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
  • H01J23/36—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
  • H01J23/48—Coupling devices having distributed capacitance and inductance, structurally associated with the tube, for introducing or removing wave energy to or from the interaction circuit for linking interaction circuit with coaxial lines; Devices of the coupled helices type
• • 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
  • H01J23/54—Filtering devices preventing unwanted frequencies or modes to be coupled to, or out of, the interaction circuit; Prevention of high frequency leakage in the environment
• • 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

• This invention relates to magnetrons and more particularly to magnetrons in which output energy is coupled axially from the device.
• a magnetron in which output energy is coupled along the longitudinal axis of the device is illustrated schematically in Figure 1.
• a cathode 1 is located on a longitudinal axis X-X and surrounded by an anode structure 2.
• the anode includes a cylindrical anode shell 3 from the interior of which a plurality of anode vanes, two of which 4 and 5 are shown, project to define resonant cavities between them.
• Magnetic pole pieces 6 and 7 located at the ends of the coaxial structure are arranged to produce an axial magnetic field in the region between the cathode 1 and the anode 2.
• a magnetron comprising: a cathode coaxially surrounded by an anode; an axial output having an output coupling member connected to the anode; and a decoupling plate located between the end of the cathode and the said member.
• the decoupling plate is a high impedance component which in one preferred embodiment of the invention comprises a disc mounted on a post, with the post being mounted on the output coupling member.
• the disc forms a slot with the facing surface of the output coupling member to present a high impedance in series with the already existing capacitance C 0 .
• the dimensions of the decoupling plate are selected such that the equivalent circuit of the decoupling plate is an inductance and capacitance in parallel which gives a resonant circuit which is resonant at the operating frequency of the magnetron. This then prevents or reduces power loss due to capacitive coupling.
• the equivalent circuit of the decoupling plate acts as a resonant circuit which is resonant at the operating frequency of the magnetron, it may still prove of benefit where the resonant frequency is different to the operating frequency.
• Another advantage of using the invention is that it enables the effects of the inherent capacitive coupling to be negated whilst still retaining the cathode end hat configuration, thus protecting surrounding metal surfaces from stray electrons from the anode/cathode region of the magnetron.
• the decoupling plate is preferably a disc, providing a large surface area parallel to the end hat of the cathode and also to the facing surface of the output coupling member. Other plate configurations could be used however.
• the decoupling plate may be of any suitable material, such as copper, for example.
• the decoupling plate is supported by a post which is mounted on the output coupling member.
• the post is supported by the cathode. This arrangement still provides a high impedance component in series with the existing inherent capacitance at the output of the magnetron but it is less convenient to implement.
• Figure 2 is a schematic longitudinal view of a magnetron in accordance with the invention.
• Figure 3 is an explanatory diagram relating to the magnetron of Figure 2.
• FIG 4 schematically illustrates a longitudinal section another magnetron in accordance with the invention.
• a magnetron is similar to that described with reference to Figure 1 and for convenience, the same reference numerals are used for the same components.
• a cathode 1 is surrounded by an anode 2 and a coaxial output line 9 is connected via an output coupling member 11 to extract energy from the interior of the magnetron.
• a copper decoupling plate 16 is located between the end hat 15 of the cathode and the disc 12 forming part of the output coupling member 11.
• the plate 16 is a circular planar member and is support at its centre by a post 17 which is mounted at the centre of the disc 12.
• a capacitance exists between the face 18 of the decoupling plate 16 which faces the end of the top hat 15, this capacitance Co being that which exists in the arrangement of Figure 1.
• the decoupling plate 16 forms a slot with the output coupling member 12 which is a quarter wavelength long, shown as dimension a in Figure 2.
• the introduction of the decoupling plate 16 presents an effective inductance and capacitance in parallel which give a resonant circuit arranged to resonant at the operating frequency of the magnetron.
• the equivalent circuit is illustrated in Figure 3 where Li and Q are the inductance and capacitance due to the decoupling plate 16 and the capacitance C 0 is the pre-existing capacitance.
• the capacitive coupling is zero when the dimensions and location of the decoupling plate
• FIG. 4 illustrates another embodiment in accordance with the invention.
• the magnetron is similar to that illustrated in Figure 2 but in this case, a decoupling plate 20 is supported by a post 21 which is mounted on the end hat 15 of the cathode 1.
• the equivalent circuit of this arrangement is the same as that illustrated in Figure 3.

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• Microwave Tubes (AREA)
• Weting (AREA)

Priority Applications (6)

Applications Claiming Priority (2)

Publications (1)

Family

ID=9888801

Family Applications (1)

Country Status (11)

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Citations (2)

Family Cites Families (4)

• 2000
  • 2000-03-30 GB GB0007783A patent/GB2368184B/en not_active Expired - Fee Related
• 2001
  • 2001-03-30 DE DE60120145T patent/DE60120145T2/de not_active Expired - Lifetime
  • 2001-03-30 US US10/240,222 patent/US7026761B2/en not_active Expired - Lifetime
  • 2001-03-30 ES ES01915574T patent/ES2265422T3/es not_active Expired - Lifetime
  • 2001-03-30 CA CA2404622A patent/CA2404622C/en not_active Expired - Lifetime
  • 2001-03-30 AT AT01915574T patent/ATE328361T1/de not_active IP Right Cessation
  • 2001-03-30 CN CNB018105556A patent/CN1316538C/zh not_active Expired - Lifetime
  • 2001-03-30 AU AU2001242658A patent/AU2001242658A1/en not_active Abandoned
  • 2001-03-30 EP EP01915574A patent/EP1273023B1/en not_active Expired - Lifetime
  • 2001-03-30 WO PCT/GB2001/001473 patent/WO2001075928A1/en not_active Ceased
  • 2001-03-30 JP JP2001573513A patent/JP4774181B2/ja not_active Expired - Lifetime

Patent Citations (2)

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