US3792306A

US3792306A - Multisignal magnetron having plural signal coupling means

Info

Publication number: US3792306A
Application number: US00312180A
Authority: US
Inventors: W Smith; J Butler
Original assignee: Raytheon Co
Current assignee: Raytheon Co
Priority date: 1972-12-04
Filing date: 1972-12-04
Publication date: 1974-02-12
Anticipated expiration: 1991-02-12

Abstract

A crossed field microwave energy device of the magnetron type is provided with a reentrant cavity resonator circuit having isolated groupings of elements to simultaneously yield separate resonant frequencies through energy exchanging relationship with a common electron space charge circulating in the interaction region adjacent to the circuit. In an illustrative embodiment two frequencies, f1 and f2, are provided by interaction with group of strapped anode vanes interrupted by intermediate inactive drift regions. The tube is operated under either pulsed or continuous wave conditions. Separate output antenna means couple energy from each circuit to a utilization load.

Description

United States Patent 1191 Smith et al.

1 1 MULTISIGNAL MAGNETRON HAVING PLURAL SIGNAL COUPLING MEANS [75] Inventors: William A. Smith, Winchester; John R. Butler, Lexington, both of Mass.

[73] Assignee: Raytheon Company, Lexington,

Mass.

[22] Filed: Dec. 4, 1972 [21] Appl. No.: 312,180

[52] US. Cl 315/3957, 315/3959, 315/3967, 315/3969 [51] Int. Cl. HOlj 25/50 [58] Field of Search. 315/513, 39.51, 39.57, 39.59, 315/3967, 39.69; 328/230, 233

1 1 Feb. 12, 1974 3,136,027 6/1964 llcitz ct a1 315/3969 X 3,176,188 3/1965 Wilbur 315/3969 3,536,953 10/1970 Van De Goor 315/3951 [5 7] ABSTRACT A crossed field microwave energy device of the magnetron type is provided with a recntrant cavity resonator circuit having isolated groupings of elements to simultaneously yield separate resonant frequencies through energy exchanging relationship with a common electron space charge circulating in the interaction region adjacent to the circuit. In an illustrative embodiment two frequencies, f and f are provided by interaction with group of strapped anode vanes interrupted by intermediateinactive drift regions. The tube is operated under either pulsed or continuous wave conditions. Separate output antenna means couple energy from each circuit to a utilization load.

10 Claims, 6 Drawing Figures PATENTEDFEBIZIBH 3,792,306

SHEET 1 {IF 2 PAIENTED I 2 I974 3, 782 306 sum 2 or 2 AMPLITUDE SCALE lOdb/CM +1 2 2450 MH 2550 MH MULTISIGNAL MAGNETRON HAVING PLURAL SIGNAL COUPLING MEANS BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to microwave energy generators of the magnetron type and, more particularly, to a cavity resonator circuit for such devices.

2. Description of the Prior Art The magnetron energy generator typically comprises a cylindrical anode member having a plurality of circumferentially disposed cavity resonators formed by spaced conductive elements, such as vanes, extending radially from the inner periphery of the anode wall. A central cathode emitter is disposed along the magnetron axis and defines with the anode cavity resonator elements an electron interaction region. The anode is biased at a potential of, illustratively, 4 to 6 kilovolts with respect to the cathode to establish a direct electric field between these electrodes extending transverse to the tube axis. A magnetic field is typically provided by externally mounted electromagnets or permanent magnets with the field extending parallel to the magnetron axis. Crossed electric and magnetic fields are thus provided within the interaction region. Electrons emitted from the cathode are accelerated toward the anode cavity resonators and rotate in a substantially circular orbital to form a rotating spoke-like space charge. An electromagnetic wave is propogated along the magnetron anode which forms a slow wave circuit. A net transfer of energy from the electrons in the beam to the electromagnetic waveis achieved when a synchronous velocity relationship is'established.

The magnetron anode structure is capable of supporting different propagation modes and the desired mode for the most effective operation is the pi-mode where adjacent anode vane tips are instantaneously 180 out'of-phase with respect to each other. To assist in mode stabilization magnetron anode structures are commonly provided with conductive straps joining alternate vane elements. Typically,-such staps are ar* ranged in pairs coaxially on one or both sides of the vane elements in close proximity to the interaction region. The magnetron anode structure is a continuous uniform and reentrant configuration and is resonant at frequencies for which it is an integral number of wavelengths long at a desired single frequency in a desired operating mode determined by the parameters of the circuit elements comprising the anode cavity resonator structures.

