US2489268A - Electrical communication system - Google Patents

Electrical communication system Download PDF

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Publication number
US2489268A
US2489268A US476072A US47607243A US2489268A US 2489268 A US2489268 A US 2489268A US 476072 A US476072 A US 476072A US 47607243 A US47607243 A US 47607243A US 2489268 A US2489268 A US 2489268A
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United States
Prior art keywords
waves
amplitude
wave
modulating
frequency
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Expired - Lifetime
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US476072A
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English (en)
Inventor
Chatterjea Prafulla Kumar
Ambrose Dermot Min
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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
    • H04B—TRANSMISSION
    • H04B14/00—Transmission systems not characterised by the medium used for transmission
    • H04B14/02—Transmission systems not characterised by the medium used for transmission characterised by the use of pulse modulation

Definitions

  • the present' invention relates l to 1 electrical communication systemsA andaccor-dingf thereto.; ⁇ provides ⁇ r ⁇ a-l transmission ⁇ systemv in which the bandwidth of the tI'arisI-nittedfrequencies:is-mod;V ulatedin accordanceswith theamplitude ofthe intelligence for-sgnal wave -to be communicated; ⁇
  • The: resulting waveform may be transmittedf alongaline-or may be used.
  • tov modulate ⁇ a carrier.
  • Waver inknown manner: The modulated carrier.-. ⁇ may be transmitted in: any-known manner, for i example,V radio; cablei orf dielectric guides;L
  • This :emodulateds Waveformis .thenrpassed:throughv a .limiten circuitl in: such:.a;.way as 4tolmit the; amplitude offthega modulatedl Wave to; at ,.least that .voi 'the Lsmallest; amplitudesine waveproducedain: tha-modulation.;
  • the resulting Waveform may thus varyrfromfatz, sine.;wave innonez-casetora 50% pulse,;with acentain,..harmcnc, contentsthatis, the number. of harmonics of .the fundamental frequency; oftthezi. sine: Wave; depending; on the lmodulation;:depth.
  • This uWave .iorm..is;used..to..modulate x a.; carrier.r ⁇ wavef-andsince. thisgmodulation; variesxin ampli. tudei.between.two fixed. values, namelygzero.,l andg. the* ⁇ amplitude of: the :fundamental sine tvvave,V the;Y carrier :canibe :modulated 'to 100%. Without irisk. ofwover modulating.'y
  • Inrxone ⁇ suitable form of receiving arrangement - the modulated carrier.I isfsreceived. on a. receiver. which is capable ,oihandling-:thenecessary handL widthfandthe;detectedswave is limitedzin amplis-- tude'ifor noise reductionwand ⁇ passed through am. high passlter.
  • Thislterxis'so ⁇ designeollthate ⁇ therfundamental frequencyy .of the detectediiwavec ⁇ is L greatly attenuated while the harmonics ⁇ r are allowedV toV pass :freely:
  • These'fh'armonicsl may loefv eachy looked uponas auf carrier '(harmonic carv riers) l modulated in amplitude "by' the original; signal4 or ⁇ intelligenc'ef ⁇ wave:
  • the output 4 ⁇ o1"v the-zn, iilter ⁇ is passedx through'-A a rectifier ⁇ and then through: a' ilcvv.v pass .lter: whichI attenuates ⁇ the harmonici carrier frequencies but ,passes thef: intelligencefirequencies
  • Theselatterf are ample edasnecessary and.passed. tothe vworker trans-.ff
  • Fig, 2 showsthewaveform:atpoint,I I of Eig-.1;Y Fig. 3Jshowsth'e waveform at point.I3.of-Fig..1';.
  • Fig. '4 shows the waveform atpointl 5 ofligi 1 band transmitter. 15#4 In Fig.. 1 the. signalvoltage wave representing mon to'valves Viy andVav and thus across resi-st? ance '.IT will be, developed ,'tlfiesine .wave.from
  • Fig,V 5- is' ⁇ theschematic diagram of receiving... arrangements...fr ,cofoperation witna transmit-- l ter as in Fig. 1' or anyother modulated frequency *lated in. accordancelwitlith'e .Waveform imposed.,
  • the circuit diagram of a receiving arrangement is shown in Fig. 5.
  • the signal is primarily received by any known technique, care being taken that the circuits involved can handle the frequency bandwidths required which is limited by the modulation depth in the transmitter.
  • the signal, from the detector of the radio receiver at the points 'l and 8 which is shown in Fig. 3 is fed into a limiter circuit one type of which is shown consisting of V5 and Vs, which are diodes, and their associated circuits.
  • the principle of operation is exactly similar to the limiters in the transmitter (Fig. l) and V3 coincides with V5; V4 with V6; resistances I9 and 3
