| 摘要 |
PURPOSE:To discriminate a frequency stably against the fluctuation of the frequency of the color subcarrier, by utilizing the fact that the level radio of two kinds of spectrum becomes infinite in the valley part of spectrums. CONSTITUTION:An input horizontal synchronizing signal fH including frequency variation DELTAf is multiplied in a PLL multiplying circuit 32 by an integral multiple to obtain a signal which is equal to one of two frequencies of the color subcarrier and is synchronized with the horizontal synchronizing signal, and the sum of this obtained signal and a reference frequency fS from an oscillator 36 is obtained by a frequency converter 34. The difference between the output signal from the converter 34 and the burst gated color subcarrier frequency from a terminal 40 is operated by a frequency converter 38, and frequency variation DELTAf is eliminated to obtain frequencies fS and fS+10fH. Next, a valley of the frequency spectrum of the frequency fS or fS+10fH is obtained, and its frequency is used as a center frequency for discrimination of an SECAM signal. |
