US2444418A - High-frequency electronic device - Google Patents

Description

y 1948- R. J. BONDLEY HIGH-FREQUENCY ELECTRONIC DEVICE Filed Oct. 15, 1942 .68 6.962 3 64 65 as 67 68 as Inventor":

Ralph \lBonclleg,

HisAttorneg.

Patented July 6, 1948 7 2,444,418: HIGH-FREQUENCY ELECTRONIC DEVICE Ralph J Bondley, Scotia, N. Y., assignor to General Electric Company, a corporation of New York Application October 15, 1942, Serial No. 462,123

The present invention relates to improvements in high-frequency electronic devices and particularly to devices of this character of the magnetron type.

High-frequency electronic devices employing a plurality of resonant cavities or slots have been employed as amplifiers and oscillation generators. One type of such device employed extensively as a high-frequency generator includes an anode structure comprising a circular array of anode elements coupled by resonant cavities and grouped around a common cathode which provide-s a source of electrons in the interelectrode space. As is well known, the functioning of such a device as a high-frequency oscillator depends upon the action of suitably directed magnetic and electric fields on the electrons emitted from the cathode.

In general, the frequency of these devices may be increased by increasing the number of anodes employed. However, the transfer of energy to the output circuit from the cavities remote from the output connections has been limited and the overall efiiciency therefor rather low. Also the number of modes or natural frequencies of operation increases with the number of anodes and the tendencyof these devices to change sporadically from one mode of operation to another has been a detrimental characteristic. Attempts to improve the efficiency and stability of operation of these devices have been made by making conductive connections between certain anode sections or poles on both the upper and lower faces of the anode structure.

An object of my invention is to provide an improved electrode structure for high-frequency apparatus to increase the efficiency of the apparatus as well as to improve the stability of operation.

It is another object of my invention to provide an improved electrode structure for high-frequency apparatus particularly of the magnetron type which is provided with means for readily adjusting the natural frequency of the electrode structure.

In accordance with the illustrated embodiment of my invention, I provide a high-frequency generator of the magnetron type having an anode structure including a plurality of anode sections coupled by resonant cavities and provided with an improved pattern of conductive connections between the different anode sections. As illustrated, the conductive connections are similar in shape to staples and are dimensioned to span an anode section and the two gaps which define the 13 Claims. (Cl. 250-275) spanned section.

On one face of the anode structure, the connections are complete; that is, alternate sections are connected around the array until every gap is spanned by two conductors. On the other face of the anode structure, the system of connections is incomplete; that is, some of the gaps are not spanned. In the preferred pattern illustrated, two adjacent conductors are omitted so that one gap is not spanned at all and the two adjacent gaps are each spanned by only one conductor. This arrangement has proved very effective in increasing the efficiency of the oscillator as well as to separate the modes of operation and improve the stability of operation. While the omission of only two conductors on one face of the anode structure has given the most improvement in operation, marked improvement in operation as compared with known arrangements has been observed when more than two adjacent conducting straps have been omitted.

My invention will be better understood by reference to the following description taken in connectionwith the accompanying drawing, and its scope will be pointed out in the appended claims.- In the drawing, Fig. l is aver-tical section of a magnetron device suitably embodying the present invention, Figs. 2 and 3 are top and bottom views, respectively, of the anode structure of the device shown in Fig. 1 and illustrating schematically the pattern of conductive connections employed for interconnecting the anode sections, andF'ig. 4 is a view showing a development of the anode surface opposing the cathode and showing the arrangement of the conductive connections be tween the anode sections.

In Fig. 1, I have shown a magnetron device of a type to which my invention maybe applied to advantage. The device is fully described and certain features thereof are claimed in the copending application of Elmer D. McArthur, Serial No. 447,903, filed June22, 1942 now Patent No. 2,412,824, and assigned to the same assignee as the present invention. Referring now to the drawing, there is shown an elongated cylindrical container, the lateral wall structure of which is provided by a single metal tube Ill consisting of ferro-magnetic material, such as cold rolled steel or the like. The ends of the container are closed by flanged members H and I2 which are welded or otherwise hermetically joined to the inner surface of the part ID. The outer surface of the container is provided with a, series of circumferentially extending fins l3 which are adapted to serve as heat-dissipating elements, and a somewhat larger circular element l4 provided near the upper end. of the container acts as a mountflangc for the device as a whole.

