US2393785A - Carrier modulation - Google Patents

Carrier modulation Download PDF

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Publication number
US2393785A
US2393785A US464341A US46434142A US2393785A US 2393785 A US2393785 A US 2393785A US 464341 A US464341 A US 464341A US 46434142 A US46434142 A US 46434142A US 2393785 A US2393785 A US 2393785A
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United States
Prior art keywords
modulation
network
load
variable
source
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
US464341A
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English (en)
Inventor
Laurance M Leeds
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.)
General Electric Co
Original Assignee
General Electric Co
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 BE474679D priority Critical patent/BE474679A/xx
Application filed by General Electric Co filed Critical General Electric Co
Priority to US464341A priority patent/US2393785A/en
Priority to GB18180/43A priority patent/GB567517A/en
Application granted granted Critical
Publication of US2393785A publication Critical patent/US2393785A/en
Priority to FR950308D priority patent/FR950308A/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/02—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
    • H03F1/04—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in discharge-tube amplifiers
    • H03F1/06—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in discharge-tube amplifiers to raise the efficiency of amplifying modulated radio frequency waves; to raise the efficiency of amplifiers acting also as modulators
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C1/00—Amplitude modulation
    • H03C1/08—Amplitude modulation by means of variable impedance element
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C7/00—Modulating electromagnetic waves
    • H03C7/02—Modulating electromagnetic waves in transmission lines, waveguides, cavity resonators or radiation fields of antennas

Definitions

  • the object of my invention is to provide an improved and more efllcient arrangement for modulating a carrier wave, I
  • Figs. 1 to 4 inclusive represent carrier modulation circuits
  • Figs. 5 to 8 inclusive represent networks for obtaining a variable inductance through the use of a variable capacity
  • Figs. 9 to 12 inclusive represent networks for obtaining a variable capacit through the use of a variable inductance
  • Fig. 13 represents a variable capacity having its value determined by the instantaneous modulating potential applied to its control electrode.
  • Figs. 1 to 4 inclusive there is shown a source of radio frequency power I having output terminals 2 coupled through reactance networks consisting of-quarter wavelength artificial transmission lines I, I, I, and 8 to a load, such as an antenna, represented by a resistance 1.
  • the reactance networks are made up of inductances I and condensers s which are varied in magnitude at themodulating frequency to produce a variation in the coupling between the power source and its load, thereby modulating the power output.
  • Equation 1 is the envelope equation of a distortionless modulated signal.
  • the modulation network 3 is made up of reactances, all of the power fed into the network must appear in theload resistance I. From this it follows that the power input is equal to the power appearing in the resistance 1 where e. and 2!:- are, respectively the instantaneous and maximum voltages across the load resistance 1, m is the modulation percentage p is the modulating frequency angular velocity, d
  • Equation Q I z--- 3 where en, the instantaneous voltage across terminals 2 of the R. F. power source is equal to E0 cos .wt. From Equations 1, 2, and 3 the instantaneous value of the reactances in the network is given by the equation 0. E.(l+m cos pt) cos wt ('4) From Equation 4 is apparent that, in order to obtain the distortionless modulated signal defined by Equation 1, itis necessary that the reactances in the modulation networks vary at modulation frequency in accordance with the equation constant 1+m cos pt (5) equal to zero and the network reactances are infinite.
  • the circuits of Figs. 5 to 8 inclusive are quarter wavelength artificial transmission lines made up of fixed condensers l and inductanoes it having variable condensers i2 connected across output terminals l3 which, due to the circuit constants, appear at the input terminals H as variable inductances.- Any one of the networks shown in Figs. to 8 may be substituted for the variable inductances in the modulation networks of Figs. 1 to 4 inclusive and will provide at the terminals ll an apparent inductanc given by the equation where L is the apparent inductance, X is the reactance of the fixed inductanoes and condensers in the networks, and C is the instantaneous capacity of variable condenser i2.
  • the circuits of Figs. 9 to 12 inclusive are made up of fixed condensers l5 and inductances I! having output terminals l1 shunted by variable inductances l8 which, due to the circuit constants, appear as variable condensers at the input terminals IQ of the network. Any of the circuits shown in Figs. 9 to 12 inclusive may be substituted for the variable condensers in the modulation networks of Figs. 1 to 4 inclusive and provide at the terminals i an apparent capacity given by the equation I where C is the apparent capacity, X is the reactance of the fixed condensers and inductances in the network, and L i the instantaneous inductance of the variable inductances l8.
  • Fig. 13 is shown a variable condenser of the construction disclosed in Patent 2,243,829, Brett et al., which is capable of modulation frequency variation necessary for operation of the modulation networks although the range of variation is not suillcient for 100 per cent modulation.
  • This condenser comprises an evacuated envelope 2
  • the electrons from the cathode pass through slits in a control electrode 24, in an accelerating electrode 25, and in a screen suppressor electrode 26, and are collected on a plate 21.
  • the screen suppressor electrode 22 shields the condenser plate 2!
  • the beam of electrons passing between the condenser plates varies the dielectric constant and, since the beam is controlled by the potential e. applied to the control electrode 24, the capacity appearing at the condenser terminals 22 is directly related to the potential at the control electrode 24. Due to the inertialess nature of the electron beam, the eflective capacity appearing at the terminals 28 can be varied at a high frequency.
  • the efliciency is the instantaneous efllciency of the power source, i. e., the eillciency of the power source at the particular loading existing at that instant, and is independent of the modulation percentage.
  • ' power source may be an oscillator, power amplifier, or other device and will have an efficiency dependent upon its design. If the power source is a class C amplifier, its instantaneous efficiency can be very high and in general will be in excess of 70 per cent at any modulation percentage.
  • the transmission apparatus disclosed above is applicable to any modulated transmitter and should result in a very simple high power broadcast or television transmitter.
  • Transmission apparatus comprising a source of carrier, a quarter wavelength artificial transmission line, made up of variable series and shunt reactances, for connecting the carrier output with a load, and means for varying simultaneously each of said reactances at modulating frequency to modulate the carrier output while maintaining constant the electrical length of the line.
  • a source of constant voltage of carrier frequency is supplied through a reactance network to a load, said network having an electrical length equal to a quarter or a wavelength or odd multiple thereof at the frequency of said source, the method of modulating the amplitude of voltage supplied to said load without modulating the phase thereof which comprises varying the characteristic impedance of said network while maintaining constant the electrical length of the network.
  • a source of carrier wave oscillations a load, a reactance network connected between said source and load.
  • said network comprising series reactance of one sign and shunt reactance of opposite sign and having an electrical length equal to an odd multiple or a quarter of a wavelength, a plurality of capacitance devices, each corresponding to one of said reactances and each having capacitance of value corresponding to modulating voltage applied thereto, means to apply thereto modulating voltage in accord with which it is desired to modulate said carrier wave oscillations supplied to said load and means to modulate each of said positive and negative reactances in accord with the corresponding one 01' said capacitances thereby to vary the voltage supplied to said load, said positive and negative reactances being varied in such relation as to maintain constant the electrical length of said network between said source and load.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Transforming Electric Information Into Light Information (AREA)
  • Transmitters (AREA)
US464341A 1942-11-03 1942-11-03 Carrier modulation Expired - Lifetime US2393785A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
BE474679D BE474679A (fr) 1942-11-03
US464341A US2393785A (en) 1942-11-03 1942-11-03 Carrier modulation
GB18180/43A GB567517A (en) 1942-11-03 1943-11-03 Improvements in and relating to arrangements for carrier modulation
FR950308D FR950308A (fr) 1942-11-03 1946-10-22 Système de modulation à haut rendement

