US2607905A - Microwave generator - Google Patents

Description

Aug. 19, 1952 F. LUDI 2,607,905

MICROWAVE GENERATOR Filed July 7, 1948 2 SHEETSSHEET 1 Aug. 19, 1952 F. LUDI MICROWAVE GENERATOR Filed July 7, 1948 2 SHEETS-SHEET 2 Patented Aug. 19, 1952 MICROWAVE GENERATOR.

Fritz. Liidi, Zurich; Switzerland, assignor to Patelhold Patentverwertungs- Holding A.-G., Glarus, Switzerland & Elektro- 1 Application 11. w, 1948, Serial No. 37,448 In Switzerland August 16, 1947 This invention relates generally to devices for generating ultra-high frequency electrical oscillations, i. e. in the centimeter range, and more particularly to those of the typein which electrons emitted radially from an elongated cathode transfer energy to an annular hollow resonae tor arranged concentric about the axis of the cathode; The resonator has annular end walls bounded in a, radial direction by outer and inner cylindrical walls, and the inner wallis .constituted by a cylindrical array of spaced anode segments, adjacent segmentsin the array. being secured to opposite end Walls suchthat alter nating, potentials are developed between adjacently positioned segments as the. resonator oscillates. Through the combined actions of a constant radialelectric field established between the cathode and the array of anode segments byan applied potential and a unidirectional magnetic field established axially, the electrons-leaving the cathode are-caused to. travel in cycloidal paths'and form into bundles which then give up energy, originatingirom the constant electric field to the alternating field of the cavity resonator to maintain the latter in a stateoi oscillation at a. constant frequency which is determined solely by its dimensions and the capacity between the anode segments. The appearance of this type of generator-which is. de-. scribed in further detailin my co-pending United States application, Ser. No. 78,533; filed March 9,1948, and also in. anarticle prepared by me which-appeared in-Helv. Phys. Acta, vol. XIII Fasc. Sext (1940-), is somewhat like that of an alternating current machine.- The ,cavity reso: nator determining the frequency along with the anode segments resembles a. stator while the motion of the electron bundles corresponds to the movement of the. rotor.

While this type of micro-wave generator has been found to. produce generally satisfactory results, it does, however, have oneoperating disadvantage thatste'ms from the so far unavoidable. coupling between the high. frequency magnetic field. within the resonator and the cathode which it encloses. l

such. coupling causes a loss of energy; because of; the high frequency currents induoedin the cathode that are free to flow offon the cathode input line,- and makes it possible, through the coupling, for the high frequency field to. besdisw turbed by extraneous fields and: charges that under optimum operating conditions should. be enti'relyexclud'ed. ,The general object of: the present invention is. to. overcome the above mentioned undesirable operating characteristic by eliminating the coupling between thehigh frequency magnetic field ofthe cavity and the cathode and specificallyby providing at least two cavity resonators enclosing the cathode and coupling these .resonators in a manner such that the instantaneous Sllmzof the high frequency fields simultaneously affecting the cathode is always equal to zero;

By. sodoing, the undesirable high frequency currents are 'nolonger "induced. in. the, cathode line, the resonators: are completely isolated from all harmful extraneous effects and one also is able to. enjoy the additionalv advantageof a much broader latitude in designing the cathode structureper. ser since research has shown that large surfaced cathodes aredesirable in the interest of increasing. the efficiency of the generator, the ratio of" the anode to the cathode diameters being particularly important. V I

Another specific ObjECtrlS. toprovide an improvedmicro-wave generator. having a pair of intercoupled' cavity resonators, the high frequency fields 'ofwhichare displaced 180 apart in phase. 1

Yet-:another. specific object is to providean improved. micro-wave generator having three associatedcavity. resonators for usein producing three phase oscillations, the high frequency; osci-llationsoitheseveral phases .beinajintercoupled so .aszto be displacedlZO-tapart in phase.