The magnetron generatres frequencies in the microwave region of the electromagnetic energy spectrum which is defined as having wavelengths in the order of from 30 centimeters to l millimeter and frequencies in excess of 1,000 MHz. The energy is coupled from the magnetron by means of an output antenna member secured to one of the vane elements. The outer portion of the conductive antenna is disposed with a dome member of a dielectric material. Additional details relative to the magnetron generators may be obtained from the text Microwave Magnetrons," Radiation Laboratory Series, Vol. 6, by G. B. Collins, McGraw- Hill Book Company, Inc., New York 1948.

need arises for the provision of plural fixed resonant frequencies which would require the utilization of separate magnetron generators each operating at a predetermined frequency. Through the introduction of spurious noise coupled to each of the generated frequencies by externally coupled mismatch load means it is possible to have a useful device for jamming radio signals.

SUMMARY OF THE INVENTION In accordance with the invention a magnetron generator is provided having in a unitary envelope plural isolated resonant slow wave circuits tuned to independent frequencies. Groupings of interconnected anode vane elements are provided by interrupting the strapping in I opposing quadrants thereby creating active resonator sectors separated by inactive drift regions. The net transfer of energy between the electrons in the interaction region and the waves on each resonator circuit will result in the simultaneous generation of plural frequency output signals. In one embodiment a common cathode serves the plural isolated resonant slow wave circuits and an output antenna probe is coupled to one vane element in each sector. The plural antennae are disposed within a common dielectric dome member. The interrupted strapping technique represents a means for varying the slow wave circuit parameters of the isolated cavity resonator groups. Other techniques include variation of the circuit parameters by variations in the pitch of the vane elements to achieve different synchronous relationships between the electrons and the waves in independent sectors of the interaction region. The radical depth of the interaction region may also be varied by tapering of the cathode emitter surfaces.

Additionally, the simultaneous operation of plural frequency signal outputs may be achieved by a stacked array of plural isolated reentrant anode slow wave circuits tuned to separate frequencies with a common cathode in a single envelope. The generation simultaneously of multisignal outputs'represents a simple and inexpensive concept which is readily implemented utilizing known techniques in the magnetron tube art for establishing plural energy exchanging synchronous relationships.

BRIEF DESCRIPTION OF THE DRAWINGS Details of the invention will be readily understood after consideration of the following detailed description and reference to the accompanying drawings wherein:

FIG. 1 is a detailed partially cross-sectional and partially isometric view of a magnetron embodying the invention;

FIG. 2 is a cross-sectional view taken along the line 2-2 in FIG. 1;

FIG. 3 is an enlarged fragmentary view of a portion of the embodiment circumscribed by the circle 3-3;

FIG. 4 is a cross-sectional view of a portion of an alternative embodiment of the invention;

FIG. 5 is a cross-sectional view of a portion of another alternative embodiment of the invention; and

FIG. 6 is a diagrammatic presentation of the output signal waveform measured with an exemplary embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, FIGS. 1 and 2, illustrate a magnetron l0 employing the interrupted strapped anode vane element technique for the simultaneous generation of plural frequency outputs. Anode member 12 comprises a conductive cylinder with a plurality of circumferentially disposed cavity resonators 14 defined by vane elements 16 supported at one end by and extending radially from anode 12. An axially disposed cathode emitter l8, illustratively, of the thoriated tungsten coil type is provided with end shields 20. The emitted electrons are directed in a circular orbit within an interaction region 22 between the cathode and ends of the anode vanes. The cathode emitter assembly is connected and supported by

electrical leads

24, 26 and 28 extending axially from one end of the anode member 12 through the supporting structure including collar 30 and dielectric tubular member 32. The central lead 26 is connected to upper end shield with the

outer leads

24 or 28 being connected to the lower shield 20. Appropriate electrical voltages for the operation of the magnetron are provided by

leads

14 or 28 and central lead 26. A box-like conductive enclosure 34 provides for the coupling of the cathode leads to external circuitry through a shielded by-pass capacitor filter arrangement. Box member 34 is secured to magnetic return path plate member 36 and

external jacks

38 and 40 are provided for connection to the high DC rectified voltage source.

The magnetic field extending parallel to the magnetron axis is provided by means of conical-shaped inner pole piece members 42 and 44 hermetically sealed to the ends of anode 12 to form the tube envelope. The electric potentials are directed transversely to the magnetic field within the anode-cathode interaction region 22.

