US3846665A - Velocity modulation tube with frequency multiplication for the continuous generation of high power outputs - Google Patents

Velocity modulation tube with frequency multiplication for the continuous generation of high power outputs Download PDF

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Publication number
US3846665A
US3846665A US00372757A US37275773A US3846665A US 3846665 A US3846665 A US 3846665A US 00372757 A US00372757 A US 00372757A US 37275773 A US37275773 A US 37275773A US 3846665 A US3846665 A US 3846665A
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frequency
resonator
resonators
velocity modulation
electron
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US00372757A
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English (en)
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G Firmain
G Faillon
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Thales SA
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Thomson CSF SA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J25/00—Transit-time tubes, e.g. klystrons, travelling-wave tubes, magnetrons
    • H01J25/02—Tubes with electron stream modulated in velocity or density in a modulator zone and thereafter giving up energy in an inducing zone, the zones being associated with one or more resonators
    • H01J25/10—Klystrons, i.e. tubes having two or more resonators, without reflection of the electron stream, and in which the stream is modulated mainly by velocity in the zone of the input resonator
    • H01J25/12—Klystrons, i.e. tubes having two or more resonators, without reflection of the electron stream, and in which the stream is modulated mainly by velocity in the zone of the input resonator with pencil-like electron stream in the axis of the resonators

