EP0413018B1 - Hyperfrequency wave generator device with virtual cathode - Google Patents

Hyperfrequency wave generator device with virtual cathode Download PDF

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Publication number
EP0413018B1
EP0413018B1 EP90903856A EP90903856A EP0413018B1 EP 0413018 B1 EP0413018 B1 EP 0413018B1 EP 90903856 A EP90903856 A EP 90903856A EP 90903856 A EP90903856 A EP 90903856A EP 0413018 B1 EP0413018 B1 EP 0413018B1
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EP
European Patent Office
Prior art keywords
electrons
cathode
virtual cathode
output circuit
energy
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German (de)
French (fr)
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EP0413018A1 (en
Inventor
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 a microwave generator device using the virtual cathode phenomenon.
  • vircators To generate microwave waves, it is known in particular to use devices called vircators, as described for example in document US-A-4,730,170, which take advantage of the space charge effects existing in beams of electrons produced by the barrel of an electron tube. Indeed, as is known, it is these effects which fix, for given voltages, a maximum value of the current which can be produced by an electron gun, or which can be transported in a given space for a set electrodes of given geometry. In a vircator, a current of electrons is injected into a defined space, most often several times the maximum current that could actually cross this space.
  • a virtual cathode which causes the reflection of a more or less large fraction of the electrons in the beam.
  • This virtual cathode is unstable, that is to say that the amplitude of its potential trough and its position oscillate, causing a periodic variation in the number of electrons reflected or transmitted.
  • Such a device makes it possible to create electromagnetic fields with high microwave powers and under a reduced volume.
  • the signal transmitted is of poor quality, that is to say that the power is transmitted in numerous modes in a series of simultaneous or successive frequencies.
  • the present invention relates to a microwave generator which uses the phenomenon of oscillating virtual cathode but which makes it possible to obtain microwave energy of better spectral quality and with a better conversion efficiency than conventional vircators.
  • the subject of the invention is a device generating microwave waves as defined by claim 1.
  • FIG. 1 therefore represents a first embodiment of a device according to the prior art, seen in longitudinal schematic section.
  • This generator is a structure of revolution around a longitudinal axis ZZ.
  • the cathode 11 is in the form of a conductive cylinder with axis ZZ the circumference of which projects 10, so that the electrons emitted by this cathode form an annular beam, represented by a dotted area 8 in the figure.
  • 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.
  • the screen 21 is for example fixed by three tabs (not shown) on the shoulder 23.
  • the known generator also includes an output microwave circuit 4 which is, in this embodiment, of the coaxial type; it is formed by an inner conductive cylinder 5 and an outer conductor constituted by the extension of the armature 20, between which an annular space 44 is defined.
  • the output circuit is substantially symmetrical of the electron gun 1 with respect to a normal plane in the plane of the figure, that is to say that the external conductor has an annular shoulder 43 and a screen 41 bearing for example by legs on the shoulder 43 and defining with this shoulder a circular slot 42 for passage electrons from the beam 8.
  • the latter is received by an annular projection 50 of the inner conductor 5.
  • the drawings of the output circuit 4 and of the barrel 1 are such that the two impedances are close.
  • This zone is bounded laterally by the wall 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 -V0 is applied to the cathode 11.
  • the parameters are chosen so that a virtual cathode 80 is formed in the injection region 3.
  • the electrons transmitted by the virtual cathode 80 are represented by an arrow 82 and the electrons reflected by this cathode by arrows 81 Virtual.
  • 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 smaller than at the periphery of this beam. If the density of electrons and, consequently, the current transport increase, the potential and the speed of the electrons decrease until reaching zero: the electrons then form a negatively charged cluster, forming a well of potential called virtual cathode.
