US2510987A - Multiplex time modulated electrical pulse demodulation system - Google Patents

Multiplex time modulated electrical pulse demodulation system Download PDF

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Publication number
US2510987A
US2510987A US602805A US60280545A US2510987A US 2510987 A US2510987 A US 2510987A US 602805 A US602805 A US 602805A US 60280545 A US60280545 A US 60280545A US 2510987 A US2510987 A US 2510987A
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Prior art keywords
pulses
pulse
channel
circuit
valve
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Expired - Lifetime
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US602805A
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English (en)
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Levy Maurice Moise
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International Standard Electric Corp
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International Standard Electric Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J3/00—Time-division multiplex systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J3/00—Time-division multiplex systems
    • H04J3/02—Details
    • H04J3/04—Distributors combined with modulators or demodulators
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J3/00—Time-division multiplex systems
    • H04J3/02—Details
    • H04J3/04—Distributors combined with modulators or demodulators
    • H04J3/042—Distributors with electron or gas discharge tubes

Definitions

  • the present invention relates to a communication system of the kind in which the intelligence wave is transmitted as a time phase modulation of a predetermined change in a, characteristic of an electrical waveform in accordance with the instantaneous amplitude of said intelligence wave.
  • the predetermined change in a characteristic of the electrical waveform may comprise a change in frequency or phase such as a phase reversal, or a change in amplitude, said change being preferably sudden.
  • the system becomes the more usual and commonly known system of the kind specified, namely a time phased pulse modulation communication system.
  • Known methods of demodulating time phased pulses comprise adding to the received train of time phased pulses, an unmodulated train of pulses (that is umnodulated as regards their times of occurrence) of the same repetition frequency as the time phased train and then producing from pairs of pulses, each pair comprising a pulse of the modulated train and a pulse of the unmodulated train, duration modulated pulses by means of a buildback circuit.
  • the duration modulated pulses will have one fixed edge, that is, the corresponding edge of each pulse will occur at constant intervals of time corresponding to the pulses of the unmodulated train.
  • the duration modulated pulses are then passed through a low pass filter which gives directly in its output the desired amplitude modulated intelligence or signal wave.
  • An object of the present invention is to provide improved and simplified demodulating arrangements in systems of the type hereinbefore specified.
  • a system of the kind hereinbefore specified has demodulating arrangements for producing duration modulated pulses under the control of the time-phased modulated wave comprising an electron discharge circuit arrangement so arranged that on the application of a high voltage thereto under the control of said predetermined change in the electrical waveform, the current through said electron discharge circuit changes from a first value to a second value and persists at said second value during the continuance of an intermediate voltage applied to said circuit arrangement, and when said intermediate voltage is removed, the current through said electron discharge circuit returns to said first value.
  • a communication system of the kind in which the intelligence wave is transmitted as a time-phase modulation of a train of electrical pulses has demodulating arrangements for producing duration modulated pulses from the time-phased pulses comprising an electron discharge circuit arrangement so arranged that on the application of a high voltage thereto under the control of said time-phased pulses, a change is effected in the current in said circuit arrangement from a first value to a second value and remains at said second value during the continuance of an intermedlate voltage applied to said circuit arrangement and when said intermediate voltage is removed said current returns to said first value.
  • the change in an electrical characteristic may be transformed in any known manner into an amplitude change, preferably a sudden amplitude change or a short sharp pulse and the derived amplitude modulation or pulse waveform may be applied to the electron discharge circuit.
  • the intermediate voltage may comprise a train of pulses of rectangular Waveform of suitable amplitude and havin a pulse repetition frequency equal to the repetition frequency of the said chan e in electrical characteristic or corresponding derived pulses and having a duration at least as long as the time modulation limit of the time-phase modulated wave.
  • the electron discharge circuit arrangement may take the form of a circuit, such as a multivibrator type of circuit, of Kipp relay which is capable of being triggered from one condition to another under the control of the applied voltages.
  • the invention is particularly applicable to a multi-channel pulse modulation system utilising distributors at the transmitting and receiving ends in which electrical pulses are employed for defining the respective channels by defining the portion of each cyclic period which is allotted to each channel, i. e. the channel period.
  • a distributor may take the form of a delay network, from points along which pulses having difierent delay times are applied to the demodulators of respective channels to bring the channels successively and cyclically into use.
  • channel period is then determined by the dura tion of the pulses applied to the input of the delay network.
  • the pulses obtained at the intermediate points along the delay network for the respective channels may be utilised as the intermediate pulses for application to the demodulation arrangements.
