US1841281A - Stabilized radio circuits - Google Patents

Description

Jan. 12, TT 3 1,841,281

STABILIZED RADIO CIRCUITS Filed March 15, 1927 3 Sheets-Sheet l PIE L1- INVENTOR +lara/d E E/l/off %:7 AT TO RNEY Jan. 12, 1932. H. F. ELLIOTT 1,841,281

STABILIZED RADIO CIRCUITS Filed March 15, 1927 5 Sheets-Sheet 2 I m VENTOR Ham/d E f/fibf/ HIS ATTORNEY 1932- H. F. ELLIOTT STABILIZED RADIO CIRCIiITS Filed March 15, 1927 3 Sheets-Sheet 3 Opera flng Range. 550 #500 K6 HIS ATTOR Y Patented Jan. 12, 1932 DELAWARE Application. meal/incurs, 1927; ser' ;'a1 no. '1 t5;tool

This invention relates toifradio frequency circuits, and especially toelectronic emission amplifier circuits of this type, utilized in connection With telephone 'or telegraphic sig-' naling.

When electronic "emission devices are'utilized for radiofreq'uency amplification, eertain deleterious eii'ectsare noted; This-can be morereadily'explained when the nature and structure of such electronic emission devices are elucidated.

- Such devices usuallycomprise a plurality I of electrodes enclosed n an evacuated vessel.

One of the electrodes serves as a-source of electronic emission, and is'usually' in theforin of a filament heated by the passage'-=of an electric current therethrough. This-;filament Y thus forms a cathode, from which electrons flovv in the space of the vessel to'the-plate electrode, or anode that is keptata potential positive with respect to the filament, as

' aplate or B batteryJ The space cur- (usuallyin the form of a grid) canbe-placed' so as to nfluence the electron emlssion, and;

rent'hetween the plate and filament thus flows through the external battery circuit. The function ofamplificationis' rendered possible by the fact that the space-current is very sensitive to the electrical'con-tlitions in the tube; For example, a control electrode 7 the influence is a function 'of'th e potential mionic repeaters-oramplifiers, the capacity i system to be unstable. especially at-the higher crate disturbing oscillations.

proposed to utllize some form of-dampin'g, such as-resistances, to prevent thcse' oscillations; and also,-to provide "so call'e'd neutral 1 difi'erence between, it and the filaments} Thus .iinute variations in'p'otential difference a pliedbetween the grid and filamentjc'an cause V comparatively large corresponding *variaeftect between the electrodes 'may cause the fre uenciess; the in'stabilit'i is manifested b a tendency for thetubeoib repeaterg'tofgen- It has been fsramnrznnnanro oiitouirsff ei 'ooarona'rron or izing ci'r'cuits vvhiclilare fiintendedto compensate (for such parasitlo coupling. The

V HAROLD F. ELLIOTT, OF PALQ'ALT QoALIEonmA, ssI NoR, 3Y essrenii/rnnrsz I a e I TO nemoconronn'rronor. Annalee, Y on roan, N; f

dampingarrangementis"obviously imprac sharp tuning-j the neutralizing circuits need accurate;adjustmentsg z It is .accordinglybne of: theobjects of my 7 tical becauseit introduces lossesthat prevent";

inventiontoiprovid'e' :a stabilizing scheme that Y overcomes these' dlsadvantages, and'to makeit possible to construct amplifier systems in f asimplemanner, thatdonot require suchiextreme delicacy in adjustment.

'It is another object of my'invention to make it possible to feedback energy from'the, out- I i put side to the input side-of such an: amplifier system, in :order ;to: reamplify the currents and their variations, and? yet without the dangenofthe feed-back (or ,regeneratiofl as it is usually called) [becoming unstable and caus ng undesiredoscillationsr we r ,My-i ention possesses :many; otherta d tages,=and ha -other objects which maybe made more easily a parent from a considere tion of several embodiments-dimy invention. 1

For-this purpose lfhave shoyvn a fewforms 'in the' drawings: accompanying and' forming I partof thepresent' specification." I shall now J "proceedeto describe-these formsrin detail,

which illustratethegenei'alprinciples of my inventionfibut it is to beun'derfstood that this detailed description is not :tobettaken' in: a 'lin'iiting sen se,- since theiscope; of my invention isbest definedby th appended claims.

