Phase-shift cell and a phase shifter for the application of said cell
United States Patent Encellaz et a]. Apr. 8, 1975 [54] PHASE-SHIFT CELL AND A PHASE 3.502.976 3/1970 Chamberlin 328/155 X SHIFTER FOR THE APPLICATION OF SAID CELL Primary E.\&#39;aminerMichael J. Lynch [75] Inventors: Robert Encellaz, Saint Martin-v A i tant E.\&#39;aminer-B. P. Davis dHere ;Jean-Paul Bonnefoy- AllOl&#39;ll), Agent, or Firm-Flynn &amp; Frishauf Claudet, Montrouge; Hans J edlitschka, Chatillon-sous- Bagneux; Michel Martin, Brie ABSTRACT A ;Ed dT 35323 an :z gi z The phase-shift cell comprises in combination a programmable generator WhlCh produces constant cur- [731 Assignees: C m i -i t AlE i At i rents, a bistable threshold circuit connected through Paris; Tekelec-Airtr i S v an integrator to the output of the generator, and a b th f, France feedback loop connected between the output of the threshold circuit and the input of the generator. Re- [22] Sept 1972 versals of the threshold circuit to a first state are initi- [211 App], No; 292,933 ated by synchronizing signals to be phase-shifted, re-  
  versals to a second state being initiated by the output signal of the integrator when the signal-attains the [30] Forelgn Apphcano Pnomy Data threshold level of the bistable circuit. The phase shift OCL 5. I971 Fl&#39;Zll&#39;lCC of the output signal of bistable circuit respect to the input signal is determined by the instant 328/128 T of reversal to the second :state. An additional cur- [51 1 Clrent generator connected between the aforementioned [58] Field of Search 328/127 155, 28; 307/262; generator and the integrator modifies the output signal 331/452 323/101, 106; 331/45 of this latter in order to vary the instant of reversal of the bistable threshold circuit to the second state. [56] References Cited UNITED STATES PATENTS 2 Claims, 9 Drawing Figures 2.567,4l() 9/1951 Trousdale 331/45 OUTPUT LOGIC CCTS. I  
 L PM PM P BISTABLE CCT.  
 SHEET 1 [1F 3 PATENTED 8 I975 FIG. 1  
 SWITCHABLE aw FIG. 5  
 PATENTEDAPR 81975 DIFFERENTIATOR .0. N B. A U H mm SC B 1 -l 2 m1: 1/ IO 7 IIIAIIII fi Alli! A v x l fl &#39;5 6 7% 5 SHEEI 2 BF 3 1 PHASE-SHIFT CELL AND A PHASE SI-IIFTER FOR THE APPLICATION OF SAID CELL This invention relates to phase shifters.  
  Devices of this type which are already known usually consist of filter networks. In these devices, the phase is dependent on the frequency.  
  Other devices for comparing saw-tooth waveforms with threshold levels can be made aperiodic by means of complicated expedients but cannot operate over a broad dynamic frequency range. These devices are also dependent on accuracy and drift of the thresholds.  
  Still further devices of the digital type can also be aperiodic but cannot operate over a wide frequency range. Moreover, the phase variation can take place only in a discrete manner.  
  The aim of the invention is to overcome the abovementioned disadvantages by producing a phase-shift cell which is of simple construction and exhibits good reliability of operation. The invention is therefore directed to a phase-shift cell of this type which essentially comprises in combination a programmable generator which produces constant currents, a bistable threshold circuit connected through an integrator to the output of said generator, a feedback loop being connected between the output of said threshold circuit and the input of said programmable generator, the reversals of said threshold circuit to a first state being initiated by syn chronizing signals to be phase-shifted whilst the reversals of said threshold circuit to a second state are initiated by the output signal of the integrator when said signal attains the threshold level of said bistable circuit, the phase shift of the output signal of said circuit with respect to the input signal being determined by the instant T, of reversal of said bistable circuit to the second state thereof. In accordance with one particular feature of the invention, an additional current generator connected between said generator and the integrator is intended to modify the output signal of said integrator in order to produce a variation in the instant of reversal of the bistable threshold circuit to said second state.  
