SDM-300L3 Satellite Modem
Revision 0
Specifications
MN/SDM300L3.IOM
14–14
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 provide
the desired input/output bit rates.
Code Rate
Symbols/Bit
Bits/Hz
1/1 1
2
1/2 2
1
3/4 1.5 1.33
7/8 1.143 1.75
14.6.2 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 provide the desired input/output bit rates.
Code Rate
Symbols/Bit
Bits/Hz
1/1 1
2
1/2 2
1
3/4 1.333 1.5
7/8 1.143 1.75
14.6.3 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 rate
encoding provides the desired input/output bit rates.
Code Rate
Symbol/Bit
Bit/s Hz
2/3 1.5 2
3/4 1.333
2.25