SDA9280 Datasheet, PDF (13/43 Pages) Siemens Semiconductor Group – ICs for Consumer Electronics

SDA 9280 B22
Interpolation filtering can be switched off for each stage separately (Ι²C signals: INT422,
INT444). Then each sample is simply repeated twice. Activation of interpolation filtering
is recommended because analog postfiltering of chrominance signals then can be
greatly simplified (see also Interpolator 2).
2.3 Luminance Peaking Filter
The luminance peaking filter improves the over all frequency response of the luminance
channel. It consists of three filters working in parallel. They have low pass (LP(z)), band
pass (BP(z)) and high pass (HP(z)) characteristics. Their gain factors are separately
programmable (Ι²C signals: LCOF, BCOF, HCOF) according to the following equations:
LCOF _* LP(z) + BCOF _* BP(z) + HCOF _* HP(z)
with:
LCOF = 0 ... [1/4] ... 3/2, 2
BCOF = 0 ... [1/4] ... 3, 7/2, 4, 5
HCOF = 0 ... [1/4] ... 3, 7/2, 4, 5
LP(z) = 1/16 _* (1 + z^-1)⁴
BP(z) = -1/8 _* (1 - z^-2)²
HP(z) = 1/16 _* (1 - z^-1)⁴
An amplification of up to 14 dB at the half of the sample frequency is available. The high
pass and band pass filters are equipped with a common coring algorithm. It is optimized
to achieve a smooth display of grey scales, not to improve the signal-to-noise ratio.
Therefore no artifacts are produced. Coring can be switched off (Ι²C signal: COR).
Note: The peaking filter may shift the black level of the signal. This has to be considered
for black level insertion (see Insertion Facilities).
A delay line for the luminance signal enables an adaption to the delay of the chrominance
signals. A range of -8 to +7 clock periods of the system clock CLL is programmable
(Ι²C signal: YDEL1).
An additional special filtering is available for compensating a non linear phase response
of the analog part of the signal path.
(1 + PHACOM) _* z^–1 - PHACOM
Three adjustments are Ι²C-Bus programmable: PHACOM = 0, 1/4, 1/8.
Semiconductor Group
13
1998-02-01