US1722094A - Electric wave translation system - Google Patents

Description

July 23, 1929. A, ENSEN 1,722,094

ELECTRIC WAVE TRANSLATION SLS'TEM- Filed Dec. 1924 6. Marisa/7 aw m Patented July 23, 1929.

UNITED STATES OFFICE.

AXEL G. JENSEN 10F RED BANK, NEW JERSEY, ASSIGNOR"TO WESTERN ELECTRIC COMPANY, INCORPORATED, 015 NEW YORK, N. Y., A CORPORATION OF NEW Y ORK.

ELECTRIC WAVE TRANSLATION SYSTEIE.

' Application filed December 4, 1924,. Serial No. 753,813.

This invention relates to electric wave translation systems and more particularly to space discharge tube systems wherein the pro-' duction of undesired oscillations is prevented.

5 It is now well known that, in a space dis charge tube system, oscillations will be generated when the input and output circuits of the tube contain reactances of the proper kind and of the proper value. These oscillations- 0 are generated by virtue of the amplifying action of the tube, and by virtue of the coupling afforded between these circuits by the inherent capacity between the tube electrodes and the tralization may provide a new-path in which parasitic oscillations may be generated. The

invention to be hereinafter described provides a solution of this problem. A

An object of the invention is to prevent the generation of parasitic oscillations in wave translation systems, particularly those including space discharge devices.

Another object is to so alter the reactance of wave translation systems or space discharge tube systems as to avoid a condition favorable to the generation of oscillations.

A further object is to prevent the How of oscillatory waves through specified paths in a space discharge tube system.

An additional object is to prevent the flow of undesired oscillatory waves by impeding them.

-A feature of the invention is a space discharge tube system providedwith an impedance element for preventing the flow of oscillatory currentsin the system.

Another feature is a space discharge tube system provided with paths including resistance, whereby an oscillatory-condition of the system is avoided.

A further feature is an arrangement of space discharge tubes having the associated circuits therewith so balanced that the generation of parasitic oscillations is prevented. v The present invention involves certaln prlnciples which are applied to systems of space discharge tubes to obtain the objects above enumerated and others. In order to prevent undesired oscillations in systems of space discharge tubes, the circuits included therein may be so designed that paths, wherein oscillatory currents tend to flow, will contain an element or elements for impeding oscillations. For example, the impedance element may be a resistance. In another instance, oscillations may be prevented by providing reactance elements in certain paths of the system such that no'tendency" for oscillations to buildup will be present. As an example of this, a space-discharge amplifier may have either its input or output circuit or both circuits balanced by means of a capacity arranged to neutralize the effect of interelectrode capacity of thespace discharge tube. In arrangements ofthis kind, heretofore known, parallel paths between the tube input and output circuits are provided wherein oscillations may be generated. This invention provides means for preventing oscillations in these paths by providing, for example, reactance of a particular kind at certain points therein where reactance of a different kind would be required to bring about a condition favorablev to the generation of oscillations. Again, by properly balancing both the input and output circuits of a space discharge tube, parasitic oscillations are prevented.

The invention is described in detail in the following specification read in connection.

Fig. 1 represents schematically a space discharge tube system having an oscillation impeding element. r

' having balanced input and output circuits.

Fig. 5 represents anamplifier having an output circuit provided with capacity reactance for preventing oscillations Fig. 6 represents a modification of the sys tem shown in Fig. 5.

In Fig. 1, a space discharge tube 10 having anode, cathode and control electrodes 11, 12 and 13, respectively, is arranged in a circuit including an impedance element 14 and a capacity. .element 15 for, preventing oscillations inthe system. The space discharge tube 10 has an input circuit connected to its con- .trol electrode and cathode which includes a resonant circuit 17, comprising a condenser v the anode 11 by a path including condenser 15. The output circuit of tube lO extends from anode 11, through an inductance 24 and a source of space current 23 to its cathode. The condenser 25, shown in dotted lines, represents the inherent capacity between the anode 11 and control electrode 13 of tube 10 plus the capacity'of the leads connected to these electrodes.

Waves to be amplified may be supplied to the input circuit through the winding of coil 19 which also represents atransformer, a

wave, collecting conductor-such as a loop antenna, or similar device. Amplified waves may be transmitted toany suitable apparatus external to the system by suitable coupling means associated with the coil 24-.