  • This virtual cathode oscillates and the frequency of the oscillations depends in particular on the injection current; 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: the maximum current for a given electron beam is weaker when the injection area 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 greater than the maximum current likely to flow through region 3, thus causing the formation of a virtual cathode.
  • the electrons transmitted represent a current modulated at the frequency of oscillation of the virtual cathode.
  • the energy produced is transmitted by the coaxial output circuit 4 to the outside.
  • the fact of using, according to the invention, separately the transmitted and reflected electrons has the effect of allowing the realization of a closer coupling between electrons, and output circuit and, consequently, obtaining electromagnetic energy of better spectral quality.
  • An alternative embodiment (not shown) consists in placing the output circuit 4 so that only the electrons reflected by the virtual cathode are used.
  • the dimensions of the barrel and of the injection region are preferably chosen so that the beam current is greater than, but close to the maximum current, so that the transmitted current is on average a fraction. significant of the total current injected into the injection region.
  • FIG. 2 shows the device of Figure 1, which further comprises means for post-acceleration of the electrons used, also seen in longitudinal schematic section.
  • FIG. 3 represents a first embodiment of the generator according to the invention, in which both the transmitted electrons and the electrons reflected by the virtual cathode are used.
  • the electron gun 1 formed by the cathode 11 and the anode 20, 21.
  • the gun 1 produces, here too, an electron beam 8 under conditions such that there is formation of a virtual cathode 80 with reflection (arrows 81) of a part of the electrons and transmission (arrow 82) of another part of the electrons towards, for example, a metal wall 50 delimiting the injection region 3.
  • the output microwave circuit 4 has two channels: one leads into a region marked 4A, between the anode 20 and the virtual cathode 80 and intended to recover the energy of the reflected electrons 81; the other opens into a region marked 4B, between the virtual cathode 80 and the wall 50 and it is intended to recover the energy of transmitted electrons 82.
  • phase shifter 45 which can be produced by any known means and connected on one of the channels, 4A or 4B, before the energies existing in the two channels combine to form the output energy.
  • the wall 46 between the channels 4A and 4B, must be of sufficient thickness to prevent the fields present in the two channels from coupling before the virtual cathode 80, this thickness being of the order of magnitude of the distance from wall 46 to the virtual cathode.
  • FIG. 3 shows a particular embodiment of the circuit 4.
  • Other variants are of course possible, which consist, for example, of producing, for each of the channels 4A and 4B, a structure of coaxial type as described Figure 1 for circuit 4.
  • FIG. 4 represents another embodiment of the device according to the invention, in which the beam produced by the electron gun is a solid cylinder, always seen in schematic longitudinal section.
  • FIG. 1 there is a structure similar to that of FIG. 1, except that 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 88.
  • 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 elements, marked 26 and 46, constituted by grids or metallic sheets sufficiently thin for their absorption of electrons to be very low.
  • this device is analogous to what has been described for FIG. 1, with the formation of a virtual cathode 83, reflected electrons 84 and transmitted electrons 85 whose kinetic energy is converted into microwave energy by the output circuit 4 .
  • the diameter of the cathode 12 must be substantially less than the wavelength of the microwave energy obtained at the output, for example of the order of half -wave length.
  • cathodes of larger diameter are usable, since the electrons tend to group around the periphery of the virtual cathode.
  • FIG. 5 represents another embodiment of the generator according to the invention, in which the electron beam used is a solid cylindrical beam and in which the generator further comprises post-acceleration means.
  • FIG. 6 represents an embodiment similar to that of FIG. 3, but in which the annular electron beam is replaced by a solid cylindrical electron beam.

