US2366555A - High-frequency apparatus - Google Patents

Description

,Jan? s. RAMO HIGH FREQUENCY APPARATUS Filed March 1, 1940 6 Sheets-Sheet l LMATTT Inventor Simon Ram o.

Their Attorney.

Jan. 2, 1945. s. RAMO HIGH FREQUENCY APPARATUS Filed March 1, 1940 6 Sheets-Sheet 2 Inventor Simon Ramo Their Attorney.

Jan. 2, 1945. s M 2,366,555

HIGH FREQUENCY APPARATUS Filed March 1, 1940 6 Sheets-Sheet s Inventor Simon Rahfio n- Attorney.

2, 1945. RAMQ I HIGH FREQUENCY APPARATUS lziled March'l, 1940 6 Sheets-Sheet 4 I Inventor Simon Rama,

by Then Attorney.

Jan. 2, 1945. A' 2,355,555

HIGH FREQUENCY APPARATUS Filed March 1, 1940 6 Sheets-Sheet 5 Fig.2.

\ l l I I I Inventor Simpn Ramo;

b 7% 6. Th el r Attorn ey,

Jan. 2, 1945. s RAMQ 2,366,555

' I HIGH FREQUENCY APPARATUS Filed March 1, 1940 6 Sheets-Sheet 6 70 BATTER) m 1H l5b.

A18 T0 BATTERY Inventor Simon Ram 0-,

Their Attorney.

Patented Jan. 2, 1945 .IHIGH-FRE UENGY APPARATUS Simon Ramo, Schenectady, N. Y assignor to General Electric Com New York pany, a corporation of ApplicationMarch 1, 1940, Serial No. 321,746 .5Claims. (01. 250 27) f The presentinvention relates to improvements in electronic apparatus for obtaining amplification and other conversion effects at frequencies f so high that electron transit timeconsiderations play a controlling part in apparatus. i v

The invention makesuse of the so-called velocity modulation principles which aredescribed in U. S. Patent No. 2,220,839, 1 granted November 5, 1940, in the name of W..C. Hahn. However, whereas Hahn has employed an elongated beam tube of the cathode ray type for producing the effects desired, it is proposed in the present instance to utilize a more compact structure in which the electron beam is caused to traversea helical or other complex path. A significant advantage, in addition to compactness, which is realized by this means consists in the possibility of causing a given element of the electron stream to traverse the same modulating or energy-abstract ing agency a large number of times so as to produce cumulative effects.

The features desired to be protected herein are the operation of the pointed out with particularity in the appended an amplifying system; Figs. 4, 5, and 6 are diagrammatic representations useful in explaining the invention; Fig. '7 is a sectional view takenon line'l-l of Fig. 1; Fig. 8 is a cross-sectional view showing an alternative embodiment of the invention; Fig. 8.a is a fragmentary sectional view illustrating aparticular detail of Fig. 8; Figs. 9 l and 10 are diagrammatic perspective views, taken in different planes, of afurther alternative application of the invention; Fig. ll is a diagrammatic representation useful in explaining the operation of the apparatus of Figs. 9 and 10; Figs. 12 and 13 are partial setional views taken in different planes of .a fourth possible embodiment of the invention; Fig. 14 is a sectional view, taken on line Id -Moi Fignl2; Fig. 15 is a diagrammatic viewshowing still another development of the invention and Figs. 15a and lb are fragmentary sectional views illustratingceiw tain details of the construction of Fig. 15.

