Which description best describes upfade in a multipath environment?
A.
In this situation, multiple signal paths are not sent at exactly the same time. The receiver
receives a positive crest on the primary signal and a negative crest on the secondary signal.
B.
In this situation, the multiple signal paths are distorted and difficult to understand.
C.
In this situation, the multiple signal paths are weaker than they should be because the signals
are out of phase with each other.
D.
In this situation, the signal is stronger than it should be because multiple signal paths are
received twice at exactly the same time, which results in the multiple signals being in-phase.
strong
————————————
If a signal is received twice at exactly the same time, the secondary wave adds its power to the
primary wave, so the receiver gets twice the positive energy (positive crest) at the same instant,
then twice the negative energy (negative crest) at the same instant The result is that both waves
add up to twice the amplitude (energy) of a single wave. and both signals are said to be in phase
(both signals are said to have an angle of 0 degrees). This rare condition is called upfade. If the
second signal negative energy (negative crest) reaches the receiver just when the first signal
positive energy (positive crest) also reaches the receiver. both signals can cancel each other,
resulting in no signal at all (this is the principle used in noise cancellation headsets).
upfade strong
in phase