  • the purpose of this limiter is to reduce noise by limiting the noise components from the crests and troughs of the received pulses.
  • the output from the limiter V5 and Vc is now passed through condenser to a high pass filter 4l.
  • This filter is so designed as regards its cut off frequency that it heavily attenuates the fundamental frequency of the pulse train applied to it while allowing free passage to the harmonics in the pulse.
  • the wave-form at the out put terminals 9 and i0 of the filter is thus a compleX carrier composed of the harmonics contained in the pulse and which bear the initial intelligence voltage Wave in the form of an amplitude modulation.
  • the output from the high pass lter il is fed through a diode Vv on resistance de to perform the necessary detection of this harmonic carrier and thence Via terminals l2 and lli to a low pass filter 5l.
  • the cut off frequency is at the same frequency or slightly lower than that of the fundamental frequency of the wave-form at points l and 8 in ig. 5 and which is shown in Fig. 3.
  • at points I3 and lll is the voltage corresponding to the intelligence or signal wave which is transmitted and may be connected to a speaker or some such appliance for audibility, or other work device.
  • this system gives a greater signal noise ratio due to the limiting circuits in the receiver and also to the filters which allow only part of the noise spectrum t0 pass.
  • a greater modulation depth in the radio frequency carrier may be obtained than with amplitude modulation systems since the amplitude of the pulses is constant. There is also the greater peak power transmission for a given valve than is normally associated with forms of pulse transmission.
  • a damped oscillatory circuit may be employed and the received detected signals applied to shock excite the oscillatory circuit.
  • the amplitude of the initial cycle of the oscillation produced depends upon the rate of change of strength of the exciting current with time, and thus since the slope .of the edges of the This latter is so arranged that .y
  • the detected received wave-form or pulses be applied to shock excite the damped oscillatory circuit, preferably tuned to the pulse repetition frequency, or the frequency of the detected wave-form, the output of said circuit will follow the amplitude variations of the initial signal wave.
  • the output of the oscillatory circuit may then be applied directly to a translating device or other work device.
  • means for producing electrical intelligence waves of varying amplitudes means for modulating less than the amplitude of a sine wave whose frequency is higher than the highest modulation frequency component of the intelligence wave to be communicated, circuit means for limiting the amplitude of said modulated wave to at least that of the smallest amplitude sine wave produced in the modulation, and means for modulating a carrier wave in accordance with the wave-form produced by said circuit means.
  • means for producing electrical intelligence waves of Varying amplitudes means for producing a wave-form Varying from pure sine wave to a pulse with a predetermined harmonic content, and means for modulating said Wave-form in accordance with said amplitudes, the number of harmonics of the fundamental frequency of said sine wave depending on the depth of the modulation.
  • means for producing electrical intelligence waves of varying amplitudes means for modulating less than 100% the amplitude of a sine wave whose frequency is higher than the highest modulation frequency component of the intelligence wave to be communicated, circuit means for limiting the amplitude of said modulated wave to at least that of the smallest amplitude sine Wave produced in the modulation, means for modulating a carrier wave in accordance with the wave-form produced by said circuit means, whereby this modulation varies in amplitude between the two fixed values of Zero and the amplitude of the fundamental sine wave.
  • An electrical communication system for transmitting and receiving intelligence comprising means for generating signal Waves having a predetermined fundamental frequency, means for varying the time rate of change of said waves between two amplitude levels in accordance With the intelligence to be transmitted while maintaining the maximum amplitude and the fundamental frequency of said waves substantially constant, means for transmitting said distorted waves, means for receiving said distorted Waves and means for demfodulating said waves.