  • the application of pulses to the input terminals of the delay network will, of course, be synchronised with the channel selection pulses applied to a similar delay network or other distributor at the transmitter.
  • Figure 1 shows explanatory curves referred in the description.
  • Figure 2 shows diagrammatically the receiving end of a multi-channel communication system utilising time phased modulator pulses with circuit diagrams of build back arrangements er' bodying th invention respectively in channel l and channel 12.
  • curve a illustrates a multi-channel communication system in which the intelligence waves oi the channels are transmitted as timephased modulated pulses.
  • the system is illustrated as having six channels numbered 2' to 55 respectively.
  • the channels are brought successively and cyclically into operation by means of a distributor at the transmitter and a distributor at the receiver working in synchronism with each other. This synchronism between the two distributors is maintained by the transmission of synchronising pulses, as illustrated at s in Figure 1, from the transmitter to the receiver.
  • the distributors at the transmitter and receiver are preferably alike and may take the form, as described in the patent specification of co-pending British application No.
  • a delay network or artificial line which retards the passage of an electrical current propag ted therethrough and comprises a plurality of series connected cells made up or" electrical condensers and inductances, and preferably alike, each 01" which retards the current passed therethrough by predetermined preferably equal time intervals.
  • Such a distributor network or artificial line is indicated by numeral l in Figure 2. Pulses of distributor cyclic frequency are obtained from the master pulse generator represented by block 2 and are fed to the input terminals of the line at a constant repetition frequency and the pulses obtained at the various tapping points TPlTP6 on the network or line are then applied to bring the channels of a multi-channel system successively into use.
  • the master pulse generator 2 may comprise, for example, a multivibrator type of circuit well known in the art, and which may be stabilised as to frequency by the pulses from the output of the network or line 5, fed back through an amplifier or reshaping device indicated by block
  • the synchronising pulses S obtained from a synchronising pulse separator arrangement indicated by block 4 fed from the high frequency receiver and detector represented by block 5, are also applied to the master pulse generator to synchronise this latter to the transmitter distributor.
  • the input to the receiver 5 will be obtained from whatever transmission medium is used and may be a transmission line, wave guide or radio.
  • the output f cm the receiver is also applied in parallel to the channel equipments via respective diodes 5 which serve to isolate the respective channels from each other.
  • amplitude limiter device indicated by block 511 is provided between the receiver 5 and the channel demodulator-s for a purpose described hereinafter.
  • the apparatus represented by blocks i, 2, 3, l, 5 and E-a does not form part of the present invention and may take any suitable form. Hence no details are given herein.
  • pulses of rectangular waveform whose duration determines the channel period, that is the period of time during each distributor cyclic period when a channel is operative.
  • Such a wave may thus be used as the pulses of intermediate voltage for the purposes of the present invention.
  • Such a pulse of rectangular waveform is illustrated in curbe Figure l, for channel 2, and is repeated at a repetition frequency equal to the distributor cyclic frequency.
  • time phased pulses of the channels may occur between the limits t1 and t2 corresponding to the leading and trailing edges of the distributor or selector pulse.
  • the pulse or" only channel 3 is illustrated in curve I) Figure 1 but it will be understood that the selector pulses for the other channels occur successively throughout the distributor cycle as illustrated in curves 0 and c.
  • Figure 2 shows in channel l a inultivibrator type of build bacl circuit comprising two interconnected valves "i and S, the anode of 7 being coupled through a capacity to the control grid of valve 8 and the anode of 8 being coupled to the control grid of valve 7.
  • the control grid of one of 12 valves in the present case, the valve 8 is blessed negatively as illustrated by biassing the cathode positively with respect to earth potential by a bias battery 9 in the cathode circuit, so as normally to render the multivibrator insensitive. The same result may be obtained by a negative bias between the grid and earth potential.
  • the selector pulses of rectangular waveform curve b Figure l, of positive sign obtained from the distributor tapping point TPi as hereinbefore explained are applied, for example, to the grid iii of valve 8 so as to reduce the negative bias, so that the multivibrator comes near enough to the threshold of sensitivity as to be trigge ed over by the first channel pulse 0?? occurring after the leading edge of the selector pulse present on the grid as illustrated in curve 0 or d Fig. i, where the triggering voltage is represented by line TV.
  • the mutivibrator will remain in this second condition so long as the selector pulse persists, and at the end of the selector pulse t re circuit automatically triggers over to its original condition in which it remains on account of the negative grid bias of valve 3 until the next selector pulse and channel pulse occur.
  • the channel pulses are assumed to be negative and ase applied. on the grid oi valve 7. They could equally well be applied directly as positive pulses on the grid of valve 8 as in fact they are in the present illustrative case after amplification in. valve l.
  • Channel pulses of suitable sign may of course be app ed to either of the cathode circuits as will be well understood.
  • the negative bias on the grid of valve 8 is greater than the maximum amplitude of the amplified channel pulses so that the valve 8 remains insensitive until the selector pulse occurs.
  • the selector pulse applied on the grid of valve 8 is thus positive and has a sufiicient amplitude so that valve 8 responds to the amplified channel pulses from valve 1.
