US2827588A - Travelling wave discharge tube arrangements utilizing delay lines - Google Patents

Description

March 18, 1958 P. GUENARD ET Ax. 2,827,588

y TRAVELLING WAVE DISCHARGE TUBE ARRANGEMENTS UTILIZING DELAY LINES Flled Aprll 17; 1952 3 Sheets-Sheet 1 (s Y V/ @gf ZLH #i 3 Y *i f. I @ummm mm March 18, 1958 P. GUENARD ET AL 2,827,588

TRAVELLING WAVE DISCHARGE TUBE ARRANGEMENTS UTILIZING DELAY LINES Filed `April 17, 1952 3 Sheets-Sheet 2 49 MIU/H //J\ geen/vis March 1'8, 1958 P. GUENARD ET A1. 2,827,588

TRAVELLING WAVE DISCHARGE TUBE ARRANGEMENTS UTILIZING DELAY LINES Filed April 17, 1952 5 Sheets-Sheet 5 i l z: il] L11-s L Il ri iuj] I E* on l:: Lila I 3]: .I LID m :Il j] :3 :im i

IC. /j 1^' "6 T" 5 effec" 60g/Hlth Has/y 71s United States aterra itiice n Patented Mar. 18, 1958 TRAVELLWG WAVE DISCHARGE TUBE AR- RANGEMENTS UTLZENG DELAY LINES Pierre Gunard, Robert Warnecke, and Ren Berterottiere, Faris, France, assignors to Compagnie Generale de Telegraphie Sans Fii, a corporation of France This invention relates to travelling wave discharge tube arrangements of the kind in which a delay line is used in association with an electron beam discharge tube.

The invention is illustrated in and explained in connection with the accompanying drawings.

Figure l is a plan View of Figure 2 showing a prior art delay line of the interdigital type;

Figure 2 is a cross-sectional view taken along line 2f-2 of Figure l;

Figure 3 is a top plan View of a delay line of the interdigital type in accordance with the present invention;

`Figure 4 is a cross-sectional view taken along line 4 4 of still another embodiment of a delay line in accordance with the present invention;

Figure 5 is a cross-sectional view taken along line 5-5 of Figure 4;

Figure 6 is a cross-sectional view taken along line 6*-6 of Figure 7 showing a still further embodiment of a delay line in accordance with the present invention;

Figure 7 is a bottom plan view of the delay line illustrated in Figure 6;

Figure 8 is a longitudinal cross-sectional View through a travelling wave tube utilizing a delay line in accordance with the present invention of the type illustrated in Figures 6 and 7; and

Figure 9 is a cross-sectional view taken along line 9-9 of Figure 8.

The so-called symmetrical nterdigital line is most advantageous for use in a travelling wave tube arrangement of the kind referred to. This form of line is illustrated in Figures l and 2 which are mutually perpendicular views of part of such a line.

As will be seen from Figures l and 2, which are respectively plan and longitudinal sections, such a line consists of two supports 1, 2 on which are disposed interleaved ngers 3, 4 for example metal bars or plates. In a travelling wave tube of the kind referred to, such a line may be disposed parallel to a plate 5, an electronic beam being injected into the space 6.

In the co-pending application of Warnecke and Gunard Serial No. 275,928, filed March l1, i952, an examination is made of the propagation of Waves in the zig-Zag guide path which is bounded by the fingers of such a line, and it is indicated that, for a certain direction of propagation of energy, there exists an infinity of waves being propagated at speeds such that their phase shift between the points 7 and 8 representing the centres of successive lengths of the zig-zag is given by the general expression:

\[/=g;-S1r+21rm (l) Where s is (to a close degree of approximation) the length of a linger, A is the wavelength in vacuo, and m any positive or negative whole number including 0.

