US 1882119 A
Description (OCR text may contain errors)
MEANS FOR RADIO COMMUNICATION Filed May 6. 1927 )9W cmg 'INVENTOR *L 0m '25 HENRI cmRElx fugaz/WE RNEY Patented Oct. 11, 1932 UNITED STATES PATENT OFFICE HET-BI OF PARIS, FRANCE HEANS FOB RADIO COMMUNICATION Application med Icy 6, 192,7, Serial No. 189,206, and in France Hay 10. 1926.
This invention relates to novel radio-telephony sending and receivingsystems, and more particularly to a transmlttlng system wherein modulatlon of the carrier wave 1s ac- 5 complished b novel means, and to a receiving system a apted to respond to szgnals sent by such transnnttlng system.
One object of the present lnvention 1s the provision in a transmission system of novel means for modulating in amplitude the radio frequency or carrier wave by speech.
The second object of the invention 1s to realize a transmission system in which.the radio frequency wave is modulated onlyin J phase when transmitted and not 1n amplitude; in other words, a system whereln the voice or speech has only the effect of producing rapfd variations in phase of the trans- Knitted wave, while the frequency and amplitude of the latterremain unchanged, and toprovide receiver apparatus in which these variations in phase are utilized for the purpose of causing variations in amplitude andy consequently of reproducing the speech. 4
The first object of the invention is based upon the observation that, if one excltes an antenna or a line by means of two electromotive forces of the same frequency and prefl erably of the same amplitude, the resultant intensity in the antenna will vary with the phase of the said two electro-motive forces. more particularly speaking, it will become zero when the two electro-motive forces are opposed, and will grow first linearly with the displacement or phase angle from vr. If, then, for instance, the antenna is excited by means of two electro-motive forces equal in magnitude and dis laced 150 degrees, for example, and if t e voice has the effect o of producing a phase displacement of one of said two electro-motive forces with relation to the other, -the amplitude in the aerial will vary, diminishing for the alterations of the telephone currents ocu) creasing on the contrary in the presence of a1- ternations of the telephone currents causing a decrease in the phase angle. Of course, it is o possible to act upon the relative phase of the two electro-motive forces either by acting From this generator are taken casioning an increase in phase angle, and in-` Now, this first object of the present invention may be carried into practice in a manner hereinafter described more fully.
Suppose there is available a high frequency alternator (generator) A of feeble power.
off two circuits, for instance, to excite two power amplifiers consisting of two triode tubes, there being inserted in the circuits connecting with these amplifiers meansadapted to alter the hase in a constant manner, such as self- 70 mductance coils condensers, resistance, or elements of artificial line. For instance, arrangements may be made so that the controlling potentials of the two amplifiers present a relative phase dierence of 150 degrees. 75 The output circuits of these two amplifiers are then connected or coupled with the antenna. In order to vary under the action of speech the relative phase of the input potentials of these `two amplifiers, one may -pro- S0 ceed in particular in the following two manners: t
(l) Insert in the connecting circuits of the generator and the amplifiers saturated selfinductances (magnetic amplifiers) in which 35 saturation is provided by the super-position of current due to speech upon a steady direct current. If these saturated self-inductances are connected in a resistance circuit adjusted to a point close to the resonance point, any variation in self-inductance will result in an appreciable change in the phase and a negligible change in amplitude.
