Offset Qpsk Decoding (Optional; 8-Psk Decoding - Comtech EF Data SNM-1001L Installation And Operation Manual

SNM-1001L Satellite Modem
Specifications
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 provide the
desired input/output bit rates.
A.11.3

Offset QPSK Decoding (Optional)

The demodulator PCB converts the transmitted baseband data into a modulated Offset
QPSK carrier within the same parameters as QPSK.
The Offset QPSK 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.
A.11.4

8-PSK Decoding

The demodulator 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 Symbols/Bit
1/1 1
1/2 2
3/4 1.5
7/8 1.143
Code Rate Symbols/Bit
1/1 1
1/2 2
3/4 1.333
7/8 1.143
Code Rate Symbol/Bit
2/3 1.5
3/4 1.333
A–27
Bits/Hz
2
1
1.33
1.75
Bits/Hz
2
1
1.5
1.75
Bit/s Hz
2
2.25
Revision 1
MN/SNM1001L.IOM