It is likewise indicated in said co-pending application that it is advantageous to select for interaction with the electron beam, the fastest of the possible waves available 2 i. e. the wave corresponding to a phase angle ,lf which is as low as possible in absolute value. It follows from the Expression l that for a linger length of the order of M4, the lowest possible value of gb is of the order of for r11-:0, and the next higher value is of the order of for m=l. The positive sign here indicates that the wave is propagated in the same direction as the energy, and the negative sign indicates that the wave and the energy are being propagated in opposite directions. In View of the fact that in amplifiers, in which the energy is propagated in the direction of the beam, the interaction requires a component of positive sign, the symmetrical interdigital line is not advantageous for application to amplifers, because the first wave utilisable corresponding to the phase shift is not a predominating component, the greatest amount of energy being carried by the wave corresponding to the phase shift which is propagated in the undesirable negative direction. For this reason it is proposed in the aforesaid co-pending application to introduced into the line a dissymmetry which favours the wave of positive sign to the detriment of the fundamental wave of negative sign.

The present invention seeks to solve the problem thus raised in a different manner, without requiring the introduction of any dissymmetry into the line.

The invention is characterised in that the line is so constructed that outside the region of the beam, that is to say at the corners of the zig-zag guide formed between the fingers of the line, the wave passes through guide elements which introduce a positive or negative phase shift supplementary to the variation of phase undergone by the wave in the course of its propagation, that is to say behaving, at ultra-high frequencies, as the equivalents of reactive impedance elements.

The elements may be arranged to act as the equivalents either of inductances or of capacities and although the action is different in the two cases the linal effect obtained is the same. If a guide element in question behaves like an inductance, it is arranged to introduce a supplementary phase shift comprised between vr 371' "iand so that the phase shift of corresponding to the negative slow mode is brought between O and 1r. If the element behaves like a capacity it is arranged to introduce a phase shift between so that the phase shift of of the positive fast mode is brought between O and 1r. In

both cases there is therefore obtained a positive mode, the phase shift of which is between V and 1r, that is to say it corresponds to the lowest value possible, as is vention may be introduced into the zig-zag guide by simply moving apart the combs shown in Figure 1, in

suchmanner as to increase the distance between the ends of theV fingersendjthe supportef the opp'ositef'corn'b, as

shown in Figure 3. Here the finger length is made as 3/s)\, with a'distance of A/'S'between the ends of the vfingers and the support of the opposite comb. VThe space 13, 'the dimension of whichl measured in the V4direction of the width of the line isV less than M4,V behaves-.like an inductance inserted in series in the zig-zag' guide. -This dimension of the space 13 could be made-greater'than M 4, Yso as to .obtain the equivalent of 'a capacity,`butthis alternative is less advantageous, because 'for practical reasons of construction it is advantageousto/make the totalV line width as small as possible.

`VFigures 4 and 5 illustrate diagrammatical v embodiment. Here the fingers 3, 4 are iiXe'dmo'n V'supports 9, 10 having transverse "dimensions greater than those of the fingers and themselves fixed on the general supports 1, 2, Vso thatY the profile off-each lcomb thas a Y way there is obtained the equivalent of a considerable induCtance, with a relatively'fsrnall depth for the notches 11, 12. Y Y l Y In order to obtain betterseparationof the region `where the beam is injected from the regions where the" supplies mentary vphase shift is effected,V and in order 'to'rvreduele theV width of the line, it'niay bekof advantageto'bend the fingers of the line so that they YpenetrateV int'oj the' spaces equivalent Vto the phase-shifting circuits` at the`ends`1which are bent back "at right-angles t'othe plane-of thej line. A delay line arranged Vin this -wa`y is 'illustrated-*in vFig'- u'res 6` and 7.V Here the fingersv '15, 16,shown rby way of example as rectangular'bars' (Figure "Sis ar'cros'ssectionV andFigure 71a Vview from below), are vrembedded" in s'olid supports 17, '18 fixed on' 'a common plate 14. These fingers are bent back at9 and120", and' dipjaliternately Y into -the notcheslanfdprovided inathe supports 18 and 17k and constituting the 'e'quiva'lentof phaseashi'f'ting quadripoles sirn'ilarly't'o` the spaces' 1l3' and-Tlf in Figures 3 and 4. At 5 there has beerr'shown, "asini-figuresZandA 5, av parallel `electrode defining, together 'thejd'elay line, a space 6 into' which'tlrerbe'am' is injected, thefla'tt'er thus being well'insulated'from the phase-*shifting* regions 21 and 22:. i

