US2462877A - Electron discharge device - Google Patents

Description

March 1, 1949.

c. v. LITTON ELECTRON DISCHARGE DEVICE 2 Sheets-Sheet 1 INVENTOR CHHRLES M L/TTON ATTORNEY March 1, 1949. c. v. LITTON 2,462,877'

ELECTRON DISCHARGE DEVICE Filed Nov. 23, 1942 2 Sheets-Sheet 2 ATTORNEY Patented Mar. 1, 1949 ELECTRON DISCHARGE DEVICE Charles V. Litton, Redwood City, Calill, assignor to Federal Telephone and Radio Corporation, Newark, N. J., a corporation of Delaware Application November 23, 1942, Serial No. 466,566

14 Claims.

This invention relates to improvements in electron discharge devices and more particularly to a vacuum tube resonator capable of producing large amounts of power at ultrahigh-frequencies. This application is a continuation-impart of my U. S. Patent No. 2,372,213 granted March 27, 1945.

An object of the present invention is to provide a novel high power vacuum tube resonator.

Another object of this invention is to provide a vacuum tube resonator capable of producing larger amounts of power at ultra-high frequencies than heretofore possible.

A further object of this invention is to provide a vacuum tube resonator having relatively low internal capacities for the amount of power which the tube is able to handle.

A still further object of the invention is to provide a novel annular cathode construction.

The invention specifically contemplates the construction of a vacuum tube resonator having a ring-shaped cathode surrounded by concentric annular electrodes such as an anode, or a grid and anode.

In its broadest sense, the invention is directed to a novel vacuum tube resonator in which the capacity between electrodes per active interelectrode area is maintained extremely low.

These and other objects and advantages of the present invention will appear from the following description of a preferred form of vacuum tube resonator embodying the essential features of the invention, illustrated in the accompanying drawings, in which:

Fig. l is a vertical cross-sectional view, in partial perspective, illustrating a preferred embodiment of a vacuum tube oscillator in accordance with the present invention;

Fig. 2 is a'horizontal cross-sectional view of the cathode structure, taken along the line 2 2 of Fig. 1;

Fig. 3 is a circuit diagram of the vacuum tube oscillator illustrated in Fig. 1;

Fig. 4 is a simplified circuit diagram showing the efiective high frequency circuit of the oscillator illustrated in Fig. 1; and

Fig. 5 is a circuit diagram similar to Fig. 4 showing the tube operating as a self-excited oscillator. I

For the successful operation of vacuum tubes at ultra high frequencies, it is known that the electrode spacings must be kept small in order to reduce inter-electrode transit time. On the 7 other hand, the inter-electrode capacities must be kept small so that the resonant circuits can tacting the inwardly directed integral develop the required impedance. Consequently, as tubes have been developed to operate at higher and higher frequencies, the area of the elements has been reduced in order to lower the inter-electrode capacities. The reduction in cathode area means low peak emission and low peak power output under pulse operation, While small plate area means low average power capabilities.

Applicant has discovered, however, that by the use of a cathode formed as a figure of revolution of relatively large radius but with a narrow elfective cathode emission surface, the periphery of this cathode being surrounded by a suitable annular anode, large amounts of power at ultrahigh frequencies can be developed. This follows from the fact that whereas the total capacity between the electrodes is increased, the capacity per unit circumference of the cathode is maintained relatively small. This follows from the fact that the electrical characteristics per unit circumference are dependent upon the thickness of the adjacent electrodes and the distance between them, and are substantially independent of the radius. The resultant tube is, in effect, equivalent to an infinite number of tubes connected in parallel, each tube having a low unit inter-electrode capacity. In such event, the power developed is greatly increased but the extra capacity introduced does not add the capacity already existing in the ordinary sense, because the circular symmetry conditions existing at one point along the circumference cannot influence the conditions at any otherpoint as contrasted, for example, to known types of tubes having concentric elements in which the radius of the centrally positioned cathode is extremely small relatively to its length. One form of such a figure of revolution tube meetin the desired conditions outlined above, is described by way of example below, while another form of such a tube is shown in my above identified copending application.

