| 摘要 |
PURPOSE:To obtain a PAL system chroma signal by applying balanced modulation to a color difference linearly sequential signal, then delaying a modulated output signal by one horizontal scanning period, inverting the delayed output signal every other horizontal scanning period, and adding the inverted output signal and the modulated output signal with each other. CONSTITUTION:A color difference linearly sequential signal is reproduced with a DC current by a clamping circuit 20, and balanced-modulated by a modulator 21 with a clamping point for reference. Subcarriers SCR/B for modulation are so switched that subcarrier SC-R, SC-B are made coincident with color difference linearly sequential signals R-Y, B-Y by means of LINE SW pulses that come every other 1H. Then, an output signal from the modulator 21 is delayed by 1H by a 1H-delay line 23. reversal amplifier 25 inverts the phase of the R-Y, and a switch 27 switches modulated signals from the amplifier 25 and a buffer 26 at R-Y and B-Y using LINE SW pulses. An adder 28 adds an OH signal with a 1H signal, and thus a chroma signal of PAL system is formed.
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