US2288275A - Modulating system - Google Patents

Modulating system Download PDF

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Publication number
US2288275A
US2288275A US211548A US21154838A US2288275A US 2288275 A US2288275 A US 2288275A US 211548 A US211548 A US 211548A US 21154838 A US21154838 A US 21154838A US 2288275 A US2288275 A US 2288275A
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United States
Prior art keywords
circuit
grid
tube
source
cathode
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US211548A
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English (en)
Inventor
Enoch B Ferrell
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AT&T Corp
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Bell Telephone Laboratories Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US729735A external-priority patent/US2159020A/en
Priority to GB15211/35A priority Critical patent/GB440993A/en
Priority to BE409720A priority patent/BE409720A/fr
Priority to DE1935ST053555 priority patent/DE698644C/de
Priority to NL73751A priority patent/NL40734C/nl
Priority to FR791875D priority patent/FR791875A/fr
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US211548A priority patent/US2288275A/en
Application granted granted Critical
Publication of US2288275A publication Critical patent/US2288275A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C1/00—Amplitude modulation
    • H03C1/02—Details
    • H03C1/06—Modifications of modulator to reduce distortion, e.g. by feedback, and clearly applicable to more than one type of modulator

Definitions

  • This invention relates to modulating systems directed particularly ,to those embodiments of and more particularly to means for regulating the invention that employ a self-detecting moduthe transmission characteristics of such systems. lator or amplifier to effect the detection required
  • the invention has as its main object to reduce for the reduction of distortion and-noise, thereby wave distortion in a modulator, particularly.eneliminating a separate detector for that purvelope distortion of a modulated wave. pose.
  • Fig. 1 shows a radio transmitting system re- Noise and modulation effects have been sucferred to in explaining the invention; cessfully controlled in amplifiers by means of Fig. 2 shows a radio transmittingsystem emnegative feedback or degeneration.
  • the underbodying the invention lying principles involved in this method of con- Fig. 3 shows an arrangement of the invention trol are disclosed by H; s.- Black in an article 1 as adapted to a screen grid amplifier; and
  • a balanced high frequency generat- detection is ing system is shown connected to a transmitemployed to derive a. detected signal from a ting antenna system 2 through ahigh frequency modulated carrier wave.
  • a signal source 4 is associated with back in the. system the detected signal varies the output circuit of the generating system by somewhat from the original signal in its wave means of a transformer 5, a bridge network 6 form according to the amount of noise and disand a low frequency amplifier I.
  • To reantenna 8 is provided with a rectifying detector prise this distortionthe detected signal is fed 9, the outputof the detector being connected back degeneratively upon the signal input of the through.
  • a filter I0 and transformer H to the modulator.
  • the fed-back component 85 By making the fed-back component 85 bridge 6. Tra formers 5 and I l are placed in large compared with the original signal input the opposite diagonals of the bridge, with the and controlling its amplitude, the envelope disamplifier 1 across one of the ratio arms. Detortion of the modulated wave may be reduced tector 9 may be a diode vacuum tube or a copperoxide rectifier or other rectifying device exhibit- Preferably a rectifier having a linear char- 40 ingalinear relationship between its input voltage acteristic is used as the means for detecting and output current.
  • the modulated ciple of degenerative feedback is used to remove 1 high frequency wave is amplified in the amplifier noise components and other undesired modu- '3 and radiated from the antenna-2.
  • the antenlations from a carrier wave thus providing a na 8 picks up energyfrom the radiated wave pure sinusoidal wave of constant amplitude for detector 9, which feeds the detected wave which may be supplied to a modulating amplifier back in reversed phase upon the input circuit of for signal modulation.
  • I the low frequency amplifier I.
  • the feedback is a division of my copendoperates to diminish noise effects and distortion ing application Serial No.
  • the bridge network 6 serves to isolate the feedback circuit from the signal supply circuit, makingthese circuits conjugate to each other and capable of independent adjustment.
  • Fig. 2 shows the application of the invention to a modulating amplifier of class B or class C; that the figure that an increase of plate current through coil 18 makes the grid more negative, while a decrease of plate current makes the grid less negative, these variations in the grid voltage being opposite in phase to the signal variations which cause the respective changes in plate current.
  • This'arrangement does not require a separate detector since the amplifier performs the detecting function.
  • the system operates to diminish noise and distortion arising in the modulating amplifier or in the carrier generator.
  • Fig. 3 shows an arrangement where the reversed feedback is from the plate circuit to the screen circuit of a screen grid tube.
  • the carrier source I! is connected to the antenna 2 through a screen grid tube 20.
  • the tube is provided with a large biasing battery 2
  • the signal source 4 is associated with the antenna 2.
  • a carrier generator i2 is connected to the antenna 2 through a modulating amplifier iii.
  • the signal source 4 is coupled to the input circuit of the amplifier it .by means of the bridge 6 and the transformer 5.
