DEMODULATEUR SYNCHRONE POUR SIGNAUX MODULES EN AMPLITUDE

DEUX CIRCUITS DE BATTEMENT 1, 2 EFFECTUENT LE BATTEMENT DU SIGNAL MODULE S(T), L'UN AVEC UN SIGNAL SENSIBLEMENT ISOFREQUENTIEL S ET L'AUTRE AVEC LE MEME SIGNAL MAIS DEPHASE DE 90. UN COMMUTATEUR 6 COMMANDE PAR UN CIRCUIT DE COMMANDE 8 SELECTIONNE TANTOT L'UN, TANTOT L'AUTRE DES DEUX SIGNAUX RESULTANTS, EN FONCTION DE LEUR AMPLITUDE, DE MANIERE A EVITER LES PERTES D'INFORMATION DUES A DES PICS D'AMPLITUDE INFERIEURS A UN SEUIL PREDETERMINE, QUI PEUVENT ETRE DUS A DES ECARTS DE FREQUENCE ENTRE LES DEUX SIGNAUX MIS EN BATTEMENT. Two circuits carry out the beating of a modulated signal, with first and second signals, respectively, each having substantially the same frequency as the carrier of the modulated signal but phased-shifted relative to one another by 90 DEG . A commutator controlled by a control circuit alternately selects the signals resulting from the beating. The selection is responsive to the amplitudes of the signals in order to avoid losses of information due to amplitude peaks under a prefixed threshold which may be caused by frequency differences between the signals which are beat.