Comtech EF Data DM240XR - Manual (Page 21)

MN-DM240XR– Revision 13 3–1
Chapter 3. Theory of Operation
3.1 Theory of Operation
The advanced hardware/software architecture of the DM240XR allows a single piece of hardware
to be configured for a variety of different applications. Several of these hardware/software
platforms are listed in the next sections. Custom applications are available.
The basic operation of each platform is similar. A digital terrestrial interface supplies the
modulator with a data stream. The data stream is synchronized if the incoming stream is framed.
The data is scrambled, and FEC is added. The data is then convolutionally encoded, punctured,
then constellation mapped. The resulting I&Q Symbols are digitally filtered. The data is then
converted into an analog waveform and is vector modulated onto an RF Carrier produced from
the Transmit IF Synthesizer Circuitry.
Since the baseband processing is completely digital, many different variations of signal
processing can be performed. Therefore, the DM240XR is one of the most flexible digital
modulators available today.
3.2 DVB-S Operation
The DVB-S version of the DM240XR complies with both EN300-421 and EN301-210 ETSI
Specifications.
A block diagram of the signal flow is shown in Figure 3-1 below.