US1450080A - Method and electric circuit arrangement for neutralizing capacity coupling - Google Patents

Description

Mar. 27, 1923.

L. A. HAZELTINE METHOD AND ELECTRIC lCIRCUIT ARRANGEMENT FOR NEUTRALIZING CAPACITY COUPLING Filed Aug. 7, 1919 3 sheets-.sheet l FIG. c?.

"Mar: 27, 1923. 1,450.08@

A. HAZELTINE METHOD lAND ELECTRIC CIRCUIT ARRANGEMENT FOR NEUTRALIZING CAPACITY COULING- Filed Aug. '7-, 1919 3 sheeVt's- sheet 2 Mar. 27; 19.23." 1,450,08)l

. L.. A. HAZELTINE METHOD AND ELECTRIC CIRCUIT ARRANCEMENT FCR NEUTRALIZING CAPACITY COUPLING Filed Aug. '7, 1919 5 sheets- sheet 3` Poema Mu. 21, i923,

UNITED iSTATES PATENT OFFICE.

LOUIS A. HAZILTINE, 0F HOBOIEN, NEW JERSEY.

muon am) gnnc'rsrc CInCUI'I` ARBAHGHENT IOR NEUTELLIZING COUPLIIG.

CAPACITY Anneau@ ala ang-n 7, ma. semi n. 316,007.

. of capacit Acoupling between two electric circuits, w ich capacity' coupling results in the transmitting `from-one circuit to the other."

15,' ItV has long been known from practical experience that the presence'of capacity,

coupling between the primary and secondary circuitsl of a radio receiver results linthe transmitting of undesired signal oscillations,

l) 4particularly those of short wave length, from the primary to the secondary circuit. This reduces the selectivity of the receiver and frequently prevents the reception of the .desired signal, which is drowned'out by a more la powerful signal of a different wave-length. Twofmethods have Ybeen .used to reducethe capacity coupling; rst, thephysical sc pal ration ofl the two circuits by as great a istance as isfeasible; and second, the partial enclosing of the 'circuits in metal screens.

. Neither method is entirely effective, for thereuire an impracticably wideA f t first would separation-o e circuits; while in the sec-v ond the-metal screens could not completely l'enclose'. the circuits as Athey would then prevent the desired magnetic coupling. s "Again, it is well known that capacity cou-V pling between the grid and plate circuits of au audion nia result in the production of oscillations. uch oscillations are4 Yfrequently very undesirable, particularly in audion am lilers, as they may completely Y the signal which it is desired to .am-

- As a third example of the undesirable effects of capacity vcouplingit has been found difficult to arrange a Wheatstone brid for high-frequency measurements, due to t e capacity coupling between the supply circuit and' the detector circuit, which may result in a false balance and so vitiate the results of the measurements.

cou ling between two circuits such as are deof undesirable disturbances c1rcu1t diagram 'asjused in the moet a vanced type o'f-re"- This invention is directedto the elimina- Vtion of the undesirable effects of capacity scri d 1n the foregoing examples. This is accomplished briefly as follows: An auxiliary circuit is provided which is electromagnetically coupled to one of the two original circuits which we will call the' first circuit, and capacitively coupled to the other, or second circuit. If a disturbing volta then exists in the second Circuit, it will Acause currents'fto flow both inthe rst circuit a nd in theauXIaR circuit, due to the capacity coupllngs. e electro-magnetic couphng between the auxiliary circuit and the first circuit is then arranged so that the magnetic effects of these two currents will.

neutralize one another and so will result in 'Il no volta e across" the first circuit. Conversely, if a disturbing voltage exists in the first circuit, it will` result in no voltage across the second circuit, by the Well known reciprocal properties of electric circuits.

