EP0407558B1 - Amplifier or oscillator device operating at ultrahigh frequency - Google Patents

Amplifier or oscillator device operating at ultrahigh frequency Download PDF

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Publication number
EP0407558B1
EP0407558B1 EP90902637A EP90902637A EP0407558B1 EP 0407558 B1 EP0407558 B1 EP 0407558B1 EP 90902637 A EP90902637 A EP 90902637A EP 90902637 A EP90902637 A EP 90902637A EP 0407558 B1 EP0407558 B1 EP 0407558B1
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Prior art keywords
electron beam
use according
circuit
output circuit
previous
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German (de)
French (fr)
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EP0407558A1 (en
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Guy Convert
Jean-Pierre Brasile
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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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J25/00—Transit-time tubes, e.g. klystrons, travelling-wave tubes, magnetrons
    • H01J25/74—Tubes specially designed to act as transit-time diode oscillators, e.g. monotrons

Definitions

  • the present invention relates to the use of a microwave amplifier device, as well as an oscillator obtained from the previous device.
  • speed modulation electronic tubes such as klystrons or traveling wave tubes.
  • This type of tube includes an electron gun, providing an electron beam; the electrons in the beam undergo a periodic change in speed which brings them together in packets in certain areas of space; these packets then excite by impulse, according to their own period, the oscillations of a microwave circuit (resonant cavity or line) by borrowing the energy necessary for their own kinetic energy.
  • Document FR-A-2,070,322 describes an example of such a tube.
  • vircators which, unlike the previous tubes, take advantage of the space charge effects.
  • a current of electrons is injected into a space, most often equal to several times the maximum current that could actually cross this space.
  • This virtual cathode is unstable, that is to say it oscillates in space, thus creating electromagnetic fields.
  • Document US-A-4,730,170 describes an example of such a vircator. With such a device, it is possible to obtain high microwave powers and this, under a reduced volume.
  • the signal transmitted is of poor quality, that is to say that the power is transmitted on numerous modes in a series of simultaneous or successive frequencies, and the applications of this type of signals are quite reduced.
  • the conversion efficiency is poor (of the order of 2 to 3% at best) compared to the efficiency which it is possible to obtain with speed modulation tubes (often greater than 40%).
  • the present invention relates to the use of a device intended to produce microwave energy from an electron beam, which makes it possible to avoid the above limitations, that is to say a yield of converting the energy of the electron beam into microwave energy and a quality of the emitted signal comparable to those of speed modulation tubes, with a weight and in a volume comparable to those of vircators.
  • the subject of the invention is the use of a microwave amplifier device as defined by claim 1.
  • FIG. 1 therefore represents a first embodiment of the device used according to the invention, seen in longitudinal schematic section.
  • the generator according to the invention is a structure of revolution around a longitudinal axis ZZ. It comprises an electron gun 1, formed by a cathode 11 and an anode composed of an armature 20 and a screen 21.
  • the cathode 11 is in the form of a conductive cylinder of axis ZZ, whose circumference protrudes 10 so that the electrons emitted by this cathode form an annular beam, represented by a dotted area 8 in the figure.
  • the direction of propagation of the electrons of the beam 8 is shown by arrows.
  • the armature 20 of the anode consists of a hollow cylinder, of the same axis ZZ as the cathode; it is closed by an annular shoulder 23 and a screen 21 in the form of a disc, leaving an annular slot 22 for the passage of the electron beam 8 to remain; the screen 21 is for example fixed by three tabs on the shoulder 23.
  • the generator used according to the invention also comprises an output microwave circuit 4 which is, in this embodiment, of the coaxial type, formed by an internal conductive cylinder 5 and an external conductor 40, arranged in the extension of the armature 20 , between which is defined an annular space 44.
  • the output circuit is substantially symmetrical of the electron gun 1 with respect to a plane normal to the plane of the figure, that is to say that the outer conductor 40 has a shoulder 43 annular and a screen 41 bearing, for example by legs, on the shoulder 43 and defining with this shoulder a circular slot 42 for the passage of the electron beam 8; the latter is received by an annular projection 50 of the inner conductor 5.
  • zone 3 Between the elements 21, 23 on the one hand, and 41, 43 on the other hand, there is a zone 3 called the injection region; this zone is laterally limited by extensions 25 and 45 of the walls 20 and 40 respectively, without contact with each other so as to form a slot 71 between them.
  • the generator according to the invention further comprises a microwave modulation circuit 7, which is in this embodiment of the coaxial type; the central conductor of the circuit is formed by the wall 40 and the external conductor by a wall 70 in the form of a hollow cylinder, always of axis ZZ, defining with the wall 40 an annular space 74, the outer conductor 70 coming to be connected to part 25 of the frame 20.
  • the application to the cathode 11 of a negative voltage with respect to that of the anode causes the emission of the annular electron beam 8.
  • the armature 20, the screen 21 and the elements of the output circuit 4 are at ground potential and a voltage -V o is applied to the cathode 11.
  • a longitudinal magnetic field (along the ZZ axis) is preferably applied to the structure, using means not shown, to focus the beam 8 thus produced.
