IN BRIEF (data for review) ____________________________________________
amplitude modulation (AM)
The amplitude modulation, also known as AM,
is to change, moment by moment,
the amplitude of a signal, said carrier,
according to the value of another signal, said modulating
. the modulated signal
take into account both the amplitude and the frequency of
modulating signal.
Therefore, the carrier signal is a kind of representation
signal that "mask" in
if the modulating signal. It fixes a
m, called
index modulation, which, for this type of modulation
, must always be less than
1 (thus including
ratio should be between 0% and 100%). If
modulation index is greater than 1 in AM, which happens
establish the over-modulation
that would go to "load" further
carrier signal, so that at
demodu-lation, the modulating signal is no longer recognizable.
A type of modulation that can
save power is the DSB, which is characterized by
carrier suppression.
This type of modulation
saves power without affecting the transmission of
information, which is contained in the sidebands.
The power required to transmit the signal modulating
, in fact, is about a quarter of that needed in AM
with transmission carrier.
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