US1828498A - Oscillation circuits - Google Patents

Description

Oct. 20, 1931. R. A. HEISING OSCILLATION CIRCUITS Filed May 26, 1928 Fla. 2

a m 5 R a m EA 5 W0 5 M W H 7 p 1 Q1 MEET Z M L c 2 J A B w 6 C JEN? ATTORNEY Patented Oct. 20, 1931 UNITED STATES; TENT OFFICE RAYMON D A. HEISING, 1l'1ILLBUR1l, "NEW JERSEY, ASSIGNOR TO BELL TELEPHONE LABORATORIES, L YORK INCORPORATED, OF NEW'YORK, N. Ya, A CORPORATION OF NEW osoinnacrion cmoorrs 1 Application filed May 26, 1928. Serial No. 280,697.

. This inventionrelates to the production of oscillations and particularly to methods of and systems for the production of oscillations the frequency of which has a definite a givensource.

It'is an object of the invention to condition an electric discharge oscillator whereby it may be more easily coerced to change its m frequency byanimpressed wave. 7

Another object of the invention is to facilitate self-synchronization between an electric discharge oscillator to becontrolled .and a' controlling source. v, 1 a w RBy self-synchronization is. meant the change of energy, such sources tend'toproduce wavesha-ving the samefrequency, that is, one'source, the controlled source, is pulled into step withthe other, the controlling or reference source. 'The controlling source is not necessarily self-excited, as in the case of the more usual type of oscillator but may amplifier. It may, infact, be any circuitin which electrical variations occur and whichthe choice depending. on their relative oper-' ating characteristics was determined by the constants of their electrical-elements. Applicanthas discovered that an electrical discharge oscillator, or any oscillator Whose frequency is determined by the natural frequency ofv a resonant circuit, may be more easily coerced tofollow' the variations of; frequency of a circuit tending .tOz control it;

if a resistanceis inserted in such frequency determining circuit. The resistancewill be especially efiicacious f connected, to the output electrodes, that. is, across or in parallel,

;;With the frequency determining circuit in relation to the frequency of the current from phenomenon by. which, when two sources of, waves ofapproximately the same frequencyare juxtaposed so as to admit ofan interbeseparately excited as in thecasef of an stead of in series with said circuit. In such a, positionthe resistance modifies the impedance :as a whole presented to the output current of the controlledoscillator in such a ma merthat such impedance will remain constant when, for example,'-the frequency adjustment of the. controlled oscillator is varied. ,7

The principle of the invention is applica ble in any situation where self-synchronization may occur. The necessary conditions arefsatisfied in part if each' of the two frequencies generated by theoscillators are expressible by rational numbers, or in other words, if there is a rational fractional relationbetween thetwo frequencies. An irra-- t1onal number,somet1mes calledan incommensurable number, is one which cannot be divided by any other I without a.- remainder, or, perhaps more simply defined, which cannot be expressed" as'either an integer or as van integerand a decimal having a fi-, nite number of places. =.-'The quantity {i is therefore irrationall The quantityand the,

quantity indicatingthe base of the natural system of logarithmsare irrational numbers. Between any two rational numbers there is an infinite quantity of irrational numbers. Strictly,.the expression. ,irrational quantity should perhaps be used instead of irrational number since a quantity which can be expressed in strictly numerical. form cannot be irrational and the so-called irrational numbers; are really expressions of ancoper ation on some othernumber like Referring'again to'the matter of therelation of frequencies, as a practical matter, of course, the frequenciesof'the two oscillators should havea very simple relation, other wise there would not'besufficientycoercive force. For example,- "frequencies like 3 and 7 coul'd'be synchronized only if the oscillator tobe coerced was. designed to be very sensitiveto coercive influences. Ifits frequency w'erei'ohanged, it would very easily snap away from the frequency. of they other oscillator.