Within the container and approximately at its central region, there i provided an anode struc ture 15 comprising a circular member which has a relatively large central opening l6 and a series of smaller openings l'l arranged symmetrically about the central opening. The central opening is joined to the openings IT by means of radially extending slots l8 which divide the wall of the anode structure surrounding the opening l6 into anode sections designated by the numerals iii to 26, inclusive. The structure l5, which preferably consists of copper, is supported by being brazed to the interior wall surface of the part In. To facilitate the brazing operation, small channels 2'! are cut in the outer periphery of the structure and these are used to receive rings of brazing material applied before the anode structure is inserted within the container. A relatively large circumferentia1ly extending channel 28 serves to reduce the overall weight of the structure.

Within the opening N of the anode structure, there is provided an indirectly heated cathode comprising a sleeve 29 of nickel or other suitable material having flanges 30 spun up at its extremities. This sleeve, which may be coated externally with a suitable activating material, such as barium oxide, contains a filamentary heater 3| by which it may be maintained at ah emissive temperature. i One end of the cathode sleeve is closed by a metal disk 32 while an apertured disk 32a partially closes its other extremity.

In the operation of the device, a space charge is assumed to lee-developed in the space between the'cathode sleeve 29 and the surrounding anode structure by the application of a suitable potential impressed between one of the cathode'lead-in wires 33, 34 and the container Hito which the anode structure is directly conductively connected. The electrons which compose this space charge are given a spiral or orbital motion by a magneticfield produced by means shortly to be described, and their resultant gyrations about the cathode produce-excitation of the anode structure at its resonant frequency. The functioning of the anode structure in the latter connection may be explained from one'point of view by considering that it is made up of a plurality of mutually coupled resonant units in each of which inductance is provided by the wall surface bounding one of the circular openings I1 and capacitance is provided by the opposing surface of one of the slots l8. Taking this viewpoint, it will be seen that the operating frequency is in a large measure determined by the dimensions of the openings l'l. As mentioned earlier in the specification, devices of the character thus far described have exhibited a tendency to change sporadically from one mode of operation to, another with a corresponding change in operating frequency. This tendency has been particularly marked when the devices are operated from a'source of pulsating voltage. Inaccordance with an important feature of the present invention, .the anode sections are conductively connected in a predetermined mannerto minimize or eliminate this undesirable tendency toward instability of operation and to increase the efficiency of the device. Before describing this system'of connections in detail, the remainder of the structural features of the device as a whole will be described.

For the purpose of providing a magnetic field of-sufiicient intensity to permit the apparatus to function in its intended fashion, there are pro vided within the container l0 tapered magnetic pole pieces 35 and 36 which are directed axially of the container and which extend in close proximity to the upper and lower surfaces of the anode structure l5. For present purposes, these pole pieces are assumed to be permanently magnetized in such a sense that the north pole of one faces the south pole of the other.

In order to assure the existence of a magnetic field of the required intensity, the pole pieces 35 and 36 should be constituted of a magnetizable substance 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.

If the pole pieces 35 and 38 are constituted of Alnico, which is considered to be a preferred material, they are normally prepared in cast form and have their critical surfaces finished by grinding. The ground-surfaces may include, for example, the end surfaces of both pole p ces a theperipheral surfaces indicated by the numerals 3? and 38, respectively. These latter surfaces, together with the end surfaces which adjoin them may advantageously be copper plated to reduce losses attributableto high-frequency circulating currents induced by the proximity of these surfaces'to the interelectrode spaces in which highfrequency waves are generated.

In order to provide a low reluctance connection between the base extremities of the respective pole pieces and the lateral Wall of the container, the pole pieces may be respectivly-seated upon relatively thick disk-like members 39and l l consisting of term-magnetic material, such as steel. For the purpose of securing the pole pieces fixedly to these basing members, use may be made of clamping rings M and. 42 slipped over the pole pieces and welded to the basing members. Each basing member is of such diameter as to fit snugly within the tubular container part H3 so as to provide a low reluctance connection with that part, and welded to one of the closure members ll, 52.

Accurate spacing of the pole pieces 3'5 and 36 with reference to the anode structure l5 may be obtained by the use of spacing rings 43 and 44 used in the manner indicated. As is shown in Fig. 1, each of these rings is interposed between one surface of the anode structure and the surface of an apertured disk 45, :36, each disk in turn being in abutment with an appropriately formed shoulder provided on the adjacent pole piece as indicated at M and 48. The spacing rings 43 and M may be welded in place before the pole pieces are inserted within the container.

