US2757311A

US2757311A - Double beam progressive wave tube

Info

Publication number: US2757311A
Application number: US164127A
Authority: US
Inventors: Huber Harry; Kleen Werner
Original assignee: CSF Compagnie Generale de Telegraphie sans Fil SA
Current assignee: Thales SA
Priority date: 1949-06-02
Filing date: 1950-05-25
Publication date: 1956-07-31
Anticipated expiration: 1973-07-31
Also published as: FR993102A; GB688925A; DE965726C

Description

SR D h K, to Jim July 31, 1956 H. HUBER ETAL DOUBLE BEAM PROGRESSIVE WAVE TUBE Filed May 25. 1950 VNJ I L EF I IT a J 1 LI a LuLv q Lv

United States Patent DOUBLE BEAM PROGRESSIVE WAVE TUBE Harry Huber, Paris, France, and Werner Kleen, Madrid, Spain, assignors to Compagnie Generale dc Telegraphic Sans Fil, a corporation of France Application May 25, 1950, Serial No. 164,127

Claims priority, application France June 2, 1949 6 Claims. (Cl. 315-35) The present invention relates to a particular form of travelling wave tube and to the application of this tube to arrangements in which this form affords considerable advantages.

It is well known that the operation of a travelling wave tube is based on the phenomenon of interaction between an electron beam and a travelling wave, this wave being amplified by this interaction efiect if the speed of the electrons is approximately equal to the phase velocity of the wave. The invention relates to this type of tube, and more particularly both to those in which the interaction space is not subjected to the action of a transverse electrostatic field or to the action of a transverse magnetic field (Kompfner-Pierce type), and to tubes having crossed electrostatic and magnetic fields, as proposed in application Serial No. 794,164, filed on December 27, 1947, now Patent No. 2,511,407, and in application Serial No. 102,896, filed on July 2, 1949, now Patent No. 2,687,777.

The tube according to the invention is characterised by the existence of two electron beams propagated in opposite directions, the two beams moving in the electromagnetic field of waves guided by a same delay line. However, there is only one delay line defining two electron and wave interaction spaces, each of which is traversed by one of the two electron beams.

The accompanying drawings illustrate two examples of the invention as applied to travelling Wave tubes respectively without and with a transverse magnetic field.

In these drawings, Figure 1 is an axial section of a first embodiment of tube without a transverse magnetic field, and Figures 2 and 3 are respectively an axial section, and a cross-section on line 33 of Figure 2, of a second embodiment with a transverse magnetic field.

With reference to Figure 1, the tube has, at one of its ends, an electron gun generating a tubular beam 1 which is propagated along the outside of a linear helix 2 employed as a delay line. The gun is composed of the annular cathode 3, the Wehnelt or control cylinder 4 and the accelerating or anode electrode 5. At the opposite end is situated another electron gun constituted by a cirular cathode 6, the Wehnelt cylinder 7 and the anode 8. This gun generates the second beam of electrons 9, which is propagated along the inside of the helix 2 in the opposite direction to the beam 1. At the two ends of the helix are situated dipoles 10 and 11 providing the coupling between the delay line (helix) and the wave guides 12 and 13. The tube is surrounded by a magnetic coil 14 serving to focus the beams. A battery 24 is provided for each gun with a connection from its positive terminal to the anode or 8 and a potentiometer 25 across its two terminals and connected by

intermediate taps

26 and 27 to the cathode 3 or 6 and to the control cylinder 4 or 7. For control purposes, each control electrode 4 or 7 may have a control circuit 28 connected thereto.

The advantage of the tube operating with two beams propagated in opposite directions, as compared with a tube operating with one beam only, will be obvious on ex- 2,757,311 Patented July 31, 1956 planation of the operation of the tube according to the invention. There are in particular two possible advantageous applications:

(a) One of the two beams serves to amplify an injected wave, while the other generates an internal feedback which causes the amplification to increase.

(b) The tube serves for amplification in both directions, it being possible to discontinue the amplification in one of the directions when the amplification in the other direction takes place.