Inthe. case-of two. frequencies which have several common multiples, it might be possibleby verycareful design .to synchronize them by using the higher common multiples, but if one oscillator attempted to change in frequency enough to make a lower common multiple effective, the oscillators would find it y t p k he ne elat q 9 b aau i ea as s aq a d we be held together more strongly than before. Another requirement is that at least one e the we. enerator mast have. a. ie -l nea ha fa t t sticl that is. it must har med tlating characteristic. There can be no coercion in the absence of such acharacteri stic,

The invention may be more fully understood from the following description when read in connection with, the accom anying drawings, Figs. 1 and f which il ust'rate' two alternative circuit arrangements embodyi-ng the principle of the inifention,

' In the system of 1- the oscillator ind'i cated general-1y byreferencenumeral l is p'nllec'hinto step with oscillator 2 through coercion transmitted throug the transformer 3 which couples the output circuit of oscillator 2 with the frequency determin-, ing circuitLg, L Gof oscillator l. The oscillator 2 typifies any circuitcapable of exerting a coercive force. on, the oscillator 1: andtherefore mayalternat-iyely be, for egample,'an amplifier separately excited by an; oscillator of any type whatever. relation of; the two circuits 1; and- 2 corresponds to that which is commonly; described" as adapted 'for self-synchroniiation of two sources immediately or remotely coupled in this mannerf-The condition ofselff -synchronization' may be satisfiedan equality relation between-the two frequenjes concerned or they-may be related harmonically or, even more generally, they may have any rational fractional rela'tion As anecessar-y. preliminary condition, the two coupled cine cnitsr must be adjusted soas to separately generate frequencies closely approximating those which they will eventually generate; when selfisynchronizedz- The. oscillator cir,cuit- 2is representedms a. conventional: type oftelectric discharge oscillatoncharacterized by a'capacitive coupling between. the. input and outputcircuits of the 9 associated, electricdischarge-device, in this-- instancethe device-.4; thiscouplingheingconstitutedhyrondensers Q1 andzGa. Theirs-1. qua it -L det rm ning; rsuin e ich both h 'flnslfi last; i ui n ust;. e 5;; nected and: to which they, are connected, throu h th i kigy-vqq lldensers, is constituted, y steam an aid, aaass raa5 C The oscillator-:isleasily recognized to f e pi t yp s'ki le d 's is U 6Q Pateiit 1,( 324,537, granted April 12,1927

The grid o flthe' enema dischargedevice isi given a definitenegative polariiing potential? by resistance Ri ifi a well'known manner.

The anode, or plate, ofsthe device is supplied 6;; witlr direct; current potential from source Eg through inductance coil L which functions as a choke coil to prevent the flow of the generated alternating current in the direct current late supply leads. By-pass condenser provides a low impedance path for the alternating current in'st unt to the plate current source and said choke coil, the choke coil and by-pass condenser therefor t0 her westit timgs n fie t. a lter- .ha oscillator lisotthe n sltpul i typ and closely approximates the circuit disclosed in 5 of; British patent to Eccles et al. 149,018. Considering each of the two included vacuum tube devices 5 and 6 separately so far as concerns its relation to the remaining circuits, the circuit approximates a conventional form of the; Hartley oscillator as disclosed, for enamels, in his U; S. Patent 1,356,763, granted @cob'er- 26, 1920'. It is characterized principally, and therebyis principally distinguished from the Colpiltts oscillator above described, by an inductive coupling between the input and output circuitslof the associated electric discharge device; in this instance, each ot' the devices 5 and 6. This con p-lin g is efi'ected throughinductances-L and: L 'which, with condenser- G constitute the requisite frequency dame mining circuit. The circuit is completed from the-input electrodesof thedevices 5-iand g (i-tothe-correspondinginductancesIL and ll l respectively by con densers 373 andl C respectively. The input electrodes are gi ven asteady negative bias by leak; resistances R3 and-R1 similarly as in the case of: oscillator" mo 2, Theanod'es, orpla'tes, of theelectricdischarge-devices 5"-and'i6*-are supplied with direct currentr potential from source E through circuit 7; and the frequency deter-- mining. circuit. The-wave generated by: the 105 above described system. ofself-synohronized' circuits isde-l'iveredto-the utilization circuits, not illustrated, by circuit 5; The cathodeszof theithree electric discharge devices, tWof-on oscillator -11 and-i one for oscillator- 2, maybe 119 energized; in: an'yrmanner conventi onali with electric-discharge devices generally; In or.