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Abstract

The invention relates to a hyperfrequency wave generator which uses an electron beam and the phenomenon of oscillating virtual cathode, but which allows to obtain a spectral quality energy and a conversion yield which are improved with respect to conventional vircator generators. This is achieved by using separately the electrons issued from the virtual cathode (80), that is to say transmitted (82) or reflected (81), in order to transform their kinetic energy into hyperfrequency energy (4).

Description

La présente invention a pour objet un dispositif générateur d'ondes hyperfréquences utilisant le phénomène de cathode virtuelle.The present invention relates to a microwave generator device using the virtual cathode phenomenon.

Pour engendrer des ondes hyperfréquences, il est connu notamment d'utiliser des dispositifs appelés vircators, comme décrit par exemple dans le document US-A-4.730.170, qui mettent à profit les effets de charge d'espace existant dans des faisceaux d'électrons produits par le canon d'un tube électronique. En effet, ainsi qu'il est connu, ce sont ces effets qui fixent, pour des tensions données, une valeur maximale au courant qui peut être produit par un canon à électrons, ou encore qui peut être transporté dans un espace donné pour un ensemble d'électrodes de géométrie donnée. Dans un vircator, on injecte dans un espace défini 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 un puits de potentiel, appelé cathode virtuelle, et qui provoque la réflexion d'une fraction plus ou moins importante des électrons du faisceau. Cette cathode virtuelle est instable, c'est-à-dire que l'amplitude de son creux de potentiel et sa position oscillent, entraînant une variation périodique du nombre des électrons réfléchis ou transmis. Un tel dispositif permet de créer des champs électromagnétiques avec des puissances hyperfréquences élevées et 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. Le document 1983 IEEE International Conference on Plasma Science, 23-25 mai 1983, San Diego, California, IEEE Conference Record - Abstracts, IEEE, (New-York, US), T.J.T. Kwan et al. : "microwave generation by virtual cathodes and reflexing systems", page 40, résumé 2D6, rapporte une étude par simulation des signaux émis qui montre qu'ils le sont sur deux fréquences distinctes, l'une qui correspond à l'oscillation de la cathode virtuelle et, l'autre, aux électrons réfléchis entre la cathode réelle et la cathode virtuelle. Les applications de ce type de signaux s'en trouvent 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 d'autres générateurs, tels que les tubes électroniques à modulation de vitesse conventionnels.To generate microwave waves, it is known in particular to use devices called vircators, as described for example in document US-A-4,730,170, which take advantage of the space charge effects existing in beams of electrons produced by the barrel of an electron tube. Indeed, as is known, it is these effects which fix, for given voltages, a maximum value of the current which can be produced by an electron gun, or which can be transported in a given space for a set electrodes of given geometry. In a vircator, a current of electrons is injected into a defined space, most often several times the maximum current that could actually cross this space. There is then an accumulation of electrons which form a potential well, called a virtual cathode, and which causes the reflection of a more or less large fraction of the electrons in the beam. This virtual cathode is unstable, that is to say that the amplitude of its potential trough and its position oscillate, causing a periodic variation in the number of electrons reflected or transmitted. Such a device makes it possible to create electromagnetic fields with high microwave powers and 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 in numerous modes in a series of simultaneous or successive frequencies. The document 1983 IEEE International Conference on Plasma Science, 23-25 May 1983, San Diego, California, IEEE Conference Record - Abstracts, IEEE, (New-York, US), TJT Kwan et al. : "microwave generation by virtual cathodes and reflexing systems", page 40, 2D6 summary, reports a study by simulation of the emitted signals which shows that they are emitted on two distinct frequencies, one which corresponds to the oscillation of the cathode the other, to the electrons reflected between the real cathode and the virtual cathode. The applications of this type of signal are therefore 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 other generators, such as conventional speed modulation electronic tubes. .

La présente invention a pour objet un générateur d'ondes hyperfréquences qui utilise le phénomène de cathode virtuelle oscillante mais qui permette d'obtenir une énergie hyperfréquence de meilleure qualité spectrale et avec un meilleur rendement de conversion que les vircators classiques.The present invention relates to a microwave generator which uses the phenomenon of oscillating virtual cathode but which makes it possible to obtain microwave energy of better spectral quality and with a better conversion efficiency than conventional vircators.

Plus précisément, l'invention a pour objet un dispositif générateur d'ondes hyperfréquences tel que défini par la revendication 1.More specifically, the subject of the invention is a device generating microwave waves 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 figures annexées, qui représentent :

  • la figure 1, un mode de réalisation d'un dispositif générateur selon l'art antérieur, dans lequel le circuit hyperfréquence de sortie utilise les électrons transmis par la cathode virtuelle ;
  • la figure 2, le dispositif de la figure précédente, dans lequel le circuit hyperfréquence de sortie assure en outre une post-accélération des électrons utilisés ;
  • la figure 3, un autre mode de réalisation du dispositif selon l'invention, dans lequel le circuit hyperfréquence de sortie utilise d'une part les électrons transmis par la cathode virtuelle et, d'autre part, les électrons réfléchis par cette cathode virtuelle mais convenablement déphasés ;
  • les figures 4, 5 et 6 représentent des variantes des modes de réalisation précédents dans lesquelles le faisceau électronique présente une section différente.
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 figures, which represent:
  • Figure 1, an embodiment of a generator device according to the prior art, in which the circuit output microwave uses the electrons transmitted by the virtual cathode;
  • Figure 2, the device of the previous figure, wherein the output microwave circuit further provides post-acceleration of the electrons used;
  • FIG. 3, another embodiment of the device according to the invention, in which the output microwave circuit uses on the one hand the electrons transmitted by the virtual cathode and, on the other hand, the electrons reflected by this virtual cathode but suitably out of phase;
  • Figures 4, 5 and 6 show variants of the previous embodiments in which the electron beam has a different section.

