US3706910A - Coaxial magnetron slot mode suppressor - Google Patents

Coaxial magnetron slot mode suppressor Download PDF

Info

Publication number
US3706910A
US3706910A US147914A US3706910DA US3706910A US 3706910 A US3706910 A US 3706910A US 147914 A US147914 A US 147914A US 3706910D A US3706910D A US 3706910DA US 3706910 A US3706910 A US 3706910A
Authority
US
United States
Prior art keywords
cavity
coaxial
tuning
slots
boundary wall
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
US147914A
Other languages
English (en)
Inventor
Robert J Foreman
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.)
Raytheon Co
Original Assignee
Raytheon Co
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
Application filed by Raytheon Co filed Critical Raytheon Co
Application granted granted Critical
Publication of US3706910A publication Critical patent/US3706910A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

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
    • H01J23/16—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

Definitions

  • ABSTRACT discloses a coaxial cavity magnetron [21] Appl' 147314 provided with a tunable slot mode absorber adapted to be picked up and moved in consort with the main [521 US. Cl. ..315/39.s1, 315/3961, 315/3977 cavity i g means A lossy ceramic g member i [51] Int.
  • the inner system includes a plurality of radially extending vane members defining therebetween resonant cavities circumferentially disposed around a central cathode.
  • An outer system is defined by an outer wall and a common cylindrical anode boundary wall to define a coaxial cavity resonator.
  • the outer system is constructed to oscillate in the TE 1 mode and the inner system is coupled to alternate cavity' resonators by slots extending through the common boundary wall.
  • the inner system is normally designed to operate in the pi-mode and the two systems are locked together by means of the coupling slots.
  • the systems are locked to a desired working mode ofoperation affording high frequency stability with large amounts of energy stored in the coaxial cavity resonator.
  • Other modes referred to as degenerate modes of the TE or TM designation exist in this coaxial resonator.
  • Suggested suppressors in the prior art have included a quarter wave circular choke provided within an end cover adjacent to and coaxial with the anode wall. The interior of the choke is lined with a lossy material such as iron or carbon to absorb the degenerate modes.
  • the vane and slot system behaves in a manner analogous to a helix or delay line slow wave structure and energy is propagated in the common boundary wall as a traveling wave. Nearly all the undesired wave energy is stored in the slots.
  • the structure is reentrant and mode instability can result due to oscillation feedback around the anode wall. These oscillations are generally at lower frequencies than the desired operating mode and start at lower values of applied voltage. In short pulse operating conditions these oscillations can start up on the leading edge of the pulse before the required applied voltage level for the desired operating mode.
  • This mode instability leads to a problem of long standing, namely time jitter.
  • the excellent frequency stability, long life and other advantages of coaxial magnetrons have, therefore, not been widely available for short pulse radar systems to cover wide frequency ranges.
  • Still another slot mode absorber is disclosed in U.S. Pat No. 3,231,781 issued Jan. 25, 1966 to M. F. Liscio wherein the annular mode abosrber is pinned to the anode structure of an inside-out or reverse magnetron with an internal coaxial TE cavity resonator.
  • Another example of the prior art is shown in U.S. Pat. No. 3,471,744 issued Oct. 7, 1969 to G. G. Pryor wherein the slot mode absorber is ring-shaped and formed by a plurality of lossy segments retained within a channel member affixed to the anode wall to provide for thermal expansion.
  • a tunable slot mode absorber for coaxial magnetrons.
  • a unique feature resides in the variable positioning of absorber material, such as a carbonized ceramic within a larger portion of the anode slots over a selected portion of the frequency range.
  • absorber material such as a carbonized ceramic
  • the absorber traverses a predetermined region of a tunable band by being picked up to travel in consort with a plunger type tuning assembly. A varying amount of energy absorbing material is thereby exposed within the slots coupling the respective resonant systems.
