US2808470A

US2808470A - Electron discharge device structures and circuitry therefor

Info

Publication number: US2808470A
Application number: US430614A
Authority: US
Inventors: Hansell Clarence Weston
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1954-05-18
Filing date: 1954-05-18
Publication date: 1957-10-01
Anticipated expiration: 1974-10-01

Description

0tl, 1957 c. w. HANSELL 2,808,470

ELECTRON DISCHARGE DEVICE STRUCTURES AND CIRCUITRY THEREFOR Filed May 18, 1954 2 Sheets-Sheet l I-: 2.,.' idg v INVENTOR.

- Clarfm'lflmellf BY g 1 Oct. 1, 1957 c. w. HANsELL ELECTRON DISCHARGE DVICE STRUCTURES AND, C IRCUITRY THEREFOR Filed May 18, 1954 2 Sheets-Sheet 2 INVENTOR. [laren/Yvzel United Sttes Patent@ M ELECTRON DISCHARGE DEVICESTRUCTURES Y AND CIRCUITRYTHEREFOR` Clarence -Weston.Hansell, Port Jefferson, N; Y.,.as signor to Radio Corporationof America,-a corporation of Delaware Application May 18, 1954, Serial N0..430,614

The terminal years of the term 0i the patent to be v granted hasbeen disclaimed 5 Claims. (Cl. 179-171) The invention is relatedto electron:disehargeelectric wave translating systems and itparticularly pertains, to improving the power conversioneiciency ofl class: A .and class Bfproportional` amplitude amplifier circuit,-arrange-` ments.

Electron discharge devices are used for converting direct current power to high frequency alternating current power in radio and industrialrelectiic circuit arrange-` ments. Av particular example ofV such circuitry is Yfound in radio transmitters wherein a relatively lowpower.- alter-` nating current signal is applied toan electron discharge device circuit in order to-reproduce the signal; at -atrelaj-L tivelyhigh power level.

The prior art amplifier circuit arrangements are limited torelatively low power-conversion eflicienciesbecause,- the electron discharge devices available for the. purpose, are so constructed that electron currents of substantialvalues must ow at times of relatively highanode-,to-cathode potential. A typical case of a low-elciency, class A, audio frequency amplifier is that of the modulator tube inthe Heising amplitude modulationsystem. Ina Heiss. ingmodulatortube, anode current tlows, in lthe absence of modulation, in an amount somewhat greater than half the peak values of current during 100% modulation. This results in a very large average power loss inthe tube as compared with what might be called the useful output power.

In class B amplifiers as now generally used inthe art, for proportional amplication of either audio or radio frequency power, the power conversion eiiciency is rela? tively low also because electron-currents flow between ythe cathode and anode electrodes when theinstantaneous potential between the cathode and anode is relatively` large. The instantaneous value of power loss is equalto the product of the instantaneous potential and current and at low signal amplitudes the potential is very nearly equal to the D. C. power supply potential so that nearly all of the D. C. input power is lost in the electron discharge devices, appearing as heat at the anodes.

As the input signal amplitude increases from zero theV power conversion eiciency increases from,zero up to some maximum value less than 100% at maximum signal amplitude. Because of the necessity to preserve lin? earity or proportionality between the output and input current amplitudes, and the tendency to lose this proportionality at the higher amplitudes, the peaklinstantaneous conversion eciency seldom exceeds 70% and generally is considerably less. The average conversion efficiency is therefore generally low. Such low eilciency conditions exist in single sideband radio transmitters where single sideband currents are produced at low power levels and are then amplified in linear, or proportional, class B ampliiers.

