US2438709A - Thermionic tube having secondary electron emissive electrode with surface and form variations - Google Patents

Description

March 30, 1948. E. LABIN ET AL 2,438,709

THERMIONIC TUBE HAVING SECONDARY ELECTRON EMISSIVE ELECTRODE WITH SURFACE AND FORM VARIATIONS Filed Aug. 6, 1942 4 Sheets-Sheet 1 I I H I E FIG. 4-

M'HM'P INVENTORS -500mm)LAB1NMANU1JU110K0B1L5KY March 30, 1948. E. LABIN ET AL THERMIONIC TUBE HAV ING SECONDARY ELECTRON EMISSIV ELECTRODE WITH SURFACE AND FORM VARIATIONS Filed Aug. 6, 1942 4 Sheets-Sheet 2 INVENTOR.

ATTORIVEK March 30, 1948. E. LABIN ET AL 2,438,709 THERMIONIC TUBE HAVING SECONDARY ELECTRON EMISSIVE Y ELECTRODE WITH SURFACE AND FORM VARIATIONS Filed Aug. 6 1942 4 Sheets-Sheet 3 E5 ELECTRON BEAM ELECTRON 55AM l 28d g ;E

f zwUAPMABzmwAA/m Jz/z/ammm/ IN VEN TOR.

March 30, 1948. E. LABIN ET AL THERMIONIC TUBE HAV ING SECONDARY ELECTRON EMISSI ELECTRODE WITH SURFACE AND FORM VARIATIONS 4 sheets -sheet 4 Filed Aug; 6, 1942 mam/r005 0F //V/l/7 V01 7461 FIG. 20.

wow/mam f/WWUH JUZ/O mam/r) INVENTOR.

Patented Mar. 30, 1948 N-lTED STATES PATENT FFEQ THERMIONIC' TUBE HAVING SECONDARY ELECTRON. EIWISSIVE ELECTRODE WITH SURFACE AND- FORM VARIATIONS Edouard Labin and Manuel Julio Kcbilsky, BuenosAires, Argentina, assignors to Hartford National Bank and Trust Company, Hartford,

(301111., as trustee Application August 6, 1942, Serial No. 453,890-

8Claims.

l I The present invention refers to a noveltype of thermionic tube in which the transfer characteristic between the input and the output is shaped at will by means hereinafter called reroot, or thesine, and the like. Hence, the novel tube permits of the performance of all the operations of which a classical thermionic valve is capable, but, as will hereinafter appear, with much greater simplicity and perfection, as well as enabling other operations to be carried out which cannot be effected by classical valves or any combination thereof;

The present method uses electron beams of which the intensity and the path of-propagation' can be controlled in order to realize a desired effect.

Attempts have been made in the past to use this idea, but the embodiments hitherto based on it have been most frequently adaptations of. the common type of valve. The concentration was prepared by means of ordinary grids; that is to say, electrodes placed in the beam, by a, suitable adjustment of the tensions, and the electrons were collected on anodes which were alsov of the ordinary type. j

Indeed, most tubes of the prior art may be said to be merely improvements on the, classical valve, obtained by applying in varying degrees the principles of electronic optics.

'Thermionic tubes are also known in which a beam of electrons is produced near one endof the tube by means of an assembly generally referred to as'an electron gun, the beam being directed, towards the other end of the tubewhere a suitable target or anode is provided. Various kinds of motion have been impressed on such a beam by electrostatic and/or electromagnetic control means lccated'toprovide aboutthe path,

of the beam a suitably varying field. It has. also been proposed to provide specialtargets, as for instance, targets consisting of a plurality of elements adapted t be connected in a circuit external to the tube, in such a manner that the passage of the electron beam from one, element,-

2 diaphragm in the path of the cathode discharge at a point in the neighborhood of the target, particularly in connection with discharge tubes containing a rarified filling of a gas or a vapor.- Such diaphragms have been used, however, merely for the purposes of selecting a small fraction of a CiiSf charge of considerable cross sectional area, so that the target is struck by a highly limited bundle of rays. Evidently in such cases movement of the general discharge in a direction transversely of the direction of propagation, before the, general discharge reaches the diaphragm, will have substantially no eifect on the properties of the restricted beam passing through the diaphragm.

In contradistinction to the devices of the prior art, the novel thermionic tube of the present invention may be said to depend in addition to a more systematic application of the principles of electronic optics and of the idea of controlling propagation paths, on the novelty of introducing special response forming means whereby a tube is obtained which has entirely new and highly useful properties.

As hereinabove indicated, the novel thermionic tube of the present invention is adapted to produce an output which shall be any predetermined desired function of an electrical quantity Vimpressed on the device as a control factor, said tube consisting in an electron discharg device of the kind comprising a means for producing an electron beam of'desired cross section with control means in the path of the beam and non accelerating control means positioned in operative relationship with respect to said beam, said tube including on the side of said control means remote from said source and in the path of the beam, a response forming system the composition and geometry of which may be designed at will for causing under the influence of the Preceding controls, the magnitude of the current of electrons issuing from the response forming system to be proportional to said predetermined desired functiornsaid tube further includingan electrode, generally a passive electrode, disposed to collect the electrons issuing from the response forming system.

The idea to be stressed is that any arbitrary type of response function desired can be precise- 1y obtained by the mere adjustment of the chemico-geometric structure of the surface of solid bodies. Besides, the use of trajectory controlby fields which do not exchange energywith the beam'abolishes the finite charge which usual tubes present to their input circuits, and the possible use of a passive collector whose eventual variations of potential do not change the output current, will furnish a device with infinite internal resistance which abolishes the ordinary limitation of the supplied current by the output circuit.

