US2422465A

US2422465A - High-frequency magnetrons

Info

Publication number: US2422465A
Application number: US474426A
Authority: US
Inventors: Ralph J Bondley
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1943-02-02
Filing date: 1943-02-02
Publication date: 1947-06-17
Anticipated expiration: 1964-06-17
Also published as: FR954569A

Description

June 1947- R. J. BONDLEY HIGH FREQUENCY MAGNETRON.

Filed Feb. 2, 1943 Ihventor Ralph J. Bondleg,

Fig.5.

bu His Attorney.

Patented June 17, 1947 Ralph J. Bondley,

Scotia, N. Y., assignor to Gen- *eral Electric Company, a corporation of New ork Application February 2, 1943, Serial No. 474,426

4 Claims. (01. 250-275) My invention relates to high frequency electric discharge devices and more particularly to ultra high frequency magnetrons of the space resonant type. My invention is in the nature of an improvement over the tuning arrangement described and claimed in copending application Serial No. 465,439, of Kenneth C. De Walt, filed November 13, 1942, and this invention.

Heretofore in the design and construction of ultra high frequency magnetrons, difiiculty has been encountered in the provision of suitable tuning means therefor. One of the disadvantages of the prior art tuning arrangements for ultra high frequency magnetrons has been the nonlinearity and the extreme sensitiveness of the frequency controlling means with respect to the operating frequency of the device. Stated in other words, the prior art magnetrons of the tunable type have been diflicult to control or ad- Just by virtue of the fact that the tuning means have caused within certain regions of operation an excessive change in frequency, and within still other ranges of operation or frequency control have entailed very slight changes in frequency upon operation of the automatic or manual frequency controlling means.

In accordance with the teachings of my invention described hereinafter, I provide new and improved frequency controlling means for magnetrons which obviate the above described disadvantages of the prior art arrangements.

- It is an object of my invention to provide new and improved ultra high frequency magnetrons.

It is another object of my invention to provide new and improved ultra high frequency magnetrons of the space resonant type.

- It is a further object of my invention to provide new and improved ultra high frequency magnetrons-of tunable character wherein a linear relationship is obtained between the operating frequency of the magnetron and the frequency controlling means or tuning means.

It is a still further object of my invention to provide new and improved frequency controlling structure for space resonant magnetrons.

Briefly stated, in the illustrated embodiments of my invention, I provide new and improved tuning means or frequency controlling means for ultra high frequency magnetrons of the space resonant type wherein a positionable member or members are associated with the anode structure defining the space resonant cavities, and wherein a linear relationship is obtained between the opcrating frequency of the magnetron and the poassigned to the assignee of effect the desired tuning operation.

space resonant sition of the tuning member or members. In the particular form of magnetron with respect to which my invention is described, I provide tun ing members which may be either of conductive material or of dielectric material and which extend into openings in the anode structure to The tuning members are inserted in the anode structure in positions or openings within which the ultra high frequency electric and magnetic fields of the various space resonant cavities are present or associated.

In one embodiment of my invention a conductive or metallic annular ring extends into an annular recess in one face of the anode structure, and the position of the ring within the structure determines the natural frequency of the space resonant cavities and consequently determines the operating frequency of the device.

In another modification of my invention, the tuning means comprises a plurality of dielectric tuning stubs or cavities and thereby control the natural frequency of the cavities and the operating frequency of the device.

7 For a better understanding of my invention, reference may be had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims. Fig. 1 diagrammatically illustrates an embodiment of my invention as applied to an ultra high frequency magnetron wherein the magnetic excitation therefor is provided by a pair of longitudinally spaced permanently magnetized pole pieces, and Fig. 2 represents a cross sectional view of the anode structure including the coupling means provided for the space resonant cavities. Fig. 3 represents a further embodiment of my invention wherein the tuning means comprises a plurality of dielectric tuning members which extend into the space resonant regions and are supported by a ring construction, the details of which are shown in Figs. 4 and 5.

Referring now to Fig. 1 of the accompanying drawing, Ihave there illustrated my invention as applied to an ultra high frequency magnetron of the space resonant type. certain general features of which are broadly disclosed and claimed in copending patent application, Serial No. 447,903 of Elmer D. McArthur, filed June 22, 1942, and which is assigned to the assignee of the present application.

The magnetron shown in Fig. 1 comprises a lateral wall structure provided by a single metal tube I consisting of ferromagnetic material such members which extend into the ically sealed to the or electrode sections of the container are closed by flanged members weldedor otherwise hermetinner surface of tube I. -Within the container and approximately at its central portion there is provided an anode structure 4 which is shown in plan view in Fig. 2*. The anode structure 4 is preferably constructed 2 and 3 which are of a conductive non-magnetic material; such as copper, and is provided with an enlarged central opening which surrounds a cathode structure to and which comprises an conductor-01a concentric transmission line 23 comprising an inner conductor 2i and an outer tubular conductor 22.

