US2294209A - Frequency modulation system - Google Patents

Frequency modulation system Download PDF

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US2294209A
US2294209A US240145A US24014538A US2294209A US 2294209 A US2294209 A US 2294209A US 240145 A US240145 A US 240145A US 24014538 A US24014538 A US 24014538A US 2294209 A US2294209 A US 2294209A
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frequency
signal
currents
current
sin
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Roder Hans
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General Electric Co
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General Electric Co
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Priority to GB29795/39A priority patent/GB534757A/en
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    • HELECTRICITY
    • H03ELECTRONIC CIRCUITRY
    • H03CMODULATION
    • H03C3/00Angle modulation
    • H03C3/34Angle modulation by deflection of electron beam in discharge tube

Definitions

  • My invention relates to signaling systems, and more particularly to such systems employing socalled, phase, or frequency modulation, of a carrier wave, that is, modulation of the frequency of the carrier wave in accordance with a signal. It has for one of its objects to provide a new and improved method and means for producing a carrier wave having its frequency accordance with the signal.
  • a further object of my invention is to produce a frequency modulated carrier wave without use of the usual frequency modulating means, i. e., without varying the frequency of any source in accordance with the signal.
  • n object ofthe invention is to eil'ect frequency modulations by the use of equipment such' as is commonly used in amplitude modulation systems.
  • Aphase or frequency modulated wave is mathematically represented 'by the following expresmodulated in v may be represented by the expression sin at and the oscillations supplied to modulator 4 may be represented by the expression cos wt.
  • Conductors A and IB,-which comprise the signal input circuit of modulator 3 are supplied with currents which may be represented by the ex-- pression cos (m sin at), and similarly the conductors C and D which comprise the input to.
  • the modulator I is supplied with currents which may be represented by the expression sin (m sin at).
  • the remainder of the apparatus of Fig. 1 comprises means for generating the two currents which are supplied to the modulators over con ductors A, B; and C, D.
  • the apparatus of Fig. 1 comprises a cathode ray tube It and for frequency 4, each of which may be of any well-known design for effecting amplitude modulation of a carrier wave.
  • the direction of the beam is controlled by four deflecting plates comprising a pair or horizontal plates It and Il between which oscillations of very high frequency such as, for example, five megacycles or other suitable frequency much higher than the signal frequency are supplied from a source It. These plates serve to deflect the beam upwardly and downwardly so as to cause it, in the absence of signal currents, to produce a luminescent line upon the fluorescent screen of the cathode ray device.
  • the beam is also deflected horizontally by means of a pair of electrodes l8 and ll between which the signal oscillations are supplied.
  • the source or signal oscillations is represented as a microphone It the output of which is supplied through an amplifier I 9 and a network comprising a series resistance 23 and shunt condenser 2
  • the luminescent vertical line produced by the source I oi thecathode ray oscillograph is caused to deflect bodily horizontally across the screen in accordance with the signal currents.
  • Light from the upper portion of the cathode ray screen l2 issuitably focused by means of a lens 22 upon a photoelectric cell 23 the output or which is amplified and supplied between the conductors A and B.
  • Light from the lower portion of the cathode my screen is focused by means of a lens 25 upon a photoelectric cell 26 the output of which is amplified by amplifier 21 and supplied between conductors C and D.
  • a suitable screen 28 is provided which extends between the lenses 22 and 25 and to a point closely adjacent the middle of the cathode ray screen.
  • Fig. 2 the middle portion of the screen is indicated by the line 28, which may be taken to represent the shield 23 of Fig. 1.
  • the portionof the screen above line 28 affects photoelectric cell 23 and that below line 23 affects photoelectric cell 26.
  • the shaded area of both portions, or sections, as shown in Fig. 2 is covered with opaque material so that light from the fluorescent screen within the tube is not visible exteriorly thereof and only light from that portion of the fluorescent screen not covered, by the opaque material afi'ects the photoelectric cells.
  • the vertical line 29 represents the luminescent line which is produced by the cathode ray beam when no signal currents are applied to the horizontal deflecting plates. When signal currents are applied, this line 29 moves bodily to the right and to the left, parallel with itself, in accordance with the variations of the signal ductors 36 and 31 respectively spaced at regularcurrents.
  • each of the shaded areas are bounded by sinusoidal lines 30 and 3
  • the current radiated from the antenna is a ,frequency modulated current, the modulationbeing in accordance with the current in microphone l8.
  • the entire screen may be covered with material having a varying degree of translucence, the variations being in accordance with the sine and cosine function.
  • Such a coating for the end of the cathode ray tube is indicated in Fig. 2 in which the shaded areas 33 represent portions of minimum visibility of the screen and the unshaded portions represent the portions of greater visibility of the screen, the translucence of the ma- .grids as represented at 34- and 35 in Fig. 4 may be positioned across the end of the cathode ray device.