(2). Superpose upon the constant otential of the input circuit of the ampli ers a modulated potential in quadrature with the former. If this modulated potential is sufciently low compared with the former, the phase of the resultant potential will be varied without affecting in an appreciable way its cos [wt-Hp sin nt] where i and Q, respectively, stand for the radio frequency and audio frequency pulsations, t for the time, and go for the maximum phase displacement angle, is equivalent for low values of q to a wave of this shape:
cos wtp sin (2t-sin wt that is to say, to the superposition of a nonmodulated wave and a completely modulated wave in quadrature with the former. Equation (1), moreover, may also be written in this form:
Y fined by 2 If this expression be now compared with hat of a wave modulated in amplitude of the orm cos wt+ cos @+RW-g cos (w-mt (2) cos wt (1-l-K cos Qt),
where K denotes the degree of modulation, it will be seen that the latter equation may b written as follows: v
cos wt-l-I cos (w-l-mt-i-I-2g cos (ar-mt (3) It will be seen that this expression differs from Equation (2) only by one sign. Now, it is well known that if a wave such as def(13) is received by a detector, each of the si e plulsations (arl-Q) and (ti-n) combines wit the pulsation wand results in the pulsation n, that is to say, speech, and in this case the amplitudes due to the terms (w-i-Q) and (mf-0) become added arithmetically. In the case of a. wave of the I kind defined in Equation (2) it will be seen from analogy that the speech currents due to interference (beats) between cos (arl-mt and cos wt and those due to interference (beats) between cos (ur-0)# and cos wt are neutralizing each other. But the remedy will be apparent at once, for all that is necessary is to dispose two filters, namely, a highass filter allowing of the passage of all p sations higher than o, and a low-pass filter permitting all pulsations lower than n to pass, or else-two band filters fulfilling the identical purpose.` Each of these filters must be followed bya detector at the output end of which there will be current-pulsating at speech frequenc Q. As these currents are displaced in p ase by 180 degrees, they will be o posed in the telephone receiver. As to t e rest, there is no objection whatever to the use of a type of receiver involving a change in frequency, so that the pulsation w may be always made the same. and so that the high-pass and low-pass filters may be adjusted once for ever with care. The second object of the invention is thus realized 1n the following manner: Sending end: independent generator of low power, tube amplier, means for changing the exciting phase of the amplifier with reference to that of the generator, either by the use of a saturated self-inductance or b the employment of a modulated potentia in quadrature with relation to the normal exciting potential. Receiving end: A receiver preferably of the type adaptable to frequency change, followed after amplification by two filters, one a high-pass filter and the other one a low-pass filter, each of said filters united with a detector. After detection, theaudio frequency currents are combined in a 'common circuit united with the telephone or connected with a low-frequency amplifier.
f The advantageous feature common to both these two objects of the invention is that of insuring economy in modulation. Modulation of the phase can be insured with an amount of power which is infinitely small even compared with that of the generator or the amplifiers. The latter function more'- over with practically constant grid excitation, and this allows of the use of amplifiers working at constant potential and good operating efficiency, a condition that would no longer be attained in a case where the output or the power of these amplifiers is to be of variable amplitude.
Finally, the second object of the invention, although requiring a receiver of special design, presents new and very valuable ad-v vantages. v
(l). Secrecy of communication- An ordinary receiver will receive but one carrier wave and respond to no modulation.
(2). Great immunitv from iamming and stray.-Indeed, in the light of what has been pointed out above i't will be noted that the re-constitution of speech necessitates the placing in opposition of two detectors. Inv
this way there is realized a sort of difierential arrangement in which the damped disturbances are opposed.
The invention will best be understood by reference to the following description taken in connection with the accompanying drawinin which:.^
ig. `1 schematically shows a transmitting arrangement forcarrving out the ,present invention,
ters shown in Figures 1 and 2 when adapted for phase modu ation.
Referring to Fig. 1, 1 stands for a radio frequency alternator'. 2 and 2' are two primaries of'Tesla transformers passed by currents conveniently phase-displaced with relation to each other, say, by 150 degrees. 3, 3 are the secondary windings of said transformers, said secondaries serving to excite two circuits, each comprising moreover a tuning coil 4, 4', respectively, a tuning cony denser 5, 5', respectively, and a saturated selfinductance 6, 6', respectively.
Each of the saturated self-inductance coils 6, 6' is represented in symbolic form by two transformers connected in series on the primary and secondary ends, though with the primaries reversed or inversed from the point of View of the linx, so as to indicate that there exists no transforming effect between the radio frequency and the audio frequency circuits. 7 stands for a telephone transformer, 8 a battery-furnishing a continuous saturation. i
From the arrangement ado ted it will be seen that the telephone current ecomes added to the direct current in one of the devices 6 or 6 at the same time as it decreases in the other device at the same instant.
In other words, when under the action of speech, one of the self-inductance coils grows in saturation, the other one loses in saturation to a corresponding amount.
The two circuits 3, 4,5, 6, and 3', 4', 5', 6 are preferably regulated so as to provide equal values for all elements, at exact tuning or resonance or slightly outside resonance,as maybe desired. To eect such regulation the battery 8 is in circuit, but no alternating current potential is applied across the primary terminals of the transformer 7, that is no speech is applied to the microphone.