  • An electrical communication system for transmitting and receiving intelligence waves comprising means for generating signal waves having a predetermined frequency, means for varying the time rate of change of said waves between two fixed amplitude levels corresponding to the lowest amplitude intelligence waves, in accordance with the intelligence to be transmitted, means for generating a carrier wave, means for modulating said carrier waves by said distorted waves, means for transmitting said modulated carrier waves, means for receiving said modulated carrier waves, means for detecting said modulated carrier Wave and means for demodulating the output signals of said detecting means.
  • An electrical communication system for transmitting and receiving intelligence comprising a source of electrical waves whose amplitude vary with the intelligence being transmitted, a source of carrier frequency sine waves, means for amplitude modulating said carrier waves with said electrical waves to derive complex waves, means for varying the harmonic content of said complex waves vin accordance with said amplitudes While leaving the fundamentals and amplitude of said complex waves unmodulated comprising means for varying the time rate of change of said complex waves to change between two amplitude levels in accordance with said amplitudes, means for transmitting the modulated complex waves, means for receiving said modulated complex waves, means for detecting said modulated complex waves, and means for attenuating the fundamental frequency of the detected wave while freely passing the harmonics, means for deriving said intelligence from said harmonics.
  • a source of modulating waves a source of carrier waves, means for amplitude modulating said carrier waves with said modulating waves to obtain modulated waves, means for limiting said modulated waves to the amplitude corresponding to the lowest amplitude modulating wave to derive waves harmonically related to the frequency of the lowest amplitude modulating waves and amplitude modulated in accordance with the modulating waves, and unmodulated waves at the frequency of the lowest amplitude modulating waves, and means for transmitting said derived and said unmodulated waves.
  • said modulating waves comprise sine waves and said means for limiting comprises means for limiting the amplitude of the modulated waves to the amplitude of the lowest amplitude sine waves.
  • a receiving system for carrier waves amplitude modulated in accordance with a source of modulating waves said modulated waves comprising waves harmonically related to the frequency of the lowest amplitude modulating waves and amplitude modulated in accordance with the modulating waves, and unmodulated waves at the frequency of the lowest amplitude modulating Waves, comprising means for receiving said modulated carrier waves, a high pass i'llter, means for applying said received waves to said filter to attenuate the unmodulated waves while passing said waves harmonically related to the frequency of the lowest amplitude modulating waves, means for amplitude detecting the passed harmonically related waves, a low pass filter, means for applying said amplitude detected waves to said 10W pass filter to derive said modulating waves.
  • An electrical communication system for transmitting and receiving intelligence comprising a source of modulating waves, a source of carrier frequency Waves, means for amplitude modulating said carrier waves with said modulating waves to obtain modulated waves, means for limiting said modulated waves to the amplitude corresponding to the lowest amplitude modulating waves to derive waves harmonically related to the frequency of the lowest amplitude modulating waves and amplitude modulated in accordance with the modulating waves, and unmodulated waves at the frequency of the lowest amplitude modulating waves, means for transmitting said derived and unmodulated Waves, means for receiving said transmitted waves, means for separating said unmodulated Waves from said waves harmonically related to the frequency of the lowest amplitude modulating Waves, means for amplitude detecting said harmonically related waves after separation, and means for processing said amplitude detected waves to derive said modulating waves.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
  • Near-Field Transmission Systems (AREA)
US476072A 1942-03-13 1943-02-16 Electrical communication system Expired - Lifetime US2489268A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB3374/42A GB556001A (en) 1942-03-13 1942-03-13 Improvements relating to electrical communication systems

