US1545607A - System of wave distribution - Google Patents

Description

July 14, 1925 1,545,607

J. C. SCHELLENG SYSTEM OF WAVE DISTRIBUTION Filed Dec. 22, 1920 Patented Jul 14, 1925.

UNITED STATES 1,545,607 PATENT OFFICE.

JOHN G. SOHELLENG, OF EAST ORANGE, NEW JERSEY, ASSIGNOR '10 -WES'I.EBN ELIO- TBIO COMPANY, INCORPORATED, OF YORK.

NEW YORK, N. Y., A CORPORATION OI NEW SYSTEM OF WAVE LDIS'IRIBIIT'IIIION.

Application filed December 22, 1920. Serial No. 482,460.

To all whom it may concern..-

Be it known that I, JOHN C. SCHELLENG, a. citizen of United States, residing at East Oran e, in the county of Essex, State of New ersey, have invented certain new and useful Improvements in Systems of Wave Distribution, of which the following is a full, clear, concise, and exact description.

This invention relates to a system of wave distribution and particularly to an oscillator circuit arrangement for supplying variable current at constant frequency.

The particular object of, the invention is to provide, in a high frequency system which includes an oscillator, a means for preserving the constancy of the frequency of the oscillations under varying conditions of load or tuning in circuits associated with said system and deriving energy therefrom.

A further object is to provide a means intermediate an oscillator and an energy absorbing circuit which renders the frequency of said oscillator independent of variations in load or tuning of said energy absorbing circuit.

.A still further object of the invention is to provide an amplifier of a particular type between the oscillator and work circuits to prevent reaction therebetween.

The invention has application in a system for the generation and distribution of electrical energy in which an oscillator of the generic type in which the frequency of the oscillators is determined by the electrical constants of an oscillatory circuit associated therewith is used. In this general type the energy is transmitted from the oscillator by means of an oscillation circuit, to which the work circuit is related by a coupling to either the inductance or the capacitance element of the said circuit. In either case the associated work circuit, in effect, is a part of the oscillation circuit, and its electrical characteristics contribute to a determination of the natural period of oscillation of the circuit as a whole. For example, the work circuit may be, and usually is, inductively related to an inductive portion of the oscillation circuit of an oscillator. The inductance in this related work circuit enters as a factor into the term which expresses the musim lified circuit of a transformer. Obvious y, any change in the electrical conditions in this related circuit will change the fundamental. frequency of the system.

'In many arrangements of this class, an amplifier -1S Inserted between the oscillator and the energy absorbing device or circuit,

the oscillation circuit of the enerator being coupled to the input circuit of the amplifier tube, the load being included in the output circuit. Any change in the load circuit as, when the tuning of this circuit is changed, results in a change in' the input impedanceof the tube, and hencein a variation of the oscillator frequency. That a change in the load, Whether of degree or land, effects a corres onding change in the input impedance has been demonstrated experimentally. A report of this, together with a mathematical analysis of circuit relations, may be found in Scientific Paper No. 351 of the U. S. Bureau of Standards.

This change in frequency can result from an increase or decrease in the loading of a power amplifier, a Variation in the resistance included in the load circuit being at-' tended by a corresponding change in the inductance always associated therewith. Or, the output circuit may include a closed oscillation circuit of a radio transmission system interposed between the amplifier tube and the radiating or antenna circuit. Such a system requires for eflicient transmission as well as the antenna circuit, should be tuned to the high frequency that is being transmitted. In this case effortsto tune the oscillation circuit associated with the output of the tube will result in a change in the transmitting frequency.

The invention is designed to avoid the variations in oscillator frequency consequent upon any change whatever in the work circuit associated therewith, the examples given above being illustrative, only, of a large number of possible applications of the invention.

The method of the invention consists, in part, in causing the output circuit of the oscillator system to have very small, or substantially zero, impedance at the oscillator frequency. Under these conditions, a relatively great change in a component impedance included in the output circuit will produce no effect on the input impedance of a the tube and hence on the frequency of the oscillator. This result is accomplished by causin the output circuit, or a portion thereo constituting the work circuit, to be tuned to a higher frequency and by transmitting at this higher frequency. To this end the amplifier is of a particular type in which the product of amplification is a distorted wave containing a first even harmonic havin a relatively great amplitude. The output circuit is tuned to this harmonic frequency which thus constitutes the frequency which is characteristic of the energy to be supplied by the generator unit as a whole, this unit consisting of the oscillator am lifier tube, and associated circuits. If desired, a filter circuit which is resonant to the oscillator frequency may be placed in shunt across the output circuit. In either case there is substantially a short circuit path for the current of oscillator frequency and any change of condition in the work circuit, involving slight change in tuning to the higher frequency, does not affect the impedance of the output circuit to the lower fr uenc The oscillator is accordingly undistur ed by normal adjustments of the work circuit.

For a more detailed disclosure of the principles of the invention, particularly as relating to its practical embod1ment,referenoe is had to the description which follows, taken in connection with the accompanying drawings, in which Fig. 1 shows a system broadl embodying the invention. Fig. 2 shows t at portion of the system of Fig. 1 included at the right of line 11 as applied to a specific use; and Fig. 3 shows a system of Fi 2 provided with a filter circuit.

fieferring to Fig. 1, the system as a whole consists of an oscillation generator 0, the amplifier A and the load circuit C, the load circuit being capable of being tuned to a definite frequency by the means shown. The oscillator O, as has been pointed out, may be any one of the several types characterized in common by an oscillation circuit associated with the primary energy source which at the same time effects the necessary coupling between the two circuits for transfer of energy therebetween, and determines the frequency of the resulting oscillations. An example of a type of oscillator conforming to this generic princi le is found in Hartley Patent 1,356,763, ctober 26, 1920.

