US2207846A

US2207846A - Electronic discharge device

Info

Publication number: US2207846A
Application number: US216824A
Authority: US
Inventors: Wolff Irving
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1938-06-30
Filing date: 1938-06-30
Publication date: 1940-07-16
Anticipated expiration: 1957-07-16

Description

.2 Sheets-Sheet l l. WOLFF ELECTRONIC DISCHARGE DEVICE Filed Jurie so, 1938 July 16, 1940.

fla.1. 1

l/EHTER INIW ZSnnentor Wolff Gttorneg Jufiy 16, 1940. Q 2,207,846

ELECTRONIC DISCHARGE DEVICE Filed June 30, 1938 2 Sheets-Sheet 2 &

Zinnefitor Irving Wolff (Ittorneg Patented July 16, 1 .4.

ELECTRONIC DIS of Dela 7 Application June 3%, 1938, Serial No. 218,824

I which this invention is an improvement.

To provide an understanding of the operation of my invention as an oscillator and as an amplifier, it is necessary to understand several fundamental principles.

Figure 1 illustrates-a basic circuit which is shown for thepurpose of facilitating explanation of these principles. A source of electrons is represented by a cathode I. An anode is located as shown at 3. The anode is given a suitable positive potential by means of a battery 5. The dash lines I represent a perforated mesh cage or enclosed space which is made to have a varying potential with respect to the cathode by means of a high frequency oscillator 9. The cathode, anode, and cage are enclosed within an evacuated chamber it and the cathode heated to incandescence. Assume that an electron Bis liberated from the cathode. It will be attracted by the positive anode and move along a path BB' through the cage i toward the anode.

The speed of the electron is determined by its initial velocity, by the instantaneous potential of the cage, and by the potential of the anode. The time which is required for an electron to pass 35 through the cage is therefore determined by its speed through the case and the length of the cage, indicated by dimension A. Let us suppose the length of the cage is equal to the distance traveled by theslowest electron during a half W period of the applied potential. If the potential of the cage is rapidly alternating, the speed of successive electrons will be difierent. Electrons approaching the cage will be speeded up when the cage potential becomes most positive,

and will be but little aiiected, or retarded, when v the cage potential is least positive, or negative. Since it takes longer for the slow electrons to pass through-the cage during the least positive half cycle or the cage, there will be a predominance 50 of incoming electrons, and during the most positive half cycle. due to the greatly increased velocities, outgoing electrons will predominate. The accumulation of electrons during the least positive, or negative, half cycle of the cage tends to 55 "make the cage potential still more negative. The

reduction of the number of electrons during the positive half cycle tends to make the cage potential still more positive. Thus the tendency of the flow of electrons is to aid the oscillatory voltage.

Electrons actually contribute energy to the system, and the energy so contributed can be made suflicient to-overcome circuit losses and to maintain self-oscillation without the assistance of the external alternating potential source 9. In practice, the almrnator 9 would be replaced by a. resonant circuit, and self-oscillations would be sustained.

Suppose that an alternating potential as well as a positive direct potential is applied to the 15 cage 1, whichjis constructed so that the electrons can pass through it. If the time required for an electron which enters the cage when the potential of the cage is most negative (a slow electron) to pass through the cage is exactly equal to the time required for the potential of the cage to go through a half period, then more energy will be given up by the electron during its approach to the cage than is taken back during its subsequent flight from the cage. The velocity of the electron is therefore decreased.

Electrons which enter the page when its potential is most positive pass through in a time which is somewhat less than a half period. Consequently, more energy will be gained by the elec- 80 tron in its approach to the cage than will be lost in its subsequent flight from the cage. The velocity of the electron is therefore increased.

It is to be noted that the electrons leaving the cage will be formed into groups of fast and slow electrons. The fast electrons catch up to the slow ones, and thus the electrons will pass some point along the line of flight in groups containing a mixture of slow and fast electrons. At this point there are alternations of electron density. It is this characteristic which is employed in the process of amplification. The anode is placed at the point at which this grouping effect occurs. The arrival of successive groups of electrons at the anode produces a current in the anode which varies in accordance with the electron distribution. When the device is used as an amplifier the condition of self-oscillation is not required. The voltage which is to be amplified is applied to the cage electrode.