Under these conditions, the currents passing through the circuits 3, 4, 5, 6, on the one hand, and through 3', 4', 5', 6', on the other hand, will preserve with relation to each other the same phase angle as .the current iiowing through the primaries 2 and 2', for reasons of symmetry.
If, then, an alternating current electromotive force be applied at 7, as when one speaks into the microphone, the two selfinductance coils 6 and 6' willbe caused to vary periodically in value, that is to say, one thereof becoming saturated when the other ticularly speaking, when the lself-inductance 6 ,decreases in value, the phase angle between the secondary current and the primary current decreases, andY vice versa.
Although nothing has been said respecting the resistance in the two circuits 3, 4, 5, 6, and 3', 4', 5', 6', it is nevertheless unfortunately there, and the very presence of this resistance allows vof gradual phase displacements. More particularly, if in the absence of telephone current, the secondary currents are exactly alike, theseconda currents are in quadrature relationship wit the primary currents, and the least variation in self-inductance results in a variation in the phase an le. In view of the fact that the two selfin uctancecoils 6 and 6' vary inversely under Y the ctlon of speech, it follows that the phase l displacement angle between the secondary current of the circuit 3, 4, 5, 6 andthe primary current flowing through 2' will decrease; in other words, the relative phase displacement of the two secondary currents will grow. It will be seen that for one halfcycle or alternation of the telephone current the relative phase angle of the two secondary currents will grow while it will diminish for the next alternation. If it is moreover noted that in order to produce a relative phase angle of the two secondary-currents of 30 degrees it suiices to produce a phase angle in each secondary of 15 degrees and that the phase displacement is automatically attained 1n a circuit regulated to resonance when producing a self-inductance'equal to one-fourth the series resistance of the circuit, that is to say, a wattless apparent power equal to 13B-th the watt, or real powerof the circuit, it will besseenthat the system ofmodulation is extremely economical in operation. Another advantageous feature is that the amplitude of the secondary current does not vary more than 3% underthe conditions as hereinbefore outlined.
Other details of the diagram Fig. 1 will be easily understood. 9 and 9' stand for two amplifiers excited, as has been shown, by
currents of-constant or practically constant amplitude, but of a phase subject to variation by speech. 10 and 10' are two oscillation circuits at the output end of the said ampliers. 11 and 11' are two couplings with the antenna circuit 'represented at 12 and tuned by the agency of inductance coil 13. The total electro-motive force induced in the antenna by the ,two couplings 11 and 11' varies with the phase displacement angle between the two, electro-motive forces induced separately by 11 and 11', and the antenna current naturally will vary in proportion with the total electro-motive force induced, while, on the other hand, if all conditions are symmetrical, the phase angle be- 5-tween the'electro-motive forces 11 and 11 will be identical to that existing between the currents of the secondary circuits 3, 4, 5, 6, and 3 4' 5', 6'.
Another method of practicin the underlying idea of the invention is iagrammatically illustrated in Fig. 2, where 1 stands as before for the radio frequency generator, 2, 3, and 2, 3 for two transformers arranged in such a way that the electro-motive forces induced in the secondaries 3 and 3 are in phase opposition. 14 and 15 are r1- mary and secondary windings of anot er transformer so that the secondary electromotive force induced in 15 is in quadrature relationship with the'electro-motive forces induced in 3 and 3. 16 denotes a complete tube modulator assembly combined with a microphone 17. In the operation of said modulator outfit recourse may be had, for instance, to the well-known method known as the constant-current orplate-.control system. In short, at the output end of device 16 there results a radio frequency potential modulated by speech and in quadrature relation with the electro-motive force induced by the transformers 2, 3, and 2', 3. 18 and 18 represent two transformers connected with the output end of the tube modulator 16. Elements 9, 9', 10, 10', 11, 11', 12, and 13 are the same as in Fig. 1.
