US3034014A - Magnetron - Google Patents

Magnetron Download PDF

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Publication number
US3034014A
US3034014A US783600A US78360058A US3034014A US 3034014 A US3034014 A US 3034014A US 783600 A US783600 A US 783600A US 78360058 A US78360058 A US 78360058A US 3034014 A US3034014 A US 3034014A
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United States
Prior art keywords
slots
slot
anode
mode
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
US783600A
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English (en)
Inventor
Drexler Jerome
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
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Bell Telephone Laboratories Inc
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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 NL246406A priority patent/NL113213C/xx
Application granted granted Critical
Publication of US3034014A publication Critical patent/US3034014A/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

  • This invention relates to electron discharge devices of the magnetron type and more particularly to a coaxial cavity type of magnetron discharge device.
  • resonators for producing a conventional 1r mode are de fined by a plurality of anode vanes extending radially inwardly from a cylindrical anode block. Instead of being coupled to an output, however, this resonant system is coupled to an outer annular resonant system which surrounds the cylindrical anode block.
  • the two resonant systems are coupled by axially extending slots through the cylindrical anode which connect the outer resonator with alternate ones of the inner resonators. The slots extend beyond the vane region of the anode to suppress current flow around the ends thereof.
  • the anode vanes are made to be approximately a quarter-wavelength long at the TE mode frequency range of the outer resonator so that the anode currents produced by the outer mode see a low impedance in the vane region and are further inhibited from flowing around the elongated slots.
  • the high currents flowing at the base of the anode vanes cause appropriate high voltages to appear at alternate anode tips, thus providing proper conditions for oscillations in the-desired 1r mode. Since the inner resonant system is isolated from the load and since it is also effectively locked in the desired 1r mode, high efiiciency can be attained without producing instability.
  • slot modes Because of energy storage in the coupling slots, however, other spurious modes are produced similar to those of the rising sun magnetron. To reduce this energy storage, damping elements and chokes 'are placed in close proximity to the ends of the slots. This, however, has not proven entirely satisfactory for removing such rising sun slot modes, hereafter referred to simply as slot modes.
  • each slot may be a storage means of inductive and capacitive energy and, hence, a self-resonant circuit. This is clear when one considers the alternating potential difference of opposite sides of the slot which is more pronounced at the middle portion thereof because current tends to discharge around the ends to neutralize such difference.
  • the middleportion therefore, acts as a capacitance while the end portions act as inductances and the slot, as a whole, acts-as a self-resonant tank circuit. Due to inductive coupling between adjacent slots, a slot mode is propagated around the periphery of the conventional coaxial cavity magnetron to form a slot mode pattern representative of the resonant frequency of the slots.
  • the slotsof one group in a coaxialcavity ditferent characteristics For example, when random slot lengths are used, this mode represents the mean selfresonant frequency of all of the slots.
  • the arrangements 7 of the aforementioned application have presented certain Even if slot mode patterns around the anode capacitance. Where the end portions of a slot are widened, this product is increased, while widening the produced by a particular slot mode, may persist through a a region in which a different frequency slot mode is presentif such a region is not long enough to dc-bunch the It is still another object of this invention to prevent bunches of electrons which may be formed by one slot mode from persisting around a substantial part of the electron stream path in a coaxial cavity magnetron.
  • these groups are made sufficiently large so that bunches of electrons which are formed by the slot mode of one group cannotpersist through an adjacent area represented by the slot mode of a successive group.
  • the differ ence in resonant frequency of the various slots in a co axial cavity magnetron be determined solely by diiferences in width thereof, whereby such differences will have a negligible effect on the desired 1r mode of the inner resonant system.
  • the embodiments of this inmagnetron be relatively wide on their end portions with respect to their middle portion, while the slots'of groups adjacent thereto be relatively wide in'their middle portion with respect to their end portion-
  • An increase in the area of the end portions will provide for an increase -of inductive energy storage, while an increase in the width of the slot in the middle portionwill provide a decrease of capacitive energy storage.
  • the self-resonant frequency of any self-resonant circuit is'inversely proportion'al'to the square root of the product of inductance and riphery such that electrons of the magnetron electron 7 middle portion of the slot decreases the product.
  • the slots of one group will exhibit a substantially ditierent resonant frequency than the slots of an adjacent group.
