Comtech EF Data SNM-1010L - Manual (Page 175)

SNM-1010L Data/Control Modem Revision 0
Theory of Operation MN/SNM1010L.OM
6.3.2.4 8PSK Encoding
The modulator converts transmitted baseband data into modulated 8PSK carrier at the
following parameters:
• 64 kbit/s to 5.0 Mbit/s (2/3 rate)
•
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 Symbol/Bit Bit/s Hz
2/3 1.5 2
6.4 Demodulator
The demodulator converts PSK modulated carriers within the 50 to 180 MHz range to a
demodulated baseband data stream. The converted modulation types are BPSK,
QPSK/OQPSK, and 8PSK. The demodulator then performs FEC on the data stream using
Viterbi or Sequential decoding algorithms. A block diagram of the demodulator is shown
in Figure Chapter 6-4.
6–13
Figure Chapter 6-4. Demodulator Block Diagram