US2748203A - High frequency power amplifier - Google Patents

High frequency power amplifier Download PDF

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Publication number
US2748203A
US2748203A US300656A US30065652A US2748203A US 2748203 A US2748203 A US 2748203A US 300656 A US300656 A US 300656A US 30065652 A US30065652 A US 30065652A US 2748203 A US2748203 A US 2748203A
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United States
Prior art keywords
cathode
anodes
axis
space charge
input
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Expired - Lifetime
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US300656A
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English (en)
Inventor
Jr Philip H Peters
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General Electric Co
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General Electric Co
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Publication date
Priority to BE521664D priority Critical patent/BE521664A/xx
Application filed by General Electric Co filed Critical General Electric Co
Priority to US300656A priority patent/US2748203A/en
Priority to GB20362/53A priority patent/GB743030A/en
Priority to FR1081596D priority patent/FR1081596A/fr
Application granted granted Critical
Publication of US2748203A publication Critical patent/US2748203A/en
Anticipated expiration legal-status Critical
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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
    • H01J25/50—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

Definitions

  • magnetron oscillators have proved very successful as high power high frequency oscillators, similar devices in which a magnetic field and an electric field at right angles to each other react upon an electronic space charge have been investigated for use in power amplification.
  • magnetron type devices To operate successfully as amplifiers, such magnetron type devices must be arranged to prevent feedback from the output to the input circuit while at the same time preferably providing both substantial power gain and relatively high power output of high frequency energy.
  • a control voltage is employed to axially deflect a rotating space charge in a magnetron type of discharge device and thus divide the electron current from the cathode between a pair of axially spaced anodes according to the amplitude of the control voltage.
  • the anodes surround an elongated cathode and are coaxial with it, and either one or two input controlelectrodes having facing surfaces transverse to the cathode axis are axially spaced from the gap between the anodes.
  • Fig. 1 is a cross sectional view of a magnetron type of discharge device with external circuits therefor incorporating my invention
  • Fig. 2 is a modification.
  • a discharge device 1 whose essential elements are an elongated cathode 2, a pair of cylindrical anodes 3 and 4 coaxial with the cathode, and a pair of input or control electrode disks 5 and 6 near the respective ends of the cathode and transverse to it.
  • An envelope 7 which may suitably be made of glass, surrounds the electrode assembly, and the various electrodes are supported by conductive support wires or rods which are sealed through the envelope to provide external terminals for circuit connections.
  • a magnetic field parallel to the axis of the cathode is established within the space between the cathode and the anodes, the means for producing this field being indicated schematically at 8 as a solenoid positioned outside the envelope 7 and whose terminals may be connected to a suitable direct current voltage source.
  • the cathode 2 may suitably comprise a cylindrical nickel sleeve surrounding a heater coil and coated with an alkaline earth oxide mixture for copious emission of electrons when the cathode is heated.
  • the heater coil is connected to the cathode support rods and also at one point to the cathode sleeve.
  • the anode cylinders 3 and 4 which surround the cathode are of the same diameter and axially spaced to thus define a gap between them transverse to the cathode axis.
  • the cylinders are preferably of the same length.
  • the control electrode disks 5 and 6 substantially enclose the ends of the space charge chamber between the cathode and the anodes and are shown as centrally apertured to permit thepassage of the cathode heater leads therethrough.
  • the control electrodes are thus on opposite sides of the gap between the anodes and are preferably equidistant from the gap.
  • the disks 5 and 6 have a diameter substantially equal to the inside diameter of the anode cylinders 3 and 4 and are positioned near the ends of the anode cylinders. While this placement of the disks is provided in order to maintain the effectiveness of the control electrodes Without unduly increasing the capacitance between them and the anodes, it is obvious that other arrangements may be utilized if desired, such as decreasing the diameter of the control disks 5 and 6 and moving them inwardly toward the gap. However, the active or effective surfaces of the anodes 3 and 4 and of the cathode 2 are only those portions between the facing surfaces of the control electrodes 5 and 6. To prevent distortion of the magnetic field, each of the various electrodes is made of a non-magnetic conductive material, such as molybdenum.
  • An input circuit 9 schematically represented as a parallel resonant circuit with lumped capacitance and inductance elements, is connected between the terminals of the control electrodes 5 and 6, and a source of amplitude modulated signals to be amplified is coupled by coupling means 10 to the input circuit.
  • a tuned output circuit 11, schematically represented as is the input circuit 9, is connected between the terminals of the anodes 3 and 4, and suitable output coupling means 12 couples the amplified power from the output circuit 11 to the desired load. While the input and output circuits 9 and 11 have been illustrated as outside the envelope of the discharge device 1, equivalent circuit arrangements within the envelope may be substituted as may be desired for higher frequency operation.
  • the cathode 2 is heated to provide thermionic emission, a source of heating current 13 being connected between the cathode terminals, one of which is preferably grounded for convenience.
  • a radial electric field is established between both anodes 3 and 4 and the cathode 2 by connecting a source of unidirectional voltage 14 between them.
