US1910977A - Wave transmission system - Google Patents

Wave transmission system Download PDF

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Publication number
US1910977A
US1910977A US556949A US55694931A US1910977A US 1910977 A US1910977 A US 1910977A US 556949 A US556949 A US 556949A US 55694931 A US55694931 A US 55694931A US 1910977 A US1910977 A US 1910977A
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Prior art keywords
frequency
groups
waves
group
filters
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US556949A
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English (en)
Inventor
Jr Charles L Weis
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AT&T Corp
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Bell Telephone Laboratories Inc
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Publication date
Priority to FR744002D priority Critical patent/FR744002A/fr
Priority to NL35164D priority patent/NL35164C/xx
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US556949A priority patent/US1910977A/en
Priority to GB21416/32A priority patent/GB405026A/en
Priority to DEI45103D priority patent/DE613221C/de
Application granted granted Critical
Publication of US1910977A publication Critical patent/US1910977A/en
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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

  • This invention relates to; Wave transmise sicn sy tems and. more p rticularly to Wav transmission systems utilizing a plurality of fr quen y ranges o multiplex transmis- It is an objectof theinvention to increase the number of Wave transmission channels that may be superposed Within a given range of frequency. More specifically the object of .thepresent invention is to decrease the frequency interval between adjacent chain nels in amultiplex carrier wave signaling systemvvithout detrimentally affecting the' quality of transmission. 4
  • each channel filter passes not only a desired bandof signals but also above and below that band, undee sired waves, such as, in the direction of transmission, a part of a signal side band that is tobe suppressed, or in the opposite direction, signals from the adjacent, parallelconnected channel.
  • impedance presented by the filter in one 1 channel to the filter in an adjacent channel may be" quite. low and irregular within the passband of the latter. Since each filter is designed to work into a particular impedance, reflection phenomena and distortion .luay arise,especiaily at frequencies near edges of the bands of waves. At. a receiving station a similar dlstortion may occur.
  • the frequency interval between adjacent channels may be consider.
  • applicants system is character ized by a division into two ormore groups at the terminal stations of the channels that tend to interfere with each other.
  • Each group is isolated from the others but connected in energy transfer relation with the Where the channels are separated into two groups, each group may contain channels in alternate frequency :b'ands. lVith the channels connected in" parallel in each group thus separated from each other by the Width of a channel,
  • a filter in a channel of one group can have no effect on signals in either of the two immediately adjacent frequency channels, as the latter are in the other group and are isolated therefrom.
  • the filters in each group are connected in series instead of in parallel, advantage is also derived by isolating the groups in accordance with the present invention.
  • the group isolating means may take any one of several forms.
  • applicants invention is featured by unilaterally conducting devices inserted in the respective group connections to isolate one group from another.
  • a space discharge amplifier can be used to good advantage for this purpose.
  • Waves in a given frequency channel in one group are freely transmitted either to or from the common circuit. They are not affected by the filter in either of the two adjacent frequency channels, these filtersbeing in another group, because they are isolated therefrom by virtue of the unilaterally conducting properties of the device.
  • the third order products may thereby be removed to a sufficient extent from the borders of the signaling bands that they are effectively suppressed by thefilter.
  • the lowest frequency of the band as demodulated be more than half the highest one so that third order products will not fall within it.
  • Fig. 1 shows the present invention as incorporated in the transmitting circuit of a carrier wave transmission system employing successive stages of modulation and successive stages of demodulation;
  • Fig. 2 shows the receiving circuit associated with the transmitting circuit of Fig. 1;
  • Figs. 3 and 1 show alternative forms of the group separating means
  • Fig. 5 shows the impedance characteristics of the frequency selective devices employed in the channels of the first stage of modulation and the second stage of demodulation of said system
  • Fig. 6 shows the impedance characteristics of the frequency selective devices employed in the second stage of modulation and in the first stage of demodulation of said sys tem to pass groups of doubly modulated waves.
  • a terminal station for translating the waves in a multiplicity of low frequency circuits to their respective positions in the wide frequency spectrum that is used for transmission purposes.
  • the frequency translation is accomplished in two steps.