The vacuum tube resonator illustrated in Fig. 1 is provided with a cathode l0 having a configuration which meets the requirements outlined above. It will be noted that the cathode l0, shown in more detail in Fig. 2. is provided with a hollow ring having a relatively narrow periphery emitting surface l2 whose radius is substantially greater than its width in the longitudinal direction. The cathode l0 may be immediately supported on either side by a pair of partially oblique disks I52 and I53 having outwardly directed flanges I66 and I6! spaced close to but not concathode flanges I64 and I65, except through a plurality of circumferentially spaced intermediate metal disks I68, preferably spot-welded between the opposing flanges. The disks I52 and I53, in turn, are supported by a cylindrical shell formed by the two half cylinders 46 and I69, and connected to- I gether through opposed flanges I12, I13. The half cylinder I69 may be strengthened by the cylindrical corrugated insert IN. The lower half cylinder 46 is supported by a cup-shaped member I4 at one end which, in turn, is attached to a hollow supporting tube I6. The other end of the tube I6 is attached in any suitable manner to a metal closure member I1 connected to a glass seal I8. The latter, in turn, is connected to the end member 20 to which is attached the rod 22 passing through the tubular support I6 and extending upwardly into the interior of the cylinders 46, I69 for connection with the cathode heaters 24 of which there may be six connected in parallel and spaced circumferentially within the cathodeID. One end of each heater 24 may be directly connected as by wire 26 to a disk I62 mounted on the end of the rod 22 by means such as screw I6I; the rod 22 will then form one of the heater leads. The other end of the heaters 24 may be attached by lead 25 to a ring I63 fastened on the tubular support I6 between a rigid collar I14 and a threaded collar I15 threadedly mounted in the upper end of the support I6 which then serves as the other heater lead. The leads 25 and 26 will extend through suitable openings in the cylinders 46, I69. To further increase the thermal efficiency of the cathode, six heat shields I10 are placed behind the respective heater coils 24, and are attached to the cylinder 46 as by brackets I'II.

' The cathode construction, described above is advantageous in many respects. The spacing between the emitting surface I2 and its supporting disks I52 and I53 acts as a thermal insulation preventing excessive heating of the disks and permitting the dissipation of such heat. The emitting surface I2 is electrically connected to the disks I52, I53 by the capacity between the opposed flanges I64, I61 and I65, I66'and directly connected by the metal disk I68.

Coaxial cavity resonators 32 and 34 in the form of split toroids are positioned coaxial with and upon opposite sides of the annular cathode emitting surface I2. In the preferred embodiment of the invention illustrated, the resonator 32 is spaced from the cylindrical member I69 and supported by an inverted cup-shaped member 36 mounted upon the end of a longitudinally adjustable bar 38. The bar 38 is slidably mounted in a centrally positioned opening within the tube cap 40 and at its outer end is provided with suitable threads 42 which are engaged by a nut 44. It will be clear to those skilled in this art that rotationof the nut 44 will result in an upward or .downward movement of the bar 38, and a resulting adjustment in the position of the resonator 32. The end of the tube is sealed despite the presence of the longitudinally movable bar 38 by suitable means such as a flexible metal membrane 48 tightly conencted about the bar 38 at its center, and connected about its circumference to a metallic wall '50 of the tube.

The coaxial resonators 32, 34 preferably form the high-frequency input circuit for the vacuum tube oscillator and coupling there-to may be made by a suitable loop I projecting through an opening into the resonator 34. The loop is supported by a coaxial line in the form of an outer tubular member 52 surrounding an internal lead 54. A

Y 4 suitable seal 56 closes tube 52 and holds the lead 54 in position. The tube 52 is held in place relatively to the resonator 34 by firmly connecting it to the lower outer shell 58 of the tube. In accordance with the preferred form of invention, and in contrast to the mounting of the resonator 32, the lower coupled resonator 34 is rigidly attached to the cup-shaped cathode support I4. Depending from the center of the lower outer shell 58 is a metal cylinder 60, connected by glass cylinder 62 to the metal closure member I1, thus completing the sealing of the lower end of the electron discharge device.

The grid is positioned concentric to the cathode I0, being spaced relatively closely to the active cathode surface I2 and also relatively closely to the outer annular surfaces of the resonators 32, 34. The grid 64 may consist of a plurality of circumferentially spaced wires 66 supported at their ends by rigid annular members 68 and 12. These annular members may be strengthened, if desired, by respective corrugated cylinder I56, inside the grid and corrugated cylinder I58, outside the grid. The lower end of the grid support 68 may be turned over as a flange 16 connected to a supporting ring 18 by suitable means such as a clamping ring I50 and screws 80. The ring 18, in turn, is mounted on one or more rods 8| extending outside of the tube through means such as the cylinder 82, the cylindrical tube 84 and the closure cap 86. The rod 8I may thus serve as a grid terminal for the grid tube.

