US2455959A - Device for the transmission of signals by means of frequency-modulated carrier waves - Google Patents

Device for the transmission of signals by means of frequency-modulated carrier waves Download PDF

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Publication number
US2455959A
US2455959A US480362A US48036243A US2455959A US 2455959 A US2455959 A US 2455959A US 480362 A US480362 A US 480362A US 48036243 A US48036243 A US 48036243A US 2455959 A US2455959 A US 2455959A
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Prior art keywords
frequency
sec
cycles
oscillations
transmitted
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Expired - Lifetime
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US480362A
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English (en)
Inventor
Mark Jan Van Der
Weyers Theodorus Josephus
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Hartford National Bank and Trust Co
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Hartford National Bank and Trust Co
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B14/00—Transmission systems not characterised by the medium used for transmission
    • H04B14/002—Transmission systems not characterised by the medium used for transmission characterised by the use of a carrier modulation
    • H04B14/006—Angle modulation

Definitions

  • 'Ihis-invention relates to a device for the transmission of signals by means of a frequency-modue lat-ed carrier wave. It is known respects the use of tions may have great modulated oscillations,
  • the invention has for its object'to-add to these advantages another advantage viz; a considerable decrease of the distortions which may arise when the emitted signal reaches the 'receiVer'al'ong dl-fferentpaths; V
  • the invention is based 'onthe recognition that upon reception of frequency-modulated oscillations reaching the receiver along two paths with a difference in transit time T the, distortion occurring after detection depends on the frequency and is approximately inversely propo'rtional to thefrequency of the modulating oscilla-' tions.
  • a device 'for the'transmission offrequency-modulated to the invention arrangedso that at 'leastapart of" the frequency spectrum insuch manner that the frequency spectrum of oscillations is, according v i of the signals to be" transmitted is heterodyned before the modulator the oscillations modulating the carrier wave to be I transmitted solely comprises frequencies above a definite frequency whichexceeds thelowest fre-' quency of the signal frequencies to betransmitted.
  • The" frequency spectrum of the signals to be transmitted is preferably shifted towards the higher frequencies by an amount corresponding at least substantially tothe r-nini'murnfrequency which may still appearin the oscillatidnsmodulating the carrier wave and which preferably amounts-to about 1 000 cycles/sec; v
  • The-choice of-the minimum frequency is deter m ned on the one hand by the admissible-distortion which occurs after detection due totransmission along two different paths, but on the other hand the minimum'frequency should not be chosen too high, since otherwise there occur toohigh modulation frequencies"and, as is wellknown, theratio between signal and the dis turbances caused'in a receiving set byother transmitters; by noise" or by atmospheri'cs' becomes worse as the ratio between the'frequencydevia tion and the highest modulation frequency de creases f
  • the invention willbemore fully explained-by reference to: the accompanying "drawing: 'given one form of e construction of a transmittingdevi'ce by way of example; in whichle 'represents Vcarrie'r wave to be :rang em'ent for the-reception of frequency mod e cycles/sec, transmitted by 'the filt er' *F'z.
  • the modulator M1 the carrier wave of 10,500 cycles/sec.
  • the two side bands are supplied to a filter F3, which transmits only one of the side bands and, for the chosen value of the frequency of the oscillator 01 passes the upper side band of 10,500 to 11,500 cycles/sec.
  • This sid band whose fre-- quency spectrum includes the heterodyned fre quencies of 0 to 1000 cycles/sec. of the signals to be transmitted, is supplied to the frequencymodulator FM, in which modulator the carrier wave generated by an oscillator 02 is frequencymodulated by the frequencies supplied to the modulator.
  • the frequency spectrum of-the oscillations modulating the carrier wave includes the frequency band of 1000 to 10,000 cycles/secjtransmitted by the filter F1 and the frequency band of 10,500 to 11,500 cycles/sec. transmitted by the filter F3, which frequency bands do not comprise;
