US2128231A - High frequency oscillator tube - Google Patents

Description

1938. w. DALLENBACH 2,128,231

HIGH FREQUENCY OSCILLATOR TUBE Filed Oct. 11, 1934 2 Sheets-Sheet l 6 /70 ibfenf/a/ /n ventor:

WALTER DALLENBAQH wMRQ/MW ATTORNEYS Aug. 30, 1938. w. DALLENBACH HIGH FREQUENCY OSCILLATOR TUBE 2 Sheets-Sheet 2 Filed Oct. 11, 1954 lnventor: WALTER [ALEN EACH QAM Vl/ M ATTORNEYS Patented Aug. 30, 1938 UNITED STATES PATENT OFFICE Walter Diillenbach, Berlin-Charlottenburg, Germany, assignor to N. V. Machinerieen-en Apparaten Fabrleken "Meaf,

lands Utrecht, Nether- Applicatlon October 11, 1934, Serial No. 747,948 In Germany October 13, 1933 14 Claims.

My invention relates, to an electron tube intended for exciting, i. e. for generating, amplifying or receiving high-frequency, eleotro-magnetic oscillations, particularly oscillations having a wave length of less than 1 m.

The electron tube consists of a resonator which is excited by a flow of electrons. In the province of the high-frequency oscillations, particularly with a wave length of less than 1 m., it is a favourable feature to design the resonator as free of damping as possible For the purpose of avoiding stray radiation, which in connection with high frequencies represents a considerable damping, the resonator is constructed, in accordance with 5 the present invention, as a hollow space limited by metallic walls and closed for the exit of stray radiation. In consequence thereof the oscillation of the resonator attains higher voltage amplitudes than an oscillating circuit with stray radiation. Furthermore, the controlling effect of the resonator upon the exciting flow of electrons will be enhanced. It has thus been rendered possible, with the aid of the expedient developed in accordance with the present invention, to increase in a generator the oscillatory power, in an amplifier the power amplification ratio and in a receiver the receptive sensitiveness to a considerable degree.

The employment of a hollow space resonator renders it, furthermore, possible to omit the glass vessel otherwise usual with electron tubes and to design the hollow space serving as resonator simultaneously as a vacuum vessel. For the purpose of maintaining the flow of electrons exciting the resonator to oscillations, it is essential to impart to the electrodes, partly formed by the walls of the hollow space serving as resonator, direct voltages. It follows therefrom that it will be necessary to insulate different parts of the w metallic walls of the hollow space from each other and to introduce current conductors into the closed hollow space. It is advisable to employ for this purpose fusions of glass with metal, so that the hollow space serving as resonator consists of two or of a plurality of wall parts, insulated from each other and closely joined, being made, to form a closed and vacuum tight hollow space through the medium of the longitudinal soldering seams of glass, so to speak.

If the cathode for emitting electrons is disposed outside the hollow space serving as resonator, it is essential to provide in the wall of the hollow space an aperture, through which the flow of electrons enters the hollow space and excites the oscillation. By means of this aperture which may, by way of example, have the form of a grid, the hollow space, serving as resonator, is coupled with the space in which the cathode has been disposed. In many cases it is advisable, that the frequency to which the 5 electron tube responds, is exclusively determined by one of the natural frequencies of the hollow space serving as resonator. In this case it is recommended to detune the space enclosing the cathode in contrast to the hollow space serving 10 as resonator, particularly to tune it to a higher frequency, so that coupling oscillations between the two spaces referred to do not take place.

If this measure is properly observed and if care is taken that generally no further resonators are 16 connected with the hollow space serving as resonator which might give rise to coupling oscillations, an electron tube will be obtained which is excited only for natural oscillations of the hollow space serving as resonator. As generator, 20 therefore, it generates a frequency which coincides with that natural frequency of the hollow space serving as resonator which is excited through the medium of the flow of electrons; as receiver or amplifier it will likewise respond only 5 to that natural frequency of the hollow space serving as resonator, which is excited by the flow of electrons.