  • the slot mode absorber ring member is spring loaded and a pin-guided mechanical spider structure supported by the tuner magnetic pole piece member is actuated when the main bellows-controlled tuning means reaches a predetermined point approaching the high end of the tuning range. In this position the tuning member is closer to the opposing wall of the coaxial cavity resonator in the region where shunt capacitances tend to terminate RF fields in those modes which have energy stored in the slots.
  • X-band device tunable from 8,500 MHz to 9,600 MI-Iz a point at approximately 9,200 MI-Iz was determined to be optimum for actuating movement of the absorber material adjacent to the ends of the slots.
  • Exemplary of the frequency-dependent variable distance for insertion of the absorber the distance between the bottom edge of this member and the top of the anode vanes varied up to approximately 0.l inch closer at the high frequency end than at a fixed position near the lower frequency limit over a range of approximately 400 MHz.
  • the depth of penetration of the lossy material is therefore efficiently maintained to provide for greater suppression of slot modes over wider bandwidths.
  • the effect on mode instability is improved by 45:l over fixed position slot mode absorbers and time jitter readings of less than and nonoseconds are attainable.
  • the new slot mode absorber serves as a power leveling device by presenting losses to the working TE mode in the-area of the tuning means where power outputs are undesirably high. Further, in combination with absorbing material carried by the tuning means to overshadow the slot mode absorbing means the shunt capacitance effect due to the presence of the tuning means in the cavity resonator is overcome. With little additional cost coaxial magnetrons of high mode stability and wide tuning ranges are possible along with the excellent frequency stability and long life.
  • FIG. 1 is a detailed vertical cross-sectional view of the embodiment
  • FIG. 2 is an enlarged cross-sectional view of the tuner pole piece assembly including the slot mode absorber
  • FIG. 3 is an enlarged end view of the assembly shown in FIG. 2;
  • FIG. 4 is a cross-sectional view of the tuner actuating mechanism and the slot mode 7 absorber actuating means
  • FIG. 5 is a cross-sectional view of the tuner actuating mechanism and the slot mode absorber assembly
  • FIG. 6 is a fragmentary cross-sectional view of a tuning ring member incorporating alternate absorber means
  • FIG. 7 is a partial detailed cross-sectional and partial elevational view of an inside-out magnetron embodying the invention.
  • FIG. 1 the illustrative embodiment in FIG. 1 comprises a coaxial magnetron 10 having an envelope 12 defined by upper and lower annular cover members 14 and 16 hermetically sealed to outer cylindrical wall member 18.
  • a plurality of anode vane elements 20 supported at their base end by common boundary wall 22 extend radially inwardly and define therebetween cavity resonators of the inner resonant system circumferentially disposed about a central cathode emitter 24.
  • the cathode 24 is supported by cylindrical member 26 which is in turn supported at its outer end by tubular member 28.
  • Member 28 is secured to magnetic pole piece member 30. Electric leads for energizing the cathode heater 32 as well as the high voltage leads for applying the electric field potentials to operate the device extend within member 28.
  • the inner resonant system is designed to operate in the pi-mode of oscillation over the frequency range which is determined by the outer coaxial resonant system.
  • the magnetron magnetic circuit in addition to the pole piece member 30 includes oppositely disposed inner pole piece member 34 and external C-shaped permanent magnets 36 contacting pole piece adapters 38. Two such external magnets are commonly provided and extend from opposite sides.
  • the magnetic field extends parallel to the axis of the cathode 24 in the interaction region.
  • the electric field also extends transverse to the magnetic field force lines in this region in the manner well known in the art for crossed field devices.
  • An outer coaxial cavity resonator 40 is defined by cylindrical wall 18 and the common boundary anode wall 22 together with the covers 14 and 16. The dimensions of the cavity resonator 40 are selected to provide resonant frequencies over a predetermined frequency band in the TE working mode. Slots 42 in wall 22 permit the coupling and locking of the pi-mode oscillations of the inner system with the TE resonant modes in the coaxial cavity 40. The degenerate TE and TM modes are suppressed by an annular lossy member 44 in end cover 14 and member 46 in a'quarter wave channel choke section 48 in end cover 16. Such materials as carbonized alumina ceramic, barium titanate, and ferrites may be advantageously employed for suppression members 44 and 46.