  • the low frequency circuits are first divided into a plurality of groups A, B, C, etc. Within each group the signal waves are then transferred to respective positions in a band of carrier signal frequencies.
  • These several groups of carrier signals are next translated, as groups,'to positions in a still wider range of frequencies and applied to a transmission line.
  • each group there may be represented perhaps sixtylow frequency lines Z Z etc., adapted to transmit telephone, telegraph or other signaling waves.
  • each of these lines there is an individual modulator M of any suitable type for applying the signaling waves to respective high frequency or carrier waves supplied by the respective generatorsG G etc.
  • the modulators are preferably of the carrier suppressing type such as disclosed in J. R. Carson Patent 1,343,306, June 15, 1920.
  • the relative frequencies of the carrier wave generators may be accurately maintained by controlling them with a common base frequency wave, as shown, for example in B. W. Kendall Patent 1,773,901, August 26, 1930.
  • a band of frequencies ranging from 250 to 2750 cycles may be required.
  • the band passing filters CBF CBF etc., to which the two signal side bands from the preceding respective modulators are applied are accordingly designed each to transmit a band of modulated carrier waves 2500 cycles in width.
  • Th filters. are pr e ab y of the t pe ut liz ng piezoelec ri crys al s h s eseribed in a pp t n of W. P. Me on bearing Serial- No. 489,268, filed October 17, 1930, although any other suitable type of lecti g r uit m y be us in ac anc with this invention.
  • the frequency separation of the carrier waves may be ⁇ 1:000 cycles.
  • a filter in one channel, filter CBF for example, has but little efiect, therefore, on the band .of signals issuing from the filter CBF in the nex para le n t d nne t th lowe t freque cy f the latter be it will be noted th t th ra teristic imp an e offilte C' i1 ishigh and t at is filter thereforehas a negligible effect on the impedance presented to the filterin the adj acent channel, A similar condition obtains in the group represented by the lower row of rectangles. Since the vacuum tube .am-.
  • T a circuit for translating the wide bands of singly-modulated carrier waves arriving from the several identical groups A, B, C, etc,, over lines L L etc, to respective positions in a second carrier frequency range for application to transmission line LE.
  • the apparatus required for this second stage of modulation may be the sameas that used for the first stage except asto the frequency range for which it is designed.
  • the band of waves applied to each of the modulators M extends from26025 to498/75 kilocycles per second .in the embodiment herein described.
  • the frequencyinterval between the upper band of one translated group and the.lowerband ofthe adjacent translated group will be the same as that between the bands within the groups, via, 1500 cycles.
  • the group band-passing filters GBF GBF etc. are designed topass only the lower ofthe side bands created. They arepreferably of the electricaltype shown in G. A. Campbell Patent 1,227,113, issued May 22, 1917. I
  • the group modulators M are divided into two groups each containing alternate frequency bands.
  • the output filters GBF GBF etc. are connected to the'collecting bus TCB while filters GBF GBF etc., are associated with bus T013
  • the first group is connected to a vacuum tube amplifier A the second to a similar amplifier A
  • a shunt resistance may again be used as a terminating impedance.
  • These amplifiers may be connected directly to the transmission line LE, or through a power amplifier A as illustrated.
  • a pair of coaxial conductors a structure such as shown in H. R. Nein Patent 1,781,124, November 11, 1930, being'suitable. It is not essential that the channel modulating circuit and the group modulating circuit be immediately associated with each other, and the lines L L etc., connecting them may be transmission lines of coaxial or any other suitable type.
  • Fig. 6 shows the typical impedance-frequency characteristics of the group bandpassing filters GBF,, GBF etc.
  • group bandpassing filters GBF, GBF etc. For purposes of illustration only, four signal bands. represented by the shaded rectangles, are shown in each group, although in the embodiment herein described, the sixty chan- .els of each of the groups A, B, (J, etc., would actually be present. Because of the alternate grouping arrangement, there is a wide frequency separation between the groups of channels connected to either bus.
  • Fig. 6 shows that the impedance of the filters, GrBF for example, rises rapidly in this frequency interval. At even the lowest frequency of the e group passed by filter GBF the characteristic impedance of filter GrBF is so high that the latter filter has practically no shunting effect.
  • the vacuum tube amplifiers A and A connecting the two collecting buses to the common transmission line, the shunting effect of a filter in. one group on signals from a group connected to the other bus is eliminated.
  • This isolation of the groups is identical with that provided in the channel circuits by the amplifiers A and A
  • the amplifiers are of the push-pull type and capacitively balanced against feed-back effects.
  • the impedance of one group filter such as GBF very low in the frequency ranges of the groups immediately above and below it and distortion wouldtherefore be introduced, especially in the frequency ban'ds'at the edges of those groups;
