Transmit Preamble; Transmit Packet; Transmit Postamble - Comtech EF Data SNM-1001L Installation And Operation Manual

SNM-1001L Satellite Modem
Burst Mode Modulator Operation
C.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.
C.2.18

Transmit Packet

The minimum length is 48 bps. The maximum length can be infinite. Packet length is
determined by the user.
C.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.
CW: I and Q channels contain all 1's
Bit Timing: I:
Q:
Unique Word: I:
Q:
Unique Word Prime
352 symbols
BIT TIMING
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
C–6
Revision 1
MN/SNM1001L.OM
31 symbols
UNIQUE WORD
31 symbols
Unique Word'