Animportant feature of the invention con-. sists in the provision of means for producing a stream of orbitallymoving electrons in which the center of orbital motion progresses continpair ofsemi-circular plates l2 and I3 (Fig. 2--a) which are connected by an axially extending wall part I4. It is providedat the other end with a pair of electrically separate collecting electrodes l5 and. I6. p

For the production of an electron stream there is provided an electron gun comprising :a cathode l8 and a pair of accelerating and focusing cylinders l9 and 29. .After issuance from the gun, I the'electrons are caused to .move more or less tangentially with reference to the .wall of the cylinder II by means of a deflecting'plate 22 which is adapted to be maintained at a slightly positive or negative. potential with respect to the cylinder. Deflection inthe other plane, that is, axially of the cylinder, is accomplished by a second deflecting plate 23 which is appropriately biased for that purpose. Y i

' After traversing a generally'semi-circular path the electrons enter the main space enclosed by the cylinder H through an opening 25 provided axially of the envelope by means of magnetic V coils, suchas are indicated n21. In this way the beam is caused to traverse afhelical path as the electrons progress along the tube toward the collecting plates l5 and IS. The electron path is indicated most clearly by the dotted line A which is shown in the diagrammatic representa- -"tionofFig.3..

. The various elementsof the electron gun and the deflecting plates 22 and 23 .may. be 'maintained in the desired potential relationship by "being connectedto an-appropriatevoltage source,

which is conventionally representedin the drawence of gaps between their edges and the correspending edges of the openings.

Referring particularly to the electrode .34,.it is.

contemplated that this electrodelshalllbaused.as.

an input element in a manner analogous to an input grid. If it be assumed in this connection that-the potentional of the electrode is-caused ticfixedand' invariable time.

is experienced in assuring a desired correlation between the orbital transit time of the electrons and the'rate of potential variation of the input electrode. This is due to the fact, demonstrable mathematically, that the time required for the various electrons to complete a single orbital turn is controlled exclusively by the strength of the magnetic field. Consequentln. for. a given field strength, irrespective ofthe velocity; with which a given electron may leave the electrode 34 after an initial traversal of the gaps 31 and 38, it will return to the vicinity of the electrode within a Therefore, if the strength of they magnetic field is properly adjusted lto'causethetime of orbital transit of each vary at high frequency with respect totthe; po-

tential level of the cylinder l I, it is apparent that varying 'p'otentiaP gradientsa will?v be: established across the: aps which bound the. electrode: including especially the gaps 31 and"- 38 which; ex:-

tend longitudinally-of the cylinder. Moreover;

the gradientsthus produced wilL' obviously tend to aifect'in some degree tnevelocityofltheelectrons' whichsuccessively traverse the gaps in their passage" around the: circumference: of the cylinder H Ithas be'eII"pointed outinlthe aforementioned Patent' No. 212205839 of' C; Hahn that cumulativemodulati'on effects" may be: obtained with a two-gapelectrode system provided a proper relationship exists between the dimenslumsof the electrode; the velocity of the electronstream and the desired operating frequency of the system; More specifically; with reference to an arrangement such as that shown in Fig. 1-, such cumulative effects maybe obtained" provided the transittime'of a given electron passing'across the face of the -electrode 34 between the gaps 31 1 and 38- is equal to a half-cycle of the: operating frequency or tosomeodd multiple thereof; Und'er these circumstances it". is found that;- an: electronwhich is acceleratedas'; it passes the first gap 315willbe again accelerated: as. it. traverses the secondagaptt'. Similarly; an'felectronn which starts out at such. a point inthe: cycIe of. potential variation of the electrode: 34 asl to be. decelerat'ed; at the gap: 351" will be furtherdecelerated upon its traversal of the gap 38: 'llhistn'iode. of

operation: not; only provides arr extremely efiectiive mechanism: for producing velocity variations the electron stream, but also; avoidst certain ;ationand, in fact,.that their application to such a' system presentscertain important. advantages. In particular, it is to be noted that with the construction of Fig. 1,, the various electrons may be caused to traverse the modulating gaps 3'15 and 38,

a plurality of times (see Fig. 3), so that, with proper phase adjustments, the effectiveness of the input System may be multiplied. without complication of structure.

