US1884711A - Electric wave transmission system - Google Patents

Description

Oct. 25, 1932. A. G. JEN SEN ,88

' ELECTRIC WAVE TRANSMISSION SYSTEM Original Filed Dec. 4, 1924 A TTOPNE) Patented Oct. 25, 1932 UNITED STATES PATENT OFFICE AXEL G. JENSEN, OF RED BANK, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK ELECTRIC WAVE TRANSMISSION SYSTEM Original application filed December 4, 1924, Serial No. 753,813, now Patent 1,722,094, dated July 23, 1929. Divided and this application filed April 24, 1929. Serial No. 357,846.

This application is a division of application Serial No. 753,813, filed December 4,1924: patented July 23, 1929, No. 1,722,094.

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

It is now well known that, in a space discharge tube system, oscillations will be generated when the input and outputcircuits of the tube contain reactances of the proper kind and of the proper value. These oscillations are generated by virtue of the amplifying action of the tube, and by virtue of the coupling afi'orded between these circuits bythe inherent capacity between the tube electrodes and the external leads associated therewith. On the basis of this knowledge, systems have been devised in which the tendency to generate undesired oscillations is reduced, by providing a balancing capacity for neutralizing the tube electrode capacity.

It has been found, however, that when tubes of great amplifying power are employed, or when a large number of tubes are placed in tandem, a system arranged for capacity neutralization may provide a new path in which parasitic oscillations may be generated. The invention to be hereinafter described provides a solution of this problem.

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 flow 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 provided with impedance for preventing the flow of oscillatory currents in the system.

Another feature is a space discharge tube sistances therein.

system provided with paths including resistance, whereby an oscillatory condition of the system is avoided.

The present invention involves certain principles which are applied to systems of space discharge'tubcs 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 currentstend to flow, will con tain an element or elements for impeding oscillations. For example, the impedance element may be a resistance. In the specific form of the invention shown in the drawing, a space discharge amplifier has its input circuit balanced by means of a capacity arranged to neutralize the eiiect of interelectrode capacity of the space discharge tube. In arrangements of this kind, "heretofore known, parallel paths between thetube input and output circuits are provided wherein oscillations may be generated. The system shown in the drawing provides means for preventing oscillations in these paths by providing, for example, non-inductive re- One of these resistances is connected between the grid and the filament of the space discharge tube and the other is connected between the filament and the neutralizing capacity. The resistances form two arms of abalanced circuit which has the circuit configuration or form of a VVheatstone bridge and which has as its other two arms the plate-grid capacity of the tube and the neutralizing capacity.

The output diagonal of the circuit includes the plate filament space path. The input diagonal includes a timed circuit, and this tuned circuit and the arms are mutually exclusive, so that the balance lupon whi ch depends the neutralization of the coupling effect of the grid-plate capacity is independent of the potential gradient along the tuning capacity, whereas were port-ions of that capacity included. in arms of the circuit the balance condition would depend on the maintaining of a given ratio between those portions.

The invention is described in detailin the following specification read in connection with the attached drawing.

The single figure of the drawing represents schematically a space discharge tube system embodying a form of the invention.

In the drawing, a space discharge tube 10 having anode, cathode and control electrodes 11, 12 and 13, respectively, is arranged in a circuit including resistance elements 26 and 26 and a capacity element 15 for preventing oscillations in the system. The space dis charge tube 10 has an input circuit connected to its control electrode and cathode which includes a resonant circuit 17 comprising a condenser 18 and inductance 19, a polarizing battery 20, and resistances 26 and 26. Resonant circuit 17 may be tuned by adjusting condenser 18. The ends of the winding of coil 19 are connected to the cathode by a path including the grid polarizing battery 20and resistances 26 and 26. One terminal of the winding of coil 19 is connected to the control electrode 13, whereas its opposite terminal is connected to the anode 11 by a path including condenser 15. The output circuit of tube 10 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 a transformer, a wave collecting conductor such as a loop antenna, or similar device. Amplified waves may be transmitted to any suitable apparatus external to. the system coupling by suitable means associated with the coil 24.

In amplifying systems as ordinarily arranged the midpoint of coil 19 is connected to cathode 12, and the capacity 25, shown in dotted lines, by provid ng 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 the production of undesired oscillations. With such. systems'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 inthe two parallel paths through the respective halves of coil 19 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.

In practice, it has been found that in such systems the balancing capacity 15 in parallel with the tube capacity 25 constitutes new paths in which oscillations may be generated,

5 especially, when tubes of high amplifying power are employed unless additional means is produced to prevent their occurrence. This fact will be understood when I consider that the input circuit of tube 10 in such systems contains an inductance, represented by 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 known that a space discharge tube system, including inductive reactancesin 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.