Radially spaced from the grid 64 and in juxtaposition with the coaxial resonators 32 and 34 are positioned a second pair of generally open toroidal coaxial resonators 88 and 90. There are, thus, four cavity resonators about the electrodes, the first and second cavity resonators 88 and 90 being supported rigidly by the metallic wall 50 of the tube, the third cavity resonator 34 being supported rigidly by the cathode I0 and the fourth cavity resonator being adjustably supported by the cupshaped member36. The resonator 90 is rigidly connected to and supported by the lower outer shell 92 of the tube, and at its upper end is provided with an inwardly turned flange 93 supporting the annular anode disk 94. The upper resonator 88 is rigidly attached to and supported by the upper outer shell 50 of the tube and is provided with a similar inwardly directed annular flange at its lower end. It will be thus seen that the anode disk 94 is, in efiect, mounted between the resonator flanges 93 and 95 and is directly electrically connected to one side of these resonators. The flanges 93 and 95 are so positioned. that the inner periphery of the anode 94 extends about the grid 64 and is concentric with the active cathode surface I2. The spacing between the internal anode surface and the grid 64 is made as small as desired, noting, however, that the internal annular surfaces of the resonator 88 and 90 are also spaced from the surrounded grid supports 68 and 12.

The high frequency output may be taken from the resonator 88 by means of a suitable loop 96 extending through an opening therein and mounted within an output 98 rigidly electrically connected to the resonator. The loop 96 is directly connected at one end to the tube 98 and its other end is in the form of a lead I00 extending concentrically within the tube 98 and out through a suitable glass seal I02, closing the outer end of the tube.

A second high frequency output may be taken from the resonator 88 through an oppositely posioff the outer end of the tioned loop I18 extending through an opening therein and mounted within a tube I85. The loop I18 in this case is directly connected at one end to the tube I85 and its other end is in the form of a lead I" extending concentrically within the tube I85 and out through a suitable glass seal 288.

If it is desired to provide water cooling of the anode, an arrangement such as shown in Fig. 1 may be used. A continuous piece of tubing starting from the inlet junction box I83 is wound inwardly on the upper outer surface of the anode 98 in a flat spiral to form tubes I88, WI and H82, ending in the outlet junction box I88. A second piece of tubing runs from the inlet junction box i83, forming tubes I 98, ISI and I92, also ending at the outlet junction box I88.

The high frequency electrical circuit resulting from the construction illustrated in Fig.1 can best be understood from the circuit diagram of Fig. 3. Beginning with the high frequency input lead 55 connected to the loop 5I, it will be seen that this is coupled to the resonator 34. The other end of the loop 5! will be electrically connected to the anode 94 via the cylindrical support 52, and the tube shell sections 58 and 92. This same end of the loop will also be electrically connected to the resonator 32 through the upper tube shell 58, the flexible metallic membrane 48, the movable bar 38 and the inverted cup-shaped support 38.

The resonator 32 will be variably coupled at one end to the cathode I8 by reason of the serial capacitances existing between the adjacent parts, represented in Fig. 3 as Caz-169 and C153k. The other end of the resonator 32 will be capacitatively coupled to the grid by reason of the capacitance existing between the outer surface of the resonator 32 and the surrounding grid support; this capacitance is representedin Fig. 3 by C32g. The input resonator 38 will be connected on the one hand to the cathode I0 through the cup-shaped support It and the capacitance 01521:, as previously described, and at the other end capacitatively coupled to the grid by reason of the capacitance existing between the outer surface of the resonator 38 and the immediately adjacent surrounding grid support; this capacitance is represented in Fig. 3 as Care.

The output loops 96 and Ii8 are, as previously described, each directly connected at one end to the anode 94 which, at the same time, forms a center tap between the resonators 88 and 98. The other ends of the loops are, of course, connected to the respective output leads I88 and I'll. The inner, opposite ends of the resonators 88 and 98 are capacitatively coupled to the grid by reason of the capacitance existing between their respective inner surfaces and the adjacent grid supports.

These capacitances are represented in Fig. 3 as Case and 090g, respectively. The high-frequency oscillator circuit is completed by the internal inter-electrode capacities indicated in Fig. 3 as Cpg, between grid and anode, Cpk between anode and cathode, and Cgk between grid and cathode.

