ADVANCE INFORMATION
VDP 313xY
2.4. Color Decoder
2.4.1. IF-Compensation
In this block, the standard luminance/chrominance
(luma/chroma) separation and multistandard color
demodulation is carried out. The color demodulation
uses an asynchronous clock, thus allowing a unified
architecture for all color standards.
With off-air or mistuned reception, any attenuation at
higher frequencies or asymmetry around the color
subcarrier is compensated. Four different settings of
the IF-compensation are possible:
– flat (no compensation)
– 6 dB/octave
A block diagram of the color decoder is shown in
Fig. 2–3. The luminance as well as the chrominance
processing, is shown here. The color decoder provides
also some special modes, e.g. wide band chrominance
format which is intended for S-VHS wide bandwidth
chrominance.
– 12 dB/octave
– 10 dB/MHz
The last setting gives a very large boost to high fre-
quencies. It is provided for SECAM signals that are
decoded using a SAW filter specified originally for the
PAL standard.
If the adaptive comb filter is used for luminance/
chrominance separation, the color decoder uses the
S-VHS mode processing. The output of the color
decoder is YCRCB in a 4:2:2 format.
Fig. 2–2: Frequency response of chrominance IF-com-
pensation
Notch
Luma
Filter
Luma / CVBS
Chroma
1 H Delay
CrossSwitch
ACC
Lowpass Filter
IF Compensation
Phase/Freq
Mixer
DC-Reject
Chroma
Demodulator
ColorPLL/ColorACC
Fig. 2–3: Color decoder
Micronas
9
MICRONAS [ MICRONAS ]