One of the objects of this invention is to provide means for generating oscillations according to the principle outlined above.

Another object is to provide means for applying these principles. to radio frequency amplifiers.

the type described.

This invention will be better understood when considered in connection with the acompanying drawings. Its scope is-indicated by the appended claims. Similar reference numerals refer to similar parts throughout the several drawings.

Referring to the drawings,

Figure l is a schematic diagram illustrative of the principle on which this invention is based,

Figures 2 and 3 are, respectivelyg'a side elevation and plan view of circuit diagrams schematically illustrating a practical circuit and tube electrode arrangement, and

Figures 4 and 5 are an elevation and plan view, respectively, partly in section, of the preferred structural arrangement of circuit elements and tube electrodes in an oscillator of the type described.

Referring to Figs. 2 and 3, a centrally located cathode i i is indirectly heated by an internal filament it connected to a suitable source of power, which is not shown. This cathode is specially prepared so as to have its emitting area confined to a plurality of longitudinal areas It with intervening nonemitting areas. The purpose of this is to provide an electron source which can readily be formed into a plurality of divergent beams of rectangular cross section. Cathodes of this nature are described in an article by H. C. Thompson on page 1276 of the October 1936 Proceedings of the Institute of Radio Engineers.

A plurality of inner accelerating electrodes I! are concentrically spaced about the cathode in register with the nonemissive areas of the oathode. The accelerating electrodes, and all other electrodes in the tube except the cathode and anode, may conveniently take the form of small,

wires or rods positioned in parallel relation to the cathode. The inner accelerating electrodes l5 are conductively connected together at their adiacent ends and are given a positive potential with respect to the cathode by means of a battery i6 or the like.

The cage structure, which was referred to in the discussion above, is composed of an inner l1 and an outer i9 ring of electrodes, arranged concentrically with the cathode and positioned in register with the inner accelerating electrodes that is, the inner cage electrodes are radially in line with the cathode and the respective adjacent inner accelerating electrodes. The outer cage electrodes is are similarly in register with the inner electrodes. The inner and outer electrodes are spaced apart a radial distance which is determined by the frequency and is substantially equal to the distance traveled by a slow electron during one half the period of oscillation at the desired frequency.

The inner and outer cage electrodes ii and is are connected in two groups, each enclosing a space which is defined by the rotation about the cathode of an inner and an adjacent outer cage electrode through an angle less than 180, as

- shown in Fig. 3. A; push-pull arrangement is thus obtained. A two-wire transmission line oscillatory circuit 2t, 23, terminates eta convenient point on each group of cage electrodes.

It may be desirable to use a further set of accelerating electrodes outside of the cage. The electrodes are shown concentrically arranged about the cathode in register with the inner electrodes, and electrically connected to them.

A cylindrical anode 21 surrounds the entire electrode assembly. The anode is made positive with respect to the cathode by means of a battery 29, or the like. The anode potential may be less than the accelerating electrode potential to con serve power. The outer end of the transmission line 2|, 23 is terminated in an antenna 3!. The mid-point of the antenna is connected through a choke coil 33 and a battery 35 to ground. The cathodeis also grounded.

The operation of this device is in accordance with the principles outlined above. The electrons from the cathode are formed into a plurality of wedge-shaped beams, which pass between, but do not touch, adjacent electrodes, and travel from the cathode to the anode. Energy is given up to the four electrodes which constitute each cage, in the manner described above. Oscillation is main-=- tained by this energy at the frequency of the tuned circuit represented by the transmission line 2|, 23. It is to be noted that this oscillatory circult is the equivalent of the alternator 9 illustrated in Fig. 1.

The number of electrodes of each type is not critical, but shouldpreferably be as large as is consistent with mechanical and electrical design considerations. If the number is large, the angle of divergence of the beam is small, and the regions of difierent potential are sharply defined. Too great a number of electrodes will reduce the current capacity .of the tube by restricting the size of the beams. If the number is small, the angle of divergence of the electron beam is large and the cage electrodes must be more widely separated, and are therefore only effective with respect to electrons on the edge of the beam. This tends to reduce the efliciency.

