US1539402A - Means for producing electrical oscillations - Google Patents

Description

May 26,\1925.

1,539,402 H. W. NICHOLS MEANS FOR PRODUCING ELECTRICAL OSCILLATIONS Filed Feb. 24, 1919 by MW Patented May 26, 1925. v

UNITED STATES PA 1,539,402: TENTOFFICE.

HAROLD W. NICHOLS, OF MAPLEWOOD, NEW JERSEY, ASSIGNOR TO WESTERN ELEC. TRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A GOjR-PORATION OF NEW YORK.

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Application filed February 24, 1919. Serial No. 278,573.

To all whom it may concern:

Be it known that I, HAROLD W. lflioiions, a citizen of the United States, residing at Maplewood, in the county of Essex, State of New Jersey, have invented certain new and useful Improvements in Means for Producing Electrical Oscillations, of which the following is a'full, clear, concise, and exact description.

. his invention relatesto means for producing electrical oscillations. More particularly, it relates to the means for controlling the frequency of the oscillat ons produced by generators of the feedback or reaction amplifier type.

The object of the invention is to provide an oscillator having non-resonant means for determining the frequency of the oscillations generated.

i It is well known that if the output c rcuit of an amplifier be connected with the input circuit, of the same amplifier, or if means be provided for feeding back energy from the output to the input circuit, oscillat ons will result if certain necessary condit ons are present. Ordinarily, an electric discharge amplifier having its output c rcuit reactively coupled to its input circuit is used, and the frequency of the oscillations generated is determined by, the tuning of a circuitwhich may comprise parts of either the input circuit, the output circu t, or both. Where a tuned circuit is not provided, the oscillations will have a frequency depending upon the capacity of the tube itself and the associated capacities and inductances.

According to the present invention, the output circuit of an amplifier, preferably a thermionic device, is arranged to feed back energy to its input circuit, the output and input circuits both having only one kind of reactance. There is accordingly no resonant or oscillatory circuit, and the frequency of the oscillations is determined by the value of the various constants of the circuit and the amplifyingtube, as will hereinafter appear. Such a device may be termed a noni-esonant oscillator.

In the accompanying drawing1 repre sents the container, preferably highly exhausted, having the usual hot cathode 2, impedance-controlling element 3 and anode 4. A source 5 may supply heating current to filamentary cathode 2. The space current or output circuit comprises cathode 2, inductance L constituting the primary of a trans former, space current source 6 and anode 4. he input circuit comprises cathode 2, inductance L which is inductively coupled to inductance L polarizing source 7 and impedance-controlling element 3. Polarizing source 7 is not essential and may be omitted. A resistance R, is connected in shunt to inductance L of the input circuit. An asym metrically conducting amplifier 10, preferably of the thermionic type, has an input circuit connected by leads 8 and 9 across the terminals of output inductance L The output circuit of amplifier 10 includes the primary Winding 11 of a transformer, the secondary winding 12 of which is connectttl to transmission conductor'or work circuit.13. The input circuit of amplifier 10 may contain a polarizing source 14.

The physical process occurring is as follows:

Suppose the space current circuit 2, L 6, 4 is suddenly-closed. The current in this circuit will at first increase rapidly and an electromotive force will be induced by L in winding L thus bringing the impedance control element 3 to a more positive potential with respect to the cathode 2. This causes further increase in the space current and consequent increase in the potential of the control element, these increases, however, being at a slower rate as the space current approaches its limiting value, as determined by the impedance characteristic of the thermionic amplifier. Finally, a point is reached at which the rate of space current increase is so small that the electromotive force induced in the input circuit is less than before and the potential of the controlling element or grid accordingly begins to fall. Falling grid potential causes the space current to begin to decrease and the decrease of space current in coil L is accompanied by an induced electromotive force in 0011 L tending to make the grid still more negative. In this manner the space current decreases to a minimum value, when it finally is caused to increase again by a reversal in the changes of grid potential. These reversals inthe action of the impedance-control element continue indefinitely if the various constants ofthe network including the tube and its as sociated circuits are properly chosen, The space current, through inductance L accordingly rises and falls cyclically in value.

Y asse ses v Any suitable means may be used for transferring to a work circuit the alternating component of the space current energy.

As illustrated in the drawing, the input circuit of an asymmetric thermionic amplifier 10 is connected directly across the inductance L,, and the output circuit of am plifier 10 will therefore supply amplified oscillations to work circuit 13 by means of transformer 11, 12. The polarizing source 14 may be used to prevent leak current in the input circuit of amplifier 10. The amplifier 10 is a potential-operated device and acts as an infinite resistance and infinitesimal capacity in shunt to the winding L The frequency of the oscillator is independent of any oscillatory circuits or of-electrical tuning as it is commonly understood. Such an oscillator is therefore entirely different in the matter of its frequency control from those in which both the stiffness and inertia factors'determine the generated frequency.

