EP0413018B1 - Mikrowellengenerator mit einer virtuellen kathode - Google Patents

Mikrowellengenerator mit einer virtuellen kathode 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
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.)
Expired - Lifetime
Application number
EP90903856A
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English (en)
French (fr)
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EP0413018A1 (de
Inventor
Guy Convert
Jean-Pierre Brasile
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Thales SA
Original Assignee
Thomson CSF SA
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Publication date
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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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  • Microwave Tubes (AREA)
  • Particle Accelerators (AREA)
  • Electron Sources, Ion Sources (AREA)

Claims (6)

  1. Vorrichtung zur Erzeugung von Mikrowellen
    - mit einer Elektronenkanone (1), die einen Elektronenstrahl (8; 88) in einer Injektionszone (3) erzeugen kann, wobei der transportierte Strom, unter Berücksichtigung der Abmessungen der Elektronenkanone und der Injektionszone ausreicht, um die Bildung einer virtuellen Kathode (80; 83) in der tnjektionszone hervorzurufen,
    - und mit einem Mikrowellenausgangskreis (4), der die Umwandlung der kinetischen Energie der Elektronen in eine Mikrowellenenergie bewirkt,
    dadurch gekennzeichnet, daß ein erster Kanal (4A), der die reflektierten Elektronen (81; 84) empfängt, und ein zweiter Kanal (4B), der die durchgelassenen Elektronen (82; 85) empfängt, sowie ein Phasenschieber (45) vorgesehen sind, der die von einem der Kanäle erzeugte Energie im wesentlichen um 180 in der Phase verschiebt.
  2. Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, daß der Ausgangskreis (4) vom koazialen Typ ist.
  3. Vorrichtung nach einem der Ansprüche 1 oder 2, dadurch gekennzeichnet, daß der Ausgangskreis (4) elektrisch von der Elektronenkanone (1) isoliert ist und daß eine Spannung (V₁) zur Beschleunigung der Elektronen zwischen die Kanone und den Ausgangskreis angelegt ist.
  4. Vorrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß der Elektronenstrahl (8) die Form eines Hohlzylinders hat.
  5. Vorrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß der Elektronenstrahl (88) die Form eines Vollzylinders hat.
  6. Vorrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß sie weiter Mittel zum Anlegen eines Magnetfelds aufweist, um den Elektronenstrahl zu fokussieren.
EP90903856A 1989-02-17 1990-02-16 Mikrowellengenerator mit einer virtuellen kathode Expired - Lifetime EP0413018B1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR8902081A FR2643506B1 (fr) 1989-02-17 1989-02-17 Dispositif generateur d'ondes hyperfrequences a cathode virtuelle
FR8902081 1989-02-17
PCT/FR1990/000112 WO1990009674A1 (fr) 1989-02-17 1990-02-16 Dispositif generateur d'ondes hyperfrequences a cathode virtuelle

Publications (2)

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

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EP90903856A Expired - Lifetime EP0413018B1 (de) 1989-02-17 1990-02-16 Mikrowellengenerator mit einer virtuellen kathode

Country Status (7)

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

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2830371B1 (fr) * 2001-09-28 2005-08-26 Thales Sa Generateur d'ondes hyperfrequences a cathode virtuelle
FR2876218B1 (fr) * 2004-10-05 2006-11-24 Commissariat Energie Atomique Dispositif generateur d'ondes hyperfrequences a cathode virtuelle oscillante.
RU2444081C1 (ru) * 2010-07-05 2012-02-27 Государственное образовательное учреждение высшего профессионального образования "Саратовский государственный университет им. Н.Г. Чернышевского" Управляемый генератор на виртуальном катоде
RU2444805C1 (ru) * 2010-08-04 2012-03-10 Алексей Иванович Арбузов Сверхвысокочастотный генератор на основе виртуального катода

Family Cites Families (5)

* Cited by examiner, † Cited by third party
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
JPH03504181A (ja) 1991-09-12
FR2643506B1 (fr) 1996-04-19
US5113154A (en) 1992-05-12
CA2027558A1 (fr) 1990-08-18
DE69016712T2 (de) 1995-06-01
JP2863310B2 (ja) 1999-03-03
DE69016712D1 (de) 1995-03-23
WO1990009674A1 (fr) 1990-08-23
EP0413018A1 (de) 1991-02-20
CA2027558C (fr) 1997-09-30
FR2643506A1 (fr) 1990-08-24

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