SIL RANGE This range of
video oversampling analogue
filters has been designed for use in conjunction with a half band interpolating/decimating
filter such as the TRW2242 or with the many encoder chips available which employ digital
filtering combined with an output D/A converter. This type of digital filtering has
good attenuation between the frequencies of Fs/4 and 3Fs/4 where Fs is the Master Clock
rate. When the normal clock rate of 27 MHz is used for the luminance channel the signal
can be expected to have insignificant energy between 6.75 MHz and 20.25 MHz.
An analogue video oversampling filter is required to attenuate the clock and sideband to reconstruct the
signal. In order to preserve the integrity of the signal these filters have a good
amplitude and group delay characteristics in the passband, similar to the requirements of
CCIR601 but due to the above considerations do not need significant attenuation below 21
MHz. |
