US1710015A - Modulation system - Google Patents

Description

April 23, 1929. c. A. cu LvER I MODULATION SYSTEM Filed July 16. 1926: I

' INVENTOR. f/zay' [05A a Z002;

ATTORNEY control the high frequency output of a radio any given instant the potentials of the grids "20 vide a circuit arrangement at a transmitter thus existing in the inductances L and L Patented Apr. 23, 1929. v

UNITED STATES PATENT OFFICE.

CHARLES A. CULVER, OF NQRTHFIELD, MINNESOTA, ASSIGNOR TO WIRED RADIO, INCL;

OF NEW YORK, N. Y., A CORPORATION OF DELAWARE.

MODULATION SYSTEM.

. Application filed July is, 1926. Serial N0.,122,986.

My invention relates broadly to circuits for to the antenna ground system 12 as shown controlling the output of a high frequency through the coupling inductance L electrical generator, and more particularly High frequency energy from the master osto a system of modulation foruse in con'ueccillator or driving circuit VT is tral'isferred 5 tion with radio telephone transmission or to the amplifier-modulator circuit through 5. broadcasting. the inductive relation obtaining between the One of the objects of my invcntion'is to inductances L L and L The grids of the effect an improvement in the means whereby 'triodes VT and VT are thus subjected to a voice generated potentials may be made to high frequency alternating potential. At

t ans-nutter, and in particular to provide a of these tubes will differ in, phase by 180. system whereby the necessity for se mrate The resulting alternating current components modulating and amplifying tubes is climiinthe two plate circuits will, therefore, be nated. I y 2 additive. However, the phase relation of 15 Another object of my invention is'the supthe potentials on the grids due to certain har- 65 pression'of hari'nonic frequencies in the high monies in the input will be of such a nature frequency power circuit of a "radio transthat the resulting plate currents will nullify mitter. f one another, and thus be suppressed. The A further object of'my invention isto proen ergy of the purified high frequencycurrent to secure greater over-all power efliciency in transferred to the antenna ground system transmission. 1. i i through the inductive relation obtaining be- Still anotherobject of my invention is to tween L L and L In order to secure provide a system of modulation for a t-ran higher power etficiency, the output circuit of mitter wherebyfdistortion is reduced to a ,the amplifier-modulator tubes are adjusted f minimum. I, i to resonance with the frequency delivered by f The invention will be more fully underthe driving circuit. This is accomplished by stood by reference to the following specificameans of the capacitances C and C The tion and accompanying drawing which'shows input circuit of these tubes may also be ad- 30- diagrammatieally a wiring arrangement of justed to resonance with the driving circuit, 60 a radio transmitter embodying the principles though this is usually unnecessary and, in of my invention. fact, in most cases undesirable. The ampli- Referring to the drawing in detail the os tier-modulator organization is less apt to oscillator tube VT together with the associllate in and of itself if the grid circuits are ciated inductance L capacitances C and C untuned. and the plate potential supply 135, constitute Modulation is. effected by means of the a master oscillator or driving circuit. voice generated potentials developed in the Various forms of oscillator circuits maybe secondary of thetransformer T, said potenemployed. 1 I tials being impressed 0n the grids of the tubes 10 Thecomponent parts consisting of the in- VT and VT simultaneously with the high ductances L L L, and L the capacitances frequency potentials induced by the master (I. 0 .0 and C the triode tubes VT, and oscillator. The. audio potentials developed the plate potential supply. B together at the terminals of the secondary of the transwith the usual filament supply, constitute a former T will be opposite in sigmthat is. out 45 combinedbalanced amplifying and modul'atof phaseby 1809, and hence the grid of the ing system. tubes VT and VT will be subjected to on The transformer T, the microphoneM,(and posite audio potentials. As a result of this battery B3 constitute the means whereby condition, the operating point on one of said sound waves are causedto control or modutubes will be moving upward on its character- 59 late theenergy delivered by the; organization istie. curve, whilethe operating point on. the