Definitions

  • ABSTRACT The present invention relates to velocity modulation tubes operating by frequency multiplication.
  • the invention provides for the utilisation of that part of the beam, 170, in zone arranged between the cathode 101 and the plane of minimum section(plane p).
  • One of the resonators 111, located adjacent the anode 102 receives the wave of frequency f for multiplication, and the second 112, located near the point of convergence of the beam, collects the wave at the multiplied frequency nf,.
  • the object of the invention is constituted by highpower velocity modulation tubes operating by fre quency multiplication.
  • the tubes in accordance with the invention are furthermore capable of continuous operation in the sense which will be defined hereinafter.
  • the tubes in accordance with the invention produce radio waves of a frequency located at the top end of the microwave range, that is to say some tens to some hundreds of gigacycles per second.
  • Velocity modulation tubes also known as klystrons
  • Velocity modulation tubes have been used for many years now to generate very high frequency radio waves, in other words micro waves, within a frequency range within which the conventional valves, with electrodes, used up to that time could not operate.
  • An amplifier of this kind essentially comprises two electromagnetic cavities or resonators, consisting of hollow volumes delimited by a wall possessing good electrical conductivity, through both of which volumes there passes an electron beam propagating through a drift space without any electric field or equipotential between the two resonators.
  • a high frequency electromagnetic field develops within the volume of this cavity.
  • the electrons of the beam experience a modification or modulation of their velocity, which depends upon the intensity of the high frequency field at the instant at which the electrons appear at the modulator input, that is to say that there is a modification in velocity varying from one electron to the next, at the frequency of the high frequency field in the modulator.
  • This modulation is generally of small amplitude in relation to the high velocity of the electrons at input to the grouping cavity.
  • the electrons follow a trajectory through the drift space between the two cavities, where they drift with a substantially uniform motion, the faster ones catching up with the slower ones.
  • the velocity modulation experienced by the electrons in the modulator is thus converted into a density modulation: at the end of the drift space, the beam exhibits a density of electrons, practically all of the same velocity varying between that of packets or bunches, where said density is greater than that of the initial beam, uniform in density and velocity, and that of zones located between the packets" or the like, where said density is less than that of the initial beam.
  • the initially uniform beam thus, at the end of the drift space, has a component alternating at the frequency which was responsible for the formation of these packets," that is to say the frequency of the wave injected into the modulator.
  • the beam induces within the volume thereof an electromagnetic field at the same frequency as said wave.
  • the amplified high frequency wave is picked up in an element coupled to the collector.
  • the same tubes can equally well operate in a frequency multiplication mode, meaning that it is possible to pick up in the collector a wave of frequency nf, produced from a wave of frequency f, injected into the modulator, n being a whole number greater than unity.
  • the facility to achieve multiplication stems from the fact that at the end of the drift space the electron beam in a velocity modulation tube not only has an alternating component at the frequency of the wave injected into the modulator, but also afternating components at harmonics of this frequency, as a more detailed analysis of the operation of these tubes shows.
  • an electron-gun whose function is that of generating the electron beam, is generally made up of several electrodes chief among which are the cathode which is the electron source and an anode which, at a positive potential in relation to the cathode, creates an electric field under the effect of which the electrons are extracted from the cathode and then accelerated through the tube.
  • the majority of the electron guns utilised in velocity modulation tubes produce a beam whose diameter decreases from the cathode towards a point known as the maximum convergence or point of minimum cross-section, often located beyond the anode, and then increases beyond this point in the absence of any means outside the electron-gun to make it retain its minimum cross-sectional area.
  • the frequency f It can be said in effect, that this difficulty becomes the more severe, other things being equal, the higher the beam power and the greater the beam current density, that is to say the current per unit area of the beam cross-section.
  • the beam diameter at the level of the collector can hardly be more than 0.2 to 0.3 mm.
  • a power density of the order of several megawatts per square mm and a current density possibly having a magnitude measurable in thousands of amperes per cm are the result.
  • the electron beam is only utilised at its convergent portion, that is to say under conditions which require no focusing, this being so even in the case of a high power beam.
  • it is intended to convey that no means associated with the tube are provided in the path of the electrons, beyond said minimum cross-sectional area of the beam, in order to modify their trajectories as produced by the geometry of the electron-gun in which the electron beam is generated.