Figs. 1a and 2a represent two examples of the present invention, in longitudinal sections 30 through the axis, and Figs. lb and 2b cross sections vertically to the axis of the rotary-symmetrical arrangement.

Fig. 3, finally, is a diagram of condition from which the voltages may be gathered for which 35 the arrangements in accordance with Fig. 1a and Fig. 2a oscillate.

In Figs. 1a and lb A represents a metallic tube of circular cross section. Coaxially thereto a tube of smaller diameter has been disposed. 40 This smaller tube consists of the two tube sections B1 and B2 rigidly connected with each other by axial barsof the grid G. The tubes A and B1 or B2 are provided at their ends with collars P1, P2 or Q1, Q2 closing up the Lecher system, formed by ABr GB2, at the ends through the medium of the existing short circuit capacities between the plates P1, Q1, in such a manner that a penetration of a stray radiation, which would exercise a considerable damping effect on the 5 oscillation of the Lecher system, through the narrow slits between P1 and Q1 or P2 and Q2, has been rendered impossible.

For the purpose of ensuring to the furthest possible extent an unimpeded flow of the high 55 frequency current on the surface of the inner conductor 81 GE, the grid elements are con nected with the tube sections B1, B2 parallel to the high frequency current, i. e. parallel to the axis 0! the arrangement.

In the axis of the arrangement, 1. e. within the high frequency conductor formed by the parts 31 G Be, a tunsten filament has been fitted between two substantial cylinders C1, C: as cathode K. These cylinders C1, C: are made to support at their ends the plates E1, E2. In view of the fact that these plates E1, E: are positioned closely adjacent to the plates Q1, Q1 connected with B1, Ba and also the cylinders C1. C2 leave free only a narrow slit opposite the inside of the tubes B1. Ba, it is obvious that the cathode K is situated within a hollow space essentially limited by the grid G and the cylinder faces C1, C2. This hollow space possesses an essentially shorter axial length than the Lecher system formed by the conductors A B1, G B: and it is for this reason detuned to a high frequency in contrast to this Lecher system. An oscillation within this Lecher system, in which at the point of the grid G a potential loop is formed, in the vicinity of the plates Q1, Q2, however, potential nodes, will, therefore, not be capable of exciting the hollow space, within which the cathode K has been positioned, to oscillations. For this reason the cathode space has not, in spite of its being coupled with the hollow space A B1 G B1, any detuning effect upon the hollow space resonator proper.

The hollow space serving as resonator, particularly the tube A, the collars P1, P1 and the plates E1, E2, simultaneously serve as vacuum vessel for the electron tube. To this end the edges of the plates E1, E1 have been fused with the edges of the collars Q1, Q: and P1, P: by means of glass-seals, so as to be vacuum proof. These glass seals connect the edges of the disk-like members in approximately the same manner as welded or soldering seams.

For the purpose of exciting oscillations of the Lecher system formed by A 131, G B1, a flow of electrons is utilized passing through the grid G in the potential loop of the resonator into the hollow space. In connection therewith a positive, particularly a high positive direct voltage D is applied to the grid G situated in the potential loop of the resonator relatively to the cathode, while to the tube A a positive or negative voltage is applied which is below the grid voltage, so that within the space between G and A a brake field is produced. If the tube A is given a negative voltage relatively to the cathode, this brake field will produce a reversal of the electrons in the space between G and A. Flows of electrons of this description will allow of intensively exciting an electron tube with hollow space resonator in accordance with Figs. la and lb. For the leading to and from of the oscillation energy, an energy circuit L, for instance in the neighbourhood of a. potential node may be coupled in a known manner. One of the conductors of the transmission line is then passed through the tube A with the aid of the seal 8:. At the free end of the energy circuit any desired loading resistance or an aerial T may be connected up.

