US2276008A - Radio rebroadcasting system - Google Patents

Radio rebroadcasting system Download PDF

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Publication number
US2276008A
US2276008A US313498A US31349840A US2276008A US 2276008 A US2276008 A US 2276008A US 313498 A US313498 A US 313498A US 31349840 A US31349840 A US 31349840A US 2276008 A US2276008 A US 2276008A
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United States
Prior art keywords
frequency
band
frequencies
current
cycles
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Expired - Lifetime
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US313498A
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English (en)
Inventor
Edwin H Armstrong
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Individual
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Individual
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Priority to BE473378D priority Critical patent/BE473378A/xx
Application filed by Individual filed Critical Individual
Priority to US313498A priority patent/US2276008A/en
Application granted granted Critical
Publication of US2276008A publication Critical patent/US2276008A/en
Priority to GB996/47A priority patent/GB621229A/en
Priority to FR946481D priority patent/FR946481A/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B14/00—Transmission systems not characterised by the medium used for transmission
    • H04B14/002—Transmission systems not characterised by the medium used for transmission characterised by the use of a carrier modulation
    • H04B14/006—Angle modulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/155—Ground-based stations
    • H04B7/165—Ground-based stations employing angle modulation

Definitions

  • the object of this ⁇ invention is to' provide a ⁇ relay system for frequency modulated signals
  • relay systems There are two types of relay systems. In one the signal from the relay transmitter is detected and converted into its original form and this-current is used to modulate the broadcastqtransmitter, In the second type thereceived radio frequency current is heterodyned to the frequency to be rebroadcast, amplied up and transmitted without ever being converted into the audio or other signaling current. In each type of relaying certain difficulties are encountered. In the rst type, reception is carried out with an ordinary frequency modulated receiver of sufhclent selectivity to distinguish between the received and retransmitted signals without overloading the initial stages of amplification. The signals are detected in the usual manner and applied to the modulation of the transmitter in the usual way.
  • the frequency of 'each transmitter is determined solely lby means located directly at each station and that the frequency of the retransmitted wave is independent of any changes in the frequency of the relay transmitter.
  • the frequency of the second station depends on the constancy of-the frequencyv of the first station. Hence where the frequency of the relay transmitter is high any drift in its frequency is accentuated in the beat frequency created at the second stationl by ⁇ tiie interaction between it and the locally lgenerated frequency.
  • Fig. I illustrates in a purely schematic way a frequency modulated transmitter in which I represents the antenna, 2 a power amplifier for feeding the antenna and 3 a modulator for modulating the frequencyy to be radi" ated in accordance with the signaling currents to be transmitted.
  • the modulation is supplied with two sources of modulating current; one the ordinary speech or musical currents of audible frequency,v and two, a superaudible current of constant amplitude and frequency which will be assumed to be of the order of 100 k. c. per second.
  • the transmitted wave has a frequency of 130,000,000 cycles and that the deviation or change in frequency from this point is 50,000 cycles above and below for the modulations which correspond to the speech frequencies.
  • the purpose of the 100,000 cycle modulating current will appear hereinafter.
  • a filter 9 which has a band Width of something in excess of 200,000 cycles, amplified by the amplifier I as in ordinary superheterodyne practice and passed through a limiter II.
  • the wide band filter I2 passing a band which may be approximately 925-1075 k. c. and a narrow band filter I3 whose band width may be from 1075 to 1125 k. c.
  • I4 represents an amplier for the output of the narrow band filter, I5 a converter whose heterodyning current is supplied from a crystal oscillator I6 having a frequency which will be assumed to be 1500 k. c.
  • the output of the converter is passed through a filter I'I having a band pass of 2575 to 2625 k. c., and the output of this lter is supplied to a second converter I8.
  • 'I'he converter I 8 is likewise supplied with a current from the output of .the band filter I2.
  • the ou-tput of the converter I8 is passed through a filter I9 which has a band width of 1525 to 1675 k, c.
  • 20 represents a crystal or other fixed frequency oscillator generating some submultiple of the frequency 41,400 k.
  • c. 2I represents a multiplier or a series of them for raising the frequency of the oscillator to 41,400 k.
  • c. 22 represents a converter for mixing the outputs of I9 and 2
  • 23 represents a lter, 24 a power amplifier, and 25 the retransmitting antenna.
  • the transmitter when unmodulated radiates a single frequency of 130,000,000 cycles.
  • the band width occupied is 129,950,000 cycles to 130,050,000 cycles.
  • 100 k. c. modulation is applied. If the deviation is not made too great, two new frequencies only will appear at 129,900,000 cycles and 130,100,000 cycles, the other frequencies of the series being relatively insignificant. These frequencies are radiated continuously and at constant amplitude.
  • the frequency band radiated in response to the speech or other signaling frequencies varies from a maximum width of 100,000 cycles down to zero in accordance with the strength of the signaling currents. Turning now to the receiver of Fig.
  • the incoming 130,000,000 cycle current is heterodyned down to 1,000,000 cycles.
  • the ,transmitter is fully modulated by the signaling current and is also modulated at the auxiliary frequency of 100,000 cycles there will appear in the intermediate frequency circuit of the receiver the following currents: 900,000 cycles, 1,100,000' cycles and a band of frequencies running from 950,000 cycles to 1,050,000 cycles. All of these currents are passed through the limiter II and appear in its output circuit. where the frequency band representing the signaling frequency is selected by the broad band filter I2 and the upper frequency 1,100,000 cycles is selected by the narrow band filter I3.
  • the 1,100,000 cycle current is then amplified and converted to 2,600,000 cycles by adding i to it a 1500 kilocycle current produced by the crystal oscillator I6.
  • the filter I1 selects this frequency and supplies it to a converter I8 where it is combined with the output current from the broad band filter I2 which comprises the frequency band of the signaling currents.
  • the difference frequency which varies between 1550 and 1650 k. c. is selected by the filter I9. It will be observed that by this process a frequency modulated current whose variations or modulations correspond in every respect to the modulations of the megacycle current has been produced yet whose midfrequency is independent of any changes or drift in frequency of the transmitted wave.
  • Fig. III An alternative method of producing the result is illustrated in the arrangement shown in Fig. III, which illustrates a somewhat different form of transmission system.
  • the auxiliary high frequency is transmitted separately and the frequency difference between it and the main frequency is determined in another way.
  • Referring vnow to Fig. III represents a master oscillator, 3
  • the principle employed in my co-pending application for U. S. patent, Serial No. 313,497, filed January 12, 1940, is employed in this system so that changes in the frequency of the oscillator are balanced out.
  • 38 represents an amplifier and 39, 40 the frequency multipliers which form a source of heterodyning current for the converter 31 as will be hereinafter explained. The output.
