US2556813A - Ultra high frequency thermionic tube - Google Patents

Description

`lune l2, 1951 R. R. LAW

ULTRA HIGH FREQUENCY THERMIONIC TUBE l Filed May 13, 1947 W W d ATTORNEY I Patented June 12, 1951 2,556,813 ULTRA HIGH FREQUENCY THERMIONIC TUBE Russell R. Law, Princeton, N. J., assignor to Radio Corporation of America, a corporation of Dela- Waffe Application May 13, 1947, Serial No. 747,789

17 Claims. (Cl. 315-40) This invention relates to electronic discharge tubes incorporating tuned or tunable circuits and particularly relates to internal circuit tubes suited for use in wide-band, cathode-modulated power amplifiers at ultra-high frequencies.

1n `accordance with the invention, the anode and cathode circuits of a push-pull amplifier are each formed by a trough-shaped conductor whose longitudinal edges form elongated anodes or cathodes and whose electrical length from cathode to cathode, or anode to anode, is an odd number, of half wavelengths. The conductors are disposed on opposite sides of a grid partition having elongated grid slots with which the anodes and cathodes are aligned and which serves as a grounding flange for the grids.

Further in accordance with the invention, the trough-shaped conductors are each supported by a conductive structure extending therefrom at a potential node point to minimize or eliminate insulating and filtering difficulties, and the exteriorly accessible mountings for the supporting structures may be flexible or deformable to permit adjustment of the inter-electrode capacitances and so provide for tuning of the internal circuits of the tube over an appreciable range of frequencies.

Further in accordance with the invention, the supporting structures and the trough-shaped circuit members are hollow or provided with passages for circulation of cooling liquid and, in the case of the cathode-circuit member and support, for encasing the supply leads of the cathodeheater element which is disposed within and adjacent the cathode faces of the cathode-circuit member.

The invention further resides in features of construction, combination and arrangement hereinafter described and claimed.

For` more detailed understanding of the invention and for illustration of one form thereof, reference is made to the accompanying drawings in which:

Figure 1 is a sectional view of a tube having internal push-pull cathode and anode circuits;

Figure 2 is a sectional view taken on line 2-2 of Fig. 1;

Figure 3 is a sectional view taken on line 3-3 of Fig. 1;

Figure 4 is a perspective View of the tube of Fig. 1 with parts omitted and parts broken away;

Figure 5 is a sectional View of the anode circuit member taken on line 5 5 of Fig. 2; and

Figure 6 is a schematic diagram of the amplier circuit and associated components.

Referring to Figures 1 to 4, as exemplary of an internal circuit tube embodying the invention, the envelope member l0 of electronic tube II is a thick cylindrical tubular member, preferably of copper, divided into a cathode compartment I2 and an anode compartment I3 by a thick partition Ill, also preferably of copper, formed integrally with or joined to the tubular envelope I and extending across the envelope l0 along a diametral plane. The elongated slots I5a, I5b extending longitudinally of the partition or plate hi are parallel to the axis of the tube envelope and are bridged by grid wires I6, preferably of tungsten and attached as by silver solder to the plate I4 which therefore serves as a grounding flange for the grids of the tube.

The cathode circuit of the tube II is formed by a channel or trough-shaped conductor I1 whose longitudinal edges or ends I8a, Ib form the cathodes of the tube. The length of the conductor Il as measured from one cathode surface to the other approximately corresponds with one, or other odd number of, half wavelengths so that the instantaneous potentials of the cathodes are out of phase so far as impressed input carrier-frequency energy is concerned. The member I1 is so shaped and so .positioned in compartment lf2 that the elongated cathodes Ia, I8b thereof are respectively in alignment with the grid slots I5a, Ib.

The anode circuit of tube I I is formed by a second channel or trough-shaped conductor I9 whose longtiudinal edges or ends 25a, 20h form the anodes of the tube. The length of conductor IQ as measured from one anode surface to the other approximately corresponds with an odd number of half wavelengths (preferably one) at the intended operating frequency so that the instantaneous radio-frequency potentials of the anodes are 180 out of phase. The member I9 is so shaped and so positioned in compartment I3 that therelongated anodes are in alignment with the grid slots Ia, Iib and the cathodes I8a, I8b.

Thus, the two trough-shaped conductors I'I, I9 form the inductances of a split loop completed by the inter-electrode capacitances.

