Terrestrial Transmission of Digital Television Signals (DVB-T) - Digital Video and Audio Broadcasting Technology - page 357

This, however, requires a further converter stage from a lower intermediate
frequency to the final RF which is more complex and costs more and,
therefore, is usually avoided today. On the other hand, this advantage is
gained at the expense of the possibly unpleasant characteristics of an ana-
log I/Q modulator, the presence of which can virtually always be detected
in the output signal. Given the correct implementation, however, it is pos-
sible to manage direct modulation from baseband to RF (Fig. 20.11.).

TS

Time
sync

Analog frontend

FFT window

Low
pass
filter

SAW
filter
(BP)

RF A

Delay

FFT

IF D FIR

LO 90

Chan.
estim.

Scatt.
pilots

Clock

NCO

(f ZF2 = f s /4)

f s = 4 * 32/7 MHz

Cont.
pilots

Frequ.
corr.

TPS
carrier

TPS
dec.

Fig. 20.12. Block diagram of a DVB-T receiver (part 1)

20.6 The DVBT Receiver

One may think that the DVB-T modulator is a rather complex device but
the receiving end is even more complicated. Due to the high packing den-
sity of modern ICs, however, most of the modules of the DVB-T receiver
(Fig. 20.12.) can be accommodated in a single chip today.
The first module of the DVB-T receiver is the tuner. It is used for con-
verting the RF of the DVB-T channel down to IF. In its construction, a
DVB-T tuner only differs in being required to have a much better phase
noise characteristic. The tuner is followed by the DVB-T channel at 36
MHz band center. This also corresponds to the band center of an analog