  The invention is also directed to a signal phase shifter which essentially comprises four cascade-connected phase-shift cells as hereinabove defined, the first of said cells being provided with an additional current generator in such manner as to deliver a signal which is displaced in phase with respect to the input signal having a period T by a quantity such thatj s 6 s T/2 j and being synchronized by said input signal whilst the three other cells are respectively synchronized in each case by the output signals of the bistable threshold circuit of the preceding cell, said signals being displaced in phase with respect to the input signal respectively by T/4 0, T/2 6 and 3T/2 6, the outputs of the first and the third cell and the outputs of the second and the fourth cell being connected respectively to the inputs of two bistable circuits the ranges of phase displacement at the outputs of said bistable circuits being respectively 90 i 90 (T 4j/T); etc.. 360 90 (T 4j/T).  
  Further characteristic features and advantages of the invention will become apparent from the description which now follows below, reference being made to the accompanying drawings which are given solely by way of example, and in which:  
  FIG. 1 is a schematic diagram of the cell according to the invention for shifting signals in phase;  
  FIG. 2 is a timedependence diagram of the signals collected at different points of the diagram of FIG. 1;  
  FIG. 3 is a schematic diagram of an aperiodic phase shifter, a number of cells such as the cell shown in FIG. 1 being employed in the construction of said phase shifter;  
  FIG. 4 is a time-dependence diagram of signals sampled at different points of the phase shifter of FIG. 3;  
  FIG. 5 is a schematic diagram of a controlled dutycycle signal generator which makes use of circuits such as the circuit shown in FIG. 1;  
  FIG. 6 is a time-dependence diagram showing the signals sampled at different points of the circuit of FIG. 5;  
  FIG. 7 is a schematic diagram showing the application of the circuit of FIG. 1 to an aperiodic polyphase generator;  
  FIG. 8 is a schematic diagram showing the application of the circuit of FIG. 1 to an aperiodic frequency multiplier;  
  FIG. 9 is a time-dependence diagram showing the formation of the output signal of the multiplier of FIG. 8.  
  The phase-shift cell or phase-shifting element which is illustrated in FIG. 1 mainly comprises an integrator 1 formed by an operational amplifier 2, a capacitor 3 being connected between one input and the output of said amplifier.  
  The input of the amplifier .2 is connected to the output of a first programmable current generator 4 which is capable of delivering in alternate sequence two currents I and I having different and constant intensities.  
  The output of thejintegrator l is connected to the input of a bistable threshold circuit 5 having another input 6 to which synchronizing signals are applied The bistable circuit 5 of the type which operates in accordance with the Eccles-Jordan principle, for example, is connected to one control input of the generator 4 through a feedback loop 7 in order to determine the choice of current delivered by this latter.  
  Finally, a second current generator 8 is connected between the first generator 4 and the integrator I.  
  In order to illustrate the operation of the circuitof FIG. 1, reference will be made to the diagram of FIG. 2 in which the curves (a), (by, (c) and (d) represent respectively the synchronizing signals applied to the bistable circuit 5, the threshold level of the bistable circuit, the output signal of the integrator l, and the output signal of the bistable circuit.  
  Referring first to the threshold level which is represented by the straight line (b) of FIG. 2, this straight line defines two zones A and B of the dynamic range of output of the integrator.  
  When the output voltage of the integrator reaches the zone A from the zone B, the bistable circuit assumes a state a which initates operation of the generator 4 so that this latter should deliver at its output the current I the direction of which is such as to return the output of the integrator 1 into the zone B.  
  The bistable circuit 5 remains in state 5&#34; until a synchronizing signal (a) applied to its input 6 causes the bistable circuit to change-over to a state a which initiates the operation of the generator 4 in order that there should thus appear at its output the current I having a sign such as to return the output of the integrator 1 from the zone B to the zone A.  
  When the output voltage of the integrator l attains he threshold (b), the initial conditions are again retored.  
  The arrangement of FIG. 1 therefore behaves as a :ircuit for shaping synchronizing signals if these latter ire periodic.  
  The time intervals T, and T which correspond to the tates and Z of the bistable threshold circuit deend on the currents l, and 1 which are delivered by he generator 4 as shown by the following calculation.  
  The currents I, and being considered as circuit paameters, let  
 I, KI  
 vith K 1.  