These and other bjects and advantages of the present invention will become more clearly apparent in the course of the following description in which reference is had to the accompanying drawings.

In the drawings:

Fig. 1 is a diagram illustrating the principal operative portions of a thermionic tube according to the present invention.

Fig. 2 is a diagrammatic representation of one embodiment of the novel tube.

' Fig. 3 is a diagram illustrating another embodiment of the tube.

Fig. 4 is a diagram illustrating a tube combining the features of the response forming systems of the Figs. 2 and 3. v

Fig. 5' is a diagram illustrating the principle of'intensity control by electron optical methods.

Fig; 6 is a diagram illustrating the formation of the output by electron optical control of the beam.

Fig. 7 is a diagram representing the cross section of an electron beam in relationship with one type of response forming element.

Figs. 8 and 9 are graphs representing the characteristic curves of certain parts of the new tube.

Fig. 10 is a diagram illustrating how the geometry of the response forming system may be determined in a given case.

Fig. 11 is a diagram illustrating the operation of one type of response forming member.

Figs. 12 and 13 are graphs representing respectively the output current'characteristic, and the family of curves equivalent to the plate characteristic of an ordinary valve, as obtained from a tube of the present invention having a given response forming system.

Figs. 14 and 15 are diagrams illustrating the formation of sinusoidal functions by reflection.

Figs. 16 and 17 are diagrams illustrating the formation of sinusoidal functions by barrier.

Figs. 18 and 19 are diagrams illustrating alternative arrangements for obtaining squaretopped waves.

Fig. 20 is a diagram showing forming means adapted to the detection of amplitude modulation.

Figs. 21 and 22 are diagrams illustrating the formation of saw-tooth outputs.

Fig. 23 is a perspective view of a modified response forming means adapted to give a sawtooth output.

Fig. 24 is a graph illustrating the output obtained by the means of Fig. 23, and

Figs. 25 and 26 are diagrams illustrating further modifications.

Referring first to Fig. 1, the novel tube comprises an envelope I 0 of glass enclosing a well evacuated space. At one end of the tube is suitably mounted a source of a stream of electrons, which may be of any well known type. For example, it may comprise an indirectly heated cathode l2, a heating filament M, an intensity control grid l6 and beam concentration means l8, so arranged that from said beam concentration means there issues a beam of electrons having a desired cross section. The tube likewise tube.

trating means I8 remote from the source I2, 14, and I6. Said deflecting means 20 is adapted to have impressed upon it a variable electrical quantity 1;, whereby the electron beam may be deflected either along the :c-axis or along the yaxis or in both said directions simultaneously, the axes of coordinates being shown in the figure with the z-axis extending longitudinally of the In other words, the beam of electrons is adapted to be deflected either height-wise or Width-wise of the tube or both height-wise and width-wise thereof;

On the side of the deflecting means 20 remote from the source, we provide a response forming system indicated by the general reference number 22, which is positioned in the path of the beam emerging from the control zone defined by said deflecting means. We further provide a target, or rather, a passive electrode 24, located so as to collect the electrons issuing from the forming system. v The response forming system itself, while always depending for its operation on its composition and geometery may be adapted to any actual constitution of the electron beam and, may be embodied in one of two principal ways or as a combination of such principal ways. It may, for example, be embodied as a barrier having an opening adapted to be explored by the electron beam moving in response to variations in the controlling quantity 0, so that the cross sectional area of the beam which passes beyond the barrier, that is the amount of output current, shall vary in accordance with the shape of the opening.

Alternatively, we may use as a response forming member, a surface having secondary emission properties of such a nature that when the surface is explored by the beam moving in response to the controlling quantity '0, the secondary emission shall vary in accordance with the chemico-geometrical structure of the surface at the point of incidence.

Obviously we may combine these two types of response forming members and may shape the beam by means of a barrier before allowing it to impinge on the secondary emission surface.

As will be clear from the above general indications, and as will hereinafter be explained in detail, the response forming system may be designed so that the composition of the members thereof is neutral or inoperative for the purposes of forming and only the geometry of said members constitutes the forming factor. The system may also be designed so that the chemical composition of said members, e. g. as secondary emission surfaces, is the forming factor the geometry of the surfaces being so chosen as to be non-contributive at all points thereof. Furthermore, between these broad limits any combination in which both the geometry and the chemical composition of the members enter as forming factors to a greater or less extent, may be utilized.

The beam may move across the response forming member as a whole or the beam may be expanded and contracted transversely of its direction of propagation to secure variation of the intensity modified bythe geometry and/or composition of the forming member. Both these methods of securing the formation of the response characteristic are in the present specification to be understood as included in the term exploration. Also it should be noted that the term "non-accelerating? as applied to: the: conetrolmeans relates= to acceleration: in:: thB"dilZCT- tion ofpropagation of the beam as a:- wholeso that some transverse acceleration mayibepresent.

From: the foregoing general description it, will readily'be seen that the novel: tube is; susceptible in operation of a large number of. adjustments armlicontrol's;v which may be' summarized as'follower (a) Control; called"electric; of the intensity of the current in the beamby the tension applied to'the grid:

(11) Control, called geometric, of'the displacementsof the beam by one or more tensions or'currents applied to the deflection means.