' Referring to the: drawings {Figures =1-to41inclu ive areiiwiringe diaresonant circuit, discussed hereinafter.

p In Fig. 1:I"'shoW one stageionly of my amplifier system',r but' of course-it is understood" that any" desired number can" be:.connected in cascade, "so far as practicable Also, I. have indicatedmysystem as appliedlto therecepe tion of'radio signaling'energy, but-it is not limited tothis field; ThusiI sliovv a conven' grams of fou'r embodiments of mymvention. V v i FigJ5-is a reactance'diagram of aparallel sov 'tionalf form ofpick up system, comprising nection 13; v tunable circuit .1 4, comprising antenna-'llgloading coil12,and=a groundconi ment 19 externally of the tube 17 through the following output circuit; coil 23, coil 24,

minute signaling energy and causes it to affect a thermionic amplifier tube 17. For this purpose, one terminal of condenser 16 is co-n nected to control electrode 18, and the other terminal to filament19. This filament is arranged to be heated by electricalenergy, as from a battery 20. The negative side of the filament 19 can be grounded, as indicated at 21. e

The electrons from filament 19 flow to the anode or plate 22, which is joined to the filapositive terminal of B battery 25, battery 25, filament 19. A by-pass condenser 26 can be shunted around battery25 to permit the radio frequency component of the output current to pass aroundthe battery 25. The

. signaling impulses cause correspondingly large impulses of current in this outputcircuit, which can be coupled to-:a succeeding stage in a Well-understood mannerto provide another stage of amplification. This is indicated by the placing of a tunable circuit ininductive coupled, relation with coil23;

. this circuit can affect a succeeding tube, such as 17 already described, in a manner similar to that disclosed.

As thus far described, the system does'not made such that the capacitive coupling between grid 18 and anode'22, tends to stabilize the system by causing negative rather than positive feed-back. In order that the resultant negative feed-back may not result in a loss of amplification, and also in. order that reactive coupling between circuit 14 and circuit 27 may be; reduced substantially to zero, thereby making the tuning of each independent of reactive effects due to tuning of the other, I provide means for balancing the system. i

To secure. this result, the high frequency component of the output current is caused to traverse a netv-zork of inductances and capacitles; for nstance, a C011 28, similar to C01l V 23, is in parallelptherewith as regards inductance 24, 'andis in inductiverelation with coil 23,. although not necessarily closely coupled therewith. Furthermore, equal condensers 29 and 30 are placed in parallel relation with inductance 24, by being connected to that terminal of inductance 24 which is nearest the batteryi25j the other terminals .in circuit 27 via coil 23 due to the capacity effect between grid 18 and plate 22 is neutralized by the substantially equal and opposite electromotive force induced therein by coil 28, which is symmetrically arranged with coil 23 with respect to the coil of circuit 27. Asymmetrical system is thus brought about by the fact that the'condensers 29 and 30 have equal values, coils 23 and 28 have the same self inductances, and the same mutual inductance with the coil of circuit 27, and capacity 31 has the same value as the capacity be tween grid 18 and plate 22. The effects of other parasitic coupling between the input and the output circuits may be reduced substantially to zero by properly arranging the battery wires and by providing suitable shielding between the circuits, indicated diagrammatically by numeral 32, all in the manner well understood by those versed in the art.

Nowconsidering the output circuit for the first-stage, it; is seen that coil 24 is in series therewith; and paralleling this coil are the twobranches 2829 and 2330. By proper choice ofthe constants of coil 24 and the equal condensers 29 and 30, it is easy to ensure that it and-its paralleling branches will have a but due to the range of operation as indicated,

only a portion of the righthand branch is used. This portion indicates a negative reactance. Since theefiect of including such a circuit in the output side of the tube is the same'as introducing a capacitive reactance therein, there is no tendency to produce oscillations, and-the system is stable. Furthermore, circuit 27, having equal effect on coils 23 and 28, which in turn are connected to a system of fully balanced capacities, cannot react on the preceding stage through the capacitycoupling in tube 17 V It is possible with this scheme to obtain some regeneration without danger of losing stability, simply by couplingcoil 24 to coil 15. It is foundthat if that be done, the regeneration increases as the frequency dc creases, since-the coil 24 has its impedance reduced with the frequency. This is desirfrom each other so far able in ensuring a substantially uniformde. gree'ofamplification for the Whole range of frequencies. i

