US2905859A - Traveling wave electron discharge devices - Google Patents

Description

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Sept. 22, 1959 J. M. OSEPCHUK ETAL 2,905,859

TRAVELING WAVE ELECTRON DISCHARGE DEVICES Filed Oct. 27, 1953 2 Sheets-Sheet 1 I/NVENTORS JOHN M. OSE'PCHUK Roy A. PAANANEN p 22, 1959 J. M. OSEPCHUK ETAL 2,905,859

k 0 F D o q FR UENCV IN MEGACVCLES PER $ECOND y A A M614 By Arm/2 EY United States Patent TRAVELING WAVE ELECTRON DISCHARGE DEVICES John M. Osepchuk, Peabody, and Roy A. Paananen, Needham, Mass, assignors to Raytheon Company, a corporation of Delaware Application October 27, 1953, Serial No. 388,473

12 Claims. (Cl. SIS-39.3)

This invention relates to electron discharge devices and more particularly to methods and means of construction of electron discharge devices of the traveling wave type having lossy material therein.

In electron discharge devices of the traveling wave type, wherein signal waves traveling along a network interact with electrons moving along paths adjacent to the network to produce amplification or oscillation, it is often desirable to introduce signal-absorbing material into the electron discharge device for the purpose of absorbing unwanted signals producing the wrong frequency or phase of interaction with the electron stream. Previously, lossy material had been painted or sprayed on various parts of the electrode structure. This was not satisfactory, since the lossy material tended to flake ofi after the electron discharge device was evacuated, was difiicult to free from gas, and was diflicult to accurately apply in the desired region to the desired thickness.

4 This invention discloses the discovery of a particularly desirable lossy material for use in electron discharge devices. The preferred embodiment of this material is pure iron. However, it is to be clearly understood that the invention is not limited thereto, but rather other ferro-magnetic materials may be used.

This invention further discloses that such material may be applied to the desired parts of the electron discharge device by electrolysis, which may be accurately controlled to produce a relatively thin uniform coating of iron in the desired region. This coating does not flake off, is relatively easily outgassed during assembly and evacuation of the device, and is closely controllable as to thickness of the coating whereby the finished dimensions of the parts may be accurately controlled during production. The electrolysis, or electro-plating technique of applying the lossy material, is particularly useful in devices where close tolerances must be maintained, since no mechanical stresses are utilized during application of the lossy material which might deform the parts of the electron discharge device, as is the case when the lossy material is sprayed or painted on the tube elements. I

This invention further discloses that the ferro-magnetic lossy coating described above is particularly useful in traveling wave devices utilizing transverse magnetic fields, since the extremely thin coating required to produce the desired loss produces little or no distortion of the magnetic field, as would be the case if larger masses of ferro-magnetic material were applied, for example, by spraying or painting techniques, or by fabricating the tube elements of ferro-magnetic material.

This invention further discloses that the effectiveness of lossy material in the electron discharge device may be further enhanced by making the characteristic impedance of the network structure different in the region thereof containing the lossy material than in the other regions of the network structure where it is desired that the rate of build-up of signal energy be a maximum. Specifidirection opposite to the direction of motion of the energy of the signal wave traveling in the network struc ture but in the same direction as the apparent phase velocity of a component of the wave traveling in the network structure, the lossy material is positioned in the region adjacent one end of a nonreentrant network structure toward which electrons move along paths adjacent the network structure, and signal energy is extracted from the device adjacent the end of the network structure away from which electrons move along paths adjacent the network structure. The impedance of the network structure along the majority of the network structure is made as high as feasible from the standpoint of structural requirements, heat dissipation requirements, and breadth of frequency response characteristics, while the impedance of the network structure the region of the lossy material from the spacing of the fingers throughout the remainder of the network, there by lowering the characteristic impedance of the network in this region. In order to prevent impedance discontinuities along the network, the lowering of the impedance is accomplished by reducing the spacing of the fingers gradually and by placing lossy material on the fingers in the region where the spacing is being gradually reduced.

This invention further discloses that the network may be nonreentrant, that is, signals traveling along the network do not reenter upon themselves, this being accomplished by a break in the network such that the network has two ends substantially isolated from each other at the frequency of the signals except for the path along the network and except for any coupling which may be achieved from electron streams interacting with the network.

