US2922919A - High frequency electron discharge device - Google Patents

Description

Jan. 26, 1960 BROCK HIGH FREQUENCY ELECTRON DISCHARGE DEVICE Filed Feb. 24, 1953 2 Sheets-Sheet 1 WSW MMV,

Jan. 26, 1960 BRUCK HIGH FREQUENCY ELEcIRoN DISCHARGE DEVICE 2 Sheets-Sheet 2 Filed Feb. 24, 1953 IN VEN TOR.

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States latent 5 Ztl-22,919 Y Patented Jan. 26, 1960 i ice acts as a travelling wave tube section, having a signal 2,922,919 wave excited therein whose propagating velocity along the section is equal to the electron beam velocity pass- C ing therethrugh Lothar Brck, Ulm (Danube), Germany, assignor to Telefunken Gesellschaft fuer drahtlose Telegraphie G.m.b.H., Hannover, Germany Application February 24, 1953, Serial No. 338,499 Claims priority, application Germany February 25, 1952 13 Claims. (Cl. S15-3.6)

This invention relates to an electron discharge device for generating ultra-short frequencies, and in particular to a discharge device which comprises an electron wave tube section and a travelling wave tube section combined in one envelope.

The use of travelling wave tube for generating high power output levels is well known. It is also well known that certain intrinsic difculties exist in the design of such a tube, these difiiculties involving (l) The manufacturing of a uniform helix winding;

(2) Maintaining the helix in axial alignment;

(3) Reducing the interception of the electron beam by the helix to a minimum, particularly at very high frequencies.

The electron wave tube is equally well known and involves the use of two electron beams having different velocities which have impressed thereon, by means of suitable electromagnetic circuits, high frequency signals to be amplified. While it is true that high voltage ampliiication may be obtained with the electron wave tube, the power output from such tubes is limited while the high voltage amplification is predominant.

It is therefore an object of this invention to provide a high frequency electron discharge device which utilizes the advantageous features of the electron and the travelling wave tubes.

It is another object of this invention to provide a high frequency discharge device which may be easily manufactured.

It is yet another object of this invention to eliminate the disadvantages associated with electron and travelling Wave tubes and to utilize the best features thereof.

With the above objects in view the present invention consists mainly of an electron discharge device for generating ultra-short frequencies, comprising in combination, a vacuum tight envelope, a first and a second electron beam emitting means located in the envelope, emitting two electron beams having different velocities, collector means located in the envelope, the collector being arranged opposite to and spaced from the rst and second electron emitting means to define a common path for the electron beams, input delay line means arranged in the region of the common path of the electron beams after the same has been emitted by the electron emitting means, the input delay means adapted to be coupled to signal waves to be amplified so as to velocity modulate the electron beams, output delay line means having a pre-determined dimension, the output delay line means being arranged in the region of the path of the electron beams subsequent to and spaced from the input delay line means, so as to leave between the input and output delay line means a field free region wherein the velocity modulated electron beams are transformed to density modulated electron beams, a voltage source connected to the output delay line means, the voltage source applying such a potential to the output delay line so that the output delay line due to its predetermined dirnension and the potential applied thereto The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantage thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Fig. 1 illustrates schematically a high frequency discharge device constituting one form of the invention;

Fig. 2 illustrates a curve showing the relative amplitude versus electron volts in the output section of this high frequency discharge device; and

Fig. 3 illustrates a modification of the invention wherein two electron beams are generated, one of these beams surrounding the other.