In amplifying systems as ordinarily arranged the capacity 25, shown in dotted lines, by providing a feed back path from the anode to the control electrode of the tube, permits the transfer of waves from its output circuit to its input circuit which may cause theproduction of undesired oscillations. In an effort to neutralize the effect of capacity 25, the anode 11 is connected to the cathode 12 by a path including the balancing condenser 15. This path is in parallel with that including the capacity 25. Varying currents "flow in the two parallel paths through the ancing capacity 15 in parallel with thetube respective halves ofcoil 1 9 in such manner as to induce electromotive forces therein which are theoretically equal and opposite, so that no potential variations are impressed upon control electrode 13. V 4

In practice, it has been found that the balcapacity 25 constitutes new paths in which oscillations may be generated, especially, when tubes of high amplifying power are employed, unless additional means is pro-' duced to prevent their occurrence. This fact will be understood when .we consider that the .-input circuit of tube 10 contains an inductance, representedby the difference between the self-inductance of coil 19 and the mutual inductance between its two halves, and the output circuit contains the inductance 24. It is well knownthat a space discharge tube system, including inductive reactances in both the input and output circuits and capacity coupling between them, will generate oscillations at certain frequencies for-which these reactances cooperate to constitute a resonant circuit. I

In order to prevent these reactances inherent in the system from producing oscillations the resistance 14 is provided. This by currents tendin to generate oscillations and, by offering a high impedance to these currents, prevents them from reaching an amplitude such. that the system will oscillate.

Resistance 14 may be of such value as not only to prevent oscillations but also to cause modulation or demodulation to take place in the input circuit. The tube 10 then becomes a modulator or detector as ,the case may be.

The system of Fig.2 is similar to that of Fig. 1 withthe exception that resistance 14 is replaced by two resistances 26 and 26 connectedrespectively between the cathode of tube 10 and the two outer terminals of the winding of coil 19. These resistances are included in the parallel paths between the anode and cathode and are of such value as to greatly impede the flow of oscillatory waves and, if desired, to cause the tube to operate as a distorting device for the impressed Waves, whereby detection or modu-' lation' of. these waves may be, effected. WVhether or not detection or modulation takes place depends upon the value of the resistresistance is included in the path traversed,v

ances which may be varied until they are of a value suitable for the purpose desired.

In the arrangement shown in this figure the inductance of coil 19 is excluded from the parallel paths including capacity 25 and resistance 26 on the one hand and condenser 15 and resistance 26 on the other. So far as concerns the energy fed back from the output circuit to the input circuit, there is no inductive rcactance included in these paths on the input side of tube 10, hence they are effectively aperiodic. A condition such as to preclude the generation of oscillations therefore exists in the circuit.

In Fig. 3 the inductance of the coil 19 is also excluded from the parallel oscillatory paths which contain the condenser 27shunted by resistance 29 and condenser 28 shunted by resistance 30 in addition to the capacity 25 and condenser 15 respectively included in these paths. Since, in the portions of the.

parallel paths on the input side of tube 10, there is included noinduc tive reactance, oscillations cannot be enerated in these paths. Resistance 29 provid the control electrode andcathode of tube 10 around the condenser 27. A similar resistance 30 is connected in'shunt to condenser 28 for balancing the resistance 29. By adjusting condensers 27 and 28 an accurate balance of the parallel paths may be obtained, and the input circuit maybe tuned to the frequency of the impressed waves.

es a leak path between .nected to the control electrode.

An additional arrangement for preventing oscillations, comprising parallel paths between the cathode and anode of a space discharge tube, is illustrated in F ig. 4. Oscillations are prevented in this arrangement by balancing both the input and the outputcircuits of the tube.

Resonant circuits 17 and 17 are included respectively in the input and output circuits of tube 10, and these resonant circuits include as their inductive elements the coils 19 and 19, respectively. Condenser 15 is arranged to balance the capacity 25 between the anode and control electrodes, as already explained. Condensers 15 and 15 provide two additional parallel paths complementary to the parallel paths through capacities 25 and 15 whereby oscillation currentstending to flow therein are neutralized. Each of these condensers has a capacity substantially equal to the capacity 25 between the anode and control electrode. Since both the input and output circuits of the tube are balanced, it is im-' possible for energy from the output circuit to be supplied to the input circuit in such man ner as to establish parasitic oscillations.