  • these means generally employ either a magnetic field directed substantially in accordance with the direction of propagation of the beam, or electric field gradients localised at a certain number of points distributed along the length of the trajectory of the beam.
  • a magnetic field directed substantially in accordance with the direction of propagation of the beam or electric field gradients localised at a certain number of points distributed along the length of the trajectory of the beam.
  • the modulator is arranged in the path of the beam, between the cathode and the point of convergence: the cross-sectional area of passage offered to the beam by this kind of modulator, which resonates at the frequency f makes it possible, without difficulty to arrange this modulator at the desired distance from the collector in order to achieve there a current density on the part of that alternating component of the beam which has a frequency nf corresponding to the optimum achievable in tubes of this kind.
  • the electron beam can also be operated within the tubes in accordance with the invention, over a short part of its length beyond said zone, still without any focusing.
  • FIG. 1 illustrates schematically and in section, a prior art velocity modulation tube.
  • One of the objects of this figure is in particular to show the general appearance of the electron beam in a prior art velocity modulation tube.
  • the tube shown in the figure is a two-cavity klystron amplifier all of the elements of which are solids of revolution about the axis XX.
  • a cathode l of spherical cap form made of an electron-emissive material or covered with a layer of electron-emissive substance and an anode 2 placed at a positive voltage V in relation to the cathode l by a voltage source 3.
  • a component 5 located in the neighbourhood of the cathode l, the function of which is to cause the beam to converge at exit from the cathode, towards the axis XX.
  • This component which may be a focusing electrode, is placed at a negative direct voltage in relation to the cathode, by the source 6.
  • the cathode 1, the focusing electrode 5 and the anode 2 constitute what is conventionally refered to as the electron-gun of the tube, which may also comprise other electrodes which have not been illustrated heresince they are not essential to the considerations which follow.
  • the cathode Under the joint action of the anode 2 and the focusing electrode 5, the cathode, when subjected to the conditions required for emission, produces a beam of electrons 7 (area covered with thin lines) converging towards the axis XX of the tube and directed towards the right, considering the figure.
  • the focusing device 8 located beyond the anode and producing a magnetic field which is constant with time and directed towards the axis XX, gives the beam a virtually constant crosssectional area over a large part of its trajectory towards an electron collector which is at a positive potential in relation to the cathode and marked 4 in the figure.
  • This electron collector is connected, like the anode 2, to the positive terminal of the source 3 in the example shown in the figure.
  • T and T in FIG. 1, represent the trajectories of two electrons located at the periphery of the beam; the trajectories of all the other electrons of the beam, some of which have been partially illustrated, are comprised within the volume whose section through the plane of the figure, is limited by the cathode and these two trajectories.
  • three zones can be distinguished, namely the zone 70 roughly delimited to the right of the cathode by the anode 2 in the example of the figure, where the beam issuing from the cathode converges to a minimum section, followed by a zone 71 along which the focusing elements 8 are located and where the beam has a cylindrical form with a section roughly equal to the preceding section, followed in turn by a zone 72 in which the beam diverges towards the electron collector 4.
  • the electron beam does not converge towards a point although in the foregoing description mention has been made of a point of convergence.
  • a beam never converges strictly to a point instead its section simply diminishing to a minimum value which, in the case of the figure, is located at the end of the zone 70.
  • References 14 and 16 respectively represent, within the amplifier klystron shown in the figure, the means used to couple the modulator 11 to the source supplying the wave which is to be amplified, and the means used to couple the collector 1'2 with the load picking up the amplified wave.
  • the field-free space 9 in the figure is generally the internal space within a tube 13 made of an electrically conductive material placed at a positive potential in relation to the cathode, in this case connected to the positive terminal of the source 3.
  • the anode 2, the electron collector 4, the tube 13 and the resonators 11 and 12 are an integral part of a single mechanical component so that a single connection suffices to establish the potential conditions defined hereinbefore.
  • FIG. 2 illustrates in schematic section a velocity modulation tube of frequency multiplication kind, in accordance with the invention.
  • this is a tube all the constituent elements of which are solids of revolution about the axis XX, with the exception of the coupling wave guides associated with the resonators.
  • FIG. 2 as in the following figures, only that half of the tube located above the axis XX has been shown.