  • the oscillations frequency-modulated in the modulator are emitted by an antenna A.
  • the choice of the frequency of the oscillator 01 determines the width of the frequency spectrum of theoscillations modulating the carrier wave.
  • This frequency is preferably so chosen that the frequency spectrum of the modulating oscillationsis but slightly broader than the frequency spectrum of the signals to be transmitted; In fact, it is advantageous inthe receiver that the frequency spectrum should not be broader than is strictly necessary, since the energy of the disturbances produced in with an increasing width trum of the oscillations frequency-modulating the carrier wave. In fact, the energy of the disturbances occurring is proportional to sents the maximum frequency of the modulating oscillations.
  • the energy of thedisturbance appearing in the receiver is larger than will be the case upon reception of a frequency-modulated carrier wave; inwhich case the frequency spectrum lations is as broad as the frequency spectrum of the signals to be transmitted.
  • the amplified oscillations set up in the output circuit of the amplifier-HF are preferably supplied through a frequency transformer or modulator M2, to which are supplied oscillations locally generated by an oscillator 03, to a detector D, in which the fre-- quency variations of the carrier wave are transformed into amplitude variations which are subsequently rectified.
  • detector comprise a frequency spectrum which correspondsto the frequency spectrum of the oscillations modulating the incoming carrier wave and extends from 1000 to 10,000 cycles/sec. and from 10,500 to 11,500 cycles/sec. In order to transform this frequency spectrum into the frequency spectrum of the signals to be received,
  • the receiver increases of the modulating oscilthe oscillations in the output circuit of the detector D are supplied to two filters F3 and F4, of
  • the filter F3 transmits the frequency band I of that part of the signals to be transmitted which is transmitted by the filter F2 in the transmitter.
  • the frequencies of 10,500 to 11,500 cycles/sec. transmitted by the filter F4 are suppliedto a modulator M3, which has also supplied to it an oscillation which is generated by the oscillator 04 and has a frequency of 10,500 cycles/sec.
  • the modulator M3 there arise two frequency bands of 21,000 to 22,000 cycles/sec. and of 0 to 1000 cycles/sec. respectively, of which the lower side band including the frequencies Of 0 to 1000 cycles/sec. is transmitted .
  • Fig. 2a represents one form of construction of a device according to the invention, in which the of the frequency spectrum of the signals to be transmitted.
  • the parts corresponding 1 to the arrangement shown in Fig. 1a bear the -;same reference numerals; furthermore, it is assumed again that the frequency spectrum of the signals to be transmitted includes the frequency range of 0 to 10,000 cycles/sec.
  • the oscillations generated in the microphone Q which comprise the frequency spectrum of 0 to 10,000 cycles/sec. are supplied through the amplifier LFI to a modulator M4, which has also supplied to it an auxiliary oscillation supplied by, an oscillator 05 whose frequency at least corresponds to the highest signal frequency to be transmitted plus the lowest frequency which may still appear in the oscillations modulating the carrier wave I to be transmitted and amounts to say 30,000
  • the auxiliary oscillation supplied by the oscillator 06 has a frequency which is 1000 cycles/sec. lower than 7 frequency band of 30,000 to 453,000 cycles/sec. transmitted by the filter Fe and consequently supplies an oscillation having a frequency of 29,000 cycles/sec.
  • the modulator M two side bands comprising a frequency range of 59,000 to 70,000 cycles/sec, and of 1000 to 11,000 cycles/sec. respectively, the frequency spectrum of the lower side band being shifted by an amount of 1000 cycles/sec. with respect to the frequency spectrum of the signals to be transmitted.
