
Frequency Domain
233
that is, it is the negative of the rate of change of phase with angular frequency,
which has units of time. Practically τ furnishes the way to determine the delay of
signals through the lter, being the amount of time a signal takes to pass through
the lter. So given the transfer function previously determined
1
1
=
+ω
v
RC
o
we have
222
()
τω =
RC
therefore the group delay varies with the frequency. For the special case of ω =0
we have τ = RC, while τ reduces with frequency. Ideally, we would have that all
frequencies of the input signal should have the same time delay, so to avoid distor-
tions but, as we demonstrated, in ...