VDP 31xxB
PRELIMINARY DATA SHEET
2.3. Color Decoder
2.3.1. IF-Compensation
In this block, the standard luma/chroma separation and
multi-standard 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 sub-
carrier 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.
2–5. The luma as well as the chroma processing, is
shown here. The color decoder provides also some spe-
cial modes, e.g. wide band chroma format which is in-
tended for S-VHS wide bandwidth chroma.
– 12 dB/octave
– 10 dB/MHz
If the adaptive comb filter is used for luma chroma sepa-
ration, the color decoder uses the S-VHS mode proces-
sing. The output of the color decoder is YC C in a 4:2:2
The last setting gives a very large boost to high frequen-
cies. It is provided for SECAM signals that are decoded
using a SAW filter specified originally for the PAL stan-
dard.
r
b
format.
Fig. 2–4: Frequency response of chroma
IF-compensation
Notch
Filter
Luma / CVBS
Luma
Chroma /C C
r
b
1 H Delay
Cross-Switch
ACC
IF Compensation
DC-Reject
Lowpass Filter
Phase/Freq
MIXER
Demodulator
Chroma
Color-PLL/Color-ACC
Fig. 2–5: Color decoder
10
Micronas
MICRONAS [ MICRONAS ]
