GB586632A - Improvements relating to the amplification of power in a train of duration-modulatedpulses - Google Patents

Abstract

586,632. Pulse modulation. STANDARD TELEPHONES & CABLES, Ltd., CHATTERJEA, P. K., and SCULLY, C. T. Sept. 3, 1943, No. 14453. [Class 40 (v)] In a duration-modulated pulse signalling system, both the power level and the degree of modulation are increased by interpolating replicas of the original modulated pulses in the gaps between them. As shown in Fig. 7, the modulated pulses are fed through an amplifier 32 to a delay circuit, and are reflected at its open terminals 34 so as to add delayed pulses to the input of the further amplifier 27. As the delayed pulses are weaker than the original, the amplifier 27 may operate as a limiter supplying pulses all of the same amplitude to the output terminals 33. By using several delay circuits, connected in parallel and with progressive delay periods, further pulses may be interpolated. Alternatively the delay circuits may operate in series with interposedisolating amplifiers (Fig. 8, not shown). In the modified arrangement of Fig. 5, the modulated pulses are used to synchronize a saw-tooth generator 21 operating only during the pulse gaps, the saw-tooth period being slightly longer than the maximum width of the modulated pulses. The input pulses are also applied to a storage or integrating circuit 22 including a condenser which is charged to a level dependent on the duration of the applied pulse. This condenser is discharged just before the arrival of the succeeding pulse bya discharge circuit 26 operated by the control circuit 25 which is synchronized by the incoming pulses. The saw-tooth wave and the voltage on the storage condenser 22 are applied to an amplifier limiter 23 which passes pulses corresponding to the tips of the saw-tooth wave to a further amplifier 24 which is also fed with the original pulses. Detailed circuits operating according to Fig. 5 are described in the Specification (Fig. 9, not shown). Specifications 579,118, [Group XXXVIII], and 582,324 are referred to.