As stated above, the anode structure 4 preferably consists of copper and is supported, as

' shown in Fig. 1, by being brazed to the inner wall be described presently. Circumferentiall'y arranged or positioned 5 there is provided a number of space resonant regions or cavities which may take the'form of cylindrical openings 6-l3, inclusive, each of which is in communication with the enlarged central opening 5 through a radially extending slot 14. Slots l4 define therebetween a plurality of electrode or anode sections.

In order to receive a tuning member, I provide in one surface, that is the bottom surface, of anode structure 4 an annular channel or groove l5. member or ring l6, preferably constructed of non-magnetic material such as copper or silver, and which proj ects into groove l5 and is in spaced relation with respect to the walls thereof. Groove l5 may be located at a number ofv positions with respect to openings 6-l3 and their associated slots l4, and the relative positions illustrated in Fig. 2 are merely exemplary of one way in which these elements of the anode structure may be arranged. I have found that effective tuning or control of the operating frequency is obtained by locating the annular groove l5 within the vicinity of the junctures of cylindrical openings 6-I3 and the slots I4.

As a means for coupling the various space resonant cavities defined by openings 6-I3 and .the associated slots I4, I provide a plurality of cou pling conductors l1 and II! which may be arranged in accordance with the patterns disclosed and claimed in my copending application, Serial No. 462,123, filed October 15, 1942, and which is assigned to the assignee of the present application.

Referring more particularly to the coupling conductors l1 and I8, these conductors are preferably arranged so that alternate metallic parts between slots M are electriaround the central opening of tube I. 'A relatively large circumferential channel 23 in the anode'structure serves to reduce the overall weight.

Within the enlarged central opening 5 of the anode structure 4 there is provided a cathode of the indirectly heated thermionic type a sleeve 24 having on the outside surface thereof a suitable electron emissive material such as barium oxide. Within the cathode sleeve 24 there is provided a cathode heating element 25, the upper terminal of which is connected to an inner conductor of a concentric line to be described presently, and the lower terminal of which is electrically connected to the sleeve 24.

Forthe purpose of providing a magnetic field to permit the apparatus to of sumcient intensity function in its intended manner, there is provided within the tube la pair of

magnetic pole pieces

26 and 21 which maybe permanently magnetized and which, of course, respectively provide north and south poles, or vice versa'.

Where the

magnetic pole pieces

26 and 21 are permanently magnetized, these members should be constructed of a magnetizable material having a high coercive force and a high energy factor. One of the materials which may be used in this connection is that known as Alnico meaning a particular class of alloys of aluminum, nickel and cobalt.

In order to obtain a low reluctance connection between the bases of the

pole pieces

26 and 21, 1 these pole pieces may be respectively seated upon relatively thick disk-like members 28 and.29 consisting of ferromagnetic material such as steel. For the purpose of securing the pole pieces rigidly onflxedly to these base members, use may be made of clamping rings'3il and 3l which are slipped over the pole pieces and; welded to the

members

28 and 29.

cally connected; that is, conductors i'l may be I considered as connecting alternate electrode sections and conductors l8 may be considered as connecting the intervening or intermediate electrode sections. This type of connection is obtained by constructing conductors i1 and iii .to span and to be physically separated from alternate electrode sections. For example, one conductor ll spans the electrode section between-m 'slots i4 associated with cylindrical openings 6 and l, and the adjacent conductor l8 spans the associated with cylindrical tends into one of the cavities, such as opening 8,

Accuratespaeing of

pole pieces

26 and 21 with respect to the anode structure 4 may be obtained by the useof.

spacing rings

32 and 33 which en-' gage the upper and bottom surfaces of the anode structure 4, and are in engagement with apertured

disks

34 and 35 abutting appropriately golrmed shoulders on magnetic pole pieces 26 and Magnetic pole pieces 26 and Time provided with longitudinally extending

channels

36, and 31, respectively, the former of which is employed to receive structure for supporting the cathode in spaced relation with respect to' anode structure 4 and fo r supplying cathode heating current thereto. For example, one type of construction which may be employed for this purpose is'that disclosed and claimed in my copending patent application, Serial No. 465,424,"flled' November 13,

1942, and which is assigned to the assignee of the present'application. This supporting structure may comprise a concentric transmission line including an outer conductor 38 and an inner conductor 39, the former of which is electrically connected to a supporting collar 40 which engages the cathode sleeve 24 and the latter of which is connected to the upper terminal of the cathode heating element 25, extending through the collar 40 and insulated therefrom by means of a vitreous "insulator 4|. Conductor 39 may extend through extension of an inner comprising the cylinder 24 and serve as a support for a shielding disk 42 which is in spaced relation with the pole face of pole piece 21 and the bottom surface of the anode structure.

