Promax PRODIG-5 - DVB-S Signals

USER’S MANUAL. PRODIG-5
Page 56 11/2006
5.14.5.3 DVB-S signals
Once determined the parameters of QPSK signal, it will be possible to measure
BER. Following is shown the BER measurement before the error corrections: BER
before the FEC: CBER.
-6 -5 -4 -3 -2 -1
MPEG-2
FREQ:
DL-Ku:
CH:
1781.94
12382.0
MHz
5037 kHz
MHz
MHz99
C/N:
POWER:
MER:
» CBER:
VBER:
dB
dBµV
dB
0.2
51.5
10.9
9.7E-4
5.2E-8
Figure 31.- Screen of CBER measurement (QPSK signals).
In a digital reception system for satellite signals, after the QPSK decoder two
different correction methods are applied (see following Figure). Obviously, each time we
apply an error corrector to a digital signal, the error rate changes, therefore if we
measure in a digital satellite television system, for example, the error rate at the output
of the QPSK demodulator, at the output of the Viterbi decoder, and at the output of the
Reed-Solomon decoder, we obtain nothing more than different error rates. This is the
reason because the BER measurement is provided before FEC, after Viterbi (VBER).
Figure 32.- Digital reception system via satellite.