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 d'un dispositif selon l'art antérieur, vu en coupe schématique longitudinale.FIG. 1 therefore represents a first embodiment of a device according to the prior art, seen in longitudinal schematic section.

Ce générateur est une structure de révolution autour d'un axe longitudinal ZZ.This generator is a structure of revolution around a longitudinal axis 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. 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 (non représentées) sur l'épaulement 23.It comprises an electron gun 1, formed by a cathode 11 and an anode, composed of a frame 20 and a screen 21. The cathode 11 is in the form of a conductive cylinder with axis ZZ the circumference of which projects 10, so that the electrons emitted by this cathode form an annular beam, represented by a dotted area 8 in the figure. 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. The screen 21 is for example fixed by three tabs (not shown) on the shoulder 23.

Le générateur connu comporte encore un circuit hyperfréquence de sortie 4 qui est, dans ce mode de réalisation, de type coaxial; il est formé par un cylindre conducteur intérieur 5 et un conducteur extérieur constitué par le prolongement de l'armature 20, entre lesquels est défini un espace annulaire 44. Le circuit de sortie est sensiblement symétrique du canon à électrons 1 par rapport à un plan normal au plan de la figure, c'est-à-dire que le conducteur extérieur 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 des électrons du faisceau 8. Ce dernier est reçu par une saillie annulaire 50 du conducteur intérieur 5. Plus généralement, les dessins du circuit de sortie 4 et du canon 1 sont tels que les deux impédances soient voisines.The known generator also includes an output microwave circuit 4 which is, in this embodiment, of the coaxial type; it is formed by an inner conductive cylinder 5 and an outer conductor constituted by the extension of the armature 20, between which an annular space 44 is defined. The output circuit is substantially symmetrical of the electron gun 1 with respect to a normal plane in the plane of the figure, that is to say that the external conductor has an annular shoulder 43 and a screen 41 bearing for example by legs on the shoulder 43 and defining with this shoulder a circular slot 42 for passage electrons from the beam 8. The latter is received by an annular projection 50 of the inner conductor 5. More generally, the drawings of the output circuit 4 and of the barrel 1 are such that the two impedances are close.

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 la paroi 20.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 bounded laterally by the wall 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 -V₀. Les paramètres sont choisis de sorte que se forme, dans la région d'injection 3, une cathode virtuelle 80. On a représenté par une flèche 82 les électrons transmis par la cathode virtuelle 80 et par des flèches 81, les électrons réfléchis par cette cathode virtuelle. En outre, 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 -V₀ is applied to the cathode 11. The parameters are chosen so that a virtual cathode 80 is formed in the injection region 3. The electrons transmitted by the virtual cathode 80 are represented by an arrow 82 and the electrons reflected by this cathode by arrows 81 Virtual. In addition, 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 plits faibles qu'à la périphérie de ce faisceau. Si la densité d'électrons et, par suite, le courant transporté augmentent, le potentiel et la vitesse des électrons diminuent jusqu'à atteindre zéro : les électrons forment alors un amas chargé négativement, formant un puits de potentiel appelé cathode virtuelle. Cette cathode virtuelle oscille et la fréquence des oscillations dépend notamment du courant d'injection ; 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 : le courant maximum pour un faisceau d'électrons donné est plus faible lorsque la zone d'injection 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 smaller than at the periphery of this beam. If the density of electrons and, consequently, the current transport increase, the potential and the speed of the electrons decrease until reaching zero: the electrons then form a negatively charged cluster, forming a well of potential called virtual cathode. This virtual cathode oscillates and the frequency of the oscillations depends in particular on the injection current; 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: the maximum current for a given electron beam is weaker when the injection area is of larger diameter.

Selon l'art antérieur, 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 supérieur au courant maximum susceptible de parcourir la région 3, entraînant ainsi la formation d'une cathode virtuelle. De la sorte, les électrons transmis représentent un courant modulé à la fréquence d'oscillation de la cathode virtuelle. Les électrons transmis, et eux seuls, voient leur énergie cinétique convertie en un champ électromagnétique par le circuit de sortie 4 et, plus précisément, dans l'espace de freinage compris entre le conducteur 5 et l'écran 41. L'énergie produite est transmise par le circuit coaxial de sortie 4 vers l'extérieur.According to the prior art, the dimensions of the device (electron gun and injection zone) and the current of the electron beam are chosen so that it is greater than the maximum current likely to flow through region 3, thus causing the formation of a virtual cathode. In this way, the electrons transmitted represent a current modulated at the frequency of oscillation of the virtual cathode. The electrons transmitted, and only they, see their kinetic energy converted into an electromagnetic field by the output circuit 4 and, more precisely, in the braking space between the conductor 5 and the screen 41. The energy produced is transmitted by the coaxial output circuit 4 to the outside.