  If the current generator 8 applies a continuous curent i to the input of the integrator with l, the ime configuration of the states of the bistable circuit i are linearly dependent on i.  
  When i is close to the value of I, the input of the inte- ;rator l is not driven far into zone B, which means that he approach to the threshold (b) of FIG. 2 following he next switching of the bistable circuit 5 in conseuence of a signal applied to its input 6 starts from a &#39;oltage close to the threshold. This explains why the Witching back of the bistable circuit 5 when the hreshold is reached, the time of which determines the ntervals T, and T depends not only on the current I,, vhich as discussed above is equal to KI i, but also on he current 1 which in the example given is equal to l i.  
  Let T be the period of the output signal of the bistaile circuit 5 as defined by two successive synchronizing ignals applied to the input 6 of said circuit and let T, ind T be the time intervals of the states a and (T asumed by the bistable circuit during the period T.  
 We then have T= T, T  
  Let AV be the variation in output voltage of the intezrator l as shown at (c) in FIG. 2, neglecting i for the noment.  
  AV can be expressed as a function of I,,T, or 1 T, by he relation:  
 0 we get At the input of the integrator, there takes place an vlgebraic addition of the currents I, or 1 of the generaor 4 to the current i of the generator 8, whith the result hat the currents applied to the amplifier 2 are given by he relations:  
 I KI i vhich gives the relation:  
  Postulating that the current i delivered by the generator 8 is zero, i 0, the time interval and by setting AT= T, T we obtain i l I l+K and limits the value of the current i to |i| I.  
  It is found that the value and the stability of the threshold do not have any effect on the operation of the circuit, with the result that this operation is not influenced by any possible drift of said threshold.  
 If we now employ expression (1) once again i T T W it is deduced therefrom that:  
 T I l +K In accordance with the previous relation, the quantity AT/T is a number which is independent of the period and can be considered as a phase angle.  
 in which the angle a can be governed by the intensity of the current i delivered by the generator 8.  
  Taking as an example the conditions in which K,, 3, we obtain:  
 with  
 lil 1.  
  In accordance with equation 1 if the current delivered by the generator 8 is zero (1&#39; o), AT= 0, consequently T T and as in the case of K 3,  
  In consequence, when the current i O, the circuit arrangement constitutes an elemental 90 phase shifter;  
  When i =l= but i I. the circuit constitutes an elemental phase shifter which produces a displacement in phase of 90 Aa with |Aa| 90.  
  These possibilities of the circuit arrangement illustrated in FIG. 1 are turned to useful account in the design of the aperiodic phase shifter which is illustrated in FIG. 3. This phase shifter is made up of four phaseshifting elements Du to Dd such as the element shown in FIG. 1.  
  A current generator 8a formed by a voltage divider 9 is connected between the integrator 1a and the current generator 4a of the phase-shifting element Da. Said voltage divider is so arranged that the opposite terminals are connected to voltage sources +V and V and the slider is connected to the conductor which connects the generator 4:! to the integrator 1a through a resistor 10.  
  A differentiator connected to the input 6a of the bistable threshold circuit a and having an input 12 to which the signal to be phase-shifted is applied has the design function of differentiating the positive fronts of said signal in order to ensure synchronization of the circuit. The phase-shifting element Da is therefore of the type which produces a phase shift of 90 Aa.  
  The phase-shifting elements Db, Dc and Dd are of the type which produce a 90 phase shift and therefore do not comprise a current generator 1&#39;.  
  The bistable circuit 5a is connected to the synchronization input 6b of the bistable circuit 5b of the phaseshifting element Db by means of a differentiator (not illustrated). Similarly, the bistable circuits 5b and 5c are connected respectively at their corresponding outputs to the synchronization inputs 6c and 6d through differentiators (not shown).  
  The phase shifter further comprises two bistable circuits l3 and 14, the inputs of the bistable circuit 14 being connected respectively to the outputs of the differentiators (not shown) whilst the inputs of the bistable circuit 14 are connected respectively to the outputs of the differentiating circuits (not shown).  
  The operation of the phase shifter is illustrated by means of the diagram of FIG. 4, in which the curves (a) to (0) represent the signals at different points of interest of the circuit.  
