Hyundai HSS-730, Service Manual

Page: 9 / 56

HSS-730/830 & UFD505/515 SERVICE MANUAL HDT DVB SATELLITE STB
Page 9
3.3. Network Interface Module
3.3.1. NIM Module
3.3.1.1. Block Diagram
The NIM module has digital tuner as depicted in the following figure.
3.3.1.2. Digital Network Interface Module Operating
The satellite RF input signal (1
st
IF) is connected to the tuner. The tuner down-converts the RF
signal to ZERO IF signal, and then generates the analog base band I(In-phase) and Q(Quadrature)
signals containing a QPSK modulated digital data. After passing the LPF and A/D converter, these
signals are demodulated by the QPSK demodulator into a digital data stream.
The satellite signal is relatively noisy and this may produce a high bit-error rate at the demodulator
output. The high demodulator bit-error rate will produce errors in the MPEG decoder that will in
turn lead to unsatisfactory audio/video quality. The FEC is needed to reduce the bit-error rate to an
acceptable level (bit-error rate of 10
-11
). The FEC used a Reed-Solomon decoder to reduce a burst
error and a viterbi decoder to correct a bit error.
RF Loop-through
Digital Tuner Module
Digital
Tuner
LPF
LPF
A/D Converter
QPSK
Demodulator
FEC
I
Q
AGC
Satellite
RF In
Transport
Stream
Control
I2C_0 100kHz
8
HSS-730 &
UFD505 :
STi5518BVB-X
HSS-830 &
UFD515 :
STV0700