A preferred embodiment of my invention is illustrated in Figs. 4 and 5. Concentric line oscillatory circuits are utilized in the cage circuit and in the anode circuit. The arrangement shown in Figs. 4 and 5 makes possible a practical construction which eliminates earlier diiilculties caused by the. high electrode capacity and long leads required to connect the elements to the necessary oscillatory circuits. Amplifiers and oscillators of theelectron transit time class are inherently limitedto ultra high frequencies. Long connections between elements must therefore be avoided, for the inductance represented by the leads may pre vent the tuned circuits from resonating at a fre= quency comparable to the transit time of the elec-' tron through the cage.

High power output also demands the full use of available electron energy. A, small pencil-like beam cannot deliver the power that can be obtained from the plurality of beams of the type which have been provided in my invention.

Referring to Figs. 4 and 5 the tube elements are contained within an evacuated space which is defined by the enlargeal section 31 terminating the inner conductor 39 of the anode resonant concentric line H. nates in an enlarged portion 13 which encloses the inner section 31. A sealing disc 48 is placed at the end of the inner conductor 39, and a seabing cup is placed so as to close the extremity of the cylindrical section 31. This sealing cup is of insulating material, and is sealed to the cylinder 3i and to the various leads which extend through it. within the evacuated chamber there The outer conductor ll termiis a centrally located cathode II to that described in connection with Figs. 2 and 3. The remaining electrodes comprise a plurality of focusing 49, inner accelerating 5|, inner cage 53, outer cage 55, and outer accelerating 51 electrodes which are all concentrically located about the cathode and arranged in the order named on radial lines extending out from the cathode. These electrodes are arranged in register with the nonemissive spaces of the cathode in the manner explained above in connection with Figs. 2 and 3. Additional focusing electrodes 49 have been added to the device illustrated in the preceding figures, however, one of which is located between the cathode and each inner accelerating electrode. Their purpose is to provide a better focus for the beams. They are negatively biased by means of a battery Stand therefore repel the electrons and cause them to segregate into narrow beams.

The focusing electrodes 89 are connected at one end by an annular ring 59. The acceleratin electrodes 5| and 51 are all mounted on and connected together by an annular ring iii. A third annular ring 63 is used to mount and connect the

cage electrodes

53 and 55. A perforated mica disc 65 is used to hold the free ends of the various electrodes in position.

A second or cage circuit concentric transmission line 51 is provided, the outer conductor 69 of which is connected to the outer conductor 13, which is a continuation of the anode circuit concentric line M and which encloses the entire tube structure. The inner conductor E5 of the cage concentric line is connected to the inner and

outer cage electrodes

53 and 55. A fixed cage biasing potential is applied by a battery 60 through a connection made to the inner conductor 15 at a voltage node 62.

The length of the concentric lines 61 and M is adjusted so that the line resonates at the desired frequency. Anode potential is obtained from a battery 52 through a connection I9 which is made at a voltage node on the inner conductor 39.

The filament leads BI and 83, the cathode II, the focusing electrodes 49, and the accelerating electrodes 5i and 51 are all at radio frequency ground potential. The accelerating electrodes 5| and 51 are connected directly to the outer shell it, but the other elements cannot be so easily grounded. It is necessary to ground effectively the filament, cathode and focusing elements. This is most conveniently accomplished by resonating their connecting leads. The leads from these elements are brought out through the concentric conductors, through suitable insulators 8%, and into

hollow tubes

81, 89, 9i and 93, which are used to tune their respective leads to resonance. Connections to the biasing battery so, filament energizing source, or ground, are then made at points of voltage node, which are approximately a quarter wave length from the end of the respective resonant circuits, as shown at as, M, es, mi.

When this device is utilized as an amplifier, the electrode potentials are adjusted so that oscillation does not take place. The input voltage which is to be amplified is introduced into the cage resonant circuit 51! by any convenient means, For example, a conductor ll may be coupled to the inner conductor E5 of the resonant circuit, The voltage to be amplified is therefore impressed on the

cage electrodes

53 and 55.

The'device illustrated in Figs. 4 and 5 is not push-pull connected because the outer conductor of a concentric transmission line is conveniently kept at ground radio frequency potential. In

- order to properly bias the accelerating electrodes 5| and 51, a battery 58 is connected between the outer shell I3 and ground. Alternatively, the shell 13 may be directly grounded and the cathode operated at a high negative potential.