Referring to Figure 1, a high-frequency discharge tube 21 is shown, into which is introduced through its input connector 1, 1 a signal to be amplified. The. outer conductor 1 of the input coax connector is vacuum sealed to the glass envelope 11 of the discharge)I device, the center conductor 1 of the input connector 'being connected through a vacuum seal in the envelope to the input end of the helix or delay transmission line 2. At the opposite end 7 of the delay line 2 is con# nected a matched attenuator 9 in order to prevent reflection of the input signal in the event of a mismatch. An output connector 20, 20 is vacuum sealed at its outer conductor 20 to the glass envelope 11, its inner conductor being connected through a vacuum seal in the envelope to the output end of a second helix, or a delay transmission line 5. At the opposite end 8 of the helix 5 is connected a matched attenuator 10 to prevent reflection of amplified signals from the output toward the input end of the tube. Electron streams 3 and 4 are emitted by cathodes 19A and 19B respectively. The filaments of cathodes 19A and 19B are connected to voltage source 14 and 15. Between voltage source 14 and 15 is connected a voltage source 16 in such manner that cathode 19B will be at a higher potential than cathode 19A with respect to the common return point 16a. Under these conditions the electron stream emitted by cathode 19B will have a higher velocity than the electron stream emitted by cathode 19A. Another voltage source 17 is connected at one of its terminals to the source 16 vat point 16a, which is the mid-voltage point of source 16, the other terminals of voltage source 17 being connected to the accelerating anode 19. The input side of delay transmission line 2, is connected to the accelerating anode, 19, and voltage source 17, via a radio frequency choke 12. This choke is used to prevent any high-frequency signals from reaching the D.C. voltage source. Voltage source 18 is connected in series with voltage source 17 at one terminal thereof, and at the other terminal thereof to a collector 6. The-collector 6 in turn is connected to the inner conductorv 20 of the output connector via radio frequency choke 13, thereby placing the helix or delay line 5, at the same potential as the collector 6. The voltage output of source 18 is approximately 2000 volts positive with respect to cathodes 19a and 19b. It is to be understood that this voltage is of course merely illustrative, and is not to be construed as a limitation of the invention.

The operation `of the discharge device illustrated in Figure 1 is as follows:

input signal will be impressed on each of the electron streams 3, 4, by Ameans of the delay line 2, thereby velocity modulating the same. The electron streams having ditferent average velocities upon becoming density modulated interact so as to produce an amplified Wave. Thef delay line 2,- as noted, is used to impress a signal ontherelectron streams, the amplification, however, taking place in the electron flow itself. The important factor in the interaction is the electric field, which stores energy Vand, acts on the electrons, and the electrons themselves.

The charge of the electrons produces the electricv field; the mass of the electrons, and their kinetic energy, serve as do inductances and magnetic stored energy in electromagnetic propagation. In electronl wave tubes it is customary to-use relatively low voltages'for accelerating the electrons in an electron stream which produces, as a result, low beam current, thereby yielding only a relatively low poweroutput. The weak beam current is acted upon by the impressed high frequency signal which interacts therewith, thereby creating strong modulation of the beam. In the ield free region, between delay lines 2 and 5, the electrons become density modulated by virtue of the faster electrons Vovertaking the slower `electrons and forming concentrated bunches. The electron streams 3, 4 emitted by cathodes 19A and 19B respectively, after passing through the iield free region come under the influence of the high potential connected to helix 5 and collector 6. As a result of the Yhigh potential at helix 5 and-collector 6, the variation -invelocity of the electrons in electron streams 3, 4 become practically insignicant, so that the section of the discharge tube including helix 5, attenuation layer 110, and collector 6 acts as a travelling wave ampliier. To insure the operation ofthis section ofthe tube asa travelling wave tube, the length, the dimensions (pitch and diameter) and the propagation conditions are fixed so that the waves excited in this section of the tube by electron streams 3, 4 will propagate at the same velocity as the electron streams 3, 4 passing therethrough.

Figure 2 illustrates in graphic form why the output section of the high-frequency discharge device 21', operates as a travelling wave tube. In this ligure, the relative amplitude in watts is plotted against electron volts. The electron velocity difference of 50 volts is Vseen to become insignificant under the iniiuence of the 2000 volts connected to the delay line 5 and collector 6.

As stated the attenuation layers 9 and 10 prevent high frequency signals from being reflected beyond the ends 7, 8 of delay lines 2,5, respectively, in the event of any mismatches in the tube. In order to reduce the effect of the attenuation layers on the electron streams 3, 4, it is also possible to gradually increase the diameter and pitch of the helices in the vicinity-of ends 7, 8 and use a ceramic wedge coated with an aquadag suspension to eliminate high-frequency signal reflections. The remaining part of the helix ,may be wound uniformly. It is of course to be understood that the delay line is not limited to the use of a conductor wound into a helical form but includes all high frequency structures capable of reducing the phase velocity of high frequency waves propagated thereby. Examples of some of these well known delay structures, are for instance, periodically loaded lines in` volving capacitive or inductiveV loading or made of circular links.

