VERFAHREN UND VORRICHTUNG ZUM MODULIEREN VON FERNSEHSIGNALEN NACH DER D2-MAC-PAKET-NORM.

摘要

A video signal intended for direct transmission via a satellite is applied simultaneously to a synchronisation development stage (10) and a base treatment unit (12). The latter's output passes through a controllable attenuator (14) to frequency-modulate an oscillator (16) feeding an amplifier (18) and a transposition stage (20). In addition to a frequency-modulating input, the oscillator (16) receives a control signal from a phase-locked loop (22) which serves to stabilise its mid-frequency. The transposition stage (20) refines the resulting modulated output and converts it to the final modulation frequency band required. The output finally produced includes a time window covering a digital element of the input signal, and a clamping period developed by the treatment unit (12). The latter produces a mean signal level of appropriate value, and can provide pre-accentuation if required.