  • FIG. 2 within the evacuated closure 10, there can again be seen, albeit with slightly different shapes, a certain number of the elements of FIG. 1 including the cathode 101, the anode 102, the focusing electrode 105, the resonators 111 and 112 having no grids, the tube 113 and the trajectory T of a peripheral electron of the beam. From this figure, it will be seen that the electron beam 107, which is not subjected to the action of any focusing element but controlled simply by the electrodes of the tube, has a different shape to that encountered in the prior art tubes, of which FIG. 1 provides an example.
  • the resonators 111 and 112 are located in the trajectory of the electron beam as indicated in the figure, that is to say the former at the level of the anode 2 of which, in the particular example chosen, it is an integral part, and the latter at the level of the point where the beam has the minimum section of radius b.
  • the resonator 111 receives the wave of frequency f, through the medium of the coupling element 114, coupling the resonator 111 with said source, and velocity modulates the electrons of the beam.
  • the conversion of the velocity modulation to density modulation takes place along the drift space inside the tube 113.
  • theelectron beam current has an alternating component of frequency nf, which induces in the resonator 112 a wave of frequency nf,.
  • the coupling element 116 directs this wave to a load (not shown) in the manner indicated by the arrow.
  • the coupling elements 114 and 116 are waveguide sections, the cross-section through which has been illustrated in the plane of the figure.
  • M indicates the coupling factor between the electron beam and the collector
  • (In/210) the standarised alternating component of the beam current at frequency nfr, the first degree n'" order Bessel function of which .
  • In (nr) represents a good approximation
  • a is a coefficient expressing the condition of nonreflection of the electrons on passage into the collector, that is to say the limit which must not be exceeded by the voltage induced by the beam across the collector terminals, if the slowest electrons of the beam are not to be reflected back in the opposite direction to the direction of propagation of the beam.
  • r represents the degree of grouping which is the product of the modulation depth and the length of the drift tube measured in terms of transit angle.
  • J (Sr) is a maximum for r L28, this maximum being 0.37.
  • r is 1.28 and 1,, (nr) may be taken equal to 0.30 for example.
  • FIGS. 3, 4 and 5 illustrate variant embodiments of the velocity modulation tubes in accordance with the invention, in which:
  • FIG. 3 a third resonator 200 is arranged in the trajectory of the beam, beyond the collector.
  • the resonator 111 receives the wave of frequency f, from the resonator 200 to which it is coupled by the device 201.
  • the tube operates as a self excited oscillator.
  • FIG. 4 a resonator 300 resonating at a frequency intermediate between f and nf, is arranged in the trajec- 65 quencies f and nf,.
  • FIG. 5 the electron collector 104, insulated from the anode 102, is depressed, i.e. placed at a potential in relation to said cathode, which is less than that of the anode 102.
  • FIG. 6 is a variant embodiment differing from that of FIG. 2 in that the resonator 112 is a dual resonator formed by two identical attached portions 120, 121 along the wall 122, coupled with one another through an opening 123 in the wall.
  • a high power velocity modulation tube operating by frequency multiplication, for the production of a high frequency radio wave at a frequency nf from a high frequency radio wave of frequency f n being an integer greater than unity, said tube comprising:
  • At least two electromagnetic high-frequency resonators arranged in the path of the beam, through which the beam passes, separated by a space along which the electrons of the beam propagate with constant velocity, one of said resonators known as the first resonator, resonating at the frequency f, and velocity modulating the electrons of the beam, being located close to the cathode of said electron gun while one of the other of said resonators known as the second resonator, is arranged adjacent the said miminum cross-section of the beam, the aperture of said second resonator through which the beam passes being of dimensions which are small enough to provide coupling of said second resonator with the beam in the absence of grids in said resonator in the path of the beam, said second resonator which resonates at the frequency nf,, picking up the high frequency wave generated at frequency nf and directing it towards a load coupled to said resonator.
  • a velocity modulation tube according to claim 1, wherein said said second resonator is a dual resonator constituted by two portions similar one to one another, one of which is coupled to said load and which are attached along a common wall and coupled with one another through an opening in the wall.
  • a velocity modulation tube wherein said first resonator receives the power at frequency f from a third electromagnetic resonator resonating at this frequency and arranged in the trajectory of the beam beyond the second resonator, and connected furthermore by coupling means to said first resonator.
  • a velocity modulation tube comprising one or more further electromagnetic resonators arranged between the first and second resonators and traversed by the beam, these resonators resonating at a harmonic of the frequency f,, which harmonic has a frequency somewhere between the fre-