The losses are higher for class B amplifiers operated at variable power levels than they are in class C ampliers operated.l at a constant high power level-because inthe former currents must ilow in the tube -while -interelectrode petentialsare high, whereas in class C'ampliers-current 2,808,470 '.'Patenfed Oct. 1g

ice

a. ows `onlyI :when the; interelectrode potentialsvr areV irelatively low. In the class C casethevr counter potentials which-.limit thecurrentpulses-y are mostly across the oscillating-toutput: circuit, Vwhereas =in iclass 'B amplifiers much less counter;voltage` appears across; theoutput circuit, on the. average-,.and much more across ,thelelectron discharge device.1` i Y f i This low power vconversion` eticiency` is. particularly objectionable .-'inlinear ampliters f of 4`radio transmitters whichamplify.v ampltudejmodulated carrier waves.A I n -this-pcase, where-'the carrier level is setv atfor nearathe center` of`A the `linear amplitude rangeof the amplifier, the average power@ conversion eiciencyfor -either the a une modulated. carrier Ycondition,,V or-.during modulation,.may be.. on theorderpoff 30% vto 40%.' 'For thisireason, the use of linear amplifiers in an amplitudemodulatedtran'smitten-is.` so, vdisadvantageou-sy .that the use ,has not been at alluniversa'l but-has `beenquite infrequent; Y Because ofthesehigh'losses some 'rather' complicated ,circuitry 4has :been -used.inbroadcast and communications transmitters. .employing y high level modulation powerrfin an ,etlorttQreduce-the losses and-increase'the powerjcon version Aelciency.. Theproblem, of` course-,is Vpresent 1 not onlydn telegraph andftelephone radio1 transmittersbut alsoin, transmitters to handle .facsimile-orpicturetrans? mission, telemeteringtelevisicngandthe like.;

An ,object` ofv the: inventionis 2 tol provide means for reducingtthe` power losses in,electricwave.translatinggsys tems iuvolvingelectron discharge devices in which elec'-A tronY current. of. substantial value., must llowat, timesy of relatively high.anode-xtofcathodey potential.,

Another- ,object 0f. theinvention is..to l provide an imi` proved electronv discharge amplifier circuit arrangement with relatively high power conversioneicie-ncy. Y

It is a further object of theinvention -to inerease-the power conversion e'iciency of an electric wave translating system while Astill VVmaintaining a relatively. lsimple `electron discharge` structure and associated circuit arrangement..

A more specific `object-.of theinventiomis to reduce power losses of electron discharge `devices ,during Vthe-conf dition of signal amplitudes,substantially.v less` than-the maximum amplitude. Y

The objects of the invention are obtained inanelec1 tric wave translating system wherein the, power losses ina high vacuum electron ydischargedevice are. minimized. at all points on the A. C. grid potential-A. C. anode ploten-` tial cycle by. arranging and energizing thetubestructure sothat the. electrons varealways.collected on electrode elements of relatively low. potential. The electronemisa sion is made to pass thrQugh,or-go,by,-.all electrodeelef, ments of high potentiahto electroden elements of. low potential. The ,electron current is transferredtautomatically' from one electrodeelement or. electrodearea, to another as the potentials` of the `electrode. elements or areas vary in response to the currentsdevelopedinthe, amplifier outputcircuits.A This `electron, current transfer from one element or area .to another causesthe electrons, to be collected with lower power `loss at, the electron co1; lecting electrode element kor area. The electronsz-are always collected yon electrode, elements or areasv of.Y rela,-^ tively low positive potential, whereby the instantaneous losses can never belarge.

The principles of the inventionmay be-appliedin seva eral distinct forms, allofthe Yforms relavtillgio, anfelectric wave translatingpsystem including au electron.discharge` device having meansto project abeam,A or beams,ofelectrons, means to modulate the beam, `vor beamsof`V electrons in intensity, and a multi-elementY electron .col-` lecting electrode structure having the elements thereof` arranged in cooperatingvrelationship with'respect toeach otherand tothetrajectory ofthe beam-, orr beamsLpf electrons in: accordance "witlrtlie-ir1vei1tioi1.Y 'Iheindividual elements of the multi-element electron collecting electrode structure have different potentials maintained thereon at any given instant and the elements of the electron collecting electrode structure are coupled toa common output circuit.: Y Y Y In one form of the invention power loss is reduced by employing a plurality of sources of D. C. power of different potential levelsV applied to different electron collectrng electrode elements of a plural-element-structure. 'I'he electron beam is projected toward the electrode of lowest direct potential in the absence of input signal and as the signal amplitude increases the electron 'current from the cathode device automatically transfers from the one electron collecting electrode to'one of increasingly higher direct potential so that the electronsv are' collected with lower average power. loss, thereby increasing the average power conversion etiiciency Without limiting the nal peak value. of power which can be obtained by use of the highest D. C. potential.

