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VPX3226E 参数 Datasheet PDF下载

VPX3226E图片预览
型号: VPX3226E
PDF下载: 下载PDF文件 查看货源
内容描述: 视频像素解码器 [Video Pixel Decoders]
分类和应用: 解码器
文件页数/大小: 92 页 / 610 K
品牌: MICRONAS [ MICRONAS ]
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VPX 322xE  
ADVANCE INFORMATION  
dB  
2.3. Color Decoder  
10  
5
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.  
0
–5  
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 also provides several  
special modes; for example, wide band chroma format  
which is intended for S-VHS wide bandwidth chroma.  
–10  
–15  
–20  
The output of the color decoder is YC C in a 4:2:2 for-  
r
b
3.5  
3.75  
4
4.25  
4.5  
4.75  
5
MHz  
mat.  
Fig. 2–4: Freq. response of chroma IF-compensation  
2.3.1. IF-Compensation  
2.3.2. Demodulator  
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:  
The entire signal (which might still contain luma) is now  
quadrature-mixed to the baseband. The mixing frequen-  
cy is equal to the subcarrier for PAL and NTSC, thus  
achieving the chroma demodulation. For SECAM, the  
mixing frequency is 4.286 MHz giving the quadrature  
baseband components of the FM modulated chroma.  
After the mixer, a lowpass filter selects the chroma com-  
ponents; a downsampling stage converts the color dif-  
ference signals to a multiplexed half rate data stream.  
– flat (no compensation)  
– 6 dB/octave  
– 12 dB/octave  
– 10 dB/MHz  
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.  
The subcarrier frequency in the demodulator is gener-  
ated by direct digital synthesis; therefore, substandards  
such as PAL 3.58 or NTSC 4.43 can also be demodu-  
lated.  
Luma  
Notch  
Filter  
Luma / CVBS  
Chroma  
Cross-  
Switch  
1 H Delay  
ACC  
Lowpass Filter  
Phase/Freq.  
Demodulator  
IF Compensation  
DC-Reject  
Chroma  
MIXER  
Color-PLL/Color-ACC  
Fig. 2–5: Color decoder  
MICRONAS INTERMETALL  
11