The simplified high frequency circuit of the tube operating as a high frequency tuned amplifieris illustrated in Fig. 4, in which the capacitances C341,, (31521:, Cazg, Caz-169, 01531;, Gan and Casg have been neglected, since they will all be effectively short circuited at ultra high frequencies. Under these conditions, the resonators 32, 34 and 88, 90 may be shown as lumped inductors forming tank circuits with the grid cathode capacitance Cgk and the anode-grid capacitance Cpg, respectively. The resonators 32, 34, 88 and 98 are so proportioned as to act as inductive reacors at the generating frequency. The tank circuit represented by the resonators 32, 34 and the shunt capacitance Cgk may be tuned by varying the dimensions of the resonator 32, as previously described. While this also varies the capacitance 032-169 slightly, this variation is unimportant and can be neglected at high frequencies when this capacitance is an efiective short circuit.

Additional means such as can be readily designed by those skilled in this art may be used to tune resonators 88 or 98, by making one of them slidable similarly to resonator 32.

If the tube is to be used as a self-excited oscillator, a circuit such as illustrated in Fig. 5 may be used. In this case the input 52, 58 is connected to one of the outputs 98, I00 through means such as a coaxial line ZII), 2I2. The output of the self-excited oscillator may then be taken from ITI, 885.

It will be seen that the construction described above is admirably adapted to provide a vacuum tube oscillator with high power for ultra-high frequencies. While there is a large amount of active inter-electrode surface for producing high power, the thickness of the effective cathode surface and of the effective anode surface in the longitudinal direction has been kept extremely narrow and, as a result, undesired capacities between these elements have been avoided and the resulting capacity per unit of circumference is extremely small. At the same time, the arrangement of the resonators to form the oscillating circuit is relatively neat and compact and provision is made for adjustment of a resonator, if desired.

While the invention has been described in connection with a certain specific constructional embodiment, it will be apparent that the novel features of the invention may be applied to tubes having other structural relationships. For example, the principle of obtaining high power at ultra-high frequencies is applicable to tubes constructed as diodes, as well as triodes. The resonators themselves may be of other configurations known to the art and the manner in which the individual parts of the tube are constructed is without any particular importance. While a special improv d form of cathode has been shown it is only essential, however,. for the optimum operation of a vacuum tube oscillator in accordance with the present invention, that the cathode be shaped with an outer efiective peripheral surface whose thickness is smaller than its radius. This form of cathode may be variously described as annular, ring-shaped or by any other similar connotation. Furthermore, it is important that the anode, of preferably substantially the same thickness as the cathode, surrounds the cathode concentrically in order to provide a minimum of inter-electrode capacitance with a maximum of 1 active inter-electrode energy transferred.

Accordingly, while I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of my invention as set forth in the objects and the accompanying claims.

What is claimed is:

l. A high frequency electron discharge device including a pair of electrodes comprising a substantially ring-shaped cathode whose outer radius is substantially greater than its longitudinal capacitatively coupled to said cathode, directly connected to said anode and coaxial with both of said electrodes, and sealed envelope-forming means enclosing said electrodes.

3. A high frequency electron discharge device including a pair of electrodes comprising a substantially ring-shaped cathode whose outer radius is substantially greater than its longitudinal dimension, and a ring-shaped grid surrounding the peripherey of and concentric with said cathode, means forming a cavity resonator capacitatively coupled to said grid and to said cathode and coaxial with both of said electrodes, and sealed envelope-forming means enclosing said electrodes.

4. A high frequency electron discharge device comprising a substantially ring-shaped cathode whose outer radius is substantially greater than its longitudinal dimension, a ring-shaped grid surrounding theperiphery of and concentric with said cathode, a ring-shaped anode surrounding the periphery of and concentric with said grid, means forming a cavity resonator capacitatively coupled to said cathode, directly connected to said anode and mounted coaxial with all of said electrodes, and sealed envelope-forming means enclosing said electrodes.

5. A high frequency electron discharge device comprising a substantially ring-shaped cathode whose outer radius is substantially greater than its longitudinal dimension, a ring-shaped grid surrounding the periphery of and concentric with 8 grid, means forming a cavity resonator coupled to said cathode and one of said other electrodes, and mounted coaxial with all of said electrodes, and sealed envelope-forming means enclosing said electrodes.