Figure 8 illustrates in' longitudinalsection, jand'Fig-VY, ure 9 in section taken on' theline r9`-"9*in"Fi`gure 81a travelling wave tube having crossedmagnetic and electric fields and utilising a lineas'illustrated in Figures 6 and 7.

The Various elements are mounted in a vacuum-,tightV metal casing 31 ending at the righthndlendfinlazcollector Vanode 32. The coaxial Yinput Vline 27 for the ultra-high ly a further Y Y -ngerscor'nprisesa third portion perpendicular to the is injectedbetween the'elect-r'ode 5, Whichmaybe brought P to a high negative potential by the source 25, and the.

line 14 which may be connectedfto the ground connec- ,Vtion of the tube and thusbroug'ltf'ito zero D. C. potential so astoV create in the space'traversed by .the beam an electrostatic field the lines of force of "which run lparallel to the'plane of the drawingv'and at right-angles -t'o the trajectory of the beam Y29. 'A magnet, the pole-pieces 33,7.34jof whicli'lare` illustrated in Figure 9, createsv a Vmagnetic 'field the ylines of force of which fare perpendicular both to the beam and to the preceding electric Vfield.

Some of the fingers 15 of the delay line may, if desired, be made of resistive material, in order to introduce attenuation into the said line.

We claim: s y I 1. A Vtravelling'wave electron tube, comprising means for producing an electron beam, a delay line having two mutuallyIuncoupledextremities, traversed by an ultrahigh frequency travelling Wave and comprising a first supportrarid a s'ec'o'ndV support parallel toA one another and parallel to the-:mean trajectory of said beam', a series of parallel fingers .positioned between said supports and Ving support, so as to becapacitively coupled therewith,

thereby forming. an interdigitalstructure havingv ajlongitudinalsyrninetry plane in the direction of said beam.

2. A tuberas clainnedV in claim l, wherein said'supports are provided-withcavitieseach disposedbetween two adjacent fingers "carriedbyrthesarnesupport, s aid free extremities of fingers carried by s one support penetrating into respective cavities .provided inthe other support.

3. A. tube as claimed in `clairn 1s, Awherein each lof said 4. .A tubeas claimed i-n'clhaim '1,- wherein eachof said l 5. A delay line for a travelling wave tube oftlie type Y in which an electron beam moves inan interactionpsprace adjacent said line and -inenergy transfer relationship therewith, comprising a viirst. support and-Ya' second sup;

Vport for said delay line lessentially parallel t o eachother, a series of parallel iingers positioned between said sup-v ports, each of said fingers *beingV built so as v to have at least two mutually perpendicular portionsrLthveV first porrtion thereof being essentially perpendicular to the'plane VVof saidl supports andk the second portion thereof being es -V sentilallydparallell tosaidplane, the jextremities of said first portions ybeing alternately carried by'saidrfirst and second supports to thereby form a Vdelay .line 'of the :interdigitated` Ytypaa'ndY each vof isaid ngersY terminating with` the free eirtreniity thereof. positioned "adjacent and' spacedff'rinl the support opposite said first portionv carrying supportfthe'reof so` a's tobefcapacitively coupled there-V with, ythereby'formingan interdigital structure having Va longitudinal plane of symmetryi in the direction of said beam. 1

Referencesf Cited in iile' of.v this` patent' UNITED STATES kPATENTS

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