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SDM-300L3 Satellite Modem
Introduction
1.6.6
OQPSK Encoding
The modulator PCB converts the transmitted baseband data into a modulated OQPSK
carrier within the same parameters as QPSK.
The OQPSK modulation is mainly different from QPSK by offsetting the I and Q channel
modulation signals. This offset prevents the RF envelope from going through zero. Under
certain conditions, this may allow less back-off in the High Power Amplifier (HPA)
system. The 1/1, 1/2, 3/4, and 7/8 rates encoded at the convolutional encoder provide the
desired input/output bit rates.
1.6.7
8-PSK Encoding
The modulator converts transmitted baseband data into modulated 8-PSK carrier at the
following parameters:
•
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.
Code Rate
1/1
1/2
3/4
7/8
64 kbps to 5.000 Mbps (2/3 rate)
Code Rate
2/3
Symbols/Bit
Bits/Hz
1
2
2
1
1.333
1.5
1.143
1.75
Symbol/Bit
Bit/s Hz
1.5
2
1–9
Revision 1
MN/SDM300L3.IOM
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