US1582044A - Wave-modulation system - Google Patents

Description

BEST AVAILABLE COP:

April 27, 1926. 1,582,044

J. W. HORTON I WAVE MODULATION SYSTEM Filed Dec. 28. 1923 Jase #7 W/mm I W A see Patented A r.- 27, 1926,

PATEN lLhBL GOP 1,582,044 T fOFFlCE.

,rosnrn w. scams, or nnoourrnnn; NEW JERSEY, assronon :ro wns'rnnu nnnornrc comm, mconrona'rnn, or new YORK, N. Y., a CORPORATION on NE YORK.

wavn-nonnna'rron srs'rma Application fledhecember 28, 1928. Serial No. 888,098.

To all whom it may concern:

Be it known that I, Josnrn )V. Hon'ron,

a citizen of the United States of America,"

.residing at Bloomfield, in the county of Essex and State of, New Jersey, have in vented certain new and usefu Improvements in Wave-Modulation Systems, of which the following is ajull, clear, concise, and exact'description.

The present invent-ion relates to modulation of electrical waves for signaling-pr kindred pur oses.

It is an o ject of the invention to obtainby modulation certainv characteristiowave products to the exclusion of other wave products. I

'It has beenfound that'when a continuous wave of given frequency-has its amplitude vor other characteristic varied in accordance with some time-variation scheme, a large number of wave products, e. g. frequency components, are produced, many if not most.

of which are both useless and troublesome in any ractical installation.

An 0 ject of the invention is to provide :1. simplified modulating arrangement which :is capzble of efficiently producing desired modu tion products to the exclusion of un-. desired components. 1 A feature comprises a modulator arrangement which is capable of producing desired components without giving riseto certain] undesired components, so that there is no' need to balance out such undesired com-V ponents'.

A further feature of the invention comprises a simplified modulator'arrangement for eliminating in an etlicient and practical manner a number-of undesired components and leaving a single or'small number of 7 other components, as desired.

The various features and obi cots of the. invention will appear'moreful y following. detailed description of typical modulators embodyingthe invention and illustrated in the accompanying drawing, in

which:

' Fig. 1 is a diagrammatic; representation of a modulator employing a vibratory type of magneticsyste Figs.2 and 3 are similarrepresentations of modulator systems employing rotating elements, and

Fig. l illustrates modulator capable of 'ically electrically to setup instan- ,whereR is the mean value of the relucfrom the balancing out alarge'number of components as may be'desired.

- Briefly and specifically, the invention may comprise a magnetic modulator in which a magnetic; circuit is influenced both mechanso taneous field intensities which correspond instant for instant to the amplitude of modulated current or voltage wave to'be transmitted." The mechanical variation may be made at the carrier frequency andfor' this purpose either vibratory elements, such as reeds, tuning forks and, the like, may be used, o r rotating elements similar to known types of armature may be employed. By so relating the moving mechanical element to thecore or field magnets that the reluctances 'of a plurality of ma etic circuits are varied simultaneously, t becomes a 'simple matter" to associate windings with $=fi (1+7: cos pt) "(1) tano," h 'is equal to one half the ratio of i the diflerenceib'etween the maximum and minimum reluctance to the average reluctance, and p'equals 21: times the frequency of a sustained wave which is'to be,modulated, whiclf frequency will be called, for convenience, the carrier frequency. H It is also as'siiined that the magnetic circuit has a polarizing winding through which. a

polarizing current flows, the instantaneous value I of which is eipressibleasz.

, where I, is the average current and 9 equals Upon writing cos pt as and expanding, it is found that 95 can be expressed -by the series:

This equation may be evaluated' for any articular case by referrin to the expressions given above for the various'coeificicnts, and it has been thrown into this. form merel for convenience in considering the physics significance of the difierent terms. lVhile equation (6 is in terms of flux variations, it may rea ily be changed into an e) pression of the same dgeneral form'fo'r'the voltage variations pro need in anioutgoing circuit arranged, for example, in inductive relation with the field, by observing the relation: v f

1 21; where N is the number of turns in the secondary coil.

