US1794932A - Frequency modulation - Google Patents

Frequency modulation Download PDF

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Publication number
US1794932A
US1794932A US216873A US21687327A US1794932A US 1794932 A US1794932 A US 1794932A US 216873 A US216873 A US 216873A US 21687327 A US21687327 A US 21687327A US 1794932 A US1794932 A US 1794932A
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United States
Prior art keywords
frequency
circuits
energy
analyzer
outputs
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Expired - Lifetime
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US216873A
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English (en)
Inventor
George L Usselman
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RCA Corp
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RCA Corp
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Filing date
Publication date
Priority to NL27771D priority Critical patent/NL27771C/xx
Application filed by RCA Corp filed Critical RCA Corp
Priority to US216873A priority patent/US1794932A/en
Priority to DER75333D priority patent/DE515621C/de
Priority to GB25277/28A priority patent/GB296678A/en
Application granted granted Critical
Publication of US1794932A publication Critical patent/US1794932A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D3/00—Demodulation of angle-, frequency- or phase- modulated oscillations
    • H03D3/02—Demodulation of angle-, frequency- or phase- modulated oscillations by detecting phase difference between two signals obtained from input signal
    • H03D3/06—Demodulation of angle-, frequency- or phase- modulated oscillations by detecting phase difference between two signals obtained from input signal by combining signals additively or in product demodulators
    • H03D3/12—Demodulation of angle-, frequency- or phase- modulated oscillations by detecting phase difference between two signals obtained from input signal by combining signals additively or in product demodulators by means of discharge tubes having more than two electrodes

