US2530937A - Frequency modulator - Google Patents

Frequency modulator Download PDF

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Publication number
US2530937A
US2530937A US679103A US67910346A US2530937A US 2530937 A US2530937 A US 2530937A US 679103 A US679103 A US 679103A US 67910346 A US67910346 A US 67910346A US 2530937 A US2530937 A US 2530937A
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US
United States
Prior art keywords
tubes
frequency
capacitors
circuit
reactance
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
US679103A
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English (en)
Inventor
John R Boykin
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.)
CBS Corp
Original Assignee
Westinghouse Electric Corp
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 to BE474098D priority Critical patent/BE474098A/xx
Application filed by Westinghouse Electric Corp filed Critical Westinghouse Electric Corp
Priority to US679103A priority patent/US2530937A/en
Priority to GB13661/47A priority patent/GB628901A/en
Priority to FR948331D priority patent/FR948331A/fr
Application granted granted Critical
Publication of US2530937A publication Critical patent/US2530937A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C3/00—Angle modulation
    • H03C3/10—Angle modulation by means of variable impedance
    • H03C3/24—Angle modulation by means of variable impedance by means of a variable resistive element, e.g. tube

Definitions

  • My invention relates to transmission systems for generating frequency modulated waves and. in particular, relates to a circuit employing a novel method of modulating frequencies by varying the equivalent reactance of a resonant circuit.
  • My arrangement is, in fact, generally applicable to the problem of varying the tuning of resonant circuits for any purpose.
  • one of the best known arrangements of the prior art has effected frequency-modulation of an oscillation generator by means of reactance tubes; that is to say, tubes which carried current substantially 90 degrees out of phase with the voltage across their terminals and in which the amplitude of such dephased current is varied in response to fluctuations of a signal Voltage impressed on control grids in the reactance tubes.
  • reactance tubes that is to say, tubes which carried current substantially 90 degrees out of phase with the voltage across their terminals and in which the amplitude of such dephased current is varied in response to fluctuations of a signal Voltage impressed on control grids in the reactance tubes.
  • this reactance tube method of frequency-modulating the oscillations generated hasdisplayed a practical defect of no small moment in that the control electrodes of the reactance tubes have been found to be subject to mechanical vibrations or microphonics.
  • My invention overcomes this defect by employing in the resonant circuit, which determines the frequency generated by an oscillation generator, only diodes; i. e., tubes which contain no control electrodes. Such tubes are much less subject to difficulty from microphonic and mechanical vibrations than are triodes and other tubes containing control elec-,
  • One object of my invention is, accordingly, to produce a system for frequency-modulating an oscillation generator which shall be substantially free from the effects of microphonics and mechanical vibrations.
  • Another object of my invention is to produce an arrangement for varying the resonant frequency of a tuned circuit by employing equipment which is not susceptible to the effects of shock, jar or microphonics.
  • Still another object of my invention is to provide a system for varying the reactance of an electric circuit by employing elements not subject to microphonic disturbances and the like.
  • Still another object of my invention is to provide an arrangement for varying the reactance of an electric circuit by employing tubes of the diode type.
  • the basis for my invention is the fact that where a capacitor is connected to an alternating voltage source in series with a variable resistor, the reactive component of the current flowing is found to vary with the changing value of the resistor; and such reactive component is found to vary most rapidly with changes of resistance when the resistance and the reactance are equal to each other.
  • tubes i and 2 are grid-controlled oscillator tubes of any conventional type, being shown for purposes of illustration as pentodes.
  • the respective anodes of the tubes I and 2 are connected to the outside terminals of a pair of seriallyconnected inductors 3 and 4 having their common terminal connected through a capacitor 5 to ground.
  • Any suitable output circuit 6, in which it is desired to employ frequency-modulated oscillations, may be connected to the anodes of the tubes I and 2.
  • Thetubes I and 2 have their suppressor grids connected to their cathodes and have their screen grids respectively connected to ground through capacitors I and 8.
  • the cathodes of tubes I and 2 are interconnected with each other through a pair of inductors 9, It], the common terminal of which is connected to ground.
  • the control electrodes of the tubes I and 2 are connected to each other through four serially-connected capacitors I2, I3, I4, I5.
  • the common terminal of the middle pair of capacitors I3 and It is connected to ground, and the two other common terminals of the abovementioned four capacitors are connected to the cathodes of tubes I and 2.
  • the control electrodes of the tubes I and 2 are likewise connected to ground through a pair of variable capacitors I'I, I8, and are likewise connected to each other through an inductor is havin its mid-terminal connected to ground through a resistor 20.
  • the circuit so far outlined will be recognized by those skilled in the art as a wellknown type of oscillation generator system, the resonant frequency of the output current of which is fixed by the tuned tank circuit l'i, l8, IS.
  • the control electrodes of the tubes I and 2 are likewise connected to each other through a channel comprising a capacitor 2!, a diode 2.2, a second diode 23 and a capacitor 24, said diodes being oppositely poled.
  • the diodes 22 are, in effect, resistors connected in series with the capacitors 2
  • the diodes 22 and 23 constitute the variable resistance which modify the amount of reactive current drawn from the above-mentioned tuned circuit by the capacitors 2
  • I To controllably vary the resistance of the diodes 22 and 23, I connect the positive terminal 25 of a direct-current source having its negative terminal grounded to the respective anodes of the tubes 22 and 23 through resistors 26, 21. I connect the cathodes of the tubes 22 and 23 to the anode of an electron tube 28 having a cathode connected to ground through a capacitor 29. I connect the control electrode of the tube- 28 to ground through a resistor 3
  • , 35 and diode 22 is connected directly in shunt with capacitor l! to ground; and a similar statement applies to the homologous capacitors and diode 23 on the other side of the frequency determining circuit.
  • the value of the resistance 26 is such that the reactance of the parallel networks 26, 22, 35, 34 is equal to the resistance 2
  • the parallel networks 21, 23, 34, 35 has a resistance equal to the reactance of capacitor 24 at the unmodulated frequency of the oscillators.
  • variable resistor i. e., a diode which is employed in series with the reactance element may be replaced satisfactorily for many purposes by other known types of variable resistor; e. g., by a carbon-type microphone.
  • I have, in diodes 22 and 23, shown a particular type of rectifier, any other type of rectifier having a resistance varying with. the direct-current voltage impressed upon it, as a selenium or a copper oxide rectifier, may be substituted for such diodes.
  • a generator of electrical oscillations including a frequency determining network, a component having a non-linear, current-voltage characteristic, and an electric discharge device having a control electrode and a plurality of principal electrodes, said component and said principal electrodes being connected in. series with each other to said frequency determining network, and terminals for impressing a control potential between said control electrode and one of said principal electrodes.
  • the component having a non-linear, current-voltage characteristic is a diode having its anode connected to the frequency determining network and its cathode to one of the principal I electrodes of the discharge device.
US679103A 1946-06-25 1946-06-25 Frequency modulator Expired - Lifetime US2530937A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
BE474098D BE474098A (xx) 1946-06-25
US679103A US2530937A (en) 1946-06-25 1946-06-25 Frequency modulator
GB13661/47A GB628901A (en) 1946-06-25 1947-05-21 Improvements in or relating to frequency determining circuits for high frequency oscillators
FR948331D FR948331A (fr) 1946-06-25 1947-06-24 Modulateur de fréquence

