US2333719A

US2333719A - Two-way radio communication system

Info

Publication number: US2333719A
Application number: US432741A
Authority: US
Inventors: Edward W Herold
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1942-02-28
Filing date: 1942-02-28
Publication date: 1943-11-09
Anticipated expiration: 1960-11-09

Description

Nov. 9, 1943. E. w. HERoLD TWO-WAY RADIO COMMUNICATION SYSTEM 'Filed Feb. 28, 1942l ATTORNEY Patented Nov. 9, 1943 fA f UNTED t y '21332'.,7121 TWO-WAYRADIO COMMUNICATIQ e,

SYSTEM mawvarjcll W. Herma* verme, N. "J1, t0-

of Delaware Application February 2s, 1942, VSerienV No; niet ,.111 apfeenee wit shan be meenemen `fixed reieto to @een filth., A. L halve' iridiateg etatio ground station. v`for' ein l' B when used for transmission employs a microphone I8, a modulator l 6, and a transmitting ampler 28. The antenna 6 is connected both to the converter 8 and the amplifier 20. In some instances, it may be unnecessary to apply the'output from the oscillator 2 directly to the receiver converter 8 because the energy fed through the amplifier may be combined vwith incoming signals and fed through the conductor 24 to the converter 8.

Where the circuit arrangement isk as just mentioned, it will, of course, be desirable- )apparent that exclusive communication between to employ in the converter unit, or in a subse-x" quent stage, filtering means for suppressing the carrier and the oscillations of the local source 2. j

The oscillator 2 may be frequencycontrolled '1 by the incoming signals in accordance with Wellknown practice. The automatic frequency control device 22 is, therefore, shown conventionally for this purpose. Although automatic frequency control devices are Well known, reference is here made to United. States Patent No. 2,121,103, granted June 21, 1938toS. W. Seeley for a comprehensive disclosure of how they may beconstructed and operated. I will now present a mathematical discussion of thetheory of operation of my invention: Let fa=the frequency of the oscillator I of station A, say4 210megacycles, for example. Let fb=the frequency ofthe oscillator 2 at station B, say,200 meagcycles.

, Let fithe frequency towhich the intermediate frequency amplifiers A7 and 4 are tuned, say 10 megacycles. Then, Y Y,

Now if station A is transmitting, then station B can placeitself in two-way communication with station A merely bytuning its own oscillator 2 .so that reception of station A s signals will beproperly received. By the samey tuning operationat station B, ythe signals transmittedtherefrom will be suitable for reception byk station A. It is essential to the successful operation of my system,I however, that both stations maintain anI agreed-upon tuning of their intermediate frequency amplifiers, both to the samel frequency.

If it is desired to change the intermediate frequency tuning` in accordance with a prearranged schedule, basedon agreement as to time of change, or any other'system,'then an element of secrecy is'introduced into the communication. Not knowing what intermediate frequency is to be used, an unauthorized receiver would be unable to pick up the incoming signals without considerable search for the transmitting carrier, and most probably would not be able to answer back.

It is not necessary that the same antenna 5 or 6 should be used both for transmission and reception, but it has been shown as a'single antenna at each station merely for thesake of simplicity. It may not alwaysbe necessary to employ an automatic frequency control such as the unit 22 at either of the stations, but should any drift in frequency 4occur at one terminal, adjustment of the tuning of the oscillator at the other terminal will automatically assure perfect two-Way communication, provided the intermediate frequency amplifiers 3 and 4 of the corresponding stations are similarly tuned. o

In connection with automatic tuning, itshould be noted that correction of the local oscillator serves additional purposes as compared with those previously contemplated. That is to say,`auto and . to those skilled in the art.

the master station and any one outlying station could be obtained by the use of differently tuned intermediatefrequency amplifiers and differently "tuned oscillators at'the outlying stations. Where this idea.y iscarried out, station B can receive selectively from any outlying station such as A, A', etc., but would need to select a local intermediate frequency for its own intermediate frequency amplier to bein agreement with the fixed-frequency of the 4 I. F. amplifier at the. selected. outlying station.v After makingthis adjustment, two-way communication .would. berestablished` simply by listeningto the signals from the selected outlying station and causing the local oscillatorofrequency at station B to be thereafter.automaticallycfrequency contro1led.,In orderito tunethe, local station to a frequencywhich the,A remotestation will accept, while at the Sametime adjustingthe tuning of ^`the local Vstation tothe frequency which the remote station radiates, it siof c ourseneces-f sary to selectanintermediate frequency for Vthe localstation which correspondsmwiththe intermediate frequency ofthefremote station. one consideration determines the adaptability@ the system for control of both stations from the one master, station. f Other modifications of the principle I have outlined will be readily apparenttothosefamiliar with superheterodyne, reception., 1 For example. a receiver may be adapted toireeive bothy signals which are lower yin 1frequency than the Vlocal 9s.- .Cillator and those which erehgher than `the os.- cillator (the so-called image response),. Thus, a group of stations mayintercommunicateandvany given station may act as a type A to someqof the other Stationsvand as a type `Bftothe remainder- When twosuch svstemspperate vwith different I. F. amplier frequencies onlywthose *stationsy within a givensystem A canestablisn two-way ommuniatiea, L o t,