  • the slots of one group in a coaxial cavity magnetron be uniformly wider than the slots of adjacent groups. Because the capacitive storage of a slot is augmerited. so heavily by the capacitance between anode -vanes, the net capacitance is not as greatly affected by changes in width as is the net inductance.
  • FIG; 1 is a sectional view of a magnetron illustrative of one. specific embodiment of this invention
  • FIG. 2 is a sectional viewof the anode vanes and anode wall of the embodiment ofFIG. 1;
  • PEG. 3 is a View, taken'along' lines 3-3 of FIG. 2, showing, in addition, the cathode assembly of the embodiment of FlG. l; 1
  • FIG. 4 is aview, similar to that of FIG. 3, of a magnetron anode and cathode assembly illustrative of an other embodiment of this invention.
  • FIG. 5 is a-development of a magnetronanode wall illustrative of still another embodiment of this invention.
  • FIG. 1 the specific illustrative embodiment of this invention depicted in FIG. 1 comprises a magnetron 9 having a plurality of anode vanes 10 mounted on a cylindrical anode wall member 1 1 as best seen in FIGS. Z'and 3.
  • the vanes 10 extend along only a small portion of the length of. the anode wall member ,11 to which they are attached as by brazing. These vanes define an array of inner cavity'resonators 13. Slots 1?.
  • a heaterelement 19 extends within cathode sleeve 16 and is connectedfto a pair of leads '20.
  • One lead 20 is-connected' to an inner cylindrical terminal conductor 21 and the other to an outer cylindrical and an end to pole piece member 29.
  • Opposite cathode pole piece 15 is a tuning head pole piece 30.
  • An exhaust tubulation 32 extends into the region of tuning pole piece 30 for exhausting the device, as is well known in theart.
  • Encompassing the cylindrical wallinember II is' an outer coaxial cavity resonator 35 in which is positioned a cylindrical groove choke 36;.
  • Choke portion 36, closely adjacent the anode wall 11 separating the inner resonators and the outer coaxial resonator, may advantageously be provided with'a soft iron lining 38 which serves to absorb and thus damp out interfering TE modes having maximum currents in that vicinity.
  • the outer resonator 35 is connected, as through a basically"H-shaped transformer section 40, as is well known in'the art, to a glass filled output wave guide section 41 through which" the energy of the magnetron is transmitted to external circuitry.
  • the transformer section 40 is inserted in the outer wall 42 of the cavity,
  • tuning mechanism 43 Positioned adjacent the tuning end pole piece 39 is tuning mechanism 43. Mounted thereon is a tuning disc 44 which is connected to a tuning screw 45 which, in turn, controls the axial movement of yoke 46. Extending through tuning pole piece 30 are tuning shafts 47 which are connected to yoke 46 and are movable therewith. The shafts 47 extend into the outer resonant cavity 35 and support a tuning ring 49 for motion within the cavity 35 to tune the magnetron, as discussed further below. Sylphon bellows 50 are attached to wall 51 and, by virtue of exhaust holes 48, maintain the vacuum within the magnetron as is well known in the art.
  • the outer cavity resonator 35 is capable of sustaining a number of different modes of operation. In accordance with this invention, however, it is dimensioned, as is well known in the art, for maximum storage of the TE mode in which the magnetic field lines are axial along the upper and lower plates of the cavity and the electric field lines are entirely circumferential. Electric currents induced thereby flow circumferentially along the outer surface of anode wall 11 and along the inner surface of the outer wall 42 of the outer cavity resonator 35. Currents induced by other modes will have an axial component Which will be damped by choke portion 36 thereby, in efiect, damping the mode.
  • the inner resonant system defined by the resonators 13, when considered alone, is a usual unstrapped magnetron system which will tend to oscillate in both the 1: and various degenerate modes.
  • outer cavity resonator 35 and the inner resonators 13 can be considered as two distinct resonant systems; 7
  • Anode vanes 10 are made approximately a quarter-wavelength long in the range of frequencies of the current flowing along wall 11, such that the high impedance termination at the free end of the anode vanes is reflected back to slot 12 as a low impedance, and, accordingly, the said current flows into the resonator and down the adjacent vane. Because such currents are quite high, a high voltage is produced on thevane. These high voltages appear only across alternate anode vanes 10 at a given time because only alternate inner cavity resonators 13 are coupled by slots 12 to the outer cavity resonator 35.
  • the TE mode frequency is therefore the frequency which is utilized.
  • the manner of energy transfer from the inner resonant system to the outer cavity can be appreciated from a consideration of the structure of the inner resonant system.
  • the electron beam of the inner resonant system induces voltages in the tips of anode vanes 16. These voltages, in turn, produce currents which flow out through the slots into the outer cavity resonator. Since the TE mode tends to sustain itself, these currents flowing .along the boundary wall 11 are balanced by currents flowing along outer wall 42. Power is tapped out of the outer cavity resonator at the outer wall 42. Actually, it is, of course, correct to consider both currents, those which flow into the slots from the outer cavity resonator and those which flow out of the slots due to electronically induced voltages, since what is involved here is a matching of the boundary conditions of the two systems.
