Patent GB-1149048-A (GB)
Title: Improvements in or relating to function generators
Inventor: BALIGUET MICHEL PAUL
IPC: G06G7/25
Filed: 1966-10-25
Abstract: 1,149,048. Function generators. SOC. NATIONALE D'ETUDE ET DE CONSTRUCTION DE MOTEURS D'AVIATION. 25 Oct., 1966 [26 Oct., 1965], No. 47835/66. Heading G4G. An electric analogue function generator comprises plural units developing functions which are summated to provide a required function; the units providing one or other of the functions (I) y = a(x - α) Y(x - α) (II) y = a(x - α) Y(α - x) (Figs. 1, 2, not shown) wherein y is the output amplitude a is a coefficient x, α are the input amplitudes Y(x - α) Y(α - x) are Heaviside step functions wherein Y(x - α) = 0 for x < α = 1 for x > α Y(α - x) = 0 for > α = 1 for x < α. Fig. 3 shows a function generating unit wherein signal x represents an input variable and signal α an inital value, and are applied to a subtracting circuit 1 producing a different signal (x - α) applied over gate 2 to amplifier 3 and output y; a circuit 4 effecting a phase or polarity comparison between (x - α) and α and controlling the gate to conduct only when x > α for function I when (x - α) and α are of similar polarity or phase, or when x < α for function II when (x - α) and α are of opposite polarity or phase; the signals being D.C., or A.C. of similar waveforms. In Fig. 4 (not shown), an amplifier is interposed between the output of the subtractor and the comparison circuit to deliver a positive direct voltage when (x - α) and α are in phase or polarity coincidence, and a negative voltage when in phase or polarity opposition; and a polarity sensitive trigger opens or closes the gate in accordance with the sign of the comparator voltage; the output amplifier having complementary outputs for Œ y. In a modification (Fig. 5, not shown) a D.C. restoration capacitor is connected between the output of the subtractor and the input of the gate, which is shortcircuitable to earth over a switch operated by the output of the comparator and the gate input signals are held positive (or negative) with regard to earth at an amplitude of (x - α) referred to zero datum. The comparator opens the gate during positive excursions of α while α and (x - α) or α and (α - x) are similar in phase or polarity, and the gate remains closed if they are opposed. In a further modification (Fig. 7, not shown) the subtractor is capacitance connected to the input of the output amplifier, which is earthed over a transistor whose base is controlled by a phase comparator comprising a two diode OR gate such that when (x - α) and α are in phase (Fig. 6, not shown) the diode circuit conducts on alternate half cycles to open the transistor to earth, and non conducts on intervening half cycles to close it. Alternatively, when (x - α) and α are antiphased the diode circuit conducts continually and holds the transistor open, so that no signal is directed to the output. In a further modification (Fig. 8, not shown) wherein signal x (or α) is D.C. and signal α (or x) is A.C., the signals are applied to an adder circuit whose output energizes a polarity detector circuit. This develops a D.C. signal of similar sign to the minimum voltage of signal (x + α) and energizes a latch circuit combined with an amplifier together with a signal x<SP>1</SP> or α1 identical with the alternating input signal and in phase or antiphase therewith, so that positive or negative signals pass to the amplifier in dependence on the sign change introduced by the amplifier, or upon the phase of signal x<SP>1</SP> or α<SP>1</SP>; to generate either function I or function II as required (Figs. 9, 10, not shown). Required functions may be synthesized by directly summing straight line segments (Figs. 14 to 17, not shown) wherein ramp function signals are derived in opposed senses from units A, B, C and are selectively combined in adders; positive A being added to negative B and positive B being added to negative C; the outputs of the adders being further combined in a further adder, or alternatively by directly summing ramp function signals derived from the units described, whose values are zero below an initial level and are otherwise equal to the input signal less the initial value. The outputs of several units A, B, C, D responsive to a single input are summed over corresponding variable series resistances R A ,R B , R C ,R D , establishing the gradients applied to the several functions (Fig. 12).