| 摘要 |
PURPOSE:To completely minimize the output level of subcarrier, by converting a subcarrier to a rectangular wave by a comparator while preventing a phase shift and then controlling the amplitude through a clipping circuit. CONSTITUTION:The input subcarrier S1 of a sine wave passes through a coupling capacitor 1 and is compared with the earth potential of average value of the subcarrier by a comparator 2 and then converted to a rectangular wave S2. In this case, the comparison with the center value is given to prevent the occurrence of a phase change during a conversion to the rectangular wave. The output S2 of the comparator 2 is supplied to a clipping circuit 3, and then the amplitude is controlled (S3) according to the control voltage. The rectangular wave S3 having the controlled amplitude is turned again to a sine wave through a band pass filter 4 to be delivered. |
