US2976458A - Magnetron - Google Patents

Magnetron Download PDF

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Publication number
US2976458A
US2976458A US783597A US78359758A US2976458A US 2976458 A US2976458 A US 2976458A US 783597 A US783597 A US 783597A US 78359758 A US78359758 A US 78359758A US 2976458 A US2976458 A US 2976458A
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United States
Prior art keywords
slots
anode
slot
coupling
magnetron
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
US783597A
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English (en)
Inventor
Feinstein Joseph
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.)
AT&T Corp
Original Assignee
Bell Telephone Laboratories Inc
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
Priority to NL246406D priority Critical patent/NL246406A/xx
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US783597A priority patent/US2976458A/en
Priority to US783600A priority patent/US3034014A/en
Priority to DEW26708A priority patent/DE1184426B/de
Priority to FR811835A priority patent/FR1241663A/fr
Priority to BE585286A priority patent/BE585286A/fr
Priority to CH8169559A priority patent/CH379648A/de
Priority to GB4242259A priority patent/GB874105A/en
Priority to NL246406A priority patent/NL113213C/xx
Application granted granted Critical
Publication of US2976458A publication Critical patent/US2976458A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • H01J25/54—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 only one cavity or other resonator, e.g. neutrode tubes
    • H01J25/55—Coaxial cavity magnetrons