  The phase-shifting element Da is synchronized by the positive fronts (curve (b)) of the signal to be phaseshifted (curve (a) of FIG. 4).  
  Said element delivers a positive pulse which is delayed with respect to the input signal by a quantity 0 which is theoretically comprised between 0 and T/2.  
  However, for reasons of stability, a limited operating range is employed, in which case the value 6 is such that The output signal of the bistable threshold circuit 5a of the phase-shifting element Da is represented by the curve (d) of FIG. 4.  
  Said signal is differentiated in a differentiating circuit which has not been illustrated (curve (e)) and applied to the synchronization input of the bistable threshold circuit 5b of the phase-shifting element Db which delays said signal by T/4 with respect to the synchronizing signal (curve (g)), that is to say by T/4 6 with respect to the input signal.  
  Said signal is then shifted in phase by T/4 with respect to the synchronizing signal by means of the phaseshifting element Dc (curve (i)), that is to say by T/2 0 with respect to the input signal.  
  The phase-shifting element Dd which is controlled by the signal delivered by the phase-shifting element Dc produces a signal which is delayed by T/4 with respect to its synchronizing signal, namely 3T/2 0 with respect to the input signal.  
  After each phase shift, the signal is collected at the output of differentiators (not. shown) and applied to a corresponding input of the two bistable circuits l3 and 14 which deliver at their outputs the signals shown at (I) to (0) in FIG. 4.  
  The output Q of the bistable circuit 13 delivers a square-wave signal (shown at (I) in FIG. 4), the phase shift d) of which with respect to the input signal varies with the current i delivered by the generator 9, 10 within limits such that:  
  The output 6 of the bistable circuit 13, as shown at (m) in FIG. 4, is in opposite phase with respect to the output 0,. Said output is therefore phase-shifted with respect to the input signal by an angle such that 60 j 360 j T s 4, s 270 T whilst the output 6 as shown at (0) in FIG. 4 is phaseshifted with respect to the input signal by an angle (1&#39;: such that:  
  90 50 that is to say 36(lj O 40 There 2 re then obtained in the case of the outputs Q,,  
 Q 6,, Q of the bistable circuits l3 and 14 ranges of variation in phase of: 50 which are centered on 90, 180, 270 and 360. A suitable choice of any one of the outputs Q,, Q Q, and Q and of the current itherefore makes it possible to obtain at one of the outputs of the phase shifter a square&#39;wave signal which is displaced in phase with respect to the input signal by any quantity between and 360.  
  The circuit which is illustrated in FIG. 1 is also employed in the construction of the controlled duty-cycle signal generator which is shown in FIG. 5.  
  Said generator comprises two cascaded elemental phase-shifter circuits l5, 16 providing fixed phase displacement and a bistable circuit 17, the two inputs of which are connected respectively to the synchronization input 18 of the circuit 15 and to the output of the bistable threshold circuit (not shown) of the circuit 16.  
  A generator of this type makes it possible to. obtain from pulsed signals a square-wave signal having a duty cycle of one-half.  
  A pulsed signal applied to the input 18 of the circuit 15 synchronizes said circuit and initiates the reversal of the bistable circuit 17 to a first state Aas shown at (a) and (f) in FIG. 6.  
  The output signal (0) of the circuit 15, as delayed by T/4 with respect to the input signal, is suitably differentiated and the resultant pulses corresponding to the positive fronts of said output signal are applied to the synchronization input of the circuit 16 and this latter then delivers at its output a signal (e) which is delayed by T/2 with respect to the input signal of the circuit 15.  
  The output signals of the circuit 16 ini tiate the reversal of the bistable circuit 17 to a state A.  
  As a result, the transition of the bistable circuit 17 from state A to state A takes place only at the end of a time interval T/2 after application of the input signal.  
  There therefore appears at the output of the bistable circuit a signal (f) having the same period as the input signal and a duty cycle of one-half.  
  If so desired, it is of course possible to obtain at the output of the bistable circuit 17 a signal having any duty cycle between 0 and 1.  
  To this end, the elemental phase-shifters 15 and 16 in the circuit of FIG. need only be replaced by the phase shifter of FIG. 3, in which case the reversal of state of the bistable circuit 17 is initiated on the one hand by the input signal of the phase shi fter and on the other hand by one of the outputs Q, to Q of this latter.  