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US00372757A 1972-06-27 1973-06-22 Velocity modulation tube with frequency multiplication for the continuous generation of high power outputs Expired - Lifetime US3846665A (en)

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FR7223173A FR2191253B1 (ja) 1972-06-27 1972-06-27

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US (1) US3846665A (ja)
JP (1) JPS4959566A (ja)
DE (1) DE2332756A1 (ja)
FR (1) FR2191253B1 (ja)
GB (1) GB1394044A (ja)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5838107A (en) * 1995-07-28 1998-11-17 Thomson Tubes Electroniques Multiple-beam electron tube with cavity/beam coupling via drift tubes having facing lips
US6025678A (en) * 1996-12-10 2000-02-15 Thomson Tubes Electroniques Linear-beam microwave tube with output cavity beyond the collector
US6147447A (en) * 1997-06-13 2000-11-14 Thomson Tubes Electroniques Electronic gun for multibeam electron tube and multibeam electron tube with the electron gun
US6486605B1 (en) 1998-07-03 2002-11-26 Thomson Tubes Electroniques Multibeam electronic tube with magnetic field for correcting beam trajectory
US20020180275A1 (en) * 1999-12-30 2002-12-05 Georges Faillon Microwave pulse generator incorporating a pulse compressor

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2579480A (en) * 1947-08-26 1951-12-25 Sperry Corp Ultrahigh-frequency electron discharge apparatus
US3172005A (en) * 1960-01-08 1965-03-02 Philips Corp Beam convergence in velocitymodulating valve
US3354348A (en) * 1963-03-05 1967-11-21 Philips Corp Harmonic producing velocity modulation tube having particular output cavity structure
US3368104A (en) * 1964-03-17 1968-02-06 Varian Associates Electron beam tube included depressed collector therefor
US3522469A (en) * 1968-04-12 1970-08-04 Varian Associates Magnetic beam focusing structure for a traveling wave tube employing magnetic shunts between the pole pieces and the emitter
US3594606A (en) * 1970-04-15 1971-07-20 Varian Associates Velocity modulation tube employing cascaded harmonic prebunching
US3622834A (en) * 1970-04-15 1971-11-23 Varian Associates High-efficiency velocity modulation tube employing harmonic prebunching

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2305883A (en) * 1940-07-13 1942-12-22 Int Standard Electric Corp Frequency multiplier
FR961000A (ja) * 1945-09-22 1950-04-28
US2562927A (en) * 1946-12-28 1951-08-07 Sperry Corp Ultra high frequency discharge tube
US2747129A (en) * 1952-04-16 1956-05-22 Ludwig J Mayer Frequency multiplier
FR1384474A (fr) * 1963-03-05 1965-01-04 Philips Nv Dispositif pour engendrer un harmonique d'une vibration électro-magnétique à fréquence élevée
US3453482A (en) * 1966-12-22 1969-07-01 Varian Associates Efficient high power beam tube employing a fly-trap beam collector having a focus electrode structure at the mouth thereof

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2579480A (en) * 1947-08-26 1951-12-25 Sperry Corp Ultrahigh-frequency electron discharge apparatus
US3172005A (en) * 1960-01-08 1965-03-02 Philips Corp Beam convergence in velocitymodulating valve
US3354348A (en) * 1963-03-05 1967-11-21 Philips Corp Harmonic producing velocity modulation tube having particular output cavity structure
US3368104A (en) * 1964-03-17 1968-02-06 Varian Associates Electron beam tube included depressed collector therefor
US3522469A (en) * 1968-04-12 1970-08-04 Varian Associates Magnetic beam focusing structure for a traveling wave tube employing magnetic shunts between the pole pieces and the emitter
US3594606A (en) * 1970-04-15 1971-07-20 Varian Associates Velocity modulation tube employing cascaded harmonic prebunching
US3622834A (en) * 1970-04-15 1971-11-23 Varian Associates High-efficiency velocity modulation tube employing harmonic prebunching

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5838107A (en) * 1995-07-28 1998-11-17 Thomson Tubes Electroniques Multiple-beam electron tube with cavity/beam coupling via drift tubes having facing lips
US6025678A (en) * 1996-12-10 2000-02-15 Thomson Tubes Electroniques Linear-beam microwave tube with output cavity beyond the collector
US6147447A (en) * 1997-06-13 2000-11-14 Thomson Tubes Electroniques Electronic gun for multibeam electron tube and multibeam electron tube with the electron gun
US6486605B1 (en) 1998-07-03 2002-11-26 Thomson Tubes Electroniques Multibeam electronic tube with magnetic field for correcting beam trajectory
US20020180275A1 (en) * 1999-12-30 2002-12-05 Georges Faillon Microwave pulse generator incorporating a pulse compressor

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GB1394044A (en) 1975-05-14
DE2332756A1 (de) 1974-01-17
FR2191253B1 (ja) 1978-03-03
JPS4959566A (ja) 1974-06-10
FR2191253A1 (ja) 1974-02-01

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