Nera Inmarsat-c, Service Manual

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AP1.3 Channel types and Signal processing
AP1-26
BPSK Modulation
BPSK is a kind of phase modulation using a digital signal. Depending on carrier phase
difference, BPSK is expressed as 0 or 1. Data signal “0” is not phase shifted; data
modulation.
Fig. AP1.3.12 BPSK Modulation
Frame synchronization
Detects a unique word to synchronize to the frame signal.
De-permuting
Demodulated signal is de-permuted and input to the interleave matrix.
De-interleaving
Reassembles the message in the interleave matrix.
Viterbi Decoding
Decodes the viterbi-encoded signal. If any error is found, it is automatically corrected.
The burst error is also corrected by combining with the interleaving.
De-scrambling
Scrambled signal is decoded.
H L L H L
Carrier
Digital signal
BPSK modulated signal
BPSK modulator
Phase
change
by 180°
no phase
change
Phase
change
by 180°
Phase
change
by 180°
signal “1” is phase shifted 180 degrees. DDS of Nera C is for the BPSK