Figure 3 illustrates a modification of described in relation to Figures 1 and 2.

In thisy ligure, unlike Fig. 1, where the cathodes were disposed side by side resulting in two electron streams moving alongside each other, cathode 22 is centrally located in relation to cathode 21. Cathode 21 is designed to emit a hollow beam (not shown) which encircles the beam emitted by cathode 22 (not shown). These electronbeams are collected at collector 32. Delaylines 25 and 27 are supported by means of rods 23 and24 respectively. These rods are provided at one end thereof lwith attenuation layers '26, 28, respectively, which serve to the invention prevent micro-wave signal reflections. The voltage sources 14, 15, 16, 17 and 18 are connected in the same manner as they Were in the embodiment described in relation to Figure 1. The same potentials for explanatory purposes are applied in this embodiment to the accelerating anode 31 and to the collector as in the embodiment illustrated in Figure l. An input connectorV 29, 29 is illustrated, the outer conductor of which, is joined to the glass envelope 33, the inner conductor of which is connected through a vacuum seal in the envelope, to'th'e input end of the delay line 25. An output connector 30, 30 is likewise connected to the glass envelope 33 at its outer conductor, its inner conductor being connected similarly through a vacuum Seal in the envelope to the output end of delay line 27.

The potential and Vthe size of the output delay line are again chosen, according to the invention, so that the delay line section 2.7 operates as a travelling wave tube section. Y The operation of the embodiment illustrated in Figure 3 is similar to the operation described in relation to Figure 1. The advantage of the arrangement illus'- trated in Figure 3 arises from the closer contact between the two electron streams (not shown), emitted by cathodes 21, 22thereby resulting in greater interaction.

I claim:

l. An' electron discharge device for generating ultrashort frequencies, comprising in combination, a vacuum tight envelope; a iirstrand a second electron beam emitting means located in said envelope, emitting two electron beams having different velocities; collector means located in said envelope, said collector being arranged opposite to and spaced from said first and second electron emitting means to definea common path for said electronV beams; input delay linemeans arranged in the region of said common path of said'electron beams after the same has been emitted by said electron emitting means, said input delay means adapted to be coupled to signal waves to be amplied so as to velocity modulate said electron beams; output delay line means arranged in the region of said path of said electron beams subsequent to and spaced from said input delay line means, sogas to leave between said input and output delay line means a ield free region acting as a traveling wave tube section causing predominantly voltage amplification wherein the velocity modulated electron beams are transformed to density modulated electron beams; a voltage source connectedV to said output delay line means for applying a direct potential thereto which is ,substantially higher than the potential of' said input delay line in such mannerthat said output Ydelay line means acts as a traveling iield tube section causing predominantly power amplification and a signal wave excited therein is propagated therealong at a velocity approximately equal to the'electron beam velocity passing therethrough.

2. An electron discharge device for generating ultrashort frequencies, comprising, in combination, a vacuum tight envelope; a lirst and a second electron beam emitting means located in said envelope, emitting two electron beams having differentrvelocities; collector means located in said envelope, said collector being arranged opposite to and spaced from said first and second electron emitting means to define a common path for said electron beams; an input helix arranged in the region of said common path of said electron beams after the same has been emitted by said electron emitting means, said input helix adapted to be coupled to signal waves to be amplified so as to velocity modulate said electron beams and to act as a traveling wave tube section causing predominantly voltage amplification; an output helix having a predetermined dimension, said output helix being arranged in the region of said path of said electron beams subsequent to and spaced from said input helix, so as to leave between said input and output helices a field free region Whereinthe velocityV modulated electron beams are transformed to density modulated electron beams and amplify .ne an'.

'said signal waves; a voltage source connected to said output helix for applying va direct potential thereto which is substantially higher than that of said input helix in such manner that said output helix acts as a travelling field tube section causing predominantly power amplification and a signal wave excited therein is propagated therealong at a velocity substantially equal to the electron beam velocity passing therethrough.