  • These grids may comprise parallel conintervals across the end of the cathode ray tube, the conductors 36 of one grid 34 being displaced from the conductors 31 of the other grid 35 by a quarter of the distance between the conductors.
  • conductors 36 are connected together and to conductor 38 leading to the signal amplifier 40.
  • conductors 31 are connected together and to conductor 39 leading to signal amplifier 4
  • the vertical line transcribed by the cathode ray beam in the absence of signal currents, thus cuts across the two' grids at a predetermined point indicated by the vertical line 42, and when deflected longitudinally of the two grids by signal currents causes varying charges to be impressed upon the'conductors 38 and 33. That is, the charge on either conductor is a maximum when the beam falls directly upon one of the conductors 36 or 31. This charge then gradually diminishes to a minimum when the beam -falls midway between such conductors. lItthen increases as the beam approaches the next conductor. 39 varies sinusoidally. Due to the relative displacement of the conductors 31 relative to conductors 36 along the lengths of the grids, the
  • two sources of carrier wave aaeaaoe current means to translate variations of said signal current into two light variations, eachvarying as sinusoidal functions of said signal oscillations of the sam frequency one of said sources being displaced in phase from the other by substantially ninety degrees, a source of signal current, means for modulating the oscillations of each of said carrier wave sources in ac-' cordance with a sinusoidal function of said signal current, the .modulation of one of said carrier wave sources being displaced in phase by ninety degrees from that of the other, and additively combining the outputs from, said modulating means.
  • two sources of carrier wave oscillations of the same frequency displaced in phase by ninety degrees a source of signal oscillations, means for producing a current varying as a cosine function of said signal oscillations and another current varyingas a sine function of said signal oscillations, means for modulating that one of said carrier wave oscillations having the leading phase with that one of the signal oscillations having the lagging phase, and means for modulating the other source of carrier wave oscillations with the remaining source of signal oscillations, and means for combining. the outputs from said modulating means.
  • the method of producing a carrier wave having'its frequency modulated in accordance with a signal current which comprises amplitude modulating two carrier waves of the same frequency and displaced in phase by ninety degrees by currents varying as sinusoidal functions of said signal current, the phase of the current with which the carrier wave of leading phaseis modulated lagging the phase of the current with which the carrier wave of lagging phase is modulated, and combining said two amplitude modulated carrier waves to produce the frequency modulated carrier wave.
  • a pair of amplitude modulators a carrier wave source connected to the inputs of said modulators, means to displace the phase of oscillations supplied from said source to one of said modulators by ninety degrees with respect to the phase of the oscillations supplied to the other modulator, a source of signal current, means to supply current to each of said modulators varying in accordance with a 'sinusoidal function of said signal currents, the
  • a cathode ray tube having a fluorescent screen, means for producing a luminescent line across saidscreen, means to deflect said line along'said screen in accordance light variations, and means to combine said "care I with signal current, said screen having'two sec- 1 tions, means to render the luminescence of said screen visible exteriorly of said cathode ray tube in amounts varying, sinusoidally from prede- 'termined points simultaneously traversed by said sections of said screen exteriorly of said tube, two
  • each grid having a plurality of conductorsv connected together and extending parallel with said line, said conductors being spaced apart at regular intervals in a direction transverse of said beam, means to deflect said beam along said grids in accordance with signal currents; the various conductors of each,
  • the method of producing a carrier current having its frequency modulated inaccord with a signal current which comprises producing two carrier currents of the same frequency displaced in phase, modulating the amplitude of each carrier current in accord with a periodic function of the signal current, the modulations of the two carrier currents having the same phase displacement one fromthe other as the two carrier currents, and combining the resulting carrier currents.
  • the method of producing a high frequency carrier current having its frequency modulated in accord with the variations of a lower frequency signal current which comprises producing two high frequency carrier currents .of the same high frequency displaced inphase ninety degrees, modulating the amplitude of each of these high frequency carrier currents in accord with periodic functions of said lower-frequency signal current, said modulations of the two carrier currents having a ninety degree phase displacement one from the other, and combining the resulting two carrier currents into a single carrier current whereby a carrier wave is produced having its frequency modulated in accord with said signal current.
  • the method of modulation which includes the steps of generating a constant frequency carrier wave, producing signalling voltage of arbitrary wave form, utilizing said signalling voltage to generate an auxiliary wave which is a simple. sinusoidal function of the instantaneous value of said signalling voltage, and modulating said.
  • Means for producing polyphase alternating currents having an instantaneous frequency determined by the rate of change of a signal volt age comprising, an energy carrying beam, means for deflecting said beam by an amount determined solely by the'instantaneous potential of said signal, a succession of targets'in the path of

