US2156278A - System of carrier current transmission - Google Patents

System of carrier current transmission Download PDF

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Publication number
US2156278A
US2156278A US76382A US7638236A US2156278A US 2156278 A US2156278 A US 2156278A US 76382 A US76382 A US 76382A US 7638236 A US7638236 A US 7638236A US 2156278 A US2156278 A US 2156278A
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Prior art keywords
carriers
frequency
carrier
frequencies
sidebands
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Expired - Lifetime
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US76382A
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English (en)
Inventor
Dekker Jan Maurits Douwes
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Associated Electric Laboratories Inc
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Associated Electric Laboratories Inc
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J1/00—Frequency-division multiplex systems
    • H04J1/02—Details
    • H04J1/04—Frequency-transposition arrangements
    • H04J1/045—Filters applied to frequency transposition

Definitions

  • each group of two channels is separated from the 10 are a requirement; moreover, these filters have adjacent groups by a single band filter.
  • the to be of relatively small band-pass width, in pardistance between the carrier frequencies is made ticular for the higher frequencies. The lattery such that they substantially coincide with the requirement necessitates Iaccurate tuning of the limiting frequencies of the pass bands.
  • a receiver may be used in which the currents from the transmitting circuit areconducted along two diiierent transmission paths, each of which its supplied with one of the corresponding carriers, and each of which includes a demodulator followedv by low-frequency selective transmitting means.
  • Fig. 1 is a diagrammatic representation of a conventional form of carrier-current transmission system
  • FIG. 2 is a diagrammatic representation of a carrier-current transmission system in accordance with my invention.
  • Fig. 3 is a block diagram of a carrier-current transmission system in accordancewith my invention.
  • Fig. 4 shows graphically the performance of a systemaccording to Fig. 3.
  • tical arrows are spaced at 400G-cycle intervals.
  • Fig. 2 4 represents the frequency range oiV a transmitting medium, extending from 0 to about 40 kilocycles. As shown, this region comprises 9 channels, 8 of which are combined in pairs, in accordance with the invention, in such' a manner that their high modulation frequencies are substantially' adjacent, the lower limits of the audio-frequency region lying near the cut-o5 frequencies of the respective transmitting circuits, which Vare connected to the transmitting medium...l
  • the transmitting characteristics of these circuits are schematically'shown in Fig. 2
  • the arrows vi. indicate the yAs will be evident upon comparison with Fig. 1, the system according to the invention provides a saving of ⁇ about 50' percent in the number of filters required.
  • the suppression bands are twice as wide in the new system as inthe old; this permits locating the sidebands not desj tined for transmission entirely in the suppression bands, while maintaining the same useful per- Y- centage o f the entire transmitting range.
  • the carriers may be suppressed more -or less completely by the use of balanced modulators
  • the attenuation near Vthe edges of the pass bands may also contribute to'this suppression.
  • the functioning'of the system is not dependent on the strength ofthe transmitted carriers.
  • y BYl these meansfthe' suppression fbands, of both thel 'Ihe arrangement of apparatus for a system functioning according to the scale division of Fig. 2 may be as shown symbolically in Fig, 3.
  • and 22 are connected through band pass filter Y 23 tothe line.
  • and 22 are supplied from audio-frequency sources 24 and 25, respectively, and additionally have supplied to them carriers I and II, respectively, as shown.
  • Modulators 2i and 22 are arranged to suppress lli the carriers.
  • band filter 4 is shown connected to the line.
  • Band filters 4 and 23 may, for instance, have the transmitting properties shown graphically in Fig. 2at l, a pass band being .shown at a, -and a 15 suppression band at b.
  • the sidebands passed,u by filter 4 are supplied to a pair of parallel transmission paths 5 and 6, which include demodulators 1 and 8, respectively.
  • Fig. 4a shows the frequencies which are passed by the-band, filters 4 and 23.
  • Block I represents the upper sideband transmitted by carrier I
  • block II corresponds to the lower sideband of carrier II. Carriers I and II are not transmitted, and hence are indicated by broken lines.
  • Fig. 4b shows the frequencies which are passed by the-band, filters 4 and 23.
  • Block I represents the upper sideband transmitted by carrier I
  • block II corresponds to the lower sideband of carrier II.
  • Carriers I and II are not transmitted, and hence are indicated by broken lines.
  • - shows the voice or audio frequencies which appear at the output of low-pass lter 9, corresponding with theupper sideband of carrier I 45 'with'the -lower sideband of carrier II and represented by block II. Since these frequencies cover the same range as those represented by block -I of Fig. 4b, block II appears in the corresponding position in Fig. 4c.
  • the audio frequencies which correspond with the upper sideband of carrier I are very weak at the output of demodulator 8 and hence do not appear at the output of filter I0. Therefore they are represented by'dotted block I.
  • the curve Il of Fig. 4c indicates the operating characteristics of lters 9 and l0.
  • y l y Fig. 5 illustrates the application of the principle of the invention to a system in which modulation and demodulation lare effected in two stages, analogous manner to the operation 10 vof a. superheterodyne receiver.
  • a separate first modulator is provided for each channel.
  • the signals of one of the channels. which shall make up such a pair are modulated with the carrier do in the iirst modulator I2, the other channel being modulated with the carrier do' in the second first modulator I3.
  • the carriers do and du' are situated respectively near the upper and lower pass-band limits of the band filter shown in the right-hand upper portion of Fig. 5, curve I4 being the attenuation characteristic of this filter.
  • a separate auxiliary modulator I5 is provided for each pair of channels, the sidebands passed by the band filter being modulated in this modulator with an auxiliary carrier dn, which has a different frequency for each set of two channels and which is suppressed by the modulator.
  • the outputs of the auxiliary modulators I5 are connected'to the line or other transmitting medium.
  • the transmission medium or line is provided with as many auxiliary modulators as there are pairs of channels.
