EP0407558A1 - Amplifier or oscillator device operating at ultrahigh frequency. - Google Patents

Amplifier or oscillator device operating at ultrahigh frequency.

Info

Publication number
EP0407558A1
EP0407558A1 EP90902637A EP90902637A EP0407558A1 EP 0407558 A1 EP0407558 A1 EP 0407558A1 EP 90902637 A EP90902637 A EP 90902637A EP 90902637 A EP90902637 A EP 90902637A EP 0407558 A1 EP0407558 A1 EP 0407558A1
Authority
EP
European Patent Office
Prior art keywords
circuit
modulation
electron beam
output circuit
microwave
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP90902637A
Other languages
German (de)
French (fr)
Other versions
EP0407558B1 (en
Inventor
Guy Convert
Jean-Pierre Brasile
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thales SA
Original Assignee
Thomson CSF SA
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Filing date
Publication date
Application filed by Thomson CSF SA filed Critical Thomson CSF SA
Publication of EP0407558A1 publication Critical patent/EP0407558A1/en
Application granted granted Critical
Publication of EP0407558B1 publication Critical patent/EP0407558B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • 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 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 causes them to regroup 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.
  • the effects of space charge are very important.
  • 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.
  • 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 1 at best) compared to the efficiency that it is possible to obtain ⁇ r with speed modulation tubes (often greater than 40%) .
  • the present invention has ofciet a device intended to produce hyperfrequency energy from an electron beam, which makes it possible to avoid the preceding limitations, that is to say an efficiency as energy conversion of the electron beam in microwave energy and a quality of the signal emitted comparable to those of speed modulation tubes, with a weight and in -an volume comparable to those of vircators.
  • the device according to the inversion comprises:
  • an electronic gun capable of producing an electron beam such that the current that i carries is slightly lower than the maximum current likely to be transported in the generator; a so-called modulation microwave circuit, making it possible to apply an alternating voltage whose amplitude is sufficient to trigger, during one of its alter ⁇ nances, the formation of a virtual cathode no longer allowing the passage of electrons, the current carried by the beam thus being modulated at the frequency called modulation of the alternating voltage;
  • FIG. 3 a third embodiment of the device according to the invention, in which the electron beam used is a solid cylindrical beam.
  • the same references relate to the same elements.
  • FIG. 1 therefore represents a first embodiment of the device 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 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 4, 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.
  • 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 operation of this device is as follows.
  • 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 is applied to the cathode 11.
  • a longitudinal magnetic field is preferably applied to the structure, using means not shown.
  • 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 current transport 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 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 hyper-frequency 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.
  • 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 direct voltage
  • MV voltages
  • KA currents
  • 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 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 is applied to the cathode relative to the anode, the modulation signal via circuit 7 and, in addition, a post-acceleration voltage + V 1 to the output circuit. relative to the wall 60, which is for example at the potential of the anode. From the outlet ⁇ an acceleration of the electrons is carried out from the injection zone 3.
  • FIG. 3 represents a third embodiment of the device according to the invention, in which the electron beam is a full cylinder.
  • the emitted surface if ve 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.
  • the inner 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.

Abstract

L'invention a pour objet un dispositif destiné à produire une énergie hyperfréquence à partir d'un faisceau d'électrons. Il comporte principalement: un canon électronique (1), permettant de produire un faisceau d'électrons (8) dans une zone dite d'injection (3); un circuit hyperfréquence de modulation (7), permettant de superposer une tension alternative à une fréquence donnée à la tension du faisceau dans la zone d'injection; l'amplitude de cette tension est suffisante pour, lors de l'une de ses alternances, assurer la transition entre l'état passant et l'état de cathode virtuelle, provoquant ainsi une modulation du courant porté par le faisceau d'électrons; un circuit hyperfréquence de sortie (4), fonctionnant à la fréquence du signal de modulation et excité par le courant modulé précédent.The subject of the invention is a device intended to produce microwave energy from an electron beam. It mainly comprises: an electron gun (1), making it possible to produce an electron beam (8) in a so-called injection zone (3); a modulating microwave circuit (7), making it possible to superimpose an alternating voltage at a given frequency on the voltage of the beam in the injection zone; the amplitude of this voltage is sufficient to, during one of its alternations, ensure the transition between the on state and the virtual cathode state, thus causing a modulation of the current carried by the electron beam; an output microwave circuit (4), operating at the frequency of the modulation signal and excited by the previous modulated current.