  • Coaxial resonator 40 is coupled through iris 50 and dumb-bell or substantially I-I-shaped transformer section 52 to a utilization load by means of output waveguide section 54.
  • the waveguide 54 and transformer 52 sections are supported by and inserted within the outer cylindrical-wall 18.
  • the remainder of the coaxial magnetron structure comprises cooling fins (not shown), an exhaust tubulation 56 in wall 18, mounting plate 58 to support the device in a system and anchor plate 60 and screw means 62 adjacent wall 18 to secure the C-shaped magnets to the envelope 12.
  • an axially translated tuning ring 64 is actuated by a tuner mechanism such as a meshing gear and ball bearing structure 70.
  • Post members 72 with screws 74 secure the tuning ring to the threaded tuner shaft 76.
  • a deformable bellows arrangement 78 extends between fixed upper plate member 80 secured to the tuner mechanism and a movable plate and tuner post support member 82 to preserve the vacuum condition within the envelope.
  • the inner portion of member 82 is provided with an adjustable tuner adapter member 84 threadably secured to shaft 76 to couple the absorber pick up means to the tuner mechanism.
  • FIGS. 2-5 inclusive To assist in an understanding of the invention two stages of operation of the assembly 90, namely, the rest position and after pick up by the main tuner mechanism 70, are illustrated in FIG. 1. Those components which are involved in movement are shown in a different position on the right-hand side and have been designated with the suffix a after the applicable reference numerals to indicate the tuning position.
  • Slot mode absorber assembly 90 is movably disposed adjacent to the ends of slots 42. The assembly is supported by inner pole piece member 34 and downward axial displacement results in the introduction of additional lossy material within'the upper ends of the slots 42.
  • the slot mode absorber means include a ringshaped lossy ceramic member 92 carried by sleeve member 94 of a refractory metal, such as molybdenum.
  • the lossy absorbing rind member 92 may, illustratively, be formed from alumina or beryllium oxide material that is porous and is impregnated with carbon formed by firing in a hydrogen atmosphere a coating of a sucrose solution (C H O Lossy ring member 92 is brazed to sleeve member 94 and the components are supported by a mechanical spider arrangement including pin-guiding members 98 secured to plate member 100 with the pins introduced within passageways 102 in four quadrants of the pole piece member 34.
  • the absorber assembly is maintained under tension by means of a high temperature spring- 104 urging against shield member 106.
  • the shield member is in turn affixed and secured to pole piece member 34 adjacent to the end of the cathode assembly 24.
  • the spring forces the absorber assembly upwards to insure proper return to the rest position after a tuning excursion.
  • a spring member of 10 percent tungsten and 90 percent tantalum alloy metal having a load factor of from 6-10 pounds was employed.
  • the adapter member 84 contacts plate member 100 and compresses spring 104 thereby carrying absorber member 92 in consort with the main tuning mechanism 70.
  • the lower limit of the axial travel is fixed by member 82 contacting the upper end of pole piece member 34.
  • a varying amount of lossy material to absorb the undesired slot mode energy is thus provided over high end of the tuning band where the tuning ring 64 is closer to end cover 16.
  • Absorber pick up point Frequency (M112) 8500 In the exemplary embodiment the slot mode absorber at its furthermost point at the low end of the band is spaced a distance of 0.225 inch from the vane 20. In this application for X-band the pick up point was determined to be 9,220 MHz. Other points may be selected for other frequencies or the entire slot mode absorber assembly can be arranged to be carried by the adapter member 84 to have the lossy material exposed throughout the tuning ring 64 excursion.
  • Pole piece member 34 is clearly shown in FIG. 3 and the passageways 102 are shown in each of the quadrants to accommodate the guide four pins 98.
  • FIG. 4 illustrates the tuner mechanism 70 with the outer shell member 108 and top cover 110 secured to end cover 14.
  • FIG. 5 shows the complete tuner mechanism coupled with the slot mode absorber assembly 90.