Publications (1)

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US2489268A true US2489268A (en) 1949-11-29

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US476072A Expired - Lifetime US2489268A (en) 1942-03-13 1943-02-16 Electrical communication system

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US (1) US2489268A (th)
BE (1) BE476184A (th)
FR (1) FR939087A (th)
GB (1) GB556001A (th)
NL (2) NL136059B (th)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2564769A (en) * 1949-10-25 1951-08-21 Rca Corp Translating circuit
US2929924A (en) * 1955-02-21 1960-03-22 Westinghouse Electric Corp Radiation suppression circuit
US2956153A (en) * 1957-11-08 1960-10-11 Sylvania Electric Prod Electrical noise reduction techniques

Citations (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1564627A (en) * 1920-03-31 1925-12-08 Rca Corp Wireless telegraph and telephone transmission
US1584327A (en) * 1926-05-11 Electric-wave transmission system
US1655543A (en) * 1924-04-18 1928-01-10 Western Electric Co Transmission system
US1678163A (en) * 1923-12-29 1928-07-24 Western Electric Co Modulation
US1699570A (en) * 1927-09-23 1929-01-22 American Telephone & Telegraph Carrier suppression modulation
US1876793A (en) * 1929-10-22 1932-09-13 Frank C Talmadge Radio circuit
US1911253A (en) * 1926-09-13 1933-05-30 Clinton Dorothy Radio receiving apparatus
US1971383A (en) * 1932-03-11 1934-08-28 Telefunken Gmbh Transmitter
US2061734A (en) * 1934-09-29 1936-11-24 Rca Corp Signaling system
US2085011A (en) * 1932-03-22 1937-06-29 Rca Corp Modulated carrier wave signaling system
US2205359A (en) * 1938-06-24 1940-06-18 Hygrade Sylvania Corp Superheterodyne receiver
US2230243A (en) * 1938-06-28 1941-02-04 Philip M Haffcke Signal selection by amplitude discrimination
US2257282A (en) * 1939-04-27 1941-09-30 Rca Corp Frequency modulation of signals
US2266401A (en) * 1937-06-18 1941-12-16 Int Standard Electric Corp Signaling system
US2279659A (en) * 1937-04-13 1942-04-14 Rca Corp Frequency modulator
US2303493A (en) * 1940-05-17 1942-12-01 Rca Corp Diversity signaling system
US2404306A (en) * 1941-04-01 1946-07-16 Rca Corp Communication system
US2416329A (en) * 1942-08-24 1947-02-25 Standard Telephones Cables Ltd Push-pull modulation system

Patent Citations (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1584327A (en) * 1926-05-11 Electric-wave transmission system
US1564627A (en) * 1920-03-31 1925-12-08 Rca Corp Wireless telegraph and telephone transmission
US1678163A (en) * 1923-12-29 1928-07-24 Western Electric Co Modulation
US1655543A (en) * 1924-04-18 1928-01-10 Western Electric Co Transmission system
US1911253A (en) * 1926-09-13 1933-05-30 Clinton Dorothy Radio receiving apparatus
US1699570A (en) * 1927-09-23 1929-01-22 American Telephone & Telegraph Carrier suppression modulation
US1876793A (en) * 1929-10-22 1932-09-13 Frank C Talmadge Radio circuit
US1971383A (en) * 1932-03-11 1934-08-28 Telefunken Gmbh Transmitter
US2085011A (en) * 1932-03-22 1937-06-29 Rca Corp Modulated carrier wave signaling system
US2061734A (en) * 1934-09-29 1936-11-24 Rca Corp Signaling system
US2279659A (en) * 1937-04-13 1942-04-14 Rca Corp Frequency modulator
US2266401A (en) * 1937-06-18 1941-12-16 Int Standard Electric Corp Signaling system
US2205359A (en) * 1938-06-24 1940-06-18 Hygrade Sylvania Corp Superheterodyne receiver
US2230243A (en) * 1938-06-28 1941-02-04 Philip M Haffcke Signal selection by amplitude discrimination
US2257282A (en) * 1939-04-27 1941-09-30 Rca Corp Frequency modulation of signals
US2303493A (en) * 1940-05-17 1942-12-01 Rca Corp Diversity signaling system
US2404306A (en) * 1941-04-01 1946-07-16 Rca Corp Communication system
US2416329A (en) * 1942-08-24 1947-02-25 Standard Telephones Cables Ltd Push-pull modulation system

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2564769A (en) * 1949-10-25 1951-08-21 Rca Corp Translating circuit
US2929924A (en) * 1955-02-21 1960-03-22 Westinghouse Electric Corp Radiation suppression circuit
US2956153A (en) * 1957-11-08 1960-10-11 Sylvania Electric Prod Electrical noise reduction techniques

Also Published As

Publication number Publication date
NL136059B (th)
NL67408C (th)
BE476184A (th)
FR939087A (fr) 1948-11-03
GB556001A (en) 1943-09-15

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