In another form of the invention the electron collecting electrode structure itself forms a substantial part or the whole of one of the reactance elements of the output circuit -so that different instantaneous potentials exist along the' multi-element electron collecting electrode structure. Electron collection is then limited automatically to portions of the electron collecting electrode structure having a relatively low instantaneous positive potential with respect to the electron emitting cathode device so that power loss is relatively lovv at all current amplitudes.

There are two general variations iny which the latter formof the invention may be constructed. One variation, which is best suited to use of very high radio frequencies, utilizes a multi-turn coil as the multi-element electron collecting `electrode structure, and the other, which is better adapted to use at 'lower radio frequencies, utilizes a plurality of electron collecting electrode elements which are operated at different A. C. potentials and, if desired, also at different D. C. potentials. With the first variation external capacity is used in conjunction therewith to form a circuit parallel resonant at the desired operating frequency. In the second form an external inductance element is used in conjunction with the interelectrode capacity and usually also an external capacity to form a parallel resonant circuit at the desired output frequency. The plurality of electron collecting elements are connected to different points along the external inductance. Obviously, an electron collecting electrode structure having both internal and external inductive and capacitive reactance components might be used.

In order that the invention may be more clearly understood and readily put to practical use, a detailed description thereof of several embodiments, given by way of example only, is given with reference to the accompanying drawings forming a part of the specification and in which: Fig. l is a schematic diagram of a` tube and circuit arrangement, suitable for amplifying relatively low frequencies, constituting a wave translating system according to one form of the invention;

Fig. 2 is a cross-sectional viewof an electron discharge device having an electron collecting electrode structure according to the invention;

Figs. 3 and 4 are cross-sectional views of another electron discharge device according to the invention;

Fig. 5 is a schematic diagram of a Wave translating system incorporating an electron discharge device of the type shown in Figs. 3 Vand 4;

Fig. 6 is a cross-sectional view of an electron discharge device having an inductive reactance type of electron collecting electrode structure according lto another form of the invention; 1 Eig. 7 is a shematic diagram-of an electric wave translating system according to the invention utilizing an elec-Y tron discharge device o f the' type illustrated in Fig. 6;

l Fig Yis across-,sectional view of another electron dise charge device according to another form of the invention; and

Fig. 9 is a schematic diagram of an electric wave translating system utilizing an electron discharge device of the type shown in Fig. 8.

It should be understood that in none of these drawings has any attempt been made to draw the tubes and circuits to scale. They are intended only to convey the invention to others skilled in the art who will understand the importance of detailed dimensions upon tube characteristics and be able to design tubes on the basis of calculations and experiment according to the usual practice.

Referring to Fig. l,V there is shown one form of electric wave translating system according to the invention in which an electron discharge device 20 of the high vacuum type has an electron emissive cathode electrode device 21, a cathode shield member 23, and a beam forming electrode 25 having an aperture 26 therein.

Electrodes

21, 23, and 25 are all arranged in an electron fgun structure for projecting a large diameter, high current beam of electrons. The electron gun structure need not be of the type specifically disclosedpbut may be of any broad electron beam forming system known to the art, since the electron gun in and of itself does not form any part of the invention. A control electrode or grid 27 is preferably interposed between the cathode shield member 23 and the beam forming electrode 25 to modulate the intensity of the electron beam in accordance with signal intelligence impressed thereon by means, for example, of a transformer 29. The cathode shield member 23 is preferably maintained at cathode potential as shown, while the beam forming electrode 25 is made positive with respect to the cathode electrode and the grid 27 is biased negative With respect to the cathode in the absence of signal.

