Table of Contents
Advertisement
SDM-300L3 Satellite Modem
Introduction
•
•
Note: The code rate determines the number of symbols per bit.
1.6.4
BPSK Encoding
The modulator converts transmitted baseband data into a modulated BPSK carrier at
2.4 kbps to 1.25 Mbps (1/2 rate). Using vector analysis of the constellation pattern, BPSK
represents one symbol with the carrier phase either at 0° or 180°. The 1/2 rate encoding at
the convolutional encoder provides two symbols output for every bit input.
Uncoded (1/1 rate) BPSK operation also is allowed from 4.8 kbps to 2.5 Mbps.
1.6.5
QPSK Encoding
The modulator converts transmitted baseband data into a modulated QPSK carrier at the
following parameters:
•
•
•
•
Using vector analysis of the constellation pattern, QPSK represents a symbol with the
carrier phase angle at 45°, 135°, 225°, or 315°. The 1/1, 1/2, 3/4, and 7/8 rates encoded at
the convolutional encoder provide the desired input/output bit rates.
QPSK (OQPSK): 4 discrete phase angles represent the 4 possible states of a
symbol.
8-PSK: 8 discrete phase angles represent the 8 possible states of a symbol.
Code Rate
1/2
1/1
4.6 kbps to 5.0 Mbps
4.8 kbps to 2.5 Mbps
7.2 kbps to 3.75 Mbps
8.4 kbps to 4.375 Mbps
Code Rate
1/1
1/2
3/4
7/8
Symbols/Bit
Bits/Hz
2
0.5
1
1
(1/1 rate, uncoded)
(1/2 rate)
(3/4 rate)
(7/8 rate)
Symbols/Bit
Bits/Hz
1
2
2
1
1.33
1.5
1.143
1.75
1–8
Revision 1
MN/SDM300L3.IOM
Advertisement
Table of Contents