. Another form of my'inventionis shown in Fig. 2. This form operates substantially like that of Fig. 1, and difiers therefrom only; in'a few details. For example," coil 231is closely coupled to acoil 33 in. a tunable circuit 34, which coil 33 is in series with the condenser branch of the tuned circuitj Furthermore, the common terminal of condensers 29and 30 is directly connected to ground, and is not directlyconnected to one terminal of coil '24. In both forms of Figs.,1ra:'1d 2,

the series circuit consistin ofithei two b branches 2328"and1293O is also designed tobe resonant toa'frequency below the range of operation of the system, wherety; the reaction on the succeeding stage is also capacitive. Thus'the coupling of this circuit to the capacity branch of circuit 34 in Fig. 2 has the effect of adding a capacity in series to the variable condenser-35 already present in thebranch. Substantially the same eflects as in the'two forms discussed canbe obtained-in the form shown in Fig. 3. In this figure, the antenna circuit 11'12.13" is arranged to afi'ect 'a tunable circuit consisting of coils 36 and 37, both coupled tocoil l2, fixedcondensers 43 and 44, and variable condenser 88. Thetherinionic amplifier 39 has the three usual ele ments 40, 41 and Y42. Its control electrode 41 connectsdirectly to one terminal of con denser 38, while filament connects to. the common terminal of-the pair of equal. condensers 48 and 44that arearranged in shunt to condenser 38. 1 The-filament also connects, by way of grounds and 51,.tvith the common terminal of coils '36 andf37,=which-are wound in the same direction. The output circuit is conventional, andincludes primary 45 of a radio frequency transformer, the secondary .46 of which forms one element of a tunable circuit 47 for affecting the succeeding stage. A neutralizing"circuit. extends from the plate to the lower terminal of coil 37, and includes a capacity 48 whichis'equal to the capacity between-grid 41 and plate 42. A shield 49 se yes to isolate the two stages as undesiredcouplings are concerned.

. it is well understood that whatever efiefct the inter-electrode capacity has'toiiriduce an ,electroinotivc. force across coil 36 is counterbalancedby the electromotive force-induced .in COll '3! due to the neutralizing circuit from plate 42 to 0011 37.. I lnaccordance with I "in invention l'stabilizethis arran ement for the range of operating frequencies by'ineluding an inductance coil '52 in the connec' tion from filament 4O to'coils 36 and 37.} C battery 53 can also be provided .in this connection if desired, There is-thus'aalpap allel circuit joined by this coil,which;:in= eludes in one branch, condenser 43 andflcoil eaees-es so opposite that there isnoreactivecoupling bet'weencircult 47 and the input circuit wh ch includes coils 36 and 37." Furthermore, coil 52 is made of suchivaluethat the parallel circuit comprising coil 52 and branches36, 43 and I 775 belowtherange ofloperationfoii the system.

37, 44 which parallelit, has a' natural. period As in the other forms,,this has the eflectlof stabilizing. the operation of the system with in thatrange. I

signed however, primarily toensure a sub- Fig..-4 I show a circuit thatissimilar inmost-respects to Figs. 1 and 2;.,it,.is de so I stantially equal amplificationfor an signals within the tuning range of circuits l4'and t.

v [The manner in which this is: accom.- pushed will, now .be descrlbed. The input I circuit of tube l7 1s the same as nrFigs- 1 and 2. The outputcircuit includes a coil 54 (that 1' is closelycoupled to another, equivalent coil 55 in the neutralizing circuit) coils 23fand a4s1ni1lar in action to the same numbered coils in Fig.2, and battery 25. -Goi1s28 and} 23neednct-be very closelycoupled togetherlf The succeeding stage 2'Zjshould be symmetrically coupled to 23'and 28 as in=Figure7 and also symmetrically coupled to coils 54 and 55'.

