US2433343A - Multichannel electrical communication system - Google Patents

Multichannel electrical communication system Download PDF

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Publication number
US2433343A
US2433343A US476071A US47607143A US2433343A US 2433343 A US2433343 A US 2433343A US 476071 A US476071 A US 476071A US 47607143 A US47607143 A US 47607143A US 2433343 A US2433343 A US 2433343A
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United States
Prior art keywords
frequency
frequencies
communication system
carrier
channel
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Expired - Lifetime
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US476071A
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English (en)
Inventor
Chatterjea Prafulla Kumar
Houghton Leslie Wilfred
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International Standard Electric Corp
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International Standard Electric Corp
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Publication date
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Publication of US2433343A publication Critical patent/US2433343A/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J1/00—Frequency-division multiplex systems
    • H04J1/02—Details
    • H04J1/06—Arrangements for supplying the carrier waves ; Arrangements for supplying synchronisation signals

Definitions

  • 'Ihepresent invention relates to arrangements for producing a series of frequencies equally spaced in the frequency spectrum and its application to the production of carrier frequenciesV in multi-channel lelectrical communication systems.
  • the present invention has for one of its objects the generation of a plurality of carrier frequencies, rigidly separated from each other and to the modulation of each independently, employing a minimum duplication of equipment and to the transmission of the signals from all channels as one transmission.
  • a wave rich in harmonics of the fundamental frequency thereof modulates a basic frequency thereby producing a series of modulation frequencies separated by a frequency interval equivalent to the fundamental frequency and spreading on either side of said basic frequency.
  • Fig. 1 is explanatory
  • Fig. 2 shows diagrammatically the transmitting end of a multi-channel communication system embodying the invention
  • Fig. 2A shows a modified transmitter system
  • Fig. 3 shows diagrammatically the receiver end of such system.
  • an oscillator or other source of carrier frequency is modulated by a train of electrical pulses, preferably of short duration, which resuit in a series of frequencies, separated by a frequency interval equivalentto the pulse repetition' frequency, and spreading on either side of the carrier frequency.
  • These frequencies are in effect the side band frequencies of the pulse train harmonics, and are as shown in Fig. l of the drawings where fc is the carrier frequency, and
  • f1, f2 and fs etc. are theside-band frequenciesdue to the pulse train fundamental frequency, second, third etc, harmonics respectively, the difference between any two frequencies, i. e., f1 and f2, or fc and f1 for example being equal to the pulse train repetition frequency fp.
  • Individual frequencies are then filtered out from this series to function as separate carrier frequencies and are modulated with the signal allotted to a particular carrier frequency or channel after which they are passed through the same amplifier and transmitted as a series of modulated carriers.
  • a receiver of the usual known type if selective enough may select any particular carrier, or ⁇
  • reference I represents a pulse generator and 2 a sinusoidal waveformloscillator, the output from which is fed to unit 3 which cnsists of a buifer stage and modulator stage for modulating the output of 2 by the output of IA resulting in a series of frequencies as shown inf.y
  • Fig. 1 The number of such frequencies is governed by the shape of the modulating pulse as Well as its duration time, and can readily be made to exceed a hundred or more if desired.
  • One frequency for each required signal channel can readily be obtained by appropriate filtering in known manner, which at the high frequencies normally used can be accomplished by normal tuned circuit technique although in some cases crystal filters may be found necessary.
  • Four channels are shown in Fig. 2, the appropriate carrier frequencies being obtained by lters 4, 5, 6 and 1; the outputs from which are then modulated in units 8, 9, I0 and II respectively, the modulating voltages being the signals which it is required to transmit through each channel and are applied at terminals 81, 91,
  • unit l2 The outputs from all of these channels are then combined by unit l2 and amplified before being fed to a radiating system TAIZ. It is of course essential that the frequency response of unit I2 be sufficient for the frequency spectrum required. If desired, in the case of a large number of channels separate final amplifiers may be Correction can also be applied to ⁇ each channel 3 so that the final signals radiated are all of the same amplitude.
  • the carrier frequencies to be radiated are very high frequencies it may be difficult in some cases to separate the individual carrier frequencies by lters 4', 5, 6 and I Fig. 2 and it will therefore, be an advantage to carry out the whole of the operation as explained for Fig. 2 at a convenient intermediate frequency; then after combining the individual modulated carriers they may be heterodyned by a local oscillator so as t produce the required high frequencies which may then be radiated after the necessary amplification.
  • a simple receiver of known type may be used for selecting any particular carrier frequency, and therefore signal channel, In the case Where the various carriers are very close to each other however, it is essential to have a band spread system incorporated in the receiver tuning arrangement.
  • Alternative receivers which may be used where flexibility of channel selection is essential, may include any pre-tuned circuit selection device, or an arrangement as shown schematically in Fig. 3 where the Whole band of signals is picked up by aerial system RAI3 and amplified by unit I3 which is an amplifier with the requisite Wideband frequency characteristic. The signals are then heterodyned by the local oscillator I4 and the produced I. F. signals are again amplified by unit I5, after which the various channels are separated out by filters, or tuned circuits I6, I1, I8 and I9 and the resulting signals are rectified by the corresponding units 20, 2l, 22 and 23 so that the signal transmitted by each channel can be obtained from terminals 201, 211, 221 and 231 respectively.
  • such signal may be transmitted in each channel by modulating the durations of the initial pulses generated in I Fig. 2A in known manner.
  • Energy from a signal source 25 is applied simultaneously With energy from pulse generator I to pulse duration modulator 24.
  • a modulation is equivalent to an ampli- 4 tude modulation of the component frequencies making up the pulse and can be received by any of the receivers tuned to one of the carrier frequencies in the outputs of filters 4'I.
  • means for producing a series of separate carrier frequency Waves including a generator of a series of electrical waves each having a form rich in harmonics of the fundamental frequency thereof and comprising a, generator of electric pulses of repetition frequency equal to the desired separation of the carrier frequency Waves, an oscillation generator producing an electrical f sinusoidal wave of a basic frequency, a modulating device to which are fed said wave rich in harmonics and said sinusoidal wave, and means for ⁇ modulating the durations of said pulses in accordance with the amplitudes of a signal wave, thereby effectively amplitude-modulating the different carrier frequency waves with the same signal wave.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Radio Relay Systems (AREA)
  • Transmitters (AREA)
US476071A 1942-03-12 1943-02-16 Multichannel electrical communication system Expired - Lifetime US2433343A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB3295/42A GB556079A (en) 1942-03-12 1942-03-12 Improvements relating to multi-channel electrical communication systems

