US2973455A - Radio frequency apparatus - Google Patents

Description

Feb. 28, 1961 R. H. MARLOWE RADIO FREQUENCY APPARATUS Filed Jan. 25; 1960 FlG.l.

INVENTOR: RICHARD H. MARLOWE,

United States Patent "ice RADIO FREQUENCY APPARATUS Richard H. Marlowe, Clinton, N.Y., assignor to General Electric Company, a corporation of New York Filed Ian. 25, 1960, Ser. No. 4,341

4 Claims. (Cl. 31539) My invention relates to radio frequency apparatus and pertains more particularly to improved voltage tunable magnetron circuitry including a rcentrant resonator cavity.

The reentrant resonator cavity has heretofore been utilized extensively with klystron amplifiers and oscillators. Its use with voltage tunable magnetrons has, however, been limited because of diflicult-ies encountered in endeavoring to obtain broadband operation of thev mag-.

netrons with such a circuit. My invention contemplates the provision of a compact, efiicient voltage tunable magnetron circuit including a reentrant cavity and effective for serving as 'a variable frequency source operable in equipments requiring tunabili-ty over a substantially wide operating frequency range.

Accordingly, the primaryobject of my invention is to provide a new-and improved voltage tunable magnetron circuit including a reentrant resonator cavity. 7

Another object of my invention is to provide anew and. improved voltage tunable magnetron circuit which is etficient and adapted for operation over a substantially wide operating frequency range. Another object of my invention is to provide a new and improved voltage tunable magnetron circuit which is compact and relatively simple and inexpensive to manufacture.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of 'novelty which characterize my in vention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In carrying out the objects of my invention I provide a circuit including an interdigital voltage tunable magnetron having apair of spaced anode contact rings and a reentrant resonator cavity. The cavity has the opposed end walls thereof apertured for receiving opposed ends of the magnetron and for serving as coaxial electrical contacts adapted for making circumferential contact with the anode rings. Extending laterally from one side of the circuit is a. coaxial line. .The outer conductor of the coaxial line is secured to the cavity and the inner conductor includes a substantially J-shaped flattened inductive loop extending inwardly in the cavity and having the end portion thereof disposed between the anode rings with the turned back portion electrically contacting one of the anode rings. Insulative means in the cavity hold the inductive loop in desired inductive relation with the magnetron.

For a better understanding of my invention reference may be had to the accompanying drawing in which:

Figure 1 is a greatly enlarged sectionalized side elevational view of radio frequency apparatus incorporating an embodiment of my invention; and

Figure 2 is fragmentary plan view illustrating particular features of my invention.

Referring to Figure 1, there is illustrated therein a voltage tunable magnetron generally designated 1. The

- magnetron 1 can be of the type disclosed and claimed in copending US. application S.N. 723,926 of G. I. Grifiin,

2,973,455 Patented Feb.- 28, 1961 2 I r. et al. entitled Voltage Tunable Magnetron, filed March 25, 1958, now Patent No. 2,930,933, and assigned to the' same assignee as the present invention. Briefly, the mag netron 1 is constructed to include stacked alternate ceramic and metal elements. The ceramic elements generally include a plurality of cylindrical ceramic wall sec tions 2 and an apertured disc-like ceramic end cap 3. The metal members are suitably brazed to or between opposed surfaces of the ceramic elements to complete a hermetically sealed envelope and include a metal end cap 4 carrying a cylindrical non-emissive cathode 5 extending centrally in a cylindrical space defined by a plu rality of anode segments generally designated 6. The

anode segments 6 are arranged in a pair of interdigital sets, with each segment being carried by a washer-like anode contactring 7. -The rings 7 are sealed between a pair of ceramic cylinders -2 and are thus mutually insulated. A filamentary emitter 8 is suitably mounted on the ceramic end cap 3 with leads sealed therethrough and connected to a. pair of. button-like contact members 9 bonded to the outer surface of the ceramic end cap, A frusto-conical control electrode 10 is sealed between one of the ceramic insulators 2 and the ceramic end cap 3 and is positioned about the emitter 8. By means of a lead not shown and which extends also in a sealed manner through the ceramic end cap 3 an electrical connection is made between the control ring 10 and a third button-like contact member v11 bonded to the outer surface to the ceramic end cap.

T m netron i adapted fornremfinswh ax y aligned with a magnetic field provided, for example, by a magnet including opposed pole pieces designated N and S in the drawing. Additionally, the magnetron is adapted for operating with suitable direct current potenv tials on the various electrodes supplied through the metal end cap 4 and the contact buttons 9 and 11 in a manner not shown.

The radio frequency circuit of the apparatus illustrated includes the anode segments 6 and the contact rings 7. Additionally, this circuit includes as an essential part thereof a reentrant resonator cavity generally designated 12. The cavity 12, as seen in Figure 2, can be circular and can comprise a cup-like body having a cylindrical outer side wall 13, a reentrant bottom 14 which includes a cylindrical inner wall 15 and a transverse end wall 16. Additionally, the cavity includes a washer-like cover 17 held in place by a plurality of machine screws .18, for example.

The bottom 16 is centrally apertured for receiving one end of the magnetron 1 and for affording a coaxial contact surface adapted for making circumferential electrical contact with one of the anode rings 7. The cap 17 receives. the opposite. end of the magnetron and makes circumferential electrical contact with theother anode ring 7 through an annular retaining member 19 threaded in the cap in. amanner to. engage the other anode ring and hold the magnetron tightly in place in the cavity.