The small graph in Fig. 3 shows the composition of the potentials applied to the amplifiers 9 and 9. AB and AB denote respectively the two potentials due to thetransformers 2 3 and 2'- BD and BD stand for the potentials induced by the transformers 18, 18 in the absence of speech modulation. AD and AD therefore denote the resultant potentials applied at the amplifier terminals 9, 9. p For total modulation of the amplitude of the modulator assembly 16, the resultant potential under the action of the voice, changes from AB to AC, for one amplier, and from AB' to AC', for the other amplifier. For less thorough or extensive modulation, the resultant vectors AD and AD will be subject to far less angular deviation. No matter how conditions may be, if the angle CAB and the angle CAB are. each limited to 30 degrees, it will be seen that for total modulation of the amplitude, the difference in phase of AC with relation to AC will change from 120 to I180 degrees. AD and AD forming an angle between themselves of 150 degrees. Under these conditions BC will be equal to l@ AB and BD equal to 1A, AB. The potential induced in the absence of voice actions by the transformers 18 and 18 will therefore be only M1 the potential induced by the transformers 2-3 and 2,-3. It will be seen moreover that AC exceeds AD by onl 9% approximately, whereas AB is only 3 o less than AD. y
`A transmitter of the kind embodying the second object of the invention can be built by starting from Figs. 1 and 2 in different manners, for instance, by eliminating all the lower parts havingindices, or if it is desired that the same transmitter should embody the two objects and prime features of the invention, this can be effected still more simply.
In the case of Fig. 1, it will-be sufiicient to arrange the battery 8V in series in the (ironcored) self-inductance saturation circuit as indicated at Fig.4 4. It will be noted, as a matter of fact, that in this case there are saturated at the same time the two selfinductance coils 6 and 6, and that they are also deprived of saturation simultaneously. What follows therefrom is that the relative phase of the potentials applied to the ampliiers 9 and 9 will not vary, but merely the phase of these potentials with relation to the primary currents flowing through the windings 2 and 3. It will moreover be noted that the relative phase of the currents flowing through the primaries 2 and 2 determines and governs only the intensity (of the current) in the antenna.
In the case of Fig. 2, the identical result will be attained, for instance, by inversing one of the windings of the transformers 2 3 and 2-3 which means the same thine' as changing in sign, in Fig. 3, the vector AB or else thevector A B.
Fig. 5 shows diagrammatically an assembly or equipment adapted to receive transmissions etl'ected by phase modulation. 21
stands for the antenna, 22 for an amplifierreceiver without detector. This receiver equipment is preferably of the type allowing of change in frequency. 23 and 24 are bandpass filters each followed by a detector, and allowing of the passage, one of the wave changed, if desired, in frequency, as wellas the higher frequencies up to 5 to 7 thousand' cycles, for instance, while stopping all lower frequencies, the other also permitting of the passage of the wave changed, if desired; in
frequency, as well aslower frequencies say from 5 to 7 thousand cycles, while stoppingl the higher frequencies. .Q5-and 25 stand for two low-frequency transformers connected in series, with the direction of winding being suitably chosen to add the incoming telephone currents. 26 finally stands for a lowfrequency amplifier connected with a telephone receiver 27. As has been pointed out above, modulation of the phase occasions a modulation in amplitude of a vector in quadrature with the mian vector (Equation (1) This amplitudel modulation may be resolved.
into two side frequencies or better into two lao side bands, if the modulation takes place at variable acoustic frequency (E uation (2)). The interference in a detector o each of said bands with the main wave reproduces the speech and as a consequence results in a current of musical frequenc in the transformers 25 and 25. Still, as fo ows from the signs, it is necessary that the interference (beat) of one band 'with the fundam should be separated from the interference (beat) of the other 'band with the same fundamental wave, whence the necessity of providing two filters and two detectors. It will be quite evident that only one filter could be provided, say, the upper or highpass band filter and .only a single detector, though in this case, one-half of the possibly available energy goes to waste, while it would furthermore not be possible by the same arrangement to neutralize atmospherics and jamming, as has been pointed out above.
It will be understood that the principle based upon phase modulation is also a plicable to modulated telegraphy. For this purpose, it is suilicient to ass into the saturated self-inductance coils ig. 1 arranged in a way as illustrated in Fig. 4, a musical frei quency current chopped up by a key. A11-- other possible scheme would be to pass into the same self-inductance coils several musical frequencies each controlled by a key. By subsequent filtering by well-known means and methods the musical currents after detection, multiplex sending could be obtained.
It will be evident to all trained in the art that there are a great number of possible modifications in details Without departing from the basic spirit of the invention. Especially the second feature and objectof the invention could be carried into practice with alternators or self-generating valve equipments in a great number of different arrangements.