  • the grid circuit of the tube i3 includes one of the ratio arms of'the bridge.
  • the plate supply battery is shown at i9.
  • the carrier wave isimpressed upon the grid circuit of the tube I! along with the signal wave from the bridge 6.
  • the plate current from the bat tery l9 passes through the bridge 6 providing a strong negative grid bias for the tube. fixed by the potential dro -in'thei ratio arm included in the grid circuit. Due to the strong bias theplate current fiows in pulses when the carrier and signal waves are impressed; In the presence of the carrier without signals the pulses are uniform, but when the signals are applied the pulses vary in strength according to the signals. Consequently the plate current contains a component of low frequency, which is substantially a faithful copy of theenvelope of the modulated wave in a properly adjusted modulator.
  • Fig. 4 illustrates a reversed feedback system in which the wave fed back is a component of the plate current in a class B power amplifier.
  • the carrier source I2 is connected to the antenna 2 through a carrier supply amplifier 30, modulating amplifier l3 and power amplifier 11.
  • the carrier amplifier 30 is provided with a choke coil II which is common to the plate and grid circuits of the amplifier.
  • the signal source 4 is coupled to the grid of the tube It through the transformer 5 and the bridge 6.
  • the plate circuit of the tube It is coupled to the grid circuit of thetube l3 by means of a resistance-l2.
  • a modulating system comprising a vacuum tube having a cathode, a grid and a plate, a grid circuit and a plate circuit therefor, a carrier source coupled to the grid circuit, a; bridge network, a signal source included in one diagonal of the bridge, and an impedance selective to low frequency included both in the other diagonal of the bridge and in the plate circuit of the tube, the grid circuit of the tube including a ratio arm of the bridge.
  • the method of correcting distortion nor-v mally produced in a modulation circuit comprising an electron discharge tube having input electrodes connected with a source of carrier waves and with a source of modulating potentials and having output electrodes connected through a modulation frequency impedor to produce in said impedor correcting potentials of modulation potential frequency which includes the steps of, impressing correcting potentials from said impedor on said. input circuit in phase opposition with respect to the modulating potentials im-' pressed thereon from said modulation potential source, and adjusting the amplitude of said correcting potentials to reduce distortion in said tube.
  • A' modulating system with distortion correc-' tion comprising a carrier wave source, a signal wave source, a self-detecting modulator of a type adapted to generate a pulsating output current analyzable into a modulated carrier wave component and a wave component simulating the cathode circuit and at least one grid-cathode circuit therefor, means for setting u carrier claim 5 inwhich the modulation frequency imwaves in the anode-cathode circuit of said modulator under the control of said carrier wave source, means for impressing waves from said signal wave source upon a grid-cathode circuit of said modulator to generate said pulsating output current in said tube, decoupling means between said signal wave source and said anodecathode circuit, means connected to said modulator for selecting and utilizing said modulated carrier wave component of the output current.
  • a modulatin system comprising a discharge tube having a cathode, an anode and a grid. an anode-cathode circuit and a grid-cathode circuit therefor, a carrier source, means to set up carrier waves in the anode-cathode circuit under the control of said carrier source.
  • a source of modulating potentials coupled to the gridcathode circuit decoupling means between said source of modulating potentials and said anode cathode circuit, an impedance device having one terminal connected to the cathode and the other terminal connected both to the grid and to the anode and means for producing'in said impedtil tube having a cathode, an anode and a grid, an anode-cathode circuit and a grid-cathode circuit therefor, a carrier source, means to set up carrier waves in the anode-cathode circuit under the control'of said carrier source, a source of modulating potentials coupled to the grid-cathode 5 by there are produced in said modulation irequency impeder distortion correcting potentials 'of modulation potential frequency simulating the original modulating potentials with superposed distortion from the modulating process and whereby the said distortion correcting potentials ⁇ are inherently in phase opposition with respect to the modulating potentials impressed upon the grid-cathode circuit from said
  • a modulating system in accordance with peder comprises an inductance.
  • the modulation frequency impeder comprises a resistor shunted by a condenser.
  • 'A modulating system comprising a discharge tube having a cathode, an anode and a grid, anode-cathode and grid-cathode circuits there for, a carrier source, means to set up. carrier waves in the anode-cathode circuit under the control of said carrier source, a signal sourcecounpled to the grid-cathode circuit and an inductance having substantial reactance in the frequencyrange comprising the waves from said signal source and having one terminal connected to the cathode and the other terminal connected to the grid and to the. anode to selectively transfer between saidanode-cathode and grid-cathode circuits, waves in the said'frequency range.
  • a modulating system comprising a discharge tube having a cathode, an anode and a grid,