,The arrangement of the auxiliary circuit will depend on the forms of the original circuits. In some cases it is necessary to add coils or capacities fo the original circuits to provide the required couplin while in other cases the couplings may obtained Vfrom coils present for other purposes or from inherent capacities. ,ff

The' principle and certain applications of this invention are illustrated 1n the accompanying drawings in which Figure 1 is a showing two capacitively coupled circuit elements which are not d1-v rectly connected, andthe arrangement fcr neutralizing this capacity coupling; Figure 2 -is a corresponding *diagramv or t e case of two circuit'e ements directly connected; Figure 3 is a vwiring showing the a'rrangement for neutralizing ca acity couplingbgtween the primary an secondary circuits `of a radio receiver; Fi re 4 is a cross-section of the coupling coils and the auxiliary coil in a radio receiver; Figure 5 shows a preferred arran ment of these coils l ceiver built for the United States Na Figure 6l is a circuit diagram showing t arrangement for neutralizing capacity coupling between the grid and plate circuits of n? VAand C, remaining the coupling capacities.

an audion; Figure 7 is a circuit diagram, showing the arrangement for neutralizing capacity coupling tied form of secondary winding whichv may be utilized as an alternative to the arrangement shown in Fig. 4. f

Referring to Fi re 1, reference characters A and B indicate the circuit elements having undesired capacity coupling thru the capacities C, and C3 and thru the imedances Z and Z". Reference character 1 indicates a coil which may be part of circuit elenient A or may be additional thereto; L2 represents the auxiliary coil closely coupled electro-magnetically to L1 and thence to circuit element A, and at the same time capac' itively coupled to circuit element B through capacities C2 and C1. The sense of electromagnetic cou lin between L and L2 is such that termina s' o lunlike po arity are connected together. To understand the principles of this arran ement, first suppose that the two coils are a ike and are very closely coupled, that (CF1-TG2) and that (C3:C,). Also suppose, just for the moment, that A is removed; then by symmetry a source of voltage in B will cause equal currents totlow through L1 and L11'Which currents will neutralize one another magnetically; so no voltage will be induced in eitherl coil. Now if A is replaced, it will be connected betweenA two points having no difference in potential and so willnot alter the electrical conditions, assuming the resistances of the coils negligible in comparison with their separate re- ,actances ment B will not result in a voltage across circuit element A so the effects of capacity cou ling will have been neutralized. Y A ore generally in Figure 1, suppose the to be unlike, though still L2 -to L, is N1/N1, then we must have .0, Cs N,

C, Ct N1' in which case' the currents of C1, C1 and L1 will be Nz/N1 times the currents of. 0 CM and L1, respectivel and the magneto-motive force of L2 will still neutralize that of L, giving no induced voltage in either coil.

lt should 'be noted that the above conditions for neutralization impose no limita- '1 tions on the internal conditions in 'circuit elements A and and Z.

If the impedance Z','

B nor on the values l.of Z

of Figui@ 1 is relaced bv a direct connection, the capacities;-

1 and C4 are directly in parallel with vA and L2, respectively, and so no longer act as couplin capacities. This circuit in effect becomes't at ofFigure 2, where the` same reference characters refer to like parts, Cl

i to the detector circuit of a Wheatstone bridge; and Fig. 8 is a modi- Vinsulated therefrom by insulator 1,5.

Thus the voltage in circuit ele-Y 'ducingthe capacities C, and C, by

Thr condition. for neutralization, as before, is simply v 'and 3 by metal partition 4. This metal lining is grounded as at 5. The antenna 6 is connected thru the primary coil -7 of the coupler 8 and variable condenser 9 to the metal'lining connected to' earth 5. The anl tenna lead passes -thru the metal walled cabi.- net but is insulated therefromby insulator l0. The secondarycoil L, of the cou ler having terminals 12 and `13 is connected at one end thru lead 13a with detecting appa- A ratus in compartment 3 and at the other end tothe metal lining 1 by means of lead 12. The lead 13 passes thru partition 4 and is The detecting apparatus in compartment 3 may be composed of a suitable circuit'inducta'nce 16, variable condenser 17 grounded at 18 and `leads 19 taken to the usual detector, preferably an audion. The moving elements of the condensers 9 and 17 are those connected to ground; so that no external capacterminal 12 and free ended at Aterminal 21.

This auxili coil; is Wound over secondary coil L1 but in opposite direction thereto, from terminal 12 as a starting point.

