AC coupled sync separator system with filter DC feedback

摘要

A novel method and apparatus of AC coupling composite video sync information to a sync separator circuitry with digital controlled filtered DC feedback is described. An AC coupling circuit such as a capacitor provides an intermediate signal in response to received composite video. The intermediate signal may be level adjusted and gain provided to provide a first input to a sync slicer and an input to a sync filter. The output of the sync filter may provide a second input to the sync slicer circuit which responsively varies the reference level for the sync slicer in repsonse to variations in the level of the received composite video. DC feedback from the filter to the AC coupling circuit provides for a stabilization in the intermediate signal and in the filter output signal. These two signals ultimately provide the input to the sync slicer so that the composite sync is provided in response to all sync signals in spite of level variations in the sync tips in the received composite video signal.