3. An electron discharge device for generating ultrashort frequencies, comprising, in combination, a Vacuum tight envelope; a first and a second electron beam emitting means located in said envelope, emitting two electron beams having different velocities; collector means located in said envelope, said collecor being arranged opposite to and spaced from said first and second electron emitting means to define a common path for said electron beam; input delay line means arranged in the region of said common path of said electron beams after the same has been emitted by said electron emitting means, said input delay means adapted to be coupled to signal waves to be amplified so as to velocity modulate said electron beams and to act as a traveling wave tube section causing predominantly voltage amplication; output delay line means having a predetermined dimension, said output delay line means being arranged in the region of said path of said electron beams subsequent to and spaced from said input delay line means, so as to leave between the adjacent ends of said input and output delay line means a eld free region wherein the velocity modulated electron beams are transformed to density modulated electron beams; attenuating means connected at the adjacent ends of said input and output-delay line means to prevent intercoupling of said input and output delay lines; a voltage source connected to said output delay line means for applying a direct potential thereto which is substantially higher than the potential of said input delay line means in such manner that said output delay line due to its predetermined dimension and the potential applied thereto acts as a travelling Wave tube section causing predominantly power amplification, and a signal field excited therein is propagated therealong at a Velocity substantially equal to the electron beam and amplify said signal waves velocity passing therethrough.

4. An electron discharge device for generating ultrashort frequencies, comprising, in combination, a vacuum tight envelope, a first electron emitting means; a second electron emitting means arranged in coaxial relation to said first electron emitting means, said first and second electron emitting means located in said envelope and emitting two electron beams having different velocities, one of said electron beams propagating within the other; collector means located in said envelope, said collector being arranged opposite to and spaced from said first and second electron emitting means to define a common path for said electron beams; input delay line means arranged in the region of said common path of said electron beams after the same has been emitted by said electron emitting means, said input delay means adapted to be coupled to signal waves to be amplified so as to velocity modulate said electron beams and to act as a traveling wave tube section causing predominantly voltage amplification; output delay line means arranged in the region of said path of said electron beams subsequent to and spaced from said input delay line means, so as to leave between said input and output delay line means a field free region wherein the velocity modulated electron beams are transformed to density modulated electron beams and amplify said signal Waves; a voltage source connected to said output delay line means for applying a direct potential thereto which is substantially higher than the potential of said input delay line in such manner that said output delay line acts as a travelling field tube section causing predominantly power amplification and a signal wave excited therein travels therealong at a velocity approximately equal to the electron beam velocity passing therethrough, A

5. vAn electron discharge device comprising, in coibination, an elongated closure defining a path of travel for a stream of charged particles; electrode means located at one end yof said closure for directing a pair of closely coupled streams of charged particles lengthwise of said path at different velocities; velocity modulation means located near said one end of said elongated closer acting a traveling Wave tube section causing predominantly voltage amplification for velocity modulating said pair of streams of charged particles with a signal it `is desired to amplify, whereby said modulated pair of streams of charged particles interact with one another to produce amplification; travelling field means causing predominantly power amplification spaced from said velocity modulation'means and located near the other end of said elongated closure, said travelling field means having a substantially higher potential than said velocity modulation means for accellerating substantially said pair of streams of charged particles and for deriving from said accelerated streams of charged particles a slow electromagnetic wave having a velocity in the direction of movement of said streams substantially equal to that of said streams, whereby said streams and slow electromagnetic wave interact to produce amplification; and means coupled to said traveling field means for deriving therefrom an amplified signal.

6. An electron discharge device comprising, in combination, an elongated closure defining a path of travel for a stream of charged particles; electrode means located at one end of said closure for directing a pair of closely coupled streams of electrons lengthwise of said path at different velocities; velocity modulation means located near said one end of said elongated closure acting a traveling wave tube section causing predominantly voltage amplification for velocity modulating said pair of streams of electrons with a signal it is desired to amplify, whereby said modulated pair of streams of electrons interact with one another to produce amplification; traveling field means causing predominantly power amplification spaced from said velocity modulation means and located near the other end of said elongated closure, said travelling field means having a substantially higher potential than said velocity modulation means for accelerating substantially said pair of streams of electrons and for deriving from said accelerated streams of electrons a slow electromagnetic Wave having a velocity in the direction of movement of said streams substantially equal to that of said streams, -wlhereby said streams and slow electromagnetic wave interact to produce amplification; and means coupled to said traveling lfield means for deriving therefrom an amplified signal.

