EP0589019A1 - Magnetron - Google Patents

Magnetron

Info

Publication number
EP0589019A1
EP0589019A1 EP19930908036 EP93908036A EP0589019A1 EP 0589019 A1 EP0589019 A1 EP 0589019A1 EP 19930908036 EP19930908036 EP 19930908036 EP 93908036 A EP93908036 A EP 93908036A EP 0589019 A1 EP0589019 A1 EP 0589019A1
Authority
EP
European Patent Office
Prior art keywords
magnetron
cylindrical cavity
resonant
cylindrical
cavities
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.)
Ceased
Application number
EP19930908036
Other languages
German (de)
French (fr)
Inventor
Michael Barry Clive Brady
Julian Richard Robinson
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.)
Teledyne UK Ltd
Original Assignee
EEV Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by EEV Ltd filed Critical EEV Ltd
Publication of EP0589019A1 publication Critical patent/EP0589019A1/en
Ceased legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
    • H01J23/16—Circuit elements, having distributed capacitance and inductance, structurally associated with the tube and interacting with the discharge
    • H01J23/18—Resonators
    • H01J23/20—Cavity resonators; Adjustment or tuning thereof
    • H01J23/213—Simultaneous tuning of more than one resonator, e.g. resonant cavities of a magnetron
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
    • H01J23/16—Circuit elements, having distributed capacitance and inductance, structurally associated with the tube and interacting with the discharge
    • H01J23/18—Resonators
    • H01J23/20—Cavity resonators; Adjustment or tuning thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
    • H01J23/36—Coupling devices having distributed capacitance and inductance, structurally associated with the tube, for introducing or removing wave energy
    • H01J23/40—Coupling devices having distributed capacitance and inductance, structurally associated with the tube, for introducing or removing wave energy to or from the interaction circuit
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J25/00—Transit-time tubes, e.g. klystrons, travelling-wave tubes, magnetrons
    • H01J25/50—Magnetrons, i.e. tubes with a magnet system producing an H-field crossing the E-field
    • H01J25/52—Magnetrons, i.e. tubes with a magnet system producing an H-field crossing the E-field with an electron space having a shape that does not prevent any electron from moving completely around the cathode or guide electrode
    • H01J25/58—Magnetrons, i.e. tubes with a magnet system producing an H-field crossing the E-field with an electron space having a shape that does not prevent any electron from moving completely around the cathode or guide electrode having a number of resonators; having a composite resonator, e.g. a helix
    • H01J25/587—Multi-cavity magnetrons

