US1946274A - Method of signaling - Google Patents

Description

Feb. 6, 1934'.

H. CHIREIX 1,946,274

METHOD OF SIGNALING s Sheets-Sheet 1 Filed March 5, 1931 INVENTOR HENR CH E\X BY 7 WG/L/ ATTORNEY Feb. 6, 1934. H. CHIREIX METHOD OF SIGNALING Filed March 5, 1931 5 Sheets-Sheet 2 INVENTOR HENR CHiREm ATTORNEY Feb. 6, 1934. H. CHIREIX 1,946,274

METHOD OF SIGNALING Filed March 5, 1931 3 Sheets-Sheet 3 OUTPUT INVENTOI'F HENRI CHIIEIX BY g owl/ ATTORNEY Patented Feb. 6, 1934 METHOD OF SKGNAMNG Henri Chireix, Paris, France, assignor to Compagnie Generate de Telegraphic, Paris, France, a ccrpcraticn oi France Application March 5, 1931, Serial No. 529,309, and in Francel'tiarch 5, 1930 7 Giaims.

It is well known that speech or music can be represented by a series of frequencies which in concentrated form may be symbolically represented by the expression n COS u 4 an designating the amplitude of the component of pulsation Sin and of phase displacement qbn.

The normal telephonic modulation caused by any transmitter or emitter of pulsation w and of amplitude A may be expresed by:

A cos wfll-l- K COS n n)} Km being in that case the degree of depth of modulation expressed in percent of the pulsation 911.

It is likewise known that this expression is identical with:

The first term representswhat is called the carrier wave, the second term the upper spectrum or band, the third term the lower spectrum or band.

It is interesting, and this has already been done for the commercial telephony (not requiring the same quality of reproduction than music or songs) to eliminate from the transmission either the carrier wave and one or" the lateral bands, or simply a lateral band.

This has been done up to the present time exclusively by means of band filters.

Considering that, for the components of low frequency of speech, the two bands are very close to each other, it may be realized that it is impossible with filters to effect the separation for these low frequencies.

The present invention, which is known as the Chireix system, discloses one method of overcoming the aforementioned difliculty.

Gn the basis of the id ntity:

cos wi cos (ltd; sin wt sin S2t=cos (w $821M down to the lowest frequencies and having the form:

a cos (S2,,t- 15 a n Sin @J- 1 For the application of the method according to the invention a first great difficulty to be solved consists, there being given a spectrum of currents to produce, starting out from this spectrum, another spectrum identical with the first with respect to the respective amplitudes an but representing currents shifted in phase by 90, this to hold true even for the very low frequencies. This problem can only be solved approximately, but in accordance with the modes of realization furnished by the invention, the solution obtained may be as close as desired.

In the accompanying drawings, Figures 1 and 2 illustrate two circuit schemes in accordance with the present invention of obtaining a current in quadrature with the applied current, but having the same amplitude.

Figures 3 to 5 illustrate detailed methods of obtaining two currents in quadrature with respect to each other from a source of applied current over a wide range of frequencies.

Figures 6 and 7 illustrate two embodiments for use in arrangements such as those illustrated in Figures 1 to 5 for suppressing the carrier and one of its associated side bands without the use of filter circuits.

Figure 8 illustrates, in schematic form, the essential elements or" a complete system embodying the principles of the present invention wherein reference characters in the boxes represent the numbers of the figures which are shown in detail in the other circuit arrangements.

One means of realization is furnished by the circuit of Figure 1 comprising, connected in series with an inductance L, a condenser C, a resistance r and a second resistance r. The input potential E is supplied by the conductors 1 and 1' between L and C on the one hand and between 1' and r on the other hand; the output potential e is collected between the conductors 2 and 2' connected respectively between L and r on the one hand and between C and 1" on the other land; in this circuit, for all the frequencies here considered, the resistances r and r are small compared with the inductive and capacitative impedances. If the circuit resonates at the pulsation we and if 1*:1" the potential collected between 2 and 2' is:

This potential varies little when w/wo varies to both sides of unity and is on the other hand in exact quadrature with E within an infinitely small value close to the second order if the variation of e is considered as infinitely small of the first order.