  • the mechanism for forming a virtual cathode is recalled below. Inside an electron beam there is a charge of space: on the axis of the beam, the potential and the speed of the electrons are lower than at the periphery. If the density of electrons and consequently the transported current increase, the potential and the speed of the electrons decrease until zero: the electrons then form a heap, negatively charged, called virtual cathode.
  • This electron cluster oscillates on the longitudinal axis, giving rise to an electromagnetic field. The frequency of the oscillations depends in particular on the injection current and it is commonly measured in Gigahertz.
  • the maximum current intensity beyond which the electrons form a virtual cathode is a function of the potential of the electron beam as well as of the dimensions of the beam and of the injection region 3; more precisely, the maximum current for a given electron beam is lower when the injection zone 3 is of larger diameter.
  • the dimensions of the device (electron gun and injection zone) and the current of the electron beam are chosen so that it is slightly less than the maximum current likely to travel through region 3, current beyond which there is virtual cathode formation.
  • the modulation circuit 7 By the modulation circuit 7 is brought an alternating electric field.
  • the voltage between parts 25 and 45 resulting from this field must be of sufficient amplitude so that, for one of the alternations, the electron beam 8 is stopped by a mechanism of the virtual cathode type and no longer reaches the circuit.
  • outlet 4 the electrons then being absorbed by the walls delimiting the injection zone 3; at the next alternation, the voltage applied between the same elements 25 and 45 restores the beam; the beam current is thus modulated in intensity at the frequency of the modulation signal.
  • the output circuit 4 is then excited by the preceding modulated current and thus ensures the transformation into microwave energy of at least part of the energy of the electrons of the beam.
  • Screens 21 and 41 conventionally have the function of absorbing divergent electrons. It should be noted that the modulation (7) and output (4) microwave circuits make it possible, by the choice of their dimensions, to precisely define the frequency of the modulation signal and, which is the aim sought, the frequency of the signal. output, thus obtaining
  • the maximum period of the alternating modulation field may be only a fraction of the beam switching time between the on state and the virtual cathode; in practice it can be of the order of the transit time of the electrons in the structure.
  • the generator described here is, like a vircator, particularly compact; the length of the injection region 3, limited by the screens 21 and 41 happens to be in fact, in practice, of the order of the operating wavelength.
  • V o can pose technological problems due to the order of magnitude of the voltages (MV) and currents (kA) used. It is then possible to use voltage pulses, of a duration for example of the order of a hundred nanoseconds, transmitted to the cathode by the coaxial structure 12-20, for example. The duration of these pulses remains long compared to the period of the pulses produced, typically of the order of a hundred picoseconds.
  • the reinjection means can be produced by any known means, such as a coupling loop produced in an opening in the wall 40 or a circuit outside the generator shown.
  • FIG. 2 represents a second embodiment of the device used according to the invention, in which means are provided for post-acceleration of the beam after modulation, in order to improve the efficiency of the assembly.
  • the output circuit 4 is also formed as in FIG. 1 by the cylindrical inner conductor 5 surrounded by the conductor 40, the shoulder 43 and the screen 41.
  • the injection zone is no longer closed by the screen 21 and the shoulder 43 but by a conductive element 61 similar to the screen 41 and an external conductor 60, arranged in the extension of the armature 20 and providing with the latter the slot 71 to which the modulation circuit is connected; the element 60 also houses an annular slot 62 with the screen 61 to allow the passage of the electron beam 8.
  • the elements 60 and 61 are therefore electrically isolated both from the barrel 1 and from the output circuit 4.
  • a voltage -V o is applied to the cathode with respect to the anode, the modulation signal via circuit 7 and, in addition, a post-acceleration voltage + Vération at the output circuit. relative to the wall 60, which is for example at the potential of the anode. In this way, the electrons are accelerated out of the injection zone 3.
  • FIG. 3 represents a third embodiment of the device used according to the invention, in which the electron beam is a solid cylinder.
  • the emissive surface of the cathode, now marked 12, of the barrel 1 is in the form of a disc so as to emit a solid cylindrical electron beam 80.
  • the internal conductor of the output circuit 4, now marked 51 is constituted by a flat surface in the form of a disc.
  • the screens 21 and 41 of FIG. 1 have been replaced here by the elements marked 26 and 46, constituted by grids or metallic sheets sufficiently thin for their absorption of electrons to be very low.
  • the diameter of the cathode 12 must be substantially less than the wavelength of the energy. microwave obtained at the output, for example of the order of half the wavelength.

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Abstract

The invention provides for a device producing ultrahigh frequency energy from an electron beam. It mainly comprises: an electronic gun (1) producing an electron beam (8) in a so-called injection zone (3); modulating ultrahigh frequency circuitry (7) for superimposing an alternating voltage at a given frequency on a beam voltage within the injection zone, the amplitude of the said voltage being such that, in one of its alternations, it provides for transition between the passing state and the effective cathode state, thus causing modulation of the current carried by the electron beam; an output ultrahigh frequency circuitry (7), operating at the modulation signal frequency and driven by the aforesaid modulated current.

