User's Manual Part 1

3EM21522AAAA Functiona
l
Description
Issue 1, March 2008 DTR-0200-SA-SIRIUS
2-9
2.3.1.1 L-Band (VSAT) Receiver
The VSAT L-Band receiver connector panel is shown in Figure 2-4.
The receiver module is located on the SPU sub-assembly.
The module receives the DVB-S/S2 signal data stream (which carries the SIRIUS
proprietary CDDS) from the L-band LNB module located on the Ku-band VSAT
antenna.
The receiver processes the down-converted L-band signal by DVB-S/S2 transport
stream removal and data recovery
.
The final receiver output is a stream of CDDS encapsulated into pseudo MPEG TS
pac
kets.
Figure 2 - 4 VSAT (L-Band) Receiver Panel
2.3.1.2 Modulator
The modulator panel is shown in Figure 2 - 5 .
The modulator, located on the SPU sub-assembly, converts the digital coded stream
to an IF.
It receives Sirius CDDS stream input data from the L-band receiver in the form of
MPEG
TS packets transferred by DVB-ASI.
The modulator also receives reference system clock signals in the form of 10MHz and
1PPs from the GPS distribution amplifiers
. These clock signals enter the modulator
at J17A and J17B and synchronize the modulator clock and, in turn, the modulator
output.
COFDM converts the MPEG TS frames to an IF in the form of I and Q signals with a
center frequency of 76.25 MHz ready for up conversion.
The modulator contains a DB-9 serial port wired as a DTE device and requires a null
modem cable to communicate with the serial port on a PC
.