  • represents an oscillator whose frequency is some submultiple of the frequency which it is desired to radiate and 42 a filter for selecting one of the frequencies resulting from the combination of the output of thel frequency multiplier 40 and the oscillator 43.
  • 44 represents a series of frequency multipliers for raising the output current of the converter 31 to the frequency to be'radiated, 45 a power amplifier for this frequency and 46 the antenna for radiating it. This channel produces the main signaling current.
  • the auxiliary frequency is produced by the other channel.
  • 41 represents an amplier for the current produced by the oscillator 43, 48 a converter, 49 another oscillator whose purpose will be expla-ined later and 50 a crystal filter for selecting the desired frequency resulting from the .combination in the converter of the currents from 41 and 49.
  • represents an amplifier, 52 a series of frequency multipliers and 53 a power amplifier whose outputA is supplied to the antenna 54.
  • the unmodulated pathv through the amplifier 38 is likewise multiplied up through the multipliers 39, 40 to 12.8 megacycles, and supplied to the converter 4
  • An4 oscillator 43 preferably crystal controlled, generates a frequency of 2708.3 k. c. which is likewise supplied to the converter 4
  • the transmission may be received by the arrangement of Fig. II provided the power of the auxiliary frequency is kept below the level of the main transmission. However, a preferable arrangement for reception is shown in Fig. IV.
  • This arrangement while generally like that of the receiver of Fig. II, differs from it in an important aspect. This consists in separating the main channel currents from the auxiliary cur- ⁇ rent by means of the broad and narrow filters 66 and 65 respectively, before limiting and making use of separate limiters 10 and 68. Other- Wise the action of the receiver is the same as in Fig. II the resulting final output current at 19 is supplied to the transmitter as in Fig. II. It will, of course, be understood that while a single intermediate frequency receiver ⁇ has been shown for the sake of simplicity that a double intermediate frequency one may be used.
  • Such a receiver is in fact desirable when frequencies as high as megacycles are being dealt with and it will likewise be understood that the automa-tic tuning devices which are now well known in the transmitter current of 41,400 k. c. to produce the 'are supplied to a converter 80 which is also excited by av current derived from an oscillator 82 of 10.35 megacycles.
  • av current derived from an oscillator 82 of 10.35 megacycles One of the resulting output currents has a frequency of 11.95 megacycles which may be readily separatedl from the 10.35 megacycle current. This is accomplished -by raising the frequency in two stages that the filtering problem has practically disappeared.
  • the method of signal transmission which consists in frequency modulating a carrier wave with a band of signal frequencies, transmitting the modulated carrier wave, transmitting a wave having a constant frequency differing from the frequency of the carrier wave by a frequency above audibility, receiving the transmitted waves, heterodyning the received waves down to a low intermediate frequency by a heterodyning current of constant frequency, selecting in parallel paths from the low intermediate frequency a derived frequency differing from the median intermediate frequency by the difference in frequencies between the carrier and the wave of constant frequency, and a band of frequencies corresponding to the signal frequencies; increasing said derived frequency to provide a higher frequency, beating said higher frequency with the selected band of frequencies to produce a band of frequencies corresponding to the signal frequencies, and causing the frequency of a second carrier wave of different frequency than said first-named carrier wave to vary in accordance with the frequencies of said band.
  • a radio transmission system the combination of means for transmitting a band of frequency modulated signals on a carrier wave, means for transmitting a wave having a constant frequency, a first converting device, means for receiving the transmitted waves and impressing them on said converting device, a local oscillator connected to said converting device and arranged to generate a frequency differing from the frequency of the carrier wave by a low intermediate frequency, a pair of parallel paths connected to the output of said converting device.
  • the first of said paths being arranged to block currents in the middle of the low intermediate frequency band and to pass currents diering in frequency from the mid-intermediate frequency by an amount equal to the difference in frequencies between the carrier wave and the wave of constant frequency
  • the second of said paths being arranged to pass a low intermediate frequency including the frequency modulations of the signal
  • a second converting device connected to said parallel paths to provide in the output thereof a resultant frequency including the frequency modulations of the signal, means for increasing the resultant frequency to the frequency to be transmitted, and means for transmitting currents of the resulting increased frequency.
  • a frequency modulation signal transmission system in combination. a first generating device arranged to generate radio frequency oscillations, a rst converting device, a circuit connecting said converting device and said generating device and comprising means for multiplying the frequency generated by the generating device, means for frequency modulating the currents in said circuit in accordance with the signals, a second converting device having its output connected to the input of said first converting device, a circuit connecting the input of the second converting device and said generating device and comprising means for multiplying the frequency generated by the generating device, means connected to the output of said first converting device for transmitting frequency modulated signaling currents, a third converting device, a second generating device arranged to generate radio frequency oscillations and connected to the inputs of the second and third converting devices, a third generating device connected to the input of said third converting device and arranged to generate a frequency which is a submultiple of the difference between the frequency of the frequency modulated currents and the frequency of the constant frequency currents and means connected
  • the -method of preventing changes in the ⁇ frequency of vthe transmittedwave due to variations in the frequency of the received wave which consists in frequency modulating a carrier wave with a band of signal frequencies, transmitting the modulatedl carrier wave and also a second wave whose frequency differs from the frequency of the carrier w'ave by a substantially constant amount, receiving the transmitted waves, heterodyning the received waves down to a low intermediate frequency.
  • a system for rebroadca'sting frequency modulated carrier waves comprising, in combination,
  • means for generating a carrier wave means for frequency modulating the carrier Wave with a band of signal frequencies, means for transmitting the carrier wave and also a second wave whose frequency differs from the frequency of the carrier Wave by a substantially constant amount, means for receiving the transmitted waves, means for heterodyning the received Waves down the selected band of frequencies to produce a' second band of frequencies corresponding to the signal frequencies, means for increasing the frequency of said second band to the frequency to ybe transmitted and means for transmitting currents of the resulting frequency.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Transmitters (AREA)
US313498A 1940-01-12 1940-01-12 Radio rebroadcasting system Expired - Lifetime US2276008A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
BE473378D BE473378A (en)van) 1940-01-12
US313498A US2276008A (en) 1940-01-12 1940-01-12 Radio rebroadcasting system
GB996/47A GB621229A (en) 1940-01-12 1947-01-11 Radio rebroadcasting system
FR946481D FR946481A (fr) 1940-01-12 1947-05-09 Perfectionnements aux procédés de radio-transmission