Figs. 2a and 2b represent an arrangement which resembles that of Figs. 1a and lb, with the only difference, that instead of the tungsten cathode an indirectly heated oxide cathode K1 has been provided and instead of the round grid bars flat grid bars G1, positioned radially, have been employed, allowing the electrons a convenient passage and embodying a further advantageous effeet, as will be shown in the following.

If in arrangements in accordance with Figs. 1a and 1b the voltage D at the grid and the voltage at the brake electrode is changed and in the condition plane in accordance with Fig. 3 those are defined within which the tube oscillates, generally two, but frequently also more oscillation ranges x or X will be obtained extending along the curves Y or Y. For voltages within the crosshatched areas and bordered by X and X the tubes in accordance with Fig. la oscillate with a frequency whose half wave length very accurately coincides with the distance between the plates Q1, Q2, i. c. with the length of the Lecher system closed at both ends. The curves Y or Y on which a change of the voltage F will exhibit the maximum oscillation amplitude, may be computed in excellent coincidence with the experiment. The basis for the computation of these curves Y or Y is furnished by the conception that electrons emerging from the grid G and reversing in the space between G and A are caught by the grid after a single reciprocating path with relatively low speeds. The presupposition of such an electron motion is, that the hollow space serving as resonator attains alternating amplitudes of its oscillation, at which the electrons are deprived of the kinetic energy, which they possess when entering the hollow space, during a single reciprocating path. These high alternating amplitudes of the oscillation and the simple electron motion resulting therefrom, i. e. the single reciprocation path in the field space of the resonator instead of the otherwise occurring multiple electron swingings are the consequence of the damping-free design of the resonator, i. e. the consequence of choosing as resonator a closed hollow space, from which stray radiation cannot escape.

The excellent coincidence of computation and experiment with regard to the curves Y or Y along which maximum oscillating amplitudes will show themselves in connection with a change of the voltage F, proves, that the voltages F and D must be so selected, that the electrons require on their path in the space between grid and brake electrode a time of motion of approximately an integral multiple of the period of the oscillation to be excited, the time of motion in Fig. 3 for the oscillation range X being approximately equal to the period of the oscillation to be excited and for the oscillation range X being about double that of the period of the oscillation to be excited.

Owing to the fact that the grid, as shown in Figs. 2a and 2b consists of flat bars placed radially, electrons returning from the reversal surface to the grid are prevented from reentering the grid cathode space in a disturbing manner. The electrons emanating from the cathode and crossing the grid G are subject to deviations in a peripheral direction owing to the fact, that generally they do not enter the resonator accurately along the middle plane between two adjoining grid bars. These deviations cause the electrons returning from the reversal surface not to rush towards the grid accurately radially, but they cause them to hit the grid with a peripheral speed component. The structure of the grid composed of flat bars mounted radially, thus ensures a safe collection of the returning electrons.

The employment of a closed hollow space, which does not allow stray radiation to escape, as resonator is independent of the kind of exciting flow of electrons employed. Instead of the tube represented in the Figs. 1a, lb, 2a, 2b in brake field connection, a magnetron tube, e. g. with a magnetic field extending parallel to the cathode, could be employed.

It is, of course, possible without any difllculty whatsoever to excite tubes in accordance with Figs. 1a, lb, 2a, 2b by a suitable selection of the flow of electrons, particularly by a suitable ad- Justment of the time of motion in any desired harmonic vibration of the Lecher system instead of in the fundamental wave.

In case of a tube intended for transmission the voltages will have to be so adjusted in accordance with Fig. 3, that the condition point is situated in the vicinity of one of the lines Y or Y at which maximum oscillation amplitude will be produced. If a tube in accordance with Figs. 1a to 2a is intended for receiving purposes, the voltages, in contradistinction thereto are to be so selected, that the condition point in Fig. 3 is situated near the edge of one of the oscillation ranges X or X. If, moreover, the voltage is so selected as to be practically zero, particularly only very little negative in contrast to the cathode, a direct current will be produced over the brake electrode A in consequence of the excited oscillation through a wave to be received. When receiving a modulated wave the demodulation may be effccted through the medium of this rectifier effect.