The practical adaption Vof my ideadsv readily apparent to those skilled in the art andrthereappears to be no need for` further, description of modulation and power-amplicatdnequipment- 'Ihe system may b euappliedwith amplitude, .frequency or phase modulation-,and the intelligence to betransmitted may be sound, television, Vfacsimile or offany other type capable of being converted into electricalcurrents or potentials. In complexity, the system may range from the simplest transceiver employing a single-tube, ,selfoscillating frequency converter; Withflocal modulation on the oscillatorand a` one-,tubev intermediate frequenysystem, yto a highly comple;

andmodulators, radio frequency amplification and multi-stage intermediate frequency amplification with automatic frequency controlli V/ My invention is tobe understood as-comprehending the various modifications Suggestedabove as well as others which might suggest themselves Y l n The s copeI of the'irl-A vennen is, therefore. Adefined br the Claims- Y i I claim: t Y 1. A two-way ycommunication system operable between two radio stations, each station com,-

plier in the receiver, the intermediate frequency ampliers at the two stations being tuned to the .prising a transmitter, a superheterodyne receiver, .an oscillator Vcommon `to the transmitter `and Y the receiver, and any intermediate frequency am-` i operable between two radio stations, each station comprising a transmitter, a superheterodyne receiver, an oscillator common to the transmitter and the receiver, and an intermediate frequency tampliflervin the receiver, means for adjusting same frequency,' and means located at `one of l said stations for maintaining a vfrequency separation betweenthe outputl energies of the two said oscillators equal to the frequency to which said intermediate frequency amplifiers are tuned.

2.,Asystem in accordance with claim l and including an automatic frequency control device in the means for maintaining frequency separation.l v .l Y

3. A system in accordance with claim 1 and including an automaticfrequency control device in the means for maintaining frequency separation and operable in accordance 4with Variations in the frequency of the receivedl vcarrier wave.`

4. A two-way vcommunication system in accordance with the invention defined in claim 1,

wherein ther oscillator at one station .is adjusted to operate at a frequencyabove the signal frequency receivedsby said station and the oscilla'- tor at the otherstation is adjusted to operate at a frequency below the signal frequency received by said other station. t j

5. In a two-waylradio communication system wherein each of two stations comprises a transmitter, a superheterodyne receiver, an oscillator the tuning conditions at only one of the stations to satisfy the'tunng conditions at both stations necessaryV for two-wayl communieationA therebel tween, said means comprising` means' for tuning the intermediate frequency amplifier at'said one 'station to operate at they same frequency as that l of the `intermediate frequency amplifier at the other station and additional means for main-v 'taininga frequency separation between the os-f cillators at thetwo stations equal to 'the operating frequency ofsaid intermediate frequency ampliers. a

, 7.' The methodaeeordmg to claim 5 and including the step of causingthe carrier wave re- 'ceived at said one station to automatically control thefrequency of the oscillator thereat. l

8- In ,a -radio communication. system having a master station and aplurality of outlying respondentv stations, wherein each station come prises a transmitter, a superheterodyne receiver,

` (an oscillator common to the transmitter and the common to the transmitter and the receiver,a`nd

an intermediate frequency amplifier in the receiver, the method of adjustingthe tuning conditions at one station only, to satisfy ther tuningr conditionsat both stations necessary fortwo-way` communicationI therebetween, which method comprises tuning the intermediate frequency amplier at said one station tothe same frequency receiver and an intermediate frequency amplien. and wherein said master stationA includes an automatic frequency control device operable upon its oscillator to control the frequency thereof in accordance with an incoming carrier wavegthev method of adjusting the tuning conditions at said master `station lto satisfy the tuning'condi--` t vtions thereatand simultaneouslyto establishtwo-I way communication between said master station and a selected ione of Asaid/respondent stations,

t whichtmethod comprises tuning the intermediate as that of the intermediate frequency amplifier at Y the other station,` and maintaining afrequency separation betweenl the oscillators at the two stations equal to the tuning frequency of said I intermediate frequency amplifiers. a Y

frequency amplifier at the master station to the same frequency as that of the intermediate fre-i quency amplifier at said selected station,v and tuning the oscillator ofthe master station sothat a frequency separation is maintainedbetween it vself and the. oscillator of the selected station equal to the selected intermediate frequency.

- Y EDWARDW; HEROLD.`

, c'. In a two-way radio communication system y