US2554134A

US2554134A - Electron tube for ultra high frequency

Info

Publication number: US2554134A
Application number: US700593A
Authority: US
Inventors: Winfield G Wagener
Original assignee: Individual
Current assignee: Individual
Priority date: 1946-10-01
Filing date: 1946-10-01
Publication date: 1951-05-22
Anticipated expiration: 1968-05-22

Description

May 22, 1951 I w. G. WAGENER ELECTRON TUBE FOR ULTRA HIGH FREQUENCY 2 Sheets-Sheet l.

Filed Oct. 1, 1946 IN VEIV TOR. VV/n field 6. Wagener BY 62% A 7'7'ORNE V y 1951 w. G. WAGENER 2,554,134

ELECTRON TUBE FOR ULTRA HIGH FREQUENCY Filed 001;. l, 1946 2 Sheets-Sheet 2 FJJE 4= I N VEN TOR. W/n fie l0 6. Wagener Patented May 22, 1951 ELECTRON TUBE FOR ULTRA HIGH FREQUENCY Winfield G. Wagener, Palo Alto, Calif. Application October 1, 1946, Serial No. 700,593

This invention relates generally to electronic apparatus suitable for use in various electrical systems and adapted in particular for the amplification of electrical pulses. More specifically it relates to electron tubes of the beam deflection type and to apparatus making use of the same.

The conventional design of beam deflection tube makes use of a cathode for generating a beam of electrons which is made to flow past a deflecting electrode or electrodes. Upon application of controlling potentials to the deflecting electrodes the beam is shifted laterally between collecting electrodes, whereby it is possible to secure a valving action with amplification of current variations. In the past such beam deflection tubes have not been commercially important due to their many inherent limitations, and particularly because for many applications other types of conventional vacuum tubes are more satisfactory. It is well recognized however that for many types of service conventional tubes give relatively poor performance, or may fail entirely in securing the results desired. For example, at frequencies above 300 megacycles the efliciency, power gain and circuit structures of conventional negative grid vacuum tubes become relatively poor. Because of the poor performance of such conventional tubes other types of electron devices have been used in ultra high frequency systems, including the Klystron, magnetron, and special triodes or tetrodes of the lighthouse type. The Klystron is a relatively complicated device, and its operation is critical with respect to applied potentials. It will not operate on the low frequencies and its efiiciency is relatively low, being of the order of about twentyfive percent. A magnetron cannot be used as an amplifier, and it cannot usually be adjusted over a wide range of operating frequencies. Special triodes or tetrodes of the lighthouse type have poor efliciency for frequencies inexcess of 600 megacycles and are limited as to power gain and power .output.

It is an object of the present invention to provide an improved electron tube of the beam deflection type which in general overcomes the limitations of prior proposed beam deflection tubes, and which will enable the application of such tubes to a wide variety of services, including the amplification of ultra high frequencies.

A further object of the invention is to provide an electron tube of the above character which can be used for the amplification of frequencies over a wide frequency range, including frequen- 9 Claims. (Cl. 250-275) an electron tube of the above character which edge sealed to the glass wall l3, and serves to when used for the amplification of ultra high frequencies will afford a relatively high efliciency, with a relatively high amplification power gain.

Another object of the invention is to provide an electron tube of the above character which will afford relatively low inter-electrode capac' ity especially between the input and output circuits for all frequencies of operation, including ultra high frequencies.

Another object of the invention is to provide an electron tube suitable for amplification of ultra high frequencies and which can be constructed in a wide variety of sizes to suit power output requirements.

Another object of the invention is to provide an electron tube having low input and low output capacities so that the stored circulating radio frequency energy in the input and output circuits can be kept to a minimum.

Another object of the invention is to provide ultra high frequency apparatus including an electron tube of the beam deflection type which is particularly adapted for use with conventional high frequency transmission lines.

Further objects of the invention will appear from the following description in which the preferred embodiments have been set forth in detail in conjunction with the accompanying drawing.

Referring to the drawing:

Figure 1 is a side elevational view in section illustrating one form of my electron tube,

Figure 2 is a circuit diagram for the tube of Figure 1,

Figure 3 illustrates ultra high frequency apparatus making use of my invention,

Figure 4 is a sectional detail taken on the line 4-4 of Figure 3.

