-Sheet 1 Fig.1.

Fig 3.

Inventor:

UJ. t r W H r m pl m LEE M M 5 b mM y 1950 J. M. LAFFERTY 2,508,346

ULTRA HIGH FREQUENCY ELECTRON DISCHARGE DEVICE Filed June 22, 1945 2 Sheets-Sheet 2 Inventor: James M .lvaFFePty,

H is Attor-n ey.

Patented May 16, 1950 ULTRA; HIGHEREQUENGX ELECTRON-.- DISCHAB DEV C James M; Lafierty; Schenectady, Ni Y2, assigno'r to General'Electric- Company, a corporation of- New York Application June 22, 1945 Serial No; 600,908

8 Glaims; 1

My invention relates to ultra high frequency electron discharge devices and-more particularly, to'ultra high frequency electron discharge devices-oi the space resonant type employing-velocity modulation principles.

Inmy copending'application; Serial No; 506;-

50l., .filed October 16, 1943; entitled" Ultra high frequency electric discharge device, which is nowpatent 2-,454-,97Q;,granted November-30'; 1948'; and assignedto the; sameassignee as the present,inventi'on; It disclosed an ultra high frequency oscillator of the reflex velocity modulation type in which a; cavity resonator is provided; The operating frequency of the. device is; controlled either by mechanical means which adjusts" the positionofa tuning diaphragm, or; electrically by controlling the potentials of a repelling electrode with respect to an anode structure. 7 My present invention is directed to certain improvements in an ultra high frequencyelectron discharge device, of this type.

' It isan object of my invention toprovide a new and improved ultra high frequency electron discharge device having a waveguide output system formedintegral with the device.

' It is another obiect' of my invention to provide anew and" improved cavity resonator in which a section of wave guide is formed integral with the-resonator and coupled therewith.

It is stillanother object" of my invention to provide a new'and improved ultra high frequency electronic tube in which the internal tubestructure is completely fabricated and then slipped into an envelope which contains an output wave uide.

It is a further object of my'invention to provide a new and" improved cavityresonator having a' wave guide output in which impedance matching between the resonator and the wave guide is effected.

In accordance with one aspect of my invention. I provide a newand improved electron discharge device employing velocity modulation principles and including a metallic enclosing envelope having a window therein which is p ervious to electromagnetic waves and which forms one end of an external wave guide section. The electron discharge device employs a cavity resonator to which islconnected' within the tube structure a section. of wave guide supported adjacent the window in the envelope.

Another feature of my invention relates to the improved cavity resonator structure having a wave guide output formed integral therewith and in which means are provided for matching the high shun-t impedance of" theresonator ta the relativelylcw impedance of thewaveguide section.

For" a' better understanding of my invention, reference-maybe hadto the followingdescription takeninconnectionwiththeaccompanyingidraw ing and* its scope Willbe pointed out in the appended claims; Fig. 1 is a longitudinal view, partiyin crosssection; of anelectron discharge evice of the velocity modulation type built in accordance-with myinvention. Figs. 2-and- 3 a-re detailedcross-sectional-views otthis discharge de-- vice: Rig; 4 represents: an" enlargement of certain partsjof Fig; 1-; while Fig. 5 represents a perspective viewof one part'of Fig. 1*.

Referring to Fig; 1-, my invention is there illustrated as applied to an ultra highfrequencyelectron discharge device comprising an enclosing en'velope I, preferably of rigid: construction, comprising a metal having alow coefficient or thermal expansion such as-Invar; andwhich ole-- finesa-t least inpart anevacu-ated space in which are positioned various elements and electrodes;

described hereinafter; The envelope 1* is supported byand sealed'to a base member 2' which comprises a flanged" metallic part to whichthe; tower part-of the" envelope l-- is-securedby-asuitable sealing means, suchas bya solder 3. A plurality of seals andlead-in prongs or terrniiial' posts 2-9, inclusive, aresupported by-aninsulating; part it of base-mem-ber 2- in insulated relation" and serveasexternally accessible contacts for the electrodes in the electron dischargedevice; Of the aforementioned siglead-inseals; and terminal posts, four are visible in- Fig; 1 below the insulating part N5; while two, to-wit, parts 8; 9; areseen inthe sectional view off the in teriorstructure of the electronic tube: orientationprotuberance; f;orguiding the in sertionof' base member '2 and the-terminal: posts into anassociated? socket is provided and may comprise the externally located tubular extension H" of insulating material formed integral witl'i; part it],