According to the invention, the broad beam of electrons emerging from the aperture 26 is impelled forward to impinge on an electron collecting electrode element or anode 33 forming one element of a plural-element electron collecting electrode structure. Another cylindrical electron collecting electrode element 35 is arranged in the electron discharge device 26 in such manner that in the absence of applied signal no electrons from the electron gun structure are collected on element 35. This other electron collecting electrode element 35 may be not only in the form of a short cylinder but also may, if desired, be in the form of dat plates forming a rectangular structure similarly placed. Such flat plate structures are more useful with electron beams which have essentially thick ribbonlike cross-sections. Preferably, the electron collecting electrode element 35 is mounted on a ring seal extending through the insulating tube envelope and the electrode 33 may be similarly mounted on half of a similar ring seal, to facilitate electrode cooling.

Referring to Fig. 2, there is a suggested example of a practical embodiment of the electron discharge device 20. A cathode device 21 and a cathode shield 23 are held in fixed relationship by means of a glass stem 37; the cathode device 21 being supported on lead-ins 38 and 39 which constitute the supports and the electric connections for the cathode device, and the heater (which is not shown) and at the same time the heater and cathode socket connecting pins. A glass press portion 41 supports a grid 27' which is electrically accessible on the exterior by means of a grid cap 27a. A beam forming electrode 25' is mounted atop the glass press portion 41. The edge of the beam forming electrode Z5 is electrically accessible from the exterior of the tube. As an alternative construction to the beam forming means shown, some conventional form of magnetic focusing arrangement might be used if desired.

The plural-element electron collecting electrode structure is formed in this case by the tubular anode electrode 33' and the tubular drift tube electrode 35 which are oined by,v glass or, ceramic envelope portions 43 and 45, the latter of whichjoins the drift tube 35=to the beam .forming electrode 25'. The external surfaces ofY the drift tube 35 and the anode-electrode 33 are exposed both for electric connections and so that the tube may -be arranged in a conventional duct-systemfor air-.cooling or maybe clamped in water jackets for liquid cooling necessary or desirable.

llt is-importantthat ample measures be taken to preventadverseeffects of secondary electron emission. y Reducedsecondary emission can `be obtained by .judicious -choice olfselectrodeV materials. lElectrode surfaces of carlbon, platinum and gold, for example, are excellent for use in` reducing secondary emission. The physical Vcon- .'iigurationfof the electrodes can also be designed to reduce secondary emission problems yThe deep cup-shapedanode electrode element (33 is well-known for this purv,.pose. and the useof the lip at Vthe entrance-aperture to the anode electrode 33 may be helpful. The drift 4tube .'35. is .preferably made of suchlength that` secondary emis- -sion .electronswill more than-likely be-returned to the'elec- ..trode.l35. However, to some degree, secondary elecrtron emission from the anode 33', when collected on the .anode 35', may .add tothe useful power output.

Referring again -to Fig. l, theelectric wave translating Asystemaccording to theinvention Viscompleted bymeans o'lfan output coupling transformer'46hiaving two primary -windings47 and 48,-both coupled to an `output second- .ary winding Y49. Itis anticipated that theratio of turns .in windings 47 and 48 will be adjusted for .bestoverall {results-.taking into account both power conversion effi-` .ciencyand output current -wave form. -Inpractice the -ratio..is .expectedtorange'from'a value of lup to-perhaps 4er 5,. .depending on conditions. The secondary winding 49 is connectedtooutput terminals 51, `50-to which anydesired-utilizationvdevice may be connected. Direct .operating-,potential `of given value Ebb/1t is :applied to 'the electron collecting electrode element-33 by Yway of the rtransformer lwinding'47 while direct potentialEabs applied to the electron collecting-electrode Velement` 35 `by Vway1ofthe 4other primary winding 48 -of the :transformer 46. The-direct potential 'on the electrodeelement-'SS .iis

.-greaterthan'that `on the element 33'by-the factor In practice Ait -is desirable to have `the factor n.-equal to .2 .at least, and 3 wor 4 `if possible. 4.It should vbe under- -stood 'ithatthisfactor need not be 1a whole number, but

-theratio=offthe two potentials is indicative of the increase `in=power conversion eiiciency as will be shown inthelfollowing discussion.

