US1815838A - Negative capacity device - Google Patents

Description

u y 9 M. M. DOLMAGE 1,815,838

NEGATIVE CAPACI TY DEVICE Filed June 27', 1929 Fig. 2

Frequency Of.Curre f' Fig. 3' flood WW WLJNVENTOR latented Julyjzll 1931 .l r 1 315 33 1 Z 1PATENT orifice 5 current is involved, it is well know ithat the-jout the method. Essentially, according to my MIHRANIVLDOLMAGE; or wiisamewbn-niswmew OF coLUiviBiA QNEGATIVE'CAPACITY DEVICE' "A i c fi n i i i ne 27 1929. Serial m. 374,084.

This invention relates"toa iewcombination This invention relates to'the discovery of a in tl e electr-ical art,va negative capacity; 7 method for obtaining what can be properly Jill-161%, in an electrical circuit or a transcalled a negative capacity. Full disclosure finission line, a single" frequency alternating is made herein of themeans "required to carry i oppositionofieredto'the fiowof electrical curdefinition ofit, a negative capacity is a device rent bye-condenser in-the electrical circuitor which, inits effect, when interposed in an .bya capacity in the transmissionline nay be electrical circuit; is the exact counterpart of offset" by an inductance. The i elief-thus oban'ordiiiary capacity for the entire range of V :0 t ained may be partial or complete depending frequencies from practically Zero to practi- 55. i

*on the relative" dimensions of the inductancev cally infinity. The re'actance of such a device and the condenser.-

may be expressed bythe relation f To make thispointperfectly-clear consider W l 1 acircuit containing in series a condenser of I (2) R c i g: l 15 capacity C, an inductancehfa resistance R, I I P J d g 3 le r e tl e the corresponding expression for the react 03 equal to E S111: -2 n such 9113 1 he mice ofan ordinary capacity being Y reactanceof the condenser s equal to' p f 1,. I pOI it I .7 Assumingsiicha negative capacity C) 7 The reactance f lp uqt l to have been wired in series with an ordinary Th e H Q m Ph3 PPQ condenser (+0) in an electrical circuit pnr e total n reactanoelofthe clrcmt wherein acts an electroinotive force of he I e v nb j v "1 quency p I Reactancj LE- .F? P r 21v Clem-71y the er ir fifi for which vit follows immediately that th 30 the two reactaiices; the capacity reactance and the inductive reactance,' are equal y to each otherand the resulting total net reactance is A 1 I 1 I [z -r1 a I T QEQ I lVhere howe'ver a number of frequencies v I a 1 I I n I have tobe transmitted simultaneously, which Hence in such a circuit, f a number of: g is-the generalcaseinsignalli ig circuits both electromot ve forces having different frequcin a wireand wireless,thedifliculty in inediately 'cies (instead ofa single frequency electroino--i I rises' that ifthesignalling circuit is'tuned to t ve force) wereiactive, the reactance of the. v V someone frequen'cmall'other frequencies'are CIICUItfWOUlCl be ml for all frequencies and f 4.0? adversely affected: As aninstance, in wire-- therewould be no discrimination as between; less receiving at the presentstage ofthe; art diiierent frequencies. To put this in another it is necessary to have recourse to so called Way, we would have realized a distoi'tionless .lo'osetuning to avoi'd the undue reduction circuit This is obviously true since relation of either the, ma'iiiica'rrier wave or the 'mOdI1' (45) holds regardless of p. The practical im- Y e ,la ted carrier waveoribothf 7 v portancein signalling workifof a negative v e net'reactance' in this'circuit would'beequal to 75 capacity, having the characteristics hereinabove'outlined, is too evident to require com- 7 case will be the same for all frequencies.