Description

La présente invention a pour objet l'utilisation d'un dispositif amplificateur d'ondes hyperfréquences, ainsi qu'un oscillateur obtenu à partir du dispositif précédent.The present invention relates to the use of a microwave amplifier device, as well as an oscillator obtained from the previous device.

Pour générer et amplifier des ondes hyperfréquences, il est connu d'utiliser notamment des tubes électroniques dits à modulation de vitesse, tels que klystrons ou tubes à ondes progressives. Ce type de tube comporte un canon à électrons, fournissant un faisceau d'électrons ; les électrons du faisceau subissent une modification périodique de vitesse qui entraîne leur regroupement en paquets dans certaines zones de l'espace ; ces paquets excitent alors par impulsion, suivant leur période propre, les oscillations d'un circuit hyperfréquence (cavité résonnante ou ligne) en empruntant l'énergie nécessaire à leur propre énergie cinétique. Le document FR-A-2.070.322 décrit un exemple d'un tel tube.To generate and amplify microwave waves, it is known to use in particular so-called speed modulation electronic tubes, such as klystrons or traveling wave tubes. This type of tube includes an electron gun, providing an electron beam; the electrons in the beam undergo a periodic change in speed which brings them together in packets in certain areas of space; these packets then excite by impulse, according to their own period, the oscillations of a microwave circuit (resonant cavity or line) by borrowing the energy necessary for their own kinetic energy. Document FR-A-2,070,322 describes an example of such a tube.

Dans les faisceaux d'électrons de tels tubes, les effets de la charge d'espace sont très importants. Ce sont en particulier eux qui fixent, pour des tensions données, une valeur maximale au courant qui peut être produit par le canon à électrons, ou encore qui peut être transporté dans un espace donné, pour un ensemble d'électrodes de géométrie donnée. Dans les tubes du type mentionné ci-dessus, pour obtenir des résultats satisfaisants en gain, rendement, qualité de signal, on est amené à limiter le courant transporté par le faisceau d'électrons à une intensité inférieure d'un ordre de grandeur au moins à l'intensité maximale. Par suite, et compte-tenu du principe même de la modulation de vitesse, ces tubes doivent utiliser des faisceaux longs, nécessitant le plus souvent une focalisation magnétique ; ces générateurs sont alors lourds et encombrants.In the electron beams of such tubes, the effects of space charge are very important. It is in particular them which fix, for given voltages, a maximum value for the current which can be produced by the electron gun, or which can be transported in a given space, for a set of electrodes of given geometry. In tubes of the type mentioned above, in order to obtain satisfactory results in gain, yield and signal quality, it is necessary to limit the current carried by the electron beam to a lower intensity of at least an order of magnitude. at maximum intensity. Consequently, and taking into account the very principle of speed modulation, these tubes must use long beams, most often requiring a magnetic focusing; these generators are then heavy and bulky.

On connaît également des dispositifs appelés vircators qui, contrairement aux tubes précédents, mettent à profit les effets de charge d'espace. Dans un vircator, on injecte dans un espace un courant d'électrons, égal le plus souvent à plusieurs fois le courant maximum qui pourrait effectivement franchir cet espace. Il y a alors accumulation des électrons, qui forment une cathode virtuelle. Cette cathode virtuelle est instable, c'est-à-dire qu'elle oscille dans l'espace, créant ainsi des champs électromagnétiques. Le document US-A-4.730.170 décrit un exemple d'un tel vircator. Avec un tel dispositif, il est possible d'obtenir des puissances hyperfréquences élevées et, ce, sous un volume réduit. Toutefois, on constate que le signal émis est de qualité médiocre, c'est-à-dire que la puissance est émise sur de nombreux modes en une suite de fréquences simultanées ou successives, et les applications de ce type de signaux sont assez réduites. Par ailleurs, le rendement de conversion est mauvais (de l'ordre de 2 à 3% au mieux) par rapport au rendement qu'il est possible d'obtenir avec des tubes à modulation de vitesse (souvent supérieurs à 40%).There are also known devices called vircators which, unlike the previous tubes, take advantage of the space charge effects. In a vircator, a current of electrons is injected into a space, most often equal to several times the maximum current that could actually cross this space. There is then an accumulation of electrons, which form a virtual cathode. This virtual cathode is unstable, that is to say it oscillates in space, thus creating electromagnetic fields. Document US-A-4,730,170 describes an example of such a vircator. With such a device, it is possible to obtain high microwave powers and this, under a reduced volume. However, it can be seen that the signal transmitted is of poor quality, that is to say that the power is transmitted on numerous modes in a series of simultaneous or successive frequencies, and the applications of this type of signals are quite reduced. Furthermore, the conversion efficiency is poor (of the order of 2 to 3% at best) compared to the efficiency which it is possible to obtain with speed modulation tubes (often greater than 40%).

La présente invention a pour objet l'utilisation d'un dispositif destiné à produire de l'énergie hyperfréquence à partir d'un faisceau d'électrons, qui permette d'éviter les limitations précédentes, c'est-à-dire un rendement de conversion de l'énergie du faisceau d'électrons en énergie hyperfréquence et une qualité du signal émis comparables à ceux des tubes à modulation de vitesse, avec un poids et dans un volume comparables à ceux des vircators.The present invention relates to the use of a device intended to produce microwave energy from an electron beam, which makes it possible to avoid the above limitations, that is to say a yield of converting the energy of the electron beam into microwave energy and a quality of the emitted signal comparable to those of speed modulation tubes, with a weight and in a volume comparable to those of vircators.

