US2218524A - Frequency modulation system - Google Patents

Frequency modulation system Download PDF

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Publication number
US2218524A
US2218524A US319877A US31987740A US2218524A US 2218524 A US2218524 A US 2218524A US 319877 A US319877 A US 319877A US 31987740 A US31987740 A US 31987740A US 2218524 A US2218524 A US 2218524A
Authority
US
United States
Prior art keywords
frequency
circuit
waves
impedance
grid
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
US319877A
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English (en)
Inventor
Joseph G Chaffee
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.)
AT&T Corp
Original Assignee
Bell Telephone Laboratories Inc
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 US319877A priority Critical patent/US2218524A/en
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US326898A priority patent/US2250104A/en
Publication of US2218524A publication Critical patent/US2218524A/en
Application granted granted Critical
Priority to FR869048D priority patent/FR869048A/fr
Priority to FR878762D priority patent/FR878762A/fr
Priority to GB3689/41A priority patent/GB546677A/en
Priority to DEW719D priority patent/DE882424C/de
Priority to BE441132D priority patent/BE441132A/xx
Priority to NL115248A priority patent/NL67475C/xx
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • 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
    • H03C3/02—Details
    • H03C3/04—Means in or combined with modulating stage for reducing amplitude modulation
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C3/00—Angle modulation
    • H03C3/10—Angle modulation by means of variable impedance
    • H03C3/28—Angle modulation by means of variable impedance using variable impedance driven mechanically or acoustically

