Comtech EF Data DMD2401/DMD2401L - Manual (Page 16)

DMD2401/DMD2401L/DMD2401 IBS/IDR Satellite Modem Introduction
TM065 - Rev. 3.3 1-1
Section 1 – Introduction
1.0 Description
The Radyne Corporation DMD2401 and DMD2401L Satellite Modems (Figure 1-1) are
microprocessor-controlled Binary Phase Shift Keyed (BPSK), Quadrature Phase Shift Keyed
(QPSK), Offset Quadrature Phase Shift Keyed (OQPSK), or Trellis Coded 8 Phase Shift Keyed
(8PSK) Modulators/Demodulators. They are used as part of the transmitting and receiving ground
equipment in a satellite communications system. The modem is designed for service in an SCPC
system where two modems are set for continuous operation with each other.
Note: Unless specified, DMD2401 denotes both the DMD2401 and DMD2401L units.
This versatile equipment package combines unsurpassed performance with numerous user-
friendly front panel programmable functions. The DMD2401 provides selectable functions for
Intelsat IBS/IDR, as well as closed networks. All of the configuration, monitor, and control
functions are available at the front panel. Operating parameters such as variable data rates, FEC
code rate, IF frequencies and IBS/IDR framing can be readily set and reconfigured from the front
panel by earth station operations personnel. Additionally, all functions can be accessed with a
terminal or personal computer via a serial link for complete remote monitor and control capability.
The DMD2401 operates at all standard IBS and IDR data rates up to 4.375 Mbps. Selection of
any data rate in closed network operation is provided over the range of 9.6 Kbps to 4.375 Mbps in
1 bps steps. The maximum symbol rate is 2.5 Msps, regardless of modulation type, FEC, code
rate or framing type.
The DMD2401 is designed to perform as both ends of a satellite Single Channel Per Carrier
(SCPC) link or as the VSAT remote site modem in a TDMA hub system in mesh or star topology
networks. The Modulator and Demodulator operate independently using BPSK, QPSK, OQPSK,
or 8PSK modulation in either SCPC or VSAT Modes.
The DMD2401 is also the ideal VSAT modem for use in a Point-to-Point Frame Relay Hybrid
Network. Other applications include FDMA, telephony, video conferencing, long-distance
learning, paging and newsgathering.
Refer to Table 1-1 for selection of any data rate that is provided over the following ranges:
Table 1-1. Data Rates
FEC 1/2 2/3 3/4 7/8
BPSK 4800 bps –
1250 Kbps
N/A 7200 bps –
1875 Kbps
8400 bps –
2187.5 Kbps
QPSK 9600 bps –
2500 Kbps
N/A 14400 bps –
3750 Kbps
16800 bps –
4375 Kbps
OQPSK 9600 bps –
2500 Kbps
N/A 14400 bps –
3750 Kbps
16800 bps –
4375 Kbps
8PSK N/A Optional N/A N/A
The DMD2401 is programmable from the front panel. The program menu was specifically
designed for ease of use to quickly put the modem online and for any network changes. The
modem also can be monitored and controlled through the RS-485 or RS-232 serial control
channel.