With the pole pieces 35 and 35 arranged inside the container l0, it becomes convenient to use the pole pieces as a supporting means for the cathode structure 29. This maybe done, for example, by the use of a pair of insulating beads 49 and 5B which are respectively centered in axially extending openings ii! and 52 cut in the pole pieces. The lower bead 5B is provided with a central aperture adapted to receive a centering stud 53 projecting downwardly from the cathode end plate 32. The upper bead 39 has two separate openings through which the current supply wires 33 and 34 extend. These wires, which are held in spaced relation within the channel 5| by means of additional insulators 5 and 55, are joined at their extremities to relatively heavy lead-in wires 56 and 5?. These, in turn, are sealed into the container through a glass-to- I netal seal which comprises a body of glass 58 tions and soldering them in place.

fused to the extremity of a metal eyelet 59. This arrangement of the cathode supply leads has the particular advantage that it avoids any substantial couplingbetween the cathode supply circuit and the high-frequency fields generated in the interelectrode space, thus being aconsequence of the fact that both the supply leads extend axially with respect to the electrode structures and are fully shielded by the bodyfof the pole piece 35. The passage communicates with an exhaust tubulation 6|] which is sealed after the device is evacuated as illustrated at 6|.

In the operation of devices of the type described above, it has been observed that the preferred mode of operation occurs when alternate poles are at any instant of opposite polarity. The stability of operation in this mode is improved by conductively connecting alternatepoles on each face of the anode structure. Inaccordance with an important feature of the present invention, the poles ofthe anode structureare connected by an improved pattern of conducting elements which has provided stable operation in the desired mode and also'resulted in a marked increase in efficiency. As illustrated in Figs. 2, 3, and 4, these connections may be made by small copper wires having a shape similar to a staple and with the arm portions thereof spaced to span the alternate anode sections. The ends of the conductors may besecured to the ends of the anode sections by placing them in small openings inot shown) in the ends of the anode see- As illustrated in Figs; 2 and 4, conductors 62 to 69, inclusive, connect alternate anode sections at the upper end of the anode structure and conductors 62 to 6'! connect alternate anode sections on the lower end of the anode structure for a portion of the entire circumference. While the patterns or systems of connections on both upper and lower faces may be complete. that is, all alternate anode sections may be connected, it is preferable that the system of connections on one face be in complete. By reference to Fig. 4, particularly, it will be noted that the gaps are spanned by two conductors with the exception of three gaps on the lower face. One of these gaps is not spanned byany conductor on the lower face of the structure while the adjoining slot on each side is spanned by only one conductor. This interruption of the complete pattern of strapping by conducting elements bythe omission of two elements on one face of the anode structure has given a higher output efficiency than could be obtained from the same device with both the upper and lower patterns of conducting elements complete. The omission of more conducting elements immediately adjacent those'omitted in the illustrated embodiment caused a slight decrease in efliciency as compared with the illustrated embodiment. The eificiency under these conditions, however, was still considerably above the efficiency resulting from a complete pattern of conducting elements on both the upper and lower'faces of the anode structure.

It will be appreciated that the presence of. the conducting elements or straps will have the effect of modifying the wave length at which the anode cavities oscillate and, accordingly, this should be taken into consideration in machining the anode structure. The magnitude of the change resulting from the presence of the conducting elements depends upon the spacing of the wires from the anode sections, and this fact may be utilized to make an adjustment of the resonant frequency of the cavities. As described above, the conductive connections are made with loops of wire of good conducting material, such as copper, which are shaped similar to staples. It will be readily appreciated that these wires may be adjusted with respectto the face of the electrpde structure by bending to adjust the natural frequency of the electrode and thereby determine its wave length as well as to make adjustments of the resonant frequencies of the different cavities after they have been machined. In practice, gages may be provided which are slipped under the loops of the conductive connections to assist in making the adjustments.

When a device such as that illustrated in Fig. 1 is placed in operation, it is, of course, necessary to provide some means for abstracting a portion line.

of the energy developed in the interelectrode space. This may be done in one way by an arrangement which includes a coupling loop 'll'l'introduced through an opening H in the wall of the anode structure. The coupling loop in the arrangement shown has an extension in the form .of a wire 12 which constitutes the inner conductor of a coaxial transmission line having a tubular part 13 as its outer conductor. The tube 13 passes through the wall of the container cylinder l0 and may be exteriorly connected through a tapering enlargement M with a somewhat larger tubular part I5. In similar fashion, the wire 12 is merged into a larger conductor 16 through a tapered transition region Tl which is of such configuration as to avoid any substantial change in the characteristic impedance of the (The fulfillment of this latter condition requires the maintenance of a constant ratio between the diameters of the outer and inner conductors.) The conductors I5 and 16 may connect with an antenna or other agency for utilizing the high frequency energy developed by the apparatus, and their size is determined with this end in view. The vacuum tightness of the container is preserved by means of a bead of glass 18 which forms a seal between the conductor 16 and the surrounding tubular member 15. y

In the illustrated embodiment, the coupling loop 10 of the output circuit has been placed in the opening or cavity l1 diametrically opposite the gap 18 across which the conductors have been omitted on one face of the anode structure.