Referring to Figure 1 the electron tube illustrated consists of an evacuated enclosure or envelope designated generally at II]. A part of the enclosure is formed by the cylindrical metal part II, which has a flared end portion I2 sealed to the glass part l3. The other end portion 14 of the metal cylinder H is sealed to the end glass wall [6. Suitable circumferentially spaced fins l1 are shown attached to the cylindrical member II to facilitate dissipation of heat. A cupped or bell shaped metal header I8 has a peripheral carry a plurality of electrode supports. A support tube [9 extends through the center of header [8, and axially within this tube there is a support conductor 2!. An insulating seal 22 is provided between conductors l9 and 2|.

Within the evacuated envelope l there is an annularly shaped cathode structure 23, which is formed to provide an electron emitting surface 24. The cathode is heated by a filament 25 or other suitable means such as will be understood by those skilled in the art. It is desirable that the surface 24, in addition to being annularly contoured, be concave as illustrated to facilitate a focusing action of the beam as will be presently explained.

The cathode structure may include the inner and outer cylindrical shaped members 26 and 2]. Member 2! is attached at its base to a cylindrical shaped member 28, which has anend flange 2,9 attached to support conductors 3!. These conductors extend through seals 32 provided in the metal header l8. For a purpose to be presently explained it is desirable that the inner member 26 of the cathode structure be attached to the enerally cylindrical shaped member 33, which is concentric with but spaced outwardly from the adjacent portion of the tube is.

In conjunction with the cathode, beam focusing electrodes are provided to form an electron beam substantially in the form of a hollow cone. These electrodes are designated by numerals 36, 3], 38 and 39. Electrode 35 is the end of the cylindrical shaped sleeve 33 attached to the innor cathode part 26. Electrode 3'! is a conical shaped metal collar attached to the inner end of the Support tube [9. Electrode 38 is the end portion of the sleeve 23. Electrode 39 is the end portion of a conical shaped member 4!, which can be supported by spaced radial struts 49. Both

electrodes

36 and 33 are conductively con nected to and therefore operate at the .same potential as the cathode. Both .electrodes 3! and 39 are connected with tube :9.

Attached to the inner end of the support conductor 2| is a circularly contoured metal disc 42 which will be called the grid and which is disposed generaly within the electron beam. Adjacent the grid 42 there is a metal grid shield 43 which likewise has a circular periphery, and which is disposed in axial alignment with the other elements of the tube, including the grid, tube I9, and the cathode. This grid can be supported by spaced radially extending struts 45. The conical shaped member 4| is provided with an inner flange 44 which is evenly spaced from the circular periphery of the grid 42, to thereby form an annular space or gap through which the electron beam flows.

The electron beam is directed toward a plate or collector electrode 4% disposed in alignment with the axis of the cathode-grid structure. It is desirable that the end face 4'! of this electrode, upon which the electrons are received, be relatively flat and at right angles to the beam axis. Adjacent the face 41 and likewise transverse to the axis of the beam, there is a metal electrode 48 which serves as an electrostatic shield. The outer periphery of this element is shown attached to the metal cylinder ll. Its central portion is provided with a circularly contoured opening 49 through which electrons may pass. It is desirable to provide the shield with metal grid bars or w res extending across the opening, in order to more effectively isolate the collecting electrode and the main field of the tube. It will be noted that the diameter of the opening 43 is somewhat 4 less than the diameter of the collecting electrode 45. The collecting electrode 46 can be mounted in any suitable manner, as by sealing the same to a cylindrical metal sleeve 52, which in turn is sealed to the glass wall [6.

The interior of the envelope is evacuated to a relatively high degree according to methods customarily used in the manufacture of high vacuum electron tubes.

The manner in which the tube of Figure 1 can be used for the amplification of electrical pulses can best be understood after a description of "Figure 2, where the several elements of the tube are illustrated diagrammatically. Batteries 53 and 54 represent suitable sources of potential. Conductor 56 connects the negative side of battery 53 with the cathode 24 and the focusing electrodes $6, 38. The positive grounded side of this battery is connected by conductor 51 to the focusing

electrodes

31, 39, and also to the deflecting electrode 44 and the shield 43. A simple resonant circuit 58 is provided for the input or control .circuit and consists for example of an inductance 59 shunted by condenser 6 l. One side of this resonant circuit is connected by condoctor 62 to the grid or deflecting electrode 42, and the other side connects to the ground. An input coil 65 is shown coupled to the inductance 59.

