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Lecture S6
Muddiest Points
General
Comments
Not
many
cards
today,
probably
because folks were delayed
to
class by
the quiz.
Responses
to MuddiestPartoftheLecture
Cards
(18
cards)
1.
What
is
the physical significance of
convolution?
(1
student)
The convolution
integral
is
a
consequence of
linearity
and
timeinvariance, so
in
a
sense all the physics is
based in
the analysis
that leads
on
to
conclude that
a
system
is LTI
—
everything
else
is a
mathematical
consequence of
that. However, you
can
also
understand
the convolution
integral
as
summing
up
lots
of
delayed
impulse responses, which
is a
result
of the LTI
assumption,
and
representing
u
(
t
)
as a
sum
of delayed
impulses.
2.
So if there is
a “West Coast”
school
of
thought
that
block diagrams
should
be
drawn
right to left, don’t these folks
write text
books?
(1)
Actually, they
do,
though most are graduate texts.
3.
In
the
3rd PRS
question, why can
we assume that
f
(
t
)
∗
g
(
t
)
in
the boxed
region?
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 Fall '05
 MarkDrela
 Digital Signal Processing, LTI system theory, 2 hours, Impulse response

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