Plus précisément, l'invention a pour objet l'utilisation d'un dispositif amplificateur d'ondes hyperfréquences tel que défini par la revendication 1.More specifically, the subject of the invention is the use of a microwave amplifier device as defined by claim 1.

D'autres objets, particularités et résultats de l'invention ressortiront de la description suivante, donnée à titre d'exemple non limitatif et illustrée par les dessins annexés, qui représentent :

  • la figure 1, un premier mode de réalisation du dispositif utilisé selon l'invention ;
  • la figure 2, un second mode de réalisation du dispositif utilisé selon l'invention, dans lequel il comporte des moyens conférant au faisceau d'électrons une post-accélération ;
  • la figure 3, un troisième mode de réalisation du dispositif utilisé selon l'invention, dans lequel le faisceau d'électrons utilisé est un faisceau cylindrique plein.
Other objects, features and results of the invention will emerge from the following description, given by way of nonlimiting example and illustrated by the appended drawings, which represent:
  • Figure 1, a first embodiment of the device used according to the invention;
  • FIG. 2, a second embodiment of the device used according to the invention, in which it comprises means giving the electron beam post-acceleration;
  • FIG. 3, a third embodiment of the device used according to the invention, in which the electron beam used is a solid cylindrical beam.

Sur ces différentes figures, les mêmes références se rapportent aux mêmes éléments.In these different figures, the same references relate to the same elements.

La figure 1 représente donc un premier mode de réalisation du dispositif utilisé selon l'invention, vu en coupe schématique longitudinale.FIG. 1 therefore represents a first embodiment of the device used according to the invention, seen in longitudinal schematic section.

Le générateur selon l'invention est une structure de révolution autour d'un axe longitudinal ZZ. Il comporte un canon à électrons 1, formé d'une cathode 11 et d'une anode composée d'une armature 20 et d'un écran 21. La cathode 11 se présente sous la forme d'un cylindre conducteur d'axe ZZ, dont la circonférence fait une saillie 10 de façon à ce que les électrons émis par cette cathode forment un faisceau annulaire, représenté par une zone pointillée 8 sur la figure. On a représenté par des flèches le sens de propagation des électrons du faisceau 8. L'armature 20 de l'anode est constituée par un cylindre creux, de même axe ZZ que la cathode ; elle est fermée par un épaulement annulaire 23 et un écran 21 en forme de disque, laissant subsister une fente annulaire 22 pour le passage du faisceau d'électrons 8 ; l'écran 21 est par exemple fixé par trois pattes sur l'épaulement 23.The generator according to the invention is a structure of revolution around a longitudinal axis ZZ. It comprises an electron gun 1, formed by a cathode 11 and an anode composed of an armature 20 and a screen 21. The cathode 11 is in the form of a conductive cylinder of axis ZZ, whose circumference protrudes 10 so that the electrons emitted by this cathode form an annular beam, represented by a dotted area 8 in the figure. The direction of propagation of the electrons of the beam 8 is shown by arrows. The armature 20 of the anode consists of a hollow cylinder, of the same axis ZZ as the cathode; it is closed by an annular shoulder 23 and a screen 21 in the form of a disc, leaving an annular slot 22 for the passage of the electron beam 8 to remain; the screen 21 is for example fixed by three tabs on the shoulder 23.

Le générateur utilisé selon l'invention comporte encore un circuit hyperfréquence de sortie 4 qui est, dans ce mode de réalisation, de type coaxial, formé par un cylindre conducteur intérieur 5 et un conducteur extérieur 40, disposé dans le prolongement de l'armature 20, entre lesquels est défini un espace annulaire 44. Le circuit de sortie est sensiblement symétrique du canon d'électrons 1 par rapport à un plan normal au plan de la figure, c'est-à-dire que le conducteur extérieur 40 comporte un épaulement 43 annulaire et un écran 41 prenant appui, par exemple par des pattes, sur l'épaulement 43 et définissant avec cet épaulement une fente circulaire 42 pour le passage du faisceau électronique 8 ; ce dernier est reçu par une saillie annulaire 50 du conducteur intérieur 5.The generator used according to the invention also comprises an output microwave circuit 4 which is, in this embodiment, of the coaxial type, formed by an internal conductive cylinder 5 and an external conductor 40, arranged in the extension of the armature 20 , between which is defined an annular space 44. The output circuit is substantially symmetrical of the electron gun 1 with respect to a plane normal to the plane of the figure, that is to say that the outer conductor 40 has a shoulder 43 annular and a screen 41 bearing, for example by legs, on the shoulder 43 and defining with this shoulder a circular slot 42 for the passage of the electron beam 8; the latter is received by an annular projection 50 of the inner conductor 5.

