US2259000A - Transmission of frequency modulated waves - Google Patents

Transmission of frequency modulated waves Download PDF

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Publication number
US2259000A
US2259000A US209183A US20918338A US2259000A US 2259000 A US2259000 A US 2259000A US 209183 A US209183 A US 209183A US 20918338 A US20918338 A US 20918338A US 2259000 A US2259000 A US 2259000A
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United States
Prior art keywords
frequency
waves
band
incoming
circuit
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Expired - Lifetime
Application number
US209183A
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English (en)
Inventor
Nyquist Harry
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AT&T Corp
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Bell Telephone Laboratories Inc
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Publication date
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US209183A priority Critical patent/US2259000A/en
Priority to GB12788/39A priority patent/GB528152A/en
Priority to FR854976D priority patent/FR854976A/fr
Priority to NL93492A priority patent/NL61925C/xx
Priority to CH234266D priority patent/CH234266A/fr
Application granted granted Critical
Publication of US2259000A publication Critical patent/US2259000A/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
    • H03C3/02—Details
    • H03C3/06—Means for changing frequency deviation

Definitions

  • 'Another objector the invention is to reduce the relative efiec-t with respect to the desired signal of interference which consists of very sudden iinpiil ses.
  • incoming frediiency mo ulated Siren/es are demodulated in any desired'rn'anner after first being subjected to the selective action of a network having the ,geiieral'charac'terifstics of a band-pass filter.
  • Fig. 2 shows a modification of the circuit of Fig. 1 provided with ineans "for counteracting the distortion occasioned by the variable magnetic inductance; and v v Fig. 3 illustrates anbther modification in Which the automaticall varyin selective networkof Figs. 1 and 2 is empleyed in afrequency moduiated wave detection 'Systein of th 'rwise converition'al type.
  • the incoming antenna or receiving circuit 4 is connected by transformer 5 to ".the input circuitsof two detectors ,each of iivhi'chdmay be of the electron discharge type, Shiintd 'acros's "the 'transfornier inpiit circuit is 1938, S ri aI'NO. 209,183
  • nqomin H e Bis inclpded 'nge ifisuwithqbiasihg r co roil ng winding lficto determinethe normal" tomo'tive force to which the core l5 isjfsfiihi cted x
  • the 'seiective network B iss-inrilar totheptuned circuit l3 a a inc ludes a inductance elementiS similar to the'ingncta nce element l4 andwhich is controlled in the same way Joya magnetic core 2B and a control winding ⁇ ! connected in series th s "is 's'u lat on.
  • the result of the combination of the two electromotive forces of this same frequency and in phase quadrature by the detectors is to produce no response in the outputcircuits' of the detectors so that the circuit of source l8 and the series windings l6 and 2
  • the circuit 6 which, as previously explained, is anti-resonant at the unmodulated carrier frequency waves serves as a by-pass to substantially divert from the transformer 5 other disturbing electromotive forces which may be of substantially more than 3,000 cycles frequency difference from the received unmodulated carrier wave.
  • the incoming wave at the receiving station will depart from the normal unmodulated carrier frequency by an amount determined by several factors including the modulation index of the transmitting system, the intensity of the modulating signal and the rate at which the intensity of the modulating signal is changing.
  • the tendency will be for the frequency of the band of essential incoming components to shift to such an extent that it will depart from the range which the circuit 6 is normally set to exclude.
  • the initial condition of phase quadrature at the input circuit of detectors I and 8 between the received wave and the locally produced wave will no longer subsist.
  • the change in frequency of the incoming wave will cause the electromotive force impressed by transformer 5 to fall more nearly in phase with the local oscillation in one detector and to increase the phase difference angle in the input circuit of the other detector.- Consequently, the space current in one detector as, for example, in detector 1 will tend to rise with a consequent increase in the potential difference across the resistance 22 in the output circuit of that detector. In converse manner, the space current of detector 8 will diminish as will the potential difference across the resistance 23 associated with that detector.
  • points 24 and 25'at the outer extremities of the two resistances were originally at equal potentials so far as the effect of space current is concerned, they now tend to assume different potentials and consequently there is-elfective in the circuit of the source it an additional electromotive force which may either aid or oppose the source I8 according to the polarity of the latter.
  • the source I8 is so poled that the effect of the additional electromotive force set up between the points 24 and 25 by the unbalance in the detector circuits is to so change the bias or control current through the winding l6 as to cause the reactance of the element M to change the tuning of the loop I3 in the same direction that the frequency of the incoming waves has changed.
  • the instantaneous effect of the frequency modulation is to increase the frequency of the incoming waves
  • the effect of the unbalance potentials between points 24 and 25 is to correspondingly increase the frequency of the oscillations from the source ll.
  • the ideal relationship for balance requires that the phase quadrature between the incoming waves and the locally produced waves be maintained. This condition may be specified if at all times the locally produced oscillations faithfully follow the frequency of the incoming waves with no delay.