Il apparaît que l'énergie ainsi produite l'est avec un rendement très supérieur à celui des vircators classiques. En effet, les recherches de la Déposante ont montré qu'une des raisons du faible rendement des vircators classiques était le fait d'utiliser un circuit de couplage qui impose un champ électromagnétique de phase sensiblement égale à tous les électrons, aussi bien transmis que réfléchis par la cathode virtuelle ; or ces deux sortes d'électrons sont sensiblement en opposition de phase et les énergies qu'ils créent s'annulent en grande partie. Selon l'invention, on utilise donc séparément l'énergie des électrons transmis et réfléchis. Dans l'art antérieur, on n'utilise que les électrons transmis.It appears that the energy thus produced is with a yield much higher than that of conventional vircators. Indeed, the Applicant's research has shown that one of the reasons for the low efficiency of conventional vircators was the fact of using a coupling circuit which imposes an electromagnetic field of phase substantially equal to all the electrons, both transmitted and reflected. by the virtual cathode; Now these two kinds of electrons are substantially in phase opposition and the energies they create largely cancel each other out. According to the invention, the energy of the transmitted and reflected electrons is therefore used separately. In the prior art, only the transmitted electrons are used.

En outre, le fait d'utiliser, selon l'invention, séparément les électrons transmis et réfléchis a pour effet de permettre la réalisation d'un couplage plus étroit entre électrons, et circuit de sortie et, par suite, l'obtention d'une énergie électromagnétique de meilleure qualité spectrale.In addition, the fact of using, according to the invention, separately the transmitted and reflected electrons has the effect of allowing the realization of a closer coupling between electrons, and output circuit and, consequently, obtaining electromagnetic energy of better spectral quality.

Une variante de réalisation (non représentée) consiste à disposer le circuit de sortie 4 de sorte que ne soient utilisés que les électrons réfléchis par la cathode virtuelle.An alternative embodiment (not shown) consists in placing the output circuit 4 so that only the electrons reflected by the virtual cathode are used.

Il est à noter par ailleurs qu'on choisit de préférence les dimensions du canon et de la région d'injection pour que le courant du faisceau soit supérieur au, mais voisin du courant maximum, de sorte que le courant transmis soit en moyenne une fraction importante du courant total injecté dans la région d'injection.It should also be noted that the dimensions of the barrel and of the injection region are preferably chosen so that the beam current is greater than, but close to the maximum current, so that the transmitted current is on average a fraction. significant of the total current injected into the injection region.

La figure 2 représente le dispositif de la figure 1, qui comporte en outre des moyens de post-accélération des électrons utilisés, vu également en coupe schématique longitudinale.2 shows the device of Figure 1, which further comprises means for post-acceleration of the electrons used, also seen in longitudinal schematic section.

A titre d'exemple, le générateur représenté figure 2 reprend la structure de celui de la figure 1, à ceci près que le circuit de sortie 4 est électriquement isolé du canon à électrons 1. Plus précisément, l'armature 20 formant l'anode du canon à électrons est sans contact électrique avec le conducteur extérieur, maintenant repéré 40, du circuit de sortie 4. A titre d'exemple, le conducteur 40 se prolonge autour de l'armature 20 en forme de cylindre creux de même axe ZZ que cette armature. Ce mode de réalisation comporte en outre des moyens 7 pour appliquer entre la cathode 11 et le circuit de sortie 4 une tension V₁, supérieure à la tension cathode/anode V₀. A titre d'exemple, les moyens 7 sont constitués par un transformateur dont le primaire 71 reçoit la tension d'alimentation et le secondaire 72 est relié :

  • à l'une de ses extrémités à la paroi 40 (potentiel de masse) ;
  • à son autre extrémité à la cathode 11 (potentiel -V₁) ;
  • en un point intermédiaire à l'anode 20, point tel que le potentiel y soit égal à -V₁ + V₀.
By way of example, the generator represented in FIG. 2 takes up the structure of that of FIG. 1, except that the output circuit 4 is electrically isolated from the electron gun 1. More precisely, the armature 20 forming the anode of the electron gun is without electrical contact with the external conductor, now marked 40, of the output circuit 4. By way of example, the conductor 40 extends around the armature 20 in the form of a hollow cylinder with the same axis ZZ as this frame. This embodiment further comprises means 7 for applying between the cathode 11 and the output circuit 4 a voltage V₁, greater than the cathode / anode voltage V₀. By way of example, the means 7 are constituted by a transformer whose primary 71 receives the supply voltage and the secondary 72 is connected:
  • at one of its ends to the wall 40 (ground potential);
  • at its other end to the cathode 11 (potential -V₁);
  • at an intermediate point at anode 20, point such that the potential there is equal to -V₁ + V₀.