Other and further objects and advantages of this in vention will be apparent as the description thereof progresses, reference being had to the accompanying drawings, wherein:

Fig. 1 illustrates a longitudinal cross-sectional View of a linear magnetic backward wave oscillator utilizing the lossy material and impedance transformation features of this invention;

Fig. 2 illustrates a transverse cross-sectional view of the structure shown in Fig. 1 taken along line 22 of Fig. 1;

Fig. 3 illustrates a transverse cross-sectional view of a further embodiment of the invention illustrating the features of this invention as applied to a circularly arranged backward wave oscillator utilizing a transverse magnetic field; and

Fig. 4 illustrates a graph showing the attenuation produced by structures of Figs. 1, 2 and 3.

Referring now to Figs. 1 and 2, there is shown an electron discharge device comprising an anode structure 10. Anode structure 10 has a metallic envelope portion made up of a back plate 11, a front plate 12, end plates Patented Sept. 22, 1959 ac us ic plates 13. are a pair. of spaced, parallelanode support members 15, which are, for example, metal. Each of support members 15 has attached thereto a plurality of anode. element s; 1 6, whichextend; toward. the opposite; support member; 15 5 from t i ow i i hfiy; rea ta h d The: fingers attached to. opposite support members; 15 overlap to.f.orm n' nter ie t q zld diwaveu dsr ru ofaanode networkjstructure. Fingers 16 ;arespaced from; back wall; mem d. e a ss t n h n of fing rs 16 an e ppo te uppo me b r: 5 r m; that to which theyare attached are made: substantiallyequal tothe, spacesbetween adjacent. fingers, I tis to be, clearly' nderstoodt o v r, ha othe ra qsh paciha couldlbe used;

Bos tirme omewhat: eyond: ne; n an n' nt: if: n ork; a fingers: isa atho es i w e 1-7,. 9 k a is n atho upp t; memberv 1 h. m y be, or example an. nu ary in r a em zsri h 2;: tends: outwardly-through front plate '12 and spaced-therefrom he t o e pp rt memb s s a d-. ye n otan n a ins- 1 19 a y i d sa m m fi. w ich: nfill-I 13; s caledi o h p tur n r t pl ten h. which, support plate member 18 passes. An indirectly hea d a h de s s o i y. Q a pl s being i i ly at a h h ne t lid o pp r y d Qathc e omp e ar urew t ihins. heater wire- 2 2:. Oneend ofheater-wire 22. is connected;- to; the cathodeZl, and the other end thereof is connected to a lead-in; member 23; extending outwardly through. s ppo yl nd p c re rom, an nsn afihs y eal d o e o r d. of s pp t; i r 3 1 9: nsu a in 21. h r a ed. athod lr sh s pre en d; e p ne nt inin t e s. hc'fih rs .651s; ated. t ;-.e e nm iv ma e ial; 5..

A conductive bloclg 26v attached to the anode structure 1&- directly. opposite the electron-emissive suriace isprof. vided, forthe purpose of;correctly shaping the electron; str m which. up n the h a o a h defl m ates iirom, the electromernissive, coating- 25. 'ljhe electron. ream sdi ect lo e P s. a i e t h ro t. ia e of fingers 16 under the influence of transverse elect-ro-. static and magnetic fields. The electrostatic field; is prodnced; between said; fingers: and a sole 27 which is posi; t nne n r of in r n -w c uppq t lead-insupports; 28 extending out through, the. front Plate; 12 and insulated therefrom;- the magnetic field, transverse to. the electrostatic field is produced by means; Qf-f magnetic pole pieces 28a. The anode structure s, main ne P v t v re pe he ole l c o 27 and the potential on the cathode structure 17 isga da jnstedsuch. that electrons emanating from surface 2 5 will, with the proper polarity of magnetic field produced between pole pieces 28a, travel down thespace; between. fingers 16 and sole 27, whereby signals traveling, along; the-network of fingers 16 will interact with said electrons causing signal amplitude build-up, and, in this case, oscil-. lations.

Attached to the anode finger element 16 nearest cath-. ode structure 17 is a signal output lead 29, which extends outwardly through an aperture in the back plate ll 'and forms the central conductor of a coaxial line 30 whose outer conductor 31 is sealed to the back plate 11 at the aperture through which the output lead 29'passes. The lead 29 is insulatingly sealed to the outer conductor'31; by means of a ceramic seal situated inside coaxialline 30 and not illustrated in the drawings. The coaxialline 3.0. forms a signal output coupling, structure from which high frequency, energy is. extracted from, the. anode networkand fed to any desired load. A signal coupling structure 32 is illustrated'herein asbeing connected; tothe; anode; fingers 16 at the other end of the network strucr ,..h t may .v om t ed, ir since all thepower is extracted from the device by means of the coaxial line 3.0-. Structure 32 may be used, for example, for

measurin refl e ne n tahs rhsd l for injecting a locking signal.