  • the amplitude limiter 5a renders the amplitude of the channel pulses applied to the multivibrator circuit 6 independent of the amplitude of the received pulses.
  • a limiter may be, for example, an electron discharge valve arranged to have a grid swing smaller than the minimum amplitude pulses applied to its grid.
  • the grid is negatively biassed and positive pulses are assumed applied thereto.
  • a high resistance is inserted in series with the grid in order to limit the grid voltage swing by the grid current.
  • the amplified-detector of the receiver 5 has a great sensitivity the amplitude of the channel pulses applied on the grid of the limiter will always have a greater amplitude than the grid swing, and the negative pulses taken from the anode circuit of the limiter valve (5a) will have a substantially constant amplitude.
  • the leading edge L coincides with the occurrence of the channel pulse P2 and the trailing edge T coincides with the trailing edge TI of the selector pulse SP2.
  • the pulses of train DNI, DN2 become duration modulated, and are passed through a low pass filter represented by block I2 to produce the original intelligence wave transmitted.
  • the output from I2 is fed to a translating device indicated as headphones I3.
  • Curve g shows the negative duration modulated pulses obtained for channel 2.
  • Fig. 2 is shown another multi vibrator circuit arrangement I4 and comprises a pentode valve I5 whose control grid is capacity coupled to the anode of valve I6 and the control grid of valve It is capacit coupled to the anode of valve I5.
  • the cathode of valve I5 is biassed positively by means of the resistance chain I1, is connected between H. T.+ and earth potential.
  • Positive selector pulses are shown as applied to the control grid of valve I5, but negative selector pulses could be applied across the resistance is in the cathode circuit of valve I5.
  • the channel modulated pulses may be applied to the control grid of valve I6.
  • Duration modulated pulses are produced in the anode circuit of valve I5 as described in connection with Figures 1 and 2. Duration modulated pulses may also be obtained from the screen grid I9 of valve I5 as shown in the arrangement in channel 6 and may be passed through a low pass filter 20 to obtain the intelligence wave.
  • pulses of rectangular waveform As the intermediate pulses, it has beenpointed out in specification of application No. 10,305/44 that the pulses become distorted as they travel along the delay line or network. This distortion consists in an increase in the duration of the pulse, the leading and trailing edges of the waveform becoming more inclined to the time axis as the pulse proceeds along the delay network, but the duration of the pulse above substantially its mean voltage is substantially constant.
  • a squaring or reshaping device such as an amplifier-limiter represented by block 2I may therefore be provided. Since positive pulses have been assumed as provided by the delay network I, the output pulses of positive sign may be obtained in the cathode circuit of the amplifier limiter 2
  • a distorted selector pulse SP3 is indicated by the broken lines M in channel 3 and a channel pulse N indicated as occurring at or towards the end of channel 2.
  • the channel duration is defined by the portion of the pulse above the mid-amplitude of the pulse SP3, and since the triggering voltage is represented by the line TV, it can be seen that if the amplitude of pulse N is made substantially half the amplitude of the selector pulse SP3, the pulse N of channel 2 can never operate the multivibrator circuit of channel 3 and interference between the channels is eliminated. similarly a pulse occurring at the beginning of channel A will be ineffective as regards channel 3.
  • a system for translating time displacement modulation signal pulses into output pulses whose width varies according to said displacement comprising, means for producing constant repetition rate control pulses in synchronism with the signal pulses in their unmodulated state, each of said control pulses having a width covering the entire range of displacement of the corresponding signal pulse, a tripping circuit having two levels of stability, means for biasing said circuit to maintain it at a first one of said stability levels, said bias having a value such that the combined amplitudes of a control pulse and signal pulse are required to produce tripping to the second stability level while the control pulse alone is s-ufilcient to maintain the circuit at said second level, means for applying the control pulses and the time displacement modulated signal pulses 3.
  • a system accore ng to claim 1, wherein said control pulses are substantially rectangular.
  • amp itities of a control pulse and sig nal pulse are rcauired to tripping to the second level while the control pulse alone is suificient to maintain the circuit at said second placement modulation to trip s- 1C1 circ es nd level at the time of application of a signal puse and to permii; retm'n to said first level at the nd of the corresponding control ulse, and means for de riving from said circuit variable wiclth output pulses.
  • each associated with a pin-- rality of signal pulses forming parts of separate channels and hzlVli'l" a time displacement with respect to their associated synchronizing pulse that varies accordin to the instantaneous value 5 of the intelligence to he nveyed comprising, o the control of said 0" pulses synchronized es and havin a of displacement -s, a plurality of a part of a sepatwo levels of stasaid circuits to stability levels, said bios haviLg a value such at the combined amplitudes of a control pulse and signal pulse 'ldzvt. iing to the second trol pulse alone is sufficient to at second level.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Radar Systems Or Details Thereof (AREA)
  • Channel Selection Circuits, Automatic Tuning Circuits (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
  • Superheterodyne Receivers (AREA)
US602805A 1944-05-26 1945-07-02 Multiplex time modulated electrical pulse demodulation system Expired - Lifetime US2510987A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB10309/44A GB587942A (en) 1944-05-26 1944-05-26 Improvements relating to demodulation arrangements in electrical pulse modulation communication systems