  • an alternative tuning ring member 64 is shown having an annular lossy ring member 112 adjacent to the inner diameter of this member.
  • the disposition of lossy material will assist in leveling the output power even in the working mode by reducing the capacitive effect of the tuning ring member in cavity 40 as it approaches end cover 16 for even greater mode suppression.
  • I-Iermetically sealed envelope 12 includes a common boundary anode wall 22 with the vane elements 20 extending radially outwardly toward a cathode emitter 114.
  • Interaction region 116 provides the 'rr-mode oscillations and is bounded by cover members 14 and 16 and cylindrical wall member 18.
  • Wall 22 encloses an inner coaxial cavity resonator 118 which operates in circular electric modes. Slots 42 permit coupling of the outer rr-mode oscillations with the inner resonator l 18.
  • the energy is coupled through an iris and impedance transformer section 120 to a load through window 122 in waveguide 124.
  • Magnets 36 again provide the magnetic field circuit in region 116 for the outer anodecathode resonator system.
  • a tuning plate 126 tunes the generated output and is axially actuated by a gear mechanism 70 similar to the structure illustrated in FIG. 1.
  • Bellows 130 contacts movable support member 132 secured to a tuner post 134.
  • the lossy slot mode absorber ring 136 is carried by movable member 138 secured to support member 132 to provide for the introduction of the lossy material in a varying amount in the slots 42 during axial excursion of the tuning plate 126.
  • Spring 140 provides the tensioning to insure return of the slot mode absorber assembly to the rest position.
  • the principal variation then in the inside-out embodiment is the inversion of the movable components to suppress the slot modes from one side of wall 22 to the other side.
  • a resonant system including a plurality of spaced anode members supported by a boundary wall defining therebetween a plurality of cavity resonators and a cathode member to generate high frequency oscillations in the pi-mode;
  • means including said boundary wall defining a coaxial cavity adapted to be resonant in a predetermined electric and magnetic field mode;
  • boundary wall having a plurality of axially extending slots coupling high frequency energy in said anodercathode cavity resonators to said coaxial cavity;
  • a slot mode absorber assembly including a member of a lossy material movably disposed adjacent to the ends of said coupling slots to suppress energy stored therein capable of generating oscillations in modes other than said resonant mode;
  • said lossy material member comprises a carbonized ceramic member.
  • a resonant system including a plurality of spaced anode vane members supported by a cylindrical boundary wall defining therebetween a'plurality of cavity resonators and a cathode member to generate high frequency oscillations in the pimode;
  • said boundary wall defining a coaxial cavity adapted to be resonant in a predetermined electric and magnetic field mode over a frequency band;
  • boundary wall having a plurality of axially extending slots coupling high frequency energy in said anode-cathode cavity resonators to said coaxial cavity;
  • means including an axially translated tuning member disposed within said coaxial cavity to vary the resonant frequency
  • a slot mode absorber assembly including a ring-shaped member of a lossy material movably disposed adjacent to the ends of said coupling slots;
  • a coaxial magnetron comprising:
  • anode member having a plurality of spaced vane members supported by a boundary wall and defining therebetween cavity resonators
  • means including said boundary wall defining a resonant cavity disposed coaxially to said anode member; means for producing transverse electric and magnetic fields;
  • boundary wall having a plurality of axially extending slots coupling said cavity resonators and coaxi l cavity;
  • tuna e slot mode absorber assembly having a member of a lossy material movably disposed adjacent to the ends of said slots;
  • a coaxial magnetron comprising: i
  • said magnetic field producing means including inner pole piece members disposed on opposing sides of said cavityresonators for directing the magnetic field parallel to the axis of said cathode member; said boundary wall having a plurality of axially extending slots coupling said cavity resonators to said coaxial cavity; a tunable slot mode absorber assembly having a member of a lossy material movably disposed adjacent to the ends of said slots; and