Viewed broadly, the input and output circuits are typical of any energy transfer system in which the capacity or potential energy storage factor is negligible, and the amplifier acts as a valve under the control of said system to permit the periodic transfer of energy from a primary source of energy, such as source 6, to said system. Potential energy storage factor is a general term used to designate the capacity of a sys- ,tem, whether such capacity is due to the physical relation of the elements of the system, such as the wiring between individual pieces of apparatus, or due to a condenser as conventionally understood.

It is not essential that the amplifier be a vacuum tube device since anyasymmetric mutual impedance arrangement may be used. By asymmetricmutual impedance is meant an impedance in which the inputand output circuits or elements have such mutual relationship that the impedance of one is directly dependent upon some characteristic pf the other, the impedance of the other being substantially independent of the conditions or characteristics of the one which it controls. Such an impedance may of course where I is the instantaneous current in the mesh R L The potential '0 of the impedance-controlling member with respect to the cathode may be considered as producing a cm'responding variation V in the effective output electromotive force which will be equal to the potential 4) multiplied by the amplifying constant p. of the amplifier giv- D (2) V p/l). From and (2) it follows vzuIt I The differential equation or characteristic for the above circuit may be written as follows:

d (it the differential operator, 1,, represents the instantaneous value of space current, R, the internal impedance of the tube between the space current electrodes 2 and 4 and m the mutual inductance between L, and L The quantity V is negative in the second member of the equation for the reason that a variation of potential in the input circuit is attended with a corresponding output variation electromotive force of the opposite sign. In other words, as the potential of the cathode 2 with respect to impedance-control element 3 is increased, the effective potential of cathode 2 with respect to anode 4 is proportionally decreased.

The differential equation for the closed branch R L of the input circuit may be written as follows:

L227I1+R2I1 777'I7I2:O Rewriting (4) and (5) respectively- 1(l" 2 p)+ 2( 1p+ 1) and 1( 2+ 2I 2( l The criterion for a real solution of (6) and (7) for I and I isp 2 p) :0 The general solution of equations of the form of (6) and (7 for I and I will take the form:

The real quantity 6 represents a damping factor.

For sustained sinusoidal oscillations, the general equation (12) I=e"' holds true.

Differentiating (12)- (13) pl=we =wI and (14) pzc) Trom (11) it will be seen that in the case of sustained oscillations where the damping factor is zero (15) 0),:ifl and since from (14) Hence it appears that oscillations will be obtained when the resistances,'inductances and mutual inductance of the circuit, and the internal resistance and amplifying power of the tube are related as in (18) and the frequency produced by the oscillator will depend upon the resistances, inductances and mutual inductance as shown by (20).

It should be noted that although the elements of the tube may constitute a small capacity, this plays no essential part in determining the generated oscillation frequency, especially at low frequencies.

Although the invention has been described and illustrated in the preferred form only, it is to be understood that it is not to be limited except as indicated by the scope of the appended claims.

What is claimed is:

1. An oscillation generator comprising a work circuit, an amplifier having input and output circuits, and a network of negligible capacity electrically associating said circuits to connect the output circuits in aiding relation to the input circuit, said network and circuits determining the frequency of the generated oscillations substantially solely by virtue of the resistance and inductance thereof.

2. An oscillator comprising a network, an amplifier associated therewith, said network comprising means whereby the network and amplifier transfer energy cyclicall to each other at a predetermined periodicity determined substantially solely by the resistance and1 inductance of said amplifer and net- WOl'i.

3. A thermionic oscillation generator having an input circuit, an output circuit, and means to connect said output circuit in energy transfer relation to said input circuit, said circuits and connecting means having a negligible amount of capacity, the frequency of the generated oscillations being determined by the other electrical constants of said circuits and connecting means.

4. An oscillation generator comprising an amplifier and means for feeding back energy amplified by said amplifier to be reamplified, both said amplifier and said means haw ing negligible capacity, the frequency of the generated oscillations. being determined by the other electrical constants of said amplifier and energy feeding back means.

5. An oscillation generator comprising an amplifier having input and output circuits,

said circuits together with said amplifier constituting a network for determining the frequency of the generated oscillations independent of any electrical capacity thereof.

6. An oscillation generator comprising a network, a prime source of energy, means whereby said source transfers energy periodically to one portion of said network and said. portion simultaneously transfers energy to a second portion of said network the first energy transfer being under the control of said second energy transfer and the periodicity of said energy transfer action being determined substantially solely by resistance and. inductance.

7. A reactive network adapted to transfer energy cyclically at a predetermined periodicity, said network having electrical constants of such value that the sum of the even power terms of the differential operator in its characteristic is zero and being nonresonant at said predetermined periodicity.

8. An oscillation generator comprising an amplifying device, and anetwork connected thereto, said network comprising resistance and inductance for determining the fre quency of the oscillations generated, said network being non-resonant at frequencies of the order of the generated oscillations.

In witness whereof, I hereunto subscribe my name'this 17th day of February A. D

HAROLD V. NI OHOLS.

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