  • iliary modulator I6 is supplied with the auxiliary carrier du and thus transposes one pair of sidebands within the pass band of a band filter Il. These filters are-present in a number equal to the number -of the pairs of sidebands.
  • - 1)th sidebands are-passed to the input of band filter I1.
  • the demodulators I8 and I9 the received currents from the output of the filter II are demodulated to eliminate the carriers do and do'.
  • frequency bands of a pair of channels are juxtaposed in such a manner that the portions conl taining the harmonics of speech (which represent The aux-l very little energy) are near each other, these bands may be approached quite closely without entailing serious diiliculties in audio-frequency filtering.
  • the pass band of each filter is thereby made 'about twice as wide as in the known system.
  • Anv additional advantage of the system is that if occasion arises a musical program may be transmitted in lieu of a pair of channels, the networks being retained unchanged.
  • a carrier transmission system including plural sources of modulation; plural sources of carriers, said carriers being alternately spaced in frequency; modulators for combining each of said modulations with one of said carriers to produce plural modulated carriers each having upper and lower sidebands; transmitting filters each connected to frequency-adjacent pairs of said modulators, said filters being adapted to suppress. the carriers, the lower sideband of the lower-frequency carrier, ⁇ and the upper sideband of the higher-frequency carrier in each of said pairs; and unitary means for simultaneously transmitting the remaining pairs of upper and lower sidebands to a receiving station.
  • a carrier transmission system including plural sources of modulation; plural sources of carriers, said carriers being alternately equally spaced in frequency; modulators for combining each of said modulations with one of said carriers to produce plural modulated carriers each having upper and lower sidebands; transmitting filters each connected to frequency-adjacent pairs of said modulators, said filters being adapted to suppress the carriers, the lower sideband of the lower-frequency carrier, andthe upper sideband of the higher-frequency carrier vin each of said pairs; and unitary means for, simultaneously transmitting theremaining pairs of upper vand lower sidebands to a receiving station.
  • a carrier transmission system including plural sources of modulation; plural sources of carriers, said carriers being alternately spaced in frequency; modulators for combining each of said modulations with one of said carriers to produce plural modulated carriers each having upper and lower sidebands; transmitting filters each connected to frequency-adjacent pairs of said modulators, said filters being adapted to suppress the carriers, the lower sideband of the lower-frequency carrier, and the upper sideband of the higher-frequency carrier in each of said pairs;
  • I'he method of conducting plural communications in a single carrier transmission medium which comprises impressing said communications separately upon carriers alternately equally spaced in frequency throughout a frequency range, suppressing the carriers, suppressing a1- ternate upper and lower sideband frequencies, and transmitting the remaining lower and upper sideband frequencies through said medium to a receiving station, the spacing of said carriers exceeding -the frequency band occupied by each pair of said remaining sideband frequencies.
  • the method of conducting plural communications in a single carrier transmission medium which comprises impressing said communications separately upon carriers alternately spaced in frequency to produce modulation of said carriers with resulting upper and lower sidebands, suppressing said carriers and alternate upper and lower sidebands so that the remaining alternate lower and upper sidebands constitute adjacent pairs of sidebands, the frequency limits of each pair corresponding to the lower modulation frequencies, and transmitting said pairs of sidebands through said medium to a receiving stationjthe spacing of said carriers exceeding the frequency band occupied by each of said pairs of sidebands.
  • the method ofV conducting plural communications in a single carrier transmission medium which comprises impressing said communications separately upon carriers alternately equally spaced in frequency to produce modulation of said carriers with resulting upper and lower sidebands, suppressing said carriers and ⁇ alternate upper and lower sidebands so that the remaining alternate' lower and 'upper sidebands constitute adjacent pairs of sidebands, the frequency limits of each pair corresponding to the lower modulation frequencies, and transmitting said pairs of sidebands through said medium to va receiving station, the spacing of said carriers exceeding the frequency band occupied by each of said pairs of sidebands.
  • I'he method of conducting plural communications in a single carrier transmission medium which comprises impressing said communications separately upon carriers alternately spaced in frequency throughout ra frequency band, suppressing the carrier frequencies,suppressing alternate upper and lower sideband frequencies, trans-A mitting the remaining lower and upper sideband frequencies through said medium to a receiving station, removing any remaining residue of the suppressed upper and lower sideband frequencies, separating said remaining lower and upper sideband frequencies into pairs each consisting of an upper sideband and an adjacent higher-frequency lower sideband, supplying the previously suppressed carrier frequencies separately to each of said pairs, and demodulating each carrier and its -associated sideband frequencies to reproduce said communications.
  • the method of conducting plural communications in a single carrier transmission medium which comprises impressing said communications separately upon -carriers alternately spaced in frequency to produce modulation of said carriers with resulting upper and lower sidebands, suppressing said carriers and alternate upper and lower sidebands so that the remaining alternate lower and upper sidebands constitute adjacent pairs of sidebands, the frequency limits of each pair corresponding to the lower modulation frequencies, transmitting said pairs of sidebands through said medium, conducting each of said pairs separately to a pair of demodulators, supplying the previously suppressed carriers separately to said demodulators, and substantially suppressing all frequencies in the outputs of said demodulators except the modulation frequencies corresponding to said plural communications.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Transmission Systems Not Characterized By The Medium Used For Transmission (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
  • Radio Relay Systems (AREA)
US76382A 1935-04-30 1936-04-25 System of carrier current transmission Expired - Lifetime US2156278A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL456270X 1935-04-30
DES0123063 1936-06-18

