US1868339A - Arrangement for the one sided band modulation of high frequency vibrations - Google Patents

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July 19, 1932. TRAUTWEIN 1,868,339

ARRANGEMENT FOR THE ONE-SIDED BAND MODULATION OF HIGH FREQUENCY VIBRATIONS Filed Feb. 2, 1926 o'uo'uunuun'uu'o'cu INVEHTDR Fr d lfh TmuTwein HTTOR HEY.

Patented July 19, 1932 FRIEDRICH TRAUTWEIN, F BERLIN -ZEH LEN DORE,

GERMANY, ASSIGNOR TO THE FIR-M DR. ERIGH F. HUTHGE'S. M. B. or BERLIN, GERMANY ARRANGEMENT FOR THE ONE SIDED BAND MODULATION OF HIGH FREQUENCY VIBRATIONS Application filed February 2, 1926,

It is common knowledge that in the modulation of high frequency oscillations as a rule the amplitude is varied in a low frequency rhythm so that the average value of the high frequency amplitude fluctuates in accordance with the low frequency. It is further known that, in this kind of modulation, an exact and true transmission'of the low frequency amplitude is not obtained seen from the mathematical definition of the proceeding. If the high frequency is designated-by N, the low frequency by n, the

time by t, the high frequency amplitude by A, the low frequency amplitude by a, and the initial amplitude designated by the index 0, a modulated oscillation has the equa- 'tion:

A=A sin Nt+A a sin [Vt sin n I This equation may be transformed into A A sinNt cos (N+ mt II composed of three frequencies, viz., the orig-- inail high frequency and the sum and the difference from highand low frequency.

The modulation may also be explained by interference, the frequency N+n as well as the frequency N -n executing with the frequency N'a beat note of frequency a. The ;wo beat notes assist one another in their mutualelfect. The Equation II shows'however that, besides these two interferences. just been mentioned, the twov which have side waves 1V+n and N 11- do also interfere,

the beat frequency of the same being equal to (N+'/1.)(1V-n)=2n, i. e., double the originallow frequency. At the receiving station the modulation amplitude, at the surging frequency is rendered audible and is observedas sound. lVith the above described kind of modulation one hears therefore in the receiver besides the original low frequency amplitude the octave of the same. Thereceived sounds are therefore distorted. 'Bhisv distortion is especially disturbing if as can be easily.

one of the two side bands.

'3. TBS 0113 1108 CLlIVG.

Serial No. 85,460, and in Germany February 3, 1925.

ance with the present state of the art of wireless telephony in order to maintain within moderate limits the sound distortion owing'to the prominence of the octaves. The transmitter therefore normally operates at are].- atively low degree of efiiciency.

Methods have become known to suppress It is difficult to eliminate a side-band by the usual resonance tuning method, since the breadth of frequency band obtained by modulation expressed as percentage in respect to the carrier frequency is much narrower than the technically obtainable minimum width of This specially holds for short waves. Even if a'sufiiciently sharp resonance curve can be obtained, for instance with comparatively longer waves, an unequal influence on the several-portions of the frequency band, i. e., distortion of the speech currents will be unavoidable. Filters with comparatively steep ascent are then employed.

According to'this invention the suppression of one side band is effected by means of a compensation arrangement which is shown by way of example in the accompanying drawing.

Fig. l is a diagrammatic representation of one embodiment of my invention for eliminating one side band and Fig. 2 is a diagrammatic representation of another embodiment of my invention wherein both the carrier wave and one side band are eliminated. The oscillations produced by a high frequency generator 1 of any convenient type are divided in such a manner, e. g. by properly adjusting the coupling conditions, that on the grids of the Valves 2 and 3 similar voltage amplitudes exist. The high frequency grid amplitudes in the valve 3 aredisplaced 90 in phase with regard to those on the valve 2 by means well known in the art, this being attained in Fig. 1 by the aid of the adjustable condenser 4. The low frequency amplitudes coming from the leading. in wire 5 are conducted to the valves 2 and 3 at voltages which are also equal regard to the-current in circuit 5 as is well .The anode currents of -p'lace in the valve 2. The proceeding in the A =A cos N H- oscillation amplitude supplied to the work to theantenna becomes to each other, the low frequency amplitude in the grid of the valve 3 being also displaced 90 in phase with regard to that on the grid of valve 2. In Fig. 1 this is indicated by the connection of a voltage transformer 6 with valve 2 and voltageotrans, former 7 with valve 3. By properly choos- 'ing the coupling factors of the transformers the voltage drop on the comparatively low resistance of the secondary Winding of 7 can.

