US2002191A - Oscillation generator - Google Patents

Description

Patented May 21, 1935 "STATES PATENT OFFICE q i j@ 2,002,191

OSCILLATION GENERATOR Rung e, Berlin, Germany assighor to I i Telefunken' G'esellschaftfiir Drahtlose. Telegraphic in. b. H., Berlin; Germany, a cor- Duration of Germany Application OctobenZS,

imsscaiza. 462.962

In GermanyNovember 2, 1928 q x a J r Tlnsinvention relates to oscillation generation and particularly to a regenerativelyconnected thermionic tube for producing continuous waves, in combination with a mechanical oscillating system coupled to the tube for frequency stabilization purposesr I 1 a It is known to be possible to create, bymeans of mechanical oscillating systems, frequency standards which surpass in constancy all electrical oscillation circuitsasto the ordergof mag- "nitude, In selecting materials suitable for such frequency standards it is, however, important toascertainthat the materials possess qualities which would malge possible, to interconnect the mechanical and electrical processes; On account of this condition only piezo-electric materials, such as quartz, and magnetic materials, such as steel, have been applied in the prior- ,art for frequency standards. Owing to these electromechanical qualities such a system in accordance with my invention may be regeneratively coupled over thermionic tubes and used as a transmitter ofa normal frequency. A The required piezo-electric or magnetic quality limits the number of materials suitable for frequency standards. Quartz has a high ternperature' coef ficientwith the result that the frequency varies rapidly with the temperature and steel displays frequently evidence of fatigue and of time-modifications caused by recrystallization. Other materials, although mechanically qualified, have so far not been applicable as frequency standards on account of the impossibility to transfer their mechanical actions into electrical actions. According to this invention, such a transfer of mechanical into electrical effects, and vice versa, is obtained by making use of the'dielectric qualities of insulators and of the conductivity of conducting material s. Thus one is not limited in the least in the choiceof materials.- It is; for instance; possible to use now fused quartz, the temperature coefficient of which is considerably lower than that of crystalline quartz and which is practically obtainable in pieces of any size although the material possesses no p'iezo-electric qualities. Conversion ,of the mechanical processes into electrical processes may be effected, by way of. example, according to the apparatus shown in the drawing inwhichz H i Fig. 1 illustrates one preferred embodiment of the invention; and

Fig. 2 illustrates a modification thereof.

In Fig. 1, the rod I, made of dielectric material, for example fused quartz, is tobe made to oscillate longitudinally in the. fundamental wave. ,To attainthis the middle of the rod is. placed between two electrodes 2, 2 which are connected across a source of constant potential (battery) 3-.and ,a resistance 4. The grid-filament circuit ofa thermionic tube 5 is connected in parallel with the resistance 4., The two ends of the rod project beyond twometal rings, one of which (6) is connected to. one terminal of the battery 3; the other (1); by wayof an oscillating circuit 8, to the other terminal of the battery 3. The battery 3 serves at the same time as .a' source for the plate potential of the thermionic tube. With this circuit arrangement the following process takes place: 5

Let us assume that the rod oscillates already on itsfundamental wave. This causes considerable compression and tension in the middle of the rod, with accompanying changing of the dielectric con- .stant of therod corresponding to its change in volume in this part; Hence, the capacity between the electrodes 2, 2 is changing in synchronism with the oscillations of the rod. Since the battery 3 maintains a constant potential, the current flowing in the circuit comprising battery 3, resistance 4,. and capacity 2, 2, is an alternating current which causes at the resistance a potential drop the frequency'of which is equal to that of the rod. This alternating potential controls, in a manner wellknown in the prior art, the plate current in the thermionic tube 5 and creates thereby an alternating potential in the oscillation circuit 8 resulting in an alternating potential component betweenthe rings 1 and 6 which are already supplied with a constant potential from the battery 3. The electric field between these two electrodes partially travels through the dielectric material of the rod, generatingin it a force which causes the rod to contract; If the potential between the rings 1 and 6 changes periodically, the rod is subjected, in addition to the constant contraction attributable to the action of the constant potential; to an alternately compressing and tensile force which; with a properly adjusted phase, maintains the mechanical oscillations. The proper phase may be obtained by selecting a proper phase angle for the resistance 4, proper polarity of the couplings 8, 9, and by tuning 8. The energy lost on account of internal friction in the rod is thereforereplaced by the thermionic tube 5. The rod oscillates like an undamped transmitter.