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US679103A US2530937A (en) 1946-06-25 1946-06-25 Frequency modulator

Publications (1)

Publication Number Publication Date
US2530937A true US2530937A (en) 1950-11-21

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ID=24725563

Family Applications (1)

Application Number Title Priority Date Filing Date
US679103A Expired - Lifetime US2530937A (en) 1946-06-25 1946-06-25 Frequency modulator

Country Status (4)

Country Link
US (1) US2530937A (xx)
BE (1) BE474098A (xx)
FR (1) FR948331A (xx)
GB (1) GB628901A (xx)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2749310A (en) * 1954-09-03 1956-06-05 Shell Dev Lubricating compositions
US3020493A (en) * 1959-02-27 1962-02-06 Hughes Aircraft Co Frequency modulation circuit

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE977690C (de) * 1950-03-07 1968-05-22 Siemens Ag Elektrischer Zweipol, der in seinem Blindwiderstandswert durch eine Steuergroesse veraenderbar ist
DE977095C (de) * 1950-03-07 1965-01-28 Siemens Ag Elektrischer Zweipol in einer Schaltung fuer Frequenzmodulation, Frequenznachstellung oder den Abgleich von Messbrueckenanordnungen

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2296962A (en) * 1939-12-22 1942-09-29 Rca Corp Frequency modulation
US2354799A (en) * 1940-07-26 1944-08-01 Rca Corp Phase modulation
US2374000A (en) * 1943-03-06 1945-04-17 Rca Corp Phase modulator
US2430126A (en) * 1943-08-25 1947-11-04 Rca Corp Phase modulation
US2436834A (en) * 1942-11-17 1948-03-02 Edwin K Stodola Phase and frequency modulation

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2296962A (en) * 1939-12-22 1942-09-29 Rca Corp Frequency modulation
US2354799A (en) * 1940-07-26 1944-08-01 Rca Corp Phase modulation
US2436834A (en) * 1942-11-17 1948-03-02 Edwin K Stodola Phase and frequency modulation
US2374000A (en) * 1943-03-06 1945-04-17 Rca Corp Phase modulator
US2430126A (en) * 1943-08-25 1947-11-04 Rca Corp Phase modulation

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2749310A (en) * 1954-09-03 1956-06-05 Shell Dev Lubricating compositions
US3020493A (en) * 1959-02-27 1962-02-06 Hughes Aircraft Co Frequency modulation circuit

Also Published As

Publication number Publication date
FR948331A (fr) 1949-07-28
GB628901A (en) 1949-09-07
BE474098A (xx)

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