  • a'receiving terminal circuit for separating the carrier frequency signals arriving over transmission line LE and for reducing these signals to telephone frequencies for application to a multiplicity of telephone circuits.
  • the first stage or group separation and'demodulation occurs in the apparatus V; Each separated and demodulated group is'then completely divided into its component signaling bands, which are then finally demodulated.
  • the grouping arrangement of these receiving circuits may follow that of the transmitting circuits, as illustrated here, although this is not essential. This arrangement is preferable, however, since it permits the use of a common carrier wave source for modulation and demodulation and reduces the number required.
  • Signals from line LE are passedthrou 'h an amplifier A and through two pat s containing amplifiers A and A respecof different selective circuits tively.
  • To amplifier A is connected a diswave generators in the modulating circuits.
  • the waves issuing from each of demodulators DM represent in the embodiment shown, sixty carrier wave signal channels extending in frequencyfrom'260.25 kilocycles to 498.75 kilocycles.
  • the characteristics of the several group filters GBF GBF etc may be the same as those of filters GBF GBlI', etc.,- shown in Fig. 6. Because of the wide frequency separation of the groups connected to either bus, there is practically no tendency for signals in one frequency group to be affected by the band filters of the adjacent groups connected to the same bus. There is no tendency for the signals transmitted through amplifier A to filter GBFQ, for example, to be shunted by the filters GrBF and GBF in the adjacent frequency channels since the latter are isolated by amplifier A The selectivity requirements on the group filters may be considerably reduced in View of the would ordinarily attend this broadening of the attenuation-frequency characteristic;
  • the course of the carrier wave band applied to the-groupsA, B, C, etc., of the channel circuits is.- similar to the course of mthe groupsof bands through the circuit V.
  • group A for example, 'the incoming waves are applied tothe two amplifiers A, and Am, the firstof which is connected to the distributing bus DB and the second, to
  • Figs. 3 and 4 are shown circuits alternative to the amplifier circuits used-to separate the groups ofalternate channels in a transmitting or areceiving station.
  • a resistancepad 7, Sis inserted'm each of the'group connections instead of an amplifier.
  • the leads 9 ofpad 7 and leads of pad 8 are connected to the respective collecting buses with whlch the two groups of filters are assoclated.
  • Leads "19 may'beconnected to the common transmission lines. L ,L etc., in the 'embodiment shownl in. Fig. 1. Signals in a given frequency band applied, for example, to leads ware-attenuated by the resistance pad 8' and pass to the transmission line through leads'19.
  • the adjacent frequency channels are in the group connected to leads 9 and the filters therein are practically isolated, so farastheir effect on signals from pad 8 is concerned, by pad 7. Although these latter filtersjmay tend to have a high shunting effect in the frequency range 'of o the band issuing from pad8, this effect is made negligible byvirtue of the attenuation of pad 7. An attenuation of decibels was found a satisfactory value for the pads 7,8 in one particular case.
  • the isolating action may be expressed also in terms of reflected waves. Onehomponent of the waves issuing from padf8 passes out through leads19; another component passes through pad 7 is reflected and returns at a level at least decibels lower than that at which it entered.
  • waves arriving through leads 19 are substantially unaffected by the characteristics of the filtering devices connected to leads 9 and 10. r
  • Fig. 4 a hybrid coil for isolating one group from a second one.
  • thenominal input and outputleads 22 and21 respectively of the hybrid coil are in conjugate relation with each other but in bilateral energy transfer relation with leads 23. Signals to 'or from a filter group connected to either of the leads 21 or 22, are therefore not affected by the filters of the other group.
  • Another feature of the present invention comprises the proportioning of carrier and signal frequencies observed in its preferred embodiment. Besides the two groups of signal side bands, there are created by the groupmodulators other and undesired modulation products. Third order products are usually of high level and difficult to suppress. Their position in the frequency spectrum is, determined by the frequency 0 of the carrier wave and by the highest and low est frequencies, fh and fl, respectively, of the signal Waves applied to the modulator.
  • the band of Waves applied tothe group modulators M of Fig. 1 is limited to an approximately .240 kilocycle band extending from 260.25 kilocycles per second to 498.75 kilocycles per second, these extreme frequencies having a ratio of 1.92 to 1.
  • the control over the ex treme frequencies of the telephone signal bands in the channel modulating circuits can, of course, be only limited. Third order products must, therefore, be controlled in some other manner, as by modulating at low power levels.
  • a common transmission circuit for said Waves for said Waves, a plurality of filters adapted to pass respective ones of said bands of waves, said filters being connected in a plurality of groups, the frequency bands represented in each of said groups being respectively intermediate those in the other of said groups, and means to connect said groups simultaneously to said transmission circuit while effectively isolat ing said groups from each other.