Entre les éléments 21, 23 d'une part, et 41, 43 d'autre part, se situe une zone 3 dite région d'injection ; cette zone est limitée latéralement par des prolongements 25 et 45 des parois 20 et 40 respectivement, sans contact l'un avec l'autre de façon à ménager entre eux une fente 71.Between the elements 21, 23 on the one hand, and 41, 43 on the other hand, there is a zone 3 called the injection region; this zone is laterally limited by extensions 25 and 45 of the walls 20 and 40 respectively, without contact with each other so as to form a slot 71 between them.

Le générateur selon l'invention comporte en outre un circuit hyperfréquence de modulation 7, qui est dans ce mode de réalisation de type coaxial ; le conducteur central du circuit est formé par la paroi 40 et le conducteur extérieur par une paroi 70 en forme de cylindre creux, toujours d'axe ZZ, définissant avec la paroi 40 un espace annulaire 74, le conducteur extérieur 70 venant se raccorder a la partie 25 de l'armature 20.The generator according to the invention further comprises a microwave modulation circuit 7, which is in this embodiment of the coaxial type; the central conductor of the circuit is formed by the wall 40 and the external conductor by a wall 70 in the form of a hollow cylinder, always of axis ZZ, defining with the wall 40 an annular space 74, the outer conductor 70 coming to be connected to part 25 of the frame 20.

Le fonctionnement de ce dispositif est le suivant.The operation of this device is as follows.

L'application à la cathode 11 d'une tension négative par rapport à celle de l'anode provoque l'émission du faisceau d'électrons annulaire 8. A titre d'exemple, l'armature 20, l'écran 21 et les éléments du circuit de sortie 4 sont au potentiel de la masse et on applique à la cathode 11 une tension -Vo. On applique de préférence à la structure, à l'aide de moyens non représentés, un champ magnétique longitudinal (selon l'axe ZZ) pour focaliser le faisceau 8 ainsi produit.The application to the cathode 11 of a negative voltage with respect to that of the anode causes the emission of the annular electron beam 8. For example, the armature 20, the screen 21 and the elements of the output circuit 4 are at ground potential and a voltage -V o is applied to the cathode 11. A longitudinal magnetic field (along the ZZ axis) is preferably applied to the structure, using means not shown, to focus the beam 8 thus produced.

On rappelle ci-après le mécanisme de formation d'une cathode virtuelle. A l'intérieur d'un faisceau électronique existe une charge d'espace : sur l'axe du faisceau, le potentiel et la vitesse des électrons sont plus faibles qu'à la périphérie. Si la densité d'électrons et par suite le courant transporté augmentent, le potentiel et la vitesse des électrons diminuent jusqu'à zéro : les électrons forment alors un amas, chargé négativement, appelé cathode virtuelle. Cet amas d'électrons oscille sur l'axe longitudinal, donnant naissance à un champ électromagnétique. La fréquence des oscillations dépend notamment du courant d'injection et elle se mesure couramment en Gigahertz. Par ailleurs, l'intensité de courant maximale au-delà de laquelle les électrons forment une cathode virtuelle est fonction du potentiel du faisceau d'électrons ainsi que des dimensions du faisceau et de la région d'injection 3 ; plus précisément, le courant maximum pour un faisceau d'électrons donné est plus faible lorsque la zone d'injection 3 est de plus grand diamètre.The mechanism for forming a virtual cathode is recalled below. Inside an electron beam there is a charge of space: on the axis of the beam, the potential and the speed of the electrons are lower than at the periphery. If the density of electrons and consequently the transported current increase, the potential and the speed of the electrons decrease until zero: the electrons then form a heap, negatively charged, called virtual cathode. This electron cluster oscillates on the longitudinal axis, giving rise to an electromagnetic field. The frequency of the oscillations depends in particular on the injection current and it is commonly measured in Gigahertz. Furthermore, the maximum current intensity beyond which the electrons form a virtual cathode is a function of the potential of the electron beam as well as of the dimensions of the beam and of the injection region 3; more precisely, the maximum current for a given electron beam is lower when the injection zone 3 is of larger diameter.

Selon l'invention, on choisit les dimensions du dispositif (canon à électrons et zone d'injection) et le courant du faisceau d'électrons de sorte qu'il soit légèrement inférieur au courant maximum susceptible de parcourir la région 3, courant au-delà duquel il y a formation de cathode virtuelle.According to the invention, the dimensions of the device (electron gun and injection zone) and the current of the electron beam are chosen so that it is slightly less than the maximum current likely to travel through region 3, current beyond which there is virtual cathode formation.

