PURPOSE: To detect the phase pulse of an I axis from a sampling point of a chroma signal by a digital circuit.
CONSTITUTION: A chroma signal S1 (sampling frequency f1) is sub-sampled by a sub-sampling pulse generated from an N-phase sub-sampling pulse generator 10 shifting frequency f2, (f1/N) in each clock (1/f1) and the sub-samplied output is inputted to an I axis judging circuit 17. The circuit 17 detects the minimum value M1 of a color burst signal (sampling frequency f1) and data M2 obtained at one clock before the value M1 and mutually compares the detected values M1, M2 to detect a signal S4 for selecting the phase pulse of the I axis obtained from the sampling point of the chroma signal. A selector circuit 18 selects one of sampling pulses of N phases based upon the selection signal S4 and inputs the selected pulse to the (N+1)th sub-sampling circuit 19 as an I axis phase pulse S5 to obtain an I axis detecting output S3 from the sampling point of the chroma signal S1.
TSUJI TOSHIAKI
IMAI KIYOSHI