Description

Aug. 25, 1942.
H. RODER 2,294,209
FREQUENCY MODULATION SYSTEM Filed Nov. 12, 1938 am wt cos(m 6mm) s p wt cosfmsm Ut)+ cos sm wt .3 w sm(m sm Lit). Fig. I.
F|L"l'E R 9 I I AMPLITUDE 4 3 HODULATORS l PHASE smFT T NETWORKH cos(m sm Ht). A
cos gut cos wi'sm (m sm at) Fig.4. 7
1.. llMlllfllllMllllln.
Inventor: Hans Roder His Attovney.
Patented Aug. 25, 1942 UNI ED STATES PATENT =-omce FRE UENCY nzfirxzrrou surfsrap i Schenectady, N. 1., assignor a Gen eral Electric Company, a corporation of New York - Application November 12, 1938, Serial a... 240,145
My invention relates to signaling systems, and more particularly to such systems employing socalled, phase, or frequency modulation, of a carrier wave, that is, modulation of the frequency of the carrier wave in accordance with a signal. It has for one of its objects to provide a new and improved method and means for producing a carrier wave having its frequency accordance with the signal.
A further object of my invention is to produce a frequency modulated carrier wave without use of the usual frequency modulating means, i. e., without varying the frequency of any source in accordance with the signal. n object ofthe invention is to eil'ect frequency modulations by the use of equipment such' as is commonly used in amplitude modulation systems.
The novel features which I believe to be char acteristic of my invention are set forth with par-e ticularity in the appended claims. My invention itself, however, both as to its organization and method of operation together with further objects and advantages thereof may best be understood by reference' to the following description taken in connection with the accompanying drawing in which Fig. 1 represents an embodiment of my invention; Figs. 2 and 3 represent details thereof, and Fig. 4 represents a modification.
. Aphase or frequency modulated wave is mathematically represented 'by the following expresmodulated in v may be represented by the expression sin at and the oscillations supplied to modulator 4 may be represented by the expression cos wt.
Conductors A and IB,-which comprise the signal input circuit of modulator 3 are supplied with currents which may be represented by the ex-- pression cos (m sin at), and similarly the conductors C and D which comprise the input to. the modulator I is supplied with currents which may be represented by the expression sin (m sin at).
These latter currents are of the signal frequency a and modulate the currents of the carrier wave frequency supplied tothe respective modulators 3 and {to produce, in the output of the modulator 3, a current which may be expressed sin wt cos (m sin t) and at the output of modulator 4, a
current which may be expressed by cos wt sin rier frequency and the output of which is supsion. sin (wt+m sin t). This expression, by
trigonometric methods. may readily be shown to be equal to the following: sin (at cos (m sin ,ut)
cos mt sin I (m sin t). In these expressions w=2wf where I is the frequency or the carrier wave: 1
t=time l a he signal frequency; and m is a constant for phase modulation, modulation m=Aw/p where A40 is the maximum shift of the carrier frequency produced by th signal- Reierring to Fig. 1 I have indicated at l a source of carrier wave oscillations the output of which is supplied to two amplitude modulators 3 and plied through a power amplifier 8 and radiated from an antenna 8. The current in the antenna called a frequency modulated wave.
The remainder of the apparatus of Fig. 1 comprises means for generating the two currents which are supplied to the modulators over con ductors A, B; and C, D. This means, the apparatus of Fig. 1, comprises a cathode ray tube It and for frequency 4, each of which may be of any well-known design for effecting amplitude modulation of a carrier wave. The oscillations supplied toamplitude oscillation supplied to modulator 3 from source I having therein the usual cathode" II and means whereby a beam 01 electronsis produced and directed upon avspot on a fluorescent screen at the end I! of the cathode my device. The direction of the beam is controlled by four deflecting plates comprising a pair or horizontal plates It and Il between which oscillations of very high frequency such as, for example, five megacycles or other suitable frequency much higher than the signal frequency are supplied from a source It. These plates serve to deflect the beam upwardly and downwardly so as to cause it, in the absence of signal currents, to produce a luminescent line upon the fluorescent screen of the cathode ray device. The beam is also deflected horizontally by means of a pair of electrodes l8 and ll between which the signal oscillations are supplied. The source or signal oscillations is represented as a