US3414761A - Dither tuner for a coaxial magnetron - Google Patents

Dither tuner for a coaxial magnetron Download PDF

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Publication number
US3414761A
US3414761A US487697A US48769765A US3414761A US 3414761 A US3414761 A US 3414761A US 487697 A US487697 A US 487697A US 48769765 A US48769765 A US 48769765A US 3414761 A US3414761 A US 3414761A
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US
United States
Prior art keywords
frequency
tuner
magnetron
anode
crankshaft
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Expired - Lifetime
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US487697A
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English (en)
Inventor
George E Glenfield
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S F D LAB
S-F-D LABORATORIES
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S F D LAB
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Priority to US487697A priority Critical patent/US3414761A/en
Priority to GB39346/66A priority patent/GB1126093A/en
Priority to DE19661541056 priority patent/DE1541056B1/de
Application granted granted Critical
Publication of US3414761A publication Critical patent/US3414761A/en
Anticipated expiration legal-status Critical
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    • 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
    • H01J23/207—Tuning of single resonator

Definitions

  • the caxial magnetron tube includes an evacuated envelope structure containing an anode electrode structure having a circular array of coupled anode resonators coaxially disposed of a circular electric mode cavity resonator coupled to the anode resonators via an array of coupling slots.
  • the coupling slots serve to lock the 1r mode of the anode resonators to the circular electric mode of th cavity resonator.
  • An axially translatable end wall of the circular electric mode resonator is provided for tuning the resonant frequency of the cavity resonator and the coupled anode resonators for tuning the output frequency of the tube.
  • a cathode electrode structure is coaxially disposed of the anode to produce a magnetron interaction region therebetween.
  • An elongated tuner actuating shaft is coupled to the movable tuning wall and extends through the vacuum envelope of the tube via a vacuum tight bellows.
  • a motor driven crankshaft is coupled via a yoke to the outer end of the tuner actuating shaft for dithering of the shaft and its dependent tuner at a relatively high rate as of 20 to 160 cycles per second to produce frequency modulation of the output frequency of the tube.
  • the motor is affixed to the outside of a housing and the housing is filled with a viscous fluid such as oil. The oil surrounds the crankshaft, yoke, and tuner actuating shaft for dampening the oscillatory motion of the tuner.
  • High power, high frequency tubes such as crossed field microwave tubes or magnetrons, are generally employed in radar scan systems for detecting ground clutter, scatter and the like.
  • the magnetron is modulated or dithered by means of a tuner. Modulation is achieved in one approach by the axial movement of a tuning rod and disk within the cavity of the magnetron to effectuate a variable displacement of the radio frequency magnetic field lines.
  • One such type tube is described in copending U.S. patent application Ser. No. 221,796, filed Sept. 6, 1962, now issued as U.S. 3,223,876 on Dec. 14, 1965, and assigned to the same assignee.
  • the frequency modulated transmitted signal be precise and readily controllable over a desired range of frequency.
  • any misalignment of the tuning rod, or variations in the axial oscillation of the rod results in undesirable changes in the modulating frequency.
  • parasitic modes of oscillation may appear, with resultant reduction in tube power output at desired frequencies.
  • any shutdown due to inoperability of the crossed field device may disable the security detection system in which it is employed, which is a highly undesirable condition.
  • An object of this invention is to provide a novel and imbproved tuning means for a high frequency, high power tu e.
  • Another object of this invention is to provide an improved high rate of change mechanical tuner for a magnetron.
  • Another object is to provide a tuner mechanism for a magnetron that affords precise tuning and longer life.
  • the tuning means of a magnetron tube comprises a mechanical assembly including an input shaft coupled to a drive means, a connecting rod connected to such input shaft and disposed along the axis of the tube, and a tuning plunger and disk coupled to the rod.
  • the tuning disk is oscillated in the vicinity of an annular anode electrode such that the frequency output of the tube is modulated at a rate determined by the frequency of oscillation of the disk along the tube axis.
  • Precision mechanical alignment and retainer means are utilized to maintain the tuning disk in precise alignment with the tube axis and coaxially with the annular anode, whereby the modulated frequency remains effectively constant during operation.
  • FIG. 1 is a perspective view of the inventive crossed field device or magnetron assembly
  • FIG. 2 is a fragmentary cross-section view of the assembly, taken along lines 22 of FIG. 1.
  • a crossed field device such as a. magnetron, comprises a support or mount 10 incorporating a permanent magnet structure for providing a unidirectional magnetic field.
  • the support 10 contains a hollow body 12, made of copper for example, adapted for evacuation.
  • a waveguide assembly 14 is connected to the body 12 through a portion of the support 10.
  • a tuner assembly 16 is disposed in accordance with this invention.
  • a cathode lead-in structure 18 extends from the support 10 in quadrature relationship with the axially aligned output waveguide 14 and tuner assembly 16 in the conventional manner as is well known from the aforecited U.S. Patent 3,223,876.
  • the magnetron of FIGURE 1 includes a cavity structure 20 wherein a cathode electrode 21 and "an annular output electrode or anode resonator structure 22 are disposed in coaxial alignment.
  • the cavity structure 20 comprises a circular mode cavity which is disposed centrally of the anode structure 22 along the axis of the tube.