The tubes in accordance with the present invention are of particular interest for the province of the centimeter and the decimeter waves.

I claim:

1. A device for generating, receiving, or amplifying ultra-short waves comprising an electron tube composed of a cathode, an inner conductor concentrically mounted about said cathode, and an outer conductor concentrically mounted about said inner conductor, said inner and outer conductors being separated to form an oscillating I space, said outer conductor consisting of a solid wall metallic tube, said inner conductor consisting of a solid wall metallic tube formed in two solid wall parts spaced from each other by a grid section, said parts of said inner conductor being separated from each other a distance materially less than the axial length of the space between said inner and outer conductors.

2. An evacuated electron tube having two solid wall cylinders forming electrodes one within the other and spaced to form an oscillating chamber therebetween, a grid forming part of the inner electrode, a cathode within said inner electrode, and means connecting each end of one electrode to a like end of the other electrode, said means sealing said chamber.

3. A tube as in claim 2, said means comprising flanges secured to the ends of said electrodes and means sealing said flanges in spaced relation.

4. A tube as in claim 2, filling means within said inner electrode limiting the oscillatory system within said inner electrode to a detuned frequency with respect to the frequency in said chamber.

5. An electron tube, comprising two coaxial hollow metal cylinders, capacitatively short circuited wall portions connected to the ends of said cylinders and in spaced relation to each other, said cylinders being spaced away from each other and enclosing therebetween a space, the outer cylinder being a solid wall electrode, the inner cylinder having openings therein, the portions of said inner cylinder between said openings being a grid, a cathode mounted coaxially within the hollow cylinder adjacent said openings, members connected with the cathode and forming shortcircuit condensers with the inner hollow cylinder, the inner ends of said members delimiting a space around the cathode which is detuned relative to the resonator space, metal plates connected to said members, and a glass-metal Joint connecting said plates and said wall portions vacuum tight.

6. An electron tube, comprising two coaxial hollow metal cylinders, capacitatively short circuited wall portions connected to the ends of said cylinders and in spaced relation to each other, said cylinders being spaced away from each other end enclosing therebetween a space, the outer cylinder being a solid wall electrode, the inner cylinder having openings therein, the portions of said inner cylinder between said openings being a grid, an indirectly heated oxide cathode mounted coaxially within the hollow cylinder adjacent said openings, members connected with the oathode and forming short-circuit condensers with the inner hollow cylinder, the inner ends of said members delimiting a space around the cathode which is detuned relative to the resonator space, metal plates connected to said members, and a glass-metal joint connecting said plates and said wall portions vacuum tight.

'7. An electron tube, comprising two coaxial hollow metal cylinders, capacitatively short circulted wall portions connected to the ends of said cylinders and in spaced relation to each other, said cylinders being spaced away from each other and enclosing therebetween an oscillating space, the outer cylinder being a solid wall electrade, the inner cylinder having a grid portion consisting of rods mounted parallel with the axis oi the cylinders, a cathode mounted coaxially within the hollow cylinder adjacent said grid, members connected with the cathode and forming short-circuited condensers with the inner hollow cylinder, said members delimiting a space around the cathode which is detuned relative to the oscillating space, metal plates connected to said members, and a. glass-metal joint connecting said plates vacuum tight with the wall portions of the outer cylinder, whereby the outer cylinder and said plates form a vacuum receptacle.

