US2567339A - Electron tube for generating ultra-short electromagnetic oscillations - Google Patents

Description

Sept. 11, 1951 F. LUDI 2,567,339

ELECTRON TUBE FOR GENERATING ULTRA SHORT ELECTROMAGNETIC OSCILLATIONS Filed Sept. 11, 1946 Eeocfance Ede, e/c.

Patented Sept. 11, 1951 ELECTRON TUBE FOR GENERATING ULTRA- SHORT ELECTROMAGNETIC OSCILLAT IONS Fritz Liidi, Zurich, Switzerland,

assignor to Patelhold Patentverwertungs- & Elektro- Holding A.-G., Glarus, Switzerland Application September 11, 1946, Serial No. 696,116 In Switzerland September 12; 1945 1 Claims. (01. 315-40) The present invention concerns an electron tube for ultra-short electromagnetic oscillations which has at least one cathode, an anode consisting of segments biased positively with respect to the cathode, and a magnet field, there being a high frequency alternating voltage between neighbouring anode segments, and where at a distance which is approximately constant from the anode a guide electrode is provided which at least over its greatest part is not penetrated by the electrons, the electrode following paths between the guide electrode and the anode.

The high frequency alternating field of the electron tubes produces for instance by means of induction or influence efiect high frequency currents in the tube elements, such as the cathode, the guide electrode, and thelike, and this results in a loss of high frequency power. The losses can be of an ohmic nature, or on the other hand these may be caused by the radiation of high frequency energy.

The object of the present invention is to avoid these disadvantages. This is achieved by connecting part of the tube, which does not belong to the oscillating circuit for determining the frequency of the tube and in which high frequency currents occur during operation, to a low-radiation electrical oscillating system which i tuned in such a manner that the high frequency losses of the tube are at least approximately a minimum.

' A number of constructional examples of the invention are illustrated diagrammatically in the accompanying drawing where Fig. -1 shows a. sectional view of a tube, Fig. 2a is a circuit diagram of acathode heating circuit embodying the invention; Fig. 2b i a fragmentary central section illustrating a constructional form of a loss-reducing oscillating system connected to the heating circuit system, whilst Fig. 3i1lustrates an arrangement of the oscillating system which serves simultaneously for'collecting the high frequency energy.

In the sectional view of the tube shown in Fig. 1 the section is taken along a plane passing through the axis of the tube. Reference numeral l indicates the electron-emitting hot cathode which in this case is in the form of a spiral, 2 is a cylindrical guide electrode, and l l a ringshaped cavity resonator of rectangular section.

which is at anode potential. The capacitive part ofthe cavity resonator is mainly formed, by the segments 5 which are arranged next to each other in the circumferential direction. 8 i a conductive loop for collecting the energy. The

denser l3.

method of operation of the tube has already-been described in detail in my copendlng application Ser. No. 583,220, filed March .17, 1945, and now -U. S. Patent No. 2,508,280, issuedMay 16, 1950,

so that it does not need to be. repeated again.

The leads IZ'for the heating current arerin the form of Lecher lines which are closed by .a capacitance 3. The Lecher line can be varied for instance by shifting the capacitance l3 together with its leads, I4 alongthe Lecher system l2. The oscillating circuitcomprising the Lecher system l2, the capacitance l3 with the leads l4, and the cathode I, is tuned according to the invention in such a, manner that the high .frequency losses are a minimum. Tuning is not necessarily achieved by varying the electrically efiective length of the Lecher line. It can" also be varied by alterin the capacitance of the con- The side plates 1 oftheelectron tube :are connected to a further Lecher system; this system is tuned by shifting the short-.circuiting element l6 to such anextent-that avalue is reached where the high frequency losses are a minimum.

Tuning for minimum .high'irequency losses of the tube is generallyachieved whenthe length of the Lecher line is an uneven multiple of a quarter wave length of the prevailing oscilla plates with separate'individually tuneable oscillating systems: Furthermore it is generally an advantage if the high frequency oscillation cire cuits are mutually decoupled. Such decoupling is not only advisable between the oscillation circuits in order to reduce the high frequency losses, but also between the latter andfor instance the collector loop 8. With Lecher lines it is possible to achieve sucha decoupling effect by arranging them perpendicular toeach other.

With the-form of the invention shown in Figs. 2a and 2b the detrimental radiation at one end of the lineis prevented by ascreening pot I6 instead of a tuned two-wire Lecher line. Ref-'- erence numeral I indicates the hot cathode and i2 are the cathode leads. Screening pot l6 has a length of M4 or an -uneven' multiple.- of same. The screening pot can belocated inside or outside the tube vessel. Since there is a magnetic field in a direction parallel to the cathode, with a special constructional form of the tube having a permanent magnet M, the screening pot is combined with the magnet in such a manner that the external conductor is at least partly formed by the iron 01' the magnet and is constructed as a bore in:the iron 01. :the magnet. A-cathode lead l2 extends through the bore of magnet M, and a conductive plug [6a is slidable in the bore and on the lead I! to adjust the eflective length of the screening pot.

