NGVD Egg ÉÍQÁ’@ \ I H, R @UFTI-ging, I ÈÁÍÍÍÍÁÈS PHASE SHIFTING CIRCUIT Filed may 9, 1944 ‘ F52. ß. v ,4 @#2 [/7 ,20 l â Wig; // ig; lâ „EN/5 @E img?, 5MM ‘ :Patented ‘Novi’ r1946 2,411,423 ' UNi'reo s’rArEs . PATENT ~ ori-*lcs 2,411,423 rmsnsmr'rmo cmcnrr Heath It. Guptill, Washington, D. C., assignor to , General Electric Company, a corporation of__ New York _ Application May 9, 1944, Serial No. 534,769 3 (01.'172-238) connected directly to ground so that it is main that source. tained at the potential of the electrically inter Vmediate connection 6 of winding I. The vari u My invention is oi' genera-l application in electron control and regulating systems, although it is particularly adapted for use in connection with the sweep circuit of the cathode ray tube. In such applications, itis desirable. to control the phase of the potential supplied to the sweep cir cuit through` a' variation of substantially 360 elec «Ítrical degrees in order to obtain optimum oper ationoij such an apparatus. It is an'obie’ct of my invention to provide a new and improved electric phase shifting circuit. It is a further` object off-my invention to pro vide a new and improved electric kphase shifting circuit of the static impedance type in which the able contact II on resistor> I0 is likewise con nected to the opposite terminal Ii‘of winding I. through a variable resistance I4. The resistance I 4 is shown as having‘a contact I5 adjustable in position along the length ci the resistance to vary ’ the resistance between contact II and 10 terminal ä. ‘ connected . ` In the operation of the phase shifting circuit, the two variable contacts I5 and," are moved in a _certain sequence in order to obtain a phase shift which progresses continuously in one direction -15 without discontinuitiesv or reversals. This se quence consists in starting the contact II at the upper terminal of resistor I0 and contact I 5 at output voltage may be varied through 360 elec- ' the lower 'terminal of resistance I4 so that the resistance between output terminal I2 and ter trical degrees relative to the input voltage. minal 5 has a value of zero. The contact I5 is ì moved along resistance I4, changing this re It is another object of~my invention to provide an improved electric phase shifting circuit which is simple in assembly and operation and which sistance to a maximum value. This movement ~ oi' contact I5 produces o, shift in phase in the requires only variable v resistances to obtain a - voltage of output terminals I2, I3 with respect to the voltage across input terminals 4, 5 of phase variation of 360 electrical degrees. slightly less than 180 degrees. Thereafter, con For a better understanding of my invention, tact II is moved along resistor from its upper . reference may be had to the following descrip. terminal to its lower terminal toI 0produce an ad-Á tion taken in connection with the accompanying ditional-` phase shift of between ten and twenty drawing and its scope will be pointed out in the 30 degrees. appended claims. Flg.x1 diagrammatically illus strates an embodiment of my invention and Fig. 2 , illustrates a variable f resistance arrangement which may be employed in the circuit of Fig. l, Referring to Fig. 1, there is shown a phase shift 35 circuit `of the static impedance type which in cludes a winding I across which is impressed an alternating voltage. 'I'he winding I may be the a transformer having a pri . mary winding 2 connected to a source of alter ~ . The winding I is provided with a pair of output terminals 4 and 5 and an elec trically intermediate terminal 6 which is con nected to ground so that the alternating poten 40 so the sequence may be repeated. This particular order of adjusting the variable elements in the phase-shifting circuit produces a phase shift which progresses always in the same direction. If the sequence is reversed, tials appearing across the terminals 4 and 5 are 45. the phase shift is continuous in the opposite di , rection. Any other desired sequence of opera balanced with respect to ground. ' Output terminal 4 of winding I is connected to the common point 1 of a pair of reactance ele ments comprising a iixed capacitance 8 and a employed but the advan tage of essentially constant-amplitude and es sentially uniform phase shift is sacrificed. fixed inductance 9 connected- in'series at their 50 In Fig. 2 there is shown a potentiometer ar rangement which is particularly adapted for use in the phase shifting circuit of Fig. -l. 'In I0 is provided with a variable point or contact II this ligure, elements corresponding to those in which Is directly connected to an output terminal the circuit of Fig. l are designated by corre I2 of the phase shifting circuit. The other out put terminal I3 of the phase shifting circuit is 55 spending reference numerals. The two resist ance units I8. Il each have a value which is opposite ends through a resistor I0. -The resistor , a,41_1,4as at an angle of 180°, or '1r radians, for X.