| 摘要 |
PURPOSE: An NTSC digital color modulating apparatus and method are provided to demodulate a modulated in-phase signal having the bandwidth of 1.5MHz and to improve resolution of the in-phase signal so as to output vivid colors. CONSTITUTION: An NTSC digital color modulator includes the first latch(21) for receiving a demodulated chrominance signal to latch a quadrature-phase signal according to the first clock, and the second latch(31) for receiving a demodulated chrominance signal to latch a demodulated in-phase signal according to the second clock. The modulator further includes the first low pass filter(22) for receiving the signal of the first latch to output a quadrature-phase signal in a predetermined frequency band, and a low pass filter(10) for accepting the signal of the second latch to output an in-phase signal in a predetermined frequency band. The low pass filter has the second low pass filter(11) for receiving the signal of the second latch, the first delay matching unit(12) for matching the output signals of the second latch and the second low pass filter with each other, a subtractor(13) for subtracting the output signal of the second low pass filter from the output signal of the first delay matching unit, an amplifier(14) for amplifying the output signal of the subtractor, and an adder(15) for adding up the output signals of the amplifier and the second low pass filter. The amplitude of the radio-frequency portion of the in-phase signal output from the low pass filter becomes identical to the amplitude of the low-frequency portion.
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