US1674705A - Reactance neutralizing network - Google Patents

Description

June 26, 1928.

J. s. STONE REACT ANCE NEUTRALI ZING NETWORK original Filed Nov. 50. 1920 11v VEN TOR Jlm/ 560M Sim/Le B y L W TTORNE y ing application, Serial No. 427, 92,

Patented June 26, 1928.

I warren startl rennet JOHN STONE STONE, OF SAN DIEGO, CALIFORNIA, ASSIGNOR TO AMERICAN TELE- PHONE AND TELEGRAPH CGIVIPANY, A CORPORATION OF NEN YORK.

REACTANCE NEUTRALIZING NETWORK.

Original application filed November 30, 1920, Serial No. 427,392. Divided and this application filed May 27 Serial No. 112,117.

It is an object of my invention to provide a network comprising as a. part thereof a given circuit element having reactancc so that the network as a whole shall have zero reactance over a certain desired frequency range.

- This application is a division of my pendfiled November 30, 1920, for a circuit for passing or stopping a frequency band of alternating currents. In that case I have disclosed a network to be interposed between a source of electromotive force and apparatus connected in circuit therewith, this network being c e signed to present an approximately uniform high or low impedance over a certain fre quency range and an impedance of opposite character for frequencies outside that range.

In the design of such an interposed network it is desirable that the device to which the current is to be supplied from the source shall have substantially zero reactance over the intended frequency range, and in that case I have disclosed a combination of apparatus to get such azero reactance. This combination forms the subject matter of the present divisional application.

Referring to the drawings, Figure 1 is a -diagram illlustrating one embodiment of 1 forms, Lu), (T and a RS, where L stands for inductance,'C for capacity, to is the frequency multiplied by 27., R is resistance and C50 and S are the frequency function and selectance as defined in the following equations:

o i i Both of these equations have reference to a tuned circuit of series inductance L, ca-

pacity C, resistance R and resonant frequency f Of the three forms of rcactancc mentioned above either of the first two may always be reduced to the third form by supplementing it with proper circuit elements. When the reactance is of the first form, that is when it is a pure inductance reactance, the addition of a capacity react-ance in series will pro duce the third form. Again, if the initial reactance be ofthe second form, that is if it be a pure capacity reactance, the addition of an inductance reactance in series will produce the third form. And the third form represented by CCOR-S taken in connection with equations 1 and 2 is seen to correspond to the reactance of a resonant circuit having the resonant frequency f Having reduced the reactance of the circuit to this last mentioned form additional reactance is chosen and introduced in series so as to make the resonant frequency f, of the resulting resonant circuit correspond to the medial frequency of the band of frequencies over which the reactance is to be neutralized. The combination reached at this stage is represented by the inductance 51 and capacity 52 of Fig. 1. The initial reactance may be represented by av part of the inductance 51 or by a part of the capacity but as described above it has been supple mented by further reactance elements to make the combination of 51 and 52 in Fi 1 having the desired resonant frequency f In series with the combination 51. 52 and in parallel with each other are the three elements 53 an inductance, 54 a capacity and 55 a resistance. This resistance 55 is shown as the input impedance of a thermionic vacuum. tube. For the present it may be thought of merely as a resistance of considerable magnitude, and the reason for showing a vacuum tube will become apparent later The reactance of the combination 51. 52 is given by the ordinates of curve 1 of F ig. 2, and the reactance of the combination 53. 54, 55 of Fig. 1 is given by the curve 2 of Fig. 2. The abscissa: of these curves in Fig. 2 are values of the frequency function Land 01 and the ordinates of curve 1 are given by equation,

is negligibly small compared to unity the expression reduces to i a x and this reactance will exactly neutralize the reactance of' the series resonant circuit when ns x oher the pi. pose of a concrete illustration, let us assume that 0.0-l is the largest quantity which we can rega d as neg 'gible in comparison with uni Accordingly afilfi -Ob l represents the limiting value of afXf in o si le loop neutralizer, so that in this we have A-lQ OiZ. Therefore in the case of the single loop neutralizer we have these conditions: \;X =O.2 and 118 3 the latter equation reducing to /e r i 1 L where r II no.

and where (1,. L and G, are the capacity, inductance and conductance, respectively, ot the loop. The resistance of this loop throughout the band of width Will be 7 l substantially l Suliiject to the conditions stated above the esultant reactance of the whole combination shown in Fig. 1 is given by the curve 3 of. Fig. 2 whose ordinates are obtained by adding the ordinates of the curves 1 and 2.

Thus it will be seen in Fig 2 that the Whole combination is approximately of zero reactance for a. certain rangeof frequencies in the neighborhood of the freqpency corresponding to zero value for (1 Itis believed that the foregoing discussion of an example of the use of a band reactance neutral-izer will sufiiciently indicate its utility in various connections. To carry the particular example already discussed a little further; that is, to make it still more specific, the filament and grid of an audion have been indicated in Fig. 1.. The most effective condition is that in which the con ductance of this translating device made the conductance of a band reactance neutrah izor which neutralizes the reactanee 0a,, RS, of the resonant circuit with which the translating device is connected. This mode of connection is the most efficient possible. The magnitude of the reactance of a loop is not affected by the algebraic sign of the conductance G so that thetra-nslating derice may have a negative conductance in which case it becomes regenerative.

I claim:

1. In combination, a circuit, a device in said circuit having a considerable amount of reactance, a supplemental reactance to make the combination resonant to a desired frequency, and in series With said combination a band reactance neutralizer comprising an inductance and a capacity and a resistance in parallel and adapted to neutraL ize the reactance ofsaid combination at and near the said desired frequency.

2. In combination, a circuit, a device in said circuit intended to absorb energy, also another device in series in said circuit having a considerable amount of reactance, a supplemental 'reactance to make the combina; tion resonant to a desired frequency, and in series with said reactance combination aband reactance neutralizer comprising an inductance and a capacity in parallel with each other and also comprising said first mentioned device in parallel with, said, inductance and capacity and adaptech toneutralize the reactance of said combination at and near the said desired frequency.

In testimony whereof, I have signed my name to this specification thisl8th day of May, 1926.

JOHN STONE STONE.-

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