US2298409A - Multiplexing - Google Patents

Multiplexing Download PDF

Info

Publication number
US2298409A
US2298409A US341285A US34128540A US2298409A US 2298409 A US2298409 A US 2298409A US 341285 A US341285 A US 341285A US 34128540 A US34128540 A US 34128540A US 2298409 A US2298409 A US 2298409A
Authority
US
United States
Prior art keywords
frequency
sub
carrier
modulated
carriers
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US341285A
Other languages
English (en)
Inventor
Harold O Peterson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
RCA Corp
Original Assignee
RCA Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by RCA Corp filed Critical RCA Corp
Priority to US341285A priority Critical patent/US2298409A/en
Priority to GB7756/41A priority patent/GB550193A/en
Application granted granted Critical
Publication of US2298409A publication Critical patent/US2298409A/en
Priority to CH270709D priority patent/CH270709A/de
Priority to FR989228D priority patent/FR989228A/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J1/00—Frequency-division multiplex systems
    • H04J1/20—Frequency-division multiplex systems in which at least one carrier is angle-modulated
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B14/00—Transmission systems not characterised by the medium used for transmission
    • H04B14/002—Transmission systems not characterised by the medium used for transmission characterised by the use of a carrier modulation
    • H04B14/006—Angle modulation

Definitions

  • This invention relates to multiplex signaling.
  • An object of the invention is to provide an improved frequency modulation m'ultiplex system especially useful for high quality broadcasting, facsimile, and tone or code signaling.
  • Another general object is to provide a multiplex circuit especially adapted for multiplexing a plurality of high quality broadcasting channels upon a radio relay circuit.
  • frequency modulation is applied to a transmitter capable of handling a band width of, for example, eight megacycles for ten high quality channels. With such a radiocircuit modulation frequencies up'to about three megacycles may readily be accommodated.
  • the band of possible modulating frequencies is divided into ten parts to accommodate frequency modulation at ten different sub-carrier frequencies.
  • Each of these sub-carrier frequencies is in turn frequency modulated by the high quality broadcast program material.
  • each subcarrier is frequency modulated with audio frequencies between about 30 cycles and inc. Since the noise which results upon demodulation of one of these sub-carrier channels will vary in proportion to audio frequency, Dre-emphasis and de-emphasis may be used in the same manner as is now used on, for example, the sound channel of the Empire State television station.
  • ten channels can I be set up as follows:
  • each of the sub-carriers would in turn be frequency modulated by an amount depending upon the band widths of the various channels as indicated above.
  • the maximum deviation of each sub-carrier may be 0.3 times its corresponding band width.
  • equal. sub-carrier band widths may be assigned to each channel, but
  • each sub-carrier should be made Fre- Deviation of Channel quency main carrier Channel number b5513 or by each carrier carrier Ki eta Kiloci/du Kitocycies' 150 125 107 so 176 150 60 225 193 50 275 236 60 325 279 50 376 822 60 425 364 v 50 476 407 50 525 450 60 676 492
  • each sub-carrier may be frequency modulated by the program material a maximum deviation of 15 1:. c.
  • phase modulation may be employed to advantage.
  • a signal to'random noise ratio of about 65 db. for a signaling channel employing band pass filters 100 cycles wide may be obtained in such a radio link.
  • Figures land 2 illustrate some of the principles involved in the noise characteristics of a frequency 'modulated signal.
  • Figure 3 shows a transmitter in which the main carrier frequency of the transmitter is frequency modulated by an equal amount by each of several sub-carriers. These sub-carriers are in turn frequency modulated by various deviations, said deviations increasing proportional to the sub-carrier frequencies; The object is to produce a system in whichthe signal-to-noise ratio will be equal in each of the various channels.
  • Figure 4 is shown another arrangement whereby the same objective is accomplished. In this case the main carrier frequency is frequency modulated by each of several sub-carriers in an amount which increases proportional to the sub-carrier frequen- Each sub-carrier frequency is in turn modulated by a fixed amount of deviation.
  • Figure 5 shows a receiving'system that could be used for receiving this type of multiplex signal.