  • Reverse feedback circuits of the stabilized amplifier type are very well known in the electrical transmission art. It may perhaps be appreciated that the circuit of detectors 1 and 8, biasing circuit of source l8 and control winding I6 and oscillator l l is a species of reverse feedback circuit in which the audio frequency detected components are fed back from the outputs of the detectors "i and 8 through frequency modulation of the oscillator l I in such manner as to reduce the resultant detected component. If the amplification which the energy undergoes in the reentrant loop involving the detectors and the feedback circuit is made very high the tendency of the circuits to introduce distortion is reduced and the effective detected audio frequency electromotive force between the points 24 and 25 will tend to faithfully reflect the variations in frequency of the incoming wave.
  • the desired band of essential frequencies is excluded by the circuit 6 and is effectively transmitted to the transformert while frequency components which were previously transmitted to the transformer are now attenuated.
  • the selective network 6 follows the incoming wave frequency accepting a relatively narrow band of essential frequencies and suppressing components of frequencies outside that band.
  • the noise energy is distributed throughout the entire range which the incoming wave traverses only a small portion of it will fall within the passed band at any particular instant; the major portion falling within the suppressed or highly attenuated poi"- tion of the range.
  • Thisexpe'dient therefore enables the receiver to accept the essential frequencies of the desired signal even though these frequencies vary from instant to instant and at the same time to exclude the major portion of extraneouswaves occurring in the over-all range of theincomingsi'gnal.
  • the average interference will be reduced so that the improvement amounts to aboutlO decibels.
  • the most common form of interference is not usually a steady form but one which consists of very sudden impulses.
  • the narrow range filter of applicants invention effects a particularly important result in reduction of noise produced by Very sudden impulses.
  • the filter is very effective in reducing noise it may in some instances introduce certain forms of distortion in the wave which would not otherwise be present.
  • the circuit of Fig. 2 may be employed.- In thiscircuit similar elements are designated as in the circuit of Fig. 1.
  • the circuit of Fig. 2 differsfrom that of Fig. 1 in the introduction between the output terminals of the oscillator II and the transformer; 9. ll] of a 'vario-filter 31, made as nearly like the vario-.
  • filter 6 as is practicable and similarly controlled by a control winding 29 associated with the variomagnetic reactance winding 38 serves to nullify the distortion eifects produced by the filter 6 by causing the variable shunting and distorting action of network 3'l upon the local oscillations to correspond at all times to the variable shunting and distortingaction of network 6 upon the received waves so that the phase quadrature condition is maintained.
  • Fig. 3 the system for controlling the variofilter 6 and for varying the frequency of the local oscillator H and of its output vario-filter 31 is identical with that shown in Fig. 2. It will be observed therefore that across points and 39 between thevario-filter 6 and the transformer 5 there may-be derived a narrow band of the essential frequencies of the incoming frequency modulated wave which has been largely "ed rrcm the normally attendant extraneous noise pulsesand other interfering waves by the action of the vario filter. I It is, therefore, possible to connect a circuit such as 3
  • the de modulating-system in this instance involves the transformer 32,"th e combined amplifier and Hill-'- iter 33 of well-known type, the frequency 'de modulator 34; audio frequency transformer 35 and a signal indicator'iiii. 7 It will be apparent that in this system, as in those of Figs. land 2; the advantage of the automatically controlled var -'filter feature isfully attained.-
  • the method of receiving carrier waves are frequency modulated in accordance hon-periodic signals and of reducing the effect "of disturbing energy of frequencies differing from the instantaneous frequency of the received c r; rier waves which comprises highly attenuating all received components differing in frequency by more than a prassigned value from the stantaneous frequency of the received modulated waves so as tol'eave relatively unattenuated band of substantially fixed width but the limiting frequencies of which constantly change and at any instant are determined by the instantaneous frequency of the received waves and frequency demodulating the unattenuate'd frequency band components whereby signals correspondin'g' to the original modulations maybe derived and noises incident to the attenuated frequency ranges may bee'liminated.
  • the method of receiving carrier waves ire-- quehcy modulated by non-periodic waves which comprises accepting only a limited band of fre-' quen'cies essential for demodulation and varying the limits of the accepted band in thesame f'rueasy direction and to the same frequency ex: tent as the instantaneous frequency of there ceived modulated waves varies so as to deriv at all times a band of accepted waves capable upon frequency modulation of yielding non periodic waves corresponding to those "by which the coming modulated waves-are frequency modulated. 3.
  • a system for receiving waves frequency modulated in accordance with non-periodic signals comprising a selective network having an effective transmission band of sufficient width to accept the components of incoming waves of the essential frequencies required for detection, means connected thereto for detecting the waves transmitted by the network, and means under the control of the detected waves for varying characteristics of the network to change the frequency limits of the band which it transmits in the same direction and to the same extent as the instantaneous frequency of the incoming waves varies without changing the width of the band thus causing the central frequency of the transmission band of the network to follow the instantaneous frequency of the incoming waves.