() Control, called opticf of'the width of" the Cross-section of the beam by one or more tensions. applied to the concentration means. 7

(d) Control? of the sensitivityof the deviation means by one or more tensions appliedto the concentration means.

(e) Adjustment of the law which relates the deflection with the deflecting signals by thedesign of! the deflecting means and deflecting chamber.

(f) Adjust'mentof' the law which relates the deflection with the response by the design of the interposed response forming means, the latter being of the general type of openedbarrier, or reflecting. surface, or a. combination of. the two.-

fields in quadrature with the beam, and oi theshaping: of the output by means of geometrical response forming systems, establishes a general basis for the construction and design of tubes adapted to give a predetermined result or type of operation; without the necessity of inventing a suitable tube for each several application. As WillbB seen below, the responseforming system may readily be designed for any type of desiredfunctional relationship between the output and the controlling quantity.

Certain embodiments; and applications of the novel tube Will now be described and for simplicity the majority of these embodiments will be: described in terms of one or other design of responseforming elements, but it i's to be understood that, ingeneral, alternative designs may be .used with equal facility for the same purpose. Thus a. barrier with a specific opening may be replaced-by orcombined. with a secondary emisemu-surface of a specific chemico-geometrical structure; and vic versa. All such alternatives areheld to lie within thescope of the present invention.

In Fig. 2, we have shown an embodiment of thetube in which the response forming system is of the barrier type. In this embodiment the grid [6a and beam concentrating means are shown. adapted.v to produce a beam of circular crosssection, but: it should be clearly unlea derstoodi that: any: other suitable: cross section. Ofi electron" beams may: be employed. The; forms-- ing; system 22a: consists of? ai plate=26rhavihg5an aperture 23 formed therein; the piat'ezbeingsoarranged that thea'aperture: is disposed-iinrthe' path, of the" beambetween the 1 deflecting? elec trodes Zea-- and; the passive: collectonelctrodei are; The gap or aperture? varies iIf..Width 'r height wise" of: the tube, .and'the-v control: electrodes; 211a are adapted to: deflect thebeamaheightewisa or: along'thezc-axis. It? is1obvious from. the figure. that 1 as the" beam. is caused-to explore the apers turc 283the'section ofthe beam'rpassingsthrou'gh said. aperture and: therefore adapted to be re ceived'by the collector 24a; varies: in}; response"- to the: varying: deflection: of the beam;

It will be clear to those skilled in the artth'at: more" accurate or well defined? results willi'b'e =obtainedif a beam= isus'edl having a substantially rectan'gularcross section: orwidth iargecomparedr with its heiglit Such a heamimay'conveniently' betermedlaminiformandmay-lbe obtamedieither by electron-optical; means or 1 else by periodically. displacing a circular section beamrwidtht-wise of the tube. The pri'nciples of the electrons-optical methods for: obtaining. laminirornrbeams-have 7 already been describedirr the literature OffthB art and are held to require no further explanation here; The method of periodical." displace ment is subject to-the limitation thatthefrequency of width-wise displacement must be greater' than the highest frequency ofthe'varias tion of the controlling quantity 2:.

Fig. 3 shows diagrammatically a tube accord;- ing to the present inventi onn-in; which the rssponseforming system 22b is constituted by sec ond'ary emission surface 30 located -in the pathi of the beam' emerging from be'tween the control or deflecting members: 2%: The beam is pres pared, asbe'fore, from the elcc'tronsissuingt'from. the cathode i2, by means of s: grid lfib and-cone centrating means I; and may. be-ofi any: desired cross section. In the present instance avery fine circular cross sectionbeami's-vquite suitable=. passive electrode 2% is located so: as toi. collect the secondary electrodes emitted by the surface 30'; and will therefore generally be to one sid'e'of the tube rather than at its end;

The secondary emission is, as is. welliiknowmaar function of' the angle 9', which the'beamfmakes with the normal s to the surface at the point? of impact; Actually, the secondary- 8miSi0n1.a1SO depends to some extent on the: velocity: of'the; primary electrons, but-at the: present timeiiti i's quite: feasible to" prepare" secondary emissive sur faces such that the influence of:thevelocity v of the primary elections shall 'be withirra wide range a negligible factor.

S'till referring to Fig; 3-; it will readily be appre ciated that the geometric control", orformation:

of the output, isobtained by f causing" the! .beam' to explore the surface 35. For every positiomof the beam correspondingto a value'veofithecontrol quantity, there is an angle of incidence (ring thestube. thebeamv willbe deflectediialsosim i only one: direction, say heig-ht-wiseoftthetubez It is however possible, and sometimes desirable, to providea secondary emission surface the inclination or constitution of which varies along both the a: and the y-axes, in which event additionaldeflection will be provided in order to enable the beam to be deflected simultaneously width-wise and height-wise of the tube so as to explore the whole of the surface.

Fig. 4 shows a combination of the construction of the response forming systems illustrated in Figs. 2 and 3. It will be noted that the barrier plate 260 with its aperture 280 is interposed in the path of the beam between the deflecting means 200 and the secondary emission surface 300, the passive electrode 240 being positioned with respect to said surface as in the .case of Fig. 3;

In Figs. 2, 3, and 4 the deflecting means has been shown as adapted to generate an electrostatic field, but it is clear that we may use electromagnetic or magnetic deflecting means, either alone or in combination with each other and/or with electrostatic means in any. of the many possible embodiments of the present invention.