"The foregoing as well. as other objects and accompanying drawings. Fig. 1 is..a perspective view illustrating one embodiment of the invention. in which thegenerator is'provided with a Pair. of adjacent interconnected cavity resonators, the oscillations of which are spaced 180 apart in phase the usualmagnetic structure by which a; unidirectional; magnetic field -is-.established parallel: to .the. axis of the cathode, has been omitted forthe sake of simplicity. fig. 2 isa verticalsection; taken along the axis. of the. oath.-

r highfrequency oscillatory circuit produced by the" generatorsillustrated in Figs. 1 and'Z. Fig,

tors through the envelope surrounding the generator elements.

Referring now to Fig. l, the improvedv high frequency generator is seen to include the usual cathode I, heated indirectly by filament la,

having a relatively large surface for the emis sion of electrons and which lies along the axisv of a pair of annular, adjacently positioned, cavity type resonators legended A and B. The two resonators are combined in a single hollow cylindrical conductive structure made up from an outer cylindrical wall 3 of conductive material extending longitudinally of the cathode, annular conductive end walls 4 and 5 extending transversely of the cathode, a third transverse annular conductive wall 6' placed intermediate the end walls 4, 5,-and an inner cylindrical wall parallel with theouter wall 3. This inner wall is comprised of a cylindrical'array of spaced anode segments 1 extending parallel to the cathode inwardly from end wall 4 to a point just short of intermediate wall 6, a similar array of anode segments 8 extending inwardly from end wall 5 and which are aligned with the anode segments 'L-and a third cylindrical array of spaced anode segments 9,10 carried by the intermediate wall 5 and which extend'respectively in opposite directions therefrom. Anode segments 9, In likewise lie parallel to the cathode axis in thespaces between anode segments 1, 8 and terminate just short of the end wallsal, 5.

Resonator A is thus constituted by the;cavity defined by outer wall 3, anode segments 1, 9 and transverse Walls 4, 6; and resonator B is constituted by the cavity defined by outer Wall 3', an- I ode segments 8, l6 and transverse walls..5, 6.

- The capacity component of each resonator con-v sists principally of the inter-leaved segmentscarrie'd -by the end and intermediate walls, respectively and these segments during operation are at any-instant of opposite polarity. :LThUSfOI' example in resonator A, at the instant that the anode segments 7 secured to end wall are charged positive, the anode segments 9 secured to intermediate wall 6 will be charged negative, and vice versa, as the resonator circuit oscillates. Resonators A and B and the cathode l are all enclosed within an evacuated envelope II; a post '12 beaded into the lower end of the envelope is usedto support the resonator structure; filament la. and the surroundin cathode l are anchored in place by rigid lead-in conductors l3, M for the filament current which are also beaded into the lower end of the envelope; and parallelarranged lead-off conductors 15, I6, I! forthe high fre-f duency oscillations produced by the generator extend through bead type seals at theupper end of envelope I l in a direction perpendicular 'to the cathode axis, it being noted that conductor 16 is connected directly to the outer 'wall 3 at the common intermediate wall 6 separating the two resonators A and B while conductors and I! pass through slots l8, IS in outer wall- 3 well into the interior of the resonators A and B, re-. spectively, and there are turnedthrough 90" so as to present short, co-axially aligned coupling i. e. energy extracting sections l5a, Ila extending towards each other in a direction parallel to the cathode axis and which terminate at the intermediate wall 6 and are electrically connected to the latter at the junction point.

The construction of the ultra-high frequency generator shown in Figs. 2 and 3 is substantially the same as the one shown in Fig. 1 and for ready comparison between the two structures, like reference numerals but with primes added thereto have been used to designate like parts in the two structures. In addition, the pole pieces 22, 23 of a generally C-shaped magnet are shown in Fig. 2

at opposite ends of the cathode l on which are wound field coils 2d, 25 that are energized from a sourceof' direct current, not illustrated, to establish a unidirectional magnetic flux parallel to the cathode axis which is essential to the generator. As previously explained, the corresponding field structure associated with Fig. 1 has been omitted in the interest of simplifying the disclosure.