Definitions

  • the invention relates to a magnetron, and in particular to a magnetron having an improved output arrangement.
  • the output from a magnetron is taken by means of a probe attached to one of the walls separating adjacent resonant cavities in the anode. This can distort the R.F. field pattern and so cause a degradation in performance of the device. It is difficult to couple heavily into the anode structure, because of weak R.F. coupling between adjacent cavities, with the result that with known magnetrons much of the potentially available microwave energy cannot be emitted.
  • This invention provides a magnetron comprising a cathode, an anode having a plurality of resonant cavities circumferentially spaced about an axis, means for producing an axial magnetic field; and an output arrangement comprising a generally cylindrical resonant cavity disposed co-axially at one end of the plurality of resonant cavities within the magnetic field, means for coupling energy from the plurality of resonant cavities into the cylindrical cavity, and means for coupling microwave energy from the cylindrical cavity out of the magnetron, the resonant frequency of the cylindrical cavity being selected to be substantially the desired output frequency of the magnetron.
  • cylindrical cavity Because of the cylindrical cavity, energy can be coupled symmetrically from each adjacent pair of resonant cavities, without the distortions induced when energy is taken from one pair of cavities only. Furthermore, the cylindrical cavity will tend to suppress the emission of harmonics of the desired signal.
  • the means for coupling energy from the plurality of resonant cavities comprises one of a plurality of circular straps connected to circumferentially alternate walls of the anode separating adjacent resonant cavities, which one strap projects axially into the cylindrical cavity further than another of the plurality of the straps.
  • An axially extensive electrostatic field is generated by the axially projecting strap from which energy is coupled into the cylindrical cavity from each adjacent cavity pair.
  • posts extend axially across the cylindrical cavity from circumferentially alternate walls separating adjacent resonant cavities. In such a case electric current would travel around adjacent posts to generate a magnetic field by which energy can be coupled into the cylindrical cavity.
  • the output from the cylindrical cavity may comprise a conventional loop or an elongate probe which couples energy into a coaxial line.
  • the output may include a movable short circuit for tuning the resonant frequency of the cylindrical cavity.
  • cylindrical resonant cavities may be disposed about each end of the plurality of circumferentially spaced cavities, which may be of use under especially high load conditions.
  • axially projecting straps may be present on each end of the walls of the anode.
  • Output loops or probes may be located within each cylindrical cavity and connected to a common co-axial or other line.
  • Figure 1 is a partly schematic, partly longitudinal sectional view through a magnetron according to on embodiment of the invention
  • Figure 2 is the same view as Figure 1, but shows a modification of that embodiment
  • Figure 3 is a view across arrow A-A of Figure 2.
  • Figure 4 is the same view as Figures 1 and 2 but showing a yet further embodiment of the invention.
  • a magnetron comprises a substantially cylindrical anode 1 having an axis la within which is located a co-axially mounted cathode 2. Vanes 3 extend inwardly from the inner walls of the anode ,2 to define a plurality of circumferentially spaced resonant cavities 4 (see Figure 3) . Magnetic pole pieces 5 provide an axially extending magnetic field at right angles to the electric field produced between the cathode 2 and anode vanes 3.
  • a generally cylindrical resonant cavity 6 is disposed co-axially at one end of the plurality of resonant cavities 4 in between the magnetic pole pieces 5.
  • the resonant frequency of the cavity 6 is selected to be substantially equal to the desired output frequency of the magnetron and in this way tends to suppress the emission of harmonics of the main signal.
  • the resonant frequency of such a cylindrical resonator, in the E01 mode is@@
  • Circular straps 7, 8, 9 are connected to the anode vanes 3 in generally known manner.
  • the radially innermost and outermost straps 7, 9 respectively are each connected to the same circumferentially alternate vanes 3 as each other, while the middle strap 8 is connected to the intervening vanes 3.
  • the innermost strap 7 projects axially further into the resonant cavity 6 than the other straps and in this way._is able, in use, to generate an electrostatic field by which energy can be electrically coupled into the cylindrical cavity 6 from each pair of adjacent resonant cavities 4.
  • An electric field probe and co-axial line 10 projects co-axially into the cylindrical cavity 6 in between the uppermost, as shown, pole pieces 5.
  • the end of the line 10 remote from the magnetron feeds a co-axial to waveguide transition member 11 for coupling energy into a waveguide 12.
  • FIG. 2 and 3 The embodiment shown in Figures 2 and 3 is generally similar to that shown in Figure 1 and the same parts have been identified by the same reference numerals.
  • the innermost strap 7b is the same height as the other straps 8 and 9.
  • Posts 20 extend between circumferentially alternate vanes 3 and the roof 21 of the cavity 6.
  • electric currents travel around the posts 6 and generate a magnetic field by which energy can be coupled into the cavity 6.
  • a loop output line 22 extends from one side for magnetically coupling energy from the cavity 6.
  • a slidable short circuit 23 is located within a waveguide 24 for adjusting or tuning the resonant frequency of the cavity 6 so that the output frequency of the magnetron may be pulled over a short range.
  • an extra cylindrical resonant cavity 6a is disposed co-axially at the other end, the bottom as shown., of the plurality of resonant cavities 4.
  • a further arrangement of straps 7a, 8a, 9a, a mirror image of straps 7 r 8, 9, is provided on the lower end of the plurality of vanes 3.
  • a further co-axial electric field probe 10a projects into the resonant cavity 6a and, although not shown in this view, each probe 10, 10a is connected to a common co-axial line for emission, e.g. into an appropriate waveguide.
  • Such an arrangement is particularly suitable if especially heavy coupling is required with the anode.
  • Each of the magnetrons shown has the advantage that microwave energy can be coupled into the cylindrical resonant cavity symmetrically from each pair of adjacent resonant cavities 4, which ensures low distortion in the output signal and ensures the efficient transfer of energy.
  • the cylindrical resonant cavity can also be selected to suppress harmonics of the output signal. Normally, in the known magnetrons, resonances in the space above and/or below the vanes can be a problem requiring careful design or the use of extra filters.
  • the anode structure may include integrally formed separating walls which separate the circumferential resonant cavities.
  • the three straps shown coupling together the anode vanes may be replaced by a pair of straps.
  • Magnetic loop outputs may be used as an alternative to the electric field probes shown in the Figures 1 and 4 embodiments.
  • one or both cavities 6, 6a may include a tuning arrangement for varying the resonant frequency and energy need not be coupled out from each of the cavities.