Publications (1)

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US2433343A true US2433343A (en) 1947-12-30

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US476071A Expired - Lifetime US2433343A (en) 1942-03-12 1943-02-16 Multichannel electrical communication system

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US (1) US2433343A (fr)
FR (1) FR928802A (fr)
GB (1) GB556079A (fr)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2481516A (en) * 1946-03-22 1949-09-13 Lance R Jacobsen Mobile telephone system
US2504986A (en) * 1948-03-17 1950-04-25 Prestole Corp Snap-in spring fastener
US2574326A (en) * 1947-12-02 1951-11-06 Rca Corp Generating groups of currents
US2575993A (en) * 1948-11-27 1951-11-20 Bell Telephone Labor Inc Multiple carrier transmission system
US2595876A (en) * 1944-02-02 1952-05-06 Gen Electric Radio pulse-echo locating equipment
US2609438A (en) * 1947-01-24 1952-09-02 Sun Oil Co Seismic exploration apparatus
US2645680A (en) * 1946-10-03 1953-07-14 Int Standard Electric Corp Pulse distributor, including electric discharge devices
US2681949A (en) * 1950-02-09 1954-06-22 Nederlanden Staat Receiver for voice frequency telegraph systems
US2700753A (en) * 1948-06-28 1955-01-25 Phillips Petroleum Co Method of and apparatus for seismic prospecting
US2866970A (en) * 1956-05-31 1958-12-30 Itt Pulse communication system

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1447204A (en) * 1919-09-30 1923-03-06 American Telephone & Telegraph Plural modulation and demodulation circuits
US1461064A (en) * 1921-02-10 1923-07-10 American Telephone & Telegraph Multiplex transmission circuit
US1851721A (en) * 1930-05-22 1932-03-29 Gen Electric Oscillation generator
US1854986A (en) * 1930-05-17 1932-04-19 Gen Electric Method and means for producing high frequencies
FR733626A (fr) * 1930-01-02 1932-10-08 Materiel Telephonique Perfectionnements aux systèmes de signalisation utilisant des ondes modulées
US1985046A (en) * 1934-03-02 1934-12-18 Bell Telephone Labor Inc Electrical wave production
US2037799A (en) * 1934-02-28 1936-04-21 Rca Corp Ultrahigh frequency device
US2226459A (en) * 1935-11-23 1940-12-24 Philco Radio & Television Corp Signal-deriving circuit
US2266526A (en) * 1938-04-11 1941-12-16 Emi Ltd Electrical oscillation generator

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1447204A (en) * 1919-09-30 1923-03-06 American Telephone & Telegraph Plural modulation and demodulation circuits
US1461064A (en) * 1921-02-10 1923-07-10 American Telephone & Telegraph Multiplex transmission circuit
FR733626A (fr) * 1930-01-02 1932-10-08 Materiel Telephonique Perfectionnements aux systèmes de signalisation utilisant des ondes modulées
US1854986A (en) * 1930-05-17 1932-04-19 Gen Electric Method and means for producing high frequencies
US1851721A (en) * 1930-05-22 1932-03-29 Gen Electric Oscillation generator
US2037799A (en) * 1934-02-28 1936-04-21 Rca Corp Ultrahigh frequency device
US1985046A (en) * 1934-03-02 1934-12-18 Bell Telephone Labor Inc Electrical wave production
US2226459A (en) * 1935-11-23 1940-12-24 Philco Radio & Television Corp Signal-deriving circuit
US2266526A (en) * 1938-04-11 1941-12-16 Emi Ltd Electrical oscillation generator

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2595876A (en) * 1944-02-02 1952-05-06 Gen Electric Radio pulse-echo locating equipment
US2481516A (en) * 1946-03-22 1949-09-13 Lance R Jacobsen Mobile telephone system
US2645680A (en) * 1946-10-03 1953-07-14 Int Standard Electric Corp Pulse distributor, including electric discharge devices
US2609438A (en) * 1947-01-24 1952-09-02 Sun Oil Co Seismic exploration apparatus
US2574326A (en) * 1947-12-02 1951-11-06 Rca Corp Generating groups of currents
US2504986A (en) * 1948-03-17 1950-04-25 Prestole Corp Snap-in spring fastener
US2700753A (en) * 1948-06-28 1955-01-25 Phillips Petroleum Co Method of and apparatus for seismic prospecting
US2575993A (en) * 1948-11-27 1951-11-20 Bell Telephone Labor Inc Multiple carrier transmission system
US2681949A (en) * 1950-02-09 1954-06-22 Nederlanden Staat Receiver for voice frequency telegraph systems
US2866970A (en) * 1956-05-31 1958-12-30 Itt Pulse communication system

Also Published As

Publication number Publication date
FR928802A (fr) 1947-12-09
GB556079A (en) 1943-09-20

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