Par le circuit de modulation 7 est amené un champ électrique alternatif. La tension entre les parties 25 et 45 résultant de ce champ doit être d'amplitude suffisante pour que, pour l'une des alternances, le faisceau d'électrons 8 soit stoppé par un mécanisme du type cathode virtuelle et n'atteigne plus le circuit de sortie 4, les électrons étant alors absorbés par les parois délimitant la zone d'injection 3 ; à l'alternance suivante, la tension appliquée entre les mêmes éléments 25 et 45 rétablit le faisceau ; le courant du faisceau se trouve ainsi modulé en intensité à la fréquence du signal de modulation. Le circuit de sortie 4 est alors excité par le courant modulé précédent et assure ainsi la transformation en énergie hyperfréquence d'une partie au moins de l'énergie des électrons du faisceau. Les écrans 21 et 41 ont classiquement pour fonction d'absorber les électrons divergents. Il est à noter que les circuits hyperfréquences de modulation (7) et de sortie (4) permettent, par le choix de leurs dimensions, de définir précisément la fréquence du signal de modulation et, ce qui est le but recherché, la fréquence du signal de sortie, permettant ainsi l'obtention d'un signal de bonne qualité.By the modulation circuit 7 is brought an alternating electric field. The voltage between parts 25 and 45 resulting from this field must be of sufficient amplitude so that, for one of the alternations, the electron beam 8 is stopped by a mechanism of the virtual cathode type and no longer reaches the circuit. outlet 4, the electrons then being absorbed by the walls delimiting the injection zone 3; at the next alternation, the voltage applied between the same elements 25 and 45 restores the beam; the beam current is thus modulated in intensity at the frequency of the modulation signal. The output circuit 4 is then excited by the preceding modulated current and thus ensures the transformation into microwave energy of at least part of the energy of the electrons of the beam. Screens 21 and 41 conventionally have the function of absorbing divergent electrons. It should be noted that the modulation (7) and output (4) microwave circuits make it possible, by the choice of their dimensions, to precisely define the frequency of the modulation signal and, which is the aim sought, the frequency of the signal. output, thus obtaining a good quality signal.

Il est à noter encore que, pour obtenir un fonctionnement satisfaisant, il n'est pas nécessaire de provoquer la formation complète d'une cathode virtuelle ; la période maximum du champ alternatif de modulation peut n'être qu'une fraction du temps de basculement du faisceau entre état passant et cathode virtuelle; en pratique elle peut être de l'ordre du temps de transit des électrons dans la structure. Le générateur décrit ici est, comme un vircator, particulièrement compact ; la longueur de la région d'injection 3, limitée par les écrans 21 et 41 se trouve être en effet, en pratique, de l'ordre de la longueur d'onde de fonctionnement.It should also be noted that, to obtain satisfactory operation, it is not necessary to cause the complete formation of a virtual cathode; the maximum period of the alternating modulation field may be only a fraction of the beam switching time between the on state and the virtual cathode; in practice it can be of the order of the transit time of the electrons in the structure. The generator described here is, like a vircator, particularly compact; the length of the injection region 3, limited by the screens 21 and 41 happens to be in fact, in practice, of the order of the operating wavelength.

Par ailleurs l'application d'une tension continue Vo peut poser des problèmes technologiques du fait de l'ordre de grandeur des tensions (MV) et courants (kA) utilisés. Il est alors possible d'utiliser des impulsions de tension, d'une durée par exemple de l'ordre de la centaine de nanosecondes, transmises à la cathode par la structure coaxiale 12-20, par exemple. La durée de ces impulsions reste longue par rapport à la période des impulsions produites, typiquement de l'ordre de la centaine de picosecondes.Furthermore, the application of a direct voltage V o can pose technological problems due to the order of magnitude of the voltages (MV) and currents (kA) used. It is then possible to use voltage pulses, of a duration for example of the order of a hundred nanoseconds, transmitted to the cathode by the coaxial structure 12-20, for example. The duration of these pulses remains long compared to the period of the pulses produced, typically of the order of a hundred picoseconds.

On a décrit ci-dessus un dispositif assurant l'amplification du signal fourni par le circuit de modulation. Comme il est bien connu, il est possible de réaliser avec cette structure un oscillateur, en lui ajoutant des moyens de réinjection dans le circuit de modulation d'une partie du signal fourni par le circuit de sortie et, ce, avec une phase convenable, qui est liée aux dimensions du circuit, ainsi qu'il est connu. Les moyens de réinjection peuvent être réalisés par tout moyen connu, tel que boucle de couplage réalisée dans une ouverture ménagée dans la paroi 40 ou circuit extérieur au générateur représenté.We have described above a device ensuring the amplification of the signal supplied by the modulation circuit. As is well known, it is possible to make an oscillator with this structure, by adding means to it for reinjection into the modulation circuit of part of the signal supplied by the output circuit, and this, with a suitable phase, which is related to the dimensions of the circuit, as is known. The reinjection means can be produced by any known means, such as a coupling loop produced in an opening in the wall 40 or a circuit outside the generator shown.

La figure 2 représente un deuxième mode de réalisation du dispositif utilisé selon l'invention, dans lequel sont prévus des moyens de post-accélération du faisceau après modulation, afin d'améliorer le rendement de l'ensemble.FIG. 2 represents a second embodiment of the device used according to the invention, in which means are provided for post-acceleration of the beam after modulation, in order to improve the efficiency of the assembly.

Sur cette figure, on retrouve le canon à électrons 1, le circuit de modulation 7 et le circuit de sortie 4, mais l'ensemble du circuit 4 a été isolé électriquement des éléments précédents.In this figure, we find the electron gun 1, the modulation circuit 7 and the output circuit 4, but the entire circuit 4 has been electrically isolated from the preceding elements.

