Circuit for compensating disturbances generated by a masking signal in satellite television receivers

摘要

During the satellite transmission of television signals, a so- called dispersal signal is superimposed on the signal to be transmitted before it is frequency modulated. This dispersal signal causes unwanted changes in brightness and disturbances during synchronisation in the satellite television receiver. These are avoided by obtaining from the synchronising signal peaks of the demodulated satellite television signal an analog control voltage and adding this to the disturbed signal. The synchronising signal peaks are sampled at a time interval the duration of which is at the most equal to the duration of the pre- and post-equalising pulses in the video signal. Thus, correct samples characterising the amplitude of the dispersal signal can also be obtained during the vertical blanking interval. IMAGE