'The reactance of thus givenby ment. 1

"Itshould be understood, of course, that instead of complete neutralization of the negative reactance of the capacity, we may arrange for partial neutralization if we so desire. The relative neutralization in such a If, for instance, we wish neutralization of thenegative reactance N e i of the capacity C in-an electrical circuit, then the combination of the negative reac'tance of thegiven capacity and of the positive reactance of the negative capacity device will be It is necessary and sufficient, in order to realize the above purpose, that the value of the negative capacitybe equal to (5) WWW- a The important point to note is this, that: whileneutrahzation of capacity reactance 1salso possiblethrough the use of ordinary inductance, such neutralization is not equally effective at all frequencies. 7 If it is 100% at some one frequency, so that for that frequency the net 'reactanceis zero, it will be only 25% vfor half of that frequency, ,This is evident since, if series inductance is used for neutralization purposes,

' cuit is given by Formula (1) hereinabove. If,

as stated, for some definite frequency the above reactancc is equal to zero, then:

1 L 1 p 0 Now, for half the above frequency, the secondlt erin in equation (1) ,WhlCll term expresses capacity reactance 1n ohms, is twice as large,

7 while'the iirst term which expresses the re- 'acta nce of the inductance 0011, is only one-half in-value. 'Assume that for'the original frequency, the positive 'reactance (pL) is 1,000 ohms and the negat1ve reactance of the capacity is 1,000 ohms. The series combination [0r theabove will have a reactance which would beOohms. The negative reactance for one-half frequency is-evidently 2,000 ohms,

while the reactance of the inductance is only +500 ohms. The net reactance of the series 7 the series combination is.

the net reactance of the circombination. is 2,000+500, or f 1,500 ohms. The neutralization which Was'1'00% forthe frequency as originally assumed is now only 25% for one-half of that frequency. The opposition oifered to the flow of current through an 7 electrical circuit containing a condenser.

, and inductancecoil would be, as shown above,

Oohms for the neutralization frequency. It is 1,500 ohms for, one-half frequency.

This brief description gives'a'clear idea of the distortion that is produced when capacityreactance is used in series with a-ninductmice when a number of different frequencies are to'be transmitted simultaneously over any given electrical circuit In commercial practice, this situation isof common ocurrence, for instance, inithe case of telephone circuits wherespeech frequencies varying between :1

- few hundred cycles an'd5,000 cycles are transcapacity wired in an electrical circuit.

7 The discussion given above for series neutralizationiof the reactance of a'capacity by means'ofnegative capacity as compared to similar neutralization by means of an 'inductance coil, also holds truefor parallel neutralization, or parallelluse of a" negative capacity with an ordinary capacity; a

The method I have discovered-to realize the object of this invention is, briefiy, to use in 7 parallel with a negative resistance a combmation comprising an ordinary positive resistance having thesame absolute ohmic value 3 as thenegative resistance, inseries with an inductance. The value of this inductance is to be chosenm accordance with the rules indicated below.

The novel' features of my invention are pointed out in the appended claims, The invention itself will be best understood byreference to'the drawings and the discussion given llGI'BlIl'bQlOW.

Figure 1 of the v drawings shows; the general ideaunderlying the useof' my method- Figure 2 shows a particular method of carry- 7 ing out-my invention'using as a negative resistance the type of circui-t and'apparatus covered in U. S. A; Patent'No'. 1,606,350, granted to me." Figure 3 shows in dotted line the reactance in ohms of the negative capacity device discovered by 'me'in function of frequency.- As a matter of interest, the corresponding reactance of an ordinary inductance coil is shown in: full line. It will be seen, at a glance, howxdifferent the-two are.

where ji's the usual imaginary factor this reactance decreases asfthe frequency in creases, while ,foranordinary inductance the 'oppositetrend holds, as shown on said Figure f 3. Furthermorathe reactance' Variation of 1 the device disclosed hereunder is inversely proportional tothe frequency, while in the case of an 'ordinaryinductance thereactance, 'fisdirectly proportional to the frequency. 7 The arrangement of apparatus" connected across terminals 1 and 2 represents a-negative"? capacity within the meaning of the word as defined'previously. Element 3is an ordinary resistance; Element lis a negative 1 resistance; It may'be of any type known'to.

theart; "In parallel with, this element are wired, in seriescoinbination, a resistance ('ele eme) and an inductanceiflelement 6). I Figure2 shows, apreferred tormof nega tivefresistance for element l of Fig'ure 1 of the drawings It is represented by. the combination ofapparatus connectedto terminals 7 'and & Thistype of negative resistance has been disclosed-in U.