  • An array of anode resonator vanes 23 surround the circular electric mode cavity 20 and the adjacent vanes have spaces therebetween.
  • Alternate anode resonators are electromagnetically coupled to the circular electric mode cavity 20 by means of axially directed slots 24 communicating through a common wall between the anode resonators and the cavity 20.
  • a magnetron interaction region surrounds the outer tips of the anode vanes 23 and is defined by the space in between the vanes and the surrounding emitter ring of the cathode 21.
  • the cathode lead-in assembly 18 is connected internally of the tube via electrical leads to the cathode 21 and enables the formation of electrons that interact with crossed electric and magnetic fields in the region of the anode resonators.
  • a strong axial DC magnetic field of about 12,000 to 15,000 gauss by way of example, is provided by means of a permanent magnet encompassing the anode electrode 22.
  • the magnetron interaction region is disposed between a pair of magnet pole pieces 25 positioned on opposite sides of the anode electrode.
  • the magnetron produces a radio frequency output of about 32-37 gigacycles per second (go/sec.) 'Which is directed to a utilization load through the output waveguide 14 or a coupling loop, in a well known manner.
  • a tuner mechanism 16 is coupled to the cavity structure 20 for achieving modulation of the characteristic resonant frequency of the cavity.
  • the tuner mechanism includes an input shaft or crankshaft 26 driven by a motor drive means 28, which may be rotated at 9600 revolutions per minute, for example.
  • the crankshaft 26 is engaged by eccentric coupling to a connecting rod 30 that is actuated to move along the central axis of the magnetron tube.
  • the eccentric coupling includes a yoke 29 riding on an eccentric portion of the crankshaft 26.
  • an assembly including resilient rings 32 and 34 are provided adjacent to the shaft 26.
  • the O-ring 32 at the terminus of the crankshaft is secured by a hardened steel washer 36, which in turn is urged against the O-ring 32 by a ballpoint contact 38 secured in a groove of the shaft 26.
  • the O-ring assembly 32 affords counterthrust to any erratic longitudinal travel of the shaft 26.
  • the O-ring 34 is located adjacent to the shaft 26 and applies pressure to a thin walled Teflon (Du Pont product) sleeve 56. This combination allows high speed rotation of shaft 26 without deterioration of the oil seal created by O-ring 34. Preloaded ball bearings 40 are also secured within the yoke 29 adjacent the crankshaft 26 to avoid radial displacement and to maintain precise alignment of the shaft.
  • Teflon Du Pont product
  • the connecting rod 30 is encompassed by a lubricating, viscous oil 42.
  • Oil seals 44 are provided to prevent seepage of the oil 42 out of the chamber enclosing the connecting rod 30.
  • the connecting rod 30 is linked, by threaded adaptor means for example, to a tuning plunger 46 that carries a tuning disk 48, disposed within the cavity structure 20a and adjacent to the anode resonator structure 22.
  • the diameter of the rod 30 is relatively small, affording flexibility of the rod, so that only linear axial motion is translated to the plunger 46.
  • the plunger 46 is vacuum sealed to the envelope of the tube by means of a cylindrical bellows 50.
  • the plunger 46 may be of tungsten, and the disk 48 may be of copper, by way of example.
  • the disk may be /32 inch thick and have a diameter of 0.340 inch, for example.
  • a double bearing assembly 52 engages the plunger assembly in rigid fashion, allowing only linear motion.
  • the tuning disk 48 is moved axially when the drive means 28 is energized.
  • the displacement stroke of the disk 48 is about 0.003 inch and the disk oscillates at about 160 cycles per second.
  • a modulation of approximately 150 megacycles per second (mc./sec.) is realized, which is a mc. deviation of the Ka band frequency of 32-37 gc./sec. for the magnetron tube employed.
  • This modulation may be varied about the center frequency at a 20-160 c.p.s. rate.
  • crankshaft 26 may be made with a shaft of another size.
  • a frequency readout device 54 may be coupled to the crankshaft 26 for translating the frequency of rotation, and thus the frequency of oscillation of the plunger 46 and disk 48, to a frequency value related to the tube frequency.
  • the frequency readout device 54 may be a crystal serving as a pressure transducer or voltage transducer that measures the degree of rotation, or the change of position or phase of the input shaft 26. The sensed change of phase is translated to a readout frequency representing modulation frequency.
  • the readout device may be coupled to the rotary drive means 28 in lieu of the input shaft.
  • a gated photocell or linear voltage device may be coupled to the rotary shaft 26 for frequency readout.
  • a coaxial magnetron means forming an evacuated envelope structure, means forming an anode structure having a circular array of coupled anode resonators disposed inside said envelope, means forming a circular electric mode cavity resonator coaxially disposed of said array of anode resonators, means forming an array of electromagnetic coupling slots communicating between said circular electric mode cavity resonator and said array of anode resonators for locking the 1r mode of the anode resonators to a circular electric mode of said circular electric mode resonator, means forming an axially translatable end 'wall of said circular electric mode resonator for tuning the resonant frequency of the coupled resonator system which includes said circular electric mode resonator and said array of anode resonators coupled thereto, means forming a cathode electrode structure coaxially disposed of said array of anode resonators for defining an annular magnetron electromagnetic interaction region therebetween, the improvement comprising, means for oscill
  • the apparatus of claim 1 including a housing external of said vacuum envelope and enclosing said yoke, crankshaft and an outer end of said drive shaft, and a viscous liquid filling said housing and surrounding said yoke, crankshaft and drive shaft for dampening the oscillatory motion of said drive shaft.
  • HERMAN KARL SAALBACH Primary Examiner. S. CHATMON, JR., Assistant Examiner.

