US1485650A - Generating harmonic currents - Google Patents

Description

March 4 1924. 1,485,650

H. J. vENNEs GENERAT ING HARMONI C CURRENTS /M vena/c' #wref/a JT Ven/ves y is of general application in the electrical.

- vshowing operating characteristics of a thermionic device accord' `of this invention, the impressed wave is 'which may be resolved into a fundamental ma be amplified.

4circuit arrangement for the production of tron source,

Patented Mar. 4, 1924. l UNITED STATES PATENT OFFICE.

HARALD J. vENNEs, or NEw YORK, N. Y., ASSIGNon 'ro WESTERN ELECTRIC courANY,'1NcoRroR.a'rEn, or NEW voRx, N. Y., A CORPORATION or NEW YoRx.

GENERATING HARMONIC CURBENTS.

V.Application lcd April 28, 1919. Serial No. 293,055.

To all whom t may conce/rn.' normal characteristic curve of a thermionic Be it known that I, HARALD J. VENNES, relay, it is seen that along only a relatively a citizen of the United States, residing at short portion of the curve in the region New York, in the county of New York Land representing zero potential on the grid will State of New York, have invented certain a given change of grid potential in the nega.- new and useful Improvements in Generatl tive .and in the positive direction produce ing Harmonic Currents, of which the fol- Substantially equal variations in plate curlowing is a full, clear, concise, and exact rent above and below a mean value. When description. the grid potential is varied over a com- This invention relates to the generation paratively Wide range, the plate current of electric currents and has for an object Variations d0 IlOt COIieSpOnd precisely, and the production of harmonic currents from a advantage-'may taken of this fact to sesource of alternating voltage, cure a non-sinusoidal plate current by im- A feature of the invention relatos to a pressing a sinusoidal electromotive force of circuit arrangement whereby harmonics are Sllloieilt magllltude- This action has been generated effectively by the use-of an elcc- Called overloading the tube, and the distron discharge rela torting effect depends upon the limited sup- This invention re lares to a means of andv ply'iof electrons present in the electron tube, method for producing harmonics from an available for conveying current across the impressed electromotive force of preferably substantiallysinusoidal wave form. The ap- According to the present invention a Chaiaratus is termed a harmonic producer and actllstlc ShQWn a? Curve 2 1S Secured: m which the distortion is very pronounced, arts. o, It is herein considered in connection and which is Particularly adapted t0 the with a transmission system as a generator or P1`0d110t1011 0f h91`m01110 0n 210001111@ 0f ,h regenerator, according as it is adapted to abrupt break 111 the P01431@n 0f the Cllrveln' produce harmonic currents for transmisfllcated by Tb@ l'aSO'll for *311,13 bend Sion Purposes, .or to Supply corresponding in the curve is primarily,I that the internal harmonics for reception or retransmission resistance is of such a small value relative purposes. According to thev preferred forni Y later pre ominates in controlling the ampligiven a marked distortion in one half-cycle, tude 0f the .Plate Qmzrent- In .Fi ,2 are hown the characteristic curve 3 an a curve while it is repeatedl more nearl true to S form in the op osite half-cycle y taking 5 glvmg the form 0f Wave Produced m the advant e of tlie irregular characteristic of an e ectron discharge de vice when provided with a suitable high v'resistance in its output circuit. The output current of the electron discharge device willtherefore have a distorted or non-sinusoidal wave form,

sine wave form indica by the dotted curve tially sinusoidal, while the upper portion is much distorted. By analysis, it is found both even and odd harmonics, in about. the same proportion.-

. Referring to Fig. 3, current from a sine wave generator 6 of base frequency is supplied through line 7 to the primary 8 of a ference. is made to the drawings, in step-upY transformer, 'the secondary 9 of 1 and 2 of which are 'ven curves whichfis connected to the input terminals of f uency component and a series of sinusoi al harmomcs. By suitable circuit arran ments, these harmonic currents may be amp ied to a work circuit, and, if desired,

Figs

10 comprises an evacuated container orl tube hot', filament 11, or 'other elecl a plate orv anode 12 and a 'd the present. -in-4 lor impedance controllingx lement 13. A atter 14 maybe used to the norfmalpotenf to the invention, and Fig. 3 illustrates iagrammatically a' containing a harmonics according to veiition. f

From the curve 1 which represents the discharge space.

tothe lar e external fixedresistance that thel output circuit by an im ressed potential of...

a 'therinonic' amplifier 10. The vamplifier 4. It is seen that the portion of curve be low the normal amplltude line 1s substanthat the output wave thus obtained contains ti of the 13. vThe lament 11 may be 11 heated by current from a battery 15 regulated by the variable resistance 16. AThe amplifier' is provided with plate current from a battery 17, connected to the filament 11, and to the plate 12 through an impedance 18, which acts to exclude the variation current component from this path. The output circuit .of amplifier 10 is traced through a condenser 19 of large capacity to the grid 21 of the harmonic generator or regenerator 20, which has a hot cathode or filament 22 connected to the filament 11 and supplied with heating current from the battery 15. A switch 20 is shown whereby the normal potential of the grid relative to the filament may be made zero as in the position shown, or may be 4made positive or negative by throwing the switch to one or the other of the other positions indicated. Connected across the filament 22 and grid 21 is a parallel resonant circuit 26 consisting of an inductance and a capacity tuned to the base frequency, so that this path offers practically infinite impedance to the base frequency current, but low impedance to any harmonics which may have passed the amplier 10. The result is that a substantially pure sinusoidal wave is impressed upon the harmonic gene ator or regenerator 20. Condenser 19 acts as a blocking condenser to prevent fiow of current from battery 17 through path 26 and back through the impedance coil 1S.