In an arrangement such asthat shown wherein the helical path of' the electrons is controlled by means of a uniform magnetic field, littIe difiiculty electron to: correspond to some whole number of cycles of the operating frequency, the effect of the: input system; upon such electron will be additiveior; each of its successive traversals of the electrode 34. The diameter of the electron orbit may be controlled andmade commensurate with the dimensions of" the cylinder- H'; by appropriate regulation of the velocitywith. which the.- electron are projected from thaelectron source:

The matters referred to in the preceding para.- graph may be more clearly understood by referrin-gto- Fig. 4.- I-nthis. figure the solid line B may be taken torepresent the assumed path of an: electron whose velocity: corresponds tothe average or unmodulated velocity of the electron stream. Thepoint 0 is considered to represent a region: in which the: stream subjected toa high frequency modulating. potential. An" electron which passes the modulating agency in such time phase as. to be accelerated"- thereby, may be expected tof'ollow' a path of somewhat greater radius than the pathB, such enlargedpathbeing represented; for example, by: the dotted line C. 0n the other hand, d'ecelerated electrons will describe asmallerorbit as indicated by the dotted line D. Theoretical analysis shows,.however; that each electron will require precisely the-same time to traverse its orbit and return to the point I). Moreover, itis found" that each electron" will pass through the point 0 along a line substantially coinci'dentwiththat of its initial transit.

Fig; 5 shows theway in which the considerations discussed above are affected bythepresence-of a component of axial velocity in theelec tron stream motion; 'Thus; in, thi figure, the solid line E represents the path of a hellcally movingelectron of average velocity; while the dotted lines F and G respectively show th'e lines followed byelectrons which are respectively accelerated and decelerated? by the effect of modulatihg potentials applied as the various electrons traverse the region occupied bythe line 0'; It will be noted that for the ease of repetitive acceleration the electron orbit increases progressivel'y, while for the case of' repetitive deceleration a progressive decrease in electron orbit occurs. However, the trajectory of each electron causes it to pass repeatedly through the line 0'.

In orderto understand the possibilityofobtaining amplification effects as a result of' the phenomena discussed in the foregoing, it, will be helpful torefer-t0 the action ofa circularly mov ing electron stream which is caused to traverse a modulating gap subjected to; cyclically varying potential gradients. Thissituation is, illustrated diagrammatically in Fig. 6, which may betaken to show-the'conditions occurring at" various points around the orbit of an, electron stream which is caused to traverse a modulating gap at 0". For the case: illustrated, it is assumed that thefre- 2,366,555 quencyof potential variation across the gap is such that eight complete cycles of variation occur duringv the time required for a single electron to traverse its orbit. The solid dots .a may be taken. to represent. individual electrons, and, considered in the aggregate, they show the cone dition of the beam at a particular instant of time.

- As' the various electrons move azimuthally,

those whosetvelocity exceeds the average beam velocityseek an orbit ofgreater radius, while the decelerated electrons seek an orbit of reduced radius. As a consequence of this action, observae tions taken between variousclosely spaced azi niuthal planes will show that the electron density measured at most points around the electron path varies materially with time. i This variation is; mainly a function of the relative displacement of the centers of gyrationof the various electhe two modulating gaps 3'! and 38 in no way aifects the applicability of the. discussion which has been given above). The relatively great axial length of the electrode 34 assures that each electron will passit a plurality of times, the number of such traversals being determined, of course, by theapitch of the helix which the electron stream describes. The resultant high degree of velocity modulationproduced in the stream before it [and the gaps 39 and: which bound this electrons and is found to be greatest between planes which are located approximately ninety mechanical degrees from 0", such planes being indicated atband 11"..

t It will be noted that at the instant whichyis of the beam between the planes 2) and. b willbe characterized by-a high degree of .charge density modulation, that is, cyclical variation of electronidensity with time. On the other hand, in a- 'region displaced ninety degrees from that just considered, that. is to say,-between the planes'c and c',-substantially no variations of the charge density with time will be observed, and. it may therefore be said that atthis point the charge density modulation ofthe beam is negligible.