Another means of realization, furnished by the circuit of Figure 2 wherein the impedances shall be small compared to the resistances R represents a variant producing the same results.

Nevertheless, the diagrams of Figures 1 and 2 give a much too rough solution of the practical realization of the method.

A better solution is furnished by the diagram according to Figure 3 in which Q1, P1, Q2 are phase-shifting devices of the type of those of Figures 1 and 2, T a transformer with two secondaries 1, 1 the input leads, 2, 2' an output line for the potential in quadrature, 3, 3' an output line for the potential in phase.

The telephonic currents being supplied by 1, 1, there is obtained in ab a potential in quadrature with E, of an amplitude at being a certain coefiicient due to the device Q1. On the other hand there is directly taken at cd, with the aid of a potentiometer, a portion in phase of the potential E. To this co-phasal tension is then added another tension furnished by the transformer T. This potential is produced by the potential ab having traversed a device P1 identical or similar to Q1. It is of the form and in phase with E, since it has been subjected to a double phase shift of The transformer T furnishes likewise a potential which is impressed on a device Q2 similar to P1 and Q1 and which reproduces at e a potential of the form:

and which is in quadrature with E since it has been subjected to three successive phase shifts.

There will then finally be obtained at 2, 2' a potential in quadrature of the form:

o+ o/ +v( o+ o/ and at 3, 3 a potential in phase of the form:

By a suitable choice of the parameters or, ,8 and 'y these two potentials may be rendered quite equal to each other over a large range of frequencies. Thus, for instance if oc=0.82, 5:0.19, :0.0125 the difference of the potentials compared to their sum is lower than 2.5% for a range of frequencies from w/ 10 to 10100, in other words for a spectrum of frequencies going from 1 to 100.

It stands to reason, besides, that the method of obtaining the correcting terms by the introduction in the connections of successive correcting devices is a general one and that there may be re-introduced in the lines 2, 2 and 3, 3 respectively, a third corrective term of potential, then a fourth, etc.

It will be noted, nevertheless, that, if the rela- I tive amplitudes as well as the phase relations are preserved, the amplitude in absolute value increases if moving away from the geometric average. This fault could be remedied by placing at the input a corrective circuit which in its most simple form may be a simple resonant circuit suitably damped such as represented at C.

From the practical point of view the circuit arrangement must be done in the manner as to prevent any shunting at the outgoing end of the phase displacing circuits, and for instance by means of relay tubes, as indicated in Figure 4, which may be understood without further description, the letters and numbers of reference designating the same elements or terminals.

A variant of Figure 4 is given in Figure 5. This variant has the purpose to prevent phase displacements which may be introduced by the transformers if these latter are not constructed correctly.

Having produced the two systems of currents:

an d.

a means for applying the method of modulation in accordance with the invention is furnished by the connection diagram of Figure 6, given by way of example.

Two high frequency potentials in quadrature are branched off the line 1, 1 by means of two tuned circuits I and II, the circuit II obtaining tubes or groups of tubes, connected in opposition. lg The grids of the symmetrical circuit III are fed by means of conductors 7, 7' which are on the other end connected to the two armatures of condenser 11 of the tuned circuit I, provided with two seif-inductances, one, 9, being the coupling means with the self-inductance 10 of the tuned circuit II. At the arinatures of the condenser 12 of this second tuned circuit are branched the two conductors 8, 8' which feed the grids of the symmetric circuit IV. The grid-cathode circuits of the symmetrical circuits close across center taps on the self-inductances 9, 16, the said taps being connected to the body 15 across polarizing batteries 14, 1e, and the cathodes of the tubes are likewise connected to the body 15. potentials impressed on the circuits III and IV are modulated, for instance according to the system called anode control system or system with constant current, by the outputs coming from the lines 2, 2 and 3, 3' of Figures 4 or 5.

If the symmetrical circuits are balanced in the manner that the wave of pulsation w does not pass, there is collected in the output circuit V by the line 4, 4'

according to the sign of the connections.

If one of the symmetrical circuits is unbalanced,

The

partly or completely, by eliminating one of its tubes, there is furthermore collected a carrier wave A cos or or A sin wt according to whether the debalancing affects III or then IV.

