Comb Filter - Sanyo AVM-2550S Training Manual

The VB7C chassis (AVM-2780G) provides for the 2-line digital Y/C separation
IC to separate luminance (Y) and chrominance (C) signals from the composite
video signal by using 2 horizontal (H) lines separation. The Y/C separation
unit for TV set requires few external parts and no adjustment.
(1) Input Clamp
This is a sync tip clamp circuit for composite signal. This circuit makes
feedback so that the minimum data after A/D conversion and at Y/C
separation equals an internal DC bias level.
(2) A/D Converter (ADC)
This is high speed series-parallel 8 bit A/D converter. Recommended Input
level is 0.75 Vp-p (Sync chip ~ white 100%).
(3) Line Memory
This block is DRAM line memory for 1H delay.
(4) Band-Pass Filter (BFP)
This filter extracts the signal of chrominance band from composite video
signal. The center frequency is fsc.
Composite
Video In

COMB FILTER

4 ADC
Clamp
1H Line
Memory
fsc
PLL System Clock
10
(5) Dynamic Comb Filter (DCF)
This block is logical comb filter to extract the chrominance signal. Filtering
logic applies a correlation of two lines to reduce color dot crawl and cross
color.
(6) Color Killer Circuit (Killer)
This block is applied for black and white (B/W) signals which have no color
burst. When pin 10 (Killer) is "H," logic stops Y/C separation and outputs
composite video signal from pin 15 (Y out).
(7) PLL (4 Times Multiply Clock Generator)
This block is a 4 times multiplier and makes 4fsc the system clock. This
block supplies the system clock (4fsc) to each block via buffers and
generates timing signals for memories.
(8) D/A Converter (DAC)
This is high speed 8 bit D/A converter. Y output level is 1.73 Vp
C output level is 437 mVp-p (Typ.). (Input condition is 0.75 Vp-p)
+
Color
BPF
Killer
Dynamic
Comb Filter
BPF
BPF
– 63 –
DAC
15 Y Output
7 Color Killer
C Output
DAC 13
p (Typ.).
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