Since the cathode is surroundedbywthewmagnetic lines of forces of the high frequency oscillations of the cavity resonator, these induce electric currents in the cathode which 'due to the tuning of the heating conductors are prevented from flowing away over the heating curproperties. In this form of the invention-a -low- "loss conductor l 8'is arranged in parallel with "the heating spiral, so that'the oscillating system is as far as possible from losses. To prevent the heating current from =i1owing through this conductor, one end of this latter is connected over a capacitance l9 -to= the oscillation circuit or reducing the high irequency losses, so that there is a separation of the direct-current kind. Collector electrode "20 serves to collect ;-the high -frequency energy.

.As a result of coupling the cavity resonator oscillations with the currents;flowing in the osciliation circuits. the frequency 'of the oscillations of the cavity resonator can be influenced by arying the tuning of the oscillation circuits, 'llt'is therefore advisable to makethe impedance A! variable. In a modified :form of the Fig. 3 circuit the impedance [7 consists of a cavity resonator.

Another modified constructional form of the invention is obtained by substituting a tube arrangement, not showmwhich acts as a variable condenser, for the capacitance 13 of Fig. 1, this tube being influenced for instance by altering the grid bias, This enables the tube oscillations to be modulated.

other embodiments-of the invention in which the cathode is electrically connected between and mechanically supported by a pair of side plates are described and claimed specifically in my copending application 'Ser. No. 696,117, filed September 1 1, 1940, which matured as Patent No. 2,522,184 on September 12, 1950,

Iclaim:

1. An electron tube for generating ultra shor t electromagnetic oscillations comprising an-evacuated envelope, a cathode and an anode within said evacuated envelope, said anode consisting ments, whereby electrons emitted by said cathode follow cycloidal paths in the annular space between the anode segments and said guide electrode, and a tuned oscillation system connected to said guide electrode; said oscillation system being non-resonant at the frequency of the generated oscillations.

2. An electron tube as recited in claim 1, wherein .said cathode is provided with leads for connecting the same in a cathode-heating circuit, :in combination with means suppressing currents of the frequency of the generated oscillations in said cathode and cathode leads, said suppressing means comprising a screening pot on one cathode lead and having a length equal to a ,-.quarter-wavelength of the generated oscillations.

.3. An electron tube as recited in claim 2, wherein said means for establishing a magnetic field comprises a permanent magnet having bores therethrough in axial alinement with said cathode, said cathode leads extend from opposite ends-ofsaidcathode and pass through said bores, and said screening pot comprises a conductive plug slidable in one of said 'bores and on the cathode lead extending through that bore.

4. An electron tube :for generating ultra short electromagnetic oscillations comprising an evacuated envelope, a cathode and an anode within said evacuated envelope, said anode consisting iii-segments adapted to be biased positively with respect to saidcathode and arranged in a cylindrical array defining a cylindrical space within which said cathode is located, means for estab- 'lishing .a magnetic field within said cylindrical space-and parallel to the axis thereof, side plates insulated irom said anode segments and arranged*perpendicular to the axis of said cylindrical spa-ceat the ends thereof, and a tuned oscillationsystem-connected to 'said side plates; said oscillation system being non-resonant at the frequency of the generated oscillations.

5. An electron tube :as recited in claim 4, in combination .with a guide electrode of generally cylindrical :form within said cylindrical space and located at a substantially uniform distance from said anode segments, said guide electrode -being mechanically .and electrically connected to one-of said side plates.

of segments adapted to be 'biased positively with V respect to said cathode and arranged in a-cylindrical array defining a cylindrical space within which said cathode is located, means for estabjl-ishing a magnetic field within said cylindrical space and parallel to the axi thereof, a guide electrode of generally cylindrical form within said cylindrical space and located at a substantially uniform distance from said anode seg- '6. An electron tube as recited in claim 4, wherein at least a part of said tuned oscillation system is a Lecher line.

An electron tube as recited in claim 6, 'wherein said 'Lecher line includes means adjustable to vary the electrically effective length thereof.

FRITZ LiiDI.

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

UNITED STATES PATENTS Number Name Date 2,128,235 Dallenbach Aug. 30, 1938 2,147,159 Gutton et al. Feb. 14, 1939 2,163,589 Dallenbach et al. June 28, 1939 2,167,201 Dallenbach July 25, 1939 2,207,846 Wolfi July 16, 1940 2,406,277 Bondley Aug. 20, 1946 2,422,695 McRae June 24, 1947 2,428,622 Gurewitsch Oct. 7, 1947 2,432,571 Haeif Dec. 16, 1947

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