microphone It the output of which is supplied through an amplifier I 9 and a network comprising a series resistance 23 and shunt condenser 2|. In this way the luminescent vertical line produced by the source I oi thecathode ray oscillograph is caused to deflect bodily horizontally across the screen in accordance with the signal currents. Light from the upper portion of the cathode ray screen l2 issuitably focused by means of a lens 22 upon a photoelectric cell 23 the output or which is amplified and supplied between the conductors A and B. Light from the lower portion of the cathode my screen is focused by means of a lens 25 upon a photoelectric cell 26 the output of which is amplified by amplifier 21 and supplied between conductors C and D.
In order that light from the upper portion of the cathode ray screen may not afiect the photoelectric cell 26, and similarly, in order that light from the lower portion of the screen may not affect photoelectric cell 23 a suitable screen 28 is provided which extends between the lenses 22 and 25 and to a point closely adjacent the middle of the cathode ray screen. v
0n the end of the cathode ray tube either exteriorly or'interiorly thereof, but between the fluorescent material and the focusing lens is a suitable coating of opaque material having a design suchas is indicated in Fig. 2 in which the middle portion of the screen is indicated by the line 28, which may be taken to represent the shield 23 of Fig. 1. The portionof the screen above line 28 affects photoelectric cell 23 and that below line 23 affects photoelectric cell 26. The shaded area of both portions, or sections, as shown in Fig. 2, is covered with opaque material so that light from the fluorescent screen within the tube is not visible exteriorly thereof and only light from that portion of the fluorescent screen not covered, by the opaque material afi'ects the photoelectric cells.
The vertical line 29 represents the luminescent line which is produced by the cathode ray beam when no signal currents are applied to the horizontal deflecting plates. When signal currents are applied, this line 29 moves bodily to the right and to the left, parallel with itself, in accordance with the variations of the signal ductors 36 and 31 respectively spaced at regularcurrents. Since the upper portion of each of the shaded areas are bounded by sinusoidal lines 30 and 3| respectively which are displaced with respect to each other, and with respect to the midposition of line 29, by 90 degrees, it will be seen that the light which afi'ects the photoelectric cell 23 varies as a cosine function of the signal currents and similarly light from the lower sectlon of the screen which affects photoelectric cell 26 varies'as a sine function of the signal current. Accordingly,- currents representing this cosine function of the signal currents appear upon conductors A and B at the output of amplifier 23 and similarly currents representing the sine function of the signal currents appear on conductors C and D at the output of amplifier For frequency modulation, as previously stated, 1n. must represent Aer/1L, that is, the ratio of the shift in the carrier frequency to the signal frequency. To effect this it is merely necessary to include the network 20-2! in the output of the Signal amplifier l9, this network being so proportioned that the voltage betweenplates I6 and. I1 varies. inversely with the frequency. Thusthe current radiated from the antenna is a ,frequency modulated current, the modulationbeing in accordance with the current in microphone l8.
By the terms phase modulation" and frequency modulation as usedherein, I do not intend to infer that modulation of the frequency of the carrier wave is not involved in both of these forms of modulation. In fact, were the sig- -modulation. Were the signal current of complex form the frequency of the carrier wave is still modulated in both forms of modulation. Phase modulation is merely that form of frequency modulation in which the amplitude of the frequency shift of the carrier is directly proportional to the modulation frequency as indicated by the above mathematical relationship m=A(0/I-h Of course, instead of covering a portion of the screen with opaque material and leaving the rest completely visible the entire screen may be covered with material having a varying degree of translucence, the variations being in accordance with the sine and cosine function. Such a coating for the end of the cathode ray tube is indicated in Fig. 2 in which the shaded areas 33 represent portions of minimum visibility of the screen and the unshaded portions represent the portions of greater visibility of the screen, the translucence of the ma- .grids as represented at 34- and 35 in Fig. 4 may be positioned across the end of the cathode ray device. These grids may comprise parallel conintervals across the end of the cathode ray tube, the conductors 36 of one grid 34 being displaced from the conductors 31 of the other grid 35 by a quarter of the distance between the conductors.
