Digital Signal Processing Reference
In-Depth Information
wards the band edges optimizes the eye opening of the modulated signal.
After power amplification, the signal is then injected into the broadband
cable system.
RF from
cable
47...862
MHz
I
I
RF/IF
down
converter,
tuner
IF
Matched
filter &
equalizer
QAM
demod.
Different.
decoder
SAW
Q
Q
Carrier and clock recovery
Energy
dispersal
and
sync inv.
removal
Convol.
de
inter
leaver
Reed
Solomon
decoder
Base
band
interface
MPEG2
TS
De
mapper
Fig. 16.3.
DVB-C receiver
16.3 The DVBC Receiver
The DVB-C receiver - set-top box or integrated - receives the DVB-C
channel in the 50 - 860 MHz band. The transmission has added effects due
to the transmission link such as noise, reflections and amplitude and group
delay distortion. These effects will be discussed later in a separate Section.
The first module of the DVB-C receiver is the cable tuner which is es-
sentially identical with a tuner for analog television. The tuner converts the
8 MHz-wide DVB-C channel down to an IF with a band center at about
36 MHz. These 36 MHz also correspond to to the band center of an analog
TV IF channel according to ITU standard BG/Europe. Adjacent channel
components are suppressed by a downstream SAW filter which has a
bandwidth of exactly 8 MHz. Where 7 or 6 MHz channels are possible, the
filter must be replaced accordingly. This band-pass filtering to 8, 7 or 6
MHz is followed by further downconversion to a lower intermediate fre-
quency in order to simplify the subsequent analog/digital conversion. Be-
fore the A/D conversion, however, all frequency components above half
the sampling rate must be removed by means of a low-pass filter. The sig-
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