  • the oscillator 06 should produce oscillations whose frequency lies beyond the side bands produced in the modulator M4; in order to achieve the desired displacement of the frequency spectrum of the signals to be transmitted the oscillator 05, provided the filter Fe transmits the upper side band of the side bands obtained in the modulator M4 which comprises the frequency range of 30,000 to 41,000 cycles/see, will consequently be tuned to a frequency which exceeds by 1000 cycles/ sec. the highest frequency of this frequency band, but if the filter F6 transmits the lowest side band of 30,000 to 20,000 cycles/sec, the oscillator 06 will be tuned to a frequency which is 1000 cycles/sec. lower than the lowest frequency of the lower side band. In both casesv the desired displacement of the frequency spectrum is accompanied by reversal of the frequency spectrum.
  • the receiver represented in Fig. 2b which is adapted for the reception of the frequency-modulated oscillations emitted by means of a device as shown in Fig. 2d, comprises a high-frequency amplifier HF, to which are supplied the oscillations picked up by the antenna A1, the frequency transformer or modulator M2 and. the detector D, the latter transforming frequency variations of the carrier Wave into amplitude variations which are subsequently rectified.
  • the oscillation supplied by the detector comprise afrequency spectrum which corresponds to the frequency spectrum of the oscillations modulating the incoming carrier wave and extends from 11,000 to 1000 cycles/sec. In order to transform this frequency spectrum thelowest frequency of the quency of into the'- frequency spectrumfiofthe signals to be received the oscillations-fin the-output circuit.
  • the detector-Dare supplied-itch modulator'Ms. having supplied to'it: an auxiliary oscillation supplied byan oscillator-10a whose frequency amounts to say 41,000-cycles/sec; 1 'fn-theimodulator Ms'the oscillations generated by'the. oscillator .07 are amplitude modulated by the oscillations. comprising the frequency spectrum of rooo ito 11,000
  • This lower side 'band is supplied through a filter F9, which, stops the carrier waveand-the upper the: low frequencynmplifler LFz and subsequently to-the l'oundspeaker in which the incoming oscih'ations, comprising a frequencyband of 0 to 10,000 cycles fisee, are transformeduagain into the. incoming soundvibrations'. 1 a l In'the. form of constructionirepresented in Fig.
  • the frequency of theioszci'llationsj supplied by the oscillators Os. endow corresponds to the: frethe oscillations produced in the transmitter by the oscillators O5 and 06 respectively.
  • the desired transformation may be obtained by tuning the oscillator 01 to a frequency of 31,000 cycles /sec. and the oscillator 08 to a frequency of 20,000 cycles/sec.
  • the frequency difference between the oscillators O5 and O6 in the transmitter and the oscillators O8 and O: in the receiver is equal to the minimum admissible modulation frequency of 1000 cycles/sec. in the transmitter plus the highest sign-a1 frequency of 10,000 cycles/sec. to be transmitted.
  • the difference between the oscillators 05, 0e and Os, 0': respectively consequently corresponds to 11,000 cycles/sec.
  • a source of wave energy of carrier wave frequency to be modulated a source of modulating potentials coupled to said source of wave energy to modulate the frequency of the latter in accordance with the modulating potentials, and means in said coupling for increasing the frequencies of a band of lower frequency modulation potentials by selected equal amounts which exceed the lowest modulation frequency to reduce at a receiving point distortion at said lower frequency modulation potentials due to multipath transmission comprising, filter circuits for separating a band of modulating potentials in the lower frequency range of said modulating potentials from the of the 'tiwo side bandsthus-produced side band, to
  • modulated wave energy amplifying means a frequency converter including a source of oscillations coupled to said amplifier, a frequency responsive detector coupled to said converter, means for selecting from said detector the modulation components corresponding to the components used to directly modulate said carrier in the transmitter, means for selecting from said detector the modulation components corresponding to the modulated subcarrier used at said transmitter, a demodulator for deriving from said modulated subcarrier the original modulation components in said band in the lower end of the modulation frequency components, and means at said receiver for recombining said modulation components.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Amplitude Modulation (AREA)
US480362A 1941-04-03 1943-03-24 Device for the transmission of signals by means of frequency-modulated carrier waves Expired - Lifetime US2455959A (en)