By the arrangementof the apparatus as above described in compartment 2 and 3 it'will be seen that the only possibility of capacity coupling between 'the' primary and secondary circuits lies in the inherent capacities C, and C11, between primary coil 7 and the seconda T coil. L1. This capacity coupling is neutra ized by the auxiliary fcol L2 and the inherent capacities C1, and C4 present by reason of the addition of coil L1. In actual construction the turns of coil L2 are wound over the turns of secondary coil L giving close-magnetic coupling and retheir screening action. The circuit of Figure 3 lis thus a s ecial application of the general tically, the primary coil 7 of Figure 3 correlltl the ratio of turiis"N,/l\'1 of the coils respectively. The secondary coil has -its iary coil L, is closely `coup 1,450,0eo B i sponding to the lcircuit element B of Figure To neutralize'. i apacity coupling. the i 1, the portion of the secondary'circuit in auxiliary coil 12,1 islclosely coupled e compartment 3 .corresponding tothe circuit magneticallytofthej grid coil L1 'and is conelement the antenna-ground circuit 6 to' nected abetween'wthlament and'tlie neuv 5 corresponding to the impedance Z and the tralizing capacity; whose' other. terminal 701 arbitrarily variable condenser 9 correspond` is connected to "t e plate. This circuit is ai ing to the impedance, Z. Neutralization of s iecial application" of thegeneral circuit of the capacity coupling will therefore be' at- Iigure2; and-neutralization of thecapacity tained', as in Figure I1, when the capacity coupling duc to C, will be attained, as in ratios (l1/C2 and C3/C, are madee ual to Figure 2, when the ratiooff'ca 'cities l/C, 75

(la, and. is v made equal to the ratio. opturns N,/N1 L1, respectively. The turns of L, are ad-A ofthe coils L,and L1, respectivel justed by trial and will be less than those Figure 7 illustrates the application of this on Ll as the capacities'C, and C4 exceed invention to the neutralization ofthe ca ac- -C1 and C, respectively. The symmetry of '.-it-ycouplin tothe detector circuit of ahi'gh0 4 the arrangement is relied on to maintain ap frequency heatstone bridge. The detector proxiinate equality between (J1/C2 and is connected across the secondary coil Ll of C,/C even when .the coils L, and L2 are a transformer whose rimary coil L ismoved relativeto coil 7 to secure variations connected between the etector pointsof the in electro-magnetic coupling between the bridge proper. The detectorfcircuitliscapau primaryand secondarycircuits: citively coupled to the bridge proper'through igure 4 is a crosssectional view showing the inherent capacities andil C, and the -arran ment of the. primary, secondary through the .bridge arms and ground; To and auxi iary couplel coils 7, LL and L neutralize 'this capacity coupling theauxil ed e ec'tro-mag- .0 high- potential end 13 connected through the net ically tol L1 and capacitively coupled to secondary inductance 16 to the detecting ap. the bridge proper thru the neutralizing. ca-

' paratus as describedand the auxiliary coil pacit-ies' C, and 0,. -This circuit is a special starts at the terminal 12 of the secondary application of the-general circuit of F ig-4 coil and doubles back over the secondary ure 1 andneutralizationof -the capacity. coil in the opposite directionwith the end couplin will be: attained as in F igul'e 1,

21 left free.' The auxiliary coil is suitablywhen t e capaci supported over secondary coil Lnb insuare made equal 'ratioof'turns vN,/ N1 lating drum 20. In case the lead 1' from ofV the coils El,.vi'epectivelyl It is the upper terminal 13 of L1 has appreciable dcsirableto .pla'c'e'tlicaux'ilia coil L, be- 100 capacity this may be neutralized by means tween" L i of the arrangement shown in Fig. 8 wherein C1 andjf' by l itsefscreing actiong5 in. a dumm lead 21* is shown connected to the YFigure '4; Y' terminalY the lcad 13. The alternative arrangement I claim Aand Vdesire vto secure. by- Letters '105 oil.v Fig.. 7 includes" an 'additional auxiliary Patent of the, United States is:

coil L2 Wound inside"l the SGCOndlllj' "QOH L1 '1. In a system of two electric circuits and capable of bein rotated by means of inversev ratio of the'- capacities with which pling.