The inner conductor 39 and the outer conductor 38 may be maintained in spaced relation with each other by means of a plurality of longitudinally spaced insulators 43. The entire concentric line arrangement may be supported in a desired central position in channel 36, and maintained in the proper longitudinal alinement by means of an insulatofr u which closely engages the inner surface 9 channel 36 and the outer surface of tubular conductor 38.

At the upper end of channel 36, the

conductors

38 and 39 are connected to externally accessible terminals 45 and 46, the latter of which are hermetically sealed by means of a suitable vitreous seal 41 which, in turn, is sealed to a flanged collar 48 welded to the upper surface of member 2.

The position of the ring tuning member 16 previously described in connection with Fig. 2 is more fully appreciated by referring to the longitudinal cross sectional view of, Fig. 1 wherein it is seen that the member or ring [6 extends into the recess .or annular groove l provided in the anode structure 4. Tuning ring I6 is provided with a flanged part l6a. Magnetic pole piece 21 is provided in its pole face with a transverse slot 49 adapted to receive and permit ready movement therein of a transverse supporting rod 50 which is attached to flange l6a of the tuning ring l6.

Control of the position of the transverse rod 50 and hence the longitudinal position of the tuning ring I6 is obtained by means of a longitudinal actuating rod 5| which is located in channel 31 and which is provided with an externally accessible actuating means such as a thumb-nut 52. The actuating means for the tuning structure may include a calibration scale (not shown) for indicating the position of the tuning ring l6 or for indicating the operating frequency of the device established by the position of that ring. Adjusting means for rod 5| includes an hermetic seal which may comprise a deformable metallic bellows 53 which is not only sealed to the lower surface of end member 3 but is also sealed to rod 5|. A metallic cap 54 surrounds the sealing bellows 53 and serves as a support for the lower extremity of rod 5|, and as a means for exerting variable pressures against the end of bellows 53 through rod 5 I and washer 53'.

The coupling conductors I! and I8 may be arranged to lie within a recess 55 provided in the bottom surface of the anode structure 4 as shown in Fig. 1. If desired, a similar system or array of coupling elements may be positioned in a recess 56 in the top surface of the anode structure 4.

In the operation of an electric discharge device of the above described nature, it may be considered that the energization or excitation of the various space resonant cavities comprising the cylindrical openings 6-l3 and the associated slots I4 is obtained by utilization of the motion of the electrons constituting the space charge which is effected or established between the outer surface of cathode sleeve 24 and the surfaces of the electrode sections between the slots l4. By virtue of the application of a unidirectional potential between the anode structure and the cathode, and the magnetic field which is provided by

pole pieces

26 and 21, the electrons constituting the space charge will be given a helical or spiral motion undergoing oscillations or gyrations to excite the various space resonant cavities at the desired frequencies. Electromagnetic energy is derived from the cavities by means of loop I 9 and concentric transmission line and is supplied to an external utilization circuit.

The control of the natural frequencies of the space resonant cavities and hence the control of the operating frequency of the device is, obtained by the longitudinal position of the tuning ring I6. As the ring I6 is inserted greater distances into annular groove I5, the operating frequency of the device is decreased. This feature of operation may be considered as occurring due to the increase of the capacitance effect of the tuning ring as a greater effective surface thereof is positioned in annular groove I5. .Of course, in a system of this nature wherein both magnetic and electric fields are present, the net effect of such a tuning ring cannot properly be described as being solely electric or solely magnetic. However,

l I have found that effective linear control of the operating frequency of the device is obtained by positioning the ring l6 longitudinally, and that the frequency decreases as the ring [6 is inserted greater distances in groove I6 and is increased as it is moved out of the groove.

Another modification of my invention is shown in Fig. 3 which is a partial cross sectional view of an electric discharge device built in accordance with my invention and many of the elements therein correspond to elements shown in Fig. 1, corresponding elements being assigned like reference numerals. In this modificationof my invention, I provide a plurality of dielectric tuning members, only two of which, 51 and 58, are shown in Fig. 3, and which are preferably constructed of a low loss dielectric material such as quartz. These tuning members are spaced annularly or circumferentially and extend into the cylindrical openings 6-l3 of the space resonant cavities. Transverse rod 50 supports an annular member or ring 59 provided with circumferentially spaced apertures 60 adapted to receive restricted ends of the dielectric tuning members. A better understanding of the arrangement of the dielectric tuning members may be obtained by referring to Fig. 4 which is a plan view showing the associated anode structure, ring 59 and the manner in which the tuning members are held in position on the ring.

A preferable form of the tuning members is illustrated in Fig. 5 wherein each member is shown as being provided with a shoulder 6| which serves to seat the member on the upper surface of ring 59, and the restricted or necked portion of the tuning member is provided with an annular recess 62 which is adapted to receive retaining and supporting means such as a spring clip 63 attached to ring 59. The spring clip meansmay be arranged as shown in Fig. 5 wherein a single ring serves to engage a pair of adjacent dielectric tuning members and a plurality of such spring means may be employed as shown in Fig. 4.

