Description of video circuit
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1) DRX
Overview of DRX
The Digital Receiver Front-end (DRX) performs the entire multi-standard Quasi Split Sound
(QSS) TV IF processing, AGC, video demodulation, and generation of the second sound IF
(SIF) requiring only one SAW filter.
All control functions and status registers are accessible via I2C bus interface. Therefore, it
simplifies the design of high-quality, highly standardized IF stages.
For pre-filtering, one 8-MHz channel SAW filter must be used.
TV signal Ë Tuner(TU1) Ë SAW-filter(S3) Ë 72 & 73 pin of VCTI(IC 29) Ë DRX of VCTI
Features
- Multi-standard QSS IF processing with a single SAW
- Programmable IF frequency (38.9 MHz, 45.75 MHz, 32.9 MHz, 36.125 MHz, 58.75 MHz.)
- Digital IF processing for the following standards: B/G, D/K, I, L/L’, and M/N
- Standard specific digital post filtering
- Standard specific digital video/audio splitting
- Standard-specific digital AGC and delayed tuner AGC with programmable tuner Take Over
Point
- Second SIF output with standard dependent pre-filtering and amplitude controlled output level
- Video demodulation
- Second SIF generation and AGC
Output of DRX : CVBS & SIF