For example, suppose that'the electron .collecting .elec- 'trodewelement'SS is supplied from asource of Epotential .--`of--15.000/2\or -7500 -volts D. C..and the otherele'ctron collectingelectrode element 35 is supplied:from-a source -:of.full potential-of 15,000 volts D. C. Fort'hezunmoduv lated :condition the emissioncurrentrpassed byfthe -conltrolfgrid 27 may `be,.'for example, 2 amperes, andallfof this-current'will-be vcollected on the electrode Aelernentlir :producing afpowerloss thereof 7500 2 wattsor I5 kilo- -watts. ln' the-conventional modulator `tube this current v'wouldihave'been lcollected on an anodeat the full 15,000

'volt-potential, causingapower loss of 30 kilowatts. Thus the-power' loss for the unmodulated case is reduced by the factor n, or 2 in the example given.

'Withthe tube :according to the invention,z-as.the 'grid v`f2.7=swingsnegative Vto rreduce the electron beam current,

-all the. diminishing current continues to flow to the lower `;potent:ial anode andthe `losses remain at half -what'the'y would'be'in a conventional tube used in the conventional manner. However, as the grid 27 swings positive to in- V'crease 'the electroncurrent and the potential of the elec- ;tron .collecting electrode element 33 diminishes toward fzero with respect to the cathode, current will Vbe reflectedvback to the tubular electrode element 35 and on peaks 'oflcurrent al1-of the current will flow into'the other electrodeelement 35,'while thepotential of electrode l33 will d be. negative with respect to the cathode. Therefore, the two anode-'electrodes can be made to "developa peak 5 potential variation approaching 15 ,'000'v`o1ts, vthereby providing peak A.'C. power output and eliciency atmaximum A. `C. current output, equal tothat of .a conventional tube. AThe net result when windings 547 and4'3lhave equal turns is that both anode Velectrodes may develop A. C; peak potentials corresponding tothe full `15,000 volts 'D. C. power supply potential, but the current transfers automatically'from one lelectron collecting electrode element to the other to'keep the average, powerflosses .at

Yroughly .l/n the value they would -beina conventional audioY amplifier orfmodulatortube.

. It is a distinct advantage in the Iapplicationof the invention that the. rectiiiers used inhigh powered transmitters are commonlydesigned toprovide a substantial amountof the rated outputpower. ata half voltage tap.

.Such rectiershave two rectifier `tubes in series in each leg -and thetransformerf'windingis .connected to the point between:.them. Therefore, the,:simp1e .circuitry of the .electric `wave translating system according to `the .invention willnotundulycomplicate the power supply problem.

When the .amplifier is .to be Aoperated constantlyI at full output,..somewhat-like.a class Camplier, it is possible `to obtain power yconversion eiciencies similar to, or better.than, .those nowobtained with class C-operation without resortingto such-large distortion inthe wave formof the electronV current. This will reduce problems in pre- Venting radiation of energy at harmonic frequency from .high-frequency industrial, medical and radio equipment.

From -another..standpoint,' the Vinvention allows utilization of the electron emission from the cathode, in class .C oscillatorsand `ampliliers,ovier a. larger fraction of the operating cycle forany given amount of powerloss. This either .will permit higheraverage lcurrent input to a tube with a given sizecathode or, Vfor any 'given required input current it will'permit a-smaller cathode'to be used. In

:other words, for any given power rating the system according to the invention reduces both anode losses and Icathodeheating losses. Alternatively, it will permit the Vcathodes to be operated-at lowertemperatures.

A suggested modification for the arrangements rvs'hownin Fig. 1 and Fig. 2'is to provide two or more tubularconductors forming aplurality'of velectron collecting elec- Ytrode elements35 arranged in .end-to-end relationship with increasing potential'on the elements `progressively remote from the-electron collecting electrode element 33.

Another embodiment of the invention is shown in Figs. `3 and\4, depicting ahi'gh'power. high 'vacuum vtube ar rangedin accordance with 'theinvention A .source 'of electrons inthe form 'ofa centrally located cathode`21" :is surrounded Yby a -heat `reflecting and beam Aforming element 25. The beam forming element 2'5" as shown yhere is-an elongated tubular or cylindrical. member having a plurality of' longitudinally 'arranged Vslits 26". The `beam forming element 25 is :surrounded by an electron Vcollecting electrode element v335in the form of a conductivetubular member or hollow cylinder. In the space between the beamformingmemberZS" and theelectron collecting electrode element .33 ainum'berof elongated conductive-members constituting electroncollecting electrode zelernents;V 35 #of .the :multi-.element structurey are arranged inthe shadows of thesolidgportionsiof thebea'm .forming -member-.25"zbetween the Vslits or slots 26.