Within the envelope I and preferably centrally locatednearthe lower partof the defined space, I provide a; thermionic cathodewhich be ofthe indirectly heated type comprising a metallic cylinder i2, preferably coated on the exterior" of the upper closed end with anelectron emissive material, I such as: an alkaline earth metal, to serve as a;source;of*e1ectrons, Afii'ament or heating element I8 is centrally posttionedwithin the cylinder l2} and; is; supplied with; energizing current through a, pair of conductors;

l4, l5, conductor l4 being connected between one end of filament l3 and terminal post 8 and conductor l5 being connected to the terminal post 9. Conductor I5 is likewise connected to the outer surface of metallic cylinder [2 at its lower extremity.

To focus the electrons emitted at the upper end of the cathode cylinder l2, a focussing electrode is employed and may comprise a cylinder I6. The focussing cylinder 16 is supported within a metallic thimble member I! which engages a shoulder portion [8 on the focussing cylinder 25. The cathode cylinder [2 likewise is supported within the thimble I! by means of an insulating disk H! which abuts the shoulder portion H3. The cylinder I2 is secured to the insulating disk [9 by a pair of flanged metallic washers 29, 2| which engage opposite sides of the disk I9 and are integrally attached to the cylinder l2, as by welding, the disk l9 being retained within the thimble I! by means of a retaining ring 22. Focussing potentials are supplied to the electrode l6 by means of a conductor 23 which is connected to the lower end of the thimble I1 and to the terminal post I. A shield 23', which may be formed of a suitable metal and which is supported from ring 22, is provided to prevent any electronic bombardment of the seals 4-9 and their associated conductors by cathode [2. Shield 23' also prevents any material which may be evaporated from the cathode from being deposited on the seals 4-9.

The thimble I! containing focussing cylinder I6,

in turn, is supported from a dielectric disk 24. The thimble H is attached to the disk 24 by means of a plurality of metallic rings 26, 21 which are welded to the outer surface of thimble l1 and have flanged portions engaging the disk 24. A metallic ring 25 is supported by and thermally connected to a heat conducting member 28 formed of a, suitable metal having a low coefficient of thermal expansion, such as Invar, the ring 25 being secured thereto as by welding. The heat conducting member 28 may be corrugated, as shown, and have an outer diameter such that it slips within the envelope l making thermal contact therewith at each corrugation. At its lower end, the member 28 may rest upon the upper end of base 2 and be attached thereto in any suitable manner, not shown, such as by welding.

. An anode structure defining a cavity resonator is provided comprising a substantially cylindrical metallic block 29 which rests upon the ring 25 and may be mechanically secured thereto, as by soldering. The lower portion of the block 29 is provided with a centrally positioned recess 30 into which the thimble I! extends. An upper portion 29 of the anode structure is provided with a similar centrally positioned recess 3| on its upper surface and the cavity resonator of the device is positioned within this recess. After the resonator is so positioned, the two portions of the anode structure are soldered together to form an integral structure.

The cavity resonator 32 comprises a tubular metallic cylinder member 33 which passes through a centrally located aperture in the block 29, a conical member 34, and a flexible diaphragm 35. The conical part 34 is circular in form and has a flanged portion 36 which engages a, shoulder 31 on the inner surface of the tubular member 33. The conical part 34 likewise has a tapered aperture 38 through which the electron beam passes and which defines, with one boundary of the cavity resonator 32, a, velocity modulating gap 39 for the electrons constituting the beam. The flexible metallic diaphragm 35, which provides means to control the natural frequency by controlling the physical dimensions of the cavity resonator 32, is seated upon a circular flange 40 extending upwardly from the top surfaces of a flange 4| which forms the upper end of the cylinder 33. The diaphragm is provided with a central aperture 42 to afford a communicating path between the cavity resonator and the electrode reversing region described hereinafter. The radial distance from the wall of resonator 32 to the inner surface of the circular flange is made approximately equal to a half wave length at the desired operating frequency of the electron discharge device so that the diaphragm 35 and the top surface of flange 4| between the cavity resonator 32 and flange 49 define an annular portion and form a section of radial transmission line of a length such that the short-circuit at one end, constituted by the flange 40, is reproduced to appear as a very low impedance at the inner end of the section of radial transmission line. The diaphragm 35 and the upper surface of the cylinder 33 are provided with a plurality of corresponding concentric grooves 43, the function of which is pointed out in detail hereinafter.