> A poten twice the value of the corresponding ~resistor I4 shown in the circuit of'Fig. l. tiometer having an approximately logarithmic The points Y taper approaches this function. I8-’--2I correspond to the points indicated by like reference numerals 'in Fig. 1. The resist ’ A of either of the contacts I I, I5 depends, of course, ance units I 8, I1 are connected in parallel be upon the particular values of resistances used tween the equipotential points I8, I9 by means for elements I0, I6, I‘I and the reactances of ele ments 8; 8. Likewise, the change in amplitude of conductor 22 of low resistance value to form the inner resistance element of a potentiometer. 'I‘he two ends 20, 2I of resistance unit l I0 have" connected thereto similar conductors 23, -2I to l »The exact phase shift obtained by variation of the output voltage depends upon the relative ' 10 values of these _resistances and their magnitudes, form the outer resistance element of a double potentiometer arrangement. vAt a point oppo site the point I8 on the inner potentiometer` element, the conductors 23, 24 are terminated in' 15’ overlapping contact strips 25. 28, which form a cross-over element in the outer potentiometer. The variable contact points II, I5 are mechani cally linked for uni-control operation. The re sistances I8, I1 and III are so arranged in the potentiometer that, as the contacts II, IB are 20 moved clockwise from the terminals I8, 25, first, the eñective resistance value of resistors I6, Il as >compared with the impedances of the react ance elements of the circuit. In general, a sub stantially uniform shift in phase may be obtained with a variation in amplitude of less than-50 per cent. While I have shown a particular embodiment of my invention, it will, of course, be under stood that I do not wish to be hunted thereto since various modiñcations may be made, and I‘ contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention. What I claim as new and desire to secure by is varied-from a value of zero with respect to Letters Patent of the United States is: ' point I8 to a maximum value at point I8. ~1. In combination, a ' source of alternating 25 Throughout this motion, the value of resistance >voltage having a pair of output terminals bal I0 is unchanged, the contact I5 remaining elec anced with respect to ground, a load connected trically at the potential of point 2t. . Additional between ground and one of said terminals movement varies the- contact point il from the Ácapacitance -end of resistor I@ to the inductance ' end. i. e., from terminal 20 to terminal 2i. .Ad through a variable resistance, a pair of vreac 30 tances connected in seriesf through a resistor, said reactances having a common point connect `ditional clockwise movement of contacts II, I5 reduces the effective resistance value of resistors ed to the other of said terminals, and means connecting said load to a variable point of said I1, It between points i8, I9 from a maximum resistor. value to zero value and completes a phase shift of ' 2. In combination, an alternating current cir 360 electrical degrees. Thereafter, the contact I i 35 cuit, apparatus for producing an alternating moves across the contact strips 25, 2liv changing voltage `variable in phase through 360 degrees the contact Ii from the inductance end of the relative tothe voltage of said circuit comprising resistor It to its capacitance end, and preparing a reactance element in said circuit having a pair of terminals and an electrically intermediate 40 trical degrees. ' , connection, a- capacitance and an inductance In the phase shift circuit described, in order each having one terminal connected to one of to obtain a shift in phase which varies substan said terminals, a resistance connected between tially uniformly with angular movement of the the lopposite terminals of said capacitance and the circuit for another phase shift of 360 elec contacts Il, I5, resistors I6, I'I preferably may be logarithmic in character, while resistor I0 preferably has a linear resistance characteristic. The relation of the resistance between point I8 said inductance, an output circuit connected be-` tween a.' variable point on said resistance and said intermediate connection, and a variable re sistance connected between said point and the and the slider l5 to the angle of electrical phase -~ shift is represented by the following equation: ' X tang-gl) where : R=resistance between point I8 and slider I5 Xï--reactance of element 8 or 9 a=phase shift angle other of said pair of terminals. 50 3. Inrcombination, an alternating current cir cuit, apparatus for producing an alternating voltage variable in phase relative to the voltage of said alternating current circuit comprising a winding energized from said circuit and having 55 a pair of terminal connections and an electrically intermediate connection, a variable resistance a connected between one of said terminals and an output circuit, a resistance having a variable point and connected between said variable _re-v If the mechanical rotation of sliders II, I5 is made equal to the electrical phase shift, for uni 60 sistance and said other terminal through a pairA of serially connected reactances, and means con form phase shift action, the resistance taper is necting saidv output circuit to said electrically in seen to be an inverse tangent or cotangent func tion. This function is one which starts at zero _for zero angle a, then increases at a constantly .termediate connection. increasing rate until it reaches an inñnite value 65. . , _ ' HEATH R. GUPTILL.