Description

DISPOSITIF AMPLIFICATEUR OU OSCILLATEUR FONCTIONNANT EN HYPERFREQUENCE AMPLIFIER OR OSCILLATOR DEVICE OPERATING IN MICROWAVE
La présente invention a pour objet un dispositif amplificateur d'ondes hyperfréquences, ainsi qu'un oscillateur obtenu à partir du dispositif précédent.The present invention relates to a microwave amplifier device, as well as an oscillator obtained from the previous device.
Pour générer et amplifier des ondes hyper réquences, 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 entraine 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 . 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 l& modulation de vitesse, ces tubes doivent utiliser des faisceaux longs, nécessitant le plus souvent une focalisation magnétique ; ces générateurs sont alors lourds et encombrants.To generate and amplify hyper frequency 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 causes them to regroup 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. 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, efficiency, 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. H 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. Avec un tel dispositif , il est possible d'obtenir des puissances hyperfréqoances élevées et, ce, sous un volumg 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 î. au mieux) par rapport au rendement qu'il est possible d'obter±r 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. With such a device, it is possible to obtain high microwave powers and this, under a reduced volumg. 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. In addition, the conversion efficiency is poor (of the order of 2 to 1 at best) compared to the efficiency that it is possible to obtain ± r with speed modulation tubes (often greater than 40%) .
La présente invention a pour ofciet un dispositif destiné i produire de l'énergie hyperfréquerce à partir d'un faisceau d'électrons, qui permette d'éviter les limitations précédentes, c'est-à-dire un rendement as 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 -an volume compa¬ rables à ceux des vircators. A cet effet, le dispositif selon l'inver ion comporte :The present invention has ofciet a device intended to produce hyperfrequency energy from an electron beam, which makes it possible to avoid the preceding limitations, that is to say an efficiency as energy conversion of the electron beam in microwave energy and a quality of the signal emitted comparable to those of speed modulation tubes, with a weight and in -an volume comparable to those of vircators. To this end, the device according to the inversion comprises:
- un canon électronique, susceptible de produire un faisceau d'électrons tel que le courant qu'i transporte soit légèrement inférieur au courant maximum susceptible d'être transporté dans le générateur ; un circuit hyperfréquence dit de modulation, permettant d'appliquer une tension alternative dont l'amplitude est suffisante pour déclencher, lors de l'une de ses alter¬ nances, la formation d'une cathode virtuelle n'autorisant plus le passage des électrons, le courant transporté par le faisceau se trouvant ainsi modulé à la fréquence dite de modulation de la tension alternative ;- an electronic gun, capable of producing an electron beam such that the current that i carries is slightly lower than the maximum current likely to be transported in the generator; a so-called modulation microwave circuit, making it possible to apply an alternating voltage whose amplitude is sufficient to trigger, during one of its alter¬ nances, the formation of a virtual cathode no longer allowing the passage of electrons, the current carried by the beam thus being modulated at the frequency called modulation of the alternating voltage;
- un circuit hyperfréquence de sortie destiné à fonctionner sensiblement à la fréquence de modulation, ou un multiple ou sous-multiple de celle-ci, ce circuit de sortie étant excité par le courant modulé précédent.- an output microwave circuit intended to operate substantially at the modulation frequency, or a multiple or submultiple thereof, this output circuit being excited by the preceding modulated current.
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 :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:
- la figure 1, un premier mode de réalisation du dispositif selon l'invention ;- Figure 1, a first embodiment of the device according to the invention;
- la figure 2, un second mode de réalisation du dispositif selon l'invention, dans lequel il comporte des moyens conférant au faisceau d'électrons une post-accélération- Figure 2, a second embodiment of the device according to the invention, in which it comprises means giving the electron beam post-acceleration