Considering now the si ificance of the various-terms of equation 6 the first term A may be passed over as of noimportance 'for modulation purposes, since this term simply represents the steady polarizing current or the ma etization of the core. If a neutralcore with no direct current. in the windings were used, thisterm would'not be present. Also. its magnitude "is not in v any way affected by"the ampli tude of the im; pressed variation .currents, such as'the signal, since the term A: doesmot' appear in the term A. v It-may be noted hoivever, that the erm A is.dependent/Jeannealso the other cocfii'cicnt-s of cqua.t-ion (6),-);'uponJthe value of 71, soithatanjn change"in sti'ucturc or adjustment,rcsultingin a new/value of [thus the ellectof changing the value of the coctiicicnts of equation (6).

The second term, A cos pt.'indicates a sine wave component of flux having a he for Ko A for BEQT AVAlLABLE COP\6 =K(1 +k cos gt) (Z Z cos pt+ 6 .cos Qpt-h cos 3pt+ (5) By equating coefficients, itis found that:

a sine ,ah 107i 35h r m m 719 171. 1571 56h 2+? si -m and so on, the other I) .coefiicients being in each case expressible in powers of the h coefficients which are odd 'or even according as the subscript of the respective b coefiicicnt is odd or even. p

By expanding nation (5) and writing A 12 etc., and B for Kiel) B for Kit-b etc., and also writing (7)) for cos pt etc., we have:

quency equal to the carrier frequency. This term 15 not a linear function of 11, since by referring to the expression forb it will be seen that its equivalent involves the odd powers of h. ,The other terms in A represent harmonics of the carrier frequency and are also. not lineaf functions of the amplitude of the reluctance variation h.

TheB terms all contain the first power of k and are, therefore, proportional to the amplitude of the impressed variation component or signahsuchjas speech for example} A highly important advantage in the system of modulationjof the invention is to be seen =1 in the fact that there are no powers of (cos I in equation (4) so that in equation (5) there are no terms containing multiples of q'. 1 This'signifies thatthere arcno harmonies of the signal frequency "not: modulation products corresponding to :such harmonics' If 'the sigrnalwave were of the form L, cos g t+k cos g. .t+j equa tion (4) shows that there would be no terms containing products-of the signal components. This signifies that there will.be no intermodulation' of components in the signal wave so that, where the signal wave consists of anumber of components as in speech, the modulating system of thc inventionis free from the distbrtion commonly present in modulatorcircuitsdue to interaction in the modulator-between the various signal components.

"lThe-fi'rst of the]; terms, B cos r 15, corresponds to thc imprcssed signal frequency.

Since the expression'forjthis term involves b, the amplitude of the output signal is dependent upon the value of 12,. So long as no adjustments or structural changes are made (ora k 7:

BEST AVAlLABLE COP".

resulting in a different value of h, therefore,

the modulating systcmacts like an ordinary transformer for the signal component, the efficiency of which depends upon the reluctance of the core.

The second of the B terms, l3 cos (pig), represents the two side bands of the signal on the carrier; The amplitude of these iniportant components is seen to \be strictly proportional to the amplitude of the signal, assuming, of course, that the maximum amplitude of the reluctance variation remains constant. 4

Similarly, the remaining terms indicate side bands of the signa lfion harmonics o the carrier. Since the tern! in B andrthose following involve increasingly higher powers of 71, these terms may be niaiielnegligibly small in comparison to the primary side. hands by making 71 small.

Aside from the quantitative values above discussed, it will be seen from equation (6) that the character of the output wave may be radically changed by chhnging the sign of one or both of the-independent variables it and-Jr; For example, by providing a plurality of cores and a commonmeans such as a vibrating or rotating member for simultaneously varying the reluctance in alxplurahty of magnetic circuits, it is possible "to' cause the reluctance of certain magneticcircuits to be increasing while the reluctance of, other magnetic circuits is decreasing in an exactly similar manner. This corresponds to gins It a positive sign (increasing reluctance) the case of certain of the magnetic circ'm' s and a negative sign (decreasing reluctan'c) in the case of the other magnetic pircuiis; By applying the signal windings in reversed sense to the different respective cores, the

sign of k may be revcrsedso that ii'thi'ssignbe called .positive for one arbitrary direction of connection, it may'be'called 'negative for the opposite direction of winding.

Taking one core (hereinafter designated as No. 0) as a reference core and considering that the direction of the instantaneous-- signal and reluctance variations (k, it, re-

spectively) are both positive in the case of this core, the effect of changing the sign of h or]: or both may be seen from the following table. In this table, the sign of th' various output components is givenjfoiieach of the four cases represented by the four possible combinations of signs of k, h.

Table 1.

Output. plus terms.

