Testing method for color signal demodulating circuit

Abstract

Abstract PURPOSE:To test electric characteristics of an IC for PAL color signal processing by varying a color synchronizing signal only in phase at two kinds of specific angles at intervals of one horizontal synchronism, and generating a testing clock signal which has a color difference signal phase set at a prescribed angle. CONSTITUTION:Color synchronizing signals (burst) 10 and 10' of a chroma signal used for the PAL system are varied in phase at 130 or -135 deg. at intervals of one horizontal synchronizing signal, and those signals 10 and 10' are extracted from the chroma signal by using gate pulses which synchronize with pulses 11, thus obtaining input signals to the automatic phase control circuit 6 and collating circuit 9 of the chroma IC of a PAL color TV receiver. Further, color signals I and W which correspond to color difference signals B-Y and R-Y in the chroma signal are varied repeatedly to 0 deg. (I) and 90 deg. (Q) at intervals of one horizontal signal, and inputted to demodulating circuits 1 and 2. Further, a signal Y which corresponds to lightness is applied to a matrix circuit 4 and a horizontal synchronizing signal H is applied to an FF8. Then, the operation states of the PAL switch 7, FF8, and collating circuit 9 of an IC for color signal processing are tested electrically.

Inventors

• 👤 Ryozo Fujiwara
• 👤 藤原　良造

Bibliographic Details