In one case or the other a system of transmission will exist answering the condition indicated at the beginning of this application.

A particularly interesting application of the method and devices according to the invention resides in broadcasting. The suppression of one of the lateral bands is the means, all other things being otherwise equal, to place in one and the same frequency band twice as many transmissions. It permits, besides, the reduction in half of the shifting band of the receivers and accordingly, due to a more pronounced syntony, the reduction of the influence of the atmospheric strays. In the case of a radio broadcast transmitter functioning according to the principle called the amplification with modulated high frequency, the circuit of Figure 6 would be simply inserted between two stages of high frequency amplification without further complications. For the same reasons the antenna may be tuned closer since the frequency spectrum is reduced by half. In this case by the way, the fact that the amplitudes have a tendency to increase, in spite of the correcting circuit, for the deep notes and the high notes is rather an advantageous item considering the diihculty of a good transmission of the extremities of the spectrum of the acoustic frequencies.

The present invention is particularly useful in various types of short wave systems, especially in multiplex telegraph and telephone communication systems operating either on a code basis or any other suitable basis.

The following example relates to a telephone communication system and is merely mentioned as an illustration, not as a limitation.

The frequencies of the first telephonic transmission P may be written symbolically for a given instant as EP; likewise the frequencies of the second 2Q. Well understood, the spectra are the same, they are the ones of the voice. By applying the connections of Figures 3, 4 or 5 and 6, the spectrum 2P may be transposed to the spectrum E(F+P) or then again to the spectrum 2(F-P), F being a frequency of the order of several thousands per second, so as to separate the new spectrum Z(F+P) or Z(FP) from the spectrum 2Q. Then there may be modulated, always according to the circuits of Figures 3, 4 or 5 and 6, the short-wave transmitter by a spectrum of frequencies or a band of frequencies A e, the spectrum A comprising:

1. The spectrum 2Q 2. The spectrum 2(F+P) or E(FP) 3. A frequency F1 At the output of the balanced circuit of Figure 6 we will have fo-l-Af, f0 being the high frequency; assuming:

fo-i-EQ lateral band fo+2(F+P) lateral band fo+F1 carrier wave At the reception, the frequency (fo-l-Fr) will act like a carrier wave and after detection we will find the currents:

which is transposed speech, or transposed and inversed.

If for instance F1=4000-Der second F =9000-per second after detection the spectrum of the communication Q will be 2 (4000Q) and the spectrum of the first communication 2(5000+P).

These communications may be separated by filters and rendered intelligible after demodulation by heterodynes of 4000 and 5000 periods per second.

They are, furthermore, both unintelligible for any observer not being in possession of the material necessary for the reconstruction.

If it is a case of making f=9000 periods per second, F is made=4000 periods per second, the communication Q will always be after detection in the spectrum 2(4000-Q), hence unintelligible, but the transmission P will be directly intelligible, since its spectrum will be If, inversely, F1 would be made=0 and if the modulator is unbalanced so as to let pass fo, the communication Q would be directly intelligible (continuous carrier wave) and the communication P would be transposed in the spectrum E(F-|-P). Naturally the examples may be varied infinitely and are only given as illustration,

In the case where the transpositions to be effected are only of some thousands of periods, as. has been said in regard to the examples for multiplex communications, the diagram of Figure 6 may be replaced by a more simple scheme (Figure 7).

Let I, II, III, IV be rotary variable condensers Whose capacities may be written:

C+c cos wt for I C-c cos wt for II 0+0 sin wt for III C-c sin wt for IV and let V be condensers of equal size and of a capacity 1 large as compared to C'+c.

Applying on the other hand at 2, 2' and 3, 3 of Figure '7 the spectra furnished by the circuit according to Figure 4 or 5, represented by the expressions 12 n Sin n n) the potential at the terminals of condenser V with respect to I can be written:

The potential of condenser V with respect to II may hkewise be written:

n ill cit an cos CcIoos wt hence the difference of potential between a and b Accordingly, there may be effected telephonic transpositions by utilizing the circuits of Figure 4 or 5 with a circuit such as that of Figure '7 and, secondly, the suppression of the high frequency carrier wave and one of side bands by applying the spectrum previously obtained to a circuit comprising the arrangements outlined in either Figure 4 or 5 working into the circuit of Figure 6. Such an arrangement is illustrated in Figure 8.

t should be distinctly understood that the invention is not limited to the precise arrangement of parts disclosed herein since various other modifications and organizations may be resorted to without departing from the spirit and scope of the appended claims. For example, the invention may be readily utilized for radio broadcasting, for short wave communication systems and for multiples telegraph and telephone communication systems.