The plate supply battery 54 is shown having its negative side grounded and its positive side connected to the collecting electrode 46 through the circuit 64. The output of the tube is provided with a resonant circuit 64 consisting for example of the inductance 6G shunted by condenser 6]. Conductor 68 connects one side of this resonant circuit to the collectin electrode 4.6, and the other side is shown connected by conductor 69 to the positive and of the battery 54. The electro-static shield 48 is likewise shown grounded to maintain the same at a constant potential. Coil H is shown coupled to the inductance 66 and represents a suitable output or load circuit. Both

circuits

58 and 64 are tuned to the frequency of operation desired.

By virtue of the concave shaping of the oathode surface, and also because of the action of the focusing

electrodes

36, 31, 38 and 39, an electron beam 12 is formed which is substantially in the form of a hollow cone. Assuming that the grid 42 is of the same potential as the surrounding deflecting electrode 44, the focusing of the beam is such that all or the major part of the electron beam is intercepted by the electrostatic shield 48 over an area surrounding and extending beyond the opening 49. Thus no electrons or only a minor portion of the electrons of the beam are collected by the face 41 of the collecting electrode 46. Upon changing the potential grid 42 relative to the surrounding electrode 44, the direction of the beam is correspondingly varied. Thus considering the cross sectional area of the beam in the plane of the collecting electrode, the diameter of the annular cross sectional area is varied symmetrically with respect to the longitudinal axis of the beam. Assuming that the potential change upon the grid 42 is such as to decrease the diameter of the beam cross sectional area at the collecting electrode, then an increased quantity of electrons are collected by the electrode 46, and the potential of this electrode changed accordingly. It will be seen that by application of varying potentials to the grid 42 a symmetrical deflection of the beam will result and that the electrons collected by electrode 46 will vary accordingly. Under ideal conditions the electrons collected by electrode 46 may vary from zero or near zero to substantially the maximum flow of the beam. In the particular circuit diagram illustrated in Figure 2, it is assumed that sine wave variations of voltage of a regular frequency are applied to the input circuit, and that current of the same frequency is absorbed in the output. It will be evident however that my tube has application for amplification of mixed frequencies, frequency bands or frequency multiplication, provided the characteristics of the input and output circuits are modified accordingly.

Particular features of the electron tube described above can be outlined as follows: The collector electrode 46 is electrostatically isolated by the

shields

48 and 43 from the grid 42 and other elements of the tube. Therefore my tube can be used in various types of circuits and net works with a minimum amount of capacity coupling between the input and output circuits. It

is well known that such inter-electrode capacity is undesirable for many types of service, including particularly amplification of ultra high frequencies. The distance between the collecting electrode 46 and the grid 42 is not a factor or limitation in operation of the tube. This is because the transit time in this space is not important and because the electro-static shield 48 determines the final velocity of the electrons toward the collecting electrode. The positioning of the shield 48 with respect to the collecting electrode should be such that the time of flight of the electron across the space between the shield and the collector, is relatively small compared to the time period of the alternating cycle. Preferably the spacing is not substantially greater than one-quarter of a cycle for the highest frequency to be amplified.

' The use of a beam which is deflected symmetrically with respect to its longitudinal axis facilitates tube construction and design, and in addition it enables a maximum concentration of electrons upon the collecting electrode. The grid shield 43 is desirable in that it serves to isolate the varying potentials applied to the grid from affecting the field extending between the shield 43 and the collector 46.

Depending upon the characteristics of the circuits used with my tube, the frequency of operation may vary from the audio range to ultra high frequencies in the order of 3000 megacycles or higher. With given circuit connections it is possible to effect adjustment of the frequency of operation without being confined to certain critical frequencies.

Relatively high amplification power gain is made possible with my tube, due to its inherent characteristics, including particularly the use of an electron beam which is deflected symmetrically with respect to its longitudinal axis. As previously explained such a beam makes possible a relatively high concentration of electrons for collection by the electrode 46. High power amplification is made practical because of the low coupling between the output and input circuits. No alternating current is returned to the cathode as in tubes with amplitude modulation of the cathode space current. Such currents cause input energy to be fed into the output circuit when there is an impedance in the cathode leads, which is always the case when operating such tubes at ultra high frequencies.

The efficiency of my tube is relatively high for all frequencies of operation, including ultra high frequencies. Thus for frequencies well above 100 megacycles, where the efiiciency of a Klystron is of the order of 20 to 25%, my tube is capable of efliciencies of the order of 60% or better. In addition to high efficiency my tube can be constructed in a variety of sizes whereby relatively high power outputs can be had for any desired frequency of operation. v a

It will be understood that my electron tube has useful application for purposes other than amplification of current pulses. For example it is possible, with application of suitable feedback between the output and input circuits, to operate my tube for the generation of alternating current. In addition tubes of the smaller sizes can be used with signal receiving equipment, including use as an amplifier of received signals, as a detector-mixer, and as an audio amplifier.