  • a system for receiving waves frequency modulated in accordance with signals comprising a receiving circuit, an attenuating network connected thereto to suppress all components outside a band of preassigned frequency extent centering at the instantaneous received frequency and to select the preassigned band, a frequency demodulating system connected to the receiving circuit to demodulate the selected band of frequencies, and means responsive to the resulting demodulated energy to vary the selective characteristics of the network to cause the central frequency of the selected band characteristic of the attenuating network to follow the instantaneous frequency of the received frequency modulated Waves. '7.
  • a receiving circuit for frequency modulated carrier waves a balanced demodulator having input terminals connected thereto and ontput terminals, an indicating circuit connected to the output terminals, a local oscillator having output terminals connected to the demodulator to impress local oscillations thereon for combination with the frequency modulated waves received by the receiving circuit, a tuned circuit having a magnetic core inductance shunted across the receiving circuit, a similar tuned circuit connected to the oscillator to determine the frequency of the oscillations produced, and a control circuit also connected to the output terminals of the demodulator and to the inductances of both tuned circuits to control the magnitudes of the inductance and to cause the tuning of each tuned circuit to follow the instantaneous carrier frequency of the received carrier waves.
  • the method of receiving frequency modulated waves carrying signal modulations while at the same time reducing the effect of undesired disturbances caused by components of frequencies remote from the instantaneous received frequency comprising selectively transmitting a band of the received waves lying between two limiting frequencies which are separated from each other by a substantially fixed amount and both of which vary in frequency in like manner so as at any instant to be separated from the varying received carrier frequency by respective frequency differences which remain substantially constant of suflicient width to include the essential frequencies required for detection and suppressing frequencies outside the limiting frequencies of the band, detecting the selected band of received waves and causing the detected waves to control the limiting frequencies of the band of waves selected in such manner as to cause the central frequency of the selected unsuppressed band to follow the instantaneous frequency of the incoming waves.
  • the method of receiving frequency modulated waves free from the effects of undesired disturbances occurring in the neighborhood of the instantaneous received frequency comprising selection of a band of frequencies of preassigned frequency extent centering at the instantaneous carrier frequency and the limiting frequencies of which vary in consonance with the instantaneous received frequency so as to remain at substantially fixed separations therefrom, demodulating the selected band of frequencies and utilizing the demodulated waves to vary the limits of the selected band in order to cause its central frequency to follow the instantaneous carrier frequency of the incoming waves.
  • the method of receiving carrier waves which are frequency modulated in accordance with signals which comprises selecting from the incoming waves a band of preassigned frequency extent, the limiting frequencies of which are constantly changing so as to maintain the central frequency of the band at substantially the instantaneous carrier frequency of the incoming waves, combining the selected waves with locally produced waves of substantially the instantaneous carrier frequency and in phase quadrature therewith and deriving from the combined waves correcting energy to control the limiting frequencies of the selected band and the phase quadrature agreement between the local oscillations and the instantaneous incoming carrier frequency waves.
  • a system for receiving carrier waves which are frequency modulated in accordance with nonperiodic modulating forces comprising a receiving circuit to which electromotive forces corresponding to the frequency modulated waves may be applied, a frequency selective network capable of transmitting a range of frequencies constituting only a small portion of the frequency range throughout which the frequency modulated carrier wave shifts during its frequency excursions, a wave detector connected to the output terminals of the network to receive from the receiving circuit waves of the limited range of frequencies passed by the selective network and means for causing the pass band of the network to vary in such manner as at all times to accept and transmit to the wave detector the incoming frequency modulated wave.
  • a system for receiving carrier waves which are frequency modulated in accordance with modulating forces comprising a receiving conductor upon which electromotive forces corresponding to the frequency modulated waves may be impressed, a detecting device and a selective network having input terminals connected to the conductor and output terminals connected to the detecting device, the selective network having a transmission band extending over a small fraction only of the range throughout which the frequency modulated wave varies during its frequency excursion and means responsive to waves yielded by the detecting device for varying the frequency position of the transmission band of the network to enable it at all times to accept waves of the instantaneous frequency of the frequency modulated carrier wave.
  • a system for receiving frequency modulated waves comprising an incoming conductor on which energy of the waves may be impressed, a selective pass network for passing a band of a frequency extent which is a small fraction only of the extent of the band through which the frequency modulated Wave ranges during the course of the frequency modulation, a network having input terminals connected to the incoming conductor and output terminals, a receiver for frequency modulated waves connected to the output terminals and means for automatically controlling the frequency position of the band passed to the receiver by the network without substantially varying its width whereby the network at all times accepts the incoming frequency modulated wave irrespective of the character of the modulation involved and of the manner in which the frequency of the incoming wave varies.