With the construction described `and disclosed, the operating frequency can be predetermined quite exactly in terms of a lumped inductance fixed by the circuit configuration and a lumped capacitance consisting substantially solely of the capacitance between the active electrode surfaces. Except insofar as ythe inter-electrode spacing may be varied, as hereinafter described, for tuning purposes, this circuit arrangement provides 3 minimum stored energy per unit area of active electrode surface `and so facilitates the attainment of high power outputs at ultra-high frequencies.

By way of example, to obtain a power output of somewhat more than a kilowatt at a frequency of about 1000 megacycles, each cathode may be about ten centimeters long by one centimeter wide. With an anode-grid spacing of about one millimeter, the anode-grid capacitance is about 17 micro-microfarads. With a direct-current anode voltage of 1000 volts and a radio-frequency swing of 400 volts, peak value, the stored energy is only 136.10-8 joules While the active energy, or power output, is of over one kilowatt: thus the band width is over 100 megacycles.

For use of the tube ll as an amplifier and in avoidance of self-generated oscillations, the length D, Fig. 1, of the partition i4 beyond the grid slots and circuit-conductors Il, I9 should be great enough to prevent feedback from the anode circuit to the grid circuit. This distance is not prohibitively great because any radiation from the circuits is rapidly attenuated toward the ends of the tubular member l because the operating frequency is substantially lower than the cut-off frequency of the compartments l2 and I3. The closure members 2l, 2l of the evacuated tube envelope may be of glass to permit visual inspection of the interior of the tube. In such case particularly, the rings 22, 22 are provided effectively to extend the tubular envelope member l0 to a length further attenuating any radiation from the oscillating circuits to such eX- tent it creates no disturbing external effects in nearby circuits or equipment. The closure members 2i, 2| may be of metal in which event the internal high-frequency circuits of the tube are completely shielded or isolated by the tube envelope.

Further in avoidance of stray external fields, the conductors 23, 24 for supplying the directcurrent operating voltages of the anodes and cathodes are connected to potential node points of the cathode and anode circuit conductors Il and I 9 respectively. As there is no difference between the radio-frequency potentials of these points and the tube envelope, the use of filter chokes and by-pass condensers is obviated; furthermore, the problem of insulating the supply leads is lessened as only the direct current potentials need be taken in consideration.

The supply conductors 23, 24 are preferably also utilized to provide the mechanical support of the circuit members Il, I9 and for that purpose are of construction affording sufficient rigidity to insure continued alignment of the cathodes and anodes with the grids. When it is desired to provide for operation at substantially different frequencies, the supports 23, 24 are mounted for movement of the loop elements Il, I9 toward and away from the grid plate I4 for adjustment of the inter-electrode capacitances. To allow this movement and yet preserve the airtight integrity of the tube envelope, the seals 4 of the bellows and cap are molded into the glass seal ring 2l.

The protruding ends of each of the supports 23, 24 is secured to a strip 28 in which is rotatably journalled a pair of nuts 29 threadably engaging the rods 30 amxed to the tube envelope I0, directly or through the posts 3| which are of insulating material if the bridging strip 28 is of metal. If desired, the tuning members may be ganged for adjustment in unison. Other arrangements providing for tuning adjustment of the velectrode supports 23, 2Ll and for insulating them from the tube envelope may, of course, be used. Without undue change of its output, the one kilowatt amplifier tube above mentioned may be tuned throughout the range of from about '700 to 1300 megacycles at a band width of more than about megacycles.

The circuit elements Il, i9 and the supports 23, 24 may be hollow to provide for circulation of cooling liquid and in the case of members l1, 23 for passage of leads 32 extending to a heater 33 Within the member vIl in heat transfer relation to the cathodes la, |81). The anode circuit member I 9, Figures 2 and 5, may be provided with chambers 33, 34 connected to each other by cross-passages 35, 35 and to inlet and outlet passages 36, 355 provided by the hollow support 24 itself or by piping therein. If cathode cooling is necessary or desirable, the cathode circuit member i1 may be provided with similar passages for flow of cooling liquid.

Radio frequency energy to be amplified may be introduced into the cathode compartment or cavity I2 in any suitable manner, preferably by a concentric line 36 whose outer conductor 3l is connected to the metallic envelope of tube lIl and whose inner conductor 38 is connected to or terminates in a coupling loop 39. The cathode-to-cathode dimension of the loop member I7 is such, as above described, that the cathodes are excited in push-pull relation by the impressed radio frequency input energy. The amplified radio frequency energy may be transmitted from the anode cavity I3 by a similar concentric line having its outer conductor 4I connected to the tube envelope and its inner conductor 42 connected to or terminating in a coupling loop 43.