  • Figures 6 and 7 illustrate terminals involving some of the points in greater detail. 1
  • the frequencies indicated are merely for the purpose of illustration.
  • Figures 8 and 9 show in block diagram form, arrangements of apparatus for carput varies over the frequency band and is proportional to the demodulated output frequencies.
  • Transmitter l8 includes a frequency modulator so that the carrier frequency may be modulated by the voltage developed in load circuit resistor It. For instance, the carrier frequency of transmitter It may be frequency modulated over a range of plus or minus 1000 k. c. (1000 k. c. deviation). This frequency modulation of the main transmitter l8 may occur at various sub-carrier frequencies. These sub-carrier frequencies are generated in units 6, I, 8, 9 and I0, each of which is in turn modulated by the signal it is desired to transmit, thus various types of program material may,for example, be introduced through input circuits I, 2, 3, 4 and 5.
  • the various sub-carrier frequencies ar impressed on the grids of vacuum tubes II, l2, l3, l4 and I5, all of which feed output into the modulator of transmitter l8.
  • the various sub-carriers chosen are 120 k. c., 172 k. c., 240 k. c., 335 k. c. and-470 k. 0.
  • Transmitter I8 is frequency modulated an equal amount by each of these sub-carrier frequencies.
  • each of these sub-carrier frequencies may impress 10 volts upon the grids of tubes II, l2, l3, l4 and I5.
  • the 120 k. c. sub-carrier will appear to have a better signal-to-noise ratio in the receiver output than will the 470 k. c. sub-carrier.
  • Another principle in frequency modulation is that the signal-to-noise ratio is proportional to the ratio of frequency deviation to modulation frequency; therefore, the overall signal-to-noise ratio can be equalized by using more deviation on the higher sub-carrier frequencies.
  • each of the sub-carrier generators 26, 21, 28, 29 and 30 are modulated by equal amounts.
  • the various program channels 2l,'22, 23, 24 and 25 are caused to frequencymodulate the various sub-carriers each by a deviation amounting to 25 k.
  • the main transmitter 38 is frequency modulated by all of the sub-carriers through vacuum tubes 3
  • the higher sub-carrier frequencies are caused tomodulated an equal amount by each of several 1 r so 43 to produce an intermediate frequency which is passed through selectorcircuit 46, amplifier 41, limiter 43, and frequency modulation discriminator anddetector 43.
  • selectorcircuit 46 amplifier 41, limiter 43, and frequency modulation discriminator anddetector 43.
  • the signal appears in the form of the various frequency modulated sub-carriers.
  • One of the sub-carrier frequencies is selected by each of the selector circuits 50, I5, 60, 83 and 10 which are followed by amplifiers SI, 56, ll. 43 and II.
  • the signal passes into limiters 52, I1, 62, 61 and 12 which feed discriminator-detector circuits'53, 53, 63, i8 and 13 the outputs of which are represented at 34, 59, 84, 39 and 14.
  • the original signals are reproduced in these output circuits.
  • the inputs in the-various channels may be pre-emphasized so as to impress more frequency deviation upon the subcarrier generators for the hi her signal frequencies.
  • the original balance may then be taken care of by de-emphasis circuits in the various receiver outputs of Figure 5.
  • the waves may be demodulated and retransmitted via the ultra short waverelay system described above to New York city, Conversely, a plurality of messages may be sent from New York city by way of the-relay system herein described to Rocky Point, Long Island, and there converted and demodulated for retransmission over long distance circuits on wave lengths above 15 meters to distant points.
  • Figure 6 illustrates the terminal at a receivingstation such as Riverhead, Long Island
  • Figure 7 illustrates the New York terminal for the signals coming via u-Jt-f radio relay from Riverhead.
  • Figure 6 could serve to illustrate the New York-terminal for signals outgoing to control a transmitting station such as Rocky Point, Long Island
  • Figure '7 with slight modifications could represent the terminal at the transmitting station.
  • These antennas may be of a directive type such as the fishbone or the rhombic antenna and they may be designed for receiving on different frequencies and from different directions. Also, each may actually be in the form of three antennas used ina diversity receiving system.
  • 8a, 9a, ia, iia, Ila, i3a and Ma represent receivers for the point-to-point frequencies between approximately 3 mc. and 30 me.