Having thus particularly described the nature of my invention, I claim:
1. In a system of radio telephony, a utilization circuit energized by two independent sources of the same frequency but presenting a predetermined phase difference between themselves of substantially 150 degrees. and means.` including saturated self-inductance coils, for varying the phase difference, said means being controlled by sound waves.
2. In a system of radio telephony, the combination of a pair of circuits having similar characteristics, means for generating high frequency currents in said circuits substantially equal in magnitude and displaced about 150 degrees, a power amplifier in each of said circuits, oscillation circuits coupled to said amplifiers and to a utilization circuit, and means coupled to said first mentioned circuits for varying the phase difference between the currents in said two circuits in correspondence with sound vibrations, to correspondtal wave y gly alter the resultant current in said utilization circuit.
3. In a stem of radio telephony, the combination o a pair of circuits havin similar characteristics, means for generating high frequency currents in said circuits substantially equal in magnitude anddisplaced about 150 degrees, a power amplifier in each of said circuits', oscillation circuits coupled to 'said amplifiers and to a utilization circuit, saturated self-inductances inserted in each of said first mentioned circuits, and means effecting the saturation of said inductances controlled by sound vibrations foi'. varying the phase difference in said two circuits, thereby correspondingly altering the resultant current in said utilization circuit.
4. A receiver for a desired signal'modulated carrier wave, comprising collecting means, means to heterodyne the received carrier wave to an intermediate frequency, a filter tuned to pass frequencies higher than the intermediate frequency, a second filter arranged to simultaneously pass frequencies lower than the intermediate frequency, detector means associated with each filter, and means to combine the resulting audio frequencies subtractively.
5. In a system of radio transmission, the combination of a pair of circuits having similar characteristics, means for generating in said circuits high frequency currents of substantially equal` and constant amplitude and definite phase difference less than 180, means for varying said phase difference in accordance with sound waves, two distinct amplifiers havin one or more stages, one of said ylol amplifiers eing excited by one of said cir! l cuits, the other by the other of said circuits, and a utilization circuit coupled to the outputs of said amplifiers.
6. In a system of radio transmission, the f combination of a pair of circuits having similar characteristics, two independent sources for generating in said circuits currents of same high frequency and equal amplitude, the current of one circuit presenting a predetermined phase difference less than 180 over the current in the other circuit, means for varying said phase difference irrespectively of amplitude and in accordance with sound waves, two distinct amplifiers having one or more stages, one of said amplifiers being excited by one of said circuits, the other by the combination of a pair of circuits having similar characteristics, means for generating in said circuits high frequency currents of substantially equa-l amplitude and definite phase difference less than 180, saturated high frequenc and low frequency self inductance coils 1n each of said circuits, the low frequency coils being connected together and forming a closed circuit with the Windin of a trans ormer of a microphone circuit, a attery connecting the point between the low frequency coils and the middle point of said transformer winding, two distinct amplifiers having one or more stages, one of said amplifiers being excited b one of said circuits, the other of said ampli ers being excited by the other of said circuits, and a utilization circuit coupled to the outputs of said amplifiers.
9. In a system of radio transmission, in
combination a pair of circuits having similar characteristics, means for generating in said circuits high frequency currents of substantiallyequal amplitude and a definite phase difference less than 180, means for varying said phase difference in accordance with sound waves comprising an arrangement for superposing on the high frequency unmodulated current in each of said circuits an auxiliary modulated current leading the unmodulated component in one of said circuits by 90 and lagging the unmodulated component in the other of said circuits by 90, two distinct amplifiers having one or more stages,
one excited by one of said circuits and the other by the other of said circuits and a utilization circuit coupled to the outputs of said amplifiers.
.10. A radio receiving system adapted to receive waves modulated practically in phase only, comprising an aerial system, means to heterodyne the received signal so as to obtain a desired intermediate' frequency of its carrier wave, a high pass filter for said intermediate frequency and upper side band, a low pass filter for said intermediate frequency and lower side band, both filters being connected in parallel and each followed by a detector, the outputs of said detectors being connected in opposition, and a low frequency amplifier and signal responsive means associated with the detector outputs.-
11. In a secret radio signalling system including a transmitter for phase modulated Waves and a receiver adapted to cooperate therewith, the transmitter comprising a pair of circuits each coupled to an amplifier, means tively. e