US2540019A - Amplifier valve for ultra-short waves - Google Patents

Description

Jan. 30, 1951 R. WARNECKE AMPLIFIER VALVE FOR ULTRA-SHORT WAVES Filed Aug. 3, 1946 INYENTOR ROBERT WARNEC/(E MAGNETIC FIELD AGENTS Patented Jan. 30, 1951 AMPLIFIER VALVE FOR ULTRA- SHORT WAVES Robert Warnecke, Paris, France, assignor to Compagnie Generals de Telegraphic Sans Fil, a corporation of France Application August 3, 1946, Serial No. 688,359 In France February 14, 1941 Section 1, Public Law 690, August 8, 1946 Patent expires February 14, 1961 4 Claims. (e1. 315--6) This invention relates generally to amplifier valves for ultra-short waves, and more particularly to electronic amplifier valves intended to operate at ultra-high frequency (in particular decimetric or centimetric electromagnetic waves).

The characteristics of the invention refer essentially to the particular methods of association of an electron discharge system employing the secondary emission, with a system of cavity resonators.

According to the present invention, one employs as an electron amplifier two cavity resonators of revolution about the same axis, which are connected by a metallic pipe, the form, structure and arrangement of which are such that certain of the constructional elements thereof are at the same time the electrodes of an electron multiplier, which means that the resultant apparatus considered as a whole as an amplifier for very short waves has two identical resonant circuits, the quality factor of which is greatly superior to that of the conventional oscillating circuits. The replacement of the latter by cavity resonators gives, in fact, a high quality factor which leads to small losses and to a large shunt impedance, otherwise all things being equal. This enables the best use to be effected, with very short waves, of the bunching of the electrons in the electron multiplier and consequently ensures the realisation of amplifier systems having a greatly improved total efficiency. Conjointly with the very Slight high frequency losses in the cavity resonator (and in the absence of losses by radiation), the amplifier system is then endowed with good stability of frequency.

There will now be described one method of producing cavity resonators which comply with conditions hereinbefore set forth (the embodiments hereinafter set forth being given by way of example only and being included in the invention like the principle itself of the association corresponding to the conditions provided for in the preceding explanation).

The construction of the above-mentioned identical cavity resonators according to the invention is such that some parts of each of them, separated from the other ones by insulating air tight joints may be permanently raised to a direct positive voltage with respect to the other parts without preventing the flow of high frequency current between the positive and the negative ones. To get this result, the form and surface of the insulating joints are such that their capacitance is great for the high frequency "underfconsideration. According to theinvention, the bottoms of these cavity resonators are provided with centrally located cathodes, yielding secondary emission electrons, which cross permeable electrodes, respectively situated at the 2 ends of the connecting pipe. These electrodes are made positive with respect to the said cathodes by means of the above mentioned joints. The high-frequency oscillations are maintained in both resonators by an oscillator suitably coupled to them.

Before examining any specific embodiments; corresponding to the preceding principles, two ob-. servations can be made:

(a) The electrode forming the control gridi must be placed in a part of the cavity resonator where the electric field of the waves is veryslight in such manner that to a large extent the method of vibration of the latter is not changed; and

(b) the said electrode will preferably be a simple ring (grid with single mesh) raised to a direct positive voltage with respect to the other parts of the cavity resonator, the action of this rin being combined with that of an external magnetic field. This field has a focusing effec on the electron beam.

The invention will be hereinafter described with reference to Figures 1, 3, 5, 6 and 7 showing both structurally and diagrammatically embodiments according to the conditions explained above.

