Standard And Optional Features; Functional Description; Figure 1-2. Cdm-710 Block Diagram; Figure 1-3. Cdm-710 Block Diagram - Comtech EF Data CDM-710 Installation And Operation Manual

CDM-710 Broadcast Satellite Modem
Introduction
The CDM-710 is compact, being 1RU high x 18.65 inches deep, with low power consumption. It
has a front panel Vacuum Fluorescent Display (VFD) and keypad for local configuration and
control, although it can be fully remote-controlled via its RS-485 bus or 10/100 Base-T Ethernet
Interface.
1.1.1

Standard and Optional Features

The CDM-710 operates in DVB-S (QPSK), DVB-DSNG (8-PSK and 16-QAM) and DVB-S2
(QPSK, 8-PSK, 16-APSK, and 32-APSK) modes. The modem is operated from the front panel
using the keypad and display or remote controlled via an RS-232 / RS-485 2/4 Wire bus or
10/100 Base-T Ethernet port located on the base modem.
The modem is available for either 70/140 MHz or L-Band applications. The standard 70/140 MHz
Tx-IF port has a BNC female connector that is programmable for either with 50Ω or 75Ω
impedance operations. Spectral rolloffs of 20, 25, and 35% are available.
1.2

Functional Description

A block diagram of the CDM-710 is shown in Figure 1-2.
The CDM-710 is constructed as a 1RU-high rack-mounting chassis, which can be freestanding if
desired. Handles at the front facilitate removal from and placement into a rack.
The CDM-710 performs several key functions:
•
It accepts incoming data from the terrestrial interface and converts it into appropriate
clock and data signals.
•
The modulator operates on the data to frame and encode it for transmission.
•
Encoded information is mapped for modulation.
•
A modulated carrier is transmitted from the IF interface for use by uplink equipment for
delivery to the satellite.
•
A carrier received from the satellite link is acquired and demodulated to recover symbols
and timing.
•
Error correction and deframing are performed.
•
User data is delivered to the to the data interface.
Transmit (Tx) data is delivered to the data interface where it is converted to clock and data
signals for further processing. Depending upon the type of interface, clock and data are provided
or in other cases the clock is embedded in the data and clock recovery is performed to generate
clock and data signals.
A First-In–First-Out (FIFO) follows the terrestrial interface to facilitate delivery of the data to the
framing card. Data is passed to the Forward Error Correction (FEC) Encoder where the data is
framed and encoded in accordance with either the DVB-S, DVB-DSNG, or DVB-S2 formats.

Figure 1-2. CDM-710 Block Diagram

DVB-S &
DSNG
Viterbi
+RS

Figure 1-3. CDM-710 Block Diagram

1–2
MN/CDM710.IOM
CDM-710
Revision 11