SLM-3650 Satellite Modem
Revision 3
Theory of Operation
MN/SLM3650.IOM
4–17
implemented digitally. The DDS performs the function of a VCO in an analog
implementation. The recovered data and symbol clocks are then used throughout the
demodulator.
The soft decision mapper converts the digital I and Q data to 3-bit soft decision values.
These values are then fed to the programmable vector rotation circuit, providing
compatibility with spectrum reversal of the I and Q channels.
The output of the vector rotation circuit is then sent to the Viterbi decoder and optional
Sequential decoder. The output is then sent to the optional Reed-Solomon or Overhead
PCB.
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