This is'ne'cessai'y in order that the potentials induced in these coils by currents in the coil of'circuit 27v maybe symmetrically distrib ,g ice uted in the balance of thejsystem.

28 30 29 31 and capacity 18 22 is sym -I metrical; there is no'reactiye coupling be-g tween circuit :14 and circuit 27. Further; 195

more, byproper choice ofconstants, the output circuit canbecaused to have a substantially constant efiect on the nput?c1rcu1t,j, 1

whereby uniform amplificationv isjobtainedp and without instability, TlllSlS rendered posslbleby :the co1ls54and 55, which being 1;

in series with the rest ofthe system, have a :risingpositi e impedance as the frequency in'creasesgyand to thfsls added the falling ne'gatiye impedance, of the-parallel system uni;

pling between the input and the output side, andbetween the stages. In'order to effect thisresult, thecoupling-bfcoils 54 and-55 v must hesuch as to'assist the'eitectfof thecouf ce i1 5. 23' and, 28; and their natural' period inust ystem;

nected'.

Thus analyzing-Fig, in detail, the four arms forming a closed ;c1rcu1t are formedthenetresult-i's asubstan- -.'constant impedance ascwell as,cou-;

also; be. outside the operating .;1-

parity and the. grid-plate capacity. The

- coils 28, are connected across the diagonal it between theentremities of capacities 29 and n OJ.

is connected across the other diagonal, and

that'the various capacities forming the bridge circuit is the same as of Fig. 1.

Due to the fact that the input circuit are properly propor ioned, the input circuit cannot be affected by any potential difference that may occur across coils'23 and 28; and conversely, the input circuit cannot aifect these coils throughthe parasitic grid-plate capacity. Thus the stages of amplification are isolated one from another, and principally by the aid of a capacity'bridge.

Theanalysis of Fig. 2' as regards the bridge The main difference is in the mode offconnection of i coil 24, but this does not alter the bridge the second and-t structure detailed in connection with Fig.1.

In Fig. 3, a similar bridge is formed, but slightly difierently arranged. The four arms forming a closed circuit are formed respectively by the grid-plate capacity; the second, by capacityrlS; thethird, bycapacity 44; and the f rth, by capacity d3. The grid 41 connects between the first and fourth arms; thatis,between the grid-plate capacity and capacity The filament connects between capacities i l and 43. Plate 42 con nects between the first and second arms; that LALLJU is between the grid-plate capacity and capacity-e8. 7 7 V The input circuit. 86-3'Z88 connects across one diagonal of the bridge; that is, one terminal connects between the first and fourth arms; andthe other terminal between bird. The output coil l5 connects across; the other diagonal of the bridge; that is, one terminal connects between seccndarm 48 and the first arm formed by the grid-plate capacity; and. theother terminal connects between the third and fourth arms 44 and 43'. As before, due to the proportioning of the capacities in the bridge, the potential differences across the output coil 45 cannot affect the input side; 7 and conversely, the input side cannot afiect the output side through the grid-plate capacity.

In l i l the brid e arms are the. same as v. l D- l 1n Flg. 1, except that in the second and third plate 22 is connected between the thirdand fourth arm; that re, between caarms, formed respectively by the capacities 29, 30, there are respectively inclu ed the coupledcoils and 54;. However, these arms are substantially entirely capacitive, the effect of the impedances of the coils 55, 54,

.being small. The output circuit including coils 23, 28 are substantially across a diagonal of the bridge as before, by connecting across condensers 29, 30.

I claim: 1. In an amplifying system, an electronic emission device, having a plurality of electrodes, an input circuit for said device, an output circuit for sand devlce, means associated with at least one of said. two circuits to oppose the eifectof capacitive couplmg between the electrodes, and means forming with sald associated means, a parallel resonant circuit the resonance period of which is below the range of operation of the system.

2. In an amplifying system, an electronic emission device having a plurality of electrodes, an input circuit connected to the input electrodes, an output circuit connected to the output electrodes, said output circuit including a series inductance, aparallel circuit connected to the inductance and forming therewith a circuit that is resonant at a frequency below the range of operation of the system, and another circuit connecting one of the input electrodes and said parallel resonant circuit and arranged to neutralize the capacity effect between two of the electrodes.