Publications (1)

Publication Number Publication Date
US2156278A true US2156278A (en) 1939-05-02

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US76382A Expired - Lifetime US2156278A (en) 1935-04-30 1936-04-25 System of carrier current transmission

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US (1) US2156278A (no)
BE (1) BE415104A (no)
DE (1) DE699830C (no)
FR (2) FR810818A (no)
GB (2) GB456270A (no)
NL (1) NL42529C (no)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2479701A (en) * 1944-02-07 1949-08-23 William C De Vry Transmitting system
US2489361A (en) * 1945-05-02 1949-11-29 Hartford Nat Bank & Trust Co Multichannel carrier wave system employing multiple modulation
US2509716A (en) * 1944-05-08 1950-05-30 Radio Electr Soc Fr Arrangement for secret radio telephony
US2621325A (en) * 1946-08-20 1952-12-09 Radio Electr Soc Fr Plural modulation multiplex system
US20070133993A1 (en) * 1999-12-29 2007-06-14 Forster Energy Llc Optical communications using multiplexed single sideband transmission and heterodyne detection

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE928110C (de) * 1943-02-12 1955-05-23 Aeg Vierdraht-Traegerfrequenzuebertragungssystem
US2574326A (en) * 1947-12-02 1951-11-06 Rca Corp Generating groups of currents

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2479701A (en) * 1944-02-07 1949-08-23 William C De Vry Transmitting system
US2509716A (en) * 1944-05-08 1950-05-30 Radio Electr Soc Fr Arrangement for secret radio telephony
US2489361A (en) * 1945-05-02 1949-11-29 Hartford Nat Bank & Trust Co Multichannel carrier wave system employing multiple modulation
US2621325A (en) * 1946-08-20 1952-12-09 Radio Electr Soc Fr Plural modulation multiplex system
US20070133993A1 (en) * 1999-12-29 2007-06-14 Forster Energy Llc Optical communications using multiplexed single sideband transmission and heterodyne detection
US7447436B2 (en) * 1999-12-29 2008-11-04 Forster Energy Llc Optical communications using multiplexed single sideband transmission and heterodyne detection

Also Published As

Publication number Publication date
FR810818A (fr) 1937-03-31
GB456270A (en) 1936-11-05
FR823061A (fr) 1938-01-13
NL42529C (no)
DE699830C (de) 1940-12-07
GB474021A (en) 1937-10-25
BE415104A (no)

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