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US2510987A true US2510987A (en) 1950-06-13

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US602805A Expired - Lifetime US2510987A (en) 1944-05-26 1945-07-02 Multiplex time modulated electrical pulse demodulation system

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US (1) US2510987A (US06623731-20030923-C00012.png)
BE (1) BE476628A (US06623731-20030923-C00012.png)
DE (2) DE973189C (US06623731-20030923-C00012.png)
ES (1) ES176835A1 (US06623731-20030923-C00012.png)
FR (1) FR939301A (US06623731-20030923-C00012.png)
GB (1) GB587942A (US06623731-20030923-C00012.png)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2652453A (en) * 1950-03-17 1953-09-15 Bendix Aviat Corp Multichannel radio communication system
US2655648A (en) * 1948-12-31 1953-10-13 Rca Corp Radio navigation system
US2687473A (en) * 1950-04-13 1954-08-24 Remington Rand Inc Signal cycling device
US2771553A (en) * 1952-11-03 1956-11-20 Itt Multiplex demodulator
US2785227A (en) * 1951-03-10 1957-03-12 Cie Ind Des Telephones Method and device for modulation and demodulation for pulse-type telecommunication system
US2894127A (en) * 1954-10-26 1959-07-07 Collins Radio Co Pulse decoding means
US3072903A (en) * 1953-06-22 1963-01-08 Lab For Electronics Inc Signal switching apparatus