In order to explain the application referred to under (a), it will be assumed by way of example that the signal to be amplified is introduced by means of the guide 12. The amplification is then efiected by means of the tubular beam 1, the mechanism of this amplification being well known, so that it is unnecessary to describe it in detail. The wave to be amplified is propagated in the direction toward the guide 13 and the field of this wave has practically no influence on the behaviour of the second beam, except at the output end, that is to say, in the region of the guide 13. If a small error in matching is left between the guide 13 and the dipole 11, a standing wave is produced which excites a wave moving in the opposite direction to the wave introduced by means of the guide 12. This second wave, which moves in the direction of the beam 9, generated by the cathode 6, is amplified owing to the interaction with this beam. If a small error in matching is left between the guide 12 and the dipole 10 a new standing wave is produced at this point on arrival in the guide 12. On suitable adjustment of the phase of this second wave, an increase of the input signal is obtained, that is to say, the process corresponds to an internal feedback which causes the gain of the tube to increase. The adjustment of the phase may be effected by regulating the potential of the cathode 3 with respect to that of the helix 2 and the feedback mechanism may be regulated by variation of the potential of the second cathode 6 or by regulation of the current of the beam 9 serving as a reaction element.

The application referred to under (b) is advantageous, for example, in a radiotelephonic connection on a carrier wave in the centimetric wave range. In this case, the tube permits amplication in both directions and the signal can be introduced either into 12 or into 13, it being possible to tap the amplified power either by means of 13 or by means of 12. For this application of the tube, it may be desirable to suppress the feedback. This is done by interrupting the current of the beam whose direction is opposite to the desired direction of amplification, by negative impulses supplied by the control circuit 28 of one of the Wehnelt cylinders, for example. The natural attenuation of the helix is sufiiciently great for a signal, which is not amplified by the interaction with the beam, to be sufliciently attenuated. The means for the automatic suppression of one of the directions of amplification and commutation of the latter are well known in the art of line telephony, and although they may also be applied (as shown) in the circuit of this tube they are not included in the invention.

It is possible that the tube operating with two beams propagated in opposite directions may be more difiicult and more costly to construct than two tubes operating with a single beam, each of which serving for amplification in one direction only. However, the use of the tube according to the invention makes it possible to employ the same external circuits for amplification in the two opposite directions, while two tubes operating with a single beam require separate circuits.

The principle of the invention is not limited to a tube of the type shown in Figure 1, in which the magnetic field serves for focussing and is directed in the direction of propagation of the waves. It may also be applied to a tube having crossed magnetic and electrostatic fields, the mechanism of which has been described in the specifications hereinbefore referred to. A tube of this nature is shown in Figures 2 and 3. The references 3 and 6 designate the two cathodes. The delay line consists of a flat helix 2 or of a wire bent in sinuous form, which is situated between two

conductors

22 and 23. The two interaction spaces are situated on either side of the helix. In order to generate the transverse electric field necessary for the operation of this type of tube, the two

conductors

22 and 23 are negative with respect to the helix 2. The transverse magnetic field in Figure 2 is perpendicular with respect to the plane of the drawings. In Figure 3, and 17 indicate diagrammatically the pole pieces of the magnet generating this magnetic field.

Instead of guides 12 and 13 as shown in Figure 1, there are employed in the tube shown in Figure 2, by way of example, coaxial lines coupled to the two extremities of the helix 2, one of which, 16, is shown in Figure 3.

As in the tube shown in Figure 1, the two beams leaving the cathodes 3 and 6 have opposite directions and are propagated in the field of the same delay line. The transverse magnetic field has the same direction in both in teraction spaces, and the two electrostatic fields must therefore be of opposite direction in order that the movements of the electrons may be opposed.

The principle of the invention is not limited to tubes with a helix or a sinuous Wire employed as the delay line, but may be applied to tubes having a delay line of any form, the applications of the principle in the tubes shown in Figures 1 and 2 only being shown by way of example.

Similarly, the principle is not limited to tubes of linear form, but is also applicable to tubes of circular form.