Definitions

  • This invention relates to signalling by frequency modulation, and more particularly to the analysis and detection of received frequency modulated signals.
  • Frequency modulation in the ideal case, should be accompanied by no amplitude mod- .ulation.- However, in actual practice a re ceived frequency modulated wave often does show amplitude variation, for various reasons, such as fading, or fluctuations in the power input to the transmitter, which may occur at a disturbing frequency.
  • the usual type of analyzer circuit consists of a resonant circuit tuned to a frequency lying to one side of the operating frequency range, and its purpose is to change frequency modulation to amplitude modulation. It is obvious that such a circuit will respond to amplitude modulation and therefore the output will be impure. It is an object of my invention to provide an analyzer circuit which will change frequency modulation to amplitude modulation but which will'not respond to amplitude modulations of the energy supplied to it.
  • the analysis be made according to a straight line resonance characteristic in order that the amplitude modulation be a true reproduction 'of the original frequency modulation, to avoid the production of harmonics, and to prevent intermodulation, of multiplex signals. It is also dcsirr able that if the resonance characteristic be curved its curvature be symmetrical in order that the positive and negative halves of the alternating current component of the amplitude modulated energy be identical. For exactly similar reasons it is desirable that the subsequent rectification or detection of the amplitude modulated energy be according to asymmetrical characteristic.
  • harmonics may be used as channel frequencies and the available choice thereby be greatly widened. Accordingly, it is a further object of my invention to provide a balanced circuit which will suppress undesired harmonics.
  • the above described objects are attained by supplying the frequency modulated energy cophasially to each of two circuits having intersectin resonance curves with maxima at frequencies lying either side of the operating range of frequency, applying the potential fluctuations from th the control electrodes of two detector tubes in phase opposition, and combining the outputs from the detector tubes 1n phase opposition.
  • Frequency changes cause one of the two circuits to become more strongly energized than the other, and as the frequency swings to and fro an alternating current component is found in the series connection between the anodes of the two tubes.
  • amplitude variations while causing similar variations in the outputs ofweach of the analyzer circuits, do not affect the resultant output because they are combined in opposition.
  • each half of .theresonance characteristic consists of a similar portion of each of two resonance curves the resonance characteristic and because the effective or combined characteristic is the resultant of two differently curved characteristics the resultant'is more nearly straight, and a wider frequency band may be utilized if desired.
  • the resultant efiective rectification characteristic is made more symmetrical, and by reason of an inherent property of symmetrical circuits numerous harmonics are suppressed.
  • the analyzer as-so far described, requires the use of two analyzer circuits instead of one, which might complicate the operation of tuning the receiver. It is a further object of my invention to provide for uni-control of the two circuits, and this is most simply done by employing arrangements quite similar to those which have been developed in connec- ASSIGNOR 'J!O RADIO CORPORA- is symmetrical,
  • this may consist of a straight line tuning condenser in each of the two analyzer circuits, with means to vary them simultaneously, and additional means to adjust their frequency separation.
  • Figure 1 is a wiring diagram and schematic representation of one form of my invention; that because the on vature of the combined halves of the worki g portions of the reso- Figure 2 is-a resonance curve for the analyzer circuits; and Figure 3 represents another form of my Referring to Figure 1 frequency modulated energy is supplied by means of the conductors 2 to the resonant analyzer circuits 4 and-6, by way of coupling transformers 8 and 10.
  • the frequency increases towards F 2 the hi her frequency circuit 6 will be more strong y energized, and the lower frequency circuit 4 more weakly energized, and there will be a resultant current flow through the transformer 16 in the opposite direction.
  • tuning condensers inc'ircuits 4 and 6 may be arranged to be vrotated by a single control, and in such case their frequency sepgeared to the condensers by'drive chains 22; The position ,of the condensers relative to their respective chain wheels may be varied by adjusting the location of lock screws 24 in. arcuate slots 26.
  • a worm gear 42 on the shaft of the motor 40, engages with a worm wheel 20, and thereby serves to vary the tuning of the analyzer circuits;
  • Figure 3 is similar to F i ure 1 except for some alternative features w ich are next described.
  • the relay magnets 50 are in this case intended to have'such high inductance that only the direct current component of the anode currents will pass therethrough. There are thus provided three paths in parallel, which according to their respective impedances, serve to separate the desired output alternating energy, the high frequency energy, and the steady anode current.
  • the arrangement shown in Figure 1 is preferable only in this respect, that it is cheaper to provide a blocking condenser, such as those indicated at 32, than it is to provide relay magnets which will efficiently prevent loss of the low frequency alternating component.
  • Figure 3 also difi'ers in that the detecting action of the tubes 12 and 14 is obtained by grid bias, ratherthan by the use of a condenser and grid leak.
  • the choice of bias means is of little consequence except that it must be remembered that the average anode current varies in opposite sense, that is, in the case of rectification by grid condenser the anode current decreases for increased al- .ternatin energy, whereas in the case of negative gri bias the anode current increases for increased alternating energy, and therefore the connection to the automatic tuning control must be reversed.
  • Figure 3 further differs in that a different means for controlling the frequency separation of the resonantcircuits is indicated.