Il est à noter que, ainsi qu'il est connu, pour que la formation d'une cathode virtuelle reste possible lorsque la tension V₁ utilisée est supérieure à la tension V₀ du mode de réalisation précédent, il est nécessaire d'augmenter la longueur de la région d'injection 3 et ceci d'autant plus que le rapport V₁/V₀ choisi est plus élevé.It should be noted that, as is known, so that the formation of a virtual cathode remains possible when the voltage V₁ used is greater than the voltage V₀ of the previous embodiment, it is necessary to increase the length of the injection region 3 and this all the more that the V₁ / V₀ ratio chosen is higher.

La figure 3 représente un premier mode de réalisation du générateur selon l'invention, dans lequel on utilise à la fois les électrons transmis et les électrons réfléchis par la cathode virtuelle.FIG. 3 represents a first embodiment of the generator according to the invention, in which both the transmitted electrons and the electrons reflected by the virtual cathode are used.

Sur cette figure, on retrouve le canon à électrons 1 formé de la cathode 11 et de l'anode 20, 21. Le canon 1 produit, ici aussi, un faisceau d'électrons 8 dans des conditions telles qu'il y a formation d'une cathode virtuelle 80 avec réflexion (flèches 81) d'une partie des électrons et transmission (flèche 82) d'une autre partie des électrons vers, à titre d'exemple, une paroi métallique 50 délimitant la région d'injection 3.In this figure, we find the electron gun 1 formed by the cathode 11 and the anode 20, 21. The gun 1 produces, here too, an electron beam 8 under conditions such that there is formation of a virtual cathode 80 with reflection (arrows 81) of a part of the electrons and transmission (arrow 82) of another part of the electrons towards, for example, a metal wall 50 delimiting the injection region 3.

Dans ce mode de réalisation, le circuit hyperfréquence de sortie 4 comporte deux voies : l'une débouche dans une région repérée 4A, comprise entre l'anode 20 et la cathode virtuelle 80 et destinée à récupérer l'énergie des électrons réfléchis 81 ; l'autre débouche dans une région repérée 4B, comprise entre la cathode virtuelle 80 et la paroi 50 et elle est destinée à récupérer l'énergie de électrons transmis 82. Les électrons 81 réfléchis par la cathode virtuelle l'étant avec un décalage moyen dans le temps de l'ordre d'une demi-période d'oscillations de cette cathode virtuelle par rapport aux électrons 82 transmis, il est nécessaire, afin de cumuler leurs effets, de déphaser l'énergie produite par les uns d'une valeur sensiblement égale à 180° par rapport aux autres ; cela est schématisé par un déphaseur 45, réalisable par tout moyen connu et connecté sur l'une des voies, 4A ou 4B, avant que les énergies existant dans les deux voies ne se combinent pour former l'énergie de sortie.In this embodiment, the output microwave circuit 4 has two channels: one leads into a region marked 4A, between the anode 20 and the virtual cathode 80 and intended to recover the energy of the reflected electrons 81; the other opens into a region marked 4B, between the virtual cathode 80 and the wall 50 and it is intended to recover the energy of transmitted electrons 82. The electrons 81 reflected by the virtual cathode being with an average offset in time in the region of half a period oscillations of this virtual cathode with respect to the transmitted electrons 82, it is necessary, in order to combine their effects, to phase the energy produced by the ones by a value substantially equal to 180 ° with respect to the others; this is shown diagrammatically by a phase shifter 45, which can be produced by any known means and connected on one of the channels, 4A or 4B, before the energies existing in the two channels combine to form the output energy.

