Datasheet

Functional Description
10
May 2006SLES043A
f − Frequency − MHz
−40
−35
−30
−25
−20
−15
−10
−5
0
5
10
01234567
No Notch Filter
Notch3 Filter
Notch1 Filter
f − Frequency − MHz
−40
−35
−30
−25
−20
−15
−10
−5
0
5
10
01234567
Amplitude − dB
Amplitude − dB
Figure 3−3. Chroma Trap Filter Frequency
Response, NTSC ITU−R BT.601 Sampling
Figure 3−4. Chroma Trap Filter Frequency
Response, PAL ITU−R BT.601 Sampling
Notch2 Filter
No Notch Filter
Notch2 Filter
Notch1 Filter
Notch3 Filter
3.7 Color Low-Pass Filter
In some applications, it is desirable to limit the U/V bandwidth to avoid crosstalk. This is especially true in case
of nonstandard video signals that have asymmetrical U/V sidebands. In this case, notch filters are provided
that limit the bandwidth of the U/V signals.
Notch filters are needed when the comb filtering turns off, due to extreme color transitions in the input image.
The response of these notch filters is shown in Figure 3−5. The notch filters have three options that allow three
different frequency responses based on the color frequency characteristics of the input video.
f − Frequency − MHz
−70
−60
−50
−40
−30
−20
−10
0
10
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
Amplitude − dB
No Notch Filter
−3 dB @ 1.412 MHz
Notch3 Filter
−3 dB @ 554 kHz
Notch2 Filter
−3 dB @ 844 kHz
Notch1
Filter −3 dB
@ 1.03 MHz
Figure 3−5. Color Low-Pass Filter With Notch Filter Characteristics, NTSC/PAL ITU−R BT.601 Sampling