. The condition of negligible charge density modulation last referred to will be realized: again when the beam returns to itsstarting point at the-region 0", and at this point the beam will be characterized by its initial, relatively uniform charge density, although the velocity variations produced by theprimarymodulating action" of the modulating system will still exist in the beam. Upon a further traversal of the gap by the electron stream, these variations will be increased in'accordance with the principles previously explained; Therefore, since the charge density modulation occurring between planes 1) and 11' is afunction of the velocity variation which p'roduces' it, it is apparent that such charge density modulation will be greater for each successive orbital passage of the electron stream;

As a result of the considerations stated in the foregoing, even a relatively slight velocity modulation produced at the modulating gap 0" may,

by additive action, be made to cause relatively great charge "density variations in the region b,

bf. Therefore, if some means, are provided by i which the charge density variations existing at connection to an appropriate input circuit, be caused to-produce velocity modulation of x the passes beyondthe extremity of the electrode may be expected to produce a correspondingly high degree of charge density variation in those azimuthal planes which include the electrode 35 trode. Consequently, if the electrode mentioned is connected to an appropriate circuit, an output voltage of useful magnitude maybe obtained.

' The provision of two gaps at the adjacent edges of the electrode 35 serves a function analogous to the two gaps provided in connection withthe input electrode34. Specifically, if the dimensions of the electrode 35 are properly correlated to the electron transit time, cumulative energy abstraction'eifects will be produced at the two gaps.

This condition is most adequately fulfilled when the dimensions of the electrode 35 correspond to those of the electrode 34. ,Again, for reasons analogous .to those given in connection with the inputstructure, additional cumulative efiects may be obtained by causingthevarious components ofthe stream to traverse the various output gaps a large number of times-as by the use of an output electrode which is of relatively great 9 length with respect to the pitch of the helical path of the stream. v

A diagrammatic view of the amplifying system which has just been described is provided in Fig. 30f the drawings. In this figure an input electrode'34, corresponding to the similarly numbered element of Fig. l, is shown as being connected to an input circuit which includesthe parallel combinationof an inductance 45 anda condenser 46. Similarly, an output circuit connected with the electrode 35 is shown as comprising an induct- L ancex=41 and a capacitance 48. The application of a relatively weak signal to the input circuit wouldzbe expected to result in the production of a much stronger signal in the output system as a result of the amplification effectsabove described. The construction shown in Fig. 1 incorporates certainpractical feature which have not so far been described and which include twosemi-cylindrical metal parts 50 and 5! (see Fig. 7). These are. placed in juxtaposition and are joined at their abutting edges by the provision of outwardable back-coupling between the variou electrode I elements. i

For supplying voltage tothe input electrode 34, there is provided on the outer peripheral surface of the shield part 50, a tubular metal member 55,

which. in combination with a lead-in conductor 56, forms a concentric transmission line suitable for connecting the electrode 34 to a signal gen crating orreceiving agency. A similar concen- ,tric line arrangement is provided inconnection I with the output electrode 35, the outer member of such system being shown at 58min Fig. 7 and the inner member at 59. l

, In addition to the use of the apparatus-of Fig. i

has an. amplifier. itmay/ alsabe; employ d fO-I'dfl tcctionpurposes by appropriate u eor the collect? ins: electrodes l5. and I 6;. @When: the apparatus is employed for this. purposano use. is made of the output; electrode. 35.). In. detectinga received signal. the signal is: impressed on the. electrode 3.4 in. accordance with. the. procedure previously discussed. As: a. result or the. modulating client of the electrode. the electrons which are. decelerated ar caused totraverse an orbit of: smaller radius than thenormal orbit of the. unmodulatedportier); oi the electron stream.v This latter factor is used in. the. production of detectiorrreffects in the following manner. 1 The diameter or-the electrode I15. is; made surcently small s that in. the absi-z-ncev of a modu lating signal; applied to. the electrode 34 substantially the; entire. electron. stream impinges: on the electrode; It... However; when. the. beam is modulated.- by the: application. of: a. signal to the input electrode 3. the decelerated electrons; areenabled to. reach the; plate} [5. as. a. result of their reduced: orbit. Consequently, an appropriate circuit connec ed to the plate. l5 may be made to develop; a. 11-0., voltage of varying magnitude depending-upon the low frequency variations of the I input signal. Such a circuit is shownin' the drawing as including a resistor 60' connectedin series: circuit with, the electrode. I and having a. pair; of output terminals (it connected across it.