  • anode-cathode and grid-cathode circuits there-v for, a carrier source, means to set up carrier waves in the anode-cathode circuit under the control of said carrier source, a source of modulating potentials coupled to the grid-cathode circuit, decoupling means between said source of modulating potentials and said anode-cathode circuit, an impedance device having one terminal connected to the cathode and the other terminal c nnected both to the grid and to the anode, and
  • a modulating system withdistortion correction comprising a discharge tube having a cathode, an anode and a grid, anode-cathode and grid-cathode circuits therefor, a carrier source, means to set up carrier waves in the anode-oath ode circuit of said tube under the control of said carrier source, a source of modulating potentials coupled with the grid-cathode circuit, decoupling means between said source of modulating potentials and said anode-cathode circuit, a modulation frequency impeder having one terminal connected to the cathode and the other terminal connected both to the grid and to the anode and means to substantially suppress the space current of the tube in the absence of impressed alternating current excitations, whereby there are developed in the anode-cathode circuit including said modulation frequency impeder distortion corrective currents of modul
  • a modulating system comprising at least one high frequency amplifier-detector tube, grid and-plate circuits therefoig'a carrier source, a
  • agsignal source means to combine carrier waves and signal waves from said respective sources to produce a modu-' lated carrier wave in the plate circuit of said amplifying tube, means to impress upon a grid of said amplifying tube suflicient negative biasing potential to substantially cut oil the space current of the tube in the absence of impressed alternating current excitation, whereby signal waves cause self-detected signal frequency variations in the space current of said amplifying .tube and means to feed said signal frequency space current variations into a grid circuit of the circuit, including input electrodes, said electrodes being connected with a source of carrier waves and with a source of modulating potentials and having output electrodes connected through a modulation frequency impeder toproduce in said impeder correctingpotentials of modulating potential frequency, which includes the steps of impressing modulating potentials upon said input circuit from said modulation potential source and impressing correcting potentials from said impeder on said input circuit in phase opposition with respect to the modulating potentials impressed thereon
  • a modulation system comprising a source of carrier waves, a source of modulating potentials, a modulation frequency impeder, an electron discharge tube having input electrodes connected with said source of carrier waves and with system previously traversed by signal waves and in such phase as to effect substantial phase opposition between said signal waves and said signal frequency space current variations in said grid circuit.
  • a modulating system comprising a self-detecting amplifying" tube, grid and, plate circuits therefor, a carrier source, a utilization circuit for waves of carrier frequency in the plate circuit of said tube, a signal source, means to combine carsaid source of modulating potentials, and having,
  • output electrodes connected through said modulation frequency impeder, means to substantially suppress the space current of said tube in the absence of impressed alternating current excitations, whereby there are produced in said modulation frequency impeder correcting potentials of modulation potential frequency, and means for impressing correcting potentials from said impeder on said input electrodes in phase opposition with respect to the modulating potentials impressed thereon from said modulating potential source.
  • a source of carrier wave oscillations a source of modulating potentials, an electron discharge tube having a control grid, a cathode and an anode, a circuit cou pling said source of carrier wave'oscillations to said cathode and control grid, a circuit coupling rier waves and signal waves from said respective sources to produce a modulated carrier wave in' the plate circuit of said amplifying tube together with self-detected signal frequency variations in the space current of said tube, and means to feed said signal frequency space current variations into a grid circuit of the system previously prising a plurality of space discharge tubes connected in cascade, grid and plate circuits for said tubes, a utilization circuit for waves of carrier frequency in the plate circuit of one of said tubes, a carrier source, a signal source, means to modulate carrier waves and signal waves from said respective sources and thereby to produce a modulated carrier wave in the aforesaid plate circuit, means including a self-detecting amplifying tube whereby the application of signal waves
  • a modulating system with distortion cor type adapted to generate a pulsating output current analyzable into amodulated carrier wave component and a wave component simulating the signal wave with superposed distortion from the modulating process
  • said modulator comprising an electron discharge tube with a cathode, an anode, a control grid and a screen grid, an anode-cathode circuit and a screen grid-cathode circuit therefor, means for setting up carrier waves in the anode-cathode circuit of said modulator under the control of said carrier wave rection, comprising a carrier wave source, a signal wave source, a self-detecting modulator of a source, means for impressing waves from said signal wave source upon said screen grid-cathode lating amplifier tube, a, combined power amplifier and detector tube, a low frequency amplifier tube, grid and plate circuits for each of said tubes, means for setting up carrier waves in the plate circuit of said modulating amplifier tube, a bridge network including an arm coupled to the grid circuit of said low frequency