Lossy material is introduced into the network structure at the end thereof away from the cathode by coating the fingers 16 in this region, for example thirty in number, with such lossy material; Thelossy material is applied before assembly of the device by dipping the fingers 16 attached to the support: members 15- in an electrolyte solution, which may be, for example, a solution of seveht ps ce tt by e h f sr s c ide. nd-thins.

percent; y. ei hs. Qt: al i m. hlo ide; t. oncentr tion of twenty-two grams per liter of. Water. An electrode of pure iron, is. placed in the electrolyte solution and is connected to the positive pole of a voltagesource, while the negatiy e poleof a voltage; source is connected to the fingers 16 through the anode support members 15. The portion of each support member 15 and the fingers 16 which it is desired not to coat may be kept. out or; the electrolyte or coated withv any desired coating which will; prevent. a deposit of iron thereon. Ihecoating of; pnre iron which appears onthefingersld is very uniform and, the, thickness of the coatingmay be closely controlled by controlling the time. and current of the plating process. The coating may be of the order of. .001 inch, or less, completely surrounding the appropriate fingers, thereby; providing better adherence. of the coating than, fingers, which are partially encased. It hasbeenfonndtthatLirf, fingers and other elements of the anode structure. be. made or copper, heat generated in the iron coating easily conducted away, such that lossy. material absorb large. amounts of power without difiicultyi In. order. to increase the 'efiectiyeness of absorptiqnof energy, in. the region of the network structure coated. with lossy material, said region being indicated stippling on. the fingers 1 6, thefcharacteristic impedance. of the network is made lower in this region than along theremainder of the network structure whichis designed to be the major portion oi the network structure. This is. accomplished by decreasing the spacing between the;v fingers. in 'the region. For example, the spaces 33; be}. tween the. fingers at the end of the network away from the cathode. structure 17 are much sniallenthan the spaces 34- between the fingers over the maj or portion. of the anode. network, said portion extendingtothe end of the network structure to which the outp it, coupling structure 30. is connected. I A i In order to avoid a sharp transition between the. high characteristic impedance. of the networkstructure over, the major region thereot and the low characteristic int: p q c i-: the i n, eo i in he o sy ma..- terial, a transition section is provided also containing lossy material wherein the spaces as shown at 3 5 gr adi1a:lly decrease. from thesizeof spaces 34; along. the netyi o glgawayv from, the. cathode to the size, of spaces 33,- this transitional: section being, for example nine or; ten inlength, The length of; the transitional section somewhat less than an electrical quarter wave length ovcr the range of desired operating frequencies for-the particulardevice illustrated herein. However, the bandpass ofithe network structure is sufiiciently broad that the spaces, 35 have, to some degree, quarter wave impedance; trans former characteristics, and the change inspacing betweeir adjacent fingers is adjusted in accordance withthe desiredimpedance thereof it the successive spaces; are considered as successive sections in amulti-section quarter wave inapedance transformer. This action is further; irnprcwedv by'havingthefingersin the transistion sectionaiso coated with lossy material While in thedevice shownherein the pitchdistance. between adjacent fingers has been held constant and the spacing between fingersadjusted; by adjusting the thickness of thefingers, itis to: be clearly. understood thatthe spacing between fingers-couldzalso be adjusted by; maintainingv a constant finger thickness and varying the pitch. distance between fingers, or b'y-varyihg bothcfingenthickness andpitchdistance, if so desiredi Itis also to be clearly understood that the particular lossy material disclosed herein may be used with other impedance transformation structures, or with other anode struc-.

tures than the interdigital structure, such as helixes, strapped and unstrapped cavity-type network structures, such as those conventionally used in cavity magnetrons, or any other desired signal-wave transmission network. It is to be clearly understood that the lossy material and impedance transformation techniques can also be utilized with traveling wave tubes which do not employ transverse magnetic fields and with traveling wave tubes for ampli fication as well as oscillation generating purposes.