The? invention may be: practiced, with numerous structure other than that which is illustrated in la. 1% and one alternative embodiment is shown in: Fig. 8.. Inthis case,ithe. electrode structure is enclosed within an; insulating envelope 65 which includes; a, deeply reentrant portion 66;. For the establishment of an electron beam or proper character there is provided an,electron, gun having as part; thereof, a generally annular cathode-68 whose.- outer peripheral surface is activated to assure electron, emission thereof upon heating of the athode. The annular stream of electrons which is generated by this means is concentrated into. a. thin, sheet by the application of approtained. at the. higher potential for this purpose.

They agencies referred to, taken in connection with, a strong magnetic field assumed to be produced axially ofthe, envelope by means not shown in the drawings, cause the electron stream to movetoward the, end of the envelope remote from the,- cathode W in .a, hollow continuous sheath which has components both of rotary and of axial motion. ,lAfi in the arrangement of Fig. 1 the. motion. of; any" individualelectron in the streamis along-1 a helical path. For the production of' high frequency effects there is provided anelectrode system which includes a; pairofcwaxial cylinders 15 and 'lfi. At the: top, of each cylinder,; in the position illustrated-in.the drawings; there is provided a rectangularr opening, such. openings being shown at 18 and 19; as" beingin aligned .relationship.- The openings referred to are occupied 'by r'ec'tangular electrodes; 801 and" 8:! which conjointly serve a Further, during its pas- 7 function similar; to that-served by the inputckfi' trode 3A' or Fig. 1'. In this connectionthe trodes tillv and 8i are both providedl withlead-in conductors as indicated at B3; and. 8:41 andinuse;

are connected to; a common source. of high fro.- quency potential (not shown). The action of the! electrodes .8U1and 18%. on the. beam is precisely similar to that of'the electrode 341 of Fig. Land need not be further described. It may be pointed outhowever', that the. use of two oppositely dis posedelectrodes tends to produce. a; somewhat stronger modulating effectthan that produced.

atsingle electrode element. a i p At the extremities of. the cylinders 1'5 and 16 additional rectangular openings. are provided which accommodate an output. electrode: in the form of a. U.-shaped.-' member hauing opposed plate-like parts: 86 and 8-11 ('see' Fig. 8a).; The

. structure thus formed. is. adapted to. serve as. an

ture is. that shown in Figs. 9 andld wherein only the high'frequency electrode system is illustrated. I The view which is. represented in Fig: 1-0 will be recognized. asv bein taken in. a plane ninety degrees displacedfrom that of Fig. 9-. In. both figures; the enclosing envelope is omitted ior'the sake of clarity;

The construction which is illustrated in the figures just referred to comprises a uni-potential part having a generally cylindrical 'center portion and a pair of quadrangularly displaced end-portions 95. and 91 All these portions: are of hollow configuration- The end portion. 98 is arranged in face-to-face' relation with an independent semi-cylindrical part; 99", which. is: also by meanstof an: input circuit which is illustrated as including the parallel combination of an inductance lll-3:and acondenser l M'.

In accordance with the principles. previously described, the various elements: of the electron stream which traverse the gaps: i012. I'D]? existing between adjacent edges; of the parts:v Miami 96 will bevariously affected in. velocity depending" on the potential relationship which exists between the parts at the instant of'such traversal.

Thus,' certain electrons which traverse: thegap H'hi. will be accelerated, while other electrons which traverse this gap will be decel'era-ted. Ad. ditional velocity variations of generally similar character will be produced-at the gap I 01."

