| 摘要 |
PURPOSE:To prevent degrading of S/N because of mixing noise from a chrominance signal system into the illuminance signal of a composite color television signal by adding a base noise clipping circuit to eliminate low-level chrominance signals to the circuit of the chrominance signal system. CONSTITUTION:In the base noise clipping circuit 7, a carrier chrominance signal is amplitude-amplified by an amplifier 9a, and by a limiter circuit 9 in the following stage, only such signal components, for instance, as equal to or lower than a slicing level Th are extracted. In thus extracted low level signals, noise components are included together with chrominance signal components. These low-level components are phase-inverted by an inverter circuit 9c in the following stage, then attenuated to a suitable level by an attenuator R2, and supplied to an adding circuit 9d. In such a manner, the low-level components are eliminated from the carrier chrominance signal supplied to the adding circuit 9d and a new carrier chrominance signal is thus formed. Accordingly, this signal is synthesized with the illuminance signal components by an adding circuit 10. As a result, the S/N of an illuminance signal can be upgraded.
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