  • the input tothe analyzer circuit may be energy of intermediate frequency obtained by heterodyning the and that the output from the detector may be separated into various channels in the case of multiplex signalling.
  • the detectors may be any suitable device of asymmetric characteristic.
  • the method of discriminating between amplitude modulation and frequency modulation when analyzing frequency modulated energy which includes supplying the energy in a desired phaserelation to each of two circuits tuned to frequencies lying either side of the operating range of frequency, and combining the outputs from the two circuits in an opposite phase relation.
  • the method of obtaining a symmetrical and substantially straight resonance characteristic for analyzing frequency modulated energy which includes supplying the energy in one phase relation to each of two circuits having intersecting resonance curves with maxima 1 ing either side of the operating range of f iequency, and combining the outputs from the two circuits in an opposite phase relation.
  • the method of obtaining symmetrical and substantially straight resonance and symmetrical detection characteristics for analyzing and rectifying frequency modulated energy which includes supplying the energy cophasially to each oftwo circuits having intersecting resonance curves with maxima lying either side of the operating range of frequency, detectin the outputs from the two circuits, and com ining the de tected outputs in phase opposition.
  • the method of eliminatin the occurrence of undesired harmonics w en rectifying analyzed frequency modulated energy which includes detecting a. portion of the analyzed energy, detecting another portion of the analyzed ener and combining the detected outputs in ase opposition.
  • the method 0 analyzing and rectifying frequency modulated energy which in cludes sn 1 in the ener in one base relation t dabh f two circi l i ts having ihtersecting resonance curves with maxiina lying either side of the operating range of frequency, separately etecting the potential uctuations in each of the two circuits in an opposite phase relation, and combining the detected outputs in opposite phase relation.
  • An analyzer for energy which is frequency modulated in accordance with a desired signal comprising a resonant circuit tuned to a frequency lying at one side of the operating range of frequency, another resonant circuit tuned to a frequency lying at the other side of the operating range of fre quency, means to supply the frequency modulated energy to the two circuits in a desired phase relation, and means for combining the outputs from the two circuits in an opposite phase relation to obtain energy modulated in amplitude in accordance with the desired signal.
  • quency modulated in accordance with a desired signal comprising two resonant circuits having intersecting resonance curves with maxima lying either side of the operating range of frequency, means to supply the frequency modulated energy to the two circuits -in .one phase relation, and means for combining the outputs from the two circuits in an opposite phase relation toobtain energy modulated in amplitude in accordance with the desired signal.
  • An analyzer and detector for frequency modulated signals comprising two resonant circuits having intersecting resonance curves with maxima lying either side of the operating range of frequency, two rectifying means, means to supply the frequency modulated energy to the circuits in one phase relation, means toapply energy of an opposite phase relation from the cirruits to the rectifying means, and means to combine the outputs of the rectifying means preparatory to translation of the signal.
  • An analyzer and detector for frequency modulated signals comprising two resonant circuits having intersecting resonance curves with maxima lying either side of the operating range of frequency, two detector tubes having control electrodes, means to supply the frequency modulated energy 'to the circuits cophasially, means to apply potential fluctuations fromthe circuits to the control electrodes in phase opposition, and means to combine the tube outputs in phase opposition preparatory to translation of the signal.
  • An automatically tuned balanced analyzer comprising two'resonant circuits having intersecting resonance curves with ma nmalying either side of the operating range
  • An automatically tuned balanced an-' alyzer and detector comprising two resonant circuits having intersecting'resonance curves with maxima lying either side of the operating range of frequency, variable reactances for tuning said circuits, a plurality of detectors, means to supply energy to the circuits in one phase relation, means to feed the detectors from the circuits inan opposite phase relation, means to combine the alternating components of'the detector outputs likewise in opposite phase relation, and means responsive to a difference in the steady components of the detector outputs for automatically changing the magnitude of the variable reactances to lessen the difference.
  • An analyzerfor frequency modulated energy comprising two resonant circuits having intersecting resonance curves with maXima lying either-side of the operating range of frequency, means to supply the frequency modulated energy to the twocircuits in one phase relation, means for combining the outputsfrom the two circults in an opposite phase relation, a straight line frequency condenser in each of the resonant circuits, means to vary them simultaneously, and "means to I adjust their frequency separation.
  • An analyzer and detector for frequency modulated signals comprising two resonantcircuits havin intersecting resonance curves with maxima Tying either side of the operating'range of frequency, two rectifying means,
  • An analyzer and detector for frequency modulated signals comprising two resonant circuits having intersecting resonance curves with maxima lying either sideof the operating range of frequency, two rectifying means, means to supply the frequency modulated energy. "to the circuits in one phase relation,
  • An analyzer and detector for frequency modulated signals comprising two resonant circuits having intersecting resonance curves with maxima lying either side ofthe operating range of frequency, two detector tubes having control electrodes, means to supply the frequency modulated energy to the circuits cophasially, means toapply potential fluctuations from the circuits to the control electrodes in phase opposition, means to combine the tube outputs in phase opposition, a straight line frequency condenser ,1n each of the resonant circuits, a reversible motor for varying the condensers simultaneously,