Permanent magnets

46 and 48 are supported by plate member 36 and are provided with axial passageways 50 to accommodate the cathode leads and supporting structure. To shape the magnetic field paths within the interaction region opposing

bar buckle magnets

52, 54 having opposite polar designations are supported by the U-shaped magnetic field return path member 56 which engage plate member 36 and provide for a closed magnetic field path. Cooling fins 58 contact the outer walls of the anode member 12 and provide for directing a circulating fluid medium to effectively remove the heat generated by the high frequency oscillations within the magnetron.

The strap interruption technique utilized in the practice of the invention will now be described with reference being directed to FIGS. 2 and 3. The anode vane elements 16 extend radially' from anode wall 12.

Conductive straps

60 and 62 coaxially disposed around the cathode 18 are interrupted in order that the anode slow wave circuit is divided into four quadrants. The conductive straps are disposed on opposing sides of the vane elements and contact alternate elements to provide the circuit parameters well-known in the art for pi-mode magnetron oscillation.

Notches

64 and 66 having a

step portion

68 and 70 are provided as shown in FIG. 3 to evolve the alternate strapping arrangement. Two opposite quadrants have the strap members short circuited by brazing both straps to the vanes to produce inactive drift regions between the'remaining quadrants. Vane element 16a and 16h as well as 16(- and 16d, therefore, form the intermediate inactive drift regions. The remaining vane elements are strapped in the normal arrangement to provide a first sector 72 encompassing three cavity resonators, l4 dimensioned to provide a resonance at a first output signal, designated f,. The output is coupled by means of a conductive antenna 74 having a leg secured to one of the vane elements. Antenna 74 extends within a common dielectric dome member 76 which is secured to pole piece member 42 and extends from the side of the anode member opposite to the cathode lead and support assembly. The dome member provides a means for the evacuation of the magnetron to a reduced atmosphere and the device is then sealed off by well-known techniques with a point of seal indicated as at 78.

The remaining normally strapped vane elements form a second slow wave circuit sector 80 resonant at a frequency f To adjust this circuit to the second desired frequency the circuit parameters are varied by such means as the thickening of the walls 12a to vary the dimension of the cavity resonators 14. The second frequency is coupled by means of an antenna 82 secured to one of the vane elements and extending into dome member 76. It will be noted that the resonant sectors are tuned to separate frequencies and simulta neously generate signal outputs utilizing a common cathode. In exemplary embodiments to be hereinafter described the separate frequencies were separated by approximately MHz with the pi-mode oscillation preserved for each independent frequencies. It is possible to have more than two separate resonator circuits separated by an isolated drift region and the conventional magnetron teachings with relation to stability of operation and the other tube parameters will dictate the range of frequencies possible with the new structure.

Alternative embodiments for the varying of the circuit parameters of the active cavity resonator sectors to determine the separate independent frequencies will now be discussed with reference being directed to FIG. 4. In this embodiment the magnetron anode circuit comprises an anode cylindrical wall 12 enlarged as at 12a and one of sector active cavity resonators is partially indicated and designated by the numeral 80. Up to this point all the elements are substantially similar to the previously described circuit component. The isolated drift region is now provided by a solid conductive member 84 intermediately disposed between the cavity resonator sectors. Conductive member 84 is secured to the wall of the anode member 12.

In FIG. 5 another method of varying the cavity resonator circuit parameters is shown and all similar components to those previously described have been similarly numbered. In lieu of the widening of the anode member walls in the region designated by the numeral 12a a conductive rod 86 can be disposed in the rear portion of one of the cavity resonators 14. In some instances more than one rod may be required to secure the desired circuit values.

In FIG. 6 the waveform trace is shown of an actual embodiment of a multisignal magnetron operated at a voltage of 3.6 kilovolts and a current of 540 microamperes (peak). The tube was operated under a pulsed condition with a pulse width of 34 microseconds and a duty cycle of 0.0 l5l. The power output was approximately 1,025 watts total (peak) with two simultaneous outputs indicated by the

peaks

88 and 90 for frequenciesf of 2,450 MHz and 2,550 MHz forfi The amplitude scale in the graph is ldb per centimeter and the dispersion approximately 25 MHz per centimeter. A bandwidth of approximately 100 MHZ is, therefore, available for coupling to any desired load.