Having thus described my invention and the operation thereof, what I claim is:

1. A circuit arrangement for obtaining a wave presenting a phase angle of 90 degrees with reference to an applied wave spectrum while preserving substantial equality of amplitude relation throughout the frequency range between currents of each frequency in the obtained wave and the applied spectrum, including a bridge arrangement comprising four elements of which two adjacent elements are respectively an inductance and a capacity, and two others two equal resistances, the value or" each or" said resistances being greatly difierent from each of the said pair of impedances, means for applying the wave spectrum to two opposite apices of the bridge, and means for collecting the phase-displaced wave at the other two apices of. said bridge.

2. Circuit arrangement adapted to obtain from a given wave spectrum two wave spectrums, one presenting the sad e phase angle as the original wave spectrum, and the other waves spectrum presenting phase angle of 90 degrees, these two wave spectrums being of like amplitudes, comprising a plurality of circuits associated with the source of current, one of said circuits containing in cascade an even number of phasedisplacing circuits causing the change in phase of 90 degrees, and means for superposing the output currents of these latter phase displacing circuits in a common or joint circuit, another of said plurality of circuits associated with the source of current containing in cascade an odd number of the said phase-shifting circuits, and means adapted to superpose the output currents of these latter circuits in another common or joint circuit.

3. In combination, a radio frequency source, a radio communication circuit arrangement adapted to derive from said source two waves presenting a relative phase displacement of 90 degrees, two symmetric circuits passed respectively by each of said waves, means of modulation of the output currents of these circuits respectively by currents of like amplitude, but of a phase displaced 90 degrees, a circuit arrangement as claimed in claim 1 for causing the last mentioned phase displacement, and a common circuit associated with the said symmetric circuits' 4. In combination, a Wheatstone bridge arrangement having a variable condenser in each of two adjacent arms thereof, two impedances in the other arms of said bridge, said impedances having values differing greatly from those of said condensers, another Wheatstone bridge similarly constructed to said first bridge, both said bridges being connected together at one of their apices, means for applying at two other opposite apices of each of said bridges two waves of equal aniplitune, but in phase quadrature with respect to each other, and terminal connections to the fourth and last apex of each of said bridges for obtaining currents therefrom.

5. A combination in accordance with claim 4 characterized in this, that said condensers are of the rotary type. I

In a communication circuit whose characteristics are suitably chosen whereby there is obtained from a wave spectrum two other wave spectrums of equal amplitude, over a large range of frequencies, one of which wave spectrums is phase and the other of which is 90 degrees out of phase with respect to said first wave spectrum, the method of communication which includes shifting the phase of a portion of the current of the first wave spectrum twice successively, each time so degrees with respect to said first wave spectrmn in order to obtain one of said desired wave spectrums and shifting the phase of the current a third successive time again by 90 degrees to obtain the other desired wave spectrum.

7. In a communication circuit whose characteristics are suitably chosen whereby there is obtained from a wave spectrum two other wave spectrums of equal amplitude over a large range of frequencies, one of which wave spectrums is in phase and the other of which is 90 degrees out of phase with respect to said first wave spectrum, the method of communication which includes shifting the phase of a portion of the current of the first wave spectrum twice successively, each time 90 degrees with respect to said first wave spectrum and adding to said twice shifted wave spectrum another portion of said first wave spectrum obtained without any phase shift in order to obtain one of said desired wave spectrums, and shifting the phase or" a portion of the current of the first wave spectrum a third successive time again by 90 degrees and adding thereto still another portion of said first wave'spectrum obtained merely by a 90 degrees phase shift in order to obtain the other desired wave spectrum.

HENRI CHIREIX.

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