  • both modes must oscillate at the same frequency.
  • the resonators 13 be so constructed as to support a frequency outside the frequency range of the outer cavity.
  • the frequencies are made substantially independent so that the frequency of the outer mode can be varied by movement of tuningring 49, while minimally affecting the 1r mode of oscillation.
  • Such minimal effects produce no overall deleterious effect unless certain spurious modeswhich are inherent inthe rising sun type of structure of the inner resonant system become prominent. These spurious rising sun modes are produced by energy stored in slots -12 and will hereafter be referred to as slot modes.
  • a uniform slot mode pattern may be propa-- gated around the entire periphery of anode wall 11.
  • Such a uniform solt mode pattern tends to interact with the electron stream which flows in the gap between propagation of a slot mode because coupling can exist between slots which are not adjacent. This coupling, of course, decreases with increased distance between the slots. difference of the self-resonant frequencies is not large. For thorough disrupting of a propagating slot mode then, it is necessary to introduce, along the anode periphery, a
  • Another purpose of the grouping of slots is to prevent a particular bunching or electrons due to a particular slot mode from persisting around the entire electron stream path. Any electromagnetic field caused by a slot or group of slots will tend to bunch the electrons of the electron stream in a particular pattern; As these bunches move along with the electron stream, they give up energy or undesirably interact to producespurious oscillations. If bunches formed by one particular slot mode move into a region of a different slot mode, the bunches may persist in spite of the different field to which they are exposed if such exposure is of relatively .short duration. i A
  • coupling can exist between slots if, the
  • the inductance is directly proportional to the area enclosed thereby.
  • the area enclosed by the ends. of a slot is indicative of the inductive storage thereof, while the width of the middle of the slot 'is vindicative of the capacitive storage.
  • the resonant frequency of any self-resonant circuit is inversely porportional to thesquare root of the product of its inductance and capacitance. Widening the ends of a particular slot will increase the inductive energy stored therein, thereby increasingflthe LC product and trons thereof would be bunched by the slot mode existing along group 53. The slot mode of the next successive slot group, group 52, would exhibit an entirely different field configuration due to the different self-resonant frequencies of the slots therein.
  • FIG; S' is a development of the cylindrical anode 1! illustrating one embodiment of the presentinvention
  • the slots 12 of groups 52 and 52' are widein center with respect to the end portions and thereby exhibit relatively high self-resonant frequencies.
  • the slots of groups 53 and 53' are wide on the ends with respect to the middleportions and thereby exhibit relatively. low s'eli resonant Widening the middle or ,a slot will decrease the electrons bunched by a'preceding slot mode.
  • the desired optimum is arrived at by experiment. While the optimum number of groupings for a 16 slot anode is four, as shown by PEG. 3, the optimum number for a 10 slot anode is two,- asshown by FIG. 4.
  • a magnetron comprising a cathode, a plurality of anode resonators adjacent said cathode, and an output cavity resonator adjacent said anode resonators, said anode resonators and said output cavity resonator having a common wall portion, and means for coupling certain ones of said anode resonators to said output cavity resonaa tor comprising a plurality of groups of adjacent slots in 'said wall portion, the slots of each group exhibiting a substantially uniform self-resonant frequency which is difierent from the self-resonant frequency of the slots of adjacent groups.
  • the change imcapacitancediieto change in slot width is smallin'comparisonto the change in inductance.
  • The, slots 12 of groups 52 and 52 are relatively narrow such that the quantity of inductive energy stored therein is relatively small and hence the slots exhibit relatively high self-resonant frequencies.
  • the slots ofgroups 53 and" 53 on the otherhand, are relatively wide such that the inductive energy stored therein is relativelyv large and hence'the slots exhibit relatively low self-resonant frequencies.
  • a grouping such as52 must be long- 3.
  • eachof said groups containing a total of four slots.
  • a magnetron comprising a cylindrical cathode for forming and projecting a stream of electrons, a cylindrical anode wall surrounding said cathode'and coaxial there with, an array of anode vanes extending radially inwardly from said anode wall and defining a plurality of anode resonators, means including said anode wall defining an outer cavity resonator, and means for coupling certain ones of said'anode resonators with said outer resonator, said last mentioned means comprising groups of adjacent slots extending through said cylindrical anode wall, a first group" of slots being characterized by afirst slot mode which modulates said electron beam to form bunche's of electrons therein, a second group of slots,
  • adjacent said first group being characterized by a second demodulate substantially said electron beam with respect to said bunches produced by said first slot mode.