Control means are provided for establishing electron repelling electric fields and may take the form of a cylindrical metallic member 44 which is supported by a dielectric cylinder 45 which rests upon the upper surface of the diaphragm 35. The dielectric cylinder 45, in turn, is secured within a retaining housing formed by a hollow vertical metallic cylinder 46 having a lateral opening 41. The cylinder 46 rests at its lower end in one of the grooves 43 on the upper surface of the diaphragm 35. At its upper end, the cylinder 46 contains a transverse member 48. So constructed the members 46, 48 form a yoke which surrounds the electrode 44 and which rests upon the upper surface of the diaphragm 35, preferably being soldered in one of the grooves 43.

Energizing potentials are supplied to the repelling electrode 44 by means of a transverse conductive strip 49, best seen in Fig. 2, which extends through lateral opening 4'! and one end of which is connected to the upper end of the electrode 44. The other end of strip 49 is connected to a vertical conductor 56 which passes through a longitudinal opening 5| in the block 29 to connect with the terminal post 4. Also shown in Fig. 2, is the gettering means 52 in the form of a fusible conductor, the ends of which are connected by means of conductors 53, 54 to terminal posts 5, 6. Near their points of connection to the gettering means 52, the conductors 53, 54 are curved and serve to support a trough 55 positioned between the gettering means 52 and the electrodes of the discharge device.

In order to derive ultra high frequency energy from cavity resonator 32, a section of a rectangular wave guide 56 is formed integral with the anode block 29 by milling a transverse rectangular slot in the block 29. The tubular cylinder 33, as seen in Fig. 3, constitutes an end wall of the section 56 of the wave guide. Electromagnetic waves are coupled between the cavity resonator 32 and wave guide 56 by means of a small slot 51, which is cut in the metallic cylinder 33 just below the flange 4|. The width of the slot 51. as best seen in Fig. 3, is such that a very small opening 58 is formed in the side wall of the cavity resonator 32. In this construction, the cylinder 33 forms a step at the end of the wave guide and the height of the slot 51 is so corre- 5 lated with the dimensions of this step that the high shunt impedance of the cavity resonator'32 is" matched with the relatively low impedance of the wave guide 56.

In order to effect the transfer of energy from the wave guide 56 to a utilization circuit external to the electronic tube, the envelope l is provided with a lateral opening 59 surrounded by an external tubular collar 65. Within the collar (it is disposed a metallic thirnble 6| which extends slightly through the opening 59 into the region within envelope l. At its end which projects through the opening 59, the thimble Si is provided with an aperture across which is sealed a vitreous Window 62, the window 62 being placed directly in rront of, the wave guide section 56. Ereferably, the window 62 is formed of a suitable glass whichispervious to electromagnetic waves, transmitting them dielectrlcally with a. minimum amount of reflection. In the construction of this window, the dielectric constant of the glass, its thickness and its surface dimensions determine its reflective properties. These parameters are so correlated that the window provides minimum reflection and optimum transmission at the desired. operating frequency. Adjacent the outer surface of the window 62 i an output section of rectangular Wave guide 53, the dimensions of which, correspond to the dimensions of the wave guide, section. 56.. The section 63 is formed in a metallic block 6d which. is supported from the collar. 60, by any suitable means, such as the Welds 65.