. Instead of causing the beam as a whole to move over the aperture in a barrier member, we may produce what may be termed a transverse pulsation of the beam, by making use of electronoptical principles. In Fig. 5 is shown a diaphragm D having an opening 0. If the beam, indicated by the shading, is focused, the whole of it may be caused to pass through the opening 0. On the other hand, if it is defocused, or spread transversely, not only will the intensity per unit area of beam cross section be reduced, but the diaphragm D will allow only a selected portion of the beam to pass so that the intensity of the current carried by the issuing beam is also reduced. This provides an optical means of controlling the intensity of the beam which is allowed to pass on to the response forming elements, and is a method known in the art.

However, as shown in Fig. 6, we may combine this optical control with a response forming element in order to cause the beam as it pulsates to explore the forming aperture. As illustrated, the barrier 2621 has a double gap 281) and the beam is adapted to be focused so as normally to strike the barrier at the junction of the two parts of the gap and to be of such cross-sectional area as to be substantially completely stopped by the barrier. of the beam increases as indicated by the broken concentric circles, so that the expanding beam sweeps over the aperture and simultaneously its intensity is reduced. The function of the shaped gap is therefore to produce the formation of the desired function in combination with the variation in intensity by superimposing the factor represented by the shape of the gap which allows more or less of an intensity modified beam to pass in accordance with the results desired.

The manner in which the composition and geometry of the response forming system may be designed for any given case will now be discussed. The law of the shape of the forming means, i. e. the law which has to be defined, will be, for the tube of Fig. 2, that of the variation of the width y of the aperture as a function of the height-wise displacement, that is to say of a function of :12.

It is possible to control the coeflicient of secondary emission not only by the relative inclination of beam and reflector, but by the variation of the chemical structure of the emissive layer.

On defocusing, the cross-sectional area This layer will then be prepared by more or less fine strips of selected alloys progressively changed to present any predetermined succession of values of secondary emissive force. This type of reflector can be referred to as structural in contradistinction to that based on the change of the angle of incidence, which can be referred to as stereotonic. However, since all the methods of utilization are identical for these two types of reflector, the convenient simplification will be made of speaking only of the stereotonic one and of using the same words for the two. For example, the term shaping will be used indifferently to include a forming of the shape of the reflector or a chemical deposit on or treatment of an unformed body or an aggregate of selected alloys or any combination of these methods of controlling the coefficient of secondary emission.

Naturally, the reflector can utilize a combination of structural and stereotonic shaping.

For the tube of Fig. 3 the law will be that of the variation of the angle of incidence as a function of the displacement of the beam either width-wise or height-wise, or both, that is to say as a function of y or of :c or of a: and y simultaneously. For the tube of Fig. 3 but with a structural reflector instead of a stereotonic one, the law will be directly that of variation of the coeflicient of secondary emission with the displacement along the surface. For the combined type of Fig. 4, the law will be the combination of the law for Fig. 2 and of the angle of incidence as a function of the height-wise displacement y.

In any given practical case the data include the function relating the output current of the tube with the electrical quantity applied to the deflecting means. This, of course, is the function it is desired to produce. On the other hand, a given deflection characteristic is chosen, that is to say, the function relating the coordinates of the position of the beam with the electrical quantity applied.

The actual designing of the tube will therefore differ slightly according to which type of tube it is desired to construct. For a tube of the type of Fig. 2, it is necessary to know a quantity which will hereinafter be called the current characteristic of the beam, or more briefly, the characteristic of the beam. In the case of Fig. 3, the quantity that must be known is the characteristic of reflection of the electron emissive surface, or more shortly, the reflection characteristic.

The definition of the term characteristic of the beam is best understood by reference to Fig. 7, which shows a cross section of a beam which is supposed to be circular. If now the beam is obstructed by a plate 32 having a slot 34 of width 2y, which is varied, and the current passing be measured, a characteristic curve may be drawn relating said current to the half width y of the aperture M. This curve is the one which has been termed above the characteristic of the beam.

It is obvious that the form of the beam characteristic depends on the form of the cross section of the beam and also on the distribution of intensity at the several points of the section. For example, if the cross section of the beam is a very narrow and relatively wide rectangle, and the distribution is uniform, the characteristic will be a straight line.

For other forms of beam cross section, the characteristic will be a curve which may be determined by theory or by experiment, and has the following properties: (a) It has no negative values; (b) it passes through zero; (0) its maxivalue ls 'olotaineiwhe" is the halffwi'dth" of the cros l H In general the shaije or the urve Will bellikef that shovvii in'FiQ S; wherein-is th maximum current arned by; the heanir M 5- The reflection characteristic of the? type of valve illustrated= i11 Fig: 33" gives the secondary emission o-btainetl from a' surface as a function of the angle of incidence.- By femis'sion" ish'ref to he understood the} coeificient h'ivliich gives 1-0 that is at so -calleci tangent incidence. minimum and maximum' values of; the current prorfluced' depend. on the material composing the" reflecting surface. In certain cases; of sen iconductive materials; bm=O, but then b viis small.

With the structural type of reflector it will; he

easier to get a reflection characteristic which reaches zero.