As can be readily observed by a comparison of Figs. 1 and 3, the only difference between-the generator constructions in Figs. 1 and 2 lies in the manner in which theanode segments associated with the end walls of the resonators are arranged. In Fig. 1, two galvanically' separate and'aligned arrays of segments 1 and 8 are utilized whereas in Fig, 3, the aligned segments in each array are seen to be continuous between the tWo'end walls 4, 5, and arcuate notches 26 are cut into the intermediate plate'6 to prevent cont'actbetween the latter and these segments. Thus although the anode segments are actually one continuous body of material, separate legends "l-,-8 ---have-nevertheless been used thereon to designate-the anode portions associated respectively with resonators A and B'. I

It will now be apparent from what has been said that the generators shown respectively in Fig; Land Figs. 2, 3 each provide dual, high frequency oscillatory circuits, one including resonator A and the other resonator B, with the cathode I common to both circuits. Considered separately, each of the resonators operates in accordance with the previously explained principles." 3

stated at the outset; the principal object of this i'nvention is 'to more effectively isolate th cavity resonator component of'the generator from all extraneous charges or fields that might exert a disturbing influence on the high frequency oscillations generated because of the inductive cou- 'pling between the high frequency magnetic field and cathode. The desired result is obtained in Fig. l and Figs. 2, 3 by providing dual resonators and arranging these such that the respective phases of the high frequency fields are stage gered by".1 That is to say, the field in 'on resonatoris always opposite in direction to that intheother resonator, such condition being illustrated schematically iri"Fig. ,2 by the usual 65 and'Q direction symbols. Under these canal-- tions, the induction eifects of the two 'high'fre .terunderstanding of the. nature of th'ecoup'ling to beapplied, reference should be made to Fig. 'ithat-shows schematically two oscillatory circuitsoa and b -connected'in' parallel and oscillating in opposite phaseasindicated by the directional arrows. oscillatory circuit a corresponds to resonator A and oscillatory-circuit b to resonator B. Condenser-plates 3-0*of circuit Ia'repre sent the capacitance of anode segments 1, '9 of resonator A; condenser plates 3'l= of circuit b represent'the capacitance ofanode segments 8, I oiFre'sonator'B; coil 32 represents the inductance of circuit aconstituted by end walls 4, 6 and that half of. outer wall 3 included therebetween; and coil 33' the inductance ofcircuit. lr constituted by end walls- 5, I6. and the. other half of outer wall 'Sincludedtherebetween.

'The'coupling between points 34 and 35 of the two circuitsin the generator'shown in Fig; l, and also in. the modified .c'onstructi'on shown in Figs. 2; 3is established by the conductive intermediate wall fi'which iscommon'to both resonators. The coupling between points 36 and 31 of the two oscillatory circuits is, however... established by .difierent means in the two constructions in Fig. 1,, suchcoupling is'produced by direct connection of: the symmetrically arranged 'couplingloops l a, We. of the two lead-oil conductors l5, 1''! which terminate at the conductive intermediate wall ii;v

- while in the Fig. 2 construction, such coupling is established by virtue. of'thefact that correspond- Fig. 5 illustratesstill a'thilid'manner of, forming the connection betweenpoints. 3.6,. 3'! of the twooscillatory circuits. at. andb for .a. generator having the resonator structure. of Fig. .1. Here it is. seen that the necessary interconnection is established by a. conductor 38 having acoupling lo.op..38a disposed. within resonator A" and a similar. coupling. 100pfl38 within resonator .B" but looped in the opposite direction, the terminalends of the conductor being connected to the intermediate transverse wall 6", and being passed through an opening 39inv the latter.