ther tube will be moving downward. lhis condition will result in an increase of output in one tube and a simultaneous decrease of output in the other tube of the balanced pair, thus establishing a so-called puslrpull condition in theoutputcircuit of the tubes VT, and VT,. These audio potentials cause the operating point of the grids of the tubes to move up and down on their characteristic curves, and thus'the high frequency output "or said tubes will be caused to vary in conformity with the voice generated potentials. As a result, the amplidude of the high frequency current developed in the antenna. circuit will vary inaccordance with the audio frequency potentials impressed upon the grids of the modulator-amplifier tubes, It will thus be seen that modulation iseftected without the use of separate modulating tubes, thus reducing the operating cost andalso securing a. greater over-all power eiiiciency. Investigation has shown also'thatthe over-all power efi'iciency is furtlier'increased as a result of i the balanced arrangement of, themodulatoramplifier tubes as shown.

' Because of the balanced arrangement of the tubes VT and VT.,, the voltage variations to which the grids of these tubes are subj ected may readily be held within limits such that the operating point on the characteristic curve will not pass beyond the straight portionof said curve,fthus avoiding distortion which might otherwise result.

' It is to be understood that modifications Other and further modifications of may be made in the above described circuits without departing from the fundamental principles involved. For instance, a series of tubes in parallel be substituted for. each of the single tubes "VT, and Vige shown, thus increasing the power output.

, ne circuit may be made within the scope of the appended claimswithout depaitin from the a spirit of the invention.

J1. A signal transmission system coinprising a plurality of electron tubes each having grid, filament and plate electrodes, input and output circuits interconnecting said electrodes with the input and output circuits of one of said :electron tubes mutually coupled for the generation of high frequency oscillations, a

signal transmission circuit, and a pair'of balanced circuits interconnecting,otlicrsof said electron tubes and interposed between SZUCl signal transmission circuit and said high frequency oscillating circuit, and a microphone circu tincluding a transformer sysstem havingjprimaryand secondary windin with thesecondary winding connected at opposite'ends with grid electrodes of said electron tubes connected in said balanced CllCllltS for modulating the eilc'ctsfof said high he quency oscillating circuit upon said signal transmission circuit.

2. A signal transmission system comprising a plurality ofelectron tubes each having grid,

filament and plate electrodes, input and output circuits interconnecting said electrodes with the input and output circuits of one of said electron tubes mutually coupled for the generation of high frequency oscillations, a signal transmission circuit, a pair of said electron tubes being connected in balanced relationship with the output circuits of said trodes of said pair of electron tubes, and connections between said high frequency oscillating circuit and the input circuits of said pair of electron tubes for impressing high frequency current thereon whereby the efli'ccts of said currenton said transmission circuit may be varied in accordance with the operation of saidmicrophone circuit.

3. A signal transmission system comprising a plurality of electron tubes each having grid,'fila-mentand plate electrodes, input and output circuits interconnecting said electrodes, one of said electron tubeshaving iiiductances connected in its input and output circuitsfor sustaining high frequency oscillations, a pair of said electron tubes being, connected in balanced relationship, a signal transmission circuit, connections between the output circuits of said pair of electron tubes and said signal transmission circuit, inductances in eachof the input circuitsof said pair of electron tubes, both of said inductances beingcoupled with the inductances in" the output circuit of said first mentioned tube, a microphone circuit including primary iandsecondary windings with the secondary winding connected between the inductances in the input circu ts of said pair of electron tubes'whereby the effects of said high frequency oscillation circuit upon said transmis-r S1011 circuit may be variablycontrolled.

LA modulation system comprising in combination a plurality of electron tubes-each having grid, filament and plate electrodes, input and output circuit-s intercoiinectingsaid electrodes, connections between the input circuits of a pair of said electron tubes, connections between the output circuits of said pair ofe'lectron tubes, :1 signal transmission circuit, a connection between said last men tion'ed outputcircuits and said signal transmissioncircuit, another of said electron tubes having input and output circuits mutually 'coupledforthe generation of oscillations and jfid8p6l1ClO1ltly coupled with the input circuits with the input circuit of one of said pair of electron tubes, and at the opposite end with 10 the input circuit of the other of the electron tubes of said pair for modulating the effect of said voice control circuit on said pair of electron tubes. y c

In testimony whereof I affix my signature.

CHARLES A. CULVER.

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