| 摘要 |
PURPOSE: To perform signal generation by a DDS circuit suitable for being used in a multi-color TV receiver at a low cost. CONSTITUTION: Sine wave signals sampled from the output of the DDS circuit 50 are inputted to one side of the phase comparator 11 of a PLL circuit 10 constituted of the phase comparator 11, a loop filter 12 and a sine VCO 13. The comparison output of the phase comparator 11 is smoothed in the loop filter 12 and inputted to the sine VCO 13. The output of the sine VCO 13 is inputted to the other input of the phase comparator 11 and turned to sine wave output to an outside. A TV system discrimination circuit 20 for discriminating colors and black-and-white inputs a discriminated result as the state control signal of the PLL circuit 10. This signal generation circuit suitable for being used in the multi-color TV receiver is realized at a low cost. |
