saa7191b NXP Semiconductors, saa7191b Datasheet - Page 8

• Manufacturer Part Number: saa7191b
• Description: Digital Multistandard Colour Decoder, Square Pixel Dmsd-sqp
• Manufacturer: NXP Semiconductors

Philips Semiconductors
7
7.1
The 8-bit chrominance input signal (CVBS or chrominance
format) passes a bandpass filter to eliminate DC
components and to decimate the sample rate before it is
fed to the two multipliers (quadrature demodulator), Fig.3.
Two subcarrier signals from a local oscillator (0 to 90
degree) are fed to the multiplicator inputs of the multipliers.
The multipliers operate as a quadrature demodulator for all
PAL and NTSC signals; it operates as a frequency
down-mixer for SECAM signals.
The two multiplier output signals are converted to a serial
data stream and applied to three low-pass filter stages,
then to a gain controlled amplifier. A final multiplexed
low-pass filter achieves, together with the preceding
stages, the required bandwidth performance. The signals,
originated from PAL and NTSC, are applied to a
comb-filter. The signals, originated from SECAM, are fed
through a Cloche filter (0 Hz centre frequency), a phase
demodulator and a differentiator to obtain
frequency-demodulated colour-difference signals.The
SECAM signals are fed after de-emphasis to a cross-over
switch, to provide the both serial-transmitted
colour-difference signals. These signals are fed finally to
the output formatter stages and to the output interface.
August 1996
Digital Multistandard Colour Decoder,
Square Pixel (DMSD-SQP)
FUNCTIONAL DESCRIPTION
Chrominance processor
8
Product specification
SAA7191B