The conductors 36 are connected together and to conductor 38 leading to the signal amplifier 40. Similarly conductors 31 are connected together and to conductor 39 leading to signal amplifier 4|.
The vertical line transcribed by the cathode ray beam, in the absence of signal currents, thus cuts across the two' grids at a predetermined point indicated by the vertical line 42, and when deflected longitudinally of the two grids by signal currents causes varying charges to be impressed upon the'conductors 38 and 33. That is, the charge on either conductor is a maximum when the beam falls directly upon one of the conductors 36 or 31. This charge then gradually diminishes to a minimum when the beam -falls midway between such conductors. lItthen increases as the beam approaches the next conductor. 39 varies sinusoidally. Due to the relative displacement of the conductors 31 relative to conductors 36 along the lengths of the grids, the
Thus the charge on conductors 38 and While I have-s o n u ia two' ways of producing the two-currentscosflt andysin (m :sin t), it will .be that any means capable of. producing 'suclifllcurrents .withthe sinusoidal variations therein, displaced in phase by 90 degreesm ay be employ vices may be devised.
Y Thus, while I have shown 'only particular embodlments of my invention it of course, "be understood that I do not wish to be limited there- .if'Many such de- .to since many'modifications' may be madenand I contemplate by the appended claims to-cover any such modifications as fall within the true spirit and scope of my invention. Y Y
What I claim as new andidesire to secureby Letters Patent of the United States, is: V
1. In combination, two sources of carrier wave aaeaaoe current, means to translate variations of said signal current into two light variations, eachvarying as sinusoidal functions of said signal oscillations of the sam frequency one of said sources being displaced in phase from the other by substantially ninety degrees, a source of signal current, means for modulating the oscillations of each of said carrier wave sources in ac-' cordance with a sinusoidal function of said signal current, the .modulation of one of said carrier wave sources being displaced in phase by ninety degrees from that of the other, and additively combining the outputs from, said modulating means.
2. In combination, two sources of carrier wave oscillations of the same frequency displaced in phase by ninety degrees, a source of signal oscillations, means for producing a current varying as a cosine function of said signal oscillations and another current varyingas a sine function of said signal oscillations, means for modulating that one of said carrier wave oscillations having the leading phase with that one of the signal oscillations having the lagging phase, and means for modulating the other source of carrier wave oscillations with the remaining source of signal oscillations, and means for combining. the outputs from said modulating means.
3. The method of producing a carrier wave having'its frequency modulated in accordance with a signal current which comprises amplitude modulating two carrier waves of the same frequency and displaced in phase by ninety degrees by currents varying as sinusoidal functions of said signal current, the phase of the current with which the carrier wave of leading phaseis modulated lagging the phase of the current with which the carrier wave of lagging phase is modulated, and combining said two amplitude modulated carrier waves to produce the frequency modulated carrier wave.
4. In combination, a pair of amplitude modulators, a carrier wave source connected to the inputs of said modulators, means to displace the phase of oscillations supplied from said source to one of said modulators by ninety degrees with respect to the phase of the oscillations supplied to the other modulator, a source of signal current, means to supply current to each of said modulators varying in accordance with a 'sinusoidal function of said signal currents, the
current, said variations being displaced in phase by substantially ninety degrees, means for modulating the'leading one'of said carrier waves in accordance with the lagging one of saidv light variations and for modulating the remaining carrier wave in accordance with the other of said rier wave aftermodulation.