Landscapes

  • Microwave Tubes (AREA)

Abstract

Magnétron comprenant une cathode (2) ainsi qu'une anode (1) possédant une pluralité de cavités résonnantes (4) espacées sur sa circonférence. Un agencement de sortie comporte une cavité résonnante cylindrique (6) disposée coaxialement à l'une des extrémités de la pluralité de cavités résonnantes (4) et à l'intérieur d'un champ magnétique axial. Un moyen assure le couplage d'énergie directement entre chaque paire de cavités (4) résonnantes adjacentes et la cavité cylindrique (6) ainsi que le transfert d'énergie de la cavité cylindrique (6) depuis le magnétron. L'utilisation de la cavité résonnante (6) cylindrique permet d'assurer un couplage symétrique de l'énergie de chaque paire de cavités adjacentes.Magnetron comprising a cathode (2) and an anode (1) having a plurality of resonant cavities (4) spaced around its circumference. An outlet arrangement includes a cylindrical resonant cavity (6) arranged coaxially at one end of the plurality of resonant cavities (4) and within an axial magnetic field. A means ensures the energy coupling directly between each pair of adjacent resonant cavities (4) and the cylindrical cavity (6) as well as the transfer of energy from the cylindrical cavity (6) from the magnetron. The use of the cylindrical resonant cavity (6) ensures symmetrical coupling of the energy of each pair of adjacent cavities.

