US2088653A - Electron tube and circuit therefor - Google Patents

Description

g- 1937- H. E. HOLLMANN 2,088,653

ELECTRON TUBE AND CIRCUIT THEREFOR Filed March 8, 1934 INVE NTQR HANS E RlCH HOLLMANN ATTORN EY Patented Aug. 3, 1937 UNITED STATES 7 2,088,653 ELECTRON UBE AND CIRCUIT THEREFOR Hans Erich Hollmann, Berlin, Germany, assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic in. b. H., Berlin, Germany, a' corporation of Germany Application March 8, 1934, Serial No. 714,651

In Germany March 8,1933

1 Claim. (Cl. 250-36) When a triode tube is operated in what is known as a Barkhausen-Kurz circuit arrangement (retarding-field scheme) the grid is impressed with a high positive potential, Whereas the outer electrode is connected with a'negativ'e or slightly positive potential; 1 The electrons'accelerated by the said high grid potential andfiy ing through the grid are retarded in the opposing field of the outer electrode for which reason this electrode has come to be called the .retaming-electrode. Supposing that a cathode is used which is operating inside the range of saturation, then it will be found that the retarding characteristic which shows the dependence of the current of the retarding electrode upon the retarding field voltage'is a mirror picture of the grid characteristic being the inter-relationship between the grid current and the. retarding fieldvoltage.

This so-called Barkhausen-Kurz short wave circuit scheme may be employed for-the generation, amplification, and rectification of any'desired frequencies. Compared with the usual connection of tubes with a positive outer electrode (anode) and a negatively biased grid, these two electrodes, in the Barkhausen-Ku'rz circuit, have not only transposed or interchanged theirfunc tions as regards potentials, but it has also been suggested to impress the input voltage between the cathode and the said retarding electrode, and to connect the output circuit withth e grid. But this scheme is attended withthisdrawback, that the internal resistance between cathode'and retarding electrode is comparatively low, indeed, that it has practically a Value of onlya few hundred ohms, and this as a result means a considerable load on the source furnishing the control potential.

The present invention is based upon. the idea of increasing the inner tube resistance which is in parallel relation with respect to the input circuit by connecting two Barkhausen-rKurzQshort wave tubes in series. Asa consequence; the internal resistance is doubled, while the loadof the source of the control voltage isreduced one half. T

A better understanding oftheinventiohfmay be had by referring to the following detailed description, which is accompanied by drawing wherein:

Fig. 1 shows a fundamental circuit arrangement in accordance with the present invention;

Figs. 2 and 3 illustrate, .by way of example, two difierent forms of electron tubes having a plurality of anodes with a common grid and cathode for efiecting the object of the invention;

Fig. 4 illustrates a further form of electron tube wherein shields are provided between two cylindrical anode sections to prevent interaction is varied inversely as the grid current.

between electron streams within the different sections respectively; 1

Fig. 5 shows a modification of the shielding arrangement of Fig. 4 where, in this case, semicylindrical anode segments are employed and where the shields themselves are disposed in a planewhich intersects the axis of, the cathode and liesin the gaps between the anode segments;

' Fig. 6 shows a combination of the shielding arrangement of Fig. 5 with a capacitive collar arrangement externally of the tube envelope for varying the effective inter-electrode capacity;

and

H fFig. 7 shows in cross section a variation in the source of grid voltage Eg. A circuit arrangement of this kind is serviceable both for the generation as well as the reception of ultra short waves.

The two retarding electrodes work in phase opposition (push-pull) and they determine the phase of the potential variations on the electrodes in the two tubes. In the case of a wave generator, the energy is. delivered by the coupling "of an antenna or an energy feed lead in the retarding-electrode circuit. If the arrangement is to be used for receiving, the retarding-electrode voltage must be so adjusted that the working point comes to lie about the kneeof the retarding? characteristic.

It is among the features of this invention that Whether the circuit is to be used as a detector,

as an amplifier, or otherwise, the tube characteristics are to be adjusted in such manner that the anode current versus anode voltage graph forms a mirror picture of the graph constituting the grid current versus anode voltage. When the adjustment has been suitably made it is found that the space current, as measured by the number of electrons emitted from the cathode, is maintained constant, while the anode current It is to be understood, however, that when operating a tube in this manner the operating range is kept within suitable limits of saturation. The tube when used as a detector is thus enabled to produce rectification in the grid circuit when radio frequency components are applied in a pushpull manner to the anodes or retarding electrodes.