Definitions

  • the present invention relates to electricalwav e nected in the cathode-ground lead and by-passed control for signaling and kindredpurposes. More by a radio frequency condenser. For a fuller particularly it relates to thesuppression of un disclosure of typical embodiments the detailed p desired variations in the strength of the Waves, description to follow shouldfbe consulted. such as arise from undesired amplitude'modula- Referring. to the drawing, v tion, distortion or noise in the system.
  • Fig. 1 is a schematic circuit diagram of the In signaling "by means of frequency modulated invention as applied to the harmonic generator or phase modulated waves, undesired amplitude portion of a frequency modulated system; and
  • Fig. 1 shows the invention applied to a harmonic transmission is not constant as to frequency generator in a frequency modulated wave trans-v throughout the entire band of interest.
  • Harmonic generators have been variations produce noise,,besides which there suggested for use in frequency modulation sys- 0 may be noisefrom extraneous sources, tube noise, terns for the double purpose of increasing the etc, all of which may give rise to amplitude varig carrier frequency and increasing the modulation ations.
  • l I v index soas to preserve a constant percentage of It is a general object of this invention to supfrequency shift.
  • tank circuit 25 which is couat all large, this is likelyto result in singing" at pled to transmitting antenna 26.
  • the desired some frequency. l p harmonic frequency is selected by proper tun-
  • a simpliing of the tank circuit 25 A by-pass condenser fied arrangement with improvedjeffectiveness'is 29 is shown aroundthe plate source H which attained by deriving the detectedamplitude variin the case of a system using'considerable power ations in some circuitdevice in the system which would preferably consist of a power rectifier and 40 has detecting properties and using the detected filtering system as common in the art.
  • An audio frequency impedance 9, to be dev in the same device For example, harmonic gen-- scribed more fully presently, is connected in the erators or frequency changers are commonly cathode lead from the negative pole of source present in a frequency modulation transmitting H which is preferably grounded.
  • the grids are system and are used for shifting the frequencies connected to the ground terminal of impedance 45 to a different position in the frequency spectrum. 9.
  • a grid bias battery I0 is indicated and may Such devices are efficient detectors and modube desirable in some cases. if lators.
  • Thepresent invention comprises the use In the operation of the circuit o f-Fig.
  • the inventionv may amount of amplification together with an efiicomprise an audio frequency impedance concient degree of distortion for performing the 55 functionof harmonic generation.
  • the amplitude modulation assumed to be present in the frequency modulated waves is detected and appears as a low frequency detected component flowing in the anode circuit and therefore in series through the low frequency impedance 9.
  • This current develops a voltage across the terminals of the impedance 9 which is applied to the grid circuit in such phase as to oppose the variations of plate current of envelope frequency, resulting in a reduction of the amplitude modulation of the high frequency waves.
  • the action may be regarded as a negative feedback of the envelope frequencies present in the applied wave, resulting in a reduction of the amplitude modulation appearing in the output.
  • the action may also be looked upon as comprising a recovery of the audio frequency modulating component in the plate circuit and remodulation of the radio frequency wave in reverse sense by application of the recovered modulating component to the grid circuit of the frequency changer.
  • the form which the impedance 9 of Fig. 1 may take may vary widely in practice and illustrative examples are given in Figs. 1A, 1B, and 1C.
  • the impedance 9 is shown as comprising a resistance l3 and radio frequency by-pass capacity [4.
  • the resistance I3 serves both for the feedback of the detected modulating component and also for biasing the grid.
  • the grid receives an excessive negative bias an opposing battery may be used with its positive pole connected to the grid.
  • the manner in which the substitute network may be connected into the circuit of Fig. 1 is shown by the dotted rectangle and the three terminals passing through it marked respectively G, C and B.
  • a transformer consisting of windings l6 and I1 is used for the feedback of the detected modulating component, while avoiding the feedback of direct current voltage.
  • This circuit permits the use of a suitable voltage ratio in the transformer itself.
  • the secondary winding l! is shown terminated in resistance [8 provided with a slider to which the grid terminal is connected. Any high frequencies appearing on the grid side of this transformer which are not to be fed back may be shunted out by condenser l9.
  • each of the circuits shown in Figs. 1A, 1B and 10 contains sufficient elements to enable a certain amount of shaping or control of the amplitude frequency relations of the fed back waves.
  • other types of cathode networks will appear to those skilled in the art, and the forms that have been disclosed are to be construed as illustrative rather than limiting.
  • the one stage of harmonic generation disclosed there may be a plurality of stages in tandem for raising the frequency to the desired frequency level.
  • the cathode impedance for reducing amplitude modulation may be used in one or more of these tandem connected harmonic generators.
  • the amplitude modulations to be reduced may arise at any point in the system including the tubes in the frequency shifting circuits by which the compensating operation is carried out.
  • such undesired moduation may arise from tube noise, power fluctuations or other local sources, or elsewhere.
  • a source of frequency modulated waves comprising a space discharge device having a grid, a cathode and an anode, means to impress waves from said source on said grid and cathode, an outgoing circuit connected to Said anode and cathode containing filter means for selectively passing waves of desired harmonic frequencies, and an impedance connected on one side to said cathode and on its other side to said grid and anode, said impedance providing an audio frequency negative feedback path from the output to the input of said device to oppose transmission into the outgoing circuit of amplitude variations of audio envelope frequency in said waves.
  • a source of frequency modulated high frequency waves a utilization circuit for waves whose frequencies are harmonics of the frequencies of the waves from said source, and a spacedischarge amplifying device having an input circuit and an output circuit, and having a non-linear characteristic, connected between said source and said utilization circuit, for stepping up the frequencies to the level of said harmonics, and means for opposing audio frequency amplitude variations in the waves of stepped-up frequency comprising an audio frequency negative feedback impedance common to the input and output circuits of said device.

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  • Amplitude Modulation (AREA)
  • Transmitters (AREA)
  • Particle Accelerators (AREA)
US319877A 1940-02-20 1940-02-20 Frequency modulation system Expired - Lifetime US2218524A (en)

Priority Applications (8)

Application Number Priority Date Filing Date Title
US319877A US2218524A (en) 1940-02-20 1940-02-20 Frequency modulation system
US326898A US2250104A (en) 1940-02-20 1940-03-30 Frequency regulation
FR869048D FR869048A (fr) 1940-02-20 1941-01-02 Systèmes de transmission à modulation de fréquence
FR878762D FR878762A (fr) 1940-02-20 1941-01-24 Procédé de régulation de fréquence
GB3689/41A GB546677A (en) 1940-02-20 1941-03-18 Improvements in or relating to systems for maintaining a constant mean frequency in transmissions by frequency modulated carrier wave
DEW719D DE882424C (de) 1940-02-20 1941-03-27 Anordnung zur Konstanthaltung der mittleren Frequenz eines Oszillators fuer frequenzmodulierte Traegerwellen
BE441132D BE441132A (en)) 1940-02-20 1941-04-10
NL115248A NL67475C (en)) 1940-02-20 1944-02-11