- la figure 3, un troisième mode de réalisation du dispositif selon l'invention, dans lequel le faisceau d'électrons utilisé est un faisceau cylindrique plein. Sur ces différentes figures, les mêmes références se rapportent aux mêmes éléments .- Figure 3, a third embodiment of the device according to the invention, in which the electron beam used is a solid cylindrical beam. In these different figures, the same references relate to the same elements.
La figure 1 représente donc un premier mode de réalisation du dispositif selon l'invention, vu en coupe schématique longitudinale.FIG. 1 therefore represents a first embodiment of the device 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 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 4, 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 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 4, 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 etBetween 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 des parois 20 et 40 respectivement, sans contact l'un avec l'autre de façon à ménager entre eux une fente 71.45 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 à 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. 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 -V . On applique de préférence à la structure, à l'aide de moyens non représentés, un champ magnétique longitudinalThe operation of this device is as follows. 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 is applied to the cathode 11. A longitudinal magnetic field is preferably applied to the structure, using means not shown.
(selon l'axe ZZ) pour focaliser le faisceau 8 ainsi produit.(along the ZZ axis) 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 péri¬ phérie. 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 eUe 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. 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 U y a formation de cathode virtuelle. 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 hyper¬ fréquence 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.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 current transport 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. 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. 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 hyper-frequency 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 fonction¬ nement 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, in order 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 V 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 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 selon l'Invention, dans lequel sont prévue 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 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 n , 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 n, 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 -V 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 sorté^ est réalisée une accélération des électrons au sortir de la zone d'injection 3.In operation, as before, a voltage -V is applied to the cathode relative to the anode, the modulation signal via circuit 7 and, in addition, a post-acceleration voltage + V 1 to the output circuit. relative to the wall 60, which is for example at the potential of the anode. From the outlet ^ an acceleration of the electrons is carried out from the injection zone 3.
La figure 3 représente un troisième mode de réali¬ sation du dispositif selon l'invention, dans lequel le faisceau électronique est un cylindre plein.FIG. 3 represents a third embodiment of the device according to the invention, in which the electron beam is a full cylinder.
Sur cette figure, on retrouve à titre d'exemple les mêmes éléments que sur la figure 1, excepté la cathode du canonIn this figure, we find by way of example the same elements as in Figure 1, except the cathode of the barrel
1, le conducteur intérieur du circuit de sortie 4 et les écrans du canon et du circuit de sortie.1, the inner conductor of the output circuit 4 and the screens of the gun and the output circuit.
Dans ce mode de réalisation, la surface émis si ve de la cathode, maintenant repérée 12, du canon 1 est en forme de disque de sorte à émettre un faisceau électronique 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 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 emitted surface if ve 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. Likewise, the inner 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 satis¬ faisant 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 Tordre 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

