Comtech EF Data SDM-300A, Installation And Operation Manual

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Specifications SDM-300A Satellite Modem
C–14 Rev. 4
C.3.3 Descrambling Types
The operator can select one of the following descrambling types:
CCITT V.35 EFData/Comstream compatible. Sequential only
CCITT V.35 Intelsat modified. Viterbi only
Fairchild compatible
2^15-1 Synchronous
IBS, Drop & Insert, ASYNC, and IESS-310
Modified V.35 Closed Network Reed-Solomon
None
C.3.4 Differential Decoder
The differential decoder takes care of one set of ambiguities due the error correction
codes being transparent.
•
On or Off
C.3.5 BPSK Bit Ordering
The decoder has the ability to select whether I is the first bit or Q is the first bit in the
symbol word grouping for compatibility with any system. For standard mode Q is the
first bit.
•
Viterbi (Standard/Non-Standard)
•
Sequential (Standard/Non-Standard)
C.3.6 Decoding
C.3.6.1 BPSK Encoding
The demodulator converts transmitted baseband data into a modified BPSK carrier
2.4 kbit/s to 1.25 Mbit/s (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 two symbols output for every bit input.
Code Rate Symbols/Bit Bits/Hz
1/2 2 0.5