Il est à noter que la paroi 46, entre les voies 4A et 4B, doit être d'une épaisseur suffisante pour éviter que les champs présents dans les deux voies ne se couplent avant la cathode virtuelle 80, cette épaisseur étant de l'ordre de grandeur de la distance de la paroi 46 à la cathode virtuelle.It should be noted that the wall 46, between the channels 4A and 4B, must be of sufficient thickness to prevent the fields present in the two channels from coupling before the virtual cathode 80, this thickness being of the order of magnitude of the distance from wall 46 to the virtual cathode.

On a représenté, sur la figure 3, un mode particulier de réalisation du circuit 4. D'autres variantes sont bien entendu possibles, qui consistent par exemple à réaliser, pour chacune des voies 4A et 4B, une structure de type coaxial telle que décrite figure 1 pour le circuit 4.FIG. 3 shows a particular embodiment of the circuit 4. Other variants are of course possible, which consist, for example, of producing, for each of the channels 4A and 4B, a structure of coaxial type as described Figure 1 for circuit 4.

La figure 4 représente un autre mode de réalisation du dispositif selon l'invention, dans lequel le faisceau produit par le canon à électrons est un cylindre plein, toujours vu en coupe schématique longitudinale.FIG. 4 represents another embodiment of the device according to the invention, in which the beam produced by the electron gun is a solid cylinder, always seen in schematic longitudinal section.

Sur cette figure, à titre d'exemple, on retrouve une structure voisine de celle de la figure 1, à ceci près que la surface émissive de la cathode, maintenant repérée 12, du canon 1 est en forme de disque, de sorte à émettre un faisceau électronique 88 cylindrique plein. 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 des 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 figure, by way of example, there is a structure similar to that of FIG. 1, except that 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 88. 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 elements, marked 26 and 46, constituted by grids or metallic sheets sufficiently thin for their absorption of electrons to be very low.

Le fonctionnement de ce dispositif est analogue à ce qui a été décrit pour la figure 1, avec formation d'une cathode virtuelle 83, électrons réfléchis 84 et électrons transmis 85 dont l'énergie cinétique est convertie en énergie hyperfréquence par le circuit de sortie 4.The operation of this device is analogous to what has been described for FIG. 1, with the formation of a virtual cathode 83, reflected electrons 84 and transmitted electrons 85 whose kinetic energy is converted into microwave energy by the output circuit 4 .

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. En pratique, toutefois, des cathodes de plus grand diamètre sont utilisables, du fait que les électrons ont tendance à se grouper à la périphérie de la cathode virtuelle.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 microwave energy obtained at the output, for example of the order of half -wave length. In practice, however, cathodes of larger diameter are usable, since the electrons tend to group around the periphery of the virtual cathode.

La figure 5 représente un autre mode de réalisation du générateur selon l'invention, dans lequel le faisceau électronique utilisé est un faisceau cylindrique plein et où le générateur comporte en outre des moyens de post-accélération.FIG. 5 represents another embodiment of the generator according to the invention, in which the electron beam used is a solid cylindrical beam and in which the generator further comprises post-acceleration means.

Sur cette figure, on retrouve une structure analogue à celle de la figure 2, sauf en ce qui concerne la cathode 11 du canon 1, le conducteur central 5 du circuit de sortie 4 et les écrans 21 et 41, remplacés respectivement par les éléments 12, 51, 26 et 46 tels que décrits figure 4.In this figure, there is a structure similar to that of Figure 2, except as regards the cathode 11 of the barrel 1, the central conductor 5 of the output circuit 4 and the screens 21 and 41, replaced respectively by the elements 12 , 51, 26 and 46 as described in Figure 4.

Les mêmes remarques que celles faites à propos de la figure 4 peuvent être faites ici.The same remarks as those made with respect to Figure 4 can be made here.

De la même manière, la figure 6 représente un mode de réalisation analogue à celui de la figure 3, mais dans lequel le faisceau électronique annulaire est remplacé par un faisceau électronique cylindrique plein.Likewise, FIG. 6 represents an embodiment similar to that of FIG. 3, but in which the annular electron beam is replaced by a solid cylindrical electron beam.

On retrouve donc une structure analogue à celle de la figure 3, sauf en ce qui concerne la structure de la cathode 11, maintenant repérée 12, et le faisceau électronique 8 qui devient un cylindre plein repéré 88, comme dans le cas des figures 4 et 5.We therefore find a structure similar to that of FIG. 3, except as regards the structure of the cathode 11, now marked 12, and the electron beam 8 which becomes a full cylinder marked 88, as in the case of FIGS. 4 and 5.