der. toavoid; unnecessary complication. such. IDEELHS.EITBJlOtrlllllStl'fltfidi The-invention particularly-relates to.tl1e function Q/fi' resistances; R shown connected 1 acrss the, frequency determining; circuit of: theraptrolleds oscillator l; The) theoretical: reasonsiortheiactionrofethe controllingzwave in-.pulling-theicontrolled a oscillator.- intozistep with itsnivn frequency, or similarlytin' coerc ing-i it into-having afrequencywvhich issin tegrally; commensurablyrelated to the he. quencyof the controllingwave, is-more-oriless obseureandineapable o-f-simple mathjemati cali analysis A theoretical analysisofthe reasons 3 whereby--- the presence of resistances snclras It; facilitate the process is not; any" lessobsoure ordiflicult of simple-explanation; However, probably the result of using such 13M resistances is to change the controlled oscillator from onehavlng a vlgorous or strong osclllatory characteristic to one having a less with itself.

In a particular situation in which the circuit of the invention has been used these resistances have taken the form of a plurality,

of the order of 4 to 6, of incandescent lamps of a normal 50 watt rating, although any other type of resistance on the same order of value, that is, 1000 ohms or thereabouts, may

equally well be used.

connected to the frequency determining circuit at its mid-point as illustrated, there may be practical advantages in so doing. For example, for very high frequencies it may quite easily result, in the absence of such connection, that the middle portion of the resistance as a whole,for example, a middle lamp, might be substantially short-circuited by its distributed capacity, so as to no longer be elfective as a resistance. The connection as shown would obviate that difiiculty.

vof its elements, have a relatively high im pedance and certainly an impedance large as compared with that of the resistance which therefore would principally determine the output impedance. Accordingly any slight variation of the circuit conditions affecting the frequency determining circuit as a variation of the oscillation frequency by variable condenser C would not appreciably affect the impedance as a whole presented to the output circuit of the devices 5 and 6. This positioning of the resistances accordingly stabilizes the operation of the circuit.

It should, of course, be understood that the invention is not specific to the particular type of oscillator illustrated or that a pushpull oscillator must, or preferably should. be used. As a matter of fact the particular type of oscillator is immaterial so long as it is of the type characterized by the use of a frequency determining circuit. Also it is immaterial as to the circuits connectedto the output .of the. controlled oscillator. such oscillator can be usedto excite furtherelectric discharge devices, such as oscillators or amplifiers, or maydeliver power to'an antenna or .to a transmission line by. coupling in any suitable fashion. When the frequen- .cies of the controlled-and controlling oscillations are to be made the same, a possible resultant compromise frequency may be avoidedloy the use of an electric discharge amplifier or other unilaterally conducting device between the-controlled and controlling circuits. l The circuit illustrated is. therefore bestadapted for the condition' in whichlthe frequencies are unequal as when one is a harmonic of the other. Although the mid-point of the series ar-- rangement of said resistances need not be self-synchronized system embodying the principle of the invention. Reference characters. used in this figure represent circuit details which are similar inconstruction and function to those having thesame identification in F ig. 1 and these details therefore need not be considered again in this instance. The only substantial difference between the circuits of the two figures relates to the method of coupling the controlled oscillator with the controlling oscillator or circuit. Fig. 2 illustrates the case, alternative to the corresponding case illustrated by Fig. l, in which the coupling is effected through the input circuits of the controlled oscillator. This arrangement is perhaps to be preferred over that of 1 when used with relatively low frequencies since greater control is obtainable. Especially when the oscillation frequencies are harmonically related a condenser, as illustrated, connected across inductance L the resultant resonant circuit being tuned to the controlling oscillator frequency has been found to be of considerable assistance in the pulling-in function. The coupling is effected through inductance coil L included in the output circuit of oscillator 2 and inductances L and L which are magnetically related thereto and included respectively in the input circuits of electric discharge devices 5 and 6 of controlled oscillator 1. r

If the introduced controlled frequency is the same as for an odd harmonic of the controlling frequency the phases of the potentials impressed on the grids of the respective tubes should be opposite and the polarizations of the windings of inductances L and L should be such as to bring about this result. If the frequency of the oscillator is an even harmonic of the controlling frequency the polarizations should be such that these phases are alike.

It will be obvious that the general principles herein disclosed may be embodied in many other organizations widely different from those illustrated without departing

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