In order to obtain optimum transmission between the wave guides 56 and 63 through the Window 62, a pair of half-wave chokes 66, 6'? are provided. The choke 63 may be formed by a cir- .-cular groove cut in the anode block 29, the bottom. of the groove being displaced from the wave guide. section 55, in a manner well known to those skilled in the art, by a distance substantially equal to a half Wave length at the desired operatingfrequency of the electron discharge device. The choke 57, which is also in the form of a circular groove, is constructed by cutting shoulders 68, 69 on the block 54 and supporting a metallic sleeve. "ill on the shoulder 69. In the construction of this choke, shoulder 68. likewise is displaced from the edge of the wave guide section 63 by a distance equal to a half Wave length at the desired operating frequency of the electronic tube.

In order to permit coupling of an external wave guide to the wave guide section at, the block 54 is; provided with threads ii. A wave guide 72 which is to be connected with the wave guide 63 isprovided at its coupling end with a circular flange l3 through which pass positioning pins 14;. The pins E i are arranged to fit in holes 15 provided in the block The oriented Wave guide 'IZ is attached to the wave guide 63 by means fa nut'lfivvhich engages the threads ll.

An important feature of my invention, which includesv a wave guide output formed integral with a. cavity resonator and coupled with an external Wave guide, is that the internal tube structure. may be completely fabricated and then.

slipped into the envelope I, which is previously formed withthe transparent wave guide window and output wave guide in.position .To efiect such-a method of assembling the tube, the corrug atedeheat, conducting member 28 is provided with a longitudinal slot ll of such dimensions, that. it passes aro-undthe thimbleyli-I and assists in orient-- ing the internal tube structure in final assembly of" the device.

As a means for mechanically controlling the position of the diaphragm 35, an externally accessible actuating means is provided for exerting different amounts of pressure thereon, thereby controlling the dimensions of the cavity resonator 32. This means may comprise an assembly supported by the flat top of the envelope I and may include an actuating rod 18' constituting" avertically adjustable or positionable member or the actuating means. The rod 18 is connected to the transverse member 48. As previously described, the transverse member 48' is connected to the cylinder lfiwhich is soldered at its lower ends tothe diaphragm 35. Alternatively, the cylinder 45 may be seated in one of the annular grooves 4'3 and the diaphragm: may be formed tohave aresiliency tending to restore itself to: a vertical position whereupon the diaphragm is-maintainedin contact with the cylinder 46; In suchinstances, the control ofthe form and position of the diaphragm is accomplished by the amount of vertical pressure exerted thereagainst.

Surrounding the vertical rod 7-8 isa hollow tun ing screw [9 which is welded on brazed around the top of rod 18 to form a vacuum-tight seal, not shown, At its lower end,- the hollow tuning screw i9 is welded or soldered: to a metallic bel lowsv 8 3i sealed to the inner surface of envelope I to provide a sealing structure-0f deformable character in the upper portion of the envelope.

Above the envelope l' and in an externally ac-- cessible position, a micrometer adjusting: means i. isprovlded to actuate the'ro'd- 18 whereby, upon actuation, the rod 'Iilis moved to position=the diaphragm 35$ in minutely determinable degrees to. obtain a. desired control in the operatingsfre'e quency of the device. Preferably, the rod 18; the. transverse member 48, the supports 46, 41; tuning screw 79, and micrometer 8.]. are composed, similar to envelope l: and member. 28, ofa metalhaving alow coeilicient of thermal expan'- sion, Invar being well suited for this construe-- tion. So constructed; the. device experiences little change inxoperating. frequency as the: op-- crating temperature varies.

Fig; 2 is, a cross-sectionalviewof the device shown, in Fig. 1 along the 1ines'2-2' and represents-the disposition of the refiector electrodefli,

the fiat conductor 49,,and the getter 52, all with respect to the anode block 29. Fig. 3 is. a cross-- sectional View of the anode, block 29 of Fig; 1 takenalong the lines. 33 and. shows the; general circular 'form of the block 29 and. the location of the transverse; slot which; forms the wave guide: 56. This figure also shows the position of the cavity resonator 32 and the coupling aperture 58. with respect to the wave guide 56.