Referring now to Fig. 3, there is shown a transverse cross-sectional view of a further embodiment of this invention utilizing a signal wave transmission network structure arranged along an arcuate path. The anode structure comprises a hollow metallic cylinder 36 covered by a lower end plate 37 and an upper end plate, not shown. Interdigital fingers 38 are provided for the signal wave transmission network structure, said fingers being attached to support rings 39, which, in turn, are attached to the inner surface of anode cylinder 36. The spacing of the fingers 38 and the mounting thereon with respect to the anode cylinder 36 are similar to that described in connection with fingers 16 of Figs. 1 and 2, the dilference being that fingers 38 lie in an arcuate locus, while fingers 16 lie in a linear locus.

Over one portion of the arcuate locus of the network structure, the fingers 38 have been omitted and a conductive member 40 has been substituted, this being securely attached to anode ring 36. Member 40 is dimensioned and positioned such that waves traveling along the network structure are prevented from being coupled between the two ends of the network of members 38, except along the network, so that the network structure is nonreentrant. Also a projection 41 on member 40 prevents electrons, moving along paths adjacent the fingers 38, from traversing the gap between the adjacent ends of the network structure of fingers 38. A signal output coupling device 42 is coupled to the network structure by connecting the center conductor 43 of coupling device 42, which comprises a coaxial conductor, to the end finger of the network of fingers 38 away from which electrons move along the network of fingers 38. Conductor 43 extends outwardly through an aperture in anode cylinder 36 spaced therefrom, and is sealed by means of an insulating seal, not shown, to an outer conductor 44, which, together with an inner conductor 43, makes up the signal output coupling device 42. Device 42 is similar to the device 30 of Fig. l. The anode fingers 38 at the opposite end of the network structure from the coupling device 42 have the spacing therebetween decreased similar to the manner disclosed in connection with Figs. 1 and 2 and are coated with lossy material in a manner similar to that described in connection with Figs. 1 and 2.

' Positioned inside the region defined by fingers 38 is a substantially cylindrical sole structure 45 which is attached by means of a web 46 to a support cylinder 47, which, in turn, is insulatingly supported through the upper end plate by 'an insulating seal, not shown, in accordance with well-known practice.

- A cathode 48 is positioned adjacent the member 40 somewhat beyond the end of network of fingers 38 to which coupling device 42 is connected. Cathode 48, as shown here, is a ribbon extending parallel to the fingers 38 for substantially the same distance parallel to the axis of the tube as the fingers 38. Cathode 48 is held in position by upper and lower cathode support members 49, which are urged apart by spring 49a. Support members 49 are connected through insulating supports indicated diagrammatically at 50 to projections 51 attached to sole 45. A conductive lead-in structure 52 connects one of the cathode support members 49, for example, the upper one, to a lead-in cylindrical member 53, which extends coaxial with cylinder 47 and is sealed thereto by an insulating seal outside the discharge device in accordance with well-known practice. The other cathode support 49 is connected by means of a conductive lead in structure, not shown, to a lead-out member 54 positioned inside cylinder 53 coaxial therewith, spaced therefrom, and sealed thereto by an insulating seal outside the discharge device in accordance with well-known practice.

A magnetic field is imposed parallel to the axis of cylinders 36, 47 and 53, and, hence, parallel to fingers 38 and cathode 48 in the space between fingers 38 and sole 45 and the space between cathode 48 and member 40. This magnetic field is produced by means of magnetic pole pieces positioned adjacent the outer surfaces of the end plates, including end plate 37, in a similar manner to the application of pole pieces 28:: to the device shown in Figs. 1 and 2.

Electrons are emitted from the cathode 48 when a suitable heater current is applied to the cathode 48. Cathode 48 may be any suitable electron-emissive material, such as tungsten or tantalum, or may be coated with electron-emissive material. Electrons emitted from cathode 48 will be directed along paths between the anode signal wave transmission network structure of fingers 38 and the sole 45 in a direction counter-clockwise, for the view shown in Fig. 3, under the influence of an electrostatic field (produced by a voltage impressed on the sole 45, which is negative with respect to the anode 36 and fingers 38, and the above-mentioned magnetic field. Backward wave oscillations developed along the network of fingers have energy components which travel in the opposite direction from the direction of motion of the electrons, and, hence, arrive at the output coupling device 42 whence they are coupled to the desired output load, not shown. Undesired reflections having energy components traveling in the opposite direction, that is, in the same direction as the electron stream, are absorbed by the lossy material coated on the members 38- in the region at the other end of the network of fingers from that to which coupling device 42 is connected.

