Method and device for modulating television signals, especially those of the D2-MAC-packet type.

摘要

Method of frequency-modulation from a video modulating signal with time-division multiplexing which is partly analog and partly digital for each line, with transmission of the continuous component of the modulating signal, characterised in that: (a) there is extracted from the modulating signal, with each line, a time window (COM) framing the digital part of the signal and a clamping window framing the clamping period provided with each line outside of the line 625 of the frame blanking; (b) the modulating signal is baseband processed in order to clamp it during the said clamping window and perform an energy dispersion with predetermined period, and possibly a preaccentuation of the signal; (c) the processed signal is applied to the input of a voltage-controlled oscillator which supplies the modulated signal to an output; (d) a fraction of modulated signal is sampled for the duration of the time window (COM) and is subjected to discrimination and filtering in order to obtain an error signal from which automatic control of frequency of the oscillator is carried out. The circuit can be used in particular to modulate a signal of the D2-MAC/PACKET type. <IMAGE>