Figure 3 illustrates equipment incorporating the electron tube of Figure 1, and particularly adapted. for the application of ultra high frequencies of the order of 306 megacycles or more. A conducting tube 16 extends axially from the grid terminal end of the tube, and is provided with contacting fingers or brushes ll for making electrical connection with the tube l9. The grid support conductor 2| is conductively connected to a conductor 15 which extends axially of the tube 16. Within the tube 16 there is a section 18 formed of suitable conductive material, and which is annularly contoured to fit within the tube 16. The annular passage 19 between section l8 and the central conductor F5 is tapered as illustrated. This forms in efiect an impedance matching section for a purpose to be presently described. Tapered section 18 together with the adjacent portion of tube 16 can be provided with slots (Figure 4) whereby it can be deformed to adjust the spacing i9.

At the plate end of the electron tube a conducting tube iil is provided which at its one end has brushes or spring contact elements 82 making electrical connection with the cylindrical member H. A central conductor 83 within tube BI is conductively connected to the exterior end of the plate or collecting electrode 46. An impedance matching section 84 is provided which has a tapered annular spacing 85 between it and the conductor 83, and which is deformable in the same manner as the section 78 previously described.

Tube 16 together with conductor 75 form a coaxial transmission line leading from a suitable source of radio frequency power, such as a suitable oscillation generator, frequency multiplier or the like. The longitudinal positioning of the impedance matching section 18 is adjusted whereby the circuit designated generally at 85, consisting of the tube l9, the central conductor 2|, and that portion of tube l6 extending between tube l9 and the matching section I8, is resonant to the exciting frequency. At thehighest frequencies the parts are preferably adjusted whereby the circuit 85 is a three-quarter wave resonant circuit. The impedance matching section it serves to impose a coupling and matching impedance between the input part of the coaxial transmission line, and the circuit 85. The degree of coupling afforded can be varied by adjusting the width of the spacing 19. It will be noted that a part of the resonant circuit 85 is within the evacuated tube.

At the plate end of the tube the matching section 64 is adjusted to provide a coaxial type of resonant circuit 81. Here it is usually desirable that the dimensions be such that a quarter wave resonant circuit is provided. By adjusting the spacing 86 the loading of the resonant circuit 8'5 is varied. Here again the resonant circuit 87 is formed partly within and partly exterior of the evacuated enclosure.

With the apparatus of Figure 3, suitable potentials must be applied to the various electrodes in the same general manner as described with reference to Figure 2. Thus conductor 16 is normally grounded together with the conductor 3! of the ouput transmission line, terminals 3: supporting the cathode are connected to the negative potential, and conductor 83 of the output transmission line connected to a source of posi tive plate potential.

With the apparatus of Figure 3 oscillatory electrical power of a frequency of say 3000 megacycles or higher can be amplified with an amplification power gain of or more, and with an efiiciency of the order of 60% or greater. Intercoupling capacity between the input and output circuits is minimized because of the action of the plate shield 48 and grid shield 43, as previously explained.

I claim:

1. In an electron tube, an evacuated envelope, means within the envelope forming an electron beam having circular cross-sectional symmetry about a longitudinal axis, a collecting electrode within the envelope serving to collect electrons from the beam, a conductor extending into the envelope axially of the beam, a beam deflecting control grid attached to the inner end of said conductor, and a tubular conductor extending into the tube and coaxially surrounding the first named conductor, the inner end of said tubular conductor extending to a region adjacent to said control grid.

2. In an electron tube, an evacuated envelope, an annular cathode within the envelope forming an electron beam having circular cross-sectional symmetry about a longitudinal axis, a collecting electrode within the envelope serving to collect electrons from the beam, a conductor extending into the envelope substantially axially of the cathode and the beam, a beam deflecting control grid attached to the inner end of said conductor, and a tubular conductor extending into the envelope and coaxially surrounding the first named conductor, said tubular conductor extending through said cathode and the inner end of said tubular conductor terminating in a region adjacent to said control grid.