' anchio apply any of the conventional cooling systems to the tube according to the invention. The outer electron collecting y. element 33" is preferably exposed so that .either a water cooling jacket or an air cooling jacket may be used to cool this electrode if necessary. Since much less heat is to be developed at the outer electroncollecting element 33 it is expected that air cooling will be adequate in most cases and this element 33" may be constructed with radiating ns if desired to facilitate such air cooling.

Glass or

ceramic envelope portions

63 and 65 are used porting insulator shown here merely as an annular insulating disc 67 in which one end of the cathode device 21" is supported with the other end centered by means of an insulating boss 69 projecting into an indentation in the wall of the header or exhaust manifold 57.

A typical circuit for use with the tube illustrated in i Figs. 3 and 4 is shown in Fig. 5. A radio frequency input Wave applied to the

input terminals

30, 31 is coupled into a resonant circuit 71 tuned to the desired operating frequency and the voltage developed thereacross is applied by way of a blocking capacitor between the cathode 21 and the beam forming element 25. Direct operating potential value Ebb/n is applied by way of a radio frequency choke between the electron collecting element 33 and the cathode 21. The resonant circuit 77 tuned to the output frequency is connected between a source of positive potential Ebb and the electron collecting element 33 by a coupling capacitor 79. The output circuit 77 is also directly connected to the other electron collecting electrode elements 3S. The output wave is applied to the

output terminals

50, 51 by means of an inductive coupling link.

The wave translating systems according to the invention as thus far described are limited in frequency range only type of tube shown in Fig. 6. Aivariable or modulated radio frequency wave applied tothe input terminals 30,

31 is inductively coupled into an input resonant circuit 71 for application between the cathode S7 and the grid 93'. Direct anode operating potential at value plus Ebb is applied by Way of a radio frequency choke 75 to the electron collecting coil 97 at the end nearest the cathode 87', and which end is connected to the sleeve 95'. The

Y output. circuit 101 incorporating the multi-turn electron collecting coil 97 is tuned to the desired operating frequency by means of two

capacitors

102 and 103, connected in series across the coil 97. The output Wave is derived across the capacitor 102 and presented to the fiers.

`tron collecting cap element 99 and instead Will begin to be collected on the electron collecting coil turn elements at first near the electron collecting cap element vention which comprises an evacuated outer envelope containing a heater element 83 for heating an indirectly heated oxide cathode device 87 having a cathode terminal 89 surrounding the heater leads. A grid sleeve 91 surrounds the cathode sieeve 39 and a grid 93 is mounted in the upper end thereof above the oxide cathode element. The cathode and grid structure is arranged according to known principles for forming and modulating the intensity of a beam of electrons. A small or moderate value of magnetic eld generally parallel to the axis of the tube 80 may be applied as an aid to form the electron beam. The multi-element electron collecting electrode structure of the tube 80 comprises a sleeve member 9S connected to a multi-turn inductance coil 97 which is terminated in a metal cap electrode 99. The beam of electrons is allowed to pass from the cathode through the control grid 93 in accordance with the signal applied thereto and the electrons of the beam then tend to pass through the multiturn electron collecting coil 97 to the electron collecting electrode cap element 99.

A schematic diagram of the wave translating system according to the invention is shown in Fig. 7, using the output terminals 50, S1. The amount of load is adjusted by varying the capacitances of the two capacitors 102, 163 diiferentially.