  • a multiplex signaling system a plurality of selective devices adapted to transmit waves in respective frequency ranges, a circuit adapted to transmit waves in all of said frequency ranges, bilaterally conducting circuits each connecting together a plurality of said devices lying in non-adjacent frequency ranges, and respective means simultaneously connecting saidvbilaterally conducting circuits and said first mentioned circuit, said means being adapted to reduce the mutual effect of selectve devicesin adjacent frequency ranges.
  • a mult iplex wave transmission system means to transmit waves in a plurality of frequency channels, a plurality of means to transmit waves in respective ones of said frequency channels, means or separating said latter means into groups, each of said groups being comprised of transmitting means in alternatefrequency channels, and means for associating said groups with said first mentioned transmitting means including meansimpeding the transmission of waves between said groups.
  • a plurality of circuits for translating waves in individual frequency ranges a pair of conductors for transmitwaves in a plurality of said frequency ranges, bilaterally conducting means to connect said plurality of circuits in a plurality of groups, the circuits included in each of said groups being adapted to transmit ing said groups with said pair of conduc-,
  • said translating means comprising a space discharge device.
  • a multiplex signaling system a plurality of circuits adapted to transmit waves in-individual frequency ranges, frequency selective means in each of said circuits, said means being of such selectivity that they are capable of transmitting with relatively small attenuation waves in adjacent frequency ranges, means to connect said circuits in a plurality of groups, the frequency ranges in each group being respectively intermediate those of another of said groups, a multiplex transmission circuit and respective means simultaneously connecting said groups thereto, said latter means each being adapted to reduce the effect of the frequency selective means in the group associated therewith on waves from others'of said groups.
  • a common transmission circuit for said waves for said waves, a group of filters adapted to pass respective ones of said bands of waves, a filter adapted to pass a band of waves intermediate in frequency bands passed by said group of filters, and means simultaneously connecting said filters in energy transfer relation with said transmission circuit, said means providing apath of low transmission efliciency between said filter and said group of filters.
  • a plurality of signaling circuits modulating means for applying the waves in each thereof. to individual carrier waves, frequency selective means adapted topass respective bands of the waves produced by said modulators, each of said selective means passing in common with the corresponding means for adjoining frequency bands frequencies lying in the range between signal bands, means to connect said circuits inparallel in a plurality of groups, the signal bands represented in each of said groups being separated from each other by at least the width of one single band, a common signaling circuit and individual means to connect said groups thereto, each of said last mentioned means having a high attenuation in at least one direction of transmission, the range of frequencies applied to each of said modulators being substantially less than 2:1.
  • a plurality of signaling circuits frequency selective means in eachof said. latter circuits adapted to pass respective ones of said plurality of frequency bands, said selective means passing in common with the corresponding frequency bands, fre quencies lying in the range between signal means for adjoining bands, means to connect said plurality of circuits in parallel in a plurality of groups, the signal bands represented in each of said groups being separated by at least the width ofone signal band, individual means to connect said groups to said first mentioned circuit, each of said lastmentioned means having a high attenuation in at least one direction of transmission, means in each of said plurality ofcircuits for combining the signal waves therein with a demodulating wave, the range of frequencies produced by each of said demodulating means being substantially less than 2:1.
  • a plurality of circuits adapted to translate waves in different frequency bands means to connect said circuits in two groups, the frequency bands translated by the circuits of eac of said groups being respectively intermediate those in the other of said groups, a circuit adapted to transmit waves in all of said frequency bands, and means to; connect said groups in energy transfer relation with said last mentioned circuit and in conjugate relation with each other.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Transmitters (AREA)
  • Mobile Radio Communication Systems (AREA)
US556949A 1931-08-14 1931-08-14 Wave transmission system Expired - Lifetime US1910977A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
FR744002D FR744002A (de) 1931-08-14
NL35164D NL35164C (de) 1931-08-14
US556949A US1910977A (en) 1931-08-14 1931-08-14 Wave transmission system
GB21416/32A GB405026A (en) 1931-08-14 1932-07-29 Carrier current transmission system
DEI45103D DE613221C (de) 1931-08-14 1932-08-13 Traegerwellensignalanlage

