Digital transmission system with a coherent demodulation adapted to the simultaneous transmission of two binary signals

摘要

System making it possible to simultaneously transmit two binary messages and to ensure high security. On transmission it uses a differential coding (3-4) of each of the messages to be transmitted in binary form (M(t), T(t)) and their addition modulo-2 (7) is applied to a 0- pi phase modulator (1) which receives a high-frequency carrier (SP). On reception a conversion mixer (11) receives, conversely, a local wave which, to within the conversion frequency, reproduces the variations in the carrier frequency. The converted signal (So) is applied to two coherent differential demodulators (18, 23). Preferably use is moreover made of a generator (5) of a pseudo-random code (PA) which is added modulo-2 with the modulo-2 output (Y(t)) on transmission, the receiver being equipped with corresponding means (15, 16, 17) of decoding before transmission of the signal to the demodulators. IMAGE