US2795735A - Ultrahigh-frequency tube - Google Patents

Description

June 11, 1957 G. D. O'NEILL ULTRAHIGH-FREQUENCY TUBE Filed Aug: 4, 1951 3.9q 39a /39C INVENTOR GEORGE D. ONEILI.

wi /W ATTORNEY United States. Patent ULTRAHIGH-FREQUEN CY TUBE George D. ONeill, Manhasset, N. Y., assignor to Sylvania Electric Products Inc., a corporation of Massachusetts Application August 4, 1951, Serial No. 240,329

3 Claims. (Cl. 315-44) The present invention relates to electron tubes primarily intended for micro-wave operation and used with a cavity resonator.

This application is a continuation in part of my copending applications, Ser. No. 681,454 filed July 5, 1946, which has matured into United States Patent No. 2,707,771 of May 3, 1955, Ser. No. 14,807 filed March 13, 1948, which has matured into United States Patent No. 2,679,- 591 of May 25, 1954, Ser. No. 31,614 filed June 8, 1948, which has matured into United States Patent No. 2,707,- 750 of May 3, 1955, and Ser. No. 61,703 filed November 23, 1948, which has matured into United States Patent No. 2,756,360 of July 24, 1956. In those applications as in the present application, the utilization of an accelerator grid close to a secondary emissive anode or dynode is disclosed and claimed in various combinations. An object of the present invention is to improve the operation and construction of a dynatron electron discharge tube and to improve the combination of such tube with a cavity resonator. Further objects and features of novelty will be apparent from the following detailed description of illustrative embodiment of the invention in its various aspects. In the single figure of the drawing there is shown a longitudinal cross section of one embodiment which is, in its essentials, a figure of rotational symmetry.

In the drawing an evacuated envelope of glass or the like encloses an assembly of electrodes including a cathode 12 having a heater 14 to provide thermionic electron emission from the upper coated portion 16 of cathode 12. An electrostatic collimating or focusing electrode or shield 18 is provided that largely encloses cathode 12 but is provided with a single, centered perforation 20 above electron-emissive surface 16. Aligned with this perforation along the axis of envelope 10 is a grid 22 and an anode 24, the surface of which (opposite grid 22) is either coated or otherwise treated in a manner wellknown to the art to provide for copius emission of secondary electrons upon bombardment by primary electrons. Grid 22 is formed of wire mesh united to a supporting disc 26 that is centrally dished to project toward the anode and is hermetically sealed radially through the envelope 10. Anode 24 is similarly formed in a disc 28 that is similarly hermetically sealed radially through the wall of envelope 10 and is dished toward the grid. Perforations 26a and 28a are provided in discs 26 and 28 within envelope 10 for facilitating the evacuation of the gas within envelope 10 during manufacture of the tube.

In the drawing, grid 22 and anode 24 serve as poles of a bi-part metal cavity resonator, connecting discs 26 and 28 also serving as parts of the resonator. The grid and anode operate at difierent D. C. potentials. As poles of the resonator they also operate at opposite A. C. potentials, in an A. C. circuit extending along the resonator surfaces between the grid and the anode. In this sense the grid and anode form parts of opposite resonator walls. One part or wall of the resonator includes anode 24, disc 28, internal cylinder 36, slidable metal annulus 32, external cylinder 38, and fixed wall portion 34. Cylin- 2,795,735 Patented June 11, 1957 der 36 is splitinto two half-cylinders for facilitating mechanical assembly. The other part or wall of the biapart resonator which operates at opposite A. C. potential from the first-mentioned part includes grid 22 and metal disc 26. i 'i In operation, grid 22' is energizedwith a relatively high value of D. C. potential, and dynode or anode 24 is energized with a lower value of D. C. potential, relative to cathode 12 as indicated by terminals 39g, 39a and 39c of D. C. supply 39. In order that the anode and the grid may be operated at this difference of potential, the metallic structure of the resonator is breached by a bypass structure including a layerof D. C. insulation. This may be introduced at various places between the grid and the anode. In the form shown a layer 40 of dielectric material is shown interposed between portions 26 and 34 of theresonator. It may alternatively be arranged as shown in Fig. 1 of my application Ser. No. 31,614.

