GB757290A - Improvements in or relating to pulse-modulation intelligence transmission systems - Google Patents

Abstract

757,290. Pulse code modulation. SOC. ALSACIENNE DE CONSTRUCTIONS MECANIQUES. Dec. 1, 1954 [Dec. 31, 1953], No. 34832/54. Class 40 (5). In a delta binary pulse code modulation communication system the comparison wave is derived by a weighted integration of the code pulses, full wave rectification of these integrated pulses, amplitude modulation of the original code pulses in accordance with the rectified integrated pulses, and integration of the amplitude-modulated pulses. Transmitter.-The incoming intelligence wave, to which a D.C. component has been added at 2, Fig. 1, to make it unidirectional, is sampled at 3 under the control of a pulse generator 5 and compared with the comparison wave to generate positive or negative pulses of variable amplitude which are clipped at 4 to form the pulse code train. The positive code pulses are passed by a gate 6 to the transmitter 8 and also to a mixer amplifier 10 to which the negative code pulses are passed by a gate 7 so as to reconstitute the code pulse train. This train is passed to the weighted integrator 10. This comprises Fig. 3 (not shown), a condenser, shunted by a resistor, and charged (or discharged) by the incoming code pulse train. The integrated pulses are rectified at 12 (whereby negative pulses are added to the positive pulses) and this signal is delayed at 13 by approximately half a pulse period before being used to amplitude modulate the original positive code pulses at 14 and the original negative code pulses at 15. The amplitude-modulated pulses are algebraically added by the integrator 16. This comprises, Fig. 4 (not shown) a condenser fed via diodes from a transformer with two primaries, one for each amplitude-modulated pulse train. The final integrated signal is rendered unidirectional by the addition of a D.C. component at 17 and fed back as the comparison signal for the comparator 3. Receiver.-The original code pulses are obtained from the incoming positive code pulses by the addition of locally generated negative pulses during the " off " periods. The code pulses are then integrated, rectified, and delayed to form an auxiliary signal which in turn is used to amplitude-modulate the code pulses, and this amplitude-modulated pulse train is integrated-as in the corresponding stages of the transmitter-but the final signal is now the demodulated intelligence wave which is amplified and passed via a low-pass filter to the output.