Placing the loop 18 in a cavity displaced ninety mechanical degrees with respect to the partially strapped cavity also operated satisfactorily with no appreciable change in efiiciency. Placing the output loop in the partially strapped slot, however, resulted in an appreciable decrease in efficiency,

While I have shown and described a particular embodimentof my invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my inventionin its broader aspects, 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.

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

1. An electrode structure comprising an even number of electrode sections mutually spaced apart about a closed figure and providin cavity resonators therebetween adapted to be excited at high frequency, said electrode sections having endsin opposite faces of said electrode structure, means conductively connecting all of the even numbered electrode sections together on one face r 1 of'zsaid electrode structure and means con'du'ctively :connecting all of the odd numbered electrode sections together on said 'one face, and a similar system of conducting connections connectring all of the alternate electrode sections together on the other face of said electrode structure.

'2. A structure fora magnetron-type discharge device including a first electrode comprising a circular array of electrode sections mutually spaced apart and defining cavity resonators there- -between, a second electrode spaced from said array of electrode sections and providing a source :of electrons in the interelectrode space, magnetic means adjacent said electrodes for producing a magnetic field in said interelectrode space to control the movement of .said electrons to cause excitation of said first electrode, and a system of conductive connections on each face of said first electrode, said faces being spaced apart along the length of said second electrode, each system of connections including connections between all alternate electrode sections.

3. A structure for a magnetron-type discharge .device including an electrode having an opening therein and having a plurality of cavity resonators about said opening and dividing said electrode into a plurality of electrode sections, a second electrode in said opening and providing a source of electrons in the interelectrode space, magnetic means in proximity to said electrode sections for controlling the movement of said electrons in said interelectrode space to produce high frequency excitation of said first electrode, and a system of conductive connections on each face of said first electrode, each system of connections including connections between all alternate electrode sections.

4. A structure for a magnetron-type discharge device including a first electrode having an opening therein and having a plurality of cavity resonators about said openin and dividing said electrode into a plurality of electrode sections, a second electrode mounted in said opening and providing a source of electrons in the interelectrode space, magnetic means in proximity to said electrode for controlling the movement of said electrons in said interelectrode space to produce high frequency excitation of said first electrode, and a system of conductive connections on each .face of said first electrode, one of said systems of connections including connections between all alternate electrode sections, the other of said systems having connections omitted in only one re- .gion thereof and being otherwise the same as said one system of connections.

5. A structure for a magnetron-type discharge device including a first electrode having anopening therein and having a plurality of cavity resonators about .said opening and dividing said electrode into a plurality of electrode sections, a second electrode positioned in said opening and providing a source of electrons in the interelectrode space, magnetic means in proximity to said electrode for controlling the movement of said electrons in said interelectrode space to produce high frequency excitation of said first electrode, and a system of conductive connections on each face of said first electrode, each system of connections including connections between all alternate electrode sections, the connections of each of said fsystems comprising conductors which are readily adjustable with respect to the surface of the first electrode to control the resonant frequency of said first electrode.

.16. Astructure for a magnetron-type discharge ing therein and having a plurality of spaced reson-ant cavities about said opening and dividing said electrode into a plurality of electrode sections, a second electrode positioned in said @opening and providing a :source of electrons in the interelectrode space, magnetic means in proximity to said first electrode for controlling the movement of said electrons in said interelectrode space to produce high frequency-excitation of said first electrode, and a system of conductive connections on each face of said first electrode, one of said systems of connections including connections between all alternate electrode sections, the other of said systems having connections omitted in only one region thereof and being otherwise the same as said one system of connections, the connections of each of said systems comprising conductors which are readily adjustable with respect to the surface of the first electrode to control the resonant frequency of said first electrode.

7. An electrode structure for a high frequency device comprising a plurality of electrode sections mutually spaced apart providing cavity resonators therebetween and adapted to be excited at high frequency, said sections having face portions for confining the space charge of the device and means conductively connecting predetermined electrode sections together in proximity to said face portions to separate the natural modes of oscillation of said structure and to stabilize the operation thereof when said electrode structure is excited for operation at a particular frequency, said means being adjustable with respect to the electrode structure to adjust the resonant frequency of the electrode structure.

