Comtech EF Data SLM-3650 Installation And Operation Manual page 193

SLM-3650 Satellite Modem
Theory of Operation
4.2.3.1 BPSK Encoding
The modulator converts transmitted baseband data into a modulated BPSK carrier at
2.4 kbps to 1.25 Mbps (1/2 rate). Using vector analysis of the constellation pattern, BPSK
represents one symbol with the carrier phase either at 0° or 180°. The 1/2 rate encoding at
the convolutional encoder provides two symbols output for every bit input.
4.2.3.2 QPSK Encoding
The modulator 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)
Using vector analysis of the constellation pattern, QPSK represents a symbol with the
carrier phase angle at 45°, 135°, 225°, or 315°. The 1/2, 3/4, and 7/8 rates encoded at the
convolutional encoder provide the desired input/output bit rates.
4.2.3.3 8-PSK Encoding
The modulator converts transmitted baseband data into modulated 8-PSK carrier at the
following parameters:
•
64 kbps to 5.0 Mbps (2/3 rate)
Using vector analysis of the constellation pattern, 8-PSK represents a symbol with carrier
phase angles at 22.5°, 67.5°, 112.5°, 157.5°, 202.5°, 247.5°, 292.5°, and 337.5°. The 2/3
rate encoding provides the desired input/output bit rates.
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Code Rate Symbols/Bit
1/2 2
Code Rate Symbols/Bit
1/2 2
3/4 1.5
7/8 1.143
Code Rate Symbol/Bit
2/3 1.5
4–13
MN/SLM3650.IOM
Bits/Hz
0.5
Bits/Hz
1
1.33
1.75
Bit/s Hz
2
Revision 3