If the rod is not made of a dielectric material but of a conducting material the regenerative coupling may be accomplished according to Fig. 2. Two electrodes, l2 and I3, connected across a coil to the filament of the tube ll. From the filament of the tube II a lead extends by way of the plate potential battery 18 and an oscillating circuit [9.

to the electrode Ill which faces the other end'of the rod. The plate of the tube 11 is connected to the plate potential batteryli} by way of a coil l l,

coupled with the circuit 19. ,,The action of this circuit arrangement is aslfollows: A' longitudinal oscillation of the rod causes a periodical changing of the distance between the electrodes l2, I3 and the left end of the rod-20. The capacity between the electrode accordingly, and so will the capacity resulting from the series connectionof the two capacities.

The battery l5 maintains this resultant capacity at a constant potential; A variation of the two component capacities will therefore cause an alternating currentto flow in the circuit I2, 20, I3, I5, M. This alternating current induces a potential in the circuit 16 which is supplied to the grid of the tube IT. The resulting alternating plate current of the tube I l induces an alternating potential in the circuit 19 which becomes superposed upon the directcurrent potential maintained between the electrodes I2,-l3 and theelectrode ID by the battery H3. The electrostatic forces between l2, l3 on the one hand and'2fl on the other, and between H] on the one hand and Non the other, which cause tension in the rod, are thus periodically increased and diminished in intensity. ,With a proper phase selection, that is with the tuning ofthe circuits l9 and I6, theseforces actin such a manner as to maintain the existing oscillations.

In either of the above'circuit arrangements a thermionic tube is used to maintain the oscillations of a mechanical system. At any point of the thermionic tube, such as at the plate lead, alternating current energy maybe taken out, the frequency of which would be. determined-by the natural frequency a of the oscillating system. Hence, the described arrangements may also be utilized to generate alternating currents? Although the described circuit arrangements show only one thermionic tube it is in many instances advisable to employ an amplifier in the form of several cascade-arranged tubes, the first grid being supplied'with the oscillatingpotential caused by the mechanical oscillating system and the last plate lead supplying the energy which is to be fed back to the oscillating system. The advantage of employing several cascade arranged amplifying stages as compared to one single tube consists in the fact that owing to the much greater amplification, the couplings between the oscillating system and the amplifying system may be the reactions which the electrodes with their circuits exert on the-natural frequency of the mechanical system. I I

bratory body, said vibratory body being arranged when in a state of oscillation to produce a variation in potential across the armatures of that l2 and the rod 20 and between the electrode I3 and the rod 20 will vary i capacity which is connected across said input circuit for varying the potential of said input circuit, said variation in potential being amplified by said device to cause a variation in potential across said other capacity.

2. In a regenerative system for producing os- "cillations, an electron discharge device having input and output circuits, a condenser arrangement comprising a vibrating rod-like element vibrating longitudinally of its fundamental wave, a plurality of armatures at one end of said element, a single armature atthe opposite end of said element, a coil said input'circuit, a second coil across said plurality of armaturesand inductively coupled to said first coil, a third coil in said output circuit, and a fourth coil connected to said single armature in circuit'with said first coil and in inductive relation to said third coil, said vibratory element when oscillating being arranged to vary the capacity between said single armature and said other armatures.

8. In a system for producing oscillations having, in combination, an electron discharge device, input and output circuits for said device, a condenser arrangement for coupling said input and output circuits comprising a. single mechanically vibrating element, two armatures at substantially the opposite ends of said element, a circuit including an inductance and a source of potential connected between said last two armatures, said inductance being inductively coupled to said output circuit, said source of potential also being in said output circuit, and two armatures intermediate the ends of said element and separated thereby connected across said input circuit, said element being common to said four armatures.

4. A system for producing oscillations having, in combination, an electron discharge device, input and output circuits, means for biasing the grid of said electron discharge device, means for varying the potential across said input circuit comprising a condenser having fused quartz for a dielectric, a plurality of armatures for said condenser, at least two of which are coupled to said input circuit, and a connection coupling at least one other armature of said condenser with said output circuit, and a source of potential in said output circuit directly connected to said last armature.

5. A system in accordance with claim 2, characterlzed in this that said vibratory .element comprises electrical conducting material.

WILHELM RUNGE.

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