Definitions

  • the slots are made to extend beyond the limits of the anode resonators .and thereby permit suitable damping elements to bepositioned in close proximity to the ends thereof for removing or suppressing any undesirable electric modes.
  • the inner reosnant system is designed to oscillate in the 1r mode, While the outer system is designed to oscillate in the TEou mode, the two systems being effectively locked together by means of coupling slots previously described.
  • the ⁇ aforementioned coaxial cavity magnetron appreciably solves these problems through lthe use of the outer output cavity. Because the inner resonant system is isolated from the output coupling means, vchanges in load have very little effect thereon.
  • a structural arrangement as disclosed in the aforementioned Collier et al. patent substantially overcomes the problem vof interfering modes without requiring straps; This is accomplished in the coaxial cavity magnetron partly by the specific geometry of the inner and outer resonant systems and also by the manner in which the undesiredmodes of this type are effectively loaded.
  • the elimination of straps is a distinct advantage in that1 in structures4 built to producevery high frequencies lstraps ,becomequite small land ,mechanicallyfdiiiicult .to ⁇ incorporate ⁇ into the magnetron 'anode structure. More- ICC over, the rsmall spacing results in excessive copper loss and therefore lower magnetron efliciency.
  • the coaxial magnetron removes certain of these slot modes, however, through the use of damping elements at the ends of the coupling slots which absorb energy stored therein.
  • damping elements have been found to be effective in removing specific slot modes, but they have not proven completely satisfactory in removing all of the interfering slot modes, mainly because the respective frequencies of s'uch modes vary over a considerably wide range.
  • VIt. is another object of this invention to obviate the necessity of using attenuating elements in the oscillatory system of a coaxial cavity magnetron.
  • a magnetron comprises an inner and an outer resonant system.
  • the inner resonant system comprises a plurality of inner resonant cavities defined by a plurality of anode vanes extending inwardly Afrom a cylindrical anode.
  • the outer resonant system surrounds the cylindrical anode and is coupled to alternate ones of the inner resonant cavities through coupling slots in the cylindrical anode.
  • the anode vanes are arranged to be approximately one-quarter Wavelength long at the frequency of the outer cavity resonator. This assures that the slots present a low impedance to the currents of the desired mode of the outer cavity resonator whether it be oscillating at the same or a different frequency from that of the inner resonant system.
  • nonuniformities are introduced into the slot system which couples the inner and outer resonant cavities.
  • Such non-uniformities may be employed to disrupt the propagation of an electromagnetic slot mode about the periphery of the cylindrical anode by weakening the coupling between adjacent slots, by altering the phase shift between adjacent slots, by altering the self-resonant frequency of successive slots, or by a combination of4 any of the i foregoing.
  • the electrical energy stored in the connected slots is also elfectivelyconnected such that the phase shift between each coupling slot of the group is.r substantially zero.
  • a slot modefis I propagated by magnetic coupling between adjacent coupling slots, a given slot mode being defined byftli'ejl 3 phase shift between adjacent slots of its field pattern.
  • a slot mode which is propagating along the periphery of the cylindrical anode with some certain discrete phase shift between each coupling slot is disrupted when it encounters a group of slots which represents a substantially zero phase shift.
  • the coupling slots of a coaxial cavity magnetron be of varying lengt
  • the quantity of energy stored in various slots can be varied in accordance with the length of the slots, as will be more fully discussed hereinafter.
  • Fig. l is a perspective sectional view of a magnetron illustrative of one embodiment of this invention.
  • Fig. 2 is a development of the cylindrical anode of Fig. 1',
  • Fig. 3 is a development of a cylindrical anode of a coaxial cavity magnetron illustrative of another embodiment of this invention.
  • Fig. 4 is a development of a cylindrical anode of a coaxial cavity magnetron illustrative of still another embodiment of this invention.
  • Fig. 5 is a diagram of the electric and magnetic fields which are produced within a slot due to an alternating voltage across the sides thereof.
  • Fig. l the specific illustrative embodiment of this invention depicted in Fig. l comprises a coaxial cavity magnetron having a cylindrical cathode 1G.
  • a cylindrical anode 11 Surrounding the cathode 10 is a cylindrical anode 11 having a plurality of vanes 12 which extend radially inwardlytherefrom.
  • the planes of anode vanes 12 are parallel with the axis of cylindrical anode 11 andrdetine an array of inner cavity resonators 13.
  • Coupling slots 14 extend through cylindrical anode 11 and are centered between adjacent anode vanes 12. These slots communicate with alternate ones of the cavity resonators 13.
  • an outer wall member 15 Surrounding the cylindrical anode 11 is an outer wall member 15 which, together with the cylindrical anode 11, defines an outer cavity resonator 16. Extending through wall member 15 such as tocommunicate with cavity resonator 16 is an output coupling slot 17.
  • the envelope, output wave guide means, tuning means, input means, and various other elements of the coaxial cavity magnetron haveV not been shown. Such elements and their functions are described in the aforementioned patent and are known in the art.
  • the outer cavity resonator I 15 is designed to support the TEMI mode, while the inner cavity resonators 13 are designed to support the rr mode of oscillation.
  • Anode vanes 12 are advantageously one-quarter wavelength long at the TEMI mode frequency range of oscillation such that the high impedance at the inner ends thereof is reected at the base as a low impedance, thus causing TEUU mode currents to flow through coupling slots 14 and lock the two resonant sys tems together, as described in the aforementioned patent.
  • Coupling slots 14 extend considerably beyond the limits of anode vanes 12 so as to prevent the anode currents in the region of vanes y12 from flowing around the slots.
  • certain coupling slots 14 are connected by transverse slots 18 as best seen in Fig. 2. These transverse slots effectively provide a short circuit between the coupling slots so connected insofar as energy stored therein is concerned. Such direct coupling results in a substantially zero. phase shift between slots 14 so connected, rather than a certain discrete phase shift between slots that are coupled solely by induction.
  • any electromagnetic mode is defined by a certain periodic phase shift.
  • random non-uniformities are introduced into the coupling system of a coaxial cavity magnetron, as described above, which alter the periodicity of this phase shift, a uniform slot mode is prevented ⁇ from propagating around the anode periphery.