Claims (6)

  1. UHF-wave generator device, including:
    - an electron gun (1), capable of producing a beam of electrons (8; 88) in an injection region (3), the current transported being sufficient, having regard to the dimensions of the electron gun and of the injection region, to cause the formation of a virtual cathode (80; 83) in the injection region;
    - a UHF output circuit (4), performing the conversion of the kinetic energy of the electrons into UHF energy;
    the circuit being characterized in that it includes a first channel (4A), receiving the reflected electrons (81; 84) and a second channel (4B), receiving the transmitted electrons (82; 85), and a phase shifter (45) phase shifting the energy produced by one of the channels by substantially 180°.
  2. Device according to Claim 1, characterized in that the output circuit (4) is of the coaxial type.
  3. Device according to one of Claims 1 or 2, characterized in that the output circuit (4) is electrically isolated from the electron gun (1) and that an electron acceleration voltage (V₁) is applied between gun and output circuit.
  4. Device according to one of the preceding claims, characterized in that the beam of electrons (8) is in the form of a hollow cylinder.
  5. Device according to one of the preceding claims, characterized in that the beam of electrons (88) is in the form of a solid cylinder.
  6. Device according to one of the preceding claims, characterized in that it further includes means for applying a magnetic field for focusing the beam of electrons.
EP90903856A 1989-02-17 1990-02-16 Hyperfrequency wave generator device with virtual cathode Expired - Lifetime EP0413018B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR8902081A FR2643506B1 (en) 1989-02-17 1989-02-17 VIRTUAL CATHODE MICROWAVE GENERATOR DEVICE
FR8902081 1989-02-17
PCT/FR1990/000112 WO1990009674A1 (en) 1989-02-17 1990-02-16 Hyperfrequency wave generator device with virtual cathode

Publications (2)

Publication Number Publication Date
EP0413018A1 EP0413018A1 (en) 1991-02-20
EP0413018B1 true EP0413018B1 (en) 1995-02-08

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EP90903856A Expired - Lifetime EP0413018B1 (en) 1989-02-17 1990-02-16 Hyperfrequency wave generator device with virtual cathode

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US (1) US5113154A (en)
EP (1) EP0413018B1 (en)
JP (1) JP2863310B2 (en)
CA (1) CA2027558C (en)
DE (1) DE69016712T2 (en)
FR (1) FR2643506B1 (en)
WO (1) WO1990009674A1 (en)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2830371B1 (en) * 2001-09-28 2005-08-26 Thales Sa MICROWAVE WAVE GENERATOR WITH VIRTUAL CATHODE
FR2876218B1 (en) * 2004-10-05 2006-11-24 Commissariat Energie Atomique HYPERFREQUENCY WAVE GENERATING DEVICE WITH OSCILLATING VIRTUAL CATHODE.
RU2444081C1 (en) * 2010-07-05 2012-02-27 Государственное образовательное учреждение высшего профессионального образования "Саратовский государственный университет им. Н.Г. Чернышевского" Controlled generator on virtual cathode
RU2444805C1 (en) * 2010-08-04 2012-03-10 Алексей Иванович Арбузов Microwave generator based on virtual cathode

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Publication number Priority date Publication date Assignee Title
GB914307A (en) * 1958-03-20 1963-01-02 Emi Ltd Improvements in or relating to electron discharge devices for generating high frequency oscillations
US3084293A (en) * 1959-04-01 1963-04-02 Hughes Aircraft Co Microwave amplifier
US4150340A (en) * 1978-03-22 1979-04-17 The United States Of America As Represented By The Secretary Of The Navy High-power microwaves from a non-isochronous reflecting electron system (NIRES)
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
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

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
1983 IEEE International Conference on Plasma Science, 23-25 May 1983, San Diego, California, IEEE Conference Report - Abstracts, IEEE, (NEW YORK, US), T.J.T. Kwan et al.: "Microwave generation by virtual cathodes and reflexing systems", page 40, abstract 2D6 *

Also Published As

Publication number Publication date
FR2643506A1 (en) 1990-08-24
JP2863310B2 (en) 1999-03-03
DE69016712T2 (en) 1995-06-01
CA2027558A1 (en) 1990-08-18
US5113154A (en) 1992-05-12
FR2643506B1 (en) 1996-04-19
CA2027558C (en) 1997-09-30
DE69016712D1 (en) 1995-03-23
JPH03504181A (en) 1991-09-12
WO1990009674A1 (en) 1990-08-23
EP0413018A1 (en) 1991-02-20

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