8. An electron tube, comprising two coaxial hollowmetal cylinders, capacitatively short circuited wall portions connected to the ends of said cylinders and in spaced relation to each other, said cylinders being spaced away from each other and enclosing therebetween an oscillating space, the outer cylinder being a solid wall electrode, the inner cylinder having a grid portion consisting of radially positioned fiat rods mounted parallel with the axis of the cylinders, a cathode mounted coaxially within the hollow cylinder adjacent said grid, members connected with the cathode and forming short-circuit condensers with the inner hollow cylinder, said members delimiting a space around the cathode which is detuned relative to the oscillating space, metal plates connected to said members, and a glassmetal Joint connecting said plates vacuum tight with the wall portions of the outer cylinder, whereby the outer cylinder and said plates form a vacuum receptacle.

9. An electron tube, comprising two coaxial hollow metal cylinders, capacitatively short circuited wall portions connected to the ends of said cylinders, said cylinders being spaced away from each other and enclosing therebetween a space, the outer cylinder being a solid wall electrode, the inner cylinder having openings therein, the portions between said openings being a grid, a cathode mounted coaxially within the hollow cylinders adjacent said grid, members connected with the cathode and forming shortcircult condensers, with the inner hollow cylinder, metal plates connected to said members, and a glass-metal joint connecting said plates vacuum tight with the wall portions of the outer cylinder, whereby the outer cylinder and said plates form a vacuum receptacle.

10. An electron tube, comprising two coaxial hollow metal cylinders, capacitatively short circuited wall portions connected to the ends of said cylinders, said cylinders being spaced away from each other and enclosing therebetween a space, the outer cylinder being a solid wall electrode, the inner cylinder having openings therein, the portions between said openings being a grid, said grid consisting of a plurality of radially disposed flat rods mounted in said opening, a cathode mounted coaxially within the hollow cylinders adjacent said grid, members connected with the cathode and forming short-circuit condensers, with the inner hollow cylinder, metal plates connected to said members, and a glass-metal joint connecting said plates vacuum tight with the wall portions of the outer cylinder, whereby the outer cylinder and said plates form a vacuum receptacle.

11. An apparatus for exciting ultra-high frequency electro-magnctic oscillations, comprising an electron tube consisting of two coaxial metal cylinders spaced away from each other, capacitatively short-circuited wall portions mounted in spaced relation to each other on the ends of said plates and said wall portions vacuum tight.

12. An electron tube comprising, a solid wall electrode, a perforated electrode within said first electrode and in spaced relation thereto, condenser plates connected to said electrodes, insulating members between said plates, said plates and said electrodes forming a hollow member electrically conductive substantially all around at least on its inner side, a cathode outside said hollow member adjacent the opening of said perforated electrode and leads connected to said electrodes.

13. An electron tube, comprising two coaxial hollow metal cylinders, capacitatively short circuited wall portions connected to the ends of said cylinders and in spaced relation to each other, said cylinders being spaced away from each other and enclosing therebetween an oscillating space, the outer cylinder being a solid wall electrode, the inner cylinder having openings therein, the portions of said cylinder between said openings being a grid, a cathode mounted coaxially within the hollow cylinder adjacent said openings, members connected with the cathode and forming short-circuit condensers with the inner hollow cylinder, the inner ends of said members delimiting a space around the cathode which is tuned to a higher specific frequency than said oscillating space, metal plates connected to said members, and a glass-metal joint connecting said plates vacuum tight.

14. An electron tube, comprising two coaxial hollow metal cylinders, capacitatively short circuited wall portions connected to the ends of said cylinders, and in spaced relation to each other, said cylinders being spaced away from each other and enclosing therebetween an oscillating space, the outer cylinder being a solid wall electrode, the inner cylinder having a grid portion consisting of rods mounted parallel with the axis of the cylinders, a cathode mounted coaxially within the hollow cylinder adjacent said grid, members connected with the cathode and forming short-circuit condensers with the inner hollow cylinder, said members delimiting a space around the cathode which is tuned to a higher specific frequency relative tosaid oscillating space, metal plates connected to said members, and a. glass-metal joint connecting said plates vacuum tight with the wall portions of the outer cylinder, whereby the outer cylinder and said plates form a vacuum receptacle.

WALTER nlummacn.

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