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US313498A US2276008A (en) 1940-01-12 1940-01-12 Radio rebroadcasting system

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US2276008A true US2276008A (en) 1942-03-10

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US313498A Expired - Lifetime US2276008A (en) 1940-01-12 1940-01-12 Radio rebroadcasting system

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BE (1) BE473378A (en)van)
FR (1) FR946481A (en)van)
GB (1) GB621229A (en)van)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2460781A (en) * 1943-10-07 1949-02-01 Rca Corp Circuit for stabilizing frequencies of transmitter-receiver systems
US2476141A (en) * 1946-08-21 1949-07-12 Rca Corp Frequency shift keyer
US2516885A (en) * 1944-04-17 1950-08-01 Standard Telephones Cables Ltd Relay system
US2579070A (en) * 1945-02-14 1951-12-18 Rca Corp Multiplex communication system
US3237121A (en) * 1962-02-10 1966-02-22 Int Standard Electric Corp System for eliminating am to pm conversion in an fm system utilizing a plurality of equalizers

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2460781A (en) * 1943-10-07 1949-02-01 Rca Corp Circuit for stabilizing frequencies of transmitter-receiver systems
US2516885A (en) * 1944-04-17 1950-08-01 Standard Telephones Cables Ltd Relay system
US2579070A (en) * 1945-02-14 1951-12-18 Rca Corp Multiplex communication system
US2476141A (en) * 1946-08-21 1949-07-12 Rca Corp Frequency shift keyer
US3237121A (en) * 1962-02-10 1966-02-22 Int Standard Electric Corp System for eliminating am to pm conversion in an fm system utilizing a plurality of equalizers

Also Published As

Publication number Publication date
FR946481A (fr) 1949-06-03
BE473378A (en)van)
GB621229A (en) 1949-04-06

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