Патент USA US2406881код для вставки
Sept. 3, 1946. 2,406,881 N. H. YOUNG, JR METHOD AND SYSTEM FOR COIVHVIUNICATING INTELLIGENCE ` Filed Sept. 19, 1942 l@ INVENTOR /VOPMÄN H. YOUNG, JR. BY I . ëÍ D % M. ATroRNl-:Y - Patented Sept. 3, 1946 2,406,881 VUNITED STATES PATENT OFFICE METHOD AND SYSTEM FOR COMBIUNICAT ING INTELLIGENCE Norman H. Young, Jr., Jackson Heights, N. Y., as signor to Federal Telephone and Radio Corpo ration, a corporation of Delaware Y Application September 19, 1942, Serial No. 458,934 8 Claims. (Cl. 179-1.5) 1 , This invention relates to a new method and; 2 . system for communicating intelligence, and is tion I0. The output of the receiver 38 is con nected, on theone hand, to a pilot filter 40 which particularly adapted for use as a secret radio is sharply tuned t0 the frequency 0f the pilot communicating l Accordingly, an object of this invention is to oscillator I2 a1; the transmitting station and to a harmonic filter 44 tuned and employed to ex provide a novel and simple method and means tract the phase modulated harmonic component. for communicating intelligence secretly. `Another' object of this invention lies in provid The pilot filter 40 is used at the receiver 35 as a local pilot frequency generator, and the output therefrom passes through a frequency multiplier system. ` ` ’ ing a novel method and means for transmitting , intelligence which can be intelligibly received 10 ¿i2 comparable to the frequency multiplier IG at only upon a properly correlated receiver. ' the transmitting station. By means of a bal Other objects and advantages of the invention anced detector 46 the phase-modulated harmonic will become apparent from the following descrip tion of a preferred form of system, illustrated in the accompanying drawing, in which: Fig. 1 is a block circuit diagram of a complete transmission system in accordance with the pres ent invention; and ` Fig. 2 is a diagram illustrating the operation of the system by means of correlated curves. Referring specifically to Fig. 1, and more par ticularly to the transmitting station I0, the latter will be provided with a constant frequency source derived from the filter 44 and the unmodulated harmonic derived from the frequency multiplier 42 are compared and the diiîerence in phase is translated into suitable audio frequency signals which, through an amplifier 4I are impressed upon the loud speaker 50. The balanced detector 4:6 used for demodulation may be of the type 20 known in the television art as a “discriminator” such as described, for example, in the book “Prin ciples of Television Engineering" by Donald G. Fink, page 405, Fig. 250, published by McGraw Hill Book Company, Inc. 1940. is passed through a frequency multiplier I6 to ,25 It is believed that the operation of the afore produce oscillations at a harmonic frequency. described system will be clear to those skilled in The frequency multiplier I6 is preferably a fre this art. It involves the principle of modulating a carrier wave as for example, by amplitude mod ` quency tripler of some suitable well-known con struction. The outputl from the frequency multi ulation or frequency modulation, by means of a plier I6 passes through a suitable phase modu 30 wave which is a-combination of a fundamental such as a pilot oscillator I2, the output of which lator 22. ’ At ,I8 I have provided a microphone as an eX ample of a suitable intelligence translating de vice, the output of the microphone I8 being pref erably amplified by audio amplifier 20 and ap plied to the phase modulator 22 to phase modu late the harmonic oscillations received from the frequency multiplier IE. wave such, for example, as a 10 kc. wave and the phase-modulated harmonic thereof, such as a phase-modulated 30 kc. wave. The resultant signal or intelligence which is transmitted will be 35 diflicult of detection and can only be reconverted into an intelligible signal provided the receiver is equipped with means for providing a source _of frequency exactly the same as that provided at the transmitter and with the proper accurately In a suitable mixer 26 the phase modulated harmonics from the phase modulator 22 are 40 designed harmonic filter. If the frequency multi plier I ‘à at the transmitter also reverses the phase added to the fundamental wave derived from the of the harmonic by 180° the modulation of the pilot oscillator I2 to produce, by simple addition, a resulting wave which will vary slightly in ac carrier wave in accordance with the transmitted intelligence will be most difficult to detect by un cordance with the amount of phase deviation of the harmonic component. This resulting wave is 45 authorized receivers, as the resultant voltage change in the modulating wave will be extremely impressed upon a modulator 28 connected be slight. This may be graphically illustrated by tween a suitable carrier wave source 32 and the transmitter 30. The resultant modulated carrier way of example in Fig. 2, in which the wave A wave will then be radiated by antenna means 34. may represent the fundamental frequency pro The receiving station generally indicated at 35 50 duced by the pilotI oscillator I2 while B repre sents the third harmonic with a 180° phase shift. will include an antenna 36 connected to a re ceiver 38, which will include suitable demodu The resultant wave produced by the addition of lating means for demodulating the basic carrier waves A and B when the wave B is exactly 180° in accordance with the type of modulation em- ' out of phase with the wave A, is represented by ployed at modulator 28 of the transmitting sta the curve C. The phase modulation of the har 2,406,881 3 4 monic B which, in most cases, will not exceed 30° of the harmonic or 10° of the fundamental ceiver, a frequency multiplier connected to said pilot frequency filter, a balanced detector fed will produce a wave C’ which, it will be noted, will differ only slightly in amplitude from the wave C. The Wave C’ is the resultant of the ad from said harmonic filter and said frequency dition of the fundamental A to the harmonic B' shifted 30° relatively to the wave B. It will be noted that by shifting the harmonic 180"V with respect to the fundamental A the peak of the harmonic substantially coincides with the peak’ of the fundamental thus producing sharply de-1 fined peaks in the resultant wave. As previously 2. The combination according to claim 1, in which said frequency multipliers include means for shifting the phase of the derived harmonic multiplier, and audio output means connected to said balanced detector. 