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US319877A US2218524A (en) 1940-02-20 1940-02-20 Frequency modulation system
US326898A US2250104A (en) 1940-02-20 1940-03-30 Frequency regulation

Publications (1)

Publication Number Publication Date
US2218524A true US2218524A (en) 1940-10-22

Family

ID=26982185

Family Applications (2)

Application Number Title Priority Date Filing Date
US319877A Expired - Lifetime US2218524A (en) 1940-02-20 1940-02-20 Frequency modulation system
US326898A Expired - Lifetime US2250104A (en) 1940-02-20 1940-03-30 Frequency regulation

Family Applications After (1)

Application Number Title Priority Date Filing Date
US326898A Expired - Lifetime US2250104A (en) 1940-02-20 1940-03-30 Frequency regulation

Country Status (6)

Country Link
US (2) US2218524A (en))
BE (1) BE441132A (en))
DE (1) DE882424C (en))
FR (2) FR869048A (en))
GB (1) GB546677A (en))
NL (1) NL67475C (en))

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2490448A (en) * 1945-11-09 1949-12-06 Amalgamated Wireless Australas Frequency changer
US2609509A (en) * 1945-06-13 1952-09-02 Bertram C Hill Electrical testing apparatus
US3202918A (en) * 1962-10-03 1965-08-24 Armand P Lucchesi Frequency multiplier

Families Citing this family (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2425657A (en) * 1941-04-17 1947-08-12 Rca Corp Short-wave apparatus
US2440600A (en) * 1941-05-14 1948-04-27 Rca Corp Electric motor control
US2475779A (en) * 1941-05-14 1949-07-12 Rca Corp Wave length modulator and control means
US2966676A (en) * 1942-06-30 1960-12-27 Bessie E Fox Electronic apparatus and method for measuring distance
US2794956A (en) * 1942-06-30 1957-06-04 Fox Benjamin Frequency modulation system
US2422422A (en) * 1942-08-31 1947-06-17 Rca Corp Reactance tube controlled generator
US2415868A (en) * 1942-10-28 1947-02-18 Rca Corp Timing modulation
US2434259A (en) * 1943-06-22 1948-01-13 Bell Telephone Labor Inc Circuit arrangement utilizing a plurality of electron discharge devices
US2511137A (en) * 1944-12-16 1950-06-13 Rca Corp Frequency control
US2588730A (en) * 1947-05-02 1952-03-11 Wayne R Johnson Method and apparatus for frequency response measurement
US2615129A (en) * 1947-05-16 1952-10-21 Edwin M Mcmillan Synchro-cyclotron
US2659813A (en) * 1950-02-11 1953-11-17 Bell Telephone Labor Inc Frequency modulation repeater
US2688730A (en) * 1950-10-18 1954-09-07 Smith Meeker Engineering Co Stable frequency generator system
US2761065A (en) * 1953-05-27 1956-08-28 Harris A Robinson Frequency control system
US3789302A (en) * 1972-03-31 1974-01-29 Microwave Ass Inc Fm heterodyne transmitter
US10424278B2 (en) * 2017-08-02 2019-09-24 Applied Invention, Llc Bell with subharmonic difference tone

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE399079A (en)) * 1931-09-17
NL57985C (en)) * 1937-07-09

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2609509A (en) * 1945-06-13 1952-09-02 Bertram C Hill Electrical testing apparatus
US2490448A (en) * 1945-11-09 1949-12-06 Amalgamated Wireless Australas Frequency changer
US3202918A (en) * 1962-10-03 1965-08-24 Armand P Lucchesi Frequency multiplier

Also Published As

Publication number Publication date
DE882424C (de) 1953-07-09
FR878762A (fr) 1943-01-29
BE441132A (en)) 1941-10-31
FR869048A (fr) 1942-01-22
NL67475C (en)) 1951-03-15
GB546677A (en) 1942-07-24
US2250104A (en) 1941-07-22

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