Samsung DVD-R155 Service Manual page 126

Circuit Operating Descriptions
13-5 IF
1) SAW FILTER
It passes only needed band of the signal that is converted to IF frequency and decrease the others band to
minimize the effect of adjacent channel.
2) RF AGC Control
It used adjusting to determine RF AGC working point in tuner.
3) VCO Tank
When VCO tank detects PLL, it makes the signal which sets a standard.
4) AFT (Auto Frequency Tuning)
AFT automatically controls the oscillator frequency in the tuner, so that it retains a constant level.
It is a quadrature detection type. The carrier, which is detected from video det is directly input to AFT.
The 90 degree delayed phase signal is input at the same time to AFT and, the results come out.
5) IF AMP
IF signal , which is selected in Saw filter, is amplified in IF amp frequency enough to be detected. The IF amp
has parallel inputs & outputs structure.
13-26
Fig. 13-16
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