180°. ' 3. The method of transmitting and receiving intelligence'which includes the steps of phase modulating a harmonic of a predetermined pilot frequency >in accordance with audio signals, add ving 'the phase-modulated harmonic and the mentioned,'however, the peaks of the resultant wave will differ only slightly in amplitude for relatively large phase shifts in the harmonic. 15 >'fundamental pilot frequency together, transmit ting the wave resulting fromrthis addition, re Preferably, the amplitude of the harmonic Will ceiving Vsaid wave, separating the pilot frequency be approximately no greater than 30% Of the and harmonic, changing the filtered pilot fre amplitude of the fundamental. It is to be noted quency to the same’frequency as the harmonic, that if the frequency multiplier I6 at the trans mitting station includes means to shift the phase 20 comparing the phase deviation between the fil tered harmonic and the- derived harmonicLand of .the harmonic 180°, similar means must be in r'ern‘o'dlicing> the `audio signals in laccordance with clude'd in the frequency multiplier 42 at the re ceiving station. said phase deviation. ' scribed 'system Without departing from the prin cîples of thev present invention. As has been previously mentioned, the manner in which the carrier-'wave is 'modulated by the ’resultant phase ’ modulated wave is unimportant. ' _4. A transmitting station including, in com vlÍt will be clear to those skilled in this -art 'that various changes may be 'made in ‘the afcrede bination, a transmitter, -a source of carrier Waves, a modulator connected between said transmitter and carrier wave source, a iirst constant fre quency source, a second constant frequency , source producing a frequency which is a harmonic The manner in 30 of said first constant'frequency source, means which the pilot >frequency Vand harmonic are gen for modulating the phase of said harmonic in erated `is likewise of no particular importance. instead of phase ’modulating the harmonic by translated audible signals, the source of intelli gence can be of any type which will suitably operate the phase modulator v22. Changes in the 'details of the transmitter l0 will also result in comparable Achanges in details of the' vapparatus accordance with signals to be transmitted, means for adding saidV phase-modulated harmonicV to used at 'the receiver 35. It is also obvious that said ñrst constant frequency source, and means for impressingY the 4resultant _of such addition upon said carrier wave modulator. l’5. The combination according to claim 4, in combination with a receiver adapted to be tuned to ’said transmitter, means connected to said re as far 'as the basic principles of this invention ceiver for 4obtaining the `phase-modulated har are concerned, it is possible to phase modulate the ‘lower frequency wave instead of the higher 'frequency wave provided, of course, the yfrequen monic, >a 'constant frequency source at said re cies are harmonically related. l While the system ‘according to my invention is particularly adapted for use in radio Ycommu nication, it will also be clear that a direct line y ceiver producing the unmodulated harmonic, means forV comparing ksaid phase-modulated har-> monic with; said locally generated harmonic, and means'ifor reproducing the transmitted signal in accordance with the differences in phase between said harmonics.' l , - n ‘connection between the transmitting stationk and y675A ‘transmitting station including, in combi the receiving stationcan be used, if desired. Accordingly, while for the purposes of ldescrib ing the invention, reference hasbeen made to nation, a transmitter, a lsource ofl carrier waves,` a modulator connected between said transmitter certain speciñc ‘devices and'relationships, it is to ‘be understood that the invention is not limited thereto except as maybe required 'by the claims which follow. ~What I claim is: A transmission >system comprising, in com source, 'a frequency Vmultiplier Iconnected Vto said and carrier wave source, a constant frequency constant frequency source, a phase modulator Aconnect/ed 'to said frequency multiplier, a mixer connected to said carrier wave modulator, means for feeding the> output 4of vsaid constant frequencyY source and of said phase modulatorjto said mixer, loination a’transrnitting station 'including a trans- ` and a variable frequency signal source opera tively connected -to said phase modulator. mitter, a source of carrier waves, a modulator 'connected between said transmitter and carrier 60 Y"7. The combination vaccording, to claim lo, in wave source, ‘a 'pilot oscillator, a frequency mul which lsaid frequency multiplier includes means tiplier connected to said pilot oscillator, a phase for shifting 'the phase of 'the harmonic 180". modulator fed by said frequency multiplier, a 8. The method of signaltransmission, which mixer connected to saidvcarr'ier modulator, means includes the steps :of lphase modulating a waveV of ‘for Iïf'ee'ding'the output of sai-'d` pilot oscillator and 65 frequency -harinonically related to 'a ‘predeter-~ said phase modulator to said mixer, and an audio mined 'pilot frequency in Yaccordance with the frequency source connected to said phasemodu signals to betlîansmitted, adding the phase modu later, and a receiving station including a receiver lated >frequen cy to the ‘pilot frequency, and ‘moduf adapted to‘receive signals from said transmitter, lating a carrier 'wave‘by the wave resulting from aïpilot frequency filter and a harmonic frequency 70 filterboth connected to the »outputof said re ' « "" NORMAN H. YOUNG, J R. this addition. " ’ Y . . .