The anode is connected to a resonant circuit 4!. Consequently, the current variations in the anode, due to the electron grouping which is caused by the applied voltage, are resolved by the resonant circuit into amplified voltage variations. The voltage variations so obtained are coupled to a utilization circuit by means of a coupled output conductor I05.

One important feature of the present arrangement is that a high control circuit impedanceis maintained. The arrangement of the tube electrodes is such that the cage electrodes are shielded from the electron beam by the accelerating and focusing electrodes. Consequently control is exerted on the electron stream without appreciable power loss due to absorption of electrons from the stream by the cage electrodes. The shielding of the cage electrodes also makes" possible a high impedance input circuit when the'device is used as an amplifier for ultra high frequencies.

Another important advantage of the present arrangement is the development of more power than has heretofore been possible. area of the electron beam, as well as the large number of separate beams which are employed, contributes to this result.

I claim as my invention:

1. An ultra high frequency oscillator which comprises a cylindrical. cathode having a pinrality of longitudinal electron emissive areas and intervening non-emissive areas; means for energizing said cathode; a plurality of inner accelerating electrodes parallel to and concentrically arranged about said cathode, in register with said non-emissive areas; a plurality of inner and outer cage electrodes, parallel to and concentrically arranged about sald cathode, in register with said inner accelerating electrodes, said outer cage electrodes being radially spaced from said inner cage electrodes; means for connecting adjacent ends of said inner and outer cage electrodes to form two separate groups each enclosing a region defined by the angular rotation about the cathode of an inner and an adjacent outer cage electrode. said angle of rotation being less than 180; a plurality of outer accelerating electrodes concentrically arranged about said cathode, in register with and adjacent to respective outer cage electrodes; a cylindrical anode enclosing said outer accelerating electrodes; means for applying direct current potentials to said accelerating and said anode electrodes; a resonant circuit connected between said separate groups of cage electrodes; means for applying a direct current potential to said groups of cage electrodes; means for obtaining energy from said electrons whereby oscillatory currents are induced in said oscillatory circuit; and means for utilizing said oscillatory currents.

2. An oscillator of the character described in claim 1 in which said means for obtaining energy from said electrons includes fixing the radial spacing between said inner and outer cage electrodes and controlling the electron velocity so that the transit time required for an electron to pass through the region bounded by said cage electrodes is substantially one-half the period of oscillation of said oscillatory circuit.

The large dill 3. An oscillator of the character described in claim 1 which is further characterized by a plurality of negatively biased focusing electrodes, parallel to and concentrically positioned about said cathode, in register with said cathode non= emissive surfaces and between said cathode and said inner accelerating electrodes.

4. A device of the characterdescrlbed which includes a cathode, a plurality of inner and outer cage electrodes parallel to and concentrically positioned about said cathode; means connecting adjacent ends of said cage electrodes; a cylindrical anode enclosing said cage electrodes; an anode oscillatory circuit connected between said anode and said cathode; a cage oscillatory circuit connected between said cage electrodes and said cathode; andmeans for applying biasing potentials to said anode and cage, electrodes.

5. A device of the character described which includes in combination a cathode; a plurality of inner and outer cage electrodes parallel to and concentrically arranged about said cathode; means connecting adjacent ends of said cage electrodes; a cylindrical anode enclosing said cage electrodes; an anode concentric line oscillatory circuit connected between said anode and said cathode; a cage concentric line oscillatory circuit connected between said cage electrodes 5g spacing between said cage electrodes whereby the transit time of an electron through said cage electrode region is equal to one-half the period of oscillation of said oscillatory circuits.