granted tofme. I p 1 :Tosho'w' how eifectivelyfthe combination a shown realizes the requirements for a-nega-f itive capacity, as defined above, consider the arallel 1 combination of elements 4, 5 and 6, sing'the usual imaginary notation, the expression is s, A. Patent 1,606,350,

mathematical] expression "for the I Developing fully' the real and imaginary terms of the'above gives theffollowingrela- [The first item ofthe above expressionis a 7 negative resistance; ,Thesecond or imaginary term represents a positive reactance, and -is ofopposite sign to the negative reactance ofan ordinary capacity. urtherfore, it'can i written the form I v e V? iltisseen from the'eirpression as ijust Written that the reactance of this new device is in} i verselyproportion'al to (p) and thereforein versely proportional to the frequency of-the just assente we can write as value ofthe" parallel impedancefof. elements I curaene'einsmiee'ar rmi ig u a asiii the present specifications, theabsolute value of case of the reactance off-anjordinary capacity. But,'-it'has-thel opposite sign 1+) insle'adqof the" minus I as fhereinabove assumed for J the rea'ctance of an ordinary capacity. New

andf(L;);in the above expression are anything we choosei V e can, thereforefif we} wish to secure a negativecapacity of predetermined Value -13), so choose the above values (l t) and'(1L) that I We can secure, .therefore,.the valueofthe tal Equation (8), It should notedthat (l3) ,;i,s" te m na and m y be, es chosen so as to secure convenient'or practical valuesfor the reactance requiredftd jrealize predetermined positive reactance e* edie;;, 1 v a. ff ifThefoinbination ot element tilve resistance 'R) with the parallel impedance of elements4, 5 and 16 asjustiiwritten" hasian 1 an: impedanceieq'ual to a; ngs, istherefore 'given by a,

a negative'capacifty i n the true sense I of the "follows x .9 a

, ve Thgimpedance-ofthecombination of apparar i tus conn'e'cted 'to terminals term." This ,entirely'new 1 device in the art,

no matter' what- *the -it'nzcpiency factor it p) 1 acts exactly likea capacity, so far as he quency variation is concerned, but otherwise w is in exact phase opposition. If in anyelec dicatedon Figure 1 of the drawings used I tric circuit, we have 'a condenserhavinga is capacity C, the combination of apparatus'in- I in series with the condenserG will wipe out" completely the reactive ;efiect of this conrent which may be transmitted through such a circuit. I

denser regardless of the frequency of the cur-f I a a a A very valuable advantage of the arrange- 'menteshown on the drawings is the ease with v which the value of the negative capacity e i p be "changed; To obtain a change it is sufiicient to change the value of the resistance elements shown on Figurel or Figure 2, with-e I ,1

out changing the inductance element. 'All the resistance elements must be changed the [same amount. If the variousresistance elements are changed by the same percentage,

element (6) of the drawings from fundamen- 7 i $31107 the capacity willhave changecl in k accordance with the square of such change, or} 21%; This will be'clea-r by referenceto Formula, OrQWe may leave the resistance elements -alone,- and change only the value, of inductance (6). In this case the variation ofthe value of the negative capacity 7 is directly'proportional to the 'Va riationin 4 the value oftheinductanee of element 6) Iclaim:

- 1. An automatic device having reactance characteristics of;0ppositesign to that of a I capacity, such reactance varying inversely With frequency. 1 V r 157 2. A-tWo terminaleIeCtriCal network consisting of a negative resistance, inparallel with a combination, of. a resistance and an inductance in r s'ries'f relation, said parallel I arrangeinent'being wired in seriesiw'ith a .re-

3L'An automatiefdevice ha ving reacta iice characteristic-ofopposite sign to. that of ar, capacity, "such-reactance arying inversely with 'fr,equeney," .jvit'h additional meansfor varying'the value of said reactance in' equal J 7 i i I i V proportion forall frequencies.:-- T 4; In an electrical network;.oontaining at condenser, automatic means-for the partial V neutralization of said condenser to the flow 3e of'currentthr'ough said.neiwvork,equally ef-' fective for all frequencies v 5. lnanelectrioal network for the -simul-' taneous tra'nsmis'sion of a band of frequen- 'cies, containing a condenser; automatic means for the complete neutralization ofsaidcon- ,denser to theflow of current through said 7 network, equally effective for all frequencies." I

'6. In an electrical "circuit containing a Condenser, automatlc means for neutralrzmg 1 p, the eflect ofsaicl ondenserto'the flow of 1 current through said circuit; such means being equally. effective "atall frequenciea 'lntestimony hereof-I'aflix iny signature. '7

MIHRANMJDQLMAGEE ,2

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