The system shown in the. drawing prevents production of such oscillations. This system is similar to the prior art system'reierred to above, but it has not the above mentioned connection from the cathode to the midpoint of coil 19, and it has two resistances 26 and 26 connected respectively between the cathode of tube 10 and the two outer terminals of the winding of coil 19. These resist'ances 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 denser 15 and resistance 26' on the other. So far as concerns the energy fed back tubes having equi-potential cathodes, i. e., J1;

cathodes heated by induction or heat radiation such as described in the patent to Nicolson No. 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 connection with a certain specific circuit arrangement, the principles involved are capableof general application to a range of equivalents 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. A circuit of Wheatstone bridge configuration comprising an electric space discharge device having therein an anode-catln ode path and a control element anode path, said circuit having four arms and two diagonals with one of said paths in an arm and the other in a diagonal and with an impedance element external to said device included in each of said other arms, and a tuning circuit included in one of said diagonals, said tuning circuit and said arms bein mutually exclusive, and two of said impedance elements being resistances.

2. A circuit of l/Vheatstone bridge form comprising an electric space discharge device having therein an anode-cathode path and a control element anode path, said circuit having four non-inductive arms and two diagonals with one of said paths in an arm and the other in a diagonal and uiti an impedance element external to said device included in each of said other arms, and a tuning circuit included in one of said diagonals, said tuning circuit and said arms being mutually exclusive, and two of said impedance elements being resistances.

3. A Wheatstone bridge form of circuit comprising an electric space discharge device having therein an anode, a cathode, control element and an anode-cathode path and a control element-anode path, and having its control element-anode capacity balanced to prevent singing, said circuit comprising four arms and an input diagonal and an output diagonal, with said control element-anode path in an arm and said anode-cathode path in said output diagonal, a tuning circuit included in said input diagonal, said tuning circuit including a variable tuning capacity, said tuning circuit and said arms being mutually exclusive, and a noninductive resistor included in each of the two of said arms that are connected to said cathode, whereby singing through arms of the circuit parallel paths is prevented and balance of the circuit with respect to action of waves from the output diagonal upon the input diagonal is independent of the potential gradient along the tuning capacity.

4.. A space discharge tube system having a. three electroue tube, a tuning circuit comprising an inductance element and a capacity, electrodes of said. tube being connected to electrically separate points in said tuning circuit, means to balance the capacity between two of said. electrodes and additional means cooperating with said balancing means to suppress parasitic oscillations in the system due to said inter-electrode capacity in cooperation with said balancing means, said additional means comprising non-inductive resistors in shunt to said tuning circuit and connecting the cathode of said tube to said tuning circuit only at the ends of said inductance element.

5. An audion amplifier the impedance network of which is arranged in the form of an alternating current VVheatstone bridge having four balancing arms one of which is the grid-plate capacity of the audion tube, one of which is a capacity connected between the plate of: said tube and one terminal of the input circuit, one of which is a resistive impedance connected between the cathode of said tube and said terminal of the input circuit, and one of which is a resistive impedance connected between the grid and cathode of said tube.

6. In combination, a three-electrode audion tube having an inherent grid-plate capacity, a resistance connected between the grid and cathode of said tube, a resistance and a capacity connected in series in the plate circuit of said tube, and an input circuit one terminal of which is connected to the grid of said tube and the other terminal of which is connected to an intermediate point in the plate circuit impedance of said tube.

7. The combination with a three-electrode thermionic device having anode, cathode and grid electrodes and an input circuit, a resistance connected between the grid and cathode of said thermionic device, a connection comprising a second resistance and a capacity connected in series between the cathode and anode of said thermionic device and an input element connected between the grid and the junction of said series connected resistance and capacity.

8. An electrical amplifier circuit comprising, in combination, a vacuum tube amplifying device, an output circuit for the amplifier stage, an input circuit for said stage, and impedance elements forming an alternating current /Vheatstone bridge of which said output and input circuits form conjugate arms, two balancing arms of said bridge respectively comprising capacity between anode and control electrode of said tube and a resistance between cathode and control electrode of said tube, and the two remaining balancing arms being constituted by a resistance and a. capacity connected in series between cathode and anode of said tube.

9. An audion amplifier stage wherein an audion and a plurality of impedances form an alternating current lVheatstone bridge network having as conjugate arms thereof the input circuit and the output circuit of said stage, characterized by the fact that the two bridge arms terminating at the plate terminal of the audion are capacitive, and the impedances of the two bridge arms terminating at the filament terminal of the audion are resistive.

In witness whereof, I hereunto subscribe my name this 8th day of April, 1929.

AXEL G. JENSEN.

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