7. In combination, a cathode ray tube having a fluorescent screen, means for producing a luminescent line across saidscreen, means to deflect said line along'said screen in accordance light variations, and means to combine said "care I with signal current, said screen having'two sec- 1 tions, means to render the luminescence of said screen visible exteriorly of said cathode ray tube in amounts varying, sinusoidally from prede- 'termined points simultaneously traversed by said sections of said screen exteriorly of said tube, two
.sources of carrier wave of the same frequency,
to deflect the electron beam of said tube in a straight line, a pair of grids, each grid havinga plurality of conductorsv connected together and extending parallel with said line, said conductors being spaced apart at regular intervals in a direction transverse of said beam, means to deflect said beam along said grids in accordance with signal currents; the various conductors of each,
grid being displaced from the conductors of the other grid by one-quarter of the distance between conductors, a pair of sources of carrier wave of the same frequency displaced in phase by ninety degrees, means to modulate one of said carrier] wave sources in accordance with the electromotive force induced in one of said grids and to modulate the other of said sources in accordance with the electromotive force induced in the other grid, and means to combine the output from said a carrier wave sources.
sinusoidal variations in said currents supplied to means to produce two currents, one varying as a 9. The method of modulating the frequency of a carrier wave in accordance with a current represented by the expression m sin pt, which comprises producingtwo currents represented by the expressions sin wtand cos wt, producing two additional currents represented by the expressions cos (m sin t) and sin (m sin pt), amplitude modulating the current sin at with the current cost (m sin t), amplitude modulating the current cos at with thecurrent sin (m sin at) and combining the modulated currents so produced, where t=time Y =the signal frequency f 'w=21r,f where is the frequency of the carrier wave m=a constant 10. The method of modulating the frequency of a carrier wave in accordancewith a current having a frequency II- which comprises producing two'currents represented by the expressions sin t andcos wt, producing two additional currents I represented by the expressions cos (m sin at) and sin (m sin t), amplitude modulating the current sin wt with the currentcos (msin at) amplitude modulating the current cos ibt with the current sin (m sin t) and combining the modulated currents so produced, where I .t=time w=21rf where f is the frequency of the carrier wave m=-Aw/ where Aw is the maximum shift of the carrier frequency produced by the signal.
such that the-modulated waves when combined produce the desired frequency modulated wave.
12. The method of producing a carrier current having its frequency modulated inaccord with a signal current which comprises producing two carrier currents of the same frequency displaced in phase, modulating the amplitude of each carrier current in accord with a periodic function of the signal current, the modulations of the two carrier currents having the same phase displacement one fromthe other as the two carrier currents, and combining the resulting carrier currents.
13. The method of producing a high frequency carrier current having its frequency modulated in accord with the variations of a lower frequency signal current which comprises producing two high frequency carrier currents .of the same high frequency displaced inphase ninety degrees, modulating the amplitude of each of these high frequency carrier currents in accord with periodic functions of said lower-frequency signal current, said modulations of the two carrier currents having a ninety degree phase displacement one from the other, and combining the resulting two carrier currents into a single carrier current whereby a carrier wave is produced having its frequency modulated in accord with said signal current.
14. The method of modulation which includes the steps of generating a constant frequency carrier wave, producing signalling voltage of arbitrary wave form, utilizing said signalling voltage to generate an auxiliary wave which is a simple. sinusoidal function of the instantaneous value of said signalling voltage, and modulating said.
carrier wave in accordance with said auxiliary wave. I
15. Means for producing polyphase alternating currents having an instantaneous frequency determined by the rate of change of a signal volt age comprising, an energy carrying beam, means for deflecting said beam by an amount determined solely by the'instantaneous potential of said signal, a succession of targets'in the path of
US240145A 1938-11-12 1938-11-12 Frequency modulation system Expired - Lifetime US2294209A (en)