6. In an ultra high frequency amplifier, a. cathode having longitudinal electron emissive regions and alternate non-emissive regions; a plurality of focusing electrodes parallel to and concentrically arranged about said cathode, in register with said non-emisslve cathode regions; means for applying a biasing potential to said focusing electrodes; a plurality of inner accelerating, inner cage, outer cage, and outer accelerating electrodes parallel to said cathode and arranged in the order named on radial lines extending from said cathode, and in register with said focusing electrodes; means connecting ad- 'jacent ends of said inner and outer cage electrodes; means connecting adjacent ends of said inner and outer accelerating electrodesra cage concentric line resonant circuit having an inner and an outer tubular conductor, said inner conductor terminating at and connected to the base of said cage electrodes; a cylindrical anode surrounding saicl-outer accelerating electrodes; an anode concentric line resonant circuit having an inner and an outer tubular conductor, said anode electrode being an extension of said inner con-= ductor; a cylindrical member connecting the outer conductors of said concentric lines; means for applying biasing potentials to said accelerating, cage, and anode electrodes; and means for efiectively grounding said cathode, focusing and accelerating electrodes with'respect to radio frequency voltages whereby a plurality of electron beams of large cross-sectional area are formed between said cathode and said anode; means for trodes whereby said electrons are accelerated or retarded so as to form successive groups which induce an oscillatorycurrent in said anode oscillatory circuit; and means for deriving anamplifled voltage therefrom.

7. An electron discharge device for operation at an ultra high frequency comprising a central cathode; a plurality of mutually parallel inner and outer cage electrodes arranged in pairs in radial planes which intersect along the axis of said cathode, the radial distance between the inner and outer cage electrodes being substantially equal to the distance traversed byan electron in one half the period of said ultra high frequency; an accelerating electrode adjacent each inner electrode, parallel thereto, and lying between. said cathode and said inner cage electrode in the radial plane which includes said adjacent inner cage electrode; and a cylindrical anode electrode enclosing said cathode, accelcrating and cage electrodes. 4

8. Anelectric discharge device for operation at an ultra high frequency comprising a central cathode electrode; a plurality of mutually parallel inner and outer interconnected cage electrodes arranged in pairs in radial planes which intersect along the axis of said cathode, the radial distance between the inner and outer cage electrodes being substantially equal to the dis-- tance traversed by an, electron in one half the period of said ultra high frequency; an accelcrating electrode adjacent each inner electrode, parallel thereto, and lying between said cathode and said inner cage electrode in the radial plane which includes said adjacent inner cage electrode; and a cylindrical anode electrode enclosing said cathode, accelerating and cage electrodes.

9. An electric discharge device for operation at an ultra high frequency comprising a central cylindrical cathode having electron-emitting regions confined to a plurality of longitudinal areas and intervening non-emitting areas; a plurality of mutually parallel cage electrodes arranged in pairs in radial planes which intersect along the axis of said cathode and pass through said nonemitting areas; theradial distance between the inner and outer cage electrodes being substantially equal to the distance traversed by an electron in one half the period of said ultra high frequency; an accelerating electrode adjacent each inner electrode, parallel thereto, and lying between said cathode and said inner cage electrode in the radial plane which includes said adjacent inner cage electrode; and a cylindrical anode electrode enclosing said cathode, accelerating and cage electrodes.

10. An electric discharge device for operation at an ultra high frequency comprising a central cylindrical cathode having electron-emitting regions confined to a plurality of longitudinal areas and intervening non-emitting areas; a plurality of mutually parallel cage electrodes arranged in pairs in radial planes which intersect along the axis of said cathode and pass through said nonemitting areas; the radial distance between the inner and outer cage electrodes being substantially equal to one half the period 01 said ultra high frequency: a cylindrical anode electrode enclosing said cathode and cage electrode; inner and outer accelerating electrodes located between said inner cage electrodes and said cathode and said outer cage electrodes and said anode, respec- 'tively,,and lying in the same plane. applying an oscillatory voltage .to said cage elec- 11. An electric discharge device fortoperation- ;at an ultra high frequency comprising a cylindrlcal cathode having electron-emitting regions confined to a plurality of longitudinal areas separated by intervening nonemitting areas; a plu.

ultra high frequency; a plurality of outer accelerating electrodes concentrically disposed about said cathode, in register with said outer cage "electrodes, and radially spaced therefrom; and

a cylindrical anode electrode enclosing all of said electrodes.

12. in a device of the character described in claim 11, means connecting all of said accelerating electrodes, and means connecting said inner and outer cage electrodes in two symmetrical 10 groups.

IRVING WOLFE.