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US211548A 1934-06-09 1938-06-03 Modulating system Expired - Lifetime US2288275A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
GB15211/35A GB440993A (en) 1934-06-09 1935-05-24 Modulating systems for carrier wave signalling systems
BE409720A BE409720A (fr) 1934-06-09 1935-05-29 Perfectionnements aux systèmes de signalisation à haute fréquence
DE1935ST053555 DE698644C (de) 1934-06-09 1935-05-30 Modulationseinrichtung
NL73751A NL40734C (enrdf_load_stackoverflow) 1934-06-09 1935-05-31
FR791875D FR791875A (fr) 1934-06-09 1935-06-06 Perfectionnements aux systèmes de signalisation à haute fréquence
US211548A US2288275A (en) 1934-06-09 1938-06-03 Modulating system

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US729735A US2159020A (en) 1934-06-09 1934-06-09 Modulating system
US211548A US2288275A (en) 1934-06-09 1938-06-03 Modulating system

Publications (1)

Publication Number Publication Date
US2288275A true US2288275A (en) 1942-06-30

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Application Number Title Priority Date Filing Date
US211548A Expired - Lifetime US2288275A (en) 1934-06-09 1938-06-03 Modulating system

Country Status (6)

Country Link
US (1) US2288275A (enrdf_load_stackoverflow)
BE (1) BE409720A (enrdf_load_stackoverflow)
DE (1) DE698644C (enrdf_load_stackoverflow)
FR (1) FR791875A (enrdf_load_stackoverflow)
GB (1) GB440993A (enrdf_load_stackoverflow)
NL (1) NL40734C (enrdf_load_stackoverflow)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2460498A (en) * 1943-03-15 1949-02-01 Sperry Corp Modulation control apparatus
US2858511A (en) * 1954-07-12 1958-10-28 Westinghouse Electric Corp Method of obtaining audio feedback from a modulated r. f. amplifier

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2460498A (en) * 1943-03-15 1949-02-01 Sperry Corp Modulation control apparatus
US2858511A (en) * 1954-07-12 1958-10-28 Westinghouse Electric Corp Method of obtaining audio feedback from a modulated r. f. amplifier

Also Published As

Publication number Publication date
NL40734C (enrdf_load_stackoverflow) 1937-05-15
FR791875A (fr) 1935-12-18
DE698644C (de) 1940-11-14
BE409720A (fr) 1935-06-29
GB440993A (en) 1936-01-09

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