It is easily seen that only a state. of oscillation can be formed which induces like-directed currents in the two looped portions of conductor 38, as shown bythedlrectionarrows. This is possible, however, only when the two fields are in opposite phase,..as. shown, the purpose of; the wire loop '38 being thusfilled. I .Fig. 6 illustrates in a somewhat diagrammatic form a further modification utilizing three resonatorsintercoupled 'in such. manner that their respective high frequency fleldsare staggered in phase by 1 20 electrical degrees. I generator is especially suited for producing three phase high frequency oscillations. Basically, this form of the invention is the same as that shown in Fig. 1 and, in the interest of simplifying the drawings, only those anode segments lying in the plane of the cathode axis :r--.'z: have been illustrated, and the cathode itself has also been excluded. As with the other embodiments, the resonator structure is comprised of an outer cylindrical wall 40, parallel with the cathode axis, annular end walls 4|, 42 transverse to the cathode axis and a pair of annular transverse walls 43, 44 intermediate the end walls so located as to divide the interior into three, like dimensioned resonators C, D and E. Circular arrays of anode seg- This form of ments 45, 46 extend inwardly from end walls 4|,

6 v ments 41-, 4'8 extend in both directionsl from the intermediate walls 43', 44; respectively, soas 'to lie in the spaces between the anode segmentsiflg Coupling loops 5 I, 5 2 and'53 extend respectively into thethreeresonators C, 'D and El-for extract; ing high frequency energy from the generator;

and these lead'via concentric lead- ofi waveguir'i'esv 54, 55, 56 to astar connected three phase load apparatus-indicated diagrammatically by th'e rece tanglesil. Y

Inorder'that the three resonators C, D men shall have the necessary phase displacement of coupling connections '58, 59 must be- .vi'ded. "Connections 58, seen tobe-of the capacity type couples conductors "5'4 and 55-; and conneee tion- 59, also of the capacity type-couples: cone iductors'ifi-and 56. By correct choice of "thedistance ."yand 2 between the outer wall and coupling connection 58-, 59 respectively, which in'the simplest manner is determined imperica-lly'. the desired "phase displacement between' resonators C', D. E can be effected without di'iliculty; so that, for example, resonator D oscillates, with a phase displacement of 120 in relation to reso nator Cyandf resonator E with a phase displacement of 240" in relationto resonator C. In this. way, the sum of the inducing effects of the high frequency magnetic field's ofall three resonators.

on the cathode is equal to zero; and radiation of high frequency energy through the catho'de made impossible;

'In't'he dual resonator generator construction shown in Fig. 1, it"i's of advantage to maketh'e connection between the high frequency conducp tors inside of the envelope so that onlytwo conductors need be .carried'out' of the envelope'ior coupling out the high frequency energy. Such an arrangement is illustrated. in Fig.1? where it. will be seen that lead-off conductor I5? isxconnected 'bya bridge 60' to conductor 11"" within the envelope 'II"', and hence only conductors. IT' and 16"" are then necessary for leading. out the high frequency energy; The two cathode lead-ins l3"" l4 are then preferably led; out of the envelope l'l'" on the. same side 'asconductors' IB, l1""., the four conductors. l'ieingarranged in the form of a cross.

I claim:

.1. Amicro-wave generator comprising a cathode; a..plurality of like annular hollow resonators-surrounding said cathode and located in side-by-side'relation along the cathode axis and concentric therewith,..each of said resonators including, annular. end walls and bounded in-Ja radial direction by an outer cylindrical wail and aninner' wall constituted by a cylindrical array of Iinterfi'tti'ng anode. "segments. terminating, in alternation on said end walls; means adjacent said resonators for establishing a unidirectional magnetic field within the space defined by said inner wall of each resonator and parallel to the common axis thereof; means symmetrically arranged in the respective resonators for extracting high frequency energy therefrom; and means intercoupling said resonators together and so constructed and arranged that the inv ductive effect of the high frequency magnetic fields produced respectively by the resonators with respect to the cathode is zero.

2. A micro-wave generator as defined in claim 1, wherein said means intercoupling said resonators includes said symmetrically arranged means for extracting high frequency energy from the respective resonators.