Plus précisément, on retrouve le canon 1 identique à ce qui a été décrit figure 1, c'est-à-dire composé de la cathode 11, l'armature 20 et l'écran 21. Le circuit de sortie 4 est formé également comme sur la figure 1 par le conducteur intérieur cylindrique 5 entouré par le conducteur 40, l'épaulement 43 et l'écran 41. Toutefois, dans ce mode de réalisation, la zone d'injection n'est plus fermée par l'écran 21 et l'épaulement 43 mais par un élément conducteur 61 semblable à l'écran 41 et un conducteur 60 extérieur, disposé dans le prolongement de l'armature 20 et ménageant avec cette dernière la fente 71 à laquelle est connecté le circuit de modulation ; l'élément 60 ménage par ailleurs une fente annulaire 62 avec l'écran 61 pour permettre le passage du faisceau électronique 8. Les éléments 60 et 61 sont donc électriquement isolés tant du canon 1 que du circuit de sortie 4.More precisely, we find the barrel 1 identical to what has been described in FIG. 1, that is to say composed of the cathode 11, the armature 20 and the screen 21. The output circuit 4 is also formed as in FIG. 1 by the cylindrical inner conductor 5 surrounded by the conductor 40, the shoulder 43 and the screen 41. However, in this embodiment, the injection zone is no longer closed by the screen 21 and the shoulder 43 but by a conductive element 61 similar to the screen 41 and an external conductor 60, arranged in the extension of the armature 20 and providing with the latter the slot 71 to which the modulation circuit is connected; the element 60 also houses an annular slot 62 with the screen 61 to allow the passage of the electron beam 8. The elements 60 and 61 are therefore electrically isolated both from the barrel 1 and from the output circuit 4.

En fonctionnement, on applique comme précédemment une tension -Vo à la cathode par rapport à l'anode, le signal de modulation par l'intermédiaire du circuit 7 et, en outre, une tension +V₁ de post-accélération au circuit de sortie par rapport à la paroi 60, qui est par exemple au potentiel de l'anode. De la sorte est réalisée une accélération des électrons au sortir de la zone d'injection 3.In operation, as before, a voltage -V o is applied to the cathode with respect to the anode, the modulation signal via circuit 7 and, in addition, a post-acceleration voltage + Vération at the output circuit. relative to the wall 60, which is for example at the potential of the anode. In this way, the electrons are accelerated out of the injection zone 3.

La figure 3 représente un troisième mode de réalisation du dispositif utilisé selon l'invention, dans lequel le faisceau électronique est un cylindre plein.FIG. 3 represents a third embodiment of the device used according to the invention, in which the electron beam is a solid cylinder.

Sur cette figure, on retrouve à titre d'exemple les mêmes éléments que sur la figure 1, excepté la cathode du canon 1, le conducteur intérieur du circuit de sortie 4 et les écrans du canon et du circuit de sortie.In this figure, we find by way of example the same elements as in Figure 1, except for the cathode of the barrel 1, the inner conductor of the output circuit 4 and the screens of the barrel and of the output circuit.

Dans ce mode de réalisation, la surface émissive de la cathode, maintenant repérée 12, du canon 1 est en forme de disque de sorte à émettre un faisceau électronique cylindrique plein 80. De la même manière, le conducteur intérieur du circuit de sortie 4, maintenant repéré 51, est constitué par une surface plane en forme de disque. Les écrans 21 et 41 de la figure 1 ont été remplacés ici par les éléments repérés 26 et 46, constitués par des grilles ou des feuilles métalliques suffisamment minces pour que leur absorption d'électrons soit très faible.In this embodiment, the emissive surface of the cathode, now marked 12, of the barrel 1 is in the form of a disc so as to emit a solid cylindrical electron beam 80. In the same way, the internal conductor of the output circuit 4, now marked 51, is constituted by a flat surface in the form of a disc. The screens 21 and 41 of FIG. 1 have been replaced here by the elements marked 26 and 46, constituted by grids or metallic sheets sufficiently thin for their absorption of electrons to be very low.

Il est à noter que, pour qu'un fonctionnement satisfaisant puisse être obtenu, le diamètre de la cathode 12 doit être sensiblement inférieur à la longueur d'onde de l'énergie hyperfréquence obtenue en sortie, par exemple de l'ordre de la demi-longueur d'onde.It should be noted that, for satisfactory operation to be obtained, the diameter of the cathode 12 must be substantially less than the wavelength of the energy. microwave obtained at the output, for example of the order of half the wavelength.

La description faite ci-dessus l'a été bien entendu à titre d'exemple non limitatif. C'est ainsi, notamment, que différents circuits hyperfréquence ont été représentés comme étant de type coaxial mais sont remplaçables par des guides d'ondes.The description given above has been understood of course by way of nonlimiting example. Thus, in particular, that various microwave circuits have been shown to be of the coaxial type but can be replaced by waveguides.