Referring now to Fig. 4, there is illustrated a graph showing the degree of attenuation which has been achieved with the type of lossy material and network impedance transformation structures disclosed herein. Along the axis of abscissae is plotted frequency in mega cycles per second, the region shown here, by way of example, being from 2300 megacycles to 3100 megacycles. Plotted along the axis of ordinates is the attenuation in decibels which is achieved by applying an input signal to the coupling device 42 and measuring, by means of a coupling device connected at the other end of the network of fingers 38, the amount of energy propagated along the network of fingers through the lossy material coated on a portion thereof. The graph of Fig. 4 indicates the attenuation in decibels and shows that at the lower frequency of, for example 2300 megacycles, the network structure has a loss of approximately thirteen decibels, as shown by point 55. The attenuation increases slightly with frequency reaching fifteen decibels at approximately 2700 megacycles, as shown by point 56, and then increases more rapidly reaching a loss of approximately nineteen decibels at 3100 megacycles, as shown at point 54. Thus it may be seen that the network structure illustrated herein has a relatively uniform loss over a relatively wide range of frequencies.

This completes the disclosure of the specific species of the invention illustrated herein. However, many modifications thereof will be apparent to persons skilled in the art without departing from the spirit and scope of the invention. For example, the device shown in Fig. 3 could have a grid positioned over the cathode 48 in order to control the quantity of electrons emitted from the cathode.' The device of Fig. 3 could be made with the network of elements on the inside surrounded by the sole and cathode. If so desired, a signal coupling device similar tothe device 42 of Fig. 3 could be connected accuses;

tothe other; end: ofthe network of fingers' 38'- from that towhich; device 42 is connected for the purpose of in. je'ct-ing; a signal for stabilizing, locking, oramplifying. purposes. The lossy material inthe" case of an amplifier could be coated uniformly along the length.- of:- networle of fingers 38' rather than at one end thereof,- the lossy coating or material may be omitted, and the; lower-- ingof the characteristic impedance in the desiredr region offattenuatio'n may bereliedonto producev said attenuaa tion particularly'at the higherfrequencies. If? desired, a continuous cathode along the entirelength of the sole 45 or. along anydesiredportion, thereofcould: be used in' place of the point source cathode illustrated? herein Accordingly, it is desired that this invention be not limited: by the particular details illustratediherein, exceptv as.- defined by the appended claims.

What is claimed is:

1'. An electron discharge devicecomprisinga sourceof electrons, a signal wave transmission network struc-. tureforpropagating electromagnetic wave energy and; spaced from saidsource, meansfor directing. electrons. from said" source along paths adjacent: to. said network: structure in energy-exchanging relation: with. said waveenergy and signal outputmeans coupled to'said network structure adjacent the end thereof fromwhich electrons. are emitted, said network structure having a signal ab-. sorbing; region adjacent said signal; output means; and occupying a minor portion of said structure, the char acteristic impedance of said network structure being.- lower in-said region thanin'theremainder of said-T net-. work structure.

2. An electron'discharge device comprising a source ofelectrons, a signal-wave transmission networkstructure spaced from said source comprisingaplurality.-of-: substantially non-magneticinterdigital conductive members, and signal absorbing means: coupled to. a minor portionofsaid networkstructure, the characteristicimpedance of said network structure being lowerin theregion of saidabsorbing-means-thanin therernainder-of' said network structure, the configuration of said network structure in the region of said absorbing meansbeing. progressively varied.

3-. A signal wavetransmission network structure, and signal absorbing means coupled to a minor portionof said network structure in a region spaced from said signal output means, the characteristic impedanceof said network structure being lowerin the region of: said ab.- sorbingmeans than in the remainder of said network structure.

4. An electron dischargedevice comprisinga source of-electrons, a slow wave transmission network structure for propagating wave energy, said network structure having an energy-absorptive region, means for directing electrons from said source alongpaths adjacent to saidnetwork structure and-in energy-exchanging .rela-v tionwith said wave energy, the characteristic impedance of-the entire absorptive region of said network structure being-lower than that of the remainder of said network structure.

5: An electron discharge device-comprising a= source of electrons, a slow wave transmission net-work structure for propagating wave energy, meansfor, directing electrons from said source along-pathsadjacent'to said network structure in energy-exchanging, relation with said wave energy, said network structure--includi'ng-an energy-absorptive region and a majorportion along which the preponderance of energy exchange between said wave energy and said electron beam-occurs, the characteristic impedance ofsaid signal-absorptive region of said-structure being less than that of said major portion -ofsaid structure.