be displaced 180 in phase with regard "to the inducing current of the circuit 5, while the voltage impressed across the secondary winding of 6 is displaced 90 in phase with known in the art. the valves 2 and 3 are addedand transferred upon the'output circuit, for instance the antenna 8. Instead of the ordinary "ulation shown by way of example in Fig. 1- any other kind of modulation might be used and highand low frequency may be used in controlling the amplitude of thesignaling current. 9

grid modamplifiers -'I"o eXplain the operation it may be supposed that the modulation proceeding represented in the above stated Equation II takes valve 3 is then explained by the 'following equation =A cos Nt+ A a cos Ni cos m5 7 III which may be transformed into cos (N a )t IV By addition of Equations II and I'Vthe circuit, for instance Aba cos (N n)t V 7 the Equation IV would have to be subtracted from II. In'this case the frequency N the sum N a are obtained. In bothcases I band may rice -' work circuit but only the two side present. Combining such a method with the combination of the modulation posite phase only the one or the other side proceedings Methods are does not occur in the bands are the carrier wave itself method underlying this invention, the high frequency oscillation as well as the low fre-- quency oscillation being-displaced 90t-in ,3 and3 are the other pair of plitudes of the and "bands of modulated frequencies,fsuperimone of'the two side frequencies or'side bands has disappeared and by similar phase or opbe supplied to a work circuit. known for modulating a high frequency carrier wave in such a manner that" phase in one circuit with regard to the other, only one side band will be obtained in the work circuit in an analo ous manner, without the carrier wave. In Eig. 2 such a, method is diagrammatically illustrated by way of example, the well-known push-pull modulation being supposed to be used for the suppression of the carrier wave. 1 is the high frequency generator, 2, and 2 are the one pair of valves for the push-pull modulation, valves for the push-pull modulation, a phase displacement of 90 between the high frequency grid amtwo valves with the aid of the condenser 4; being presumed. The low frequency transformer 6 serves for the modulation in the group of valves 2;, 2 from the circuit 5, and the transformer 7 serves for the modulation of thegroup of valves 3 3 at phase displacement of90 with regard t0 2,, 2 The modulations in2 2 and 3 3 free from the carrier waves, are added by common coupling at'the samerphase or at opposite phases in a work circuit, for instance the antenna 8. Y

Iclaim: H r Y 1. A systemof modulating carrier frequency with suppression of carrier wave and one of'the side-bands comprising electron device arrangements, each one connected to suppress the carrier wave, separate input circuits for said arrangements, a common output circuit for said arrangements, means for into two components producing a 90 phase shift'between'said' components, dividing a carrier frequency wave into two components equally having a 90 phase difierence therebetween," utilizing one component of said carrier wave and one component of said modulating wave'to produce side bands of modulated frequencies, utilizing the remaing component of said carrier frequency Wave and the remaining component of said modulating wave to produce further side posing resultant pairs of side bands to eliminate all but a single side band carrier modulate-d wave and at-the same time suppress the carrier.

r A system for producing a single side band carrier suppressed modulated wave which comprises in combination a source of modulating waves, two circuits branched therefrom, means in said branched circuits for producing a phase shift in the respective branch'circuits, a source of carrier frequency,

'means'for deriving from said source two carrier wave components, means for producing a phase shift between said carrier wave rent shifted 90 out of phase to balance the components, means for modulating said deeffect of one of the resulting modulation side rived carrier waves by the output wave from bands in said output circuit.

said branch circuits respectively to produce upper and lower side bands of each of said derived carrier waves, means for superimposing the resultant pairs of side bands whereby both the carrier and all but a single side band are balanced and suppressed.

4. A system for producing a single side band carrier suppressed modulated wave which comprises in combination a source of modulating waves, two circuits branched therefrom, means in said branched circuits for producing a phase shift in the respective branch circuits, a source of carrier frequency, means for deriving from said source two carrier wave components differing from each other in phase by 90, means including a push-pull circuit arrangement for modulating said derived carrier waves by the output wave from said circuits respectively to produce carrier suppressed upper and lower side bands of each of said derived carrier waves, means for superimposing the resultant pairs of side bands whereby one side band of each pair is balanced out and the remaining side bands are added.

5. A system of modulating a carrier wave with suppression of the carrier frequency and one of the side bands comprising a pair of electron tube arrangements, each of said arrangements being connected to suppress the carrier frequency, separate input circuits for said arrangements, a common output circuit for said arrangements, means for producing separate carrier frequency components and separate modulating frequency components, respectively, to be applied to said arrangements respectively, and means for shifting the phase of one of said carrier frequency components and one of said modulating frequency components by 90 with regard to the remaining carrier frequency component and the remaining modulating frequency component respectively.

6. In a modulating system as described in claim 5 in which each of said arrangements comprises two vacuum tubes with their grid controlled in push-pull fashion by the respective carrier frequency component.

7 A system of modulating carrier frequency with suppression of the carrier wave and one of the side bands comprising two electron device arrangements including pushpull circuit connections to suppress the carrier wave; separate input circuits for said arrangements; a common output circuit for said arrangements; means for applying carrier currents of equal frequency to said arrangements; further means for shifting the phase 90 at carrier frequency on one of said arrangements; and means for modulating both carrier currents in said arrangements in accordance with acommon modulating cur- In testimony whereof I aflix my signature.

DR. FRIEDRICH TRAUTWEIN.

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