Landscapes

  • Microwave Tubes (AREA)
US147914A 1971-05-28 1971-05-28 Coaxial magnetron slot mode suppressor Expired - Lifetime US3706910A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US14791471A 1971-05-28 1971-05-28

Publications (1)

Publication Number Publication Date
US3706910A true US3706910A (en) 1972-12-19

Family

ID=22523441

Family Applications (1)

Application Number Title Priority Date Filing Date
US147914A Expired - Lifetime US3706910A (en) 1971-05-28 1971-05-28 Coaxial magnetron slot mode suppressor

Country Status (5)

Country Link
US (1) US3706910A (enExample)
JP (1) JPS5314191B1 (enExample)
DE (1) DE2225750C3 (enExample)
FR (1) FR2140003B1 (enExample)
IT (1) IT952391B (enExample)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4053850A (en) * 1976-09-23 1977-10-11 Varian Associates, Inc. Magnetron slot mode absorber
US4246512A (en) * 1978-04-25 1981-01-20 English Electric Valve Company Limited Co-axial multi cavity anode magnetrons
US4420710A (en) * 1980-08-14 1983-12-13 English Electric Valve Company Limited Co-axial magnetrons
GB2386749A (en) * 2002-03-16 2003-09-24 Marconi Applied Techn Ltd A magnetron with a dielectric resonator comprising a lossy portion
US20050104523A1 (en) * 2001-02-13 2005-05-19 E2V Technologies (Uk) Limited Magnetron
US20050230387A1 (en) * 2004-04-14 2005-10-20 Michael Regan Insulated RF suppressor for industrial magnetrons
US20100066593A1 (en) * 2008-09-17 2010-03-18 Tetsuya Takashima Magnetron and radar apparatus

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2608673A (en) * 1949-10-25 1952-08-26 Raytheon Mfg Co Electron discharge device
US2692977A (en) * 1951-02-27 1954-10-26 Sperry Corp Resonant cavity wavemeter for microwave energy
US2710945A (en) * 1947-09-26 1955-06-14 Bell Telephone Labor Inc Mode suppression in resonant cavities
US2805362A (en) * 1954-08-12 1957-09-03 Raytheon Mfg Co Mechanical tuning for magnetrons
US2837694A (en) * 1954-09-16 1958-06-03 Raytheon Mfg Co Electron discharge devices
US2877434A (en) * 1945-11-19 1959-03-10 Harold K Farr Mode filter
US3014152A (en) * 1957-12-05 1961-12-19 Jr Earl J Shelton Magnetron mode loading
US3471744A (en) * 1967-09-01 1969-10-07 Varian Associates Coaxial magnetron having a segmented ring slot mode absorber
US3479556A (en) * 1967-09-27 1969-11-18 Sfd Lab Inc Reverse magnetron having an output circuit employing mode absorbers in the internal cavity
US3600629A (en) * 1969-11-12 1971-08-17 Varian Associates Tuner for providing microwave cross-field tubes with an extended temperature stabilized frequency range

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2877434A (en) * 1945-11-19 1959-03-10 Harold K Farr Mode filter
US2710945A (en) * 1947-09-26 1955-06-14 Bell Telephone Labor Inc Mode suppression in resonant cavities
US2608673A (en) * 1949-10-25 1952-08-26 Raytheon Mfg Co Electron discharge device
US2692977A (en) * 1951-02-27 1954-10-26 Sperry Corp Resonant cavity wavemeter for microwave energy
US2805362A (en) * 1954-08-12 1957-09-03 Raytheon Mfg Co Mechanical tuning for magnetrons
US2837694A (en) * 1954-09-16 1958-06-03 Raytheon Mfg Co Electron discharge devices
US3014152A (en) * 1957-12-05 1961-12-19 Jr Earl J Shelton Magnetron mode loading
US3471744A (en) * 1967-09-01 1969-10-07 Varian Associates Coaxial magnetron having a segmented ring slot mode absorber
US3479556A (en) * 1967-09-27 1969-11-18 Sfd Lab Inc Reverse magnetron having an output circuit employing mode absorbers in the internal cavity
US3600629A (en) * 1969-11-12 1971-08-17 Varian Associates Tuner for providing microwave cross-field tubes with an extended temperature stabilized frequency range