In. considering the. operation of the embodiment of my inventiondescribed above, it maybe stated generally that the-electron, discharge de-:

vice is of the velocity modulation typewherein;

the electron beam is velocity modulated periodically so that successive groups of electrons are, alternately accelerated and decelerated tending; to group the electrons in the beam after the: beam has traversed the velocity modulation ap: 39 in the resonator 32-. The particular form of electron discharge devicedescribed above operatesin accordance withrefleic principles. After:-

undergoing velocity modulations, the? electrons.

are given. an opportunity to assume: a charge: density distribution incident Y tothe. effect; of the1 7 velocity modulation and are reversed in theadlreca tion of travel to re-enter the cavity resonator delivering energy to the electromagnetic fields thereof and through the output aperture 58 to the wave guide section 56. In the device described above, an electron beam is established by virtue of the unidirectional potential impressed between the anode construction comprising the block 29 which is maintained at the potential of the envelope I and the cathode cylinder 12. The electrons of the beam initially assume a velocity determined by the differences in potential impressed between the anode and cathode. Negative potential is supplied likewise to the focussing cylinder I6 which tends to restrict the size of an electron beam, confining it to a relatively small area in order that a large percentage of the electrons pass through the cavity resonator 32 through the conical part 38. Assuming an excitation of the cavity resonator 32 by virtue of sporadic motion of electrons across the gap 39 during starting operation, the resonator is set into an oscillation and there is established across the modulating gap 35 between the upper edge of the conical part 38 and the diaphragm 35 an alternating high frequency potential incident to the electromagnetic field within the cavity resonator. By virtue of the alternating nature of this potential, electrons which are in the effective region of the gap 39 during periods of time when the diaphragm 35 is positive with respect to the conical part 38 are undergoing an acceleration. Consequently, the electrons, after traversing the gap 39, pass through the aperture 42 and proceed into the region of the field produced by the reflecting electrode 44 which, preferably, is maintained at a negative potential with respect to the cathode. The distance which the electrons proceed in their paths beyond the diaphragm 35 is a function of the kinetic energy of each electron. It is well understood that the energy of an electron may be referred to a voltage which will accelerate the electron to a particular velocity, establishing that amount of kinetic energy. The faster electrons obviously travel further toward the reflecting electrode before they are stopped and reversed than do the slower electrons.

The operating frequency of the system may be controlled either by controlling the physical dimensions of the cavity resonator 32 by means of the micrometer adjusting means 8i, or by controlling the voltage impressed upon the various electrodes including the voltage of the cathode cylinder [2 with respect to the anode and the voltage of the reflecting electrode 44. Considering first the control of the operating frequency by virtue of change in the natural resonance frequency of the cavity resonator, the position of the diaphragm 35 controls one boundary of the resonator and, consequently, controls its natural frequency. Ready adjustment of the position of this boundary is obtained by movement of the rod 18.

The operating frequency, as stated above, may also be controlled by variation of the voltages impressed upon the reflecting or repelling electrode 44, in this manner controlling the transit time of the electrons in the beam and consequently controlling the phase of charge density modulated electrons which are returned to the cavity resonator with respect to the field thereof. By using this method of controlling the operating frequency, it has been found that a final adjustment of the range of frequency may be obtained.

One of the features of my invention is the particular configuration of the reflecting electrode 44. As may be seen by reference to Fig. 1, this electrode is in the form of a hollow cylinder having its open end adjacent the aperture 42 in the diaphragm 35. The configuration of the electrode, moreover, is such that it provides both optimum transit time and optimum focussing of electrons so that they return through aperture 42 and in proper phase relation with the electromagnetic fields of the resonator.

It has been found in the operation of frequency devices of the type disclosed that excellent transmission of energy is obtained from the cavity resonator 32 to an external wave guide by virtue of the construction in which all coupling between the resonator and a wave guide is effected within the tube itself, and that transmission of energy between the wave guide sections 56, B3 is eiTected with substantially little reflection of electromagnetic waves. This result is attributable in large part to the construction of the wave guides and the window in which chokes are provided and formed integral with the anode block and output guide 63.

