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VCT3801A 参数 Datasheet PDF下载

VCT3801A图片预览
型号: VCT3801A
PDF下载: 下载PDF文件 查看货源
内容描述: 视频/控制/图文电视IC系列 [Video/Controller/Teletext IC Family]
分类和应用: 电视
文件页数/大小: 172 页 / 2219 K
品牌: MICRONAS [ MICRONAS ]
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ADVANCE INFORMATION  
VCT 38xxA  
2.4. Color Decoder  
If the adaptive comb filter is used for luma chroma sep-  
aration, the color decoder uses the S-VHS mode pro-  
cessing. The output of the color decoder is YCrCb in a  
4:2:2 format.  
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.  
A block diagram of the color decoder is shown in Fig.  
2–3. The luma as well as the chroma processing, is  
shown here. The color decoder provides also some  
special modes, e.g. wide band chroma format which is  
intended for S-VHS wide bandwidth chroma.  
Notch  
Filter  
Luma / CVBS  
Luma  
Chroma  
1 H Delay  
CrossSwitch  
ACC  
IF Compensation  
Low-pass Filter  
Phase/Freq  
Demodulator  
Mixer  
DC-Reject  
Chroma  
ColorPLL/ColorACC  
Fig. 2–3: Color decoder  
2.4.1. IF-Compensation  
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  
– 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.  
Fig. 2–4: Frequency response of chroma IF-com-  
pensation  
Micronas  
13  
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