The harmonic producer 20 comprises an evacuated tube containing, in addition to the grid 21 and filament 22 already mentioned, an anode or plate 23. Plate current is supplied from battery 17, connected to the filament 22, and to plate 28 through an impedance coil 24, similar to impedance coil 18, anda large ohmic resistance 25, which may be inductive or non-inductive. Coil 24 may be omitted, especially if the resistance 25 is inductive. This resistance 25 is large compared with the normal output impedance of the tube, values of the order of from 6000 ohms to 48000 ohms having been used, depending upon operatin 5 conditions, where the normal internal output impedance of the tube was of the order of 4000 or 5000 ohms. The smaller value of resistance mentioned was used in a particular case in which the base frequency current supplied to the harmonic generator was relatively strong, and the large value Was used when the incoming base frequency current was weak and it was found advantageous to bring the break in the characteristic of the generator well within the range of the small impressed potential. These values are given by Way of illustration only and are not to be construed as in any sense limiting the invention. Resistance 25, in addition to giving the highly advantageous characteristic for the production of harmonics, performs the additional function of greatly stabilizing the output circuit, since when the tube is highly conducting, i. e., when the distortion occurs and therefore when the harmonics are being produced, the impedance of tli'e circuit is practically the impedance of the exterior portion of the circuit, and small fluctuations in the tube impedance, such as are often occasioned by an exchange of tubes, have negligible effect upon the production of harmonics.

Y The output circuit of the harmonic generator 20 leads through the condenser 27 of large capacity to the grid 28 of a thermionic amplifier 80. which has a hot cathode or filament 20 connected to filament. 22 and supplied with heating current from the battery 15. A battery 31 is used to fix the normal potential of the grid 28. Condenser 2T acts as a blocking condenser to prevent fiow of current from battery 17 through the path 24, 25, and back through the inductance 34, mentioned hereinafter. In the evacuated enclosure of amplifier 30, besides the grid 28 and filament 29 already mentioned, is a plate 32 connected to the plate battery 17, through in'ipedance coil 33, which acts similarly to impedances 18 and 21, to prevent fiow of variation current components in the plate battery circuit. Across the input terminals of the amplifier 30, an inductance 34 is connected, which offers low impedance to the base frequency current component, but high impedance to the harmonics which appear in the output circuit of the harmonic generator 20. The harmonics are therefore impressed on the amplifier 30, and after passing through the amplifier, they are led through a condenser 235 of large capacity to the primary 530 of a suitable transformer,the secondary 3T of which may be connected to the desired work circuit. J

Although an exact explanation of the action of the resistance 25 is notessential to enable one to practice this invention, thel following explanation is believed to be correct andimay assist somewhat in an understanding of the invention. It is not intended as a limitation on the invention, Which is independent. of the theory of operation.

The space current circuit comprises in series the space current source, the large fixed external resistance and the variable internal resistance of the tube. This latter resistance approaches a zero value as the grid potential increases. As the internal resistance approaches zero the space current; approaches the limiting value determined by the fixed external resistance. Accordingly. the bend in the characteristic curve must occur between this limit -when the effect of the external resistance preponderates and the other limit When the internal resistance is large enough to cause its effect to preponderate. That this bend due to the effect of the large external resistance becomes comparatively sharp as the horizontal portion of the curve is approached follows from the fact that with a uniform rate of decrease of the internal resistance, the rate of change lof the ratio of external to internal resistance progressively increases.

It should be noted also that the eiect produced by the external resistance and the ordinary so-called saturation eiect are additive, which increases the sharpness `of the bend in the characteristic curve.

Although the invention has been illustrated and described in connection with a pecific circuit arrangement, it is to be unerstood that it is not' to be limited either to the specilic arrangement as a whole or to its particular details, but only by the scope of the appended claims.

What is claimed is:

1. The method of generating harmonics in a system comprising in combination a source of alternating electromotive force, an

'electric discharge repeating device having a cathode, an anode and an impedance control element, and a high resistance in the output circuit of the repeatingdevice, which method consists in impressing on the repeating device from said source cyclically varying voltage which alternates between limits chosen to include the knee of the characteristic curve of said repeating de-v.

chosen to include the knee of the charactery istic curve of said repeater.

3. A generator of harmonics comprising an electric discharge repeating device having a cathode, an anode and an impedance control element, a source of substantially constant alternatin potential connected to said cathode and said impedance control element, and a direct current source and a large impedance serially connected to said cathode and anode, the amplitude of said alternating potential being sufficient to cy- 5. A generator of harmonics comprising an electron discharge repeater comprising an electron discharge device with an anode, a cathode and an impedance control element, an input and an output circuit for said repeater, a source of substantially constant alternating potential and a polarizing source connected to said input circuit, a

of element ar e compared to the minimum internal impeance of said device connected serially in said output circuit whereby angular configuration is given to the characteristic curve representing the relation between the potential of the impedance control element with respect to the cathode and the space current, the potentials impressed from said alternating potential and polarizing sources being such that operation occurs over that part of said characteristic curvel which includes the angular portion.

In witness whereof, I hereunto subscribe my name this 24th day of April A. D. 1919.

HARALD I. VENNES.

-source of s ace current and an impedance

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