  • the common connection to the anodes is made from the positive terminal of the source 14 to the mid-point or high frequency neutral point of the output circuit, as represented by a midtap on its inductance element.
  • the negative terminal of the source 14 is suitably returned to ground.
  • the radial electric field in conjunction with the axial magnetic field imparts an average angular velocity about the cathode to the emitted electrons which constitute the space charge, and the intensities of the electric and mag- 3 netic fields are adjusted to provide a substantial electron current flow to the anodes.
  • a negative bias voltage is supplied to the input electrodes and 6. This is suitably achieved without interfering with the signal input circuit connected between these electrodes by connecting the negative terminal of a source of bias voltage 15 to the high frequency neutral point of the input circuit and grounding the positive terminal of the source.
  • both Input electrodes 5 and 6 are negative with respect to the cathode and the cathode space charge, thus tending to repel the space charge axially toward the center of the space charge chamber.
  • the space charge is thus bunched or compressed and is believed to take the form of a disk of relatively high charge density, since electrons in the disk are supplied from the entire active length of the cathode.
  • the space charge disk representing the bunched space charge of the device 1 is axially deflected to change the terminus of the electron space charge current from one to the other of the anodes 3 and 4- by the modulating voltage applied between the control electrodes 5 and 6 from the signal source previously mentioned.
  • the power to switch the space charge disk across the anode gap is negligible and hence the input circuit is not loaded, as is generally desired for amplifier operation.
  • the output circuit 11 is preferably tuned, more or less broadly as desired, to the frequency of the input circuit 9 so that the alternate switching of current from one anode to the other at the input frequency excites the output cir cuit at the same frequency.
  • An output amplitude limiting action which occurs when the drive input is either more than sufiicient to transfer the current all to one anode or less than sufiicient to create any ditferential current between anodes may also be utilized.
  • the power output is derived from the voltage source 14 and the power to switch the bunched charge across the gaps is negligible.
  • the output circuit 11 may be tuned to any desired harmonic of the frequency of the input circuit for utilization of the power amplifier as a frequency multiplier.
  • Fig. 2 a modification of the arrangement of Fig. 1 is employed in which the input and output circuits are single-ended to provide potentials with respect to a common reference point instead of being arranged for balanced or push-pull operation as in Fig. 1.
  • a discharge device 16 having a cylindrical sleeve cathode 17, a pair of hollow cylindrical anodes 18 and 19, and a pair of annular electrodes 20 and 21, electrode 21 being conductively supported from the cathode.
  • the electrode 29 and the anodes 18 and 19 are provided with radial flanges which extend through the envelope to provide external terminals.
  • Conductive support wires for the cathode 17 and for a cathode heater assembly inside the cathode sleeve also extend axially through the envelope Wall past the input electrode Ztl.
  • a magnetic field parallel to the cathode axis is established within the space between the cathode and anodes, the means for producing this field being indicated as magnet pole pieces 23 respectively positioned at either end of the device 16.
  • An input circuit 24 schematically represented as a parallel resonant circuit with lumped capacitance and inductance elements is coupled between the cathode 17 and control electrode 20. As shown in Fig. 2, one side of the input circuit 24 is connected to the input or control electrode 20 and the other side is coupled to ground through a negative bias voltage source 25 which may suitably be bypassed by a capacitor 26. The cathode 17 is directly returned to ground.
  • a suitable input coupling means such as a capacitor 27 supplies the biased electrode 20 with a signal voltage from a signal source.
  • the bias voltage is selected as previously described to axially compress the cathode space charge by repelling at least a portion of the space charge toward the cathode 17 and the electrode 21 to compress the space charge axially.
  • a suitable output coupling means 31 is coupled to the output circuit 28 to transmit the amplified power to the desired load.
  • the amplifier arrangement of Fig. 2 corresponds to that of Fig. 1. Accordingly, when the input signal on the input electrode 20 is negative going, the space charge is forced across the gap between the anode cylinder 18 and 19 toward the other electrode 21, which may also be considered as a control electrode at cathode potential. The space charge current accordingly is transferred from the anode 18 to the anode 19 thereby to provide amplified signals across the output circuit 28.
  • An electron discharge device of the magnetron type comprising an evacuated envelope containing an elongated electron emitting cathode extending along a given axis, first and second cylindrical anodes spaced along said axis and coaxial therewith and each presenting a continuous cylindrical surface facing said cathode, the spaced facing ends of said anodes being transverse to said axis and defining a gap between them, means for coupling an output circuit between said anodes and first and second control electrodes having facing surfaces transverse to said axis and spaced from said gap on opposite sides thereof, said electrodes being surrounded by and located within the axial extent of said anodes, for deflecting electrons in the space between said cathode and said anodes across said gap.
  • An electron discharge device comprising an evacuated envelope containing an elongated electron emitting cathode extending along a given axis, first and second cylindrical members spaced along said axis and coaxial therewith and each presenting a continuous cylindrical surface facing said cathode, the spaced facing ends of said members being transverse to said axis and defining a gap between them, means for coupling an output circuit between said members and first and second control electrodes having facing surfaces transverse to said axis and spaced from said gap on opposite sides thereof, at least one of said electrodes being surrounded by and located within the axial extent of said members, and means for producing a static magnetic field parallel to said axis in the space between said cathode and said cylindrical members.