  • Cia may be tuned to a signal from London, receiver #911 to a signal from Italy, and receiver #iila to a signal from San Francisco.
  • the outputs of these three receivers pass through bandpass filters ia, [6a andi'ia into a frequency modulated sub-carrier generator 2ia in which they are caused to frequency modulate a source of 100 k. c, sub-carrier.
  • a maximum deviation of k. c. is indicated for the sub-carrier generator 2ia. It would be advisable to have higher deviation on the higher tone frequencies so that the overall signal-tonoise ratio would be the same on each channel. Thus, the deviation caused by the 765 cycle tone would be greater than the deviation'caused by the 425 cycle tone by a factor of 765 divided by As illustrated, antenna 4a and receiver iia re- .ceive a broadcast programwhich may include voice and music. This material is caused to frequency modulate sub-carrier generator 22a.
  • Antenna 5a and receiver l2a receives another telegraph circuit which is passed through bandpass filter iBa to frequency modulated sub-carrier generator 23a.
  • Receivers l3a and a are shown to be receiving frequency shift facsimile signals, one of them being a tone of 3000 cycles with a deviation of 800 cycles and the other being a tone of 5000 cycles with a deviation of 1300 cycles. These are passed through band filters Ilia and 2011 respectively and together with the telegraph signal from filter i8a frequency modu-' late the sub-carrier generator 23a.
  • the frequency modulated sub-carriers from generators Zia, 22a and 2311 are caused to frequency modulate a uh transmitter 24a which feeds through transmission line 25a to antenna 2611.
  • 200 k. c. sub-carrier is greater than that on the 100 k. c. sub-carrier and the deviation on the 300 k. c. carrier is still greater.
  • the system might, as a matter of fact, be considered a phase modulation system since in phase modulation the frequency deviation is proportional to the modulation frequency.
  • the 500 me. frequency modulated or phase modulated carrier is received on antenna 21b and conducted through transmission line 28b to a selective circuit 29b from which it goes to a converter 30b where it is combined with the frequency from a local oscillator 3ib.
  • the intermediate frequency is selected in circuit 32b, amplified and'limited in circuit 33b, and demodulated in the discriminator and detector circuit llb.
  • 34b we have the original sub-carrier frequencies which are selected by circuits 35b, 36b and 31b, amplified by 38b, 39b andlilb, limited by limiters lib, 42b and 43b, and demodulated by discriminator-detector circuits b, llb and b.
  • FIG. 8 we have tone generators ic, 2c and 30 which are modulated through keying devices 40, 5c and to feeding bandpass filters lo, and 9c.
  • the outputs of these bandpass filters are combined to operate a phase modulator iiic wherein the carrier from oscillator lie is phase modulated in accordance with the various tones coming through filters 1c, 8c and 9c.
  • the phase modulated carrier coming out of I00 is applied to the input of a series of amplifier-multiplier stages He in the manner well known to the transmitter art.
  • the output of amplifier-multiplier i2c passes if frequency increases the current in detector A' decreases whilst the current in detector B increases and if the frequency decreases the re-' verse is true.
  • Typical arrangements of this nature for phase modulation and for frequency modulation reception are more specifically described in Seeley Patent 2,121,103 and Crosby Patents 2,071,113 and 2,060,611. 7
  • the output of detector unit 220 is in the form of the original tone frequencies which may be separated off in bandpass filters 23c, 24c and 250 which connect to utilization circuits 26c, 21c and 280.
  • the coupling or the amplification of the signal may be varied so as to produce the desired swing in the sub-carrier frequency.
  • the output of the modulated sub-carrier generators may be limited to the constant value often volts or, more simply, by suitable taps on transformers or resistors the output may be adjusted to the desired constant voltage.
  • the signal input may be varied or the amplification thereof may be varied so as to produce the desired limit of frequency modulation.
  • the output of the respective sub-carrier generators and v a converter I35 also supplied from an oscillation generator I controlled by crystal I I5 or by any other suitable controlling element such as a resonant line.
  • the variabl frequency beat is filtered out and amplified in the amplifier H6.
  • the output of amplifier II6, therefore, represents a true frequency modulated sub-carrier wave which in turn is fed into a further converter I26 supplied with still higher frequency waves from high frequency oscillation generator I25.