9. An annular cathode comprising a hollow ring, open on its inner side, whose outer periphery constitutes an electron emitting surface,-

a pair of disks, one positioned on each side of said ring, circumferentially spaced metallic spacing members connecting said disks to the respective adjacent facesof said ring, and a hollow cylinder extending through and supporting said disks, the diameter of said cylinder being substantially less than the outer diameter of said ring.

10. An annular cathode according to claim 9, further comprising cathode heating means positioned inside said ring between said ring and cylinder, heater terminals mounted within said cylinder, and leads extending through said cylinder from said terminals to said heating means for supporting the latter.

11. An annular cathode according to claim 9, further comprising cathode heating means positioned inside said ring between said ring and cylinder heater terminals mounted within said cylinder, leads extending through said cylinder from said terminals to said heating means for supporting the latter, and a heat ,hield connected to said cylinder and mounted close to said heating means between the same and said cylinder.

12. A high frequency electron discharge device comprising, a hollow cylinder having circumferentially spaced openings near its center, arouately shaped heating means surrounding the center of the cylinder, leads extendin from said heating means through said openings into said cylinder, heater lead terminals within said cylin- 40 der, said terminals including a hollow tube exsaid cathode, a ring-shaped anode surrounding and concentric with said grid, means forming a cavity resonator capacitatively coupled to said grid and to said cathode and mounted coaxial with all of said electrodes, and sealed envelopeforming means enclosing said electrodes.

6. A high frequency electron discharge device comprising a substantially ring-shaped cathode whose outer radius is substantially greater than its longitudinal dimension, a ring-shaped grid surrounding the periphery of and concentric with said cathode, a ring-shaped anode surrounding and concentric with said grid, means forming a cavity resonator capacitatively coupled to both said grid and cathode and mounted coaxial with all of said'electrodes, and sealed envelope-forming means enclosing said electrodes.

'7. The combination according to claime, in which said cavity resonator-forming means is directly connected to said anode.

8. A high frequency electron discharge device comprising a cathode in the form of a hollow ring, open at its center, whose outer radius is substantially greater than its longitudinal dimension, a pair of disks on each side of said ring, circumferentially spaced metallic spacing members connecting said disks to the lateral faces of said ring, and a hollow cylinder supporting said disks, an annular grid surrounding the periphery of and concentric with said cathode, an annular anode surrounding and concentric with said annular tending downwardly from and coaxial with said cylinder, means connecting said heater leads to said heater terminals for supplying current to and simultaneously supportin said heating means, means supporting one end of said cylinder from said tube, a hollow ring-shaped cathode surrounding and partially enclosing said heating coils, means supporting said cathode from said cylinder, an annular grid spaced from and surrounding said cathode, an annular. anode spaced from and surrounding said cathode grid, a generally cylindrical metal member forming an outer wall of said electron discharge device, coaxial with said electrodes and supporting said anode, said anode having a radial extension projecting through the outside of said wall, a pair of cavity resonators in the form of hollow toroids open at one side, supported by and within said cylindrical member with their open sides respectively on opposite sides of the said annular anode and their inner peripheries spaced from but adjacent the outer periphery of said grid, a third cavity resonator in the form of a hollow toroid having an open side, supported by said hollow cylinder with its open side facing one lateral face of said cathode and its outer periphery spaced from but adjacent the inner periphery of said grid, a fourth cavity resonator in the form of a hollow toroid having an open side, mounted with its open side facing the other lateral face of said cathode, its outer periphery spaced from but adjacent the inner periphery of said grid, and its inner periphery spaced from but adjacent the outer surface of said hollow cylinder, means adjustably supporting said fourth resonator from said generally cylindrical metal member, said means including means sealing thetube of said cylindrical member, means sealing the bottom of said cylindrical member and forming therewith an evacuated vessel enclosing said electrodes, means supporting said grid from said bottom sealing means, input coupling means extending through the bottom sealing means into said third resonator, and output means extending through said cylindrical member into one of said pair of resonators.

13. A high frequencyelectron discharge device according to claim 12, further comprising arcuately shaped heat shielding means supported by said hollow cylinder intermediate the latter and said heating means.

14. A high frequencyelectron discharge device according to claim 12, in which both said coupling means are formed as loops, one end of each of which is galvanlcally connected to said anode 10 through said outer cylindrical member, and the other ends of which are formed as leads projecting outside of the electron discharge device.

CHARLES V. HTTON.

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

UNITED STATES PATENTS

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