  • An electron discharge device of the magnetron type comprising an envelope containing an elongated electron emitting cathode extending along a given axis, a pair of anodes each surrounding said cathode and having an inner cylindrical surface coaxial therewith and each presenting a continuous cylindrical surface facing said cathode, said anodes having facing end surfaces transverse to said axis spaced from each other along said axis to define a gap between them means for coupling an output circuit between said anodes, and first and second annular control input electrodes surrounding said cathode near the opposite ends thereof and having facing surfaces transverse to said axis, said control electrodes being spaced from said gap on opposite sides thereof and being located within the axial extent of said anodes.
  • a power amplifier comprising an electron discharge device having an envelope containing an elongated electron emitting cathode extending along a given axis, a pair of cylindrical anodes surrounding said cathode and coxial therewith, said anodes having facing end surfaces traneverse to said axis spaced along said axis to define a gap between them and each presenting a continuous cylindrical surface facing said cathode, and a pair of control electrodes having facing surfaces transverse to said axis and spaced from said gap on opposite sides thereof, means providing a static axial magnetic field in the space between said cathode and said cylindrical members and means providing a static radial electrical field between said cathode and said anodes to establish a generally rotating space charge around said cathode between said cathode and said anodes, means for applying a negative bias to at least one of said control elecrodes with respect to said cathode to axially compress the rotating space charge, and means for applying signal voltage between said control electrodes to axially
  • a high frequency power amplifier comprising an electron discharge device having an envelope containing an elongated electron emitting cathode extending along a given axis, a pair of cylindrical anodes surrounding said cathode and coaxial therewith, said anodes having facing end surfaces transverse to said axis spaced along said axis to define a gap between them and each presenting a continuous cylindrical surface facing said cathode, and a pair of control electrodes having facing surfaces transverse to said axis and spaced from said gap on opposite sides thereof, means providing a static axial magnetic field in the space between said cathode and said cylindrical members and means providing a static radial electric field between said cathode and said anodes to establish a generally rotating space charge around said cathode between said cathode and said anodes, means for applying a negative bias to said control electrodes with respect to said cathode to axially compress the rotating space charge, tuned input circuit means coupled to said control electrodes for applying an alternating input voltage therebetween to move the
  • a high frequency power amplifier comprising an electron discharge device having an envelope containing an elongated electron emitting cathode extending along a given axis, a pair of hollow anodes each surrounding said cathode and having an inner cylindrical surface coaxial therewith, said anodes having facing end surfaces transverse to said axis spaced along said axis to define a gap between them and each presenting a continuous cylindrical surface facing said cathode, and a pair of control electrodes having facing surfaces transverse to said axis and spaced from said gap on opposite sides thereof, means for establishing an axial magnetic field in the space between said cathode and said cylindrical members, means for supplying a positive potential to said anodes with respect to said cathodes to establish a radial electric field between said cathode and said anodes whereby a generally rotating direction around said cathode is imparted to the space charge flowing between said cathode and said anodes, means for applying a negative bias to at least one of said control electrodes with respect
  • a power amplifier comprising an electron discharge device having an elongated electron emitting cathode extending along a given axis, a pair of hollow anodes surrounding said cathode to define a space charge chamber coaxial therewith, said anodes having facing end surfaces transverse to said axis spaced along said axis to define a gap between them and each presenting a continuous cylindrical surface facing said cathode, and a pair of control electrodes each having a surface transverse to said axis facing said gap and each spaced therefrom on opposite sides thereof, means providing a static axial magnetic field and a static radial electric field in said space charge chamber to establish a generally rotating space charge current around said cathode between said cathode and said anodes, means for applying a negative bias to said control electrodes with respect to said cathode to axially compress the rotating space charge, and means for applying an alternating input voltage between said electrodes and said cathode to switch the space charge current between said pair of anodes.
  • a power amplifier comprising an electron discharge device having an elongated electron emitting cathode extending along a given axis, a pair of hollow anodes surrounding said cathode and coaxial therewith, said anodes having facing end surfaces transverse to said axis and spaced along said axis to define a gap between them and each presenting a continuous cylindrical surface facing said cathode, and a pair of control electrodes having facing surfaces transverse to said axis spaced from said gap, one of said electrodes being connected to said cathode, means for providing a static axial magnetic field and a static radial electric field in the space between said cathode and said anodes to establish a generally rotating space current around said cathode, means for applying a negative bias to the other control electrode with respect to said cathode and said one electrode to axially compress the rotating space charge, and means for applying an alternating input voltage between said other control electrode and said cathode and said one electrode to switch the compressed space charge between said pair of ano