The amplifier A differs from the conventional type which is designed to amplify with minimum distortion, in that it combines the usual function of an amplifier with that of a harmonic producer, and hencecan be considered an amplifier in which the amplification is accompanied by relatively great distortion.

A common adaptation for using an amplifier tube as a harmonic generator onsists in overloading the tube, by which is meant that the alternating variations of E. M. F. impressed on the grid are of such amplitude as to cause the tube to operate at a critical value of its grid potential, as at or beyond the knee of the characteristic curve, with resulting periodic distortion of the output wave. Although this, or any other mode of operation which produces a distorted wave, is comprised within the bounds of the invention, it is preferred to use the other of the two general types, that in which a suflicient negative potential is impressed on the grid to bring its mean potential to a point close to the lower end of the characteristic curve. The alternating variationsin grid potential will correspondingly occur between an upper limit which may be in a region of positive potential and a lower limit which is very close to the foot of the curve or even be ond this point. The method of operating the amplifier as above, results in a distorted ,space current wave in which is contained a relatively large component of the first even harmonic. This function results from the fact that a negative polarizing potential may be given a sufficient value to reduce the normal space current to a small value. a

The work circuit C is tuned to a harmonic, for example, the first even harmonic of the enerated wave. For example, if F is the requency desired, the oscillator would be designed and adjusted for a frequency F. In Fig. 2 the work circuit is shown as the closed oscillation circuit of an antenna .sys-' term, the radiating circuit being preferably tuned to the same frequency as the closed circuit by the variable means shown. The closed circuit is tuned to the harmonic frequency. Since the frequency to which the closed circuit is tuned 1s so different from the generator frequency, the impedance of the plate circuit, so far as this frequency is concerned, is very small. Hence only very small changes of generator frequency will.

occur when the impedance of the output circuit to frequency F is varied. p

In Fig. 3, an additional means is shown for insurin that the impedance of the plate circuit to 518 oscillator frequency shall be very small. The means shown is the filter circuit F, which may be composed simply of an inductance and a capacitance in series and tuned to the oscillator frequency. This circuit, in effect, is a short circuit to circuit C for the fundamental frequency and the impedance of the output circuit, as a whole, is substantially zero to the oscillator frequency. Any slight variation of the values of the elements in circuit C, as an adjustmentfor-prec1se tumng, accordingly does not affect them dance of the pate circuit to the oscillator ncy. .S umn1 nanzing-a11 of the above, the inven- 'tion in its broadest aspect resides in causing the plate circuit to have zero, or substantially zero, impedance to the currentof oscillator frequency. Since this feature taken alone, would be inconsistent with the use of the plate circuit as a work circuit, it is necessary to, in effect provide separate circuits for the oscillator frequency current and for the work current. TlllS is accomplished in a simple way by tunin the work circuit to a different frequency t an that of the oscillator frequency, thus insuring an ener flow from the system without sacrificing t e essential requirement that the plate circuit have zero impedance tothe oscillator frequency. In order to most eficiently extract ener from a system it is convenient to make fiie work circuit frequency correspond to a harmonic of the voltage wave impressed on the plate circuit, the first even harmonic being chosen since it is the most powerful of the harmonics maklng. up the com lex wave of the harmonic generator. It has een found that with the method here used of stepping-up the frequency,efiicienc1es as high as 55% can be obtained when the load is tuned to the first even harmonic.

This result amply demonstrates that it is practicable @tostep-up the frequency in this I t should be understood that, although a single amplifier unit is shown, further amphfication of the harmonic frequency may be secured by am lifiers inserted between the generator-amplifier system shown and the work circuit, and that there may be as many stages of amplification as may be desired.

What is claimed is:

1. In combination, a primary energ source and an ener absorbing and frequency determined-circuit associated there with, said circuit comprising a wave distorting means for producing harmonics of the wave from said source, and a work circuit, said work circuit'constituting-a parallel resonant path for a harmonic f uency and including a series resonant path or the frequency from said source.

2. In a system of distribution, a source of oscillations including an oscillation circuit for determining the frequency supplied thereby, an audion amplifier associated with said source and having its input circuit energized by said oscillation circuit, the mean grid dpotential of said amplifier being aduste so that the output current-thereof has a first even harmonic of said frequency of materially greater amplitude than any other harmonic, a load circuit included in the space circuit of said amplifier and tuned to said harmonic frequency, and a filtercircuit in shunt with said load circuit and tuned to resonance with the oscillation frequency.

3. In combination, an oscillation generator including an energy. absorbing and frequency determining circuit, said clrcuit comprising1 wave aving a frequency widely different from the fre uency determined by the constants of said circuit and havin an impedance at that frequency which is substantially greater than zero, and including a series path which is resonant to the determined frequency.

4. In combination, a primary energy source including a frequency determining circuit, an output circuit, and means between said source and output circuit for deriving harmonies of the wave from said source, said output circuits comprising means for officiently transmitting currents of a harmonic frequency and having an impedance at that frequency which is substantially greater than zero, said output circuit also comprising a series resonant path for the frequency of my name this 17th day of December, A. D.

v com: o. SCHELLENG.

means for efficiently transmitting a

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