Referring to Figure 1, R1 and R2 indicate two hollow metal chambers having in the example under consideration, a common wall P, bored with an aperture S. These chambers will, for example, be cylindrical boxes (straight, circular cylinders) the axis of revolution XX of which is normal to the circular metallic discs A1 and A2 at the centres thereof, these discs being constituted and treated in order to present a high power of secondary emission. The discs A1 and A2 form a portion of the ends of the boxes R1 and R2 but they are separated from the rest of the cavity resonator by above-mentioned insulating joints of material having large surface relative to its thickness. Through this joint, as a result of its great capacitance, will fiow the high frequency current circulating in the inner surface of the resonator. As regards the direct voltage, this joint will perfectly insulate the disc A1 from the rest of the resonator. A1 and A2 are both connected with the negative terminal of the battery V0, while the other parts of the cavity resonator, the permeable cathodes and the connecting pipe are connected with its positive terminal.

It will thus be seen that the system illustrated in Figure 1 is the equivalent of that illustrated in Figure 2 provided an inductive capacity system R'1 and R'z is made to correspond to each of the resonators R1 and R2, and its operation as an electron valve is the same. In order that the system can operate as an amplifier in the manner indicated in Figure 1, it is sufiicient for the cavities to vibrate in phase, that is to say, for the potentials Va to be added together in amount, their sign being the same (the difference of high frequency potential between. A1 and A2 being This means that when a positive charge appears on the face of the wall P which lies within the cavity resonator containin A1, the opposite face of P lying within the other cavity resonator is negative. This result will be attained by exciting each cavity suitably, for example by means of loops coupling the magnetic field and such as Bi and B2.

A load circuit may also be introduced in the same way.

Naturally, and this will also be the case for: the examples shown in Figures 3 and 4, it is to be implied that a focussing magnetic field is employed the lines of force of which are parallel to the axis produced by an externalcoil as-shown in Figure 3.

Figure 3 represents another modification in carrying the invention into effect which differs from the preceding one by the fact that the part of each cavity resonator which is at the direct potential V with respect to the others is reduced to that which constitutes or immediately surrounds the ringserving as a grid and surrounding. the beam. Ba and B4 are loops for coupling with the load Q. On the diagram the same references indicate the same elements as in the preceding figures of the drawings. The ring is shown held up by a disc connected by capacitive joints to the sides f1 and f2 of the resonators R1 and R2. The capacitative connection is necessary in order that the electric field of the high frequency oscillations in each cavity does not undergo discontinuity at the edges of the disc and so that-the ring is raised to a high frequency pot'entia'l. If, furthermore, the latter did not exist, the vibration or" the cavity resonators might be unfavourably altered and possibly even prevented. This is furthermore the reason for the use of. a double cavity.

It will be noted that with the arrangements illustrated the action of the electrodes on the electronsdiffers from that of the ordinary transit time multiplier.

In the latter, it is presumed that the field acting on a. secondary electron emitted for example at the surface of the electrode A1... corresponds to the difference of high frequency potential between A1 and A2 and to the direct voltage V0 applied between G and A1, This action cannot exist in the valves described here where each cavity has its own oscillating field, the two fields interfering with each other in: the connectin pipe.

Referring to Figure 4 which corresponds to this case, the movement of the electrons is as follows: an electron emitted by A1 is subjected in its vicinity to the combined field determined by Tia/2 and by V11 in the cavity I- (thespace formed between A1 and G) and in the latter it remains subjected to this field alone. When it arrives in III (the space formed between G and A2) it is the same. The intermediate space II cannot be regarded as free from field. A bunching of electrons like that which is used in velocity modulation valves, takes place. In this case, the length e must be determined correspondingly in order that this effect may be favourable, that is to say, in order that it may produce a phase difference in the advantageous sense, with a suitable dimensioning; it will then be possible to increase the number of the electrons arriving in proper phase to be slowed down, which improves the efiiciency of the system.

An. example corresponding to a ring of great thickness c with respect to the distance d between the plates A1 and A2 is illustrated in Figures 5' and 6.

In the example illustrated in Figure 6, as in the example illustrated in Figure 3, the generated profile: of the cavities of revolution constitutin the resonator presents a retracted part.