3. In an electron tube, an evacuated envelope, means within the envelope forming an electron beam having circular cross-sectional symmetry about a longitudinal axis, a collecting electrode within the envelope and adapted to receive electrons from the beam, a substantially disc-like control grid within the envelope concentric with said axis and extending laterally of the same, a conductor extending into the envelope and having its inner end attached to said deflecting electrode, and an annular grid shield surrounding said beam and spaced from the periphery of said grid by an annular gap through which said electron beam is caused to pass, the dimensioning of said gap in a direction longitudinally of the axis of the beam being a minor fraction of the distance between said control grid and the collecting electrode,

4. A tube as in claim 3 together with an additional metal grid shield disposed concentric with the axis of the beam, in relatively close proximity with that side of the control grid which faces the collecting electrode, and having a diameter less than the diameter of the control grid.

5. In an electron tube, an evacuated envelope, means within the envelope forming an electron beam having circular cross-sectional symmetry about a longitudinal axis, a conductor extending into one end of the envelope and aligned with said axis, the inner end of said conductor forming a collecting electrode, a sleeve of conductive material forming a part of the envelope and concentric with the axis of the beam, a control grid arranged to act upon the beam and spaced longitudinally a substantial distance from the collecting electrode, said sleeve having a length in the direction of the axis of the beam sufiicient to substantially embrace the collecting electrode and that part of the beam extending from the control grid to the collecting electrode, a conductive shield extending transverse to the axis of the beam and in proximity to the collecting electrode, said shield being provided with an opening for the passage of electrons to the collecting electrode,

the outer periphery of said shield being conductively connected to said sleeve, and heat dissipating means carried by the outer surface of said sleeve.

6. In an electron tube, an evacuated envelope,

. an annular cathode disposed in the tube and aligned on a longitudinal tube axis, a collecting electrode within the tube and aligned with said axis, said collecting electrode being spaced a substantial distance from the cathode, focusing means adjacent the cathode serving to focus electrons from the cathode in the form of a hollow conical-shaped beam with the larger end of the beam at the cathode and the smaller end at the collecting electrode, beam deflecting means located in said envelope and interposed between the focusing means and said collecting electrode, said last means including elements providing an annular opening for accommodating the beam, and an electrostatic shield disposed in the envelope and adjacent the collecting electrode, said shield having an opening for passage of electrons to the collecting electrode, said opening having a diameter which is a minor fraction of the effective diameter of the cathode and which is substantially smaller than the mean diameter of said annular opening, the distance in a direction longitudinally of said axis between the shield and the collecting electrode being a minor fraction of the distance between the shield and said beam deflecting means.

'7. In an electron tube, an evacuated envelope, a metal tube extending into one end of the envelope, a conductor aligned with the axis of said tube and extending into the other end of the envelope, the inner end portion of said last named conductor formin a collecting electrode, an annular cathode disposed in the envelope and surrounding said tube, said cathode being adapted to form an electron beam having circular cross-sectional symmetry about the axis of the tube, another conductor extending into the envelope through said tube and aligned with said axis, a deflecting electrode attached to the inner end of said conductor and between the cathode and the collecting electrode, a conducting sleeve forming a part of the envelope and disposed concentric with said axis, one end portion of said sleeve embracing said collecting electrode,'and the remaining portion of the sleeve embracing the space between the control grid and the collecting electrode, and an electrostatic shield in the envelope and extending transverse to the axis of the beam, said shield having its outer periphery conductively connected to said sleeve, the distance between the shield and the collecting electrode being a minor fraction of the distance between said shield and the deflecting electrode.

8. An electron tube as in claim 7 together with a second electrostatic shield disposed within the envelope and aligned with said axis, said last named shield being disposed adjacent the control electrode whereby the distance between said last named shield and the control electrode is a minor fraction of the distance between said last named shield and the collecting electrode.

9. In an electron tube, an evacuated envelope, means including a cathode in the envelope and adapted to form an electron beam having circular cross-sectional symmetry about the longitudinal axis and substantially in the form of a hollow cone, electrode means within the envelope for deflecting the beam with respect to its cross-sectional dimensioning and symmetrically with respect to said axis, electrode means within said envelope adapted to collect electrons at the smaller end of the beam responsive to WINFIELD G. WAGENER.

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

UNITED STATES PATENTS Number Name Date 2,064,469 Haeif Dec. 15, 1936 2,233,126 Haefi Feb. 25, 1941 2,233,166 Hahn Feb. 25, 1941 2,390,250 Hansell Dec. 4, 1945 2,407,274 Hartley et a1 Sept. 10, 1946 2,409,179 Anderson Oct. 15, 1946 2,409,992 Strobel Oct. 22, 1946 2,466,064 Wathen et a1. Apr. 5, 1949