' fimpedence Z. Reference c the purpose of which is to proyide more coupled through a junction point and complete screenin Each of the c'oils L1, through a capacity, means forneutralizin L, and L', is pre erably grounded as shown the capacity coupling comprising a coil u at 12. connected between said junction pointv and Figure 5 is a sectional view of the preone terminal of said coupling capacity, and ferred arrifngement of the coupling coils an auxiliary coil and a neutralizingcapacity wherein the primary coil 7 is rigidl mountunequal to'the coupling capacityconnected ed on panel 22 by supports 23 an 24, Secbetween said junction pointl and the other 115 ondary coil L1 and auxiliary coil L, insu-v terminal of the coupling capacity, said coils lated therefrom by- suitable insulation 20 being lclosely coupled elect-romagnetically are .wound on frame 25 mounted on shaft 26 and having av ratio of turns equal to the knob 27 to obtain' di erent degrees of cou-A they are respectively associated.

2. In a system of two electric circuits-in Figure 6 illustrates the application of this which an element of one circuit has one terinvention to the-'neutralization of the capaminal connected to the second circuit cityV coupling between the gridA and plate through coupling Vimpedances and has its 21 of L, and disposed alongside'f 4Having thus described-my invention, whatV circuits of an audion, the grid circuit conother -terminal connected to the'second cirmi taining. a coil L, and the plate circuit an cuit through a group of coupling capacities, 'ancter C, inmeans. for neutralizing sai couplingY c omdicates the inherent coupling capacity, partj prising'a coil connected between said ter- V of which iswithin the audion and part be i minals and anauxiliarv coil closely coupled tween theleadsto the grid and the plate. electromagneticallytothe first coil and conl vnecte'd between the first mentioned terminal and the common terminal of. a group. of neutralizing capacities, each of which extends to said second circuit, is associated with one couplingcapacityfand has a ratio to its associated Vcoupling capacity equal tothe inverse ratio of turns of the 'auxiliary coil to the first coil.

3. In a. system-of two electric circuits in which an element of one circuit has one ter mina] connected to the second circuit through coupling impedances and has. its other terminal connected to the second circuit through a pair ofv coupling ca acities, means for neutralizing said coup ing comprising a coil connected between said terminals and an auxiliary coil closely coupled electromagnetically to the first coil and connected between .the first mentioned. terminal` and the common terminal of a air of neutralizing capacities, each oi w ich extends to said second circuit, isassociated with one v coupling capacity, andv 'hasa ratio to its which an element of one circuit' has one associated coupling ea acityequal to the in verse ratio of turns oi) the auxiliary coil to the first coil.

4. In a system of two electric circuits-in terminal connected-to" the second circuit through arbitrarily variablev coupling impedances and has its'p'other terminal connected to the -second 'circuit throu h- .a group of coupling capacities, means or .neutralizing said'coupling comprising a coil connected between said terminals and `an auxiliary coil closely coupled electromagnetically tothe first coil and connected' between the f first mentioned terminal' and the 'common ter-- minal of a groupv of neutralizing capacities,

each of which extends to said second circuit, is vassociated with one coupling capacity, and has a ratio to its associate coupling capacity equal ,to the inverse ratio of turns of theY I gether, said auxiliary coil beinginterposed f in the electro-static field created between vsaid coil and said circuit.

6. ,In a Wave signalingresponsive device comprising a primary circuit and a secondary circuitl the combination of a conducting screen electro-statically isolating the secondary from the primary -circuits except-for a pair of coupling coils and an auxiliary coil electro-magnetically coupled and connected to one of said coupling coils with terminals of Aunlike polarity connected together, said auxiliary coil havingfcapacity coupling to the other of said cou ling coils.

7. In a wave sign ingresponsive device comprising a primary circuit and a secondary circuit, the combination of a conducting screen electro-statically isolating the secondary from the primary circuits ex ceptpfor a pair of coupling coils, and an auxiliary 4coil electro-magnetically coupled and connected to one oi said coupling coils with terminals of unlike polarity connected together, said auxiliary coil being interposed in the electro-static field created between said coupling coils.

Louis A. HAZELTINE.

Images