SDM-300L3 Satellite Modem
Revision 0
Specifications
MN/SDM300L3.IOM
14–29
14.10.12 Receive
Doppler/Plesiochronous Buffer Size
The receive Doppler buffer size can be set by the operator from:
1. Bypass.
2. 32 to 262144 bits, in 16 bit steps for all data rates.
3. Selectable in ms, from 1 to 99 in 1 ms steps, for data rates < 2.6 Mbps.
4. Selectable Frame Format G.704 or None.
14.10.13 Switch
Faults
•
Modulator Fault
Open collector output, 15V maximum, 20 mA maximum
current sink, fault is open circuit
•
Demodulator Fault
Open collector output, 15V maximum, 20 mA maximum
current sink, fault is open circuit
14.11 Decoding
14.11.1 BPSK
Decoding
Using vector analysis of the constellation pattern, BPSK represents one symbol with the
carrier phase either at 0
°
or 180
°
. The characteristics for BPSK are provided in the
following table.
Code Rate
Symbols/Bit
Bits/Hz
1/1 1
2
1/2 2
0.5
5/16 3.2
0.3125
21/44 2.1
0.477
14.11.2 QPSK
Decoding
The demodulator converts transmitted baseband data into a modulated QPSK carrier at the
following parameters:
4.8 kbps to 2.5 Mbps (1/2 rate)
7.2 kbps to 3.75 Mbps (3/4 rate)
8.4 kbps to 4.375 Mbps (7/8 rate)