As a further development of the said basic idea of the invention a special form of electron tube is here suggested which is characterized by a joint cathode and a joint grid, but two or more retarding electrodes or anodes. However, in order that such a tube may be rendered useful for the present purposes, it must measure up to other requirements, and it distinguishes itself thereby from other similar tubes disclosed in the earlier art. In order thatthe effect of all anodes may be the same, and in order that also the length of the electron paths may be alike, it is necessary that all of the retarding electrodes or anodes should be located upon the same circular or cylindrical form. "In order to design a push-pull arrangement at least two retarding electrodes must be present. For the sake of insuring uniform field distribution it may also be desirable, however, to provide a still greater number of retarding electrodes and to connect the same in two groups. The inter-connections between these groups are most suitably established within the vacuum vessel proper, it being understood, moreover, that strict symmetry is essential for the proper function of such tubes. p

The. formation of the various retarding electrodes is possible in two different ways. .They are either formed by sections at right angles to the cylinder axis so that two or more co-axial cylinders of like diameter result (Figure 2), or else the cylinder surface is divided, by sections laid through the axis of the cylinder, into segments (Figure 3). In order that the conditions of symmetry may be improved in the former case it may under certain circumstances be advisable to bring the midpoint of the cathode out of the glass bulb and to connectthe'two halves of the cathode in parallel. Fundamentally speaking, it

- is not necessary that the various retarding electrodes should be of like size, though when constituting the two electrode groups this point should be borne in mind that each of the two groups should have the same total surface or area. It would thus be possible, for instance, to dispose four co-axial cylinders of like length and like diameter adjacent to one another and to connect the first and the third, and the second and the fourth; or else only three cylinders could be provided of which the central one has a length twice that of the two outers, with the latter two being united together.

Whether this latter arrangement comprising co-axial cylinders, or the one involving segments parallel to the axis, is to be used will depend to a certain degree upon the kind of the oscillation system to be connected with the tube. Where very short waves are dealt with, say, of a length below one meter, it has been found that a parallel wire system is suitable as the oscillation circuit. In this instance, segmental subdivision is particularly useful, with the retarding electrodes being then placed in the voltage loop of a parallel wire system, i. e., the retarding electrodes are at high potential points on a two wire orlecher wire system, such as shown in Figs. 3 or 6.

To insure undisturbed operation'of the pushpull scheme it is important that the electron paths between the cathode and the two retarding electrodes (or groups thereof) should not interengage. In order to prevent this from occurring the suggestion is made according to this invention to'dispose shields or screens in the space between the various retarding electrodes, said shields or screens consisting preferably of metal and being kept at a constant potential. For this purpose the shield is united, for example, with the grid or the cathode.

Figure 4 shows an exemplified embodiment of an arrangement of the said sort. K is the incandescent cathode, G the grid electrode, and BI, B2, denote the two retarding electrodes having the shape of co-axial cylinders. Between these is disposed the metallic shield S which consists of a disk of circular form and which is united with the grid.

In Figure 5 this scheme has been applied to a tube furnished with segmental retarding electrodes. Under certain circumstances, it may be very desirable toemploy a unitary metallic gridsupporting element S which of itself constitutes the shielding surfaces.

The two retarding electrodes (or groups thereof) are to be regarded as the coats or plates of a condenser between which a certain potential prevails. According to another object of this invention, the said capacity is utilized for the purpose of tuning the oscillation circuit between the retarding electrodes to resonance. In order that the effective capacity may be varied, recourse is bad according to this invention to an arrangement as shown in Figure 6 which has proved preferable for short wave work. The two retarding electrodes El, B2 are located at close proximity to the inner wall of the cylindrical glass bulb Z or i are made to bear directly thereon. 'A metallic collar T is mounted on the outside of the glass of which are formed, on the one hand, by the said metallic tube, and, on the other hand, by the retarding electrodes BI and B2. It can be seen. directly that the capacity of these condensers is increased, the farther the said tube T is shifted over the electrodes. in Fig. 6 also includes preferably a pair of shield plates S lying in a plane which intersects the axis of the cathode and passes through the gaps between the anode segments.

Instead ,of a metal tube T, metallic rotatably mounted on the glass bulb could be arranged as shown in Figure 7. If these are turned in a direction as indicated by the arrow p, the capacity between the retarding electrodes Bl B2,

The structure shown coats S and the coats S will be obviously altered. The

number of the outer electrodes S should suitably be the same as the number of retarding electrodes B.

I claim:

.An electron discharge device having a vacuumtight envelope, a centrally disposed linear cathode, a cylindrically formed screen electrode completely surrounding said cathode, a plurality of anode segments having cylindrical surfaces of the same radius co-axially disposed about said screen electrode, shielding means interposed between adjacent edges of said anodesegments and connected to said screen electrode, an inductive circuit interconnecting said anode segments, and.

means including a metallic collar adjustably fit-

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