While the interrupted strapped technique for the variation anode slow wave circuit parameters has been illustrated, other techniques include a plurality of stacked isolated reentrant anode slow wave circuits tuned to separate frequencies and employing a common cathode and common output. Another means for achieving the multisignal output would include variations of the interaction space parameters by variations of the radial depth of the cathode emitter, as well as tapering of the pitch of the end of the anode vane elements. The synchronous motion is thereby varied between the electrons and the waves on the slow wave structure at the various sectors with the anode-to cathode potentials being maintained at a constant value. The invention may also be practiced with continuous wave as well as pulsed operating condition. Since numerous variations, modifications and alterations may be practiced the foregoing detailed description of illustrative embodiments is intended to be interpreted broadly.

We claim:

1. A multisignal microwave magnetron comprising:

a cathode member;

an anode member having a plurality of conductive elements defining therebetween a plurality of cavity resonators circumferentially disposed around said cathode member;

the free ends of said anode elements defining with said cathode member an interaction region; means for producing crossed electric and magnetic fields within said interaction region;

means for simultaneously generating independent resonant frequency signals comprising interconnecting said anode elements in isolated active resonator sectors having predetermined circuit parameters separated by inactive drift regions; and

means for coupling said signals from each of said sec tors.

2. The magnetron according to claim 1 wherein said anode elements are alternately connected by conductive strap members with said. inactive drift regions defined by severing said members at predetermined points.

3. The magnetron according to claim 1 wherein said signal coupling means comprise a conductive antenna probe member secured to an anode element in each sector.

4. The magnetron according to claim 3 wherein the free end of each of said antenna probe members are disposed within a unitary dielectric dome member.

5. The magnetron according to claim 1 wherein said inactive drift regions comprise a spaced solid conductive member having athickness substantially greater than the active anode element.

6. A magnetron anode comprising:

a cylindrical conductive member having a plurality of radially extending conductive elements defining resonant slow wave circuits having predetermined frequency generating parameters;

said elements being interconnected to form plural isolated active resonant sectors tuned to independent resonant frequencies and separated by inactive drift regions.

7. A magnetron anode according to claim 6 wherein said elements comprise conductive vane members.

8. A magnetron anode according to claim 7 wherein said vane members in each active sector are alternatively connected by conductive strap members.

9. A magnetron anode according to claim 8 wherein said inactive drift regions comprise adjacent vane members joined together by conductive strap members. i

10. A magnetron anode according to claim 6 wherein said cylindrical conductive member is thicker in one active resonant sector relative to a second sector to vary the resonant circuit parameters.

a I UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3 92 ,3 6 Dated February 12, 1974 lnventofls) William A. Smith and John R; Butler It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column l,' line 41, chan ge"'staps" to -straps-- Column 1, line 47 change "a desired single" to -the operating Column 1, line 58, change "with" to -within-&- I

Column 2, line 7 change "radio" to "radar- Column 2 line 40, change "radical" to --radial- Column 3, line 29, change "l4" to--'-24-- Column 3, line; 47, change "buckle" to -buckin g Signed and sealed this 9th day of July 197A.

(SEAL) Attest: I

MCCOY M. GIBSON, JR. 1 c. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PC4050 (10-69) USCOMM-DC wave-ps9 U.S. GOVERNMENT PRINT NG OFFICI "I! 0-J6l-33A

Claims

1. A multisignal microwave magnetron comprising: a cathode member; an anode member having a plurality of conductive elements defining therebetween a plurality of cavity resonators circumferentially disposed around said cathode member; the free ends of said anode elements defining with said cathode member an interaction region; means for producing crossed electric and magnetic fields within said interaction region; means for simultaneously generating independent resonant frequency signals comprising interconnecting said anode elements in isolated active resonator sectors having predetermined circuit parameters separated by inactive drift regions; and means for coupling said signals from each of said sectors.

2. The magnetron according to claim 1 wherein said anode elements are alternately connected by conductive strap members with said inactive drift regions defined by severing said members at predetermined points.

5. The magnetron according to claim 1 wherein said inactive drift regions comprise a spaced solid conductive member having a thickness substantially greater than the active anode element.

6. A magnetron anode comprising: a cylindrical conductive member having a plurality of radially extending conductive elements defining resonant slow wave circuits having predetermined frequency generating parameters; said elements being interconnected to form plural isolated active resonant sectors tuned to independent resonant frequencies and separated by inactive drift regions.

9. A magnetron anode according to claim 8 wherein said inactive drift regions comprise adjacent vane members joined together by conductive strap members.