If the resonator were removed and various D. C. potentials were applied to the several electrodes, it would be observed that at some part of a range of voltage variation a rise of potential applied to the anode or dynode would be accompanied by a drop in its current. This represents negative resistance, which is utilized in producing microwave oscillations by assembling the grid and the anode to the remainder of the resonator. The oscillation is largely confined within the cavity resonator, except for the power coupled out for example, by a loop (not shown) conventionally used with cavity resonators. The resonator and tube can be used for other or additional purposes than for oscillation, and with various power couplers, as disclosed in said copending applications.

When the tube is connected to the resonator as shown, oscillations are established at a frequency determined by the resonator structure, including both the metal portions external of envelope 10 and the disc terminals sealed through the envelope, as well as the dynode and grid electrodes. The grid and the dynode actually are part of the resonator, and affect its natural resonant frequency.

The structure of the several electrodes as shown is quite desirable, based on various considerations. The provision of the portion 10a of the envelope above anode 24 is effective in avoiding physical displacement of that anode in relation to the grid due to the pressure difference developed during exhaust; but the exhaust holes 28a might, if desired, be omitted together with envelope portion 10a. Similarly the shield 18 and cathode 12 may take various forms, for example, such as the form in application Ser. No. 61,703, where the shield electrode interposed between the cathode and the accelerator grid, and the shield is there seen to have additional valuable properties. The tube structure shown therein, and the structure in my copending application Ser. No. 14,807, may be used together as other forms of the combination here described in detail, and the disclosures in those applications form part of the disclosure herein.

Further variations in detail will occur to those skilled in the art, and, therefore, it is appropriate that the appended claims be accorded a latitude of interpretation consistent with the spirit and scope of the invention.

What is claimed is:

1. A high frequency tube comprising an enclosing envelope, an electron-emitting cathode, a reentrant metal member sealed to said envelope in a vacuum-tight manner, said reentrant metal member having a central transversely extending section acting as the anode of the tube, the internal face of said transversely extending section having a coating of secondary emission material, an inverted disc-shaped metal member having its outer margin sealed vacuum-tight through the wall of said envelope and having its central portion in the form of a foraminous transversely extending section substantially parallel to the transversely extending section of said reentrant member, a perforated shield surrounding said cathode allowing electron emission towards the anode, and means external of said envelope and connected to the rims of said metal member to form therewith a cavity resonator with the boundary walls thereof D. C. insulated from each other and separate connections for said boundary walls for applying thereto different positive potentials with respect to the cathode.

2. A high frequency tube comprising an enclosing envelope, an electron-emitting cathode, a metal member sealed to said envelope in a vacuum-tight manner, said metal member having a central transversely extending section acting as the anode of the tube, the internal face of said transversely extending section having a coating of secondary emission material, a disc-shaped metal member having its outer margin sealed vacuum-tight through the wall of said envelope and having its central portion in the form of a foraminous transversely extending section substantially parallel to the transversely extending section of said reentrant member, a perforated shield surrounding said cathode allowing electron emission towards the anode, and means external of said envelope and connected to the rims of said metal member to form therewith a cavity resonator with the boundary walls thereof D. C. insulated from each other and separate connections for said boundary walls for applying thereto diiferent positive potentials with respect to the cathode.

3. A high frequency device, comprising an electronemitting cathode, a metal member spaced from said cathode and coated with secondary electron emissive material, an accelerating electrode interposed between said cathode and said metal member, a cavity resonator embodying D. C. dividing means and providing high frequency connection of said accelerating electrode and said metal member,

and a perforated shield surrounding said cathode allowing electron emission towards the accelerating electrode.

References Cited in the file of this patent UNITED STATES PATENTS 2,517,726 Skellett Aug. 8, 1950

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