For cathode modulation of the amplier, the cathode conductor 23 is connected to one end of resistor Ml, Figure 6, generically representative of a physical resistor or the direct-current resistance of the secondary winding of a modulating transformer. The other end of the resistor or winding is grounded to the negative terminal B of the sourse of direct-current anode voltage. In either case, the grids-of the tube are negatively biased by the voltage drop due to flow of anode-cathode current and the audio or video modulating voltage is effectively impressed between the cathodes and grids of the tube. Alternatively, the radio frequency input of the tube may be modulated at audio or video frequencies.

Because of its wide-band width, the internal circuit tube of the invention is well suited as the power-amplifier of a television or frequencymodulated transmitter.

It shall be understood the invention is not limited to the particular construction disclosed and that changes and modifications may be madeA within the scope of the appended claims.

What is claimed is: l. An electronic discharge device comprising an evacuated envelope including an elongated,

section, a at conductive partition extending.

across said tubular member along a diametral plane and providing two compartments and having an elongated grid slot, and elongated cathode and anode structures respectively disposed in said compartments in alignment with each other and said grid slot.

Y2. An electronic amplifier device comprising an evacuated envelope including a tubular conductive member, a conductive partition extending across said member internally7 thereof and providing two compartments and having a pairof' elongated grid slots, an open-loop member disposed in one of said compartments and whose end faces disposed in alignment with said grid slots provide elongated cathodes, and a second open-loop member disposed in the other of saidv 'compartments and whose end faces disposed in` alignment with said grid slots provide elongated anodes.

3. A push-pull amplifier device comprising an evacuated envelope including a tubular conductive member, a conductive partition extending across said member internally thereof and providing two compartments and having a pair of elongated grid slots, a pair of elongated cathodes disposed in one of said compartments in alignment with said elongated grid slots, a trough-y ing across said member internally thereof :andi providing tWo compartments and having a pair of elongated grid slots, an open-loop member disposed in one of said compartments and-'whose end faces disposed in alignment with said grid slots provide elongated cathodes, a second'openloop member disposed in the other of said compartmentsy and whose end faces disposed in alignment with said grid slots provide elongated anodes,v and insulated conductive supports respectively extending from said open-loop members at potential nodes thereof.

5. A push-pull amplifier comprising a conductive plate having a pair of elongated slots bridged by grid elements, a pair of elongated cathodes spaced from one side of said plate in alignment with said grid slots, a push-pull cathode circuit having lumped capacitance consisting substantially solely of the capacitance between said cathodes and said grid elements and having lumped inductance consisting substantially solely of the inductance of a half-wave loop member connecting said cathodes, a pair of elongated anodes spaced from the opposite side of said plate in alignment with said grid slots, and a push-pull anode circuit having lumped capacitance consisting substantially solely of the capacitance between said anodes and said grid elements and having lumped inductance consisting substantially solely of the inductance of a second half-wave loop member connecting said anodes.

6 6. A push-pull amplifier comprising a conduce tive plate having a pair of elongated slots bridged by grid elements, a pair of elongated cathodes spaced from one side of said plate in 4alignment with said grid slots respectively, a

push-pull cathode circuit having lumped capacitance consisting substantially solely of the capacitance between said cathodes and said grid elements, a half-wave loop member connecting said cathodes and providing substantially all of the lumped inductance of said push-pull cathode circuit, la pair of elongated anodes spaced from the opposite side of said plate in alignment with said grid slots respectively, a push-pull anode circuit having lumped capacitance consisting substantially solely of the capacitance between said anodes and grid elements, and a half-wave loop member connectingsaid anodes and providing substantially all of the lumped inductance of Hsaid push-pull anode circuit.

"1'. A push-pull amplier comprising a conductive plate having a pair of elongated slots y bridged by grid elements, a pair of elongated cathodes spaced from one side of said plate in alignment with said grid slots respectively, a push-pull cathode circuit'having lumped capacitance consisting substantially solely of the capacitance between said cathodes and said grid elements, a half-wave loop member connecting said cathodes and providing substantially all of the lumped inductance of said push-pull cathode circuit, a pair of elongated anodes spaced from the opposite side of said plate in alignment with said grid slots respectively, a push-pull anode circuit having lumped capacitance consisting substantially solely of the capacitance between said anodes and grid elements, aV half-wave loop member connecting said anodes and providing substantially all of the lumped inductance of said push-pull anode circuit, and means supporting said half-wave loop members for movement toward and away from said plate to vary the lumped capacitance of said circuits. v

8. A. push-pull amplifier device comprising a pair of half-wave loop members, at the ends of one of which areelongated cathodes and at the ends of the other of which are elongated anodes, structure supporting said loop members rwith their corresponding ends in spaced alignment, a conductive plate disposed between said spaced ends of the loop members and having a pair of elongated grid slots `each aligned with one of said cathodes and the corresponding anode, and an evacuated housing including a tubular conductive member enclosing said loop members and engaging said plate.