We claim:

1. An electron discharge tube comprising an envelope, a delay line dividing the inside of the envelope into two distinct separate parallel electron and wave interaction ducts, ultra-high frequency terminals coupled to opposite nections to the line and sources for biasing the latter negatively with respect to the former, and means associated with each source for concentrating the emission thereof into a beam propagating in the associated duct at a desired velocity substantially equal to the wave phase velocity of energy flowing in the line in the same direction.

2. An electron discharge tube comprising a retardation line in the form of a helix, means coupled with one end of said line for introducing ultra-high frequency energy into said line, means coupled with the other end of said line for extracting the amplified ultra-high frequency energy, means comprising an emissive cathode situated near one end of said retardation line and a source of potential connected between said cathode and said line for giving to said cathode a negative potential with respect to said line, and a system of electron lens electrodes, with accelerating and focusing means for causing the electrons concentrated in tubular beam form to enter an interaction space adjacent and exterior to said line, and parallel thereto, at a velocity substantially equal to the phase velocity of the ultra-high frequency energy introduced in said one end of the line and propagating towards said other end thereof, means for causing propagation of ultra-high frequency en ergy from said other end towards said one end of the line, and means comprising a second emissive cathode situated near said other end of said line with a second system of electron lens electrodes and accelerating and focusing means, and a source of potential connected between said second cathode and said line for giving to said second cathode a negative potential with respect to said line thereby to direct a beam of electrons of cylindrical form, inside said helix, in the opposite direction to and uncoupled from the beam of said first cathode, at a velocity substantially equal to the phase velocity of the ultra-high frequency energy propagating in opposite direction with respect to said energy introduced in the line.

3. An electrondischarge tube, comprising a retardation line, means coupled with one end of said retardation line for introducing ultra-high frequency energy, on one side of said line a first emissive cathode situated near one end of said line and emitting a first electron'beam and a first conducting electrode extending parallel to said retardation line, on the other side of said line, a second emissive cathode located near. the other end of said line and emitting a second electron beam uncoupled from said first beam, and'a second conducting electrode extending parallel to said line and to said first electrode, said line and said electrodes defining therebetween two interaction spaces separated by said line, means comprising a source of potential connected to said line on one hand, and to said cathodes and said electrodes on the other hand, for giving negative potentials to said cathodes and said electrodes with respect to said line, and means for establishing a substantially time constant magnetic field in said interaction spaces substantially perpendicular to said line and parallel to said electrodes, thereby to direct two parallel and reciprocally offset electron beams into said interaction spaces, said beams travelling in reciprocally opposite directions at a velocity substantially equal to the phase velocity respectivcly of the ultra-hi h frequency energy introduced in said one end of the line and propagating towards said other end, and of the ultra-high frequency energy propagating opposite to the former.

4. A tube as claimed in claim 1 in combination with means for varying the potentials of the two sources.

5. A tube as claimed in claim 1 in combination with means for varying the current of at least one of the two electron beams.

6. A tube as claimed in claim 1 in combination with means for applying a voltage to an electron lens electrode to interrupt the current of one of the beams.

References Cited in the file of this patent UNITED STATES PATENTS 2,280,824 Hansen et al. Apr. 28, 1942 2,381,320 Tawney Aug. 28, 1942 2,406,370 Hansen et al. Aug. 27, 1946 2,406,371 Hansen et al. Aug. 27, 1946 2,479,084 Rosenthal Aug. 16, 1949 2,511,407 Kleen et al June 13, 1950 2,578,434 Lindenblad Dec. 11, 1951 2,585,582 Pierce Feb. 12, 1952 2,600,509 Lerbs June 17, 1952 2,607,904 Lerbs Aug. 19, 1952 2,635,206 Pierce Apr. 14, 1953 2,652,513 Hollenberg Sept. 15, 1953 OTHER REFERENCES Article by A. V. Hollenberg, pp. 52-58, Bell System Tech. Journal for January 1949.

Article by A. V. Haefi, pp. 4-10 incl., Proc. I. R E. for January 1949.