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  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
  • Noise Elimination (AREA)
US209183A 1938-05-21 1938-05-21 Transmission of frequency modulated waves Expired - Lifetime US2259000A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US209183A US2259000A (en) 1938-05-21 1938-05-21 Transmission of frequency modulated waves
GB12788/39A GB528152A (en) 1938-05-21 1939-04-28 Transmission of frequency modulated valves
FR854976D FR854976A (fr) 1938-05-21 1939-05-19 Systèmes de transmission d'ondes électriques
NL93492A NL61925C (enrdf_load_stackoverflow) 1938-05-21 1939-05-22
CH234266D CH234266A (fr) 1938-05-21 1939-05-22 Verfahren zum Empfangen einer mit Signalen frequenzmodulierten Trägerwelle und Einrichtung zur Ausübung des Verfahrens.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US209183A US2259000A (en) 1938-05-21 1938-05-21 Transmission of frequency modulated waves

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US2259000A true US2259000A (en) 1941-10-14

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US209183A Expired - Lifetime US2259000A (en) 1938-05-21 1938-05-21 Transmission of frequency modulated waves

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US (1) US2259000A (enrdf_load_stackoverflow)
CH (1) CH234266A (enrdf_load_stackoverflow)
FR (1) FR854976A (enrdf_load_stackoverflow)
GB (1) GB528152A (enrdf_load_stackoverflow)
NL (1) NL61925C (enrdf_load_stackoverflow)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2488584A (en) * 1943-12-08 1949-11-22 Rca Corp Locked-in oscillator circuits
US2494795A (en) * 1945-02-03 1950-01-17 Philco Corp Frequency-detector and frequency-control circuits
US2510906A (en) * 1945-03-24 1950-06-06 Avco Mfg Corp Frequency modulation receiver
US2541066A (en) * 1943-11-24 1951-02-13 Sperry Corp Object detecting and warning system and method
US2609494A (en) * 1950-01-24 1952-09-02 Padevco Inc Frequency modulation system for receiving one of two overlapping waves
US2983814A (en) * 1956-02-01 1961-05-09 Raytheon Co Signal receivers
US3119964A (en) * 1958-08-14 1964-01-28 Robertshaw Controls Co Phase shift keying communication system including automatic phase correction means

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2989622A (en) * 1958-12-29 1961-06-20 Bell Telephone Labor Inc Hybrid sideband frequency modulation system
DE1199337B (de) * 1959-02-04 1965-08-26 Peter G S Mero Phasendiskriminator
FR2938261B1 (fr) 2008-11-13 2010-11-19 Arkema France Fabrication de copolymeres ethylene/ester vinylique d'acide carboxylique a partir de matieres renouvelables, copolymeres obtenus et utilisations
FR2939139B1 (fr) 2008-12-03 2012-12-21 Arkema France Composition comprenant du polypropylene et/ou un copolymere du propylene obtenus a partir de matieres renouvelables et utilisations

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2541066A (en) * 1943-11-24 1951-02-13 Sperry Corp Object detecting and warning system and method
US2488584A (en) * 1943-12-08 1949-11-22 Rca Corp Locked-in oscillator circuits
US2494795A (en) * 1945-02-03 1950-01-17 Philco Corp Frequency-detector and frequency-control circuits
US2510906A (en) * 1945-03-24 1950-06-06 Avco Mfg Corp Frequency modulation receiver
US2609494A (en) * 1950-01-24 1952-09-02 Padevco Inc Frequency modulation system for receiving one of two overlapping waves
US2983814A (en) * 1956-02-01 1961-05-09 Raytheon Co Signal receivers
US3119964A (en) * 1958-08-14 1964-01-28 Robertshaw Controls Co Phase shift keying communication system including automatic phase correction means

Also Published As

Publication number Publication date
NL61925C (enrdf_load_stackoverflow) 1948-11-15
FR854976A (fr) 1940-04-29
GB528152A (en) 1940-10-23
CH234266A (fr) 1944-09-15

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