In Fig. 5 an amplifier system is illustrated in which only the outputcircuit is balanced and the inductance of resonant circuit 22 is excluded from the arallel paths between the anode and control e ectrode to prevent oscillations,'as was done in the input circuit in.

Fig. 3. Condensers 27 and 28 render the parallel paths between the anode and cathode of tube 10 in this figure capacitively reactive so far as the output circuit of the tube is concerned, hence oscillations cannot be generated in these paths because, as explained above, of the lack of inductive reactance therein on one side of tubelO. The choke coil 37 is designed to have a very large. inductance so that for frequencies at which oscillations might otherwise occur the resultant reactance of the output circuit is capacitive. In other words the inductance is made so large that the reactance is substantially pure capacity reactance. One terminal of the balancing condenser 15, in this instance, is connected to the terminal of condenser 28' remote from the cathode, while its other terminal is con- This condenser functions in the same manner as the corresponding condensers in the previous figures.

I A second space dischargetube amplifier 35 is here shown with its input circuit capacity coupledto the output circuit of tube 10 for obtaining a step-up of voltage of translated waves. a It will be noted that the input circuit of tube 35 isconnected across both condensers 27' and 36, which are included in series in a. closed loop including. the resonant circuit 22 and condenser 28', whereas theoutput'circuit of tube 10 is only connected across-condens-- er 27; y r

"By this arrangement there is provided a. step-up in voltage between the output circuit of tube 10 and the input circuit of tube 35. It is thus evident that condenser 27 functions not only as means for preventing singing in the system, but also as a voltage multiplying means. I I

The amplifier circuit illustrated in Fig. 6 is very similar to that illustrated in Fig. 5, but.

the input circuit is balanced, and the output circuit is provided with only capacitive reactance so that an oscillation condition is avoided.

In particular instances the invention has i been found effective when employed with tubes having equipotential cathodes, i. e. cathodes heated by induction or heat radiation such as described in the patent to Nicolson 1,459,412 granted June 19, 1923, but this statement should not be taken to indicate that the utility of the invention is in any manner limited to a particular type of tube.

Although, for the purpose of explaining the invention, it has been described in connec-i tion-with certain specific circuit arrangements, the principles involvedare capable of general application to a range of equivalents not specifically described; but which will readily occur to persons skilled in the art, and consequently this invention is to be limited only as indicated by the scope of the appended claims.

What is claimed is:

1. In a space discharge tube system, a three electrode space discharge tube, input and output circuits for said tube, means for balancing the capacity between certain electrodes of said tube to prevent oscillations at frequencies near the frequencies of. the currents impressed on said input circuit, and a1 non-reactive impedance cooperating with said balancing means to prevent the generation of oscillations in the s stem at frequencies above the frequencies 0 the currents impressed on said input circuit. it I 2. In a space discharge tube' system, a three electrode space discharge device, a resonant circuit, electrodes of said devlce being connected to electrically separate points in said resonant circuit,'means connected to balance the capacity between two of said electrodes to prevent oscillations at frequencies near the said paths cooperating to preventthe production of oscillations having a frequency near the frequency of the currents impressed on the discharge tube and oscillations having a fre quency above the frequency of the currents impressed on the discharge tube,

4. In a circuit including a space discharge tube having an input circuit and an output circuit, means for preventing singing caused by the internal capacity of the tubes, comprising a capacity connected between said input and output circuits, and means comprising a resistance included in said input circuit in the path of waves tending to establish oscillations for preventing the generation of currents having frequencies different from the frequencies of the currents impressed on the tube.

5. In 'an amplifier, a space discharge tube having three electrodes and circuits associated therewith for amplifying high frequency waves, said amplifier including a plurality of paths for waves tending to produce sustained 9 oscillations, an impedance in one of'said paths of one kind adapted to prevent oscillations having a frequency near the frequency of the currents impressed on the amplifier, and an impedance in another of said paths of a difr 'fcrent kind adapted to prevent oscillations In witness whereof, I hereunto subscribe my name this 1st day of December, A. D. 1924.

AXEL G. JENSEN.

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