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  • Microwave Tubes (AREA)
  • Transmission Devices (AREA)
US487697A 1965-09-16 1965-09-16 Dither tuner for a coaxial magnetron Expired - Lifetime US3414761A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US487697A US3414761A (en) 1965-09-16 1965-09-16 Dither tuner for a coaxial magnetron
GB39346/66A GB1126093A (en) 1965-09-16 1966-09-02 Tuner mechanism for microwave tubes
DE19661541056 DE1541056B1 (de) 1965-09-16 1966-09-06 Koaxialmagnetron

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US487697A US3414761A (en) 1965-09-16 1965-09-16 Dither tuner for a coaxial magnetron

Publications (1)

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US3414761A true US3414761A (en) 1968-12-03

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US (1) US3414761A (de)
DE (1) DE1541056B1 (de)
GB (1) GB1126093A (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3870923A (en) * 1972-12-29 1975-03-11 Thomson Csf Magnetron with an improved tuning mechanism
US3876903A (en) * 1974-03-22 1975-04-08 Varian Associates Dither tuned microwave tube
FR2430663A1 (fr) * 1978-07-03 1980-02-01 Sits Soc It Telecom Siemens Dispositif pour l'accord de tubes a micro-ondes
US4234855A (en) * 1978-02-02 1980-11-18 Societa Italiana Telecomunicazioni Siemens S.P.A. System for linearly tuning a microwave oscillator
US4281273A (en) * 1978-10-03 1981-07-28 E M I -Varian Limited Spin tuned magnetron having load sharing bearing arrangements
US4313091A (en) * 1979-02-13 1982-01-26 Societa Italiana Telecomunicazioni Siemens S.P.A. Crankshaft tuning mechanisms for microwave oscillators

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3289035A (en) * 1962-08-10 1966-11-29 Sfd Lab Inc Reverse magnetron having means to suppress undersired modes

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3187220A (en) * 1961-01-30 1965-06-01 Raytheon Co Hydraulically tuned magnetron
FR1372678A (fr) * 1962-08-10 1964-09-18 S F D Lab Magnétron de type inversé

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3289035A (en) * 1962-08-10 1966-11-29 Sfd Lab Inc Reverse magnetron having means to suppress undersired modes

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3870923A (en) * 1972-12-29 1975-03-11 Thomson Csf Magnetron with an improved tuning mechanism
US3876903A (en) * 1974-03-22 1975-04-08 Varian Associates Dither tuned microwave tube
US4234855A (en) * 1978-02-02 1980-11-18 Societa Italiana Telecomunicazioni Siemens S.P.A. System for linearly tuning a microwave oscillator
FR2430663A1 (fr) * 1978-07-03 1980-02-01 Sits Soc It Telecom Siemens Dispositif pour l'accord de tubes a micro-ondes
US4247828A (en) * 1978-07-03 1981-01-27 Societa Italiana Telecomunicazioni Siemens S.P.A. Reciprocating piston tuning mechanism for a microwave oscillator
US4281273A (en) * 1978-10-03 1981-07-28 E M I -Varian Limited Spin tuned magnetron having load sharing bearing arrangements
US4313091A (en) * 1979-02-13 1982-01-26 Societa Italiana Telecomunicazioni Siemens S.P.A. Crankshaft tuning mechanisms for microwave oscillators

Also Published As

Publication number Publication date
GB1126093A (en) 1968-09-05
DE1541056B1 (de) 1971-12-16

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