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SDM-300A Satellite Modem
Decoder
A.1.4.7
Sequential Decoder
The sequential decoder is used in closed network applications, typically in Frequency
Division Multiple Access (FDMA) satellite communications systems. The sequential
decoder is a FAST option.
Refer to Figure A-8 for a block diagram of the sequential decoder.
MICRO-
MICROCOMPUTER
COMPUTER
INTERFACE
BUS
I CHANNEL
COSTAS
PROCESSOR
Q CHANNEL
VCXO
SW EEP
CLOCK
RECOVERY
Rev. 4
SYNDROME SHIFT
REGISTER A
PARITY
SYNDROME INPUT
GENERATOR
GENERATOR
SYNDROME SHIFT
AMBIGUITY
RESOLVER
REGISTER B
INPUT
BUFFER
ADDRESS
GENERATOR
TIMING AND
CONTROL
Figure A-8. Sequential Decoder Block Diagram
V.35
DESCRAMBLER
OUTPUT
DIFFERENTIAL
BUFFER
DECODER
CHANNEL BER
DETECTOR
LOCK
DETECT
PROCESS
CLOCK
Options
RECEIVE
DATA
RECEIVE
CLOCK
RCVR
DDS
IF
AGC
CONTROL
A–41
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