It is apparent that the outgoing circuit may 'be similarly or oppositely connected to any two or more of the cores. For exampte, if it he considered that the No. 0 or reference core and core No. l are employed and that the outgoing circuit is connected in series aiding as to these two cores, it will be seen that the only components which appear in the outgoing circuit are those in the upper row of the taole, grouped under plus terms, that is, terms in A, A (2p), B(q), I3 (2pig),since the terms in the right-hand column opposite the reference core just neutralize the corresponding terms opposite core No. 1, all of which latter terms are positive, as indicated in the table. If the outgoing windings were connected in series opposing, only those terms would appear in the outgoing circuit which are listed in the uppermost row of the table under minus terms. If coresNo. O and No. 2 are employed and if they are connected in series aiding in the outgoing circuit, it is obvious that the outgoing circuit will contain only the terms in A, and if. they be connected in series opposing the outgoing circuit will contain only B terms and in each case the terms will he either all of the A terms or all of the B terms respectively. If the No. 0 and N o. 3 cores are chosen and if their windings are connected in series aiding, the output circuit will contain the even terms in A and the odd terms in B. If the circuits are oppositelyv connected. the odd terms in A and the even terms in B will be obtained.

By referring to equation (6), icwill be seen that a reversal in the sign of it, without- .changingthe sign of It results in reversing the sign of all of the terms of the equation depending upon'odd powers of it. Since 7.: appears as the first power in each of the lt terms i. e. as an odd power, the effect of 'changing its sign is to reverse the sign ot all of the B terms. whereas if the signs of both Z: and h be changed, the eiieobon the B termswill be to reverse the signwf o v those terms involving the even powers of ii. The terms of equation (6) thus fall into four classes composed respectively as follows:

Irl. Terms representing the odd multiplespf the carrier without the side-bands, that is, the terms A,(p), Aflilp), etc.

III. Terms representing the speech sidel i I. Terms representing the even pmvcred llB Oi'uputnu' usums. r p l n I bands on evenmultlplcs of the carr er, and f 01 EGO-3K2? Maximum Mpg, direct speech, that is, the terms B, +I Piq) 13422119), etc. L, U r I J+ A, mong. mosey). Min is, u 5 IY. 'lerms representing the speech side 3 I Aupgtxmmsn bands on odd multiples of the earner, that All the n time.

is, the terms EJ711 17), B (3piq), etc.

- the side bands of speech on the carrier and.

From what has been said above it follows that he sign of the class I terms is unail'ected by the sign of h or-lc; the sign of the class II terms depends on the sign of h but is independent of k; the sign,of the class III terms depends on 7.: but isindependent of l1; and the sign of the class IV terms depends on both [sand it. As has been described above in connection with Table l, iii-systems cmplo 'ing two cores, it is possible by controlling the signs of IL and Z: and the connections of the output windings to separate components of two of these classes from components of the other two classes. By employing four cores, how ever. it is possible to isolate the components of any one class from the others. Thiswill be described more fully in connection withthe following description of the drawing. Referring now to Fig. 1 of the drawing, two cores 10 and 11 are shown arranged to have the length of their air gaps varied by These cores means of the tuning fork 12. are permanently magnetically polarized to provide the requisite biased condition. .-\s explained in the theoretical analysis'of the invention above, a polarizing winding and current may be alternatively employed with similar eli'cct. This latter alternativc'means is illustrated in the circ iits' eif Figs. 2 and 4 to be described. T l e-tuning fork is arranged to be vibrated automatically at some high frequency corresponding to the carrier frequency that is to be used. The prongs of the fork in vibrating'approach toward and recede from the pole faeesof the respective magnets so that the reluctance of each magnetic circuit is periodically varied at the carrier frequency rate and substantially sinusoidally. Since both prongs approach their respective field magnets simultane ously, the reluctance is decreasing for one core 'at the same time that his decreasing for the other core, so that the sign of I; is the same for both magnetic circuits. r

The cores 10 and 1-1 are also provided with windings as indicated carryingspeech cur-,

rents derived from the :IIllOIdPhOIlB circuit 13. With the reversing switch 14 in the positionindicated, it will be assumed that the dirctionsjof winding are such thatthe speech current-increases the flux in core 10 at the same timc. that it decreases the flux in core 11. The two cores therefore correspond tothe reference core and to core N0. 3 of Table 1. If then the windings in the outgoing circuit 15 .are connected in series opposing, the carrier and all its harmonics are balanced out and there is present in the outgoing circuit only the iiormal speechand on its harmonics. If the switch .16 were thrown to the other posit-ion soasito connect the out-gomgwmdings m series aiding in the circuit 15, the only components trans the circuit of'Fig. 1,

.the polarizing windings may. be dispensed outgoing win mg,

BEST AVAlLABLE COPi mitted would be the carrier and its harmonics, since the direct speech and all of the side band components would be nontralized.

