US2315308A - Method and means for transmitting frequency modulated signals - Google Patents

Method and means for transmitting frequency modulated signals Download PDF

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Publication number
US2315308A
US2315308A US349870A US34987040A US2315308A US 2315308 A US2315308 A US 2315308A US 349870 A US349870 A US 349870A US 34987040 A US34987040 A US 34987040A US 2315308 A US2315308 A US 2315308A
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United States
Prior art keywords
frequency
oscillator
current
modulated signals
frequency modulated
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Expired - Lifetime
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US349870A
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English (en)
Inventor
Edwin H Armstrong
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Individual
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Individual
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Publication date
Priority to BE472792D priority Critical patent/BE472792A/xx
Application filed by Individual filed Critical Individual
Priority to US349870A priority patent/US2315308A/en
Application granted granted Critical
Publication of US2315308A publication Critical patent/US2315308A/en
Priority to GB1000/47A priority patent/GB623222A/en
Priority to FR946308D priority patent/FR946308A/fr
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
    • H03C3/02—Details
    • H03C3/09—Modifications of modulator for regulating the mean frequency
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C3/00—Angle modulation
    • H03C3/38—Angle modulation by converting amplitude modulation to angle modulation
    • H03C3/40—Angle modulation by converting amplitude modulation to angle modulation using two signal paths the outputs of which have a predetermined phase difference and at least one output being amplitude-modulated

Definitions

  • This invention has for its object the elimina tion of disturbances resulting from frequency changes in radio transmitting systems, particularly of the type described in my U. S. Patent #1,941,068 for producing wide band frequency modulated signals.
  • the frequency modulated signal is produced by changing the phase of a current derived from a relatively low frequency oscillator whose frequency is usually crystal controlled.' This initial phase shift is then multiplied a great many times until the desired frequency change is produced at the frequency which is to be radiated.
  • small irregularities in the constancy of the frequency of the oscillator give rise to various difficulties, and it is the purpose of this invention to eliminate them.
  • the single ligure illustrates the general arrangement of the apparatus which will be understood from the following description.
  • An arrangement now in common use for producing a frequency modulated current of 100 kc. deviation at approximately 40 megacycles consists of a crystal controlled oscillator having a frequency of 200 kc., a ⁇ phase shifting device.
  • the frequency multiplication is usually accomplished in two steps, the first step being up to some convenient multiple of the 200 kc. from which it is heterodyned down to some relatively lowerfrequency that is a sub-multiple of the frequency to be radiated, and this in tum is multiplied upto the nal value. It has been common practice to multiply up to a frequency of 12.8 megacycles, which is then heterodyned down to some frequency in thevicnity of 900 kc. This frequency is then in turn multiplied up to the vicinity of 40 megacycles.
  • a heterodyning current of 11.925 megacycles would be combined to produce a difference frequency of 875 kc. which would then be multiplied 48 times to produce a 42,000 kilocycle current.
  • the total frequency multiplication amounts toA 3072 times.
  • the frequency of the 'initial crystal oscillator is not a constant quantity but varies minutely due to irregularities of filament emissions and to various other effects and while these changes are extremely minute, after a multiplication of several thousand fold they become perceptible.
  • the drift of frequency due to temperature changes of either crystal may cause a resultant change in frequency of the transmitted wave of an undesired amount. This is particularly true with respect to the higher frequencies.
  • the present invention has for its object the reduction of all these effects to such'v a very small percentage of their i original amount that they become of negligible importance.
  • 'Ihe invention proposes to accomplish this by deriving the current for the second oscillating source from the initial oscillator so that any changes in frequency of the first oscillator, whether slow or fast, will be substantially cancelled out in the conversion of frequency down to the submultiple of the frequency to be radiated.
  • I represents the oscillator of some lowfrequency
  • 2 the usual carrier amplifier and 3 the usual balanced modulator employed in producing the initial phase shift
  • 4 l, 6, l, 8, i represent the usual series of doublers forraising the oscillator frequency which in the present case is taken for example as 200 kc.
  • pliers I0, I I, I2, I3 I4 composed of two triplers and three doublers raise the frequency to 14,400 kilocycles.
  • I5 is a converter for combining the 12.8 megacycle modulated'current with the 14.4 megacycle unmodulated current to, give a resultant frequency modulated current of 1600 kilocycles.
  • I6, I1, I8, I 9 and 20 represent a series of doublersand triplers to raise the frequency to 115.2 megacycles.
  • represents the usual power amplifier and 22 the antenna. 23 represents the usual correction amplifier.
  • the method of reducing disturbances which arise due to the extremely minute inherent variations in the frequency of the initial oscillator of a wide swing frequency modulation system which consists in dividing the current from the oscillator into a plurality of paths, changing the phase of the current derived from said oscillator in one of said paths without introducing into said path disturbances of greater magnitude than that of the disturbances inherent in the said oscillator, multiplying in said path the frequency of the modulated currents to produce a higher second frequency, multiplying in said other path the frequency of the current derived from the initial oscillator to produce a third frequency which differs from the second frequency by an amount which is a sub-multiple of the frequency to be transmitted, beating the second'frequency and third frequency together to produce a fourth frequency, multiplying the fourth frequency to the frequency to be transmitted, the total multiplication effected by the several multiplying steps being of the order of several thousand fold, and transmitting the currents of the resulting frequency.

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  • Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)
  • Amplitude Modulation (AREA)
US349870A 1940-08-02 1940-08-02 Method and means for transmitting frequency modulated signals Expired - Lifetime US2315308A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
BE472792D BE472792A (fr) 1940-08-02
US349870A US2315308A (en) 1940-08-02 1940-08-02 Method and means for transmitting frequency modulated signals
GB1000/47A GB623222A (en) 1940-08-02 1947-01-11 Method and means for transmitting frequency modulated signals
FR946308D FR946308A (fr) 1940-08-02 1947-05-07 Procédés et moyens pour l'émission de signaux de fréquence modulée

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US349870A US2315308A (en) 1940-08-02 1940-08-02 Method and means for transmitting frequency modulated signals

Publications (1)

Publication Number Publication Date
US2315308A true US2315308A (en) 1943-03-30

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ID=23374312

Family Applications (1)

Application Number Title Priority Date Filing Date
US349870A Expired - Lifetime US2315308A (en) 1940-08-02 1940-08-02 Method and means for transmitting frequency modulated signals

Country Status (4)

Country Link
US (1) US2315308A (fr)
BE (1) BE472792A (fr)
FR (1) FR946308A (fr)
GB (1) GB623222A (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2660708A (en) * 1949-11-09 1953-11-24 Theodore H Nakken Frequency division

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2660708A (en) * 1949-11-09 1953-11-24 Theodore H Nakken Frequency division

Also Published As

Publication number Publication date
BE472792A (fr)
GB623222A (en) 1949-05-13
FR946308A (fr) 1949-05-31

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