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US464341A US2393785A (en) 1942-11-03 1942-11-03 Carrier modulation

Publications (1)

Publication Number Publication Date
US2393785A true US2393785A (en) 1946-01-29

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Family Applications (1)

Application Number Title Priority Date Filing Date
US464341A Expired - Lifetime US2393785A (en) 1942-11-03 1942-11-03 Carrier modulation

Country Status (4)

Country Link
US (1) US2393785A (fr)
BE (1) BE474679A (fr)
FR (1) FR950308A (fr)
GB (1) GB567517A (fr)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2492168A (en) * 1948-04-03 1949-12-27 Int Standard Electric Corp Modulator
US2577972A (en) * 1948-11-13 1951-12-11 Emi Ltd Circuit arrangement for stabilizing the amplitude of electrical oscillations
US2615983A (en) * 1950-05-05 1952-10-28 Avco Mfg Corp Tuner for television receivers
US2633529A (en) * 1950-05-03 1953-03-31 George V Eltgroth Frequency selective network
US2691765A (en) * 1952-04-05 1954-10-12 Bell Telephone Labor Inc Electron discharge device
US3132313A (en) * 1959-08-13 1964-05-05 Alford Andrew Impedance matching filter
US3296520A (en) * 1961-10-26 1967-01-03 William F Griffith Electrically controlled variable resistance
US3343088A (en) * 1963-12-12 1967-09-19 Westinghouse Electric Corp Wideband high efficiency transmitter system
US3766313A (en) * 1972-08-07 1973-10-16 Rca Corp Circuit for transmitting digital signals to conventional television receiver
US3792302A (en) * 1972-12-22 1974-02-12 Raytheon Co Vhf slow wave structure

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2941269B1 (fr) 2009-01-19 2015-07-03 Peugeot Citroen Automobiles Sa Culasse de moteur de vehicule automobile.

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2492168A (en) * 1948-04-03 1949-12-27 Int Standard Electric Corp Modulator
US2577972A (en) * 1948-11-13 1951-12-11 Emi Ltd Circuit arrangement for stabilizing the amplitude of electrical oscillations
US2633529A (en) * 1950-05-03 1953-03-31 George V Eltgroth Frequency selective network
US2615983A (en) * 1950-05-05 1952-10-28 Avco Mfg Corp Tuner for television receivers
US2691765A (en) * 1952-04-05 1954-10-12 Bell Telephone Labor Inc Electron discharge device
US3132313A (en) * 1959-08-13 1964-05-05 Alford Andrew Impedance matching filter
US3296520A (en) * 1961-10-26 1967-01-03 William F Griffith Electrically controlled variable resistance
US3343088A (en) * 1963-12-12 1967-09-19 Westinghouse Electric Corp Wideband high efficiency transmitter system
US3766313A (en) * 1972-08-07 1973-10-16 Rca Corp Circuit for transmitting digital signals to conventional television receiver
US3792302A (en) * 1972-12-22 1974-02-12 Raytheon Co Vhf slow wave structure

Also Published As

Publication number Publication date
BE474679A (fr)
FR950308A (fr) 1949-09-23
GB567517A (en) 1945-02-16

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