' For present purposes it is desired that successive modulating impulses produced in the manner specified in the last paragraph shall havecumu'e lative effects with respect to the production of Similarly, the end. por..

displacement of the centers of gyration of thevarious electrons. For this reason, most effective operation of the particularapparatus shown in Figs. 9 and will obtain. when the velocity changes to which any given electron is subjected atthe two gaps I06 and I01 are subtractive in nature. That is to say, it is desired that an electron which is subjectedto an accelerating influence at the gap I06 shall be subjected to a deceleratinginfiuence at the gap I01. When I23, I24, I and I26. The separate pairs of slots are ,quadrangularly displaced and are substantially filled by conforming electrode elements.

numbered I21 to I respectively. The oppoe sitely disposed electrode parts are maintained at a common potential by the provision of U-shaped connecting parts indicated at I32 Iand I3 3.

The transverse dimensions of the electrodes I21 to I30 are made such that the electron transit time across them corresponds approximately to a half-cycle of the intended frequency of operation of the apparatus or, for extremely high frequencies, to an odd multiple thereof. Furtherthiscondition is realized, the path of an initially acceleratedelectron may be as indicated by the dotted line J of Fig. 11 in which the solid line I represents the normal trajectory of an electron of average intensity. 0n the other hand, an electron which is subjected to deceleration upon its first traversal of a modulating space will be caused to move as indicated by the dottedline K. This representation, which assumes that each electron is oppositely afiected as it passes two diametrically spaced modulating gaps, dem; onstrates the possibility of obtaining a wide and rapiddisplacement of the electron orbits by the means specified. 1

As previously stated, such displacement results in the occurrence of charge density modulation in parts of the beam which are displaced from the velocity-affecting gaps. The charge density modulation thus provided may be utilized in the production of amplification eflects by appropriate utilization of the electrode I00 in connection with an output circuit, such as that formed by the tuned combination .of a condenser III) and an inductance I I I. It will be noted that the electrode I00 is so positioned with respect to the other parts of the system as to provide a pair of gaps which are quadrangularly displaced from the gaps I06,I01. cated at I I3, is apparent in the drawings.) For reasons which have been previously given, the charge density variations occurring in the beam are greatest in the vicinity of these gaps so, that the effect of the beam on the output system is a maximum for the arrangement illustrated. Consequentlyinview of favorable differences in magnitude between the charge density variations and the velocity variations which produce thema relatively weak input signal applied to the electrode 99 may be expected to produce an amplified output signal across the terminals of the circuit IIO, III. I I 1 The modification shown in Figs. 12, 13 and 14 of the drawings represents a combination of the principles employed in the construction. of Fig. 1 with those which are utilized in the arrangement of Figs. 9 and 10. In this case, an electron beam generated by an emittingsource H5 is caused to traverse a hollow cylinderI I6 which it enters through a small opening II9 provided in one of the bounding, surfaces (I I8) of the cylindrical enclosure. A deflecting electrode I2I positioned in the vicinity of the opening IIB serves to impart a component or axial velocity to the beam. This factor, taken in connection with the influence of a strongaxial magnetic apair of opposedrectangularslotsas indicated at (Only one of said gaps, indiconnects the electrodes I21 and I28 to produce more, the total circumference ofjthe cylinder II6 should be such that the time required for a given electron to pass from a selected point, say, the electrode I21, to a diametrically opposite point (that is, the electrode 128) will correspond to a whole number of complete cycles of the operatingpotential. With these conditions fulfilled, a given electron which is twice accelerated as it successively traverses the gapswhich bound the electrode part I21 will be twice decelerated as it traverses the gaps associated with the electrode part I28. Theconverse will hold for an electron which is initially decelerated. As a consequence of these circumstances, there will be a strong tendency for relative displacement of the centers of gyration of the various electronsto occur. As has already been explained, this provides a mechanism by which amplification efiects may be obtained. i

As in the arrangements previously described, 1 the electron beam, after its modulation by the which include these electrodes, strong excitation of the output system associated with such electrodes may be obtained. I

In the use of the system for'amplification purposes, input voltage may be applied between the cylinder II6 andthe conductive part I32 which modulation of the electron beam. An appropriate circuit for this use may include the parallel combination of la condenser I35 and an inductance I36. A tuned output system is illustrated as including an inductance I31 and a condenser I38.