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US300656A 1952-07-24 1952-07-24 High frequency power amplifier Expired - Lifetime US2748203A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
BE521664D BE521664A (en)) 1952-07-24
US300656A US2748203A (en) 1952-07-24 1952-07-24 High frequency power amplifier
GB20362/53A GB743030A (en) 1952-07-24 1953-07-22 Improvements in and relating to magnetron devices
FR1081596D FR1081596A (fr) 1952-07-24 1953-07-24 Magnétron amplificateur

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Application Number Priority Date Filing Date Title
US300656A US2748203A (en) 1952-07-24 1952-07-24 High frequency power amplifier

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US2748203A true US2748203A (en) 1956-05-29

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BE (1) BE521664A (en))
FR (1) FR1081596A (en))
GB (1) GB743030A (en))

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1816682A (en) * 1926-03-10 1931-07-28 Gen Electric Electron discharge device
US2147143A (en) * 1937-07-24 1939-02-14 Rca Corp Magnetron detector circuit
US2187172A (en) * 1936-12-06 1940-01-16 Rca Corp Vacuum tube
US2187171A (en) * 1936-06-04 1940-01-16 Rca Corp Vacuum tube for microwaves or ultra-short waves
US2293798A (en) * 1939-05-24 1942-08-25 Rca Corp Modulation of magnetron oscillators
US2535793A (en) * 1946-01-08 1950-12-26 Rca Corp Magnetron
US2576599A (en) * 1946-02-21 1951-11-27 Rca Corp Magnetron

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1816682A (en) * 1926-03-10 1931-07-28 Gen Electric Electron discharge device
US2187171A (en) * 1936-06-04 1940-01-16 Rca Corp Vacuum tube for microwaves or ultra-short waves
US2187172A (en) * 1936-12-06 1940-01-16 Rca Corp Vacuum tube
US2147143A (en) * 1937-07-24 1939-02-14 Rca Corp Magnetron detector circuit
US2293798A (en) * 1939-05-24 1942-08-25 Rca Corp Modulation of magnetron oscillators
US2535793A (en) * 1946-01-08 1950-12-26 Rca Corp Magnetron
US2576599A (en) * 1946-02-21 1951-11-27 Rca Corp Magnetron

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GB743030A (en) 1956-01-04
FR1081596A (fr) 1954-12-21
BE521664A (en))

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