US3013180A - Magnetron device and system - Google Patents

Description

Dec.

P. H. PETERS, JR 3,013,180

MAGNETRON DEVICE AND SYSTEM Filed May 1, 1958 I V f O" k wa F lg 4.

In vemor His Attorney.

United States Patent Ofitice 3,013,180 Patented Dec. 12, 1961 3,013,180 MAGNETRON DEVICE AND SYSTEM Philip H. Peters, J12, Schenectady, N.Y., assignor to General Electric Company, a corporation of New York Filed May 1, 1953, Ser. No. 732,224 Claims. (Cl. 315-39) The present invention relates to improved magnetron devices and systems, and, particularly, to improvements in the control and stabilization of the operating frequency of such devices and systems.

Magnetron devices are widely used as a source of high frequency oscillations and the output is often supplied to a wave guide system coupled directly with the anode terminals of the device. As is well understood, the dimensions and configuration of the anode circuit and also the parameters of the guide directly associated with the anode circuit affect the operating frequency and stability of the operation at any particular frequency. I have found that in order to provide stable operation at the desired frequency it is often desirable to modify the electrical parameters of the device and system and that this may be accomplished to advantage by suitably locatedconducting strips or bars between the anode terminals external of the envelope and accordingly it is an important object of my invention to provide improved magnetron devices and systems with respect to stable op eration at a desired frequency.

While not limited thereto I have shown my invention,

in the illustrated embodiment, applied to a magnetron systern which is voltage turnable; that is the frequency of operation may be varied over a substantial range by varying the anode-cathode voltage. Both the operating frequency and the range over which tuning may be accomplished may be modified and determined by providing suitable conductive connections between the anode terminals. In particular, when the magnetron device is utilized in a rectangular cross section and with energy propagated in only one longitudinal direction from the device I have found that conductive connections between the anode terminals located on diametrically opposite sides of the magnetron envelope adjacent the side walls of the guide are effective to control the frequency range over which tuning is readily accomplished and that a conductive connection located on the longitudinal axis of the guide and behind the discharge device with respect to the direction of the propagation of output energy along the guide is particularly effective in establishing the center frequency of operation.

In the drawing, FIGURE 1 is an elevational view of an electric discharge device and wave guide system embodying my invention;

FIGURE 2 is an enlarged elevational view of a part of the system of FIGURE 1 and partially in section to show the operative relationship between the discharge device and the wave guide;

FIGURE 3 is a sectional view taken along the line 3-3 of FIGURE 2, and

FIGURE 4 is an elevational view of a discharge device illustrating a modified form of my invention.

As illustrated in FIGURE 1 of the drawing I have shown my invention embodied in a magnetron device and system including a wave guide having a tapered intermediate section 11 connecting the portion of uniform cross section 12 and a second portion 13 of uniform cross section but lesser height which may be considered the input section of the guide within which the magnetron discharge device 14 is supported. As is more readily apparent from the enlarged sectional view of FIGURE 2, the discharge device includes a generally cylindrical envelope made up of annular insulating members 15, 16, 17 and 18 Which'support terminal members 19, 20, 21, 22

and 23 and cooperate therewith to provide a vacuum tight envelope. Terminals 19 and 23 are generally disk-shaped and close the opposite ends of the envelope while the terminals 20, 21, and 22 are generally annular in shape. The anode terminals 21 and 22 are spaced apart a distance corresponding to the spacing between the opposite side walls of the reduced section of the wave guide 10 and, as illustrated, the tube is secured in position in the aperture provided in the side walls of the guide by means of a threaded ring 24.

- The anode circuit of the device is of the interdigital type and is made up of two sets of longitudinally extending anode segments 25 and 26 arranged in a cylindrical array in alternate relation with the segments 25 of one set connected with and supported from the upper anode terminal 21 and the sections 26 of the other set connected with the lower anode terminal 22. A source of electrons and a non-emitting cathode for defining with the cylindrical array of anode sections the interaction space are provided by the cathode structure supported from the opposite end terminals 19 and 23 of the device. As illustrated, the emitting portion of the cathode is in the form of a spiral conductor 27 having one end received in a recess provided in a boss 28 on the inner wall of the end terminal 19 and the other end supported by the section 29 of reduced cross section formed integrally with non-emitting cathode post 30 supported from the other end terminal 23. As is well understood by those skilled in the art the cathode spiral may be formed of a suitable refractory metal such as tungsten. The injection of electrons emitted from the cathode 27 into the interaction space defined by the anode segments 25 and 26 and the non-emitting cathode post 30 is accomplished under the control of a frustoconical control member terminating adjacent the upper end of the array of anode segments and supported at its larger end from the control grid terminal 2%. The end of the guide behind the device 14 is suitably closed to minimize the radiation high frequency energy. As illustrated, this closure or shield may be in the form of a small piece of tubing 32 which is longitudinally slotted to receive the end of the guide.

It is well understood by those skilled in the art that the system thus far described may be operated by impressing a suitable cathode heater voltage on the end terminals 19 and 23 to render the cathode spiral 27 emitting. Suitable control voltage is impressed on the frustoconical control electrode 34 to determine the number of the emitted electrons which find their way into the interaction space between the non-emitting cathode 30 and the array of anode segments 25, 26. A radial electric field is produced by a direct current voltage applied between the cathode terminal 19 or 23 and the array of anode segments and an axial magnetic field is provided by means of a suitable permanent magnet or electromagnet, the pole pieces of which are shown at 33 in FIG- URE 1. It is generally considered that the electrons constituting the space charge form in bunches and rotate in t the annular space between the cathode and the anode to interact with the high frequency fields generated across the adjacent anode sections and, in this way, to transfer energy from the electrons to the field and to sustain the oscillations of the anode structure.