 The aperiodic polyphase generator which is shown in FIG. 7 makes it possible to divide a period T into two parts, namely T/K in one case and T (K UK) in the other case.  
  A generator having n phases makes it possible to split up a complete period into n different states.  
  The generator must therefore be so designed as to split up the period Tinto n portions each having a value of T/n.  
  With this objective, there are employed (:1 l) circuit elements D, to Dn l which are of the type shown in FIG. 1 and connected in a chain.  
  Each phase-shifting element is also connected to a phase-synthesizing logic circuit L.  
  Each phase-shifting element D, to Dn l delivers a signal corresponding to the beginning of the following phase.  
  The logic circuit L which is synchronized, if desired for reliability, by the input signal then reconstitutes each of the n signals thus obtained as was done, for example, for the four outputs of the respective cells of the circuit of FIG. 3 by the bistable flipflop circuits l3 and 14, and delivers at its n outputs signals having a period T but relatively displaced by T/n. Since the nth input is simply the input signal delayed for the complete period T, an nth phase shifting circuit is not necessary and if a separate nth input is necessary, a known circuit for delivering the input signal following the input signal which is delivered at the first of the n outputs can be used.  
  The aperiodic frequency multiplier which is shown by way of example in FIG. 8 performs multiplication by 4.  
  Said multiplier comprises three chain-connected phase-shifting elements D, to D, having fixed phase displacement and of the same type as the element shown in FIG. 1.  
  The phase-shifting element D, is synchronized by the input signal having a period T, the frequency of which is to be multiplied. The multiplier further comprises an OR-circuit 18, the inputs of which are connected to the inputs and to the outputs of the three phase-shifters D, to D The output of the OR-gate is connected to a generator 19 having a duty cycle of one-half such as, for example, the generator which is shown in FIG. 5.  
  Each phase-shifting element D, to D delivers a synchronizing pulse (c), (e), (g), (shown in FIG. 9) which is delayed with respect to the input signal (a) by T/4, T/2 and 3T/4.  
  The OR-circuit l8 re-groups these pulses and the input pulse and delivers four uniformly spaced pulses (h) during one period T. These pulses are applied to the /2 duty cycle generator 19 which delivers at its output a square-wave signal (1&#39;) having a period T/4.  
  The devices shown in FIGS. 3, 5, 7 and 8 can operate over a very wide frequency band of the order of l cps to 10 cps by mounting a network of self-switching capacitors across the terminals of the integrators which are employed in the construction of the phase-shifting elements.  
 What is claimed is:  
  1. An aperiodic generator of polyphase pulse signals having nl phases comprising:  
 nl chain-connected phase-shift cells of which the first cell is synchronized by a single phase input pulse signal of minimum repetition period T to be converted to a polyphase pulse signal and the following cells are each synchronized by the output signal of the preceding cells;  
 a phase-synthesizing logic circuit having n outputs and having connections to the outputs of each of said phase shift cells and arranged to produce nl outputs having the same repetition period as the input signal; each of said phase shift cells comprising:  
 a constant current generator having two constant current output states, the direction of output current in one of said states being opposite to that in the other of said states;  
 an integrator having as its input the output of said constant current generator;  
 a bistable threshold circuit arranged to go from a first state to a second state when the output of said integrator attains a predetermined threshold level of said bistable threshold circuit and to go from its second state to its first state in response to input impulses, said bistable circuit being connected to switch said generator correspondingly between its output states; and  
 means for deriving phase shifted output synchronizing signals from the transitions of said bistable threshold circuit from said first state to said second state; and  
 means for supplying to at least one of said cells a current additional to the output of the constant current generator thereof for controlling the amount of phase shift produced thereby;  
 said phase shift cells being arranged so that the aggregate phase shift produced by the last of said phase shift cells for the maximum phase shift setting of said phase shift controlling means is less than said period T, so that the incremental phase shifts produced by the respective cells correspond to a polyphase distribution within the period T.  
  2. An aperiodic generator of&#39;polyphase signals as defined in claim 1 in which said period T is a substantially constant repetition period of said single phase input signal, in which the increments phase shift produced by the respective phase shift cells are equal, and in which said phase shift controlling means supplies an additional current only to said first cell.