Comtech EF Data SNM-1002 - Manual (Page 105)

SNM-1002 LinkSync
 Modem
Revision 2
Theory of Operation MN/SNM1002.OM
4–11
4.4 Demodulator
A block diagram of the demodulator is shown in Figure 4-3.
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 and
QPSK (refer to Section 4.2.3 for a description of modulation types). The demodulator
then performs FEC on the data stream using Viterbi decoding algorithms.
DIGITAL
SIGNAL
PROCESSING
DIGITAL
CLOCK
RECOVERY-
LOOP
SWITCH
REF
VCXO
REF
PLL
OC XO
OPT
HIGH
STABILITY
AGC LPF BPF
LO #2
LOOPBACK
RF INPUT
RF INPUT
50 TO 180 MHz
BPF
A TO D
CONVERTER
LO #1
REFERENCE
VITERBI
DECODER
DOPPLER/
PLESIOCHRONOUS
BUFFER
INTERFACE
EXT REFERENCE
Figure 4-3. Demodulator Block Diagram