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Application Number Priority Date Filing Date Title
NL231617X 1941-04-03

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US2455959A true US2455959A (en) 1948-12-14

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BE (1) BE445078A (OSRAM)
CH (1) CH231617A (OSRAM)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2530926A (en) * 1944-04-22 1950-11-21 Radio Electr Soc Fr Short-wave, long distance communication system
US2719955A (en) * 1952-01-02 1955-10-04 Du Mont Allen B Lab Inc Transmission system
US3084328A (en) * 1958-06-12 1963-04-02 Philips Corp Suppressed carrier signle-sideband transmission system
US3147437A (en) * 1962-03-13 1964-09-01 Robertshaw Controls Co Single side band radio carrier retrieval system

Citations (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1491357A (en) * 1924-04-22 Harold w
US1907109A (en) * 1930-01-02 1933-05-02 Western Electric Co Radio signaling system
US2059719A (en) * 1932-05-25 1936-11-03 Rca Corp Radio telephone system
GB466071A (en) * 1935-09-18 1937-05-21 Standard Telephones Cables Ltd High frequency wave electrical signalling systems
US2111023A (en) * 1935-11-05 1938-03-15 American Telephone & Telegraph Noise and cross-talk reduction in telephone communication circuits
US2132205A (en) * 1937-06-23 1938-10-04 Bell Telephone Labor Inc Secret transmission
US2179182A (en) * 1936-11-27 1939-11-07 Rca Corp Frequency modulation circuits
US2212240A (en) * 1936-05-05 1940-08-20 Int Standard Electric Corp Carrier wave modulating system and apparatus
US2233183A (en) * 1938-11-12 1941-02-25 Gen Electric Frequency modulation system
US2301455A (en) * 1939-10-27 1942-11-10 Wireless Res Corp Apparatus and method for communication
US2323698A (en) * 1940-10-12 1943-07-06 Edwin H Armstrong Frequency modulation signaling system
US2389356A (en) * 1942-11-24 1945-11-20 Rca Corp Method of reduction of selective fading
US2402059A (en) * 1942-04-29 1946-06-11 Hazeltine Research Inc Secrecy communication system
US2407259A (en) * 1941-07-09 1946-09-10 Bell Telephone Labor Inc Transmission control in signaling systems
US2407308A (en) * 1941-01-16 1946-09-10 Lorenzen Robert Method and apparatus for secret signaling
US2408692A (en) * 1942-04-29 1946-10-01 Rca Corp Signaling system

Patent Citations (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1491357A (en) * 1924-04-22 Harold w
US1907109A (en) * 1930-01-02 1933-05-02 Western Electric Co Radio signaling system
US2059719A (en) * 1932-05-25 1936-11-03 Rca Corp Radio telephone system
GB466071A (en) * 1935-09-18 1937-05-21 Standard Telephones Cables Ltd High frequency wave electrical signalling systems
US2111023A (en) * 1935-11-05 1938-03-15 American Telephone & Telegraph Noise and cross-talk reduction in telephone communication circuits
US2212240A (en) * 1936-05-05 1940-08-20 Int Standard Electric Corp Carrier wave modulating system and apparatus
US2179182A (en) * 1936-11-27 1939-11-07 Rca Corp Frequency modulation circuits
US2132205A (en) * 1937-06-23 1938-10-04 Bell Telephone Labor Inc Secret transmission
US2233183A (en) * 1938-11-12 1941-02-25 Gen Electric Frequency modulation system
US2301455A (en) * 1939-10-27 1942-11-10 Wireless Res Corp Apparatus and method for communication
US2323698A (en) * 1940-10-12 1943-07-06 Edwin H Armstrong Frequency modulation signaling system
US2407308A (en) * 1941-01-16 1946-09-10 Lorenzen Robert Method and apparatus for secret signaling
US2407259A (en) * 1941-07-09 1946-09-10 Bell Telephone Labor Inc Transmission control in signaling systems
US2402059A (en) * 1942-04-29 1946-06-11 Hazeltine Research Inc Secrecy communication system
US2408692A (en) * 1942-04-29 1946-10-01 Rca Corp Signaling system
US2389356A (en) * 1942-11-24 1945-11-20 Rca Corp Method of reduction of selective fading

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2530926A (en) * 1944-04-22 1950-11-21 Radio Electr Soc Fr Short-wave, long distance communication system
US2719955A (en) * 1952-01-02 1955-10-04 Du Mont Allen B Lab Inc Transmission system
US3084328A (en) * 1958-06-12 1963-04-02 Philips Corp Suppressed carrier signle-sideband transmission system
US3147437A (en) * 1962-03-13 1964-09-01 Robertshaw Controls Co Single side band radio carrier retrieval system

Also Published As

Publication number Publication date
CH231617A (de) 1944-03-31
BE445078A (OSRAM)

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