TW2864D datasheet(16/110 Pages) RENESAS

16 / 110 page

TW2864

FN7745 Rev. 0.00

Page 16 of 110

September 28, 2012

Color Decoding

CHROMINANCE DEMODULATION

The color demodulation for NTSC and PAL standard is done by first quadrature mixing the chroma signal to the base

band. A low-pass filter is then used to remove carrier signal and yield chroma components. The low-pass filter

characteristic can be selected for optimized transient color performance. For the PAL system, the PAL ID or the burst

phase switching is identified to aid the PAL color demodulation.

For SECAM, the color information is FM modulated onto different carrier. The demodulation process therefore

consists of FM demodulator and de-emphasis filter. During the FM demodulation, the chroma carrier frequency is

identified and used to control the SECAM color demodulation.

The sub-carrier signal for use in the color demodulator is generated by direct digital synthesis PLL that locks onto the

input sub-carrier reference (color burst). This arrangement allows any sub-standard of NTSC and PAL to be

demodulated easily with single crystal frequency.

Figure 5 shows the frequency response of Chrominance Low-Pass Filter Curves.

TW2864D Datasheet(PDF) 16 Page - Renesas Technology Corp