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

Priority Applications (8)

Application Number Priority Date Filing Date Title
NL246406D NL246406A (forum.php) 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
NL246406A NL113213C (forum.php) 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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US3034014A true US3034014A (en) 1962-05-08

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US783597A Expired - Lifetime US2976458A (en) 1958-12-29 1958-12-29 Magnetron

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US783597A Expired - Lifetime US2976458A (en) 1958-12-29 1958-12-29 Magnetron

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BE (1) BE585286A (forum.php)
CH (1) CH379648A (forum.php)
DE (1) DE1184426B (forum.php)
FR (1) FR1241663A (forum.php)
NL (2) NL113213C (forum.php)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3157818A (en) * 1961-10-18 1964-11-17 Bell Telephone Labor Inc Coaxial cavity magnetron tuning ring
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
US3225249A (en) * 1962-04-27 1965-12-21 Gen Electric Magnetron having evacuated discharge sub-assembly united with unevacuated magnetic and resonant cavity structure
US3229152A (en) * 1961-10-19 1966-01-11 Gen Electric Magnetron having evacuated discharge subassembly united with unevacuated magnetic andresonant cavity structure
US3310704A (en) * 1959-08-06 1967-03-21 Varian Associates Output coupling circuit for microwave tube apparatus
US3381168A (en) * 1964-12-01 1968-04-30 Westinghouse Electric Corp Frequency stable coaxial magnetron utilizing low coefficient of thermal expansion material
US3395314A (en) * 1964-11-24 1968-07-30 Westinghouse Electric Corp Coaxial magnetron having attenuator means for suppressing undesired modes
US3412283A (en) * 1965-10-15 1968-11-19 Westinghouse Electric Corp Coaxial magnetron in which the anode is welded to the body
US3414760A (en) * 1965-10-15 1968-12-03 Westinghouse Electric Corp A frequency diversity coaxial magnetron
US3478247A (en) * 1967-06-12 1969-11-11 Litton Precision Prod Inc Microwave tuner having a rapid tuning rate
US3478246A (en) * 1967-05-05 1969-11-11 Litton Precision Prod Inc Piezoelectric bimorph driven tuners for electron discharge devices
US3875470A (en) * 1972-12-21 1975-04-01 English Electric Valve Co Ltd Combined magnetron and resonant stabilizing filter
US4420710A (en) * 1980-08-14 1983-12-13 English Electric Valve Company Limited Co-axial magnetrons

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL277268A (forum.php) * 1961-04-26
FR1391037A (fr) * 1964-01-15 1965-03-05 Lignes Telegraph Telephon Procédé perfectionné de réalisation de structures anodiques de magnetrons et magnétrons en résultant

Citations (4)

* 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
US2821659A (en) * 1954-11-18 1958-01-28 Bell Telephone Labor Inc Magnetron
US2854603A (en) * 1955-05-23 1958-09-30 Bell Telephone Labor Inc Magnetrons

Family Cites Families (1)

* 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

Patent Citations (4)

* 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
US2821659A (en) * 1954-11-18 1958-01-28 Bell Telephone Labor Inc Magnetron
US2854603A (en) * 1955-05-23 1958-09-30 Bell Telephone Labor Inc Magnetrons

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3310704A (en) * 1959-08-06 1967-03-21 Varian Associates Output coupling circuit for microwave tube apparatus
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
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
US3412283A (en) * 1965-10-15 1968-11-19 Westinghouse Electric Corp Coaxial magnetron in which the anode is welded to the body
US3414760A (en) * 1965-10-15 1968-12-03 Westinghouse Electric Corp A frequency diversity coaxial magnetron
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
US3875470A (en) * 1972-12-21 1975-04-01 English Electric Valve Co Ltd Combined magnetron and resonant stabilizing filter
US4420710A (en) * 1980-08-14 1983-12-13 English Electric Valve Company Limited Co-axial magnetrons

Also Published As

Publication number Publication date
NL246406A (forum.php)
BE585286A (fr) 1960-04-01
FR1241663A (fr) 1960-12-28
DE1184426B (de) 1964-12-31
CH379648A (de) 1964-07-15
US2976458A (en) 1961-03-21
NL113213C (forum.php) 1966-09-15

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