While I have shown particular embodiments of my invention, it will of course be understood that I do not wish to be limited thereto, since various modifications may be made, and I contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An electrode structure for an ultra high frequency electron discharge device of the cavity resonator type comprising a metallic block having a central aperture therein, a hollow metallic member supported in said aperture defining a portion of a cavity resonator, said member comprising an entrance part for receiving electrons and producing a narrowly defined control region within said resonator, a deformable diaphragm positioned opposite said entrance part and having an aperture therein, said block having a transverse slot defining a wave guide, said metallic member extending across said slot and forming an end wall for said wave guide, said metallic member having a transverse slot whereby energy from said resonator is coupled into said wave guide.

2. An ultra high frequency electron discharge device comprising an enclosing metallic envelope, a cavity resonator positioned within said envelope, means within said envelope for exciting said resonator, a section of wave guide of the hollow pipe type supported within said envelope, means coupling said resonator and said section, said envelope having a dielectric window formed continuously therewith and positioned opposite one end of said wave guide, means supported by said envelope defining a second section of wave guide external to said device, said sections of wave guide being aligned with each other and said window being disposed between said sections, whereby electromagnetic waves from said resonator are transmitted between said sections of wave guide through said window, and choke means surrounding said sections adjacent said window to facilitate transmission of electromagnetic waves through said sections.

3. A device as in claim 2 wherein said. choke means comprises annular grooves within each of said sections.

4. An electron discharge device of the velocity.

than said cavity spaced from said metallic means and defining therewith a cavity resonator including said cavity and an annular portion between said metallic means and said diaphragm, said metallic means and said diaphragm having aligned apertures through which an electron beam may be, projected to excite said resonator.

5. A device as in claim 4 wherein the radial dimension of said annular portion between said means and said diaphragm is substantially equal to one-half of the wave length at a predetermined operating frequency of said device.

6. An electron discharge device of the velocity modulation type comprising an envelope, a plurality of co-operating electrodes within said envelope including a resonant electrode structure comprising a metallic block having a central opening therein, metallic means supported within said opening having walls defining a generally annular cavity of diameter substantially less than the transverse dimension of said opening, and a circular flexible diaphragm of diameter greater than said cavity spaced from said metallic means and defining therewith a cavity resonator including said cavity and an annular portion between said metallic means and said diaphragm, said metallic means and said diaphragm having alinged apertures through which an electron beam may be projected to excite said resonator, said block having a second opening defining a metallic wave guide, said metallic means forming an end wall for said wave guide and including means intercoupling said cavity resonator and said wave guide whereby energy from said resonator may be coupled into said wave guide, said envelope including a window pervious to electromagnetic waves at one end of said wave guide.

7. ,A device as in claim 6 including means defining a wave guide external to said envelope coupled to said first mentioned wave guide through said window.

8. An electron discharge device of the velocity modulation type comprising an envelope, a plurality of co-operating electrodes within said en- Velope including a resonant electrode structure comprising a metallic block having a central opening therein, metallic means supported Within said opening having walls defining a generally annular cavity of diameter substantially less than the transverse dimension of said opening, a circular flexible diaphragm of diameter greater than said cavity spaced from said metallic means and defining therewith a cavity resonator including said cavity and an annular portion between said metallic means and said diaphragm, said metallic means and said diaphragm having aligned apertures through which an electron beam may be projected to excite said resonator, said block having a second opening defining a metallic wave guide, said metallic means forming an end wall for said wave guide and including means inter-coupling said cavity resonator and said wave guide whereby energy from said resonator may be coupled into said wave guide, said envelope including a window pervious to electromagnetic waves at one end of said wave guide, and means defining a wave guide external to said envelope coupled to said first mentioned wave guide through said window, said block and said last-mentioned means each including grooves defining chokes surrounding said wave guides and positioned adjacent said window.

JAMES M. LAFFERTY.

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

UNITED STATES PATENTS Number Name Date 2,200,023 Dallenbach May 7, 1940 2,287,845 Varian et al June 30. 1942 2,372,193 Fisk Mar. 27, 1945 2,408,437 McRae Oct. 1, 19-16

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