3.,A.; micro-wave generator comprising an evacuated envelope housing a cathode; an annular resonator structure disposed concentrically about said cathode, said resonator structure comprising annular endwalls, an outer cylindrical wall extending between said end walls, an intermediate annular wall parallel with said end walls and an inner cylindrical wall constituted by a cylindrical array of interfitting anode segments terminating in alternation on said end and intermediate walls, the annular space defined between one of said end and intermediate walls and the inner and outer wall section therebetween constituting one resonator, and the similar space defined by said intermediate wall and the other end wall and by the sections of the inner and outer walls therebetween constituting a second resonator; means adjacent said resonators for'establishing a unidirectional magnetic field within the space defined by the inner wall of. each resonator and parallel to the common axis thereof; lead-off meanscoupled to each resonator for extracting high frequency energy therefrom; and means including said intermediate wall that is common to both resonatorscoupling the latter together in parallel and so constructed and arranged that the inductive effect of th high frequency magnetic fields pro- [duced respectively by theresonators with respect 'to said cathode is zero.

4; A micro-wave generator as defined in claim 3 wherein said coupling means comprises means coupling together the high frequency lead-off .means of the respective resonators.

'5. Amicro-wave generator as defined in claim 3'wherein said coupling means comprises means interconnecting the high, frequency lead-olf- '3 wherein said coupling means comprises a coupling loop extending through an aperture in said intermediate wall into both resonators and which surrounds the respective high frequency fields of the resonators in inverse sense.

7. A micro-wave generator comprising a cathode; three annular hollow resonators disposed concentrically about said cathode in side-by-side relation, each of said resonators including annular' end walls and bounded in a radial direction by an outer cylindrical wall and an inner wall constituted by a cylindrical array of interf'fitting anode segments terminating in alternation on said end walls; means adjacent said resonators for establishing a' unidirectional magnetic field within the space defined by the said ne l, p each ire na p l.a dy a a l l i m n axis p :13 10 m? metrically positioned .with respect to the ree spective resonator "for extractingv high frequency energy therefrom; and means intercoupling said resonators together and so constructed and arranged thatthe respective high frequency magnetic fields produced .by said resonators are apart in phase.v f I 8. A micro-wave generator as defined in claim 7 wherein said intercoupling means includes capacity type connections extending between said lead-off means. v vI 9. ,A micro-wave generatorcomprisinga cathode; an annular hollow resonator structure disposed concentrically about said cathode; said resonator structure comprising end walls, an outer cylindrical wall connecting said end walls, a pair of spaced annular walls arranged parallel with said end walls and intermediate thereof, and an inner wall constituted by a cylindrical array of interfitting anode segments terminating in'alternation on said end and'intermediate walls, the annular spaces defined respectively between said end and intermediate walls and the inner'and' outer wall sectionstherebetween constituting three like resonators; ineans fadjacent said resonator structure for establishing a unidirectional magnetic field within the space defined by the innerfwall of each resonator and parallel to the common axis thereof; lead-01f means cooperative with each resonator for ex.- tracting high frequency energy; and means including said intermediate walls intercoupling said resonator chambers together and so .0011- structed and arranged that the, inductive reflect of the high frequencyjmagnetic fieldsproduced respectively by theresonators with respect to said cathode is'zerofi p' 10. A micro-wave generator as defined inclaim 9 wherein the means intercouplingsaid resonators also includes capacitive type connections between the said lead-o'fi means cooperative with the several resonators. 7 I Y FRITZ LUDI.

E ES ITED The following references are of record in the file] of this patent:

UNITED STATES PATENTS Number Name 3 Date 2,115,521 Fritz l Apr. 26, 1938 2,128,237 Dallenbach Aug, 30, 1938 2,144,222 Hollm'alln I. Jan 1'7, 1939 2,233,261 Hollmann "Feb.,25, 1941 2,409,222 Morton "Oct-l5, 1946 2,463,416 Nordsieck

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