Patent GB-760602-A (GB)
Title: Electrical apparatus for multiplication of two functions
IPC: G06G7/16
Filed: 1953-12-30
Abstract: 760,602. Electric analogue calculating apparatus. SOCONY MOBIL OIL CO., Inc., [formerly SOCONY-VACUUM OIL CO., Inc.]. Dec. 30, 1953 [Jan. 7, 1953], No. 36199/53. Class 37. An electric calculating apparatus multiplies two input functions f1, f2 by developing analogue voltages thereof, adding an oscillatory voltage to the analogue voltage of function f1 to produce analogue voltage S1, additively combining the latter in an electron discharge tube sense discriminating summation circuit with the analogue voltage S2 of the input function f2 to derive an analogue voltage given by | S1+S2 | - | S1 - S2 |, and separating from such analogue voltage by filter means the oscillatory component whereby the remaining unidirectional component is the analogue voltage of the product f0; the added oscillatory voltage being of frequency differing from the input functions and of amplitude less than the sum thereof. The first input voltage is additively combined with an oscillatory waveform (which may be a sawtooth) which is symmetrical and of sloping profile with regard to the zero axis to produce the combined signal S1 while the second input voltage signal S2 is combined therewith to give composite signals (S1 + S2) and (S1 - S2) which are respectively applied in opposite phases to the anodes of diodes 19, 20 (Fig. 1) and to the cathodes of diodes 16, 17, whose respective cathodes and anodes are interconnected by potentiometer 18 whose slider (adjustable for balance) is earthed over load resistance 15. A pulsating voltage at carrier frequency appears across the latter, given by (S1+S2) | - | (S1 - S2) | (Figs. 2, 3, not shown), whose unidirectional value when filtered free of carrier components is proportional to the product of the input signals, which may be unidirectional or complex. In Fig. 4 the combined signal S1 is applied to the primary of transformer 30 whose centre tapped secondary is connected in series with the secondaries of transformers 31, 33, energized by input signal S2 in series with the primaries of transformers 32, 34. The secondaries of the latter are respectively connected between the junctions of the secondaries of transformers 30, 31 and 30, 33 and the cathodes of diodes 16, 17, while the anodes of diodes 19, 20 are connected to the free ends of the secondaries of transformers 31, 33. Combination waveforms derived from signals (S1+ S2) and (S1 - S2) are applied to the diodes as in Fig. 1 while resistance 18 connects the respective anodes and cathodes, and is centre tapped to earth over resistance 15 to derive the pulsating voltage whose amplitude, less carrier components, is proportional to the product of the inputs. Fig. 5 shows a development wherein a first input signal at terminal 40 and a carrier signal at terminal 41 are added at the grid of mixing triode 44, amplified by triode 47, and phase split by triode 49 to develop corresponding antiphase voltages across resistors 50, 51 to drive push-pull pentodes 54a, 54b, whose output transformer 55 has a feedback secondary 55c in the cathode return of triode 47. Similarly the second input signal is amplified by triode 58, and phase split by triode 60 to drive push-pull pentodes 65a, 65b whose output transformer 66 has a feedback secondary 66c in the cathode return of triode 58. Secondaries 55a, 55b in series develop the combined signal S1 across resistance 56 centre tapped to earth, while the secondaries of transformer 66 develop signals S2 across resistances 67, 68, and are respectively connected in appropriate phase to the anode of diode 19 and the cathode of diode 16, and to the cathode of diode 17 and the anode of diode 20. The respective anodes and cathodes are connected to opposite ends of resistance 18 centre tapped to earth over resistance 15, while the free ends of secondaries 55a, 55b are connected to the respective centre taps of resistances 67, 68 so that signals | S1+S2 |, | S1 - S2 | are applied in appropriate phase to the diodes as described above. The pulsating signal across resistance 15 is applied to the slider of potentiometer 75, connected over reversing switch 91 to the cathode and anode of diode connected triode 90, which introduces a thermal agitation voltage adjustable in magnitude and sense to balance out any similar residual voltage arising in the diode network; and is also connected to voltmeter 78 and to an adjustable low-pass filter comprising resistance 79 in series with one of a range of capacitors 81 to 84 selectible by switch 85 to remove carrier frequency components, leaving a unidirectional voltage across terminal 80 representing the product of the functions represented by the input signals. In modifications, the appropropriately phased combinations (S1+S2) and (S1-S2) of the signals S1, S2 for application to the diode network shown in Fig. 1 are derived from circuits comprising two pairs of transformer coupled mixing triode amplifiers (Fig. 7, not shown) and two parallel mixing and phase splitting triode amplifiers (Fig. 8, not shown), supplied with the individual signals S1 and S2. In a modification (Fig. 9, not shown) of the circuit shown in Fig. 1, the diodes 16, 17 are reversed and the pairs of cathodes are respectively connected to the inputs of corresponding triode cathode followers, between the cathodes of which the pulsating output voltage is developed. Fig. 10 shows a squaring circuit in which a carrier signal ec is applied over a phasesplitting transformer to the anode of diode 186 and the cathode of diode 187, and in antiphase to the anode of diode 188 and the cathode of diode 189. Anodes of diodes 187, 189 are connected over equal resistances to the secondary of output transformer 192, where centre tap is connected over equal resistances to the cathodes of diodes 186, 188, and whose primary is energized by an input signal e1. The secondary centre tap of transformer 192 is earthed over resistance 195, across which appears a voltage e0 which after removal of carrier frequencies is proportional to the square of the input signal. Fig.-11 shows a modification in which signals | S1+S2| and | S1 - S2 | respectively energize solenoids 209, 222 co-operating with armatures 205, 220 to adjust spring-loaded and oppositely energized potentiometers 201, 216 to derive unidirectional slider voltages respectively proportional to the absolute magnitudes | S1 + S2 | and - | S1 - S2 | which energize the grids of triodes 210, 223 having a common load resistance 212, across which a pulsating voltage is developed which after removal of carrier frequency components is proportional to the product of the input signals.