  • the second beating or heterodyning process occurring in I26 produces upper and lower side bands, the upper one of which representing a true frequency modulated wave is fed throughhigh pass filter 121 and transmission line no to amplifier and/or frequency multiplier and/or limiter I3I, in turn feeding antenna I33 through transmission line I32.
  • the lower side bands resulting from the detection process in detector I28 are fed to a low pass filter I 28 which in turn supplies amplifier and automatic frequency control ling or discriminating circuits I29 of the type described, for example, in Seeley Patent 2,121,103.
  • the frequency controlling voltages arising across the output of discriminator circuit I29 are fed through lines I22, switch I23 and transmission lines I24 to the high-frequency oscillation generator I25 to vary the frequency thereof in such transmission line I20 into resistor II8 to vary modulators may be limited and by means of transformers or other adjustable couplings the desired voltage may then betaken. off for modulation of the main radio frequency carrier.
  • variable frequency beat from amplifier IIG may be fed to a similar frequency discriminating circuit or automatic frequency controlling circuit II'I for-automatically frequency controlling the oscillation generator II3 to bring the beat frequency of the sub-carrier appearing in the output circuit of amplifier II5 back to the desired sub-carrier frequency channel.
  • all of the automatic frequency controlling systems may be used together or switches I23 and I I9 may be opened, nullifying the A. F. 0. action of circuit I29.
  • switch I23 may be kept closed, switch 9 open and also switch I40 may be left open, in which event only the A. F. C. system I29 will be operative.
  • I26 may represent a. high frequency oscillation generator which is directly frequency modulated from the sub-carrier waves coming from 6.
  • filters I28 and I2! would, be identical, each passing the same band of frequencies.
  • Apparatus I25 would represent apparatus for frequency controlling or varying the frequency modulated oscillator I26.
  • Circuit 200 represents a discriminator circuit of the type described in the Seeley patent referred to above. This circuit is designed to operate with the entire band of sub-carrier frequencies. With switch 202 closed, automatic frequency controlling voltages are applied 'to the frequency variable oscillation generators 6 to I0 inclusive in such a direction as to make the entire band of sub-carrier frequencies stay within its assigned channel.
  • part of the output of the transmitting system is fed through lines I to a converter beat frequency amplifier and frequency discriminating circuit 200.
  • the converter fill is also supplied with oscillations from a crystal or other constant frequency oscillation generator 208.
  • the automatic frequency controlling voltages arising in transmission line fill areused to automatically frequency control the frequency modulated oscillator or generator It.
  • the frequency controlling voltages arising across transmission line Iii may be fed through wires M2 and switch 2 to give a supplemental con-. trol on the whole group of sub-carrier frequency generators through the transmission line I" in addition to the control given by'apparatus I".
  • switch 202 may be left open and switch 2 closed. r, switch ill may be left open and switch 202 closed. Or, both switches may be closed, as found desirable.
  • the systems of either Figures 11 or 12 for automatically frequency controlling the transmitting end of the signaling system may be applied also when the sub-carrier generators are phase modulated and the main carrier II or I28 are also phase modulated or when the sub-carriers are frequency modulated and the main carrier phase modulated, or when the sub-carrier frequencies are phase-modulated and the main carrier fre-' quency modulated, or when the sub-carrier frequencies are phase modulated and the main carrier phase modulated, or when the sub-carrier frequencies are amplitude modulated and the cessively higher mean frequency, means for modulating each of the sub-carrier waves generated with a different signal, the sub-carrier waves of higher frequencies being modulated to a greater degree than the sub-carrier waves of lower frequencies, means .for combining the modulated sub-carrier waves, and means for utilizing the combined sub-carrier waves to modulate a main high frequency carrier wave whereby the signal-to-noise ratio in each signal channel is maintained approximately equal.