In operation, the Vcontrol grid 93 is biased negative in the usual manner so that, in the obsence of radio frequency input, a small electron current will flow from the cathode 87 through the control grid 93', through the sleeve and the coil 97' to the electron collecting cap element 99 at the far end of the multi-turn electron collecting coil 97. The amount of this small D. C. current is so adjusted that the radio frequency output will be proportional to the radio frequency input at very small input and output levels, as is commonin class B ampli- As the applied radio frequency Wave amplitude is increased progressively, a modulation or variation of the electron current will take place at the input frequency. But as the input is increased the current will begin to cut f oif when the grid potential is negative and from somewhat more than that level upward the electron current will begin to flow in discrete pulses, the pulses increasing in strength with increasing input amplitude.

- oscillations will reduce the potential of the electron col- Vloss at the electron collecting cap element 99, just as in any conventional class B ampliier. However, unlike the operation of conventional class B ampliers, the potential of the electron collecting cap element 99' will swing down to and beyond zero with respect to the Ycathode 87 at only a moderate percentage of the maximum power input and output, and while the electron current pulses are still rather small. The pulses of electron current will then cease to be collected by the elec- As, the amplitude increases still further the zero potential point along the coil 97', at the time electron current pulses llow, will move along the coil toward the sleeve 95'. Electron collection will then take place always at a region of the multi-tum coil 97' which is near zero potential and power loss due to electron collection will remain low at all amplitudes up to the maximum for -which the tube and the circuit components in the wave ,level is about half the peak amplitude, as it will be in amplifiers used with amplitude modulated carrier currents, the power loss in a practical case may be reduced by the invention to about half or less of what it would be in a conventional amplifier.

It Amay be noted that not onlydoes the point of collection of electron current on the coil 97, at the instantaneous Ynegative peaks of R. F. potential, move along the coil .i asoma() `It is suggested thatthe multi-.turmelectron .vcllect'ing coil 97 may'be varied Vin pitch along-'the length-thereof to modify the amplitude response 'characteristic' by a moderate amount. Itis also considered that the final turn of the coil 97 may have a shorter radius so that it acts as the end cap in a terminal eliminating the need for an electron collecting cap element, although it is recognized that the use of the separate secondary emission preventing cap element 99 is preferred.

It is anticipated that in a tube like that of Fig. 6, for operationat relatively high frequency and power levels the coil 97 may be made of tubing, through which a coolingfluid may be circulated. j

Another embodiment of the invention is found in the tube 80 illustrated in Fig. 8 and Fig. 9p, in which the same beam forming electron gun assembly as shown in the tube of Fig. 6 is used. Instead of a multi-turn coil, however, a series .of tubular electron collecting electrode elements 101-105 are distributed along the electron beam between the grid sleeve 91 and the electron collecting terminal cap element 99. Preferably, these electrodes 101-105 are tapered or necked down and situated so that one is inserted into the other for a suitable distance. The electrodes 101-105 are preferably exposed for a portion of their lengths, so that suitable external connections may be readily made and cooling may be facilitated. Glass envelope portions 121-126 are used to complete the evacuated envelope of the tube 80".

As shown in Fig. 9, the electrodes 101'-105 together with the electron collecting terminal cap element 99 form the electrodes of a capacitive reactance component, which when shunted across an inductive reactance element 131 forms the output circuit 133. The circuit 133 may be tuned by varying the inductance of the element 131 but may also be tuned by adjustment of a plurality of capacitors 141-145 forming a capacitive potentiometer. Each of the electrodes 102-105' may be connected to a tap on the inductive reactance element 131, but a plurality of R. F. chokes 151-155 are preferably used for this purpose.

The arrangement of Fig. 9 functions in very much the same manner as the arrangement of Fig. 7. The modulated wave signal input is applied at the

terminals

30, 31 and the electrons emanating from the cathode 87 pass through the electrodes 101'105, and are collected on electron collecting electrode element 99. As the potential of the electron collecting cap element 99 swings down- Ward due to increased current flow and reaches a point at which the potential on the element 99 is lower than the potential on the element 105', the electrons transfer themselves for collection to the electrode 105. When this electrode 105 has its potential reduced due to electron current ow to a value lower than that on the next electrode 104', the electrons then transfer themselves for collection to the latter electrode element 104' and so on.