In the caselirst assumed above, the windings 1'7 and 18are assumed to be connected in series aiding and the "carrier. frequency is. therefore present in the circuit including these windings and the grid andjilament of the serves as a control for maintaining the vibrations of the tuning fork 12. r The magnet 20 connected in the plate-circuit of the tube 19 serves to drive the tuning fork.

T he various combinations obtainable with depending on the positions of thc' reversing switches 14 and 16, ma v'-readily be determined by referring to Table l.

Types of modulator arrangements employ 35 ing a rotating element for determining the carrier frequency are shown in Figs. 2, 3 and 4. These arrangements possess greater flexi ility than the arrangement shown .in Fig. 1. since the number of teeth or poles on the rotating member may readily be varied to change the character of the carrier wave produced and since this type of construction pcrmits'a number of cores to be associated readily with the same rotating element. In the arrangementof Fig. 2, two'cores 5 are illustrated, each having a'spee'ch input winding connected in the circuit 23, a polarizing winding connected in the circuit of battery 24 and an output winding associated 9 with the outgoing circuit 25. The cores may V he permanentlv ma in the arrangemenfiofFig. 1, in which case with.-- Reversing switches are shown for reversing the connection-of one coil of each pair so that the two coils of any pair-may be included in each circuit in either an aid-: ing or anopposing sense. In the arrange ment of Fig. 2, the two-cores are arranged so that similar reluctance changes iareproduced simultaneously in'each of the magnetic circuits. In this respect, therefore, the arrangementof this figureis similar to that of Fig. 1.. In the case of Fig. 3, the cores are shown in such position-relative to the rotating element 22that the reluctance ofone magnetic circuit is a minimum at. the instant when that of the other magnetic cir; cuit is a. maximum. Itfwill be understood 130 that windings are to be applied tothe cores; of Fig. 3 in the same manner as shown in connection with Fig. 2.. a

In Fig. 4, four cores are arranged to be influenced by the same rotating element 22. Each core is provided with a polarizing winding, a s eech input winding and an as in the case of Fig.2, and switchesare-shown for reversing the connection of thesevarious windings to their amplifier tube 19 so that this circuit 5- gnetically polarized ass y BEST AVAILABLE COPE 1,582,044 I El respective circuits. As in the similar arrangement of Fig. 2, permanently magnetically polarized cores may be used to obviate the necessity of using polarizing windings and currentsi I One of the cores in each of 2, 3 and" 4 is designated 0' on the drawing and will be taken arbitrarily as the reference core. 111' Fig. 2, the second core bears the designation 3, at and in Fig. 3 the other core bears the designation 1, 2, 5 or 6. These designations refer to Tables 2 and 3 which show the various manners of connection to be used for obtaining particular characters of output wave. Similar designations are made of the cores shown in Fig. 4. It will be noted that in each case the core which is designated 1 3, 4 is positioned with respect to the ron tation member 22 m such a way that its re luctance changes are similar from instant to instant to those of the reference core, while the core with the other desi ation has a reluctance variation 180 di erent from the reluctance variation of the reference core.

In the following Table 2, the, first column indicates a particular meet the cores des gnated in Figs. 2, 3, or 4. p The second and third columns indicate whether the speech and reluctance variations occur in the same .sense or in the opposite sense in any core with respect to the reference core. The

fourth column indicates whether the out ut winding of any core andthatof the reefe-v ence core have their corinections to'ztheoutgoing circuit alike or reversed; The signifi cance of the last four columns is given below in connection with Table 2'.

'Table 2;

Output connections. 1-

Reversed.......-.

In this table, the column I indicates the output components representing the class I terms as defined aboveinconnection with equation (6). The symbols in column I .indicate whether in the case of any particular core. with its direction of application of k and k and with its output connection, all'as indicated, these components would tend-to aid, or oppose the same components obtained with the O or reference core. J

- themes the class IV terms. f

The column H indicates the output components representing the class II terms as explained above; The column III indicates therla'ss' III terms, and the column IV in- By choosing the proper arrangement of twd'cores with respect tocthe rotating element and the propemconnectlon between the [various coilsand their respective circuits in accordancewith the scheme given in Table 2, it IS possible to isolate the components of two classes, "and by choosing four cores, to

isolatethe components of any single class.

