SERVICE MANUAL
Document No
Date of Origin
Date of REV
51-L-DSR004
98-10-21
PAGE REV.
0
PAGE
14 /102
S-00-005(96.03.27)
REV.1
4-4. Dem o d u l a t o r & Cha n n e l Dec o d e r
The outcoming
I/Q signal from the tuner is tranfered
to the ADC (analouge
to
digital
conversion)
for QPSK demodulation.
This digital
data is then channel
decoded
to remove various
noise and error corrected
that can occur during
satellite
transmittion.
Channel
decoding
is accomplished
by VITEBI decoding(inner
FEC) and RS decoding
(outer FEC). Most RS decoders
have the function
for de-interleaving
and remove
energy dispersal.
4-4-1.
demodulation
method
:
QPSK
4-4-2.
inner FEC
:
VITERBI
convolution
4-4-3.
symbol rates
:
20 ~ 30 Msym/s,
step 0.1Msym/s
4-4-4.
symbol rate lock range
:
110 ppm
4-4-5.
convolutional
code rates
:
1/2, 2/3, 3/4, 5/6, 7/8. K=7
(depend
on BIT stream)
4-4-6.
outer FEC
:
reed solomon
decording
(204,188)
T=8
4-4-7.
bit error rate
:
1
¡¿
10
-11
max
4-4-8.
deinterleaving
:
convolutional,
depth I=12
4-4-9.
implementation
loss
:
¡Â
0.5 dB, 0.8 dB max
at AWGN, 4.1 dB < Rs/No < 8.5 dB
4-4-10.
data acquisition
time
:
¡Â
300 msec