3. In an amplifying system, an electronic emission device, an input circuit for said device including a coil, an output circuit for said device including a coil inductively coupled to the coil in the input circuit, and means whereby the efiect due to this coupling, upon the input circuit is that of a capacity reactance within the range of operation of the system. I

2. in an amplifying system, an electronic emission device having a plurality of electrodes, an input circuit connected between the input electrodes, a parallel circuit having a capacitive and an inductive section, and resonant at a frequency below the range of operation of the system, an output circuit connected between the output electrodes and including the inductive section, the capacit1ve branch including a palr of coupled coils inc one of which is also included inv the output;

circuit, and a circuit extending. from the other'of said coupled coils to one of the electrodes of the input circuit and including a "capacity in series that is equivalent to the capacity between said one ofthe electrodes and an output electrode.

5. In an amplifying system, an electronic emission device, having an electron emitting electrode, a control electrode and an anode,

an input circuit'connected between the electron emitting electrode and the control electrode,*apa1r of equal inductance coils coupled'together, a pairof equal capacities conne'cted in tandem acrossboth coils in series, a connectionbetween the anode and that terminal of one of the capacities which is di-.

rectlyiconnected to one of .said inductance coils, a capacity between that terminal of the other capacity which is directly connected to the other coil and the control elec-.

trode, said capacity being equal to the capac pair of coupled coils, the pair of equal capacthe input circuit.

of the input electrodes withthe ities, and'the last mentioned inductance coil has a parallelresonance ata frequency below the range of operation of the system,

7. The combination as set forth in claim 2, in which the series inductance is-coupled to 8. The combinationas set forth in claim 2,

in which a close inductive coupling is pro-- vided betweenthe. circuit that connects one 7 parallel circuit, and the output circuit. 7 V r 9. The combination as set forth in claim 4, in which ap'air of equal closely coupled inductance coils are provided, one being in se-' ries in the circuit that includes the capacity equivalent to the inter-electrode capacity, g

emisslon'device having an electron emitting 10. The combination as set forth in claim' and the other in series in the output circuit.

' 5, in which a'pair of equal closely coupled inductance coils are provided, one being in series 1n the connection between the anode and one of the capacities, and the other in series with the capacity that is equal 'to the capacity between the control electrode and the anode. r

11. An electrical amplifying system having in combination a plurality of electronic amplifiers arranged in cascade, circuits adjustable for resonance over a range of frequencies interconnecting said amplifiers, means for reducing reactive couplings between said resonant circuits to negligible values including a parallel resonant circuit having a frequency below the range of operation of the system, and means whereby the amplification of each of the amplifiers in the system is maintained substantially constant over the range of frequencies covered by the ad justableresonant circuits.

12. In an amplifying system, an electronic emission device having input and output electrodes; means forming with said device, a four arm capacity brldge, sald electrodes being each 001111601366]. I'QSPGCtlYGbZtQ a corner of the bridge; an input circuit connecting across a diagonal of the bridge; a circuit connecting across the other diagonal of the:

bridge; and means whereby a capacitive re-3 reactance being effective between the input and output electrodes 13. In an amplifying system, an electronic ,1 emlsslon device having input and output ele trodes, means forming with the capacity be-i tween the electrodes a four armed capacity bridge, an input circuit-connectedacross one diagonal of said bridge, and acircuit connected substantially across the other diagonal Q I of saidbridge, the said-latter circuit including a pair of coupled'coils, and a coil con-i necting-between said .pair of coils and an input electrode 14, In an amplifying system, an electronic em ssion device having an electron emitting electrode, an anode, and a control electrode; means forming with the interele'ctrode capacities of said device, a four armed capacitive bridge, the electron emitting, electrode and the control electrode being connected to diagonallyopposite-points, and the anode to one'oftheotherpoints of the bridge; and a other dia'gonal, said circuit including acoil that carriestheoutput current and SZlld coil of the system.

circuit connected substantially across the V 15. In an amplifyingsystem an electronic electrode, an anode, and a control electrode;

means formingwith the interelectrode ca-t pacities of said device, a four armed capaci-z tive bridge, the electron emitting electrode and the control electrode being connected to diagonallyvopposite points,and the anode to n one of theother pointsof the bridge; a 'circuit including a pai'r of coupled coils con nected substantially across the other diago-- nal; and a coil connecting between the said coils and to theelectron emitting electrode;

16. The combination as set forth in claim 1 5,'in which there is includedlanother pair of coupled coils, one in the arm of the bridge that extends between the anode and the electron emitting electrode',an'd the other in that arm whichextends betweenthe electron emitting electrode and that point on the bridge to which none of the three electrodes connect.

