Patent GB-990236-A (GB)
Title: Improvements in multiplying circuits suitable for electrical analog computing apparatus
IPC: G06G7/163
Filed: 1961-08-01
Abstract: 990,236. Controlled reactor circuits; impedance networks. COMPAGNIE GENERALE DE TELEGRAPHIE SANS FIL, and SOC. MAROCAINE DE RECHERCHES, D'ETUDES ET DE DEVELOPPMENTS SOMAREDE. Aug. 1, 1961 [Aug. 8, 1960], No. 27940/61. Headings H3B and H3U. By adjusting the control current of a network comprising controlled inductors and fixed capacitors, the network remains resonant at a predetermined frequency for all values of controlled output power dissipated in a load. In one arrangement, Fig. 9, comprising four controlled inductor units 15, 15<SP>1</SP>, 16, 161 and input and output capacitors 13, 14, the inductors are biased by a current I L  applied to control winding terminals 1, 1<SP>1</SP>, from a source E. The inductor unit pairs 15, 151 and 16, 161 are controlled in opposite respects by a control current Is applied to the control windings over a potentiometer R, and the inductors are varied over a range in which the flux-current relationship is linear. Either the control voltage source or the potentiometer setting may be varied to adjust the control current. In a modification, Fig. 12, only two of the inductor units shown in Fig. 9 are used, and are connected so that a mutual induction coupling is provided between the two coils of each unit. An arrangement using three controlled inductors 15, 16, 16<SP>1</SP> and having one commoned input and output terminal is shown in Fig. 14. Instead of parallel condensers across the input and output terminals, the input and output lines may include series capacitors 13, 13<SP>1</SP>, 14, 14<SP>1</SP> as shown in Fig. 16. Two inductor units having internal mutual inductance couplings may be used, Fig. 17 (not shown), as in the Fig. 12 arrangement. A modification of Fig. 16 uses only three inductor units, Fig. 19, one unit 18 being connected with a capacitor 17 between the lines. In the latter arrangement one input and output terminal may be commoned, Fig. 21 (not shown). A modification of Fig. 12 is described in which one of the mutually-coupled inductor units is shunted by capacitors, Fig. 22 (not shown). A circuit is described, Fig. 23, in which an arrangement as shown in Fig. 12 has a fourterminal network comprising capacitors 24, 25 and inductors 22, 23 connected to its output. The whole circuit 200 is resonant at a chosen frequency and functions as an amplifier of the control current. The circuit 200 may be operated with a feedback loop connected to a detector D, Fig. 25, the circuit being controlled by a signal amplified at A which is the difference between the control and feedback voltages X 0  and X. Two of the Fig. 23 circuits are used in Fig. 28, the difference signal from the amplifier A of one circuit being used to control the second circuit. Details of the inductor unit are shown in Fig. 5 in which a ferrite case 101 having a cover-plate 102 encloses a control coil 111 and reactor windings 112, 113. The latter windings are connected in series opposition to form the units used in Fig. 9, and are connected in separate paths in Fig. 12 for mutual inductance coupling. The characteristics may be modified by tapering the polepieces 103, 104, Fig. 30 (not shown). Specification 703,178 is referred to.