GB692461A - Improvements in or relating to circuit arrangements for converting amplitude modulated pulses into pulsating d.c. voltage - Google Patents

Abstract

692,461. Pulse modulation circuits. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. July 26, 1951 [July 26, 1950], No. 17766/51. Class 40 (v). A train of amplitudemodulated pulses (a), Fig. 2, is converted into a stepped D.C. wave (c), Fig. 4, by applying the modulated pulses to a polarity-inverting valve 1, Fig. 1, and by using both the input and output pulses to control the voltage on a condenser 3 from which the stepped D.C. wave is derived. In Fig. 1, the input pulses of negative sign, shown as produced by a generator 9 of low internal resistance Ri, are applied to the grid of the valve 1, and positive pulses are taken from the anode through a condenser 4. Three rectifiers 2, 5, 7 all conducting in the same direction, are connected in series between input terminal a, live terminal c of condenser 3, anode terminal b, and negative terminal of a bias source 6. When no pulses are present, the point a is at earth potential, and the point b at the negative potential V6 of the source 6. A negative input pulse (a), Fig. 2, gives rise to a positive-going pulse (b) at the point b which rises in voltage until it is slightly less negative than a, whereupon current passes through the rectifiers 5, 2 and the voltage at b ceases to rise. The voltage at c on the condenser 3 rapidly assumes a corresponding value. At the end of a pulse, a returns to earth potential and the voltage at b becomes more negative until limited to the value V6 by the rectifier 7. For the interval between pulses, the voltage at c remains steady owing to the high impedance offered by the rectifiers 2, 5 to a discharge current, with the result that the voltage at c follows the stepped form of Fig. 4.