6.- Anelectron-discharge device-comprisinga source of-electrc-ns, a non-reentrant slow wave transmission .network. structure for propagating wave energy; means for directing-electrons from said source along: paths adjacent 8- tO. saidnetwork structure in. energy-exchanging relation; with-saids wave energy, said network structureincluding' an: energy-absorptive region positioned adjacent the: endof: said: network structure toward. which electrons move 5 along said paths, and a major region alongwhich the preponderance of energyexchange between. said' wave energy and said' electron beam occurs, the characteristic impedance of said signal-absorptive region of said struc ture being: less than that of said major region of said structure.

7; An electron discharge device comprising a source of electrons, at slow. wave transmission network structure for-propagating waveenergy, means for directing: electrons fromsaid source along paths adjacent-'to said-net'-- work structure in energy-exchanging relation: with said waveenergy, said network'structure including an-energy absorptive region-at least a portion ofwhichis of: sub--' stantially uniform impedanceand a major region alongwhich the preponderance of energy exchange between saidwave; energy: and said electron beam occurs, the characteristic impedance of said signaI abSor tiVe Iegionbeing less than that of said major region.

8; An electrondischargedevicecomprising asource of electrons, aslow wave transmission network structure for: propagating waveenergy, means for directing: elw trons from-said source along: paths adjacent: to said net work structure and in energy-exchanging relation withs'aidwaveenergy, said network'structure comprisingan energy-absorptive region including a plurality ofi spaced conductive: members of-uniform pitch, saidnetworlcstruc turefurtherincluding a major portion-along which tliei preponderanceof-energy exchange between thewave energ y andth'e electron beam occurs; the conductive menu b'ers of saidenergy-absorptive region having disposed thereon loosy material, the spacing between-adjacent ones otsaid membersbeingless in the region of said lossy ma terial than alongsaidmajor portion of said network: structure; whereby the characteristic. impedance at said; energy-absorptive-region is less than that 'of said major; port-ion ofi said network structure.

9. An electron discharge device comprisingasource of electrons,- a 1 slow wave transmission network structure; for propagating wave energy, means-for=-directingz elee-p trons-from said source along paths adjacent=to saidlnet work structure and in energy-exchanging: relatiolriwitb said-wave energy, said network' structure comprisingcan: energyab'sorptive region including-a plurality. of -i spaced; conductive membersof uniform thickness; said :network' structure-further including a major portioni aiong which thepreponderance of energy :exchange between the :wav: energy and the electronbeamoccurs; the. conductive. members of said energy-absorptive. region having posed thereonlossymaterial, the pitch ofzsaidinetwork structure-being less than inthe-regionofi said lossy mae terial than along said major portioncofv saidznetworki' structure, whereby'the characteristic impedance: of'said energy-absorptiveregion is-less than that of said. major: portionof vsaid network-structure.

10.= An electron-discharge device comprising; a source of electrons; aslow wave transmission. network. structure for propagating wave-energy, meansion:directingieleca tronsfrom said source-along paths adjacentutosaid networkstructure and im energy-exchauging -;relation. with; said 'wave energy, said i net-work structure; comprising a plurality of spacedco'nductivemembers, said: network structure including an energy-absorptive region :at leastza portion of which is of substantially uniform impedance and a=m-ajor= portion 'alongwhich thepreponderanceiofi energyexchange between the; wave energy andathedelec tron beam occurs,- the conductive memberstof'said energy absorptive: region havingdisposed. thereon .lossy-vmateria'l, the. characteristic; impedance. of. saidtenergy-absorptive region of said structurerbeingslessithantthatzofisaid:major portion of said structure,

11, Anelectron,.dischargedevice accordingto claimJ wherein the construction of the network structure in the energy-absorptive region is progressively altered to provide an impedance match between said portion of said signal-absorptive region of substantially uniform impedance and the major portion of said network structure.

12. An electron discharge device according to claim 10 wherein the construction of a portion of the members of the network structure in the energy-absorptive region is progressively altered to provide an impedance match between said portion of said signal-absorptive region of substantially uniform impedance and the major portion of said network structure.

References Cited in the file of this patent UNITED STATES PATENTS Meyer Nov. 3, 1908 Doehler et a1 Nov. 28, 1950 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 2,905,859 September 22, 1959 John M. Osepchuk et al It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 6, line 28, after "fingers 38" strike out the comma and insert instead a closed parenthesis; column '7, line 24, after "energy" insert a comma; line 27, after "means" strike out the comma; column 8, line 35, for "loosy" read lossy Signed and sealed this 22nd day of March 1960,

(SEAL) Attest:

KARL Ha AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents

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