'8. An electrode structure comprising a plurality of electrode sections mutually spaced apart providing cavity resonators therebetween and adapted to be excited at high frequency, and means conductively connecting predetermined electrode sections together to separate the natural modes of oscillation of said structure and to stabilize the operation thereof when said electrode structure is excited for operation at a particular frequency, said means comprising Wire-like loops which are readily bendable to adjust the spacing of said connections with respect to said structure and thereby adjust the natural frequency of said electrode structure.

9. A structure for a magnetron-type discharge device including a first electrode comprising a circular array of electrode sections which are mutually spaced apart providing a plurality of cavity resonators, a second electrode spaced from said array of electrode sections and providing a source of electrons in the interelectrode space, means in proximity to said first electrode for producing .a magnetic field parallel to the axis of said circular array to control the movement of said electrons and cause excitation of said first electrode at a particular frequency, a system of conductive connections connecting all alternate electrode sections on one face of said first electrode, and an incomplete system of conductive connections connecting alternate electrode sections on the other face of said electrode sections, said incomplete system having connections omitted at only one region thereof providing at least one electrode section in said region not connected by any conductive connections on said other face.

10. A structure for a magnetron-type discharge device including a first electrode comprising a circular array of electrode sections which are mutually spaced apart providing a plurality of cavity resonators, a second electrode spaced from said array of electrode sections and providing a source of electrons in the interelectrode space, means in proximity to said first electrode for producing a magnetic field parallel to the axis of said circular array to control the movement of said electrons and cause excitation of said first electrode at a particular frequency, a system of conductive connections connecting all alternate electrode sections on one face of said first electrode, an incomplete system of conductive connections connecting alternate electrode sections on the other face of said first electrode, said incomplete system having connections omitted at only one region thereof providing at least one electrode section in said region not connected by any conductive connections on said other face, and means located in one or the cavity resonators remote from said last-mentioned electrode section for extracting energy from said electrode structure.

11. A structure for a magnetron-type discharge device including a first electrode comprising a circular array of electrode sections mutually spaced apart and definin a plurality of cavity resonators, a second electrode spaced from said array of electrode sections and providing a source of electrons in the interelectrode space, means in proximity to said first electrode for producing a magnetic field to control the movement of said electrons to cause excitation of said first electrode at a particular frequency, a system of conductive connections connecting all alternate electrode sections on one face of said first electrode, and an incomplete system of conductive connections connecting alternate electrode sections on the other face of said electrode, said incomplete system having only adjacent connections omitted providing only one break therein.

12. A structure for a magnetron-type discharge device including an electrode structure comprising an array of generally parallel electrode sec tions which are mutually spaced apart providing cavity resonators between them, means for providing an electronic space charge in proximity to said electrode sections and in energy-exchanging relation with said resonators, means in proximity to said electrode structure for producing a magnetic field parallel to said electrode sections whereby the electrode structure may be set into high-frequency resonance as a consequence of the gyrations of the electrons composing said space charge, a system of conductive connections connecting all alternate electrode sections at one Number end of said structure, and an incomplete system of conductive connections connecting alternate electrode sections at the other end of said structure and having a plurality of adjacent connections omitted at only one region thereof leaving at least one electrode section unconnected with any other section at said other end of said structure.

13. A structure for a magnetron-type discharge device including a first electrode comprising an even number of electrode sections which are mutually spaced apart providing cavity resonators, a second electrode spaced from said first electrode and providing a source of electrons in the interelectrode space, means in proximity to said first electrode for producing a magnetic field substantially parallel to said electrode sections to control the movement of said electrons and thereby cause excitation of said first electrode at a particular frequency, means conductively connecting all of the even numbered electrode sections on one face of said first electrode, means conductively connecting all of the odd numbered electrode sections on one face thereof, means conductively connecting less than the total even numbered electrode sections on the other face thereof, and means conductively connecting less than the total number of odd electrode sections on th'e other face thereof, the unconnected odd and even electrode sections on said other face being adjacent providing only one break in the system of conductive connections on said other face.

RALPH J. BONDLEY.

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

UNITED STATES PATENTS Name Date Samuel Dec. 8, 1936 Dallenbach Aug. 30, 1938 Gutton et al. Feb. 14, 1939 Dallenbach et al. June 27, 1939 Dallenbach July 25, 1939 Fritz Jan. 16, 1940 Varian et a1 June 10, 1941 Linder May 16, 1944 Spencer Sept. 24, 1946 Biggs etal Oct. 8, 1946 FOREIGN PATENTS Country Date Great Britain Apr. 2, 1936 Number

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