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Application Number Priority Date Filing Date Title
US556949A US1910977A (en) 1931-08-14 1931-08-14 Wave transmission system

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US1910977A true US1910977A (en) 1933-05-23

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DE (1) DE613221C (de)
FR (1) FR744002A (de)
GB (1) GB405026A (de)
NL (1) NL35164C (de)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2550198A (en) * 1944-10-10 1951-04-24 Marzin Pierre Coaxial-cable carrier system
US2657269A (en) * 1947-01-02 1953-10-27 Int Standard Electric Corp Electric pulse modulation system of communication
US2844711A (en) * 1953-06-08 1958-07-22 Motorola Inc Multiple frequency channel multiplex communication system
US2871293A (en) * 1954-09-17 1959-01-27 Itt Multichannel telephone carrier system
US2895009A (en) * 1953-06-29 1959-07-14 Itt Channeling system for frequency spectrum transmission
US2902673A (en) * 1953-04-10 1959-09-01 Donald G C Hare Selective signalling device
US3754101A (en) * 1971-07-02 1973-08-21 Universal Signal Corp Frequency rate communication system

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE745229C (de) * 1939-01-15 1944-03-01 Lorenz C Ag Schaltung zum Zusammenfuehren der Ausgaenge von abgestimmten Verstaerkern auf gemeinsame Verbraucher
DE865151C (de) * 1943-05-18 1953-01-29 Siemens Ag Einseitenband-Traegerfrequenz-Fernsprechsystem
DE973493C (de) * 1950-09-28 1960-03-10 Philips Nv Einseitenbandtraegerfrequenzfernsprechsystem
US3771064A (en) * 1972-07-03 1973-11-06 Electronic Labor Inc Bidirectional signal processing means

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2550198A (en) * 1944-10-10 1951-04-24 Marzin Pierre Coaxial-cable carrier system
US2657269A (en) * 1947-01-02 1953-10-27 Int Standard Electric Corp Electric pulse modulation system of communication
US2902673A (en) * 1953-04-10 1959-09-01 Donald G C Hare Selective signalling device
US2844711A (en) * 1953-06-08 1958-07-22 Motorola Inc Multiple frequency channel multiplex communication system
US2895009A (en) * 1953-06-29 1959-07-14 Itt Channeling system for frequency spectrum transmission
US2871293A (en) * 1954-09-17 1959-01-27 Itt Multichannel telephone carrier system
US3754101A (en) * 1971-07-02 1973-08-21 Universal Signal Corp Frequency rate communication system

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Publication number Publication date
NL35164C (de)
DE613221C (de) 1935-05-18
FR744002A (de) 1933-04-10
GB405026A (en) 1934-01-29

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