During operation of the magnetron strong magnetic fields are established between the anode rings 7 in the cavity 12, and provided for transmitting radio frequency energy out of the cavity 12 is a coaxial line 20. The line 20 includes tubular outer conductor 21 suitably mounted in the side wall 3 of the cavity and extending radially outwardly therefrom. The inner conductor 22 of the line 20 includes an end portion extending radially inwardly and shaped to define a substantially J-shaped inductive loop adapted for coupling energy from the cavity into the coaxial line.

The loop 23 is flattened such as to define a cross section which is substantially wider than the cross section of the portion of the inner conductor in the tubular portion 21. Additionally, the inductive loop 23 extends sutficiently inwardly to dispose the looped end portion between the anode contact rings of the magnetron. Still further, the extreme inner end portion 24 or the portion which turns back on the main portion of the flattened loop rests on and engages electrically the planar surface of one of the anode rings 7: The portion 24 is preferably of substantiallength and width to insure substantial areal contact between these members. Additionally, the lengthofi the J'- shaped portion and the substantial width thereof provides for maximum linking orinductive relation with the magnetic flux present in the cavity during operation of the magnetron. Electrically speaking, this arrangement af fords a verytight coupling between the load represented by the coaxial lineand-the magnetron I with-thedcsi'red efiect of lowering the Q of the circuit; With the Q K thus lowered the circuit is adapted for more eflicient operationover a substantially wide range ofoperating'frcquencies of the magnetron.

asses reentrantresonator-cavityhavingsaidmagnetronmounted said anode rings.

therein and including a cylindrical inner side wall, a radially spaced, relatively longer cylindrical outer side wall and longitudinally spaced apertured transverse end walls, said end walls including coaxial contact surfaces each making circumferential electricaLcontact with one of said anode rings, a coaxial line including outer and inner conductors, said outer conductor extending from the outer side wall of said cavity, and s aid innen conductor in, cluding an inductive loop portion disposedi'externally 'of said envelope of said magnetron and 'extending'in'wardly in said cavity: and between radiallyrprotmding. portions of 2. A combination according 'to'claim 1, wherein said inductive loop is substantially J-shaped and the turned I back end portion thereof engages and electrically contacts In order to hold the loop 23' in place in the desired position between the anode rings 7, I have provided an insulative support member 25. By way of example, the member 25 can be formed satisfactorily of Teflon. Additionally, and as seen in Figure 2, themember 25 is slightly wider than the flattened portion of the loop 23, thus to prevent rotation of the loop and'thereby insure support of the loop in the desired position shown in the drawing in which it extends parallel to the planes of said anode rings.

The member 25 includes a first portion 26 shaped to fit substantially tightly in the looped portion of the inductive loop and a second portion 27 corresponding in width generally to the distance between the outer and inner walls 13 and 15, respectively, of the cavity. Thus; the member 25, when positioned in the cavity inthe manner shown in Figure 1,, holds the-loop 23- in the desired position. Assisting in this function andinsuring contact between the Ioopend=24 and the anode-ring engaged'there by isa planar insulative member 28 having preferably the same general width as the member-28 iositioned between the loop and the cover 17 of the cavity. The member 28 can also be formed of Teflon and cooperates with the member 25 tohold the loop in the desired position shown wherein it makes electrical contact with one of the anode rings and is positioned in close relation to the ceramic wall member disposed" between the anode rings. If desired the loop can abut-the ceramic wall member between the anode rings; however, it is to be understood one of said anode rings of said magnetron.

3. In combination, an interdigital magnetron including an envelope having a pair of anode ringsv sealed in axially spaced relation in the wall of said envelope and separated by an insulative section of said wall, a reentrant resonator that such abutment is not essential to the desired operation of my circuit.

While I have shown and described a specific embo'dig ment of my invention I' do not desire my invention to be limited to the particular form shown and described, and I intend by the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by'ljetters Patent of the United States is:

1. In combination, an interdigital magnetron including an evacuated envelope having a longitudinally spaced pair of anode rings sealed through the wall of said envelope and separated by an insulated section of said wall, a

cavity having said magnetron motmted therein and including radially spaced inner and outer side walls and axially spaced opposed transverse end walls, said end walls being apertured and including, coaxial contactsurfaces each making circumferential electrical contact with one of said anodevrings, a coaxial line including outer and inner conductors, said outer conductor extending radially from the outer side wall of said cavity, said inner conductor including a flattened J-shaped inductive loop which is substantially wide relative to the portion of said inner conductor in said outer conductor, said inductive loop extending radially inwardly in saidcavity and with the inner end portion disposed externally of saidenvelope and between radially protruding portions of said anodein close relation to the wall portion of,jsaid'l envelope between said rings, and insulative means in' said cavity-holding said loop in position between saidanode ringsiwith therturned back end portion of said loop engaging and'fmalting;electricalcontact with one of said anode rings.

'4. The combination according to claim 3, wherein the flattened portion of said loop extends parallel to the planes of said anode rings and said insulative means comprises a first member engaging one side of said loop and has a portion fitted between said inner and outer walls of, said cavity and. another portion fitted inthe looped. portion of said inductive loop, said insulative means further includes a second member engaging the opposite sideoff said loop, and said first and second members are tightly fitted'in said cavity for holding said'lo'op in place and avoiding rotation thereof out of said parallel position.

References Cited in the file of this patent UNITED STATES. PATENTS.

' 2,578,569- McCarthy Dec. 11, :1 2,653,301 Moore etal Sept. 22, 1953 2,679,615 Bowie May 25; 1954

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