SLM-3650 Satellite Modem
Revision 3
Theory of Operation
MN/SLM3650.IOM
4–25
4.5.3 Closed
Network
Typically, the closed network operation does not add overhead to the terrestrial data. The
closed network operation is not dictated by a specification. The terrestrial data and clock
are passed through the baseband loopback relay and are translated from the selected
baseband format to TTL. The data is re-synchronized by the clock and the data stream is
then output to the modulator through the interface loopback device.
The receive data from the demodulator/decoder is input to the buffer. User data from the
DEMUX section may be optionally input to the buffer.
The front panel interface provides four clock selections clocking the data out of the
buffer:
•
Internal Clock (SCT)
•
RX Recovered Clock (RXCLK)
•
External Clock (EXT)
•
TX Clock Dejittered (TXCLK)
If either RXCLK, SCT, or EXT is selected and then fails, the interface will automatically
switch to RX Sat CLK as the source. The receive data and selected clock are translated to
the levels of the selected baseband interface and output through the baseband loopback
relay.
4.5.4 Open
Network
The modem is a high-performance, full-duplex, digital-vector modulator/demodulator.
The modem meets the open network requirements of the INTELSAT IESS-308 and -309
specifications for IDR, IBS, and EUTELSAT SMS.
Refer to Appendix A for IBS and IDR information.
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