  • the slot modes When one considers the slot modes as standing waves, they can be considered to have been broken up into a series, each existing along only a small portion of the anode periphery and therefore being prohibited from effectively interacting with the electron beam.
  • Fig. 3 illustrates another embodiment of this invention wherein certain coupling slots 14 of a conventional coaxial cavity magnetron are omitted.
  • the distance between certain adjacent coupling slots in the array is relatively great. Since the propagation of a slot mode depends upon magnetic coupling between adjacent slots, such propagation may be eliminated by the absence of a slot. Even if coupling between displaced slots does exist, it will be so weak that that periodicity of the slot mode propagated thereby will be seriously disrupted. With several slots randomly omitted as shown, any slot mode pattern around the anode 11 will be effectively broken up.
  • p Fig. 4 is illustrative of another embodiment of the -invention wherein the slots 14 are of randomly varying length.
  • the effect of such asymmetries in the coupling system of a coaxial cavity magnetron can be appreciated from a consideration of the energy stored in each slot.
  • the middle portion of the slot may be considered to be a capacitor.
  • Such voltage tends to produce a current flowing around the ends of the slot, giving rise to inductive energy storage at the slot ends.
  • a maximum capacitive storage therefore, occurs at the center of the slot, with such storage uniformly tapering to zero at the ends thereof, while a maximum inductive storage occurs at the slot ends and uniformly tapers to zero at the center.
  • the capacitive energy storage produces an electric field proportional thereto as designated by arrows 19 of Fig. 5. The. length of these arrows indicates the strength of the electric field at various distances along the length of Va slot.
  • the magnetic field which is produced by the inductive energy storage is perpendicular to the electric field and is represented by Icircles 20. Dotted circles represent flux lines leaving the paper, while crossed -circles represent flux lines entering the paper. The size of the circles indicates the strengthof the magnetic field 'at various distances along the length of a slot. Due to Vcapacitive and inductive storage, the slot considered is essentially a resonator. It iscle'ar' from a study ⁇ of Fig.
  • dissipative rings were positioned near the ends of the slots for slot mode suppression.
  • the instant invention may be used without such dissipative rings in many cases since the nonuniformities in the coupling system may provide sufficient slot mode suppression, or it may be used in conjunction therewith, when desired, to provide even more effective suppression.
  • a magnetron comprising a wall member, a plurality of anode vanes positioned on said Wall member and defining anode cavity resonators, a cathode positioned adjacent said vanes, means including said wall member defining an output cavity resonator, means comprising an array of slots extending through said wall member for coupling certain ones of said anode cavity resonators to said output cavity resonator, said slots giving rise to spurious slo-t modes, and means ⁇ for suppressing said spurious slot modes comprising anray non-uniformities in said array of slots.
  • a magnetron comprising a wall member, a plurality of anode vanes positioned on said wall member and defining anode cavity resonators, a cathode positioned adjacent said vanes, means including said wall member defining an output cavity resonator, and means comprising an array of slots extending through said wall member for coupling certain ones of said anode cavity resonators to said output cavity resonator, the spacing between certain successive ones of said slots being greater than the spacing between certain other successive ones of said slots.
  • a magnetron comprising a wall member, a plurality of anode vanes ⁇ positioned on said wall mem-ber and defining anode cavity resonators, a cathode positioned adjacent said vanes, means including said wall member defining an output cavity resonator, and means comprising Van array of slots extending through said wall member for coupling certain ones of said anode cavity resonators to said output cavity resonator, certain ones of said slots being interconnected by other slots trans-Y nator, said slots' giving' riseto spurious slot modes,"a'nd means lfor suppressing the propagation of spurious slot vmodes. alongthe periphery off-said cylindrical wall memyber comprising other ⁇ elongated slots extending through s'aid cylindrical' wall, said other elongated slots'each interconnecting a plurality of said elongated coupling slots.
  • a magnetron comprising a cylindrical cathode, a cylindrical anode surrounding said cathode and coaxial therewith, an outer wall member surrounding said cylindrical anode and defining therewith an output cavity resonator, a plurality of vanes extending radially inwardly from said cylindrical anode and defining a circular array of anode cavity resonators, the planes of each of said vanes being parallel with the axis of said cylindrical anode, a coupling system comprising an array of slots extending through said cylindrical anode and parallel with the axis thereof lfor coupling certain ones of said anode cavity resonators to said output cavity resonator, said slots giving rise to spurious lslot modes, and means for suppressing the propagation of spurious slot modes around the ent-ire periphery of said anode comprising non-uniformities in said coupling system.
  • a magnetron comprising a cylindrical cathode, a cylindrical anode surrounding said cathode and coaxial therewith, an outer wall member surrounding said cylindrical anode and defining therewith an output cavity resonator, a plurality of vanes extending radially inwardly from said cylindrical anode and defining a circular array of anode cavity resonators, the planes of each of said vanes being parallel with the axis of said cylindrical anode, and a coupling system comprising an array of slots extending through said cylindrical anode and parallel with the ax-is thereof for coupling certain ones of said anode cavity resonators to said output cavity resonator, a majorityof pairs of successive ones of said slots having therebteween two of said vanes, and a minority of pairs of successive ones of said slots having therebetween 'four of said vanes.
  • an inner resonant system comprising a cylindrical wall plate having a plurality of vanes equally Y u distributed non-uniformities in the resonant characteristics of said slots.
  • transverse slots being removed from the locationv of said vanes.
  • a magnetron comprising a wall member, a plurality of anode vanes positioned on said 'wall member and defining anode cavity resonators, a cathode positioned adjacent said vanes, means including said wall member defining an output cavityresonator, and means comprising an array of slots extending through said 'wall member Vfor coupling certain of said anode cavity resonators with said -output cavity, adjacent slots having different resonant characteristics in at least part of said array for suppressing spurious slot modes.

