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SDM-300Ls Satellite Modem
Burst Mode Modulator Operation
B.2.17
Transmit Preamble
In burst mode, when RTS transitions from false to true, the modem shall turn on the RF
carrier and generate a burst preamble with the following characteristics:
96 symbols at 19.2 kbps
288 symbols at 57.6 kbps
CW
Channel contents:
*Note: Bit Timing and the Unique Word is BPSK and uncoded.
At the end of the preamble, the modulator shall cause CTS to transition from false to true.
This signals the baseband equipment to begin sending data. The RF carrier shall remain
on until RTS transitions back to false.
B.2.18
Transmit Packet
The minimum length is 48 bps. The maximum length can be infinite. Packet length is
determined by the user.
B.2.19
Transmit Postamble
When RTS transitions back to false, the modulator flushes the Encoder and sends the End
of Message pattern, turns off the RF carrier and resets CTS back to false. The EOM
pattern is shown below.
6 symbols
Flush
*Note: The Unique Word Prime is BPSK and uncoded.
352 symbols
BIT TIMING
CW:
I and Q channels contain all 1's
Bit Timing:
I:
Q:
Unique Word: I:
Q:
Unique Word Prime
1010...
1010...
000 0010 0011 1010 1001 0111 1001 1011
000 0010 0011 1010 1001 0111 1001 1011
31 symbols
Unique Word'
I:
110 1100 1111 0100 1010 1110 0010 0000
Q:
110 1100 1111 0100 1010 1110 0010 0000
B–6
Revision 1
MN/SDM300L3.IOM
31 symbols
UNIQUE WORD
31 symbols
Unique Word'
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