By virtue of the tapered relationship of the dielectric tuning stubs or members and the resilient character of the spring clip means 52, the members may be readily inserted through the apertures 60 and will upon insertion deflect the spring means 63 sufi'iciently to permit the proper seating of the tunin members on the upper surface of the ring 59, whereupon the ends of spring means 63 will enter the annular recesses 62.

I have found that one of the important advantages of magnetrons built in accordance with my invention is the substantially linear frequency change withrespect to the position of the tuning elements or the distances the tuning elements are moved; Furthermore, I have found that the tuning or frequency control is highly effective on completely coupled or strapped anode structures. The tuning or frequency control of ultra high frequency magnetrons built in accordance with my invention is not critical; that is, a reasonable amount of mechanical motion produces a useful frequency change. Lastly, the above described types of frequency control are readily applicable to'those arrangements where it is desired to provide, externally accessible means for controlling the frequency determining means.

While I have shown and described my invention as applied to'an electric discharge device of the ultra high frequency type embodying various elements of particular configuration, it will be obvious to those skilled in the art that changes and modifications may be made without depart-- ing from myinvention, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim asnew and desire to secure by Letters Patent of the United States is:

1. An ultra high frequency electric discharge device of the magnetron type comprising a plurality of cooperating electrodes-including a cathode and an'annular anode structure having a central opening through which'said cathode extends and providing a plurality of cavity resonators, a pair of magnetic pole pieces longitudinally displaced from said anode structure and each having therein a longitudinal channel, means mounted in the channel of one pole piece supporting said cathode and constituting a heating current lead, an adjustable tuning member extending into said anode structure, means defining a transverse slot in the pole face of the other pole piece, a transverse rod supporting said tuning member and positioned in the transverse slot in the face of said other pole piece, and means supporting said transverse rod and said tuning member comprising a longitudinal rod located within the channel of said other pole piece.

2. An ultra high frequency electric discharge device of the magnetron type comprising a plurality of cooperating electrodes including a cathode and an annular anode structure having a central opening through which said cathode extends and providing a plurality of cavity resonators, a pair of magnetic pole pieces longitudinally displaced from said anode structure and each having therein a longitudinal channel, means mounted in the channel of one pole piece supporting said cathodeand constituting a heating current lead, an adjustable tuning member extending into saidanode structure, means defining; a transverse slot in the pole face of the other pole piece, means supporting said tuning member comprising a rod located in the slot of the other pole piece, and externally accessible control means positioning said rod and said member.

3. An ultra high frequency electric discharge device of the magnetron type comprising a plurality of cooperating electrodes including a cath- 4 ode and an annular anode structure having a central opening through which said cathode extends providing a plurality of cavity resonators. a pair of magnetic pole pieces longitudinally displaced from said anode structure and each havin therein a longitudinal channel, means mounted in the channel of one pole piece supporting said cathode and constituting a heating current lead, means for controlling operating frequency of said device comprising a plurality of dielectric tuning members which extend into each of said cavity resonators, a member supporting and positioning said dielectric tuning members, means adjustably supporting and positioning said member and said tuning members comprising a longitudinal rod in the channel of the other pole piece, and externally accessible actuating means controlling the position of said rod.

4. An electric discharge device of the magnetron type including a plurality of cooperating electrodes including an anode structure having a plurality of circumferentially spaced anode sections extending radially inwardly and terminating short of the center of said structure and defining a central opening in said structure, said sections also defining between said sections a plurality of circumferentially disposed cavity resonators communicating with said opening, a generally annular channel having substantially depth formed in said anode structure near the inner ends of said sections, a cylindrical tuning member having substantial length extending a variable distance lengthwise into said channel whereby a substantially variable portion of the surface of said tuning member is juxtaposed to a corresponding portion of the surface of said channel, and means attached to said tuning member for moving said tuning member variable distances into said channel whereby the tuning effect of said tuning member may be varied in generally linear relation to the distance which said member extends into said channel.

RALPH J. BONDLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,288,812 Linder July '7, 1942 2,233,482 Linder Mar. 4, 1941 2,167,201 Dallenbach July 25, 1939 2,115,521 Fritz, et al Apr. 26, 1938 2,163,589 Dallenbach June 27, 1939 2,163,147 Samuel June 20, 1939 2,348,986 Linder May 16, 1944 2,408,234 Spencer Sept. 24, 1946 2,408,235 Spencer Sept. 24, 1946 2,408,355 Turner Sept. 24, 1946 FOREIGN PATENTS Number Country Date 509,102 Great Britain July 11, 1939 215,600 Switzerland Oct. 16, 1941