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  • Microwave Tubes (AREA)
US783597A 1958-12-29 1958-12-29 Magnetron Expired - Lifetime US2976458A (en)

Priority Applications (9)

Application Number Priority Date Filing Date Title
NL246406D NL246406A (en(2012)) 1958-12-29
US783597A US2976458A (en) 1958-12-29 1958-12-29 Magnetron
US783600A US3034014A (en) 1958-12-29 1958-12-29 Magnetron
DEW26708A DE1184426B (de) 1958-12-29 1959-11-12 Magnetronroehre der Radbauart
FR811835A FR1241663A (fr) 1958-12-29 1959-12-01 Magnétron
BE585286A BE585286A (fr) 1958-12-29 1959-12-03 Magnétron.
CH8169559A CH379648A (de) 1958-12-29 1959-12-10 Magnetronröhre
GB4242259A GB874105A (en) 1958-12-29 1959-12-14 Improvements in or relating to magnetrons
NL246406A NL113213C (en(2012)) 1958-12-29 1959-12-14

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US783597A US2976458A (en) 1958-12-29 1958-12-29 Magnetron
US783600A US3034014A (en) 1958-12-29 1958-12-29 Magnetron

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US2976458A true US2976458A (en) 1961-03-21

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US783600A Expired - Lifetime US3034014A (en) 1958-12-29 1958-12-29 Magnetron

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US783600A Expired - Lifetime US3034014A (en) 1958-12-29 1958-12-29 Magnetron

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BE (1) BE585286A (en(2012))
CH (1) CH379648A (en(2012))
DE (1) DE1184426B (en(2012))
FR (1) FR1241663A (en(2012))
NL (2) NL113213C (en(2012))

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3223882A (en) * 1961-03-24 1965-12-14 Gen Electric Traveling wave electric discharge oscillator with directional coupling connections to a traveling wave structure wherein the number of coupling connections times the phase shift between adjacent connections equal an integral number of wavelengths
US3444428A (en) * 1964-01-15 1969-05-13 Lignes Telegraph Telephon Magnetron anode blocks
US3875470A (en) * 1972-12-21 1975-04-01 English Electric Valve Co Ltd Combined magnetron and resonant stabilizing filter

Families Citing this family (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3169206A (en) * 1959-08-06 1965-02-09 Varian Associates High frequency tube method and apparatus
NL277268A (en(2012)) * 1961-04-26
US3157818A (en) * 1961-10-18 1964-11-17 Bell Telephone Labor Inc Coaxial cavity magnetron tuning ring
US3229152A (en) * 1961-10-19 1966-01-11 Gen Electric Magnetron having evacuated discharge subassembly united with unevacuated magnetic andresonant cavity structure
US3225249A (en) * 1962-04-27 1965-12-21 Gen Electric Magnetron having evacuated discharge sub-assembly united with unevacuated magnetic and resonant cavity structure
US3395314A (en) * 1964-11-24 1968-07-30 Westinghouse Electric Corp Coaxial magnetron having attenuator means for suppressing undesired modes
US3381168A (en) * 1964-12-01 1968-04-30 Westinghouse Electric Corp Frequency stable coaxial magnetron utilizing low coefficient of thermal expansion material
US3414760A (en) * 1965-10-15 1968-12-03 Westinghouse Electric Corp A frequency diversity coaxial magnetron
US3412283A (en) * 1965-10-15 1968-11-19 Westinghouse Electric Corp Coaxial magnetron in which the anode is welded to the body
US3478246A (en) * 1967-05-05 1969-11-11 Litton Precision Prod Inc Piezoelectric bimorph driven tuners for electron discharge devices
US3478247A (en) * 1967-06-12 1969-11-11 Litton Precision Prod Inc Microwave tuner having a rapid tuning rate
GB2081969B (en) * 1980-08-14 1984-04-18 English Electric Valve Co Ltd Suppression of slot modes in co-axial magnetrons

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2446826A (en) * 1943-04-14 1948-08-10 Gen Electric Magnetron
US2734148A (en) * 1950-04-03 1956-02-07 Magnetron tube
US2854603A (en) * 1955-05-23 1958-09-30 Bell Telephone Labor Inc Magnetrons

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB611505A (en) * 1943-11-19 1948-11-01 Marconi Wireless Telegraph Co Electron discharge device and associated circuit
US2821659A (en) * 1954-11-18 1958-01-28 Bell Telephone Labor Inc Magnetron

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2446826A (en) * 1943-04-14 1948-08-10 Gen Electric Magnetron
US2734148A (en) * 1950-04-03 1956-02-07 Magnetron tube
US2854603A (en) * 1955-05-23 1958-09-30 Bell Telephone Labor Inc Magnetrons

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3223882A (en) * 1961-03-24 1965-12-14 Gen Electric Traveling wave electric discharge oscillator with directional coupling connections to a traveling wave structure wherein the number of coupling connections times the phase shift between adjacent connections equal an integral number of wavelengths
US3444428A (en) * 1964-01-15 1969-05-13 Lignes Telegraph Telephon Magnetron anode blocks
US3875470A (en) * 1972-12-21 1975-04-01 English Electric Valve Co Ltd Combined magnetron and resonant stabilizing filter

Also Published As

Publication number Publication date
NL246406A (en(2012))
DE1184426B (de) 1964-12-31
FR1241663A (fr) 1960-12-28
BE585286A (fr) 1960-04-01
NL113213C (en(2012)) 1966-09-15
US3034014A (en) 1962-05-08
CH379648A (de) 1964-07-15

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