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GB29795/39A GB534757A (en) 1938-11-12 1939-11-10 Improvements in frequency and space modulation systems for carrier-wave signalling
DEL99450D DE758889C (en) 1938-11-12 1939-11-14 Method and arrangement for frequency or phase modulation

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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2431569A (en) * 1942-10-14 1947-11-25 Hartford Nat Bank & Trust Co Frequency modulation
US2476349A (en) * 1944-09-04 1949-07-19 Hartford Nat Bank & Trust Comp Phase or frequency modulation system
US2494992A (en) * 1943-04-02 1950-01-17 Westinghouse Electric Corp Cathode-ray tube
US2525475A (en) * 1948-07-22 1950-10-10 Westinghouse Electric Corp Radio apparatus
US2545955A (en) * 1947-02-17 1951-03-20 Amalgamated Wireless Australas Modulation
US2569358A (en) * 1947-04-29 1951-09-25 Hartford Nat Bank & Trust Co Apparatus for phase modulating high-frequency oscillations
US2569911A (en) * 1944-12-18 1951-10-02 Electronbeam Ltd Signal storing device and proportional-control circuits therefor
US2612634A (en) * 1944-10-19 1952-09-30 Rca Corp Angular modulation
US2705258A (en) * 1951-08-08 1955-03-29 Lesti Arnold Color television camera
US2781169A (en) * 1951-03-16 1957-02-12 Northrop Aircraft Inc Vector adder
US2938075A (en) * 1954-05-18 1960-05-24 Emi Ltd Wired electrical signal distributing systems
US5255269A (en) * 1992-03-30 1993-10-19 Spacecom Systems, Inc. Transmission of data by frequency modulation using gray code

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2135844B (en) * 1983-02-21 1986-08-28 Nippon Telegraph & Telephone Oscillator with variable frequency and phase

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1744044A (en) * 1926-09-20 1930-01-21 American Telephone & Telegraph Single-side-band carrier system
DE616269C (en) * 1932-03-31 1935-07-27 Siemens & Halske Akt Ges Process for producing a phase shift of preferably 90 °

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2431569A (en) * 1942-10-14 1947-11-25 Hartford Nat Bank & Trust Co Frequency modulation
US2494992A (en) * 1943-04-02 1950-01-17 Westinghouse Electric Corp Cathode-ray tube
US2476349A (en) * 1944-09-04 1949-07-19 Hartford Nat Bank & Trust Comp Phase or frequency modulation system
US2612634A (en) * 1944-10-19 1952-09-30 Rca Corp Angular modulation
US2569911A (en) * 1944-12-18 1951-10-02 Electronbeam Ltd Signal storing device and proportional-control circuits therefor
US2545955A (en) * 1947-02-17 1951-03-20 Amalgamated Wireless Australas Modulation
US2569358A (en) * 1947-04-29 1951-09-25 Hartford Nat Bank & Trust Co Apparatus for phase modulating high-frequency oscillations
US2525475A (en) * 1948-07-22 1950-10-10 Westinghouse Electric Corp Radio apparatus
US2781169A (en) * 1951-03-16 1957-02-12 Northrop Aircraft Inc Vector adder
US2705258A (en) * 1951-08-08 1955-03-29 Lesti Arnold Color television camera
US2938075A (en) * 1954-05-18 1960-05-24 Emi Ltd Wired electrical signal distributing systems
US5255269A (en) * 1992-03-30 1993-10-19 Spacecom Systems, Inc. Transmission of data by frequency modulation using gray code

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DE758889C (en) 1954-06-21
GB534757A (en) 1941-03-17

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