As described in detail in US. Patent 2,774,039-Peters et al.dated December 11, 1956 it is possible to change the operating frequency of magnetron systems of the type herein described directly in accordance with the applied voltage between the anode and cathode circuit provided the space charge within the interaction space is suitably limited and the anode system is heavily loaded. The operating frequency and the bandwidth over which it may be tuned is also affected by the geometry of the tube itself and the associated circuit. In accordance with the present invention I have found that both the operating frequency and the bandwidth can be desirably controlled by providing suitable conductors extending between the anode terminals. As shown in FIGURES 2 and 3 three of these strips in the form of conductive coatings on the anode insulator may be provided. One of these strips 34 is located on the longitudinal axis of the guide, that is, directly behind the magnetron with respect to the direction of propagation and energy in the guide. The other two are located at opposite ends of a diameter of the device which is substantially perpendicular with respect to the longitudinal axis of the guide. These conducting strips may to advantage be formed at the time the envelope is fabricated and, in this way, may be formed by a suitable metalizing process which is carried out at the same time the envelope is sealed together and exhausted. For example, the area to be coated with metal may be painted with a slurry of titanium hydride and a suitable volatile carrier mixed with a quantity of powder of the metal of which the coating is to be formed. The coating may be copper, nickel or lead, for example. Upon firing to a temperature sufiicient to melt the powdered metal the hydride is disassociated and the metal wets the ceramic in the area painted with the hydride to form a tightly adhering bond. The strips on the opposite sides of the longitudinal center line of the guide lower the inductance in shunt with the anode and compensate for the intervane capacity. The conductor behind the tube tends to establish the center frequency and to optimize power output of the system.

The present invention provides a simple and reliable means of presenting the required shunt inductance for the tube to determine the center operating frequency and the bandwidth over which it may be tuned.

In FIGURE 4 I have illustrated a modification of my invention in which the metallic layers 34, 35 and 36 illustrated in FIGURES l, 2 and 3 have been replaced by conducting rods which are similarly positioned. As illustrated in FIGURE 4 only rods 36' and 34 are visible. These rods extend betwen the anode terminals 21 and 22 and may be positioned in suitable recesses and brazed thereto during the fabrication of the tube.

While I have shown and described particular embodiments of my invention it will be apparent to those skilled in the art that changes and modifications may be made without departing from my invention in its broader aspects and I aim, therefore, 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 as new and desire to secure by Letters Patent of the United States is:

1. A magnetron device including a plurality of generally annular insulators and a plurality of generally annular metal terminals arranged in alternate relation and providing a generally cylindrical envelope for the device, an anode structure supported within said envelope from a pair of said terminals comprising a plurality of anode sections arranged in a cylindrical array with alternate sections connected to and supported from a different one of said terminals and a pair of conductors extending etween the terminals to which said anode sections are connected and located substantially at the opposite ends of a diameter of said envelope.

2. A magnetron device including a plurality of generally annular insulators and a plurality of generally annular metal terminals arranged in alternate relation and providing a generally cylindrical envelope for the device, an anode structure supported within said envelope from a pair of said terminals comprising a plurality of anode sections arranged in a cylindrical array with alternate sections connected to and supported from a ditferent one or" said terminals and three conductors extending between the terminals to which said anode sections are connected, two of said conductors being located substantially at the opposite ends of a diameter of said envelope and a third of said conductors being located substantially midway between said two conductors.

3. A magnetron device including a plurality of generally annular insulators and a plurality of generally annular metal terminals arranged in alternate relation and providing a generally cylindrical envelope for the device, an anode structure supported within said envelope from a pair of said terminals comprising a plurality of anode sections arranged in a cylindrical array with alternate sections connected to and supported from a different one of said terminals and a pair of conductive strips on the exterior surface of the insulator between said pair of terminals and interconnecting said terminals and located substantially at the opposite ends of a diameter of said envelope.

4. In combination, a rectangular wave guide having a tapered section gradually increasing in height and connected at the smaller end thereof with a section of wave guide of uniform height, a generally cylindrical magnetron device having a pair of axially spaced anode terminals coupled to opposite Walls of said wave guide section of uniform height, a hollow cylindrical insulator extending between said anode terminals, a substantially cylindrical anode structure supported from said terminal members within said insulator including a plurality of anode sections positioned in side-by-side and angularly spaced relation throughout the circumference of said terminal members with alternate sections connected to and supported from a different one of said terminal members, a cathode supported within said anode structure to provide a substantially annular space charge region between said anode structure and said cathode and conductors extending between said anode terminals exteriorly of said insulator at locations on the opposite ends of a diameter of said device which is perpendicular to the longitudinal axis of said wave guide.

5. In combination, a rectangular wave guide section, a generally cylindrical magnetron device having a pair of axially spaced anode terminals coupled to opposite walls of said wave guide section, a hollow cylindrical insulator extending between said anode terminal, a substantially cylindrical anode structure supported within said insulator from said terminal members including a plurality of anode sections positioned in side-by-side and angularly spaced relation throughout the circumference of said terminal members with alternate sections connected to and supported from a different one of said terminal members, a cathode supported within said anode structure to provide a substantially annular space charge region between said anode structure and said cathode and conductors extending between said anode terminals exteriorly of said insulator at locations on the opposite ends of a diameter of said device which is perpendicular to the longitudinal axis of said wave guide.

References Cited in the file of this patent UNITED STATES PATENTS 2,463,416 Nordsieck Mar. 1, 1949 2,477,633 Litton Aug. 2, 1949 2,617,965 Kurshan Nov. 11, 1952 2,679,615 Bowie May 25, 1954 2,715,697 Webber Aug. 16, 1955 2,721,295 Posthumus Oct. 18, 1955 2,810,096 Peters et a1. Oct. 15, 1957

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