  • a signaling system comprising means for generating a series of sub-carrier waves of different sub-carrier frequencies, means for angular velocity modulating each of the sub-carriers with a different signal, the sub-carriers of successively higher frequency being angular velocity modulated in successively higher degrees, means for combining the angular velocity modulated subcarriers, and means for utilizing the combined sub-carriers to angular velocity modulate another carrier of a frequency higher than any of the modulated sub-carriers whereby each signal channel has approximately the same signal-tonoise ratio.
  • means for generating a series of sub-carriers of the same amplitude but of successively higher frequency means for angular velocity modulating each of the sub-carriers with a different signal, the degree of angular velocity modulation increasing in direct proportion to the frequency of the sub-carrier, means for combining the angular velocity modulated sub-carriers, and means for angular velocity 2,sos,4oa
  • a plurality of signal sources a plurality of sub-carrier generators, the channel width assigned to each sub-carrier generator varying in direct proportion to the frequency of the sub-carrier, means for angular velocity modulating each of the sub-carriers in accordance with'a different signal so as to cause the sub-carrier to fully occupy its assigned channel, combining the modulated sub-carriers and utilizing the combined sub-carriers to angular velocity modulate a carrier of a frequency higher than any of the modulated sub-carriers.
  • means to generate a series of sub-carrier waves of successively higher frequency means to angular velocity modulate each of the sub-carriers the same amount, means for adjusting the amplitudes of the modulated sub-carriers to successively higher values in accordance with the frequency of the sub-carriers,
  • means for generating a main carrier wave means for generating a series of sub-carriers, means for modulating the frequency of the main carrier an equal amount by each of the several sub-carriers, and means for frequency modulating the sub-carriers in direct proportion to their sub-carrier frequencies.
  • means for generating a main carrier frequency means for generating several sub-carriers, and means for modulating the main carrier by the sub-carriers an amount which increases in proportion to the frequency of the sub-carrier modulating the main carrier.
  • means for generating a series of sub-carriers means for generating a main carrier, means for angular velocity modulating the sub-carriers by amounts which are proportional to the square root of the subcarrier frequencies, and means for modulating the main carrier by amounts which are proportional to the square root of the sub-carrier frequencies.
  • a multiplex system a plurality of subcarrier generators, means for angular velocity modulating each of the sub-carrier generators with a different signal, means for combining the modulated sub-carriers, means for generating a main high frequency carrier, and means for angular velocity modulating the main carrier with the combined sub-carriers, the modulation adjustment being such that the product of the deviation of each sub-carrier and the deviation of the main carrier produced thereby increases in proportion to the sub-carrier frequency.
  • means for generating a series of alternating current voltage waves of successively higher frequency means for impressing a different signal on each of said waves
  • means for generating a series of relatively low frequency alternating waves means for generating a high frequency carrier wave, the relatively low frequency waves being of different frequencies and having impressed thereon different signals, and means for modulating the high frequency carrier wave with said relatively low frequency waves by amounts which are proportional to the square root of the ing waves, means for generating a high frequency carrier wave, the relatively low frequency waves being of different frequencies and having impressed thereon different signals, and means for angular velocity modulating the high frequency carrier wave with said relatively low frequency waves by amounts which are proportional to the square root of the frequencies of said relatively low frequency signal carrying waves.
  • means for generating a series of relatively low frequency alternating waves means for generating a high frequency carrier wave, the relatively low frequency waves being of difierent frequencies and having impressed thereon different signals, and means for frequency modulating the high'frequency carrier wave with said relatively low frequency waves by amounts which are proportional to the square root of the frequencies of said relatively low frequency signal carrying waves.