Description

MAGNETRON
The invention relates to a magnetron, and in particular to a magnetron having an improved output arrangement.
Conventionally, the output from a magnetron is taken by means of a probe attached to one of the walls separating adjacent resonant cavities in the anode. This can distort the R.F. field pattern and so cause a degradation in performance of the device. It is difficult to couple heavily into the anode structure, because of weak R.F. coupling between adjacent cavities, with the result that with known magnetrons much of the potentially available microwave energy cannot be emitted.
This invention provides a magnetron comprising a cathode, an anode having a plurality of resonant cavities circumferentially spaced about an axis, means for producing an axial magnetic field; and an output arrangement comprising a generally cylindrical resonant cavity disposed co-axially at one end of the plurality of resonant cavities within the magnetic field, means for coupling energy from the plurality of resonant cavities into the cylindrical cavity, and means for coupling microwave energy from the cylindrical cavity out of the magnetron, the resonant frequency of the cylindrical cavity being selected to be substantially the desired output frequency of the magnetron.
Because of the cylindrical cavity, energy can be coupled symmetrically from each adjacent pair of resonant cavities, without the distortions induced when energy is taken from one pair of cavities only. Furthermore, the cylindrical cavity will tend to suppress the emission of harmonics of the desired signal.
In one embodiment, the means for coupling energy from the plurality of resonant cavities comprises one of a plurality of circular straps connected to circumferentially alternate walls of the anode separating adjacent resonant cavities, which one strap projects axially into the cylindrical cavity further than another of the plurality of the straps.
An axially extensive electrostatic field is generated by the axially projecting strap from which energy is coupled into the cylindrical cavity from each adjacent cavity pair. In an alternative embodiment posts extend axially across the cylindrical cavity from circumferentially alternate walls separating adjacent resonant cavities. In such a case electric current would travel around adjacent posts to generate a magnetic field by which energy can be coupled into the cylindrical cavity.
The output from the cylindrical cavity may comprise a conventional loop or an elongate probe which couples energy into a coaxial line.
In another embodiment the output may include a movable short circuit for tuning the resonant frequency of the cylindrical cavity.
In a yet further embodiment cylindrical resonant cavities may be disposed about each end of the plurality of circumferentially spaced cavities, which may be of use under especially high load conditions. In such a case, axially projecting straps may be present on each end of the walls of the anode. Output loops or probes may be located within each cylindrical cavity and connected to a common co-axial or other line.
In order that the invention may be well understood, various embodiments thereof will be described with reference to the accompanying diagrammatic drawings, in which; Figure 1 is a partly schematic, partly longitudinal sectional view through a magnetron according to on embodiment of the invention;
Figure 2 is the same view as Figure 1, but shows a modification of that embodiment;
Figure 3 is a view across arrow A-A of Figure 2; and
Figure 4 is the same view as Figures 1 and 2 but showing a yet further embodiment of the invention.
As seen in Figure 1, a magnetron comprises a substantially cylindrical anode 1 having an axis la within which is located a co-axially mounted cathode 2. Vanes 3 extend inwardly from the inner walls of the anode ,2 to define a plurality of circumferentially spaced resonant cavities 4 (see Figure 3) . Magnetic pole pieces 5 provide an axially extending magnetic field at right angles to the electric field produced between the cathode 2 and anode vanes 3.
A generally cylindrical resonant cavity 6 is disposed co-axially at one end of the plurality of resonant cavities 4 in between the magnetic pole pieces 5. The resonant frequency of the cavity 6 is selected to be substantially equal to the desired output frequency of the magnetron and in this way tends to suppress the emission of harmonics of the main signal. As is well known, the resonant frequency of such a cylindrical resonator, in the E01 mode, is@@
FF proportional to the radius of that cavity.-
Circular straps 7, 8, 9 are connected to the anode vanes 3 in generally known manner. The radially innermost and outermost straps 7, 9 respectively are each connected to the same circumferentially alternate vanes 3 as each other, while the middle strap 8 is connected to the intervening vanes 3. The innermost strap 7 projects axially further into the resonant cavity 6 than the other straps and in this way._is able, in use, to generate an electrostatic field by which energy can be electrically coupled into the cylindrical cavity 6 from each pair of adjacent resonant cavities 4.
An electric field probe and co-axial line 10 projects co-axially into the cylindrical cavity 6 in between the uppermost, as shown, pole pieces 5. The end of the line 10 remote from the magnetron feeds a co-axial to waveguide transition member 11 for coupling energy into a waveguide 12.
The embodiment shown in Figures 2 and 3 is generally similar to that shown in Figure 1 and the same parts have been identified by the same reference numerals. Instead of electrically coupling into the cylindrical cavity 6, the innermost strap 7b is the same height as the other straps 8 and 9. Posts 20 extend between circumferentially alternate vanes 3 and the roof 21 of the cavity 6. In use, electric currents travel around the posts 6 and generate a magnetic field by which energy can be coupled into the cavity 6. Instead of the electric field probe, a loop output line 22 extends from one side for magnetically coupling energy from the cavity 6. A slidable short circuit 23 is located within a waveguide 24 for adjusting or tuning the resonant frequency of the cavity 6 so that the output frequency of the magnetron may be pulled over a short range.
In the embodiment shown in Figure 4, as compared to the Figure 1 embodiment, an extra cylindrical resonant cavity 6a is disposed co-axially at the other end, the bottom as shown., of the plurality of resonant cavities 4. A further arrangement of straps 7a, 8a, 9a, a mirror image of straps 7r 8, 9, is provided on the lower end of the plurality of vanes 3. A further co-axial electric field probe 10a projects into the resonant cavity 6a and, although not shown in this view, each probe 10, 10a is connected to a common co-axial line for emission, e.g. into an appropriate waveguide. Such an arrangement is particularly suitable if especially heavy coupling is required with the anode.
Each of the magnetrons shown has the advantage that microwave energy can be coupled into the cylindrical resonant cavity symmetrically from each pair of adjacent resonant cavities 4, which ensures low distortion in the output signal and ensures the efficient transfer of energy. The cylindrical resonant cavity can also be selected to suppress harmonics of the output signal. Normally, in the known magnetrons, resonances in the space above and/or below the vanes can be a problem requiring careful design or the use of extra filters.
Variations may be made to the embodiments shown. For example the anode structure may include integrally formed separating walls which separate the circumferential resonant cavities. The three straps shown coupling together the anode vanes may be replaced by a pair of straps. Magnetic loop outputs may be used as an alternative to the electric field probes shown in the Figures 1 and 4 embodiments. Similarly, in the Figure 4 embodiment one or both cavities 6, 6a may include a tuning arrangement for varying the resonant frequency and energy need not be coupled out from each of the cavities.