The arrangements shown in Figs. 6 and 7 are considered limited to frequencies above 3 megacycles per second. Since these embodiments form a part of the reactance of the` output circuit it appears that each tube must be designed for a particular range of frequencies. It is not considered that this factor is in any way detrimental because it is well-known that any inductor can be designed for operation .over a range of frequencies at least as great as 2:1 land even wider ranges under certain circumstances. The tube Shown in Fig. 8 is probably more readily operable over a wider and lower frequency range because of the fact that external capacitance as well as inductance will usually be employed. It is contemplated that the values of reactance between electrodes 101-105' in the arrangement shown in Fig. 9 may be changed or .adjusted deliberatelyY to modify` the` amplitude response `characteri'stic.arid l'the fliciencyunder certain operating conditions if Vsuch appears"desirble."j'lhis'fis readily ,accomplishedby varying'the relatively higl'frequency potentialsappliedotthe :succession `ofaclectrodes. lbf-165.

It is also contemplated that the circuit arrangements according to thelinvention-maybeused with all the usual -.f`expe.dients fto..prevent,.r.adio frequencyffeedbaek,tisiich as -rsh'ieldinggtneutralizing,..and.tl1e.1ike.

The invention claimed is: p

l. An electron discharge device wave translating system comprising means for producing a beam of electrons, means for modulating the intensity of said beam in accordance with a signal wave to be translated, a plural-element electron collecting electrode structure constituted by one member upon which said beam lof electrons tends to inipinge and by a multi-turn coil through which said electron beam is projected and upon which said beam may impinge, and means for establishing at -an'y given instant different signal-developed potentials upon said member and the turns of said coil, said last-named means including a resonant output circuit coupled to said device.

2. An electron discharge device wave translating system comprising means for producing a beam of electrons, means for modulating the intensity of said beam in accordance with a signal wave to be translated, a plural-element electron collecting electrode structure constituted by one member upon which said beam of electrons tends to impinge and by a coil through which said electron beam is projected and upon which said beam may impinge, and a resonant output circuit constituted at least in part by said coil coupled to said device, the oscillations produced in said output circuit causing said member and said coil to have, at any given instant, different signal-developed potentials.

3. An electron discharge device wave translating system comprising means for producing a beam of electrons, means for modulating the intensity of said beam in accordance with a signal wave to be translated, a pluralelement electron collecting electrode structure constituted by one member upon which said beam of electrons tends to impinge and by a multiturn coil through which said electron beam is projected and upon which said beam may impinge, a capacitive reactance element connected across said coil to form in combination therewith a circuit parallel resonant at the desired output frequency, the oscillations produced in said resonant cir-cuit causing the elements of said structure to have, at any given instant, different signal-developed potentials, and output connections coupled to said parallel resonant circuit.

4. An electron discharge device wave translating system comprising means for producing a beam of electrons, means for modulating the intensity of said beam in accordance with a signal Wave to be translated, a pluralelement electron collecting electrode structure constituted by one member upon which said beam of electrons tends to impinge and by a multi-turn coil through which said electron beam is projected, one end of said coil being connected to said member through connections devoid of concentrated impedance, and a resonant output circuit constituted at least in part by said coil coupled to said device, the oscillations produced in said output circuit causing said member and the turns of said coil to have, at any given instant, different signal-developed potentials.

5. An electron discharge device wave translating system comprising means for producing a beam of electrons, means for modulating the intensity of said beam in accordance with a signal wave to be translated, a pluralelement electron collecting electrode structure constituted by one member upon which said beam of electrons tends to impinge and by a multi-tum coil through which said electron beam is projected and upon which said beam may impinge, and means for establishing at any given `11 A instant different signal-developed potentials along the 2,232,050 length of said coil, said last-named means including a 2,233,126 resonant output circuit coupled to said device. 2,240,183 V2,332,977 References Cited in the le of this patent 5 2,444,073 UNITED STATES PATENTS .2,733,305

1,969,399 Farnsworth Aug. 7, 1934 2,122,538 Potter July 5, 1938 l 12 e Clavier Feb. 18, 1941 Haeif Feb. 25, 1941 Hahn Apr. 29, 1941 .Skel1ett,... Oct. .'26,` 1943 Tomlin June 29, 1948 Diemer Jan. 3l, 1956