7. An electron discharge device comprising, in cornbination, an elongated closure defining a path of travel for a stream of charged particles; electrode means located at one end of said closure for directing a pair of closely coupled streams of charged particles lengthwise of said path at different velocities; velocity modulation means including delay line means located near said one end of said elongated closure acting a traveling wave tube section causing predominantly voltage amplification for velocity modulating said pair of streams of charged particles with a signal it is desired to amplify, whereby said modulated pair of streams of charged particles interact with one another to produce amplification; traveling field means causing predominantly power amplification including delay line means spaced from said velocity modulation means and located near the other end of said elongated closure, said travelling field means having substantially higher potential than said velocity modulation means for accelerating substantially said pair of streams of charged particles and for deriving from said accelerated streams of charged particles a slow electromagnetic wave having a velocity in the direction of- `magnetic wave interact to produce amplification;fand

Ameans coupled to said traveling field means for deriving therefrom an amplified signal.

8. An electron discharge device comprising, in combination, an elongated closure defining a path of travel for a stream of charged particles; electrode means located at one end of said closure for directing a pair of closely coupled streams of charged lparticles lengthwise of said path at different velocities; velocity modulation means including a helix of wire concentrically arranged with respect to the path traveled by said streams of charged particles and located near said one end of said elongated closure acting a traveling wave tube section causing predominantly voltage amplification for velocity modulating said pair of streams of charged particles with a signal it is desired to amplify, whereby said modulated pair of streams of charged particles interact with one another to produce amplification; traveling field means causing predominantly power amplification including a helix of wire concentrically arranged with respect to the path traveled by said streams of charged particles, spaced from said velocity modulation means and located near the other end of said elongated closure, said helix of wire of said travelling field means being at a substantially higher potential than said helix of wire of said velocity modulation means for accelerating substantially said pair of streams of charged particles and for deriving from said accelerated streams of charged particles a slow electromagnetic wave having a velocity in the direction of movement of said streams substantially equal to that of said streams, whereby said streams and slow electromagnetic wave interact to produce amplification; and means coupled to said traveling field means for deriving therefrom an amplified signal.

9. An electron discharge device comprising, in combination, an elongated closure defining a path of travel for a stream of charged particles; electrode means located at one end of said closure for directing a pair of closely coupled streams of charged particles lengthwise of said path at different velocities; velocity modulation means including delay line means located near said one end of said elongated closure acting a traveling Wave tube section causing predominantly voltage amplification for velocity modulating said pair of streams of charged particles with a signal it is desired to amplify, whereby said modulated pair of streams lof charged particles interact with one another to produce amplification; means for maintaining said delay line means at a given potential; traveling field means causing predominantly power amplification including delayl line means spaced from said velocity modulation means and located near the other end of said elongated closure; means for maintaining said last-named delay line means at a potential substantially more positive than that of said first-named delayV line means for accelerating substantially said pair of streams of charged particles and `for deriving from said accelerated streams vof charged rparticles a slow electromagnetic Wave having a velocity in the direction of movement of said streamssubstantially equal to that of said streams, whereby said streams and slow electromagnetic wave interact to produce amplification; and means coupled to said traveling field means for deriving therefrom an amplified signal.

l0. An electron discharge device comprising, in cornbination, an elongated closure defining a path of travel for a stream of charged particles; electrode means located at one end of said closure for directing a pair of closely coupled streams of electr-ons lengthwise of said path at different-velocities; velocity modulation means including a helix ofV wire concentrically arranged with respect to` the path traveled by said streams ofrcharged particles and located 'near said one "end of said elongated closure acting a traveling wave tube section causing pre- Cil dominantly voltage amplification for velocity modulating said pair of streams of electronsY with a signalY it is desired to amplify, whereby said modulated pair 'of streams of electrons interact with one another to produce amplification; traveling field means causing predominantly power amplification including a helix of wire concentrically arranged with respect to the path traveled by said streams of charged particles, spaced from said velocity modulation means and located near the other end of said elongated closure, said helix of wire of said travelling field means being at a substantially higher potential than said helix of wire of said velocity modulation means for accelerating substantially said pair of streams of electrons and for deriving from said accelerated streams of electrons a slow electromagnetic wave having a velocity in the direction of movement of said streams substantially equal to that of said streams, whereby said streams and slow electromagnetic wave interact to produce amplification; and means coupledV to said traveling field means for deriving therefrom an amplified signal. Y