When either the beam characteristic 01: the characteristic of reflection as well as the deflec tion characteristic is known the shape of; the; aperture or the contour of the surface require cl for each application may readily' beidete-rinined The method of determinationis illustrateq 1n F 7} 1 (in which the -1 9 1 51 exiaisf u e as i p r 1? p din t "Wh i e fi l tube is of the type oi Fig, 2 or Fig, 3. ,In quadrant I the function itis desired to form with thetuhe s1 graphed, and thi function has beensh r in the: form i/iM=f(v/1;u) wh er e vq'fis a certain value of reference for the geometrical coiitrol: niagfi i The characteristic of deflection i/A ='A (b where A is a certainvalue of reference for the dis"- placement, is shown in quadrant II. In the'eir ample illustrated the characteristic :c/A=A(1)/v'a) has been supposed a straight line, but when ad visable its shape maybe altere'tl'by a suitable arrangement'of'the deflecting devices. o

The characteristic i./i1'v1=H'(1i /B) of the beain; or the characteristic'i/z'm Gw) of refiect'ionis drawn in quadrant III. V

The required shape'of the aperture,

y/B=S('31':/A)

or the law connectingthe' ahgle ofinciden'cewith the coordinate x, 0 2( :c/A) is constructed point 60' by point in the following manner. Any point Mr is taken on the curve of"quadrant I and from it lines are drawn parallel to the axes to cut the; curves in quadrants II and III at points Mn and.

Mm respectively, froxn which parallels are drawn to MIMIII and MIMII respectively tocut each other at MIv which will be a pointon'the requiredcurve. In the case of a tube'of the type of Fig.3, this method Only' gives the equation of incidence 0:2(2c/A), but from" this equation the surface 70' contour can be deduced bynfiethods'well known'i-n" elementary geometry. For -a tube offthe type shown in Fig; 4, quadrantI will contain not a single curve, but a familyof curves since the dc sired function wouldthen-be of the-type of two 7 seesaw reflect'i'iig'= stir-face )f may he design' out ut current if as function of th geo'fiiet control vqitaeeiv; shan nee straight 1i ample,==let aF-tube'withcompound re'sp I ing' ele'rhehts s shown in Fig? 4fbe" considered for snap-Hairy; sim'p'cis"e the" surface 30b to plane anilfltheharn to be 'lainihiforin; It is ea be such tbat the" beam willlbe on'the hendxofitha curve, inbtherwords, hardlyprojecting into the V shape; gap or into :the' responsivezone' of the ire? fiectorp In this-form, we; also have an idea-Lida}.- tec'tor' which cloes not consume energy: from 'the' source'to which'it is connected V.

As regards orders of magnitude there is;no d iffi;-j culty eithen In current practicejinconnection with-beams;intelevisiomtubes; intensities of apfi prox-ir'natelyd-maf ar'ementioned. Tubes are also known havin'g aidefiection sensitivity of 5 mm; per "VOlfiZ On thi's 'ba'sis', if j theheight of the V shape" ga'p or of the reflector is assumedmo be 1; cmii' 'th'e rstrai'glit "portion of the, transfer chaf acteristic will alreadyhave a gradient: or slop'eof 0J5"-ma:i/vl,-'onthesuppcsition 'that?therflecting. surface *has no 'niultiplying'efiects Ifa imul tiplicatiofioffivetimes'iyassumed for saidos'ur face, the s1oie weum "be? 255" ma;/v'. J In'fthe": reflector-"tyne of tubesuch' mam-mismanagemherentr present? The tube of the present invention may also be used as a converter. If in an amplifying tube the current is controlled not only by the geometric control 12, but also by the electrical control it, the output current would be strictly proportional to the product vu, provided that the excursion of 'u. remains within the linear zone of the electrical control. If v is made the tension of a local oscillator of frequency f1, and u that of the signal of frequency is, in the output current there will be terms of frequency of fi-fs or ,f1+].-., which may be taken as intermediate frequencies in a classical superheterodyne.

Should there be any dificulty with respect to a want of linearity of the electrical control, a tube can be used with response forming means of the reflector type, the forming surface being so shaped that two independent geometric tension controls applied simultaneously to heightwise and widthwise deflecting means respectively, will cause the output current to be exactly proportional to the product c1112. Thus the tube provides a high signal level converter, without whistlings, interferences and deformations.

Other applications can immediately be found for the multiplying tubes as for example, as watt amplitude modulators meters, phase meters, and the like, but in the case of the tube of the present invention, such applications are effected with greater perfection, precisely because of the greater perfection of the multiplying properties of the tube.

It will be appreciated from the foregoing that one of the principal operative control factors in the novel tube is represented by electrodes lying outside the beam and by fields in quadrature with the beam, or by the optical focusing means, all of which do not accelerate but only deflect the electrons, or vary the cross-section of the beam. Consequently, the impedance of the control element becomes practically infinite.

The following illustrative examples of Various applications will make this clear.

The principles of the present invention may be utilized to provide a highly satisfactory R. M. S. voltmeter having a substantially linear scale, since said principles readily permit of the construction of one tube having a characteristic of the form i=kv and of another having a characteristic of the form i=lcVv, which two tubes may be used in combination to give a voltmeter of the type stated. In the first, or squaring tube, the mean value of the squares of the voltage 12 will be obtained. This mean value would itself already be proportional to the effective value of 1), but a voltmeter constructed with this tube alone would have a parabolic scale. If the ouput of the squaring tube is passed through the other or root extractor tube, a final output will be obtained which is proportional to the effective voltage, so that a linear law scale is achieved.

Tubes according to the present invention may also be constructed to give outputs following a sinusoidal law. Figs. 14 and 15 show two types of surfaces of secondary emission suitable for the production of an output proportional to the sine or cosine of a given angle, and Figs. 16 and 17 illustrate two types of apertures designed to give similar results in tubes of the type of Fig. 2. In each of these four figures, the electron beam EB is adapted to move widthwise of the paper in exploring the response forming member. This finds application in frequency modulation.

