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Variation of QAM
o Variations of QAM are numerous
o Any measurable amount changes in
amplitude can be combined with any measurable
no.
of changes in Phase
4
QAM & 8 QAM (Figure))_
o In both case no. of amplitude shifts is
more than the no. of phase shifts
o Because
amplitude changes are
susceptible to Noise
, number of
phase
shifts
used by QAM is always larger than the amplitude shifts
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Bandwidth for QAM
o BW required for QAM is the same as in the
case of
ASK
and PSK
o QAM has the same advantages as PSK over
ASK
o Bit Baud Comparison
Bit
Baud Comparison
Consult
book section 5.3
Example
5.11
A
constellation diagram consists of eight equally spaced points on a circle. If
bit rate is
4800
bps, what is the Baud Rate?
Solution:
Constellation
indicates 8 PSK with the points 45 degree apart
Baud
Rate= 4800 / 3 = 1600 baud
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