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4053850A (en) * 1976-09-23 1977-10-11 Varian Associates, Inc. Magnetron slot mode absorber
US4246512A (en) * 1978-04-25 1981-01-20 English Electric Valve Company Limited Co-axial multi cavity anode magnetrons
US4420710A (en) * 1980-08-14 1983-12-13 English Electric Valve Company Limited Co-axial magnetrons
US20050104523A1 (en) * 2001-02-13 2005-05-19 E2V Technologies (Uk) Limited Magnetron
US7199525B2 (en) 2001-02-13 2007-04-03 E2V Technologies (Uk) Limited Strapped magnetron with a dielectric resonator for absorbing radiation
GB2386749A (en) * 2002-03-16 2003-09-24 Marconi Applied Techn Ltd A magnetron with a dielectric resonator comprising a lossy portion
GB2386749B (en) * 2002-03-16 2005-11-23 Marconi Applied Techn Ltd Magnetron
US20050230387A1 (en) * 2004-04-14 2005-10-20 Michael Regan Insulated RF suppressor for industrial magnetrons
US20100066593A1 (en) * 2008-09-17 2010-03-18 Tetsuya Takashima Magnetron and radar apparatus
US8237608B2 (en) * 2008-09-17 2012-08-07 Furuno Electric Company Limited Magnetron and radar apparatus

Also Published As

Publication number Publication date
FR2140003B1 (enExample) 1977-12-23
DE2225750B2 (de) 1974-03-28
FR2140003A1 (enExample) 1973-01-12
DE2225750A1 (de) 1972-12-14
IT952391B (it) 1973-07-20
DE2225750C3 (de) 1974-12-19
JPS5314191B1 (enExample) 1978-05-16

Similar Documents

Publication Publication Date Title
US4053850A (en) Magnetron slot mode absorber
US3471744A (en) Coaxial magnetron having a segmented ring slot mode absorber
US2466063A (en) High-power high-frequency electron discharge apparatus
US3706910A (en) Coaxial magnetron slot mode suppressor
KR20040044707A (ko) 전자레인지용 마그네트론
US3412285A (en) Coaxial magnetron with rotatable tuning means
US3346766A (en) Microwave cold cathode magnetron with internal magnet
US2496500A (en) Electron discharge device
US2815469A (en) Magnetron oscillators
US3980920A (en) Multi-resonator microwave oscillator
US3614518A (en) Microwave tuner having sliding contactors
US3289035A (en) Reverse magnetron having means to suppress undersired modes
US3078385A (en) Klystron
US2748277A (en) Magnetron noise generators
US3479556A (en) Reverse magnetron having an output circuit employing mode absorbers in the internal cavity
US3317785A (en) Magnetron assembly having dielectric means, external to envelope, for setting the center operating frequency
US2658165A (en) Magnetron tube with cavity resonator
US3379926A (en) Coaxial magnetron having slot mode suppressing lossy material in anode resonators
US3263118A (en) Magnetron having concentric annular tunable resonator utilizing axial plunger and vacuum sealing bellows mounted inside principal envelope wall
US3720889A (en) Electron discharge devices
US2595652A (en) Coupled cavity resonator
US2551614A (en) Tunable magnetron
US3231781A (en) Reverse magnetron with slot mode absorber
US2878415A (en) Electron discharge device
US3154717A (en) Magnetron tube with axially movable tuning means