A still further development ofwhich the invention has been found capable is illustrated in Fig.

beingthe separate invention of John P. Blewett and is claimed in copending patent application Serial No. 385,437, filed March2'1, 1941. I

In this case there is shown an evacuated envelope I40 (indicated in dotted outline) which encloses a linear cathode. I4I of generally filamentary character. (The active portion of the cathode is assumed to consist of. the; region between the points e and f.) Surrounding the oathode :and extending generally coaxially therewith there isprovided a high frequency. electrode system mcluding a seriesof cylindrical parts I42 to r the following.

. vo field produced by some appropriate means (not The cylinder I42, which subtends a major portionof the cathode l4I,1is maintained 'at a positive potential with respect to the filament so as to produce radial motion of the electrons emitted in its vicinity. This motion is converted into orbital motion. by-means of a strong magnetic field established in a direction parallel to the cathode, as indicated by the heavy arrow M. Also a unidirectional potential is impressed between the electrode I42 and the electrode I43 to cause the electrons to' move axially along the electrode system in the direction of the higher numbered electrodes. If desired, further unidirectional potentials may be applied to the other electrodes of the system, (namely, the electrodes I44, I45 and I46) to increase this axial motion, but satisfactory operation of the apparatus will obtainif all these parts areat a common potential with the electrode I43. A direct current source such as a battery I49 may be employed for maintaining the potential relationships referred to. r 3

As appears more clearly in Fig.-15--a ,'the electrode I43 COHSlStSZOf a split cylinder having two semi-cylindrical conducting parts, M311 and H517, which are insulatingly spaced, and which define a generally cylindrical chamber-between them. In the use of the apparatus, these parts are subjected to analternating difference of potential by vmeans of an appropriate input circuit which is illustrated diagrammatically as including simply a pair of parallel conductors-[| and I52. These conductors are assumed to constitute a standing wave transmission line (e. g. a quarter wave line) which may be excited in any desired fashion. A common battery'connection I53 for the two conductors is provided for the purposeof maintaining the average potential 'of the electrode parts 143a and I 43b at a desired value.

By the input arrangement specified, cyclically variable voltages are developed across the gaps which separate the electrode parts 143a and 1431).

Consequently, if the circumferential dimensions of the parts areproperly correlated to the orbital velocity of the electrons and to'the operatingfrequency of the system, cumulative modulation ef fects may beobtained asthe various electrons successively and repetitively traverse the said interelectrode gaps.

Amplification is obtained with the apparatus described above by making theelectrode I45 also of a split cylinder construction, asshown in Fig. l5--b and by connecting the parts 145a and H51) to an appropriate output circuit-which is represented diagrammatically as including a pair of parallel conductors I54 and 155. As the various components of the previously modulated beam successively traverse the gaps existing between the electrode parts M511 and I451), excitation of these parts will be produced and an output voltage of significant magnitude will be developed charge in a system in which the electron source comprises a centralfilamentas just described; In this situation, the theoretical considerations which indicate a quadrangulardisplacement of the input and output'gaps for cases of relatively low electron density no longer' apply with complete accuracy, and a determination ofthe best relationshipbetween the location of the input gaps and the location of the output gaps may best be made by experimental methods. Even in the arrangements previously referred to, wherein the electron source comprises an electron gun-or the likeQan experimental adjustment of the gap rela tionships should be made provided the current density employed is so high as to make space charge a significantfactor."

It should .also be pointed out in onnection with the apparatus of 'Fig. l5-that the arrangementshown does'not necessarilypermit all the emitted electrons to follow orbits of uniform radius, It appears, however, that the-net effect is to establish a rotating and axially progressing space charge which produces high'freq'uency effects generally indistinguishable from those caused-by an electron stream whose form is more definitely fixed.

In the foregoing the invention (has been de-' scribed by reference to particular embodiments. It will .be understood, however, that numerous modifications" may be made by those skilled in the art without departing from the invention. I, therefore, aim in the appended claims to cover all such equivalentvariations as come withinthe true spirit and scope of the foregoing disclosure.