Another highly useful purpose to which the tubes of the present invention may be applied is secret transmission. The use of the tube as a classical amplitude modulator has already been explained hereinabove. Such a modulator gives the product of the carrier wave e=E sin wt and the function of formation 18(2)) =A+Bv which is exactly linear as a function of the geometrical control quantity '0 which reproduces the intelligence. If, as in the case of secret transmission, it is desired to modulate purposely without fidelity, it suffices to take for 8(0), where u is still the intelligence, any function which has purposely been made peculiar and complex by means of a response forming system of irregular properties. The wave E B(v) sin wt sent through the ether, then carries a completely deformed modulation, and if it is detected, a tension u=p(v) will be obtained in which nothing of the intelligence will be recognisable. stored by a listener aware of the law 5(1)) of the response forming system of the transmitter. Such listener will apply the detected tension u to the geometrical control means of a tube, the response forming system of which shall have properties of deformation exactly opposed to those of the forming system of the transmission tube, that is to say, a forming system which shall give the response law 1 :18 (u), where B is the inverse function, in the mathematical sense, of the function p. Thus at the output of the reception tube the tension will be v=p'[5(v) 157). In this manner, a secret transmission can be established by constructing two tubes with response forming systems having any arbitrary and irregular characteristics, and inverse to one another, in the sense of the inverse functions of analysis. The method is of the greatest possible simplicity and does not require circuits or adjustments. It is almost infinitely flexible, since, for example, in the barrier type of tube, two or three strokes of a file applied to the gap defining edges are sufficient to constitute a secret channel. The efficacy of the protection (secrecy) afforded, is practically complete, since the only manner inwhich the deformed intelligence can be restored is by using a receiving tube with a response forming system properly designed to be the counterpart of the transmission forming system.

The widening of the spectral band occupied by the modulation consequent on the deformation is not a serious obstacle, since secret transmission is generally applied only for spoken communications the spectrum proper to which is in itself narrow, and to short waves where the absolute range of frequencies available for each transmitter is great.

In Figs. 18 and 19 are shown alternative ways of obtaining square topped waves by means of tubes of the present invention. In the secondary emission type of tube shown in Fig. 18, the emissive member 38d is shaped so that the angle of incidence shall be constant, and in the barrier type of tube, the aperture 28d is made of constant width. The operation of such tubes, which can readily be understood from Figs. 18 and 19, will be briefly described for simplicity with reference only to Fig. 19. If the position of rest of the beam, that is, its position when the geometrical control quantity 0:0, is adjusted so that it falls just below the line a-a, at the bottom of the aperture, then for the values of the alternating quantity applied to the geometrical control means which cause the beam to move upwards, or to oscillate within the aperture, there will be a constant output U. For those values which deflect the beam below the line w-a, the output will be The intelligence can only be reradii on the surface Stir.

type e1=E(t) sin [(t)l, where the amplitude E may vary with the time as well as the'argument 4), provided thatthe corresponding instantaneous frequency w=d/dt does not go beyond a limited band. If m is fixed, =wt, and we have a wave of pure amplitude modulation. If w includes a fixed portion and a variable portion, the wave is one which issues from a frequency responsive circuit to which a frequency modulated wave has been applied. In all practical cases, the complementary signal e2=E(t) cos [(t)] can be obtained by known means. If these two signals e1, e2, are used as geometrical control magnitudes in a suitable deviation chamber, and they be supposed substantially sinusoidal, it is readily possible to produce a conical deviation of the beam, and the trace thereof on a screen will be a circle the radius vector R of which will be proportional tothe common amplitude Ed) at the complementary signals 61, and eat. If such a beam is allowed to fall on a response forming system of the secondary emission-type including a, surface 3dr which is a surface of revolution about the axis of the tube, as the amplitude E?) of the incident signal varies, the beam will describe circles P, P, of varying It is always possible to define immediately, by applying the general methods discussed hereinabove, a shape for the surface such that the response shall be proportional to the radius R, that is to E0!) Thus an accurate detection is obtained of the variation inscribed in the amplitude of the signal, by a process which does not require any time constant. The tube does not load the circuit to which it supplies the detected output. It should also be noted that it is not essential to adjust the conical deviation of the beam accurately. Any closed and sufficiently regular path will serve as a satisfactory basis for defining a response forming system of characteristics adapted to provide detection.

Another possible application of the novel tube is the production of saw-tooth voltages or waves. If the beam is given a circular deviation of frequency a, and it is allowed to fall on a strip separated into two portions tile and 39'e as shown in Fig. 21, and havingits surface prepared so that the secondary emission shall increase linearly as the electronic spot moves from'A to B, a steadily rising output will be generated until the spot reaches the gap G, when the output is suddenly reduced to nothing, whereupon a, similarly growing output is again established as the spot continues to move from B to A. If the currents generated by the two strips in opposition are collected, it will be seen that a saw-tooth Wave of frequency 2 is generated, as shown in Fig. 22, where the points marked M indicate the maximum values at the ends B, B of the respective strips, of the output. As in all the applications of the novel tube, the accuracy of the output function obtained does not depend on non-linear electronic phenomena, but on the accuracy with which the response forming system is constructed and onthe fineness of the spot. I-Ience"straightline increases AM and vertical drops M-B in the output can be obtained with much greater 14 accuracy than inordinarycircuitsgand thissholds for any frequency forwhich it isiknown howto prepare circular 'paths'for the beam, that is to say, for frequencies much beyond the values hitherto used. The frequency of the teeth may be made other multiples of to than 20:, by suitably sub-dividing the strip into 12 equal parts where 11 2. It should be added that the .tensio'nwhich can be obtained with an output resistance of some tens of thousands of ohms is easily some tens of volts.

