| 摘要 |
PURPOSE:To prevent a carrier from leakage by detecting a pedestal potential of a chrominance signal, modulating a signal obtained by subtracting the pedestal potential from the chrominance signal and adding the pedestal potential to the modulated signal. CONSTITUTION:The chrominance signals R-Y, B-Y are inputted to chrominance signal input terminals 12, 15 and on/off switches 18, 19 are conducted during a fixed period of a blanking period under the control from control terminals 13, 16. Integrators 20, 21 integrate the input signal for a fixed period, an average value is obtained and a result is detected as the pedestal potential. Then, when the difference between the input chrominance signals R-Y, B-Y and the pedestal potential obtained from the integrators 20, 21 is obtained by subtracters 22, 23 to have relative data, the pedestal potential of the chrominance signal constantly goes to 'O'. Then, the outputs from the subtracters 22, 23 are respectively balance modulated by balanced modulators 24, 25, and added in an adder 26 to make a balance-modulated chrominance signal. The chrominance signal is added with a luminance signal in an adder 27 and outputted from a signal output terminal 28. Thereby, the carrier leakage is not leaked.
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