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
  • Transmitters (AREA)
US216873A 1927-09-01 1927-09-01 Frequency modulation Expired - Lifetime US1794932A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
NL27771D NL27771C (enrdf_load_stackoverflow) 1927-09-01
US216873A US1794932A (en) 1927-09-01 1927-09-01 Frequency modulation
DER75333D DE515621C (de) 1927-09-01 1928-08-05 Demodulationsschaltung zum Empfang frequenzmodulierter Wellen
GB25277/28A GB296678A (en) 1927-09-01 1928-09-03 Improvements in or relating to radio and the like receivers

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US216873A US1794932A (en) 1927-09-01 1927-09-01 Frequency modulation

Publications (1)

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US1794932A true US1794932A (en) 1931-03-03

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US216873A Expired - Lifetime US1794932A (en) 1927-09-01 1927-09-01 Frequency modulation

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US (1) US1794932A (enrdf_load_stackoverflow)
DE (1) DE515621C (enrdf_load_stackoverflow)
GB (1) GB296678A (enrdf_load_stackoverflow)
NL (1) NL27771C (enrdf_load_stackoverflow)

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2415469A (en) * 1943-02-25 1947-02-11 Purdue Research Foundation Electrical control apparatus
US2417191A (en) * 1942-01-13 1947-03-11 Southwest Airmotive Company Airplane antenna automatic tuning system
US2425923A (en) * 1945-03-07 1947-08-19 Rca Corp Frequency divider and discriminator circuit
US2428264A (en) * 1943-04-27 1947-09-30 Rca Corp Frequency discriminator circuits
US2465448A (en) * 1936-11-27 1949-03-29 Rca Corp Wave length modulated wave signaling
US2494677A (en) * 1942-11-13 1950-01-17 Hartford Nat Bank & Trust Co Radio receiver with condenser tuning
US2498340A (en) * 1945-01-22 1950-02-21 Rca Corp Antenna tuning control system
US2519668A (en) * 1944-09-04 1950-08-22 Sidney S Konigsberg Indicating system
US2545297A (en) * 1946-03-13 1951-03-13 Mittelmann Eugene Oscillation frequency control
US2747146A (en) * 1952-02-12 1956-05-22 Cook Electric Co Frequency enseitive control apparatus
US2812510A (en) * 1952-06-25 1957-11-05 Elmer H Schulz Frequency modulation system
US2820109A (en) * 1952-03-22 1958-01-14 Cgs Lab Inc Magnetic amplifier
US2830241A (en) * 1954-07-21 1958-04-08 Turck Jean Telecontrol device
US2901614A (en) * 1957-03-14 1959-08-25 Collins Radio Co Coarse frequency discriminator
US2915741A (en) * 1955-11-16 1959-12-01 Tele Dynamics Inc Automatic compensation in a telemetric system
US2929876A (en) * 1955-06-10 1960-03-22 Metallotecnica Soc Automatic frequency control device of very high stability and highly sensitive for radio receivers
US2996681A (en) * 1960-01-07 1961-08-15 Admiral Corp Transistorized peak detector
US3074021A (en) * 1958-04-03 1963-01-15 Gen Electronic Lab Inc Crystal discriminator
US3241077A (en) * 1961-07-06 1966-03-15 North American Aviation Inc Self-adaptive control system eliminating variable unwanted component
US3365147A (en) * 1965-04-12 1968-01-23 Honeywell Inc Control apparatus for steerable craft

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE758225C (de) * 1937-04-13 1953-04-16 Rca Corp Schaltung zur Stabilisierung der mittleren Traegerfrequenz eines frequenz- oder phasenmodulierten Hochfrequenzsenders
DE753551C (de) * 1939-04-15 1953-03-09 Fernseh Gmbh Verfahren und Einrichtung zum Empfang einer mittels frequenzmodulierter Wellen uebertragenen Signalfolge

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2465448A (en) * 1936-11-27 1949-03-29 Rca Corp Wave length modulated wave signaling
US2417191A (en) * 1942-01-13 1947-03-11 Southwest Airmotive Company Airplane antenna automatic tuning system
US2494677A (en) * 1942-11-13 1950-01-17 Hartford Nat Bank & Trust Co Radio receiver with condenser tuning
US2415469A (en) * 1943-02-25 1947-02-11 Purdue Research Foundation Electrical control apparatus
US2428264A (en) * 1943-04-27 1947-09-30 Rca Corp Frequency discriminator circuits
US2519668A (en) * 1944-09-04 1950-08-22 Sidney S Konigsberg Indicating system
US2498340A (en) * 1945-01-22 1950-02-21 Rca Corp Antenna tuning control system
US2425923A (en) * 1945-03-07 1947-08-19 Rca Corp Frequency divider and discriminator circuit
US2545297A (en) * 1946-03-13 1951-03-13 Mittelmann Eugene Oscillation frequency control
US2747146A (en) * 1952-02-12 1956-05-22 Cook Electric Co Frequency enseitive control apparatus
US2820109A (en) * 1952-03-22 1958-01-14 Cgs Lab Inc Magnetic amplifier
US2812510A (en) * 1952-06-25 1957-11-05 Elmer H Schulz Frequency modulation system
US2830241A (en) * 1954-07-21 1958-04-08 Turck Jean Telecontrol device
US2929876A (en) * 1955-06-10 1960-03-22 Metallotecnica Soc Automatic frequency control device of very high stability and highly sensitive for radio receivers
US2915741A (en) * 1955-11-16 1959-12-01 Tele Dynamics Inc Automatic compensation in a telemetric system
US2901614A (en) * 1957-03-14 1959-08-25 Collins Radio Co Coarse frequency discriminator
US3074021A (en) * 1958-04-03 1963-01-15 Gen Electronic Lab Inc Crystal discriminator
US2996681A (en) * 1960-01-07 1961-08-15 Admiral Corp Transistorized peak detector
US3241077A (en) * 1961-07-06 1966-03-15 North American Aviation Inc Self-adaptive control system eliminating variable unwanted component
US3365147A (en) * 1965-04-12 1968-01-23 Honeywell Inc Control apparatus for steerable craft

Also Published As

Publication number Publication date
NL27771C (enrdf_load_stackoverflow)
GB296678A (en) 1929-02-07
DE515621C (de) 1931-01-09

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