9. A push-pull amplifier device comprising a pair of half-Wave loop members, at the ends of one of which are elongated cathodes and at the ends of the other of which are elongated anodes, structures extending from potential node points of said loop members and supporting them with their corresponding ends in spaced alignment, a conductive plate disposed between said spaced ends and having elongated grid slots respectively aligned with the pairs of said spaced ends, and a cathode-heater circuit including at least one conductor within the supporting structure for the cathode loop member.

10. A push-pull amplifier device comprising a pair of half-wave loop members, at the ends of one of which are elongated cathodes and at the ends of the other of which are elongated anodes, structures extending from potential node points of said loop members' and supportingthem with their corresponding ends in spaced alignment, and a conductive plate disposed between said spaced ends and having elongated grid slots respectively aligned with the pairs of said spaced ends, at least one of said loop members and its supporting structure having passages for circulation of cooling liquid therethrough.

11. In an electronic tube, a member in the form of a half-wave loop whose ends provide electrodes of the tube, structure supporting said member at a potential node point and extending externally of the tube, and means in said structure and member providing' passages for flow of liquid through said structure and said member for cooling of said electrodes.

12. In an electronic tube, a hollow half-Wave member whose ends provide cathodes of the tube, electrical heating means within said loop member, hollow structure supporting said member at a potential node point and extending externally of the tube, and at least one conductor extending through said structure and said member' for connection to said heating means.

13. An electronic discharge device comprising a tubular conductive envelope member, a pair ofA electrode supporting members extending through said envelope member frem opposite sides thereof, a pair of half-wave loops each supported at a potential node point by one of said structures and with its ends spaced from and aligned with the ends of the other loop, the ends of one of said loops providing cathodes and the ends of the other of said loops providing anodes, and a slotted grid plate supported by said envelope member between said loop members.

14. An electronic discharge device comprising a tubular conductive envelope member, a pair of electrode supporting members extending through said envelope member from opposite sides thereof, a pair of half-wave loops each supported at a potential node point by one of said structures and with its ends spaced from and aligned with the ends of the other loop, the ends of one of said loops providing` cathodes and the ends of the other of said loops providing anodes, a slotted grid plate supported by said envelope member between said loop members, and a pair of deformable insulating seals through which supporting members extend for adjustment or" the spacing between said grid plate and the ends of said loop members.

15. An electronic discharge device incorporating push-pull anode and cathode circuits comprising a pair of cathodes, a half-'wave loop hav- 8 ing said cathode at opposite ends thereof, a pair of anodes, a half-Wave loop having said anodes at opposite ends thereof, and a gridplate disposed between said loops and having a pair of grids respectively disposed between one of said cathodes and one .of said anodes.

16. An electronic discharge device incorporating push-pull anode and cathode circuits com; prising a pair of cathodes, a half-wave troughshaped member having said cathodes at opposite edges thereof, a pair of anodes, a half-wave trough-shaped member having said anodes at opposite ends thereof, a grid plate disposed between said loop members and having a pair of grids respectively disposed between .one of said cathodes and one of ksaid anodes, supporting structures for said loop members extending lfrom potential node points thereof, and means mounting said supporting structures in said device, said means .being deformable for variationv of the ca.- pacitances between said plate and said ends of the loop members.

17. An electronic discharge device incorporar,.- ing push-pull anode and Ycathoide circuits comprising a pair of cathodes, a half-wave troughshaped member having said cathodes at opposite edges thereof, a pair of anodes, a half-.wave trough-shaped member having saidanodes at opposite ends thereof, a grid plate `disposed between said loop members and having a pair of grids respectively disposed between one of said cathodes and one of said anodes, supporting structures respectively extending from potential node points of said members, and means mounting said supporting structures in said device, said means being deformable for tuning of said circuits, said members and Supporting structures having passages for ow of cooling liquid 4and for cathode-heater conductors.

RUSSELL R. LAW.

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

UNITED STATES PATENTS Number Name Date 1,978,021 Hollmann Oct. 23, 19.34 2,009,369 Hansell July 23, 1935 2,034,433 Heintz Mar. 1.7, 1936 2,107,387 Potter Feb. 8, 1938 2,122,538 Potter July 5, 1938 2,153,728 Southworth Apr. 11, 1939 2,368,031 Llewellyn Jan. 23, 19.45

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