  • a multiplex system comprising means .for generating a series of sub-carrier radio frequencies of successively higher mean frequency, means for so modulating each of the sub-carriers generated with a different signal that the higher sub-carrier frequencies are modulated to a greater degree than the low sub-carrier frequencies, means for combining the modulated sub-carrier frequencies, and means for utilizing the combined sub-carriers to modulate an ultra high frequency carrier wave.
  • means for generating a series of sub-carriers of the same amplitude but of successively higher frequency means for means for adjusting the amplitudes of the modulated sub-carriers to successively higher values in accordance with-the frequency of the sub-carriers, means to combine the modulated sub-carriers, and means to utilize the combined carriers to angular velocity modulate a main high frequency carrier.
  • means for generating a series of alternating waves of successively higher frequency means for generating a series of alternating waves of successively higher frequency, -means for modulating each of the waves with a different signal, and means 1 for so utilizing the modulated waves to frequency modulate a main high frequency carrier that the degree of modulation produced in the main carrier increases with the modulated waves of successively higher frequency.
  • means for generating a main carrier frequency means for generating several sub-carriers, and means for frequency modulating the main carrier an amount which increases in proportion to the frequency of the sub-carrier modulating the main carrier.
  • means for generating a series of sub-carriers means for generatfrequency modulating each of the sub-carriers with a diflerent signal, the degree of frequency modulation increasing in direct proportion to the frequency of the sub-carrier, means for combining the frequency modulated sub-carriers,
  • a plurality of signal sources a plurality of sub-carrier generators, the channel width assigned to each sub-carrier generator varying in direct proportion to the frequency of the sub-carrier, means for angular velocity modulating each of the sub-carriers in accordance with a different signal so as to cause the sub-carrier to fully occupy its assigned channel, means for combining the modulated subcarriers and utilizing the combined sub-carriers to modulate in frequency an ultra high frequency carrier and means for transmitting said modulated ultra high frequency wave.
  • means to generate a series of sub-carrier waves of successively higher frequency means to modulate each of the ing a main carrier, means for modulating in frequency the sub-carriers by amounts which are proportionalto the square root of the sub-carrier frequencies, and means for modulating the main carrier by amounts which are proportional to the square root of the sub-carrier frequencies.
  • means for generating a series of sub-carriers of successively higher frequency means for modulating each of the subcarriers with a different signal, and means for so utilizing the modulated sub-carriers to frequency modulate a main carrier that the degree of frequency modulation produced in the main carrier increases with the successively higher sub-carrier frequencies.
  • means for generating a main ultra high frequency carrier wave means for generating a series of low frequency sub-carriers, means for-modulating the frequency of the main carrier an equal amount by each of the several sub-carriers, and means for 'fregenerator being assigned to each signaling chan-- nel, means for angular velocity modulating the waves. generated by said sub-carrier generators with different signals, means combining the modulated sub-carrier waves, a high frequency carrier generator, and means for angular velocity modulating the carrier wave generated.
  • the deviation of the generated waves being adjusted so that for each channel the product of the deviation produced in a sub-carrier wave and of the deviation of the main carrier by the sub-carrier of said given channel increases in proportion to the sub-carrier frequency.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Transmitters (AREA)
  • Selective Calling Equipment (AREA)
US341285A 1940-06-19 1940-06-19 Multiplexing Expired - Lifetime US2298409A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US341285A US2298409A (en) 1940-06-19 1940-06-19 Multiplexing
GB7756/41A GB550193A (en) 1940-06-19 1941-06-19 Improvements in and relating to multiplex frequency-modulation systems
CH270709D CH270709A (de) 1940-06-19 1947-07-29 Mehrkanal-Radioanlage mit zweifach winkelmodulierter Trägerwelle.
FR989228D FR989228A (fr) 1940-06-19 1947-07-30 Système de transmission multiplex