Claims

1. A magnetron comprising a cathode, an anode having a plurality of resonant cavities circumferentially spaced about an axis, means for producing an axial magnetic field; and an output arrangement comprising a generally cylindrical resonant cavity disposed co-axially at one end of the plurality of resonant cavities within the magnetic field, means for coupling energy from the plurality of resonant cavities into the cylindrical cavity, and means for coupling energy from the cylindrical cavity out of the magnetron, the resonant frequency of the cylindrical cavity being selected to be substantially the desired output frequency of the magnetron.
2. A magnetron, as claimed in claim 1, in which cylindrical resonant cavities are disposed at each end of the plurality of circumferentially spaced cavities.
3. A magnetron, as claimed in claim 1, in which the means for coupling energy from the plurality of resonant cavities, comprises one of a plurality of circular straps connected to circumferentially alternate walls of the anode separating adjacent resonant cavities, which one strap projects axially into the or a cylindrical cavity further than another of the plurality of straps.
4. A magnetron, as claimed in claim 1 or 2 in which posts extend axially across the or a cylindrical cavity from circumferentially alternate walls separating adjacent resonant cavities.
5. A magnetron, as claimed in any preceding claim, in which the output from the or a cylindrical cavity comprises a loop.
6. A magnetron, as claimed in any of claims 1 to 4, in which the output from the or a cylindrical cavity comprises an electric field probe.
7. A magnetron, as claimed in any preceding claim, in which the output from the or a cylindrical cavity includes a movable short circuit for tuning the resonant frequency of the cylindrical cavity.
EP19930908036 1992-04-10 1993-04-13 Magnetron Ceased EP0589019A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9207895A GB2266180B (en) 1992-04-10 1992-04-10 Magnetron
GB9207895 1992-04-10

Publications (1)

Publication Number Publication Date
EP0589019A1 true EP0589019A1 (en) 1994-03-30

Family

ID=10713805

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19930908036 Ceased EP0589019A1 (en) 1992-04-10 1993-04-13 Magnetron

Country Status (3)

Country Link
EP (1) EP0589019A1 (en)
GB (1) GB2266180B (en)
WO (1) WO1993021647A1 (en)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5483123A (en) * 1993-04-30 1996-01-09 Litton Systems, Inc. High impedance anode structure for injection locked magnetron
GB9723478D0 (en) 1997-11-07 1998-01-07 Eev Ltd Magnetrons
GB0319389D0 (en) * 2003-08-18 2003-09-17 E2V Tech Uk Ltd Magnetrons
JP4497517B2 (en) * 2003-12-15 2010-07-07 株式会社Ｉｈｉエアロスペース Microwave power transmission equipment
US8624496B2 (en) * 2009-10-20 2014-01-07 Muons, Inc. Phase and frequency locked magnetron
CN111900066B (en) * 2020-07-15 2024-06-04 清华大学 Magnetron with a magnetron body having a plurality of magnetron electrodes

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL232555A (en) * 1958-03-31
GB1009870A (en) * 1961-04-27 1965-11-17 Gen Electric Crossed-field electric discharge tube
GB982806A (en) * 1962-10-22 1965-02-10 Ass Elect Ind Improvements in multi-cavity magnetrons
GB1100424A (en) * 1964-02-24 1968-01-24 Kobe Kogyo Corp Improvements in or relating to magnetrons
US3458753A (en) * 1965-08-30 1969-07-29 Gen Electric Crossed-field discharge devices and couplers therefor and oscillators and amplifiers incorporating the same
GB1412034A (en) * 1973-03-02 1975-10-29 English Electric Valve Co Ltd Resonant devices
JPS54113241A (en) * 1978-02-24 1979-09-04 Hitachi Ltd Magnetron
GB2100056B (en) * 1981-06-10 1985-04-03 M O Valve Co Ltd Cavity magnetron
GB8925000D0 (en) * 1989-11-06 1990-05-30 Eev Ltd Magnetrons

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9321647A1 *

Also Published As

Publication number Publication date
GB9207895D0 (en) 1992-05-27
GB2266180B (en) 1995-08-30
WO1993021647A1 (en) 1993-10-28
GB2266180A (en) 1993-10-20

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