17. The combination as set forth in claim 15, in which thereis included another'pair of coupled coils, one in the-armof the bridge that extends between the anode and the 'electhe capacities and coils beingso proportioned that a substantially constant reactive efi'cct is produced thereby between .the inputand the emission device, an input circuit for said de-' vice, an output circuit for saiddevice, said output circuit including a series inductance, andv a parallel circuit connected to said 1nductance and forming therewith a circuit that is resonant at a frequency below the range of operation of the system,/sa1d lnductance being coupled to said input circuit.

' 19. In an amplifying system,;an electronic 7 emission device, an input circuit for said device, an output circuit for said device, said output circuit including an output impedance and a series inductance, and a circuit including capacity connected in parallel with said ii pedancc inductance and forming therewith a circuit that is resonant at a frequency below the range ofoperation of the system,

said inductance being coupled to said input circuit.

20. In an amplifying system, an electronic emission device having an input circuit and an output circuit including an inductance, means for neutralizing capacitive coupling between the electrodes of said device comprising a coil coupled to said output induc-' tance and a capacity connected between said. coil and saidinput circuit, and a circuit including capacity connected in parallel with said inductanceand coil and forming therewith a parallel circuit which is resonant at a frequency below the range of operation f the system.

21. In an amplifying system, an electronic emission device having an input circuit and an output circuit including an inductance,

means for neutralizing capacitive coupling between the electrodes of said device com prising a coil coupled to said output induc tance and a capacity connected between said coil and said input circuit, a pair of capacities in series connected in parallelwith said inductance and coil, and a connection between the common terminal of said capacities and the common terminal of said inductance and coil whereby two parallel resonant circuits are formed, each of said parallel circuits being resonant at a frequency below the range of operation of the system.

22. In an amplifying system, an electronic emission device, an input circuit for said deviceincluding a coil, and an output circuit for said device including-a coil inductively coupled to the coil in the input circuit, means whereby the effect due to this coupling upon the input circuit is that of a capacitive reactance within the range of operation of the system, and inductively reacting means in said output circuit whereby uniform amplification over the operating range is obtained.

, 23. In an amplifying system, an electronic emission device having a pluralityof electrodes,.'an input circuit for said device, an output. circuit for said device, means associated with at least one of said circuitsto oppose the effect of capacitive coupling between the electrodes, means forming with said associated means a parallel resonant circuit the resonant period of which is below the range of operation of'the system, and an inductive reactance in circuit with said parallel circuit, the combined impedance of'said parallel circuit and inductive reactance providing substantially uniform amplification over the operating range.

24. In an amplifying system, an electronic emission device having an input circuit and an output circuit including an inductance, means for neutralizing capacitive coupling between the electrodes'of said device comprising a coil coupled to said output inductance and a capacity connected between said coil and said input circuit, a circuit including capacity connected in parallel with said in ductance and coil and forming therewith a parallel circuit which is resonant at a frequency below the range of operation of the system, and an additional series inductance in said output circuit. r

25. In an: amplifying system, anelectronic emission device having an input circuit and anoutput circuit including an'inductance, a circuit for neutralizing capacitive coupling between the electrodes of said device comprising a coil coupled to said output inductance a capacity connected between said coil and said input circuit, a pair of capacities in series connected in parallelwith said inductance and coil, a connection between the common terminal of said capacities and the common terminal of said inductance and coil whereby two parallel resonant circuits are formed, each of said parallel circuits being resonant at a frequency below the range of operation of the system, and a pair of coupled inductances one in said output'circuit and one in said neutralizing circuit. In testimony whereof I have hereunto set my hand. v

" .HAR-OLD F. ELLIOTT.

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