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US341285A US2298409A (en) 1940-06-19 1940-06-19 Multiplexing

Publications (1)

Publication Number Publication Date
US2298409A true US2298409A (en) 1942-10-13

Family

ID=23336951

Family Applications (1)

Application Number Title Priority Date Filing Date
US341285A Expired - Lifetime US2298409A (en) 1940-06-19 1940-06-19 Multiplexing

Country Status (4)

Country Link
US (1) US2298409A (fr)
CH (1) CH270709A (fr)
FR (1) FR989228A (fr)
GB (1) GB550193A (fr)

Cited By (36)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2428297A (en) * 1943-11-06 1947-09-30 Rca Corp Selective radio frequency control system
US2446077A (en) * 1945-05-02 1948-07-27 Press Wireless Inc Frequency-shift telegraph system
US2479701A (en) * 1944-02-07 1949-08-23 William C De Vry Transmitting system
US2481516A (en) * 1946-03-22 1949-09-13 Lance R Jacobsen Mobile telephone system
US2487522A (en) * 1943-12-23 1949-11-08 Candeland Harold Electrical signaling system
US2495997A (en) * 1944-10-31 1950-01-31 Philco Corp Radio receiver aligning apparatus and method
US2496846A (en) * 1947-03-18 1950-02-07 Raytheon Mfg Co Communication system
US2499014A (en) * 1944-03-17 1950-02-28 Radio Electr Soc Fr Frequency modulating system
US2500090A (en) * 1945-02-14 1950-03-07 Rca Corp Radio relaying
US2509218A (en) * 1944-04-20 1950-05-30 Standard Telephones Cables Ltd Repeater link system
US2511204A (en) * 1948-01-08 1950-06-13 Rca Corp Frequency shift keying channeling
US2514425A (en) * 1945-02-06 1950-07-11 Rca Corp Radio relaying
US2519935A (en) * 1945-08-14 1950-08-22 Philco Corp Electrical system for the transmission of angular or azimuthal intelligence
US2536825A (en) * 1948-03-26 1951-01-02 Stromberg Carlson Co Multiplex telephony
US2538017A (en) * 1945-03-26 1951-01-16 Ernst H Krause Modulation-on-pulse control system
US2542700A (en) * 1942-02-20 1951-02-20 Rca Corp Pulse modulation system
US2546307A (en) * 1947-10-01 1951-03-27 Walter C Johnson Limiter circuit for telemetering systems
US2559644A (en) * 1948-09-18 1951-07-10 Rca Corp Pulse multiplex system
US2579882A (en) * 1947-06-05 1951-12-25 Rca Corp Interference suppression in radio signaling systems
US2580903A (en) * 1947-06-02 1952-01-01 Rca Corp Color television system
US2587541A (en) * 1947-11-29 1952-02-26 Rca Corp Pulse type modulator for facsimile signals
US2607853A (en) * 1947-01-27 1952-08-19 British Telecomm Res Ltd Telecommunication system
US2616975A (en) * 1947-02-06 1952-11-04 Rca Corp Time division multiplex system
US2621325A (en) * 1946-08-20 1952-12-09 Radio Electr Soc Fr Plural modulation multiplex system
US2654885A (en) * 1949-12-19 1953-10-06 Padevco Inc Multiplex frequency modulation communication system
US2670404A (en) * 1949-12-02 1954-02-23 Radio Electr Soc Fr Multichannel radioelectric communication system
US2700753A (en) * 1948-06-28 1955-01-25 Phillips Petroleum Co Method of and apparatus for seismic prospecting
US2705321A (en) * 1949-06-29 1955-03-29 Wing Engineering Corp Percentage modulation system for proportional control
US2776429A (en) * 1951-01-27 1957-01-01 Multiplex Dev Corp Multiplex communications system
US2844711A (en) * 1953-06-08 1958-07-22 Motorola Inc Multiple frequency channel multiplex communication system
US3462688A (en) * 1967-04-10 1969-08-19 William E Abel Communication system for classroom use and the like
US3480733A (en) * 1964-08-04 1969-11-25 Nippon Electric Co Frequency allocation system for common amplification of multifrequency carriers
US3852530A (en) * 1973-03-19 1974-12-03 M Shen Single stage power amplifiers for multiple signal channels
US4345334A (en) * 1977-05-05 1982-08-17 American Optical Corporation Reduced-cross talk telemetry system and method of manufacture thereof
US5027429A (en) * 1988-08-12 1991-06-25 Nec Corporation Frequency modulator utilizing frequency synthesizer
US5163181A (en) * 1988-10-21 1992-11-10 Harris Corporation Multiple rf signal amplification method and apparatus