The arrangements that are indicated in components are given in the following Table 3 which is self-explanatory.

' Table 8.

As in Use cores. flgum To Isolate clams.

land II 0and3 c. I and III I and IV II and 1H 9 and 6 II and IV III and IV.

whu-a-lowwwww niIII I 17v 0, 2, 4, and 5 It will be understood that the rotating element 22 maybe provided with any desired number of teeth and may be driven in any suitable manner at a speed to produce the desired carrier frequency.

Suitable-filtering circuits may be connected in the outgoing circuit 15 or 25, such as a. band filter or a low pass or, high pass filter for suppressing output components lying in a different frequency range from the-components which it is desired to transmit.

The circuitswhich carry speech currents shouldhave low impedance to speech frequency currents and high impedance to currents of the frequencies not intended to traverse them. Similarly the circuits for the carrier and side-band components should have low impedance for currents of these frequencies and high impedance for speech fre u'ency currents, i

I e inventlonflis'not to be construed as I limited to the specific circuit'arrangements shown and described but only by the scope of the appended claims. What is claimed is: x 1. The mthod of modulation comprising varying'the magnetomotive force of a magtain.components and to transmit certain othcr components of the modulated wave to the outgoing circuit.

7 3. The 'method'of generating a sidehhn'd comprising setting up a magnetic field vary- 70' Table 2 to be used for isolating any desired ing in accordance with a range of frequency components, independently and mechanically varying the field strength at a carrier frequency rate,and utilizing the resultant flux to neutralize certain components and to transmit certain other components of the modulated wave to the outgoing circuit.

4. The method of selective wave generation comprising producing simultaneous reluctance variations in a plurality of magnetic circuits, causing the resultant flux variations to set up voltage variations in an outgoing circuit, and'utilizing the resultant flux variations'of one such magnetic circuit toneutralize in the outgoing circuit certain components set up by the flux'variations in the other ma netic circuit.

5. In a modulating system, a magnetic circuit, means to vary the magnetomotive force of said magnetic circuit in accordance with a modulating wave, means to vary the reluctance of said magnetic circuit at the frequency of a wave to be modulated, and means for utilizing the resultant flux to neutralize certain components and to. transmit certain other components of the modulated Wave to the out oing circuit.

6. In a modu ating system, a plurality of magnetic circuits, means for varying the magnetomotive force of eaclr of said circuits in accordance witha modulating wave, mechanical means for varying the reluctance of said magnetic circuits, and means for utilizing the resultant flux to neutralize certain components and to transmit certain other components of the modulated wave to the outgoing circuit;

7. In a modulating system, a plurality of magnetic circuits each having an air-gap, means to control the fiuX in each of said magnetic circuits in accordance with a modulating wave, means for varying the air-gap reluctance of said magnetic circuits,- and means'for utilizing the resultant flux to neutralize certain components and to transmit BEST AVNLABLE COPi certain other components of the modulated wave to the outgoing circuit.

8. In a modulating system, a plurality of magnetic cores each having an air-gap, a winding on each core for controlling the flux in the core in accordance with modulating variations, mechanical means for varying the air-gap reluctance of said cores at the frequency of a.wave to be modulated, a second winding oneach core, an outgoing circuit, and connections for including said second windings in said outgoing circuit in such a. sense as to neutralize in the outgoing circuit certain of the products of modulation.

9. In a modulating system, a plurality of magnetic circuits, windings for influencing each of said magnetic circuits, means to set up signal current variations in said windingsymeans to produce simultaneous reluctance variations in said magnetic circuits at the frequency of a wave to be modulated,

and an outgoing circuit associated in common with said magnetic eircuitsi'ii a way to have voltage variations set up therein, the sense of the variations in the respective magnetic circuits produced by the signal currents; and by the reluctance variations being such that certain modulation components are neutralized in the outgoing circuit and other modulation components are reinforced.

1G? in a modulating system, a plurality of magnetic cores each having an air-gap, a winding on'each core, a microphone circuitconnected to all of said windings in common, mechanical means for varying the airgap reluctance of each of said coressimultaneously at a carrier frequency, a second winding associated with each core, and an" Jo snPH W. neuron.

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