Claims (9)

  1. Use of a UHF wave amplifier device, this device comprising in succession:
    - an electron gun, capable of producing an electron beam (8) in an injection region (3);
    - a UHF circuit called a modulation circuit (7), allowing an alternating voltage to be applied in the injection region;
    - an output UHF circuit (4) allowing at least some of the energy of the electrons in the beam to be converted into UHF energy,
    characterized in that,
    while the said device is in use, the current carried by the electron beam is less than the maximum current capable of being carried in the injection region, and that the abovementioned alternating voltage has an amplitude which is sufficient, during one of its half-cycles, to trigger the formation of a virtual cathode no longer allowing the electrons to pass, the current transported by the beam thus being modulated at the so-called modulation frequency of the alternating voltage, the output circuit being excited by the previous modulated current.
  2. Use according to Claim 1, characterized in that the output circuit is of the coaxial type.
  3. Use according to one of the previous claims, characterized in that the modulation circuit is of the coaxial type.
  4. Use according to Claims 2 and 3, characterized in that the central conductor (40) of the modulation circuit is constituted by the outer conductor of the output circuit.
  5. Use according to one of Claims 1 or 2, characterized in that the output circuit is electrically isolated from the injection region and in that an electron-accelerating voltage is applied between the injection region and the output circuit.
  6. Use according to one of the previous claims, characterized in that the electron beam is in the shape of a hollow cylinder.
  7. Use according to one of the previous claims, characterized in that the electron beam is in the shape of a solid cylinder.
  8. Use according to one of the previous claims, characterized in that it furthermore comprises means of reinjecting a part of the signal supplied by the output circuit into the modulation circuit thus forming an oscillator.
  9. Use according to one of the preceding claims, characterized in that it furthermore comprises means of applying a magnetic field for focussing the electron beam.
EP90902637A 1989-01-27 1990-01-26 Amplifier or oscillator device operating at ultrahigh frequency Expired - Lifetime EP0407558B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR8901007A FR2642584B1 (en) 1989-01-27 1989-01-27 AMPLIFIER OR OSCILLATOR DEVICE OPERATING IN MICROWAVE
FR8901007 1989-01-27
PCT/FR1990/000059 WO1990009029A1 (en) 1989-01-27 1990-01-26 Amplifier or oscillator device operating at ultrahigh frequency

Publications (2)

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EP0407558A1 EP0407558A1 (en) 1991-01-16
EP0407558B1 true EP0407558B1 (en) 1995-08-02

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US (1) US5164634A (en)
EP (1) EP0407558B1 (en)
JP (1) JPH03503818A (en)
CA (1) CA2026111C (en)
DE (1) DE69021290T2 (en)
FR (1) FR2642584B1 (en)
WO (1) WO1990009029A1 (en)

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FR2830371B1 (en) * 2001-09-28 2005-08-26 Thales Sa MICROWAVE WAVE GENERATOR WITH VIRTUAL CATHODE
SE532955C2 (en) * 2006-06-01 2010-05-18 Bae Systems Bofors Ab Microwave generating device
RU2444082C2 (en) * 2010-05-24 2012-02-27 Государственное образовательное учреждение высшего профессионального образования "Саратовский государственный университет им. Н.Г. Чернышевского" Generator of microwave signals on virtual cathode
RU2671915C2 (en) * 2017-12-14 2018-11-07 Александр Петрович Ишков Autoresonant ultra high frequency generator
CN113936982B (en) * 2021-08-23 2023-07-21 西北核技术研究所 Beam-regulated high-efficiency low-magnetic-field relativity backward wave tube

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US2252565A (en) * 1940-03-09 1941-08-12 Rca Corp Electron discharge device
US2428622A (en) * 1942-11-12 1947-10-07 Gen Electric Tuning and coupling means for highfrequency systems
DE975093C (en) * 1944-03-30 1961-08-10 Karl Dr Hausser Arrangement with a braking field tube for generating very short electrical waves
GB852421A (en) * 1956-02-21 1960-10-26 Vickers Electrical Co Ltd Improvements relating to velocity modulated electron discharge devices
FR2070322A5 (en) * 1969-12-01 1971-09-10 Thomson Csf
US4345220A (en) * 1980-02-12 1982-08-17 The United States Of America As Represented By The Secretary Of The Air Force High power microwave generator using relativistic electron beam in waveguide drift tube
US4422045A (en) * 1981-03-20 1983-12-20 Barnett Larry R Barnetron microwave amplifiers and oscillators
US4751429A (en) * 1986-05-15 1988-06-14 The United States Of America As Represented By The United States Department Of Energy High power microwave generator
US4745336A (en) * 1986-05-27 1988-05-17 Ga Technologies Inc. Microwave generation by virtual cathode with phase velocity matching
US4730170A (en) * 1987-03-31 1988-03-08 The United States Of America As Represented By The Department Of Energy Virtual cathode microwave generator having annular anode slit

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Publication number Publication date
US5164634A (en) 1992-11-17
WO1990009029A1 (en) 1990-08-09
JPH03503818A (en) 1991-08-22
FR2642584A1 (en) 1990-08-03
CA2026111A1 (en) 1990-07-28
DE69021290T2 (en) 1995-12-21
CA2026111C (en) 2000-05-30
FR2642584B1 (en) 1994-05-06
EP0407558A1 (en) 1991-01-16
DE69021290D1 (en) 1995-09-07

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