Figure '7 again illustrates an embodiment. embraced by the present invention, the design of which, however, considered from the point of view of the system of the electrodes controlling the movement of the electrons, differs still more from the system of the usual electron multiplier. This system similar to that illustrated in Figure corresponds with a great thickness e of ring. as compared. with the distance A1A2, to the case of great penetration of the alternating field developed in a single cavity coupled galvanically to the plates Ar and A2.

In all the systems suggested, it will be understood that the difference of potential between the side plates of the resonators employed is produced by the circulation of currents induced by the groups of electrons approaching from the electrodes, the capacitative connections are thus provided in order to constitute a veritable shortcircuit from their point of view to the frequency of operation.

In a general way, the principal characteristic of the invention consists in the association of a resonant cavity or a collection of cavities with: a system of two secondary emission electrodes separatedby an accelerating electrode raised to a continuous current potential, the space between each emittin electrode and the electrode at the direct potential serving successively as acceleration space and as braking space for the electrons dueto a rockin movement.

It will be appreciated that according to the present" invention it is not thesame electronic mass or cloud which carries out a number of times consecutively an oscillating movement, but that there are always other electrons which travel over the path between: the one and the other emitting electrode. The rise in the emission by oscillating or rocking movement is only possible if the electrons always bombard the opposite electrode with a velocity which is sufficient to cause the secondary emission, which must be obtained by i-nterposing between the two emitting, electrodes. the resonator of whichv the natural period must be adjusted to the electronic time. of travel. Without such a. system of control of the field; the valve cannot oscillate and cannot even furnish. an appreciable emission current.

The invention is naturally capable of numerous modifications, other than. those expressly electrons to oscillate in said enclosure at a very high frequency, said enclosure being evacuated,

said means comprising secondary emission cathodes located at the bottom of said cavities facing the openings of said metallic conduit, insulating seals having surfaces large relative to their thickness arranged around the periphery between said cathodes and said metallic conduit, electronpermeable electrodes constituting the openings of said metallic conduit, means in circuit with and adapted to maintain said two electrodes at a fixed positive potential relatively to said cathodes, a very high frequency oscillator coupled to both said cavity resonators, a load impedance shuntingsaid cavity resonators relatively tq said oscillator, and focussing means comprising magnetic field means with its axis parallel to the common axis of said cavity resonators? 2. In an electronic amplifier, the combination, with two identical, cylindrical, cogaxial cavity resonators having a circular base ,aiid highlyconducting walls, and which are joined together by a cylindrical metallic conduit co-a'xial therewith so as to form a gas-tight enclosure, of means for causing electrons to oscillate from :one end to the otherbf said enclosure at a very; high frequency, said enclosure being evacuated, said means comprising a secondary emission cathode located centrally at the bottom of each cavity.

an annulus located at each end of said conduit, a source of direct current supply having the positive pole thereof connected to said conduit and the negative pole to both said cathodes, a very high frequency oscillator coupled to both said cavities symmetrically relatively to the center of said conduit, insulating seals having surfaces large relative to their thickness separating each said cathode from the corresponding one of said annuli, a load impedance shunting both said cavity resonators relatively to said oscillator, and focusing means comprising a magnetic field means with its axis parallel to the common axis of said cavity resonators.

3. The combination claimed in claim 2 wherein said two cavities have a'common frontal wall of relatively very small thickness, the length of said metallic conduit being limited to the thickness of said common wall and the electrodes thereof being united in a single electrode.

4. The combination claimed, in claim 2 wherein said two cavities have a common frontal wall and wherein said conduit, being of a length greater than the thickness of said common wall, is positioned symmetrically about said wall.

ROBERT WARNECKE.

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

UNITED STATES PATENTS Number Name Date 2,139,813 Farnsworth Dec. 13, 1938 2,295,396 George Sept, 8, 1942 2,337,214 Tunick h Dec. 21, 1943 2,409,417 Bull Oct. 15, 1946 2516303 7"???1'71'7':

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