REVE NDI CATIONS DREDI NDI CATIONS
1. Dispositif amplificateur d'ondes hyperfréquence s, caractérisé par le fait qu'il comporte :1. Microwave wave amplifier device s, characterized in that it comprises:
- un canon électronique (1) , susceptible de produire un faisceau d'électrons (8) dans une région d'injection (3) , le courant transporté par le faisceau étant légèrement inférieur au courant maximum susceptible d'être transporté dans la région d'injection ;- an electronic gun (1), capable of producing an electron beam (8) in an injection region (3), the current transported by the beam being slightly less than the maximum current capable of being transported in the region d 'injection;
- un circuit hyperfréquence dit de modulation (7) , permettant d'appliquer dans la région d'injection une tension alternative dont l'amplitude est suffisante pour déclencher, lors de l'une de ses alternances, la formation d'une cathode virtuelle n'autorisant plus le passage des électrons, le courant transporté par le faisceau se trouvant ainsi modulé à la fréquence dite de modulation de la tension alternative ; - un circuit hyperfréquence de sortie (4) destiné à fonctionner sensiblement à la fréquence de modulation, ou un multiple ou sous-multiple de celle-ci, ce circuit de sortie étant excité par le courant modulé précédent, permettant ainsi la transformation en. énergie hyperfréquence d'une partie au moins de l'énergie des électrons du faisceau.- a so-called modulation microwave circuit (7), making it possible to apply an alternating voltage in the injection region, the amplitude of which is sufficient to trigger, during one of its half-waves, the formation of a virtual cathode n '' more authorizing the passage of electrons, the current carried by the beam thus being modulated at the frequency called modulation of the alternating voltage; - an output microwave circuit (4) intended to operate substantially at the modulation frequency, or a multiple or submultiple thereof, this output circuit being excited by the preceding modulated current, thus allowing transformation into. microwave energy of at least part of the electron energy of the beam.
2. Dispositif selon la revendication 1, caractérisé par le fait que le circuit de sortie est du type coaxial.2. Device according to claim 1, characterized in that the output circuit is of the coaxial type.
3. Dispositif selon l'une des revendications précédentes, caractérisé par le fait que le circuit de modulation est du type coaxial.3. Device according to one of the preceding claims, characterized in that the modulation circuit is of the coaxial type.
4. Dispositif selon les revendications 2 et 3, caractérisé par le fait que le conducteur central (40) du circuit de modulation est constitué par le cond-scteur extérieur du circuit de sortie .4. Device according to claims 2 and 3, characterized in that the central conductor (40) of modulation circuit is formed by the external cond-sctor of the output circuit.
5. Dispositif selon une des revendications 1 ou 2 , caractérisé par le fait que le circuit de sortie est isolé5. Device according to one of claims 1 or 2, characterized in that the output circuit is isolated
5 électriquement de la région d'injection et qu'une tension d'accélération des électrons est appliquée entre région d'injection et circuit de sortie.5 electrically from the injection region and that an electron acceleration voltage is applied between the injection region and the output circuit.
6. Dispositif selon Tune des revenications précé¬ dentes, caractérisé par le fait que le faisceau d'électrons est 0 en forme de cylindre creux.6. Device according to one of the preceding claims, characterized in that the electron beam is 0 in the form of a hollow cylinder.
7. Dispositif selon Tune des revendications précé¬ dentes, caractérisé par le fait que le faisceau d'électrons est en forme de cylindre plein .7. Device according to one of the preceding claims, characterized in that the electron beam is in the form of a solid cylinder.
8. Dispositif selon l'une des revendications précédentes, caractérisé par le fait qu'il compor_e en outre des moyens de ré-injection dans le circuit de modulation d'une partie du signal fourni par le circuit de sorti. , formant ainsi un oscillateur.8. Device according to one of the preceding claims, characterized in that it also comprises re-injection means into the modulation circuit of part of the signal supplied by the output circuit. , thus forming an oscillator.
9. Dispositif selon Tune des revendications précé- o dentés, caractérisé par le fait qu'il comporte en outre des moyens d'application d'un champ magnétique de focalisation du faisceau d'électrons. 9. Device according to one of the preceding claims, characterized in that it further comprises means for applying a magnetic field for focusing 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
FR8901007 1989-01-27
FR8901007A FR2642584B1 (en) 1989-01-27 1989-01-27 AMPLIFIER OR OSCILLATOR DEVICE OPERATING IN MICROWAVE
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 true EP0407558A1 (en) 1991-01-16
EP0407558B1 EP0407558B1 (en) 1995-08-02

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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
SE0601209A1 (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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CA2026111A1 (en) 1990-07-28
CA2026111C (en) 2000-05-30
WO1990009029A1 (en) 1990-08-09
FR2642584B1 (en) 1994-05-06
FR2642584A1 (en) 1990-08-03
DE69021290T2 (en) 1995-12-21
EP0407558B1 (en) 1995-08-02
US5164634A (en) 1992-11-17
DE69021290D1 (en) 1995-09-07
JPH03503818A (en) 1991-08-22

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