ll. An electron discharge device comprising, in combination, an elongated closure defining a path of travel for a stream of charged particles; electrode means located at one end of said closure for directing a pair oifsclosely ycoupled streams of charged particles lengthwise of said path at different velocities; velocity modulation means located near said one end of said elongated closure acting a traveling wave tube section causing predominantly voltage amplification for velocity modulating said pair of streams of charged particles with a signal it is desired to amplify, whereby said modulated pair of streams of charged particles interact with one another to produce amplification; traveling field means causing predominantly power amplification spaced fromrsaid velocity modulation means and located near the other end of said elongated closure, said travelling field means having a substantially higher potential than said velocity modulation means for accelerating substantially said pair of streams of charged particles and for deriving from said accelerated streams of charged particles a slow electromagnetic wave having a velocity in the direction of movement of said streams substantially equal to that of said streams, whereby said streams and slow electromagnetic wave interact torproduce amplification; attenuation means operatively associated with s'aid `velocity modulation means and said traveling field means Vfor preventing intercoupling of said two means; and means coupled to said traveling field means for deriving therefrom an amplified signal.

l2. An electron discharge device comprising, in combination, an elongated closure defining a path of travel for a stream of chargedrparticles; electrode means located at one end of said closure for directing a pair of closely coupled streams of charged particles Vlengthwiseof said path at different velocities; velocity modulation means including a helix of wire concentrically arranged with respect to the path traveled by said streams of charged particles and located near said one ,end of said elongated closure acting a traveling wave tube section causing predominantly voltage amplification for velocity modulating said pair of streams of charged particles with a signal it is desired to amplify, whereby said modulated pair of streams of charged particles interact with one another to produce amplification; traveling field means causing predominantly powerkamplification including a helix of wire concentrically arranged with respect' to the path traveled by said streams of charged particles, spaced from said velocity modulation means and located near the other end of said elongated closure, said helix of wire of said travelling field means being at a substantially higher potential than said helix of wire of said velocity modulation means vfor accelerating substantially said pair ot' streams of charged particles and for deriving from said accelerated streams of charged particles a slow electromagnetic wave having a velocity in the direction of movement of said streams substantially equal to that of said streams, whereby said streams and slow electromagnetic wave interact to produce` amplification; attenuation means located at the ends adjacent one another of said two helices of wire for preventing intercoupling of said velocity modulation means and said traveling field means; and means coupled to said traveling iield means for deriving therefrom an amplied signal.

13. An electron discharge device comprising, nation, an elongated closure deiining a path of a stream of charged particles; electrode means one end of said closure for directing a pair coupled streams of electrons, one concentric other, lengthwise of said path at different in combitravel for located at of closely ywith the velocities;

velocity modulation means located near said one end of said elongated closure acting a traveling wave tube section causing predominantly voltage amplification for velocity modulating said pair of streams of electrons with a signal it is desired to amplify, whereby said modulated pair of streams of electrons interact with one another to produce amplification; traveling ield means causing predominantly modulation power amplification spaced from said velocity means and located near the other end of References Cited in the tile of this patent UNITED STATES PATENTS 2,238,770 Blumlein Apr. 15, 1941 2,406,370 Hansen et al. Aug. 27, 1946 2,585,582 Pierce Feb. 12, 1952 2,652,512 Hollenberg Sept. 15, 1953 2,652,513 Hollenberg Sept. 15, 1953 2,653,270 Kompfner Sept. 22, 1953 2,694,159' Pierce Nov. 9, 1954 2,801,362 Hebenstreit et al July 30, 1957 2,802,136 Lindenblad Aug. 6, 1957

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