Table of Contents
Advertisement
Introduction
The modulator and demodulator are intended for use in commercial applications for
transmission and reception of digitized video signals. The basic digitized video format
supported is defined by the Moving Pictures Experted Group-2 (MPEG-2) (see ISO/IEC
DIS 13818-1, Coding of moving pictures and associated audio).
The demodulator also has adative equalization capability. A general block diagram for
the demodulator is shown in Figure 1-2.
User
Rx
Interface
IF
Other formats including unframed data are supported by selecting the appropriate data
interface. The demodulator uses a plug-in data interface module installed in the rear of
the chassis. The data interface module provides flexible adaptation to the various
physical and electrical interfaces found in the communications industry. Refer to
Appendix A for a detailed description of the data interface module.
The data rate of the demodulator is programmable from 1.5 to 100 Mbit/s, with
maximum symbol rates up to 37.5 Msys/s depending upon the modulation, code rate, and
data interface. Demodulation formats include QPSK, 8PSK and 16QAM. Operation is
based upon the DVB standard. Refer to Appendix B for detailed remote control
operation.
The demodulator incorporates concatenated error correction coding for improved signal
quality. With concatenated coding, an outer Reed-Solomon Codec is used in tandem with
an inner Viterbi or trellis-type Codec. The Reed-Solomon coding is DVB (based on 204,
188, t=8 type code), while the Viterbi and trellis codes are based upon a constraint length
K = 7 convolutional coding. This combination significantly reduces the required
operating power of the satellite system.
The demodulator is a completely self-contained unit in a standard, one-unit (1U) 19-inch
(48.26 cm) rack-mountable enclosure. It includes a backlit LCD display and a standard
EFData six-button keypad for user control. Prime power is alternating current (AC) input
or optionally direct currect (DC) input. The IF input to the demodulator is
L-Band or 70 or 140 (70/140) MHz IF.
1–2
L-Band Or
Carrier &
70 / 140 MHz
Symbol
Tuner
Recovery
LNB
Voltage
Synthesizer
5611
Figure 1-2. Demodulator Block Diagram
SDM-2020 Satellite Demodulator
Viterbi / Trellis
De-interleaver
Decoder &
RS Decoder
Sync
Descrambler
M&C
Plug-In
Data
User
Interface
Interface
Remote Port
& Faults
Rev. 3
Advertisement
Table of Contents