The saw-tooth waves may "also be generated 'With the barrier type of tube, as illustrated in Figs. 23 and 24. For this purpose a laminiform beam will be used, as obtained by optical methods, and it will be caused to rotate in an approximately circular-path-so as to explore successivelya pair of curved apertures 28:: and 28'e, whichincrease in width gradually in the direction 'of-rotati'on of thebeam. These apertures extend over diametrically oppositelarc s of so that while' the beam is passing over the interveningarcsthere will be no output, and the general result will be asshown by the full-line curve'in Fig.524. :To obtain a continuous saw-tooth wave, it isnece'ss sary' to provide asecond tubewiththeobeam .and

the apertures 28f, 28' displaced 90-with respect to'the arrangement just described, so'that the second beam will produce'the' saw teeth shown in brokenlines inFig. 24. The two outputs are collected together to give the eompleteawaveby connecting the outputs of the two tubes in parallel.

The tube described with reference to Fig. 19 may also be used as a silencing tubeby applying the signal Us to the grid of theelectrical control and to the plates of the geometric control and adjusting the position of the rest of the beam-so that'it falls across the transverse center-line of the aperture. Then, so long as Us is such that the beamoscillates between opposite ends of the aperture the signal passes in the normal way to the output circuit. As soon as the amplitude of Us brings the beam beyond either of said ends, the output falls instantaneously to zero a'n'dremains zerofor the whole time the beam remains in this position, 3y reason of the integrating properties of the detectorsuch drops do not-p'roduce audible phenomena." K'nown art calls-for the use, for obtaining thiseffector a double am= plifier chain, one member of which is cut on when the peak tensions surpass acertain value. The novel tube ;may-also 'be-usedfor automat ically controlling-the output. With, for exa mple, a barrier type tube in which 'the aperture 2Bi1fiS as'shOWn in Fig. 25, output characteristics of the typesrepresented by the curvesd, e, *and -f, of Fig. 26 may readilybe obtained. Th'esignal is applied to the electrical control andtheam'p'litude of the signal is detected andappliedto the geometric control. The shape of'the aperture 2811 is such that as the geometric control tension 12 increases, the amplification between-the electric control and the output varies in inverse proportionality. Hence, by suitably adjusting the position of rest (when 12:0) of the beam to coin cide with the base 11-1) or to lie at a low'erlevel c-c (Fig, 25) then if the width of the beam be made slightly less than that of thebase of the aperture 28q,the curves :2 and e respectively will be obtained. If additionally the beam lee-made sensitivity control by applying the rectifiedv'olt age proportional to the amplitude to the geometric control members with a time constant which is large compared with the slowest modulation. In this manner it is possible to obtain simultaneously a. silencer between stations of adjustable threshold. If the time constant is small compared with the most rapid modulation then a demodulator is obtained which may be used as an amplitude limiter in frequency modulation receivers.

Although the present invention has been described with reference to certain embodiments illustrated in the drawings, it is to be understood that many modifications may be made in the construction and details of the tubes without departing from the spirit of the present invention, and all such modifications are held to lie within the scope of the appended claims.

We claim:

1. A thermionic tube having a response characteristic adapted to produce an output voltage proportional to a predetermined mathematical function of an electrical quantity impressed on the tube as a control factor, comprising a source of an electron beam, a non-accelerating control means positioned in operative relationship with respect to said beam for deflecting the said beam, a response forming system arranged remote from said source and in the path of the electron beam and comprising a secondary-electron emissive electrode having a geometrical configuration and surface variations producing in combination an emission response variable over the surface of the electrode and adapted to produce an issuing electronlc current variable in magnitude substantially proportional to the position of the point of impact of the electron beam on the surface of the electrode, and a collector electrode arranged adjacent to said response forming system and between the said source and the secondary-electron emissive electrode for collecting secondary emissive electrons from said emissive electrode to produce an output voltage substantially proportional to the said predetermined function of the said electrical quantity impressed as a control factor.

2. A thermionic tube having a response characteristic adapted to produce an output voltage proportional to a predetermined mathematical function of an electrical quantity impressed on the tube as a control factor, comprising a source of an electron beam, a non-accelerating control means positioned in operative relationship with respect to said beam for deflecting the said beam, 2. response forming system arranged remote from said source and in the path of the electron beam and comprising a secondary-electron emissive electrode having a geometrical configuration producing an emissive response variable over the surface of the electrode and having a graded secondary-emission characteristic, whereby the electrode is adapted to produce an issuing electronic current variable in magnitude substantially proportional to the position of the point of impact of the electron beam on the surface of the electrode, and a collector electrode arranged adjacent to said response forming system and between the said source and the secondary-electron emissive electrode for collecting secondary emissive electrons from said emissive electrode to produce an output voltage substantially proportional to the said predetermined function of the said electrical quantity impressed as a control factor.