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2499844A (en) * 1947-01-16 1950-03-07 Philco Corp Receiver for pulse-position-modulation systems
BE513508A (US06623731-20030923-C00012.png) * 1947-10-21

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1918252A (en) * 1930-06-12 1933-07-18 Western Electric Co High speed telegraphy
US2199634A (en) * 1938-06-21 1940-05-07 Rca Corp Secret communication system
US2262838A (en) * 1937-11-19 1941-11-18 Int Standard Electric Corp Electric signaling system
US2266481A (en) * 1939-10-27 1941-12-16 Int Nickel Co Age hardenable, low expansion, nickel-iron-titanium alloy
US2379900A (en) * 1940-11-29 1945-07-10 Rca Corp Receiving system
US2391776A (en) * 1943-05-29 1945-12-25 Rca Corp Intelligence transmission system
US2392546A (en) * 1942-02-20 1946-01-08 Rca Corp Pulse modulation receiver
US2416330A (en) * 1944-08-07 1947-02-25 Standard Telephones Cables Ltd Multichannel receiving system

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB470495A (en) * 1935-11-14 1937-08-16 Alan Dower Blumlein Improvements in or relating to multiplex signalling systems
NL88393C (US06623731-20030923-C00012.png) * 1937-06-18
DE971784C (de) * 1942-12-01 1959-03-26 Telefunken Gmbh Schaltungsanordnung fuer eine Empfangs- oder Zwischenstation bei der wechselzeitigen Mehrfachuebertragung mittels phasenmodulierter Impulse

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1918252A (en) * 1930-06-12 1933-07-18 Western Electric Co High speed telegraphy
US2262838A (en) * 1937-11-19 1941-11-18 Int Standard Electric Corp Electric signaling system
US2199634A (en) * 1938-06-21 1940-05-07 Rca Corp Secret communication system
US2266481A (en) * 1939-10-27 1941-12-16 Int Nickel Co Age hardenable, low expansion, nickel-iron-titanium alloy
US2379900A (en) * 1940-11-29 1945-07-10 Rca Corp Receiving system
US2392546A (en) * 1942-02-20 1946-01-08 Rca Corp Pulse modulation receiver
US2391776A (en) * 1943-05-29 1945-12-25 Rca Corp Intelligence transmission system
US2416330A (en) * 1944-08-07 1947-02-25 Standard Telephones Cables Ltd Multichannel receiving system

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2655648A (en) * 1948-12-31 1953-10-13 Rca Corp Radio navigation system
US2652453A (en) * 1950-03-17 1953-09-15 Bendix Aviat Corp Multichannel radio communication system
US2687473A (en) * 1950-04-13 1954-08-24 Remington Rand Inc Signal cycling device
US2785227A (en) * 1951-03-10 1957-03-12 Cie Ind Des Telephones Method and device for modulation and demodulation for pulse-type telecommunication system
US2771553A (en) * 1952-11-03 1956-11-20 Itt Multiplex demodulator
US3072903A (en) * 1953-06-22 1963-01-08 Lab For Electronics Inc Signal switching apparatus
US2894127A (en) * 1954-10-26 1959-07-07 Collins Radio Co Pulse decoding means

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Publication number Publication date
DE914633C (de) 1954-07-05
BE476628A (US06623731-20030923-C00012.png)
ES176835A1 (es) 1947-03-16
GB587942A (en) 1947-05-09
DE973189C (de) 1959-12-17
FR939301A (fr) 1948-11-09

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