Psk Encoding - Comtech EF Data SNM-1001L Installation And Operation Manual

SNM-1001L Satellite Modem
Introduction
1.6.3.3 Offset QPSK Encoding
The modulator 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 at the convolutional encoder
provide the desired input/output bit rates.
1.6.3.4

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, 8PSK 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
1–8
Revision 1
MN/SNM1001L.IOM