Purpose And Function; Figure 1-2. Satellite Communications System With An Sdm-650B - Comtech EF Data SDM-650B Installation And Operation Manual

Introduction

1.1 Purpose and Function

The modem is a high performance, full-duplex, Bi-Phase Shift Keying/Quadrature Phase
Shift Keying (BPSK/QPSK), digital modulator/demodulator (modem), for Frequency
Division Multiple Access (FDMA) satellite communication systems.
The modem provides an interface between Single Channel Per Carrier (SCPC) fixed-rate
terminal equipment, having a data rate of 19.2 kbit/s to 3.584 Mbit/s.
The modem also provides an interface between IF converter equipment operating in a 50 to
90 MHz band, or 100 to 180 MHz band (Figure 1-2).
DIGITAL
CUSTOMER
INTERFACE
DATA
REMOTE
SERIAL
INTERFACE
FAULT
INDICATORS
SDM-650B
SATELLITE
DATA MODEM

Figure 1-2. Satellite Communications System with an SDM-650B

1–2
ENCODER/
MODULATOR
MICRO- POWER
SUPPLY
COMPUTER
DEMODULATOR/
DECODER
SDM-650B Satellite Modem
TRANSMIT
RF EQUIPMENT
ANTENNA
AC POWER
RECEIVE
RF EQUIPMENT
Rev. 5