Cited By (36)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2542700A (en) * 1942-02-20 1951-02-20 Rca Corp Pulse modulation system
US2428297A (en) * 1943-11-06 1947-09-30 Rca Corp Selective radio frequency control system
US2487522A (en) * 1943-12-23 1949-11-08 Candeland Harold Electrical signaling system
US2479701A (en) * 1944-02-07 1949-08-23 William C De Vry Transmitting system
US2499014A (en) * 1944-03-17 1950-02-28 Radio Electr Soc Fr Frequency modulating system
US2509218A (en) * 1944-04-20 1950-05-30 Standard Telephones Cables Ltd Repeater link system
US2495997A (en) * 1944-10-31 1950-01-31 Philco Corp Radio receiver aligning apparatus and method
US2514425A (en) * 1945-02-06 1950-07-11 Rca Corp Radio relaying
US2500090A (en) * 1945-02-14 1950-03-07 Rca Corp Radio relaying
US2538017A (en) * 1945-03-26 1951-01-16 Ernst H Krause Modulation-on-pulse control system
US2446077A (en) * 1945-05-02 1948-07-27 Press Wireless Inc Frequency-shift telegraph system
US2519935A (en) * 1945-08-14 1950-08-22 Philco Corp Electrical system for the transmission of angular or azimuthal intelligence
US2481516A (en) * 1946-03-22 1949-09-13 Lance R Jacobsen Mobile telephone system
US2621325A (en) * 1946-08-20 1952-12-09 Radio Electr Soc Fr Plural modulation multiplex system
US2607853A (en) * 1947-01-27 1952-08-19 British Telecomm Res Ltd Telecommunication system
US2616975A (en) * 1947-02-06 1952-11-04 Rca Corp Time division multiplex system
US2496846A (en) * 1947-03-18 1950-02-07 Raytheon Mfg Co Communication system
US2580903A (en) * 1947-06-02 1952-01-01 Rca Corp Color television system
US2579882A (en) * 1947-06-05 1951-12-25 Rca Corp Interference suppression in radio signaling systems
US2546307A (en) * 1947-10-01 1951-03-27 Walter C Johnson Limiter circuit for telemetering systems
US2587541A (en) * 1947-11-29 1952-02-26 Rca Corp Pulse type modulator for facsimile signals
US2511204A (en) * 1948-01-08 1950-06-13 Rca Corp Frequency shift keying channeling
US2536825A (en) * 1948-03-26 1951-01-02 Stromberg Carlson Co Multiplex telephony
US2700753A (en) * 1948-06-28 1955-01-25 Phillips Petroleum Co Method of and apparatus for seismic prospecting
US2559644A (en) * 1948-09-18 1951-07-10 Rca Corp Pulse multiplex system
US2705321A (en) * 1949-06-29 1955-03-29 Wing Engineering Corp Percentage modulation system for proportional control
US2670404A (en) * 1949-12-02 1954-02-23 Radio Electr Soc Fr Multichannel radioelectric communication system
US2654885A (en) * 1949-12-19 1953-10-06 Padevco Inc Multiplex frequency modulation communication system
US2776429A (en) * 1951-01-27 1957-01-01 Multiplex Dev Corp Multiplex communications system
US2844711A (en) * 1953-06-08 1958-07-22 Motorola Inc Multiple frequency channel multiplex communication system
US3480733A (en) * 1964-08-04 1969-11-25 Nippon Electric Co Frequency allocation system for common amplification of multifrequency carriers
US3462688A (en) * 1967-04-10 1969-08-19 William E Abel Communication system for classroom use and the like
US3852530A (en) * 1973-03-19 1974-12-03 M Shen Single stage power amplifiers for multiple signal channels
US4345334A (en) * 1977-05-05 1982-08-17 American Optical Corporation Reduced-cross talk telemetry system and method of manufacture thereof
US5027429A (en) * 1988-08-12 1991-06-25 Nec Corporation Frequency modulator utilizing frequency synthesizer
US5163181A (en) * 1988-10-21 1992-11-10 Harris Corporation Multiple rf signal amplification method and apparatus

Also Published As

Publication number Publication date
CH270709A (de) 1950-09-15
FR989228A (fr) 1951-09-06
GB550193A (en) 1942-12-28

Similar Documents

Publication Publication Date Title
US2298409A (en) Multiplexing
US2378298A (en) Composite-modulation radio service system
US3329899A (en) Submodulation systems for carrier recreation and doppler correction in single-sideband zero-carrier communications
US1950406A (en) Method and apparatus for controlling electrical waves
US2028212A (en) Radio transmitting system
US2094113A (en) Wave transmission
US2611036A (en) Selective sideband transmission and reception system
US1738522A (en) Electromagnetic wave signaling system
US2429504A (en) Frequency modulation network
US2389356A (en) Method of reduction of selective fading
US1976393A (en) Side band reversal transmission system
US3462554A (en) Transmission system utilizing independent diversity reception on plural sideband components
US1797317A (en) Binaural phase-discrimination radio system
US2852606A (en) Electrical communication systems and method of transmitting energy
US2855506A (en) Automatic frequency control circuit for frequency shift radio telegraphy
US1951524A (en) Variable frequency multiplex system
US1461064A (en) Multiplex transmission circuit
US2284706A (en) Arrangement for the transmission of intelligence
US1690299A (en) Generation and control of electric waves
US2542700A (en) Pulse modulation system
US1989770A (en) Wireless signaling system
Davey et al. Frequency Shift Telegraphy---Radio and Wire Applications
US1746829A (en) Radio signaling system
US1941447A (en) Radio telephone signaling
US2378013A (en) Synthetic modulator system