3. A thermionic tube having a response characteristic adapted to produce an output voltage proportional to a predetermined mathematical function of an electrical quantity impressed on the tube as a control factor, comprising a source of an electron beam, a non-accelerating control means positioned in operative relationship with respect to said beam for deflecting the said beam, a response forming system arranged remote from said source and in the path of the electron beam and comprising a secondary-electron emissive electrode having a geometrical configuration and a graded secondary emission response characteristic producing an emission response variable over the surface of the electrode and adapted to produce an issuing electronic current variable in magnitude substantially proportional to the position of the point of impact of the electron beam onthe surface of the said electrode, and a collector electrode arranged adjacent to said response forming system and between said source and the said emissive electrode for collecting secondary emissive electrons from said emissive electrode to produce an output voltage substantiall proportional to the said predetermined function of the said electrical quantity impressed as a control factor.

4. A thermionic tube having a response characteristic adapted to produce an output voltage proportional to a predetermined mathematical function of an electrical quantity impressed on the tube as a control'factor, comprising a source of an electron beam, a non-accelerating control means positioned in operative relationship with respect to said beam for deflecting the said beam, 2. response forming system arranged remote from said source and comprising a secondaryelectron emissive electrode disposed in the path of said beam, said secondary emissive electrode having a geometrical configuration and a secondary emissive response characteristic producing in combination an emission response variable over the surface of the electrode and adapted to produce an issuing electronic current variable in magnitude substantially proportional to the position of the point of impact of the electron beam on the surface of the electrode, and a collector electrode arranged adjacent to said response forming system and between the said source and the secondary emissive electrode for collecting secondary emissive electrons from said emissive electrode to produce an output voltage substantially proportional to the said predetermined function of the said electrical quantity impressed as a control factor.

5. A thermionic tube having a response characteristic adapted to produce an output voltage having a substantially straight line characteristic as a function of an electrical quantity impressed on the tube as a control factor, comprising a source of a beam of electrons, non-accelerating electron beam deflector means, a secondary emission electrode of substantially parabolic profile arranged at a point remote from said source and in the path of said beam, the radius of curvature of said secondary emission electrode corresponding substantially to the plane of deflection of the beam in response to said electrical quantity impressed as a control factor, and a collector electrode arranged in the proximity of the secondary emissive electrode for collecting secondary electrons issuing from said secondary electrode on being struck by said beam.

6. A thermionic device for detecting amplitude modulation of an oscillating signal voltage without limitation imposed by time constants comprising, a source of an electron beam, two non-accelerating control means, one in quadrature with the other, arranged in succession in operative relationship with'respect to the beam for deflecting the said beam, one of said control means being adapted to have impressed on it said oscillating signal voltage and the other of said control means being adapted to have impressed on it a second oscillating signal volttage in hase quadrature with the first-mentioned signal voltage to thereby move the beam in a closed substantially regular path, a secondary emissive electrode in the form of a surface of revolution about the normal path of the beam corresponding to zero values of both said signal voltages and arranged on the side of the control means remote from said source, said secondary emissive electrode having a secondary emission response characteristic substantially proportional to the radius of the surface perpendicular to said normal path, and an electrode arranged in the proximity of the secondary emissive electrode for collecting electrons emitted by the said secondary emissive electrode on being struck by said beam, whereby the variable output from said electrode is made dependent only on and proportional to the amplitude variation of the said oscillating signal voltage.

'7. A thermionic tube, comprising a source of an electron beam 01' given cross-section, means to vary the cross-section of said beam in response to an electrical control quantity, a response forming system arranged on the side of said cross-section controlling means remote from said source and comprising a secondary emissive electrode positioned in the path of said beam, said secondary emissive electrode having a geometrical configuration and a secondary emission response characteristic adapted to vary in combination, the magnitude of the issuing electronic current substantially proportional to a predetermined mathematical function of the cross-section of said electron beam, and a collector electrode arranged adjacent to the secondary emissive electrode to collect the secondary electrons issuing from said secondary emissive electrode.

8. A thermionic device for producing a sawtooth voltage, comprising a source of a beam of electrons, non-accelerating control means positioned in operative relationship with respect to said beam and adapted to rotate said beam in a closed substantially regular path, a plurality of secondary emission electrodes arranged in the path of said beam on the side of the control means remote from said source, each of said secondary emissive electrodes extending over a substantially equal segment of the path of the electron beam and each having a secondary emission response characteristic linearly increasing between a minimum and a maximum value, said segments being disposed around said path with the maximum emission end of one segment adjacent the minimum emission end of the next segment, and an electrode arranged to collect electrons emitted by said segments on being explored by said beam.

EDOUARD LABIN.

MANUEL JULIO KOBILSKY.

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

UNITED STATES PATENTS Number Name Date 1,719,756 Clay July 2, 1929 1,757,345 Strobel May 6, 1930 1,920,863 Hopkin, Jr. Aug. 1, 1933 1,998,465 Severy Apr. 23, 1935 2,003,775 Schlesinger June 4, 1935 2,069,441 Headrick Feb. 2, 1937 2,071,382 Balshley Feb. 23, 1937 2,083,204 Schlesinger June 8, 1937 2,103,645 Schlesinger Dec. 28, 1937 2,138,928 Klemperer Dec. 6, 1938 2,144,337 Koch Jan. 17, 1939 2,173,193 Zworykin Sept. 19, 1939 2,241,027 Bumstead May 6, 1941 2,247,350 Colberg July 1, 1941 2,257,795 Gray Oct. 7, 1941 2,293,417 Thompson Aug. 18, 1942 2,357,922 Ziebolz et al Sept. 12, 1944

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