What I claim as new and desiretofs'ecure by i for producing a stream of orbitally moving elecacross the terminals of the output circuit. After its passage. through the electrode-- I45 the elec tron stream may be collected by means of an ap propriately positioned anode I56.

, It is desirable with the construction above described to prevent radially moving electrons from reaching the surface of the envelope I40 and thus producingobjectionable wall-charging. .To this end the electrodes .I42, I44 and I46 are provided with flanged extensions which overlap the inter electrode gaps and prevent egress of electrons by this means. Functionally similar flanges I58 are provided in connection with the gaps which exist betweenthe respective parts of the electrodes I43 and I45. I

It will be noted that in the construction of Fig. 15 the input and output gaps are in a common plane rather than being 90 degrees displaced as in the cases previously described. Thepossibility of this arrangement, which has been found satisfactory fora particular condition of operation, is explainedin part by the greater effect of space trons in which the center of orbital motion progresses along. a given axisea pair of concentric conducting cylinders arranged one;;within\ the other and defining between them 'an annular space to be traversedby the said electron stream, the said cylinders being respectively provided with elongated gaps contiguouswith a commonregion of the said annular space, said ps, extending parallel to .the said axis of progression of the electron stream, common means for; producing cyclically varying potential gradientsacross the said gaps so as to vary the orbital velocity of-the electrons which successively traverse the said region, and energy-abstracting meanspositioned to be affected by variations, existing in the electron stream at a point which is axially-displaced from thesaidregion.

.2. High frequency apparatus including means for producing a stream of orbitally moving elec trons in which the center of orbitalmotionprogresses along a given axis, a generally cylindrical conducting structuredefining a hollow chamber to 'be traversedlby the "electron stream, said structure having a pair of elongated openings therein which extend axially of the -men'iberat diametrically opposed region's thereof, elon gated conductive elements positioned insai'd openings but inv completely filling the .same so as to provide elongated gaps betweenfitheboundaries of the openlugs and the edges of'th'e' elements, means for impressing a high "frequency voltage between the elements and'the said cylindrical structure there :by to produce'variations in the orbital velocity 2,366,555 the electron stream at a region which is axially the potential gradients developed across the said gap, additional conducting parts defining a second elongated gap extending generally parallel to the first gap in a region which is axially displaced therefrom sufliciently to permit the velocity variationsof the beam to be effectively converted into charge density variations in the intervening space, said second gap being azimuthally displaced from the firstgap by a substantial angle less than 180 degrees at which said charge density variations are maximum, and means connected with the said additional conductingparts andadapted to be excited thereby in accordance with variations existing in the electron stream upon its traversal of the said second gap.

4. High frequency apparatus including means for producing a stream of orbitally moving electrons in which the center of orbital motion progresses along a given axis, means defining an elongated gap which extends generally parallel to said axis in proximity to the electron stream, means for producing cyclically reversible potential gradients across the said gap, thereby to produce variations in the orbital velocity of the various electrons asthey pass the said gap, means defining a second elongated gap extending generally parallel to the first gap in a region which is axially displaced therefrom by an amount sufficient to permit said velocity variations to be efiectively converted into charge density variations in the intervening space, said second gap being also azimuthally displaced from the first gap by an angle on the order of ninety degrees so that it coincides with a region of maximum charge density variation, and energy abstracting means arranged to be affected by the variations existing in the electron stream as it passes the said second gap.

5. High frequency apparatus including means for producing a stream of orbitally moving electrons in which the center of orbital movement progresses along a given axis, a pair of semicylindrical conductive parts which are cooperatively positioned to provide axially extending gaps between their juxtaposed edges in proximity to the electron stream, means for producing cyclically reversible potential gradients across the said gaps so as to vary the orbital velocity of the various electrons passing the gaps, a second pair of semi-cylindrical conductive parts which are also cooperatively positioned to provide axially extending gaps between their juxtaposed edges,

said last-named gaps being in proximity to the path of the electron stream and being both axially and azimuthally displaced from the first-named gaps, and energy-abstracting means arranged to be affected by the variations existing in the electron stream as it passes the said last-named gaps.

SIMON RAMO,

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