[ibis-macro] Re: On impulse and step responses.
- From: "Mirmak, Michael" <michael.mirmak@xxxxxxxxx>
- To: "msteinb@xxxxxxxxxx" <msteinb@xxxxxxxxxx>, "ibis-macro@xxxxxxxxxxxxx" <ibis-macro@xxxxxxxxxxxxx>
- Date: Thu, 20 Jun 2013 17:39:41 +0000
For some of us, college was a long time ago.
For some of us (likely an overlapping set), pressing particular buttons to get
a particular model/device/board analysis done in a particular flow, and getting
the work summarized in slides, takes precedence over hitting the books and
getting the theory right. Sad, perhaps, but often a business necessity.
Thanks for your patience.
- MM
From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx]
On Behalf Of Mike Steinberger
Sent: Thursday, June 20, 2013 10:35 AM
To: ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Re: On impulse and step responses.
Greg-
The math is truly still the math, but it also has to be all the math.
If you want to use a narrow pulse of whatever shape, that's fine; however it is
essential that the pulse always has unit area (volts * seconds). Therefore, as
your pulse gets narrower and narrower, its amplitude has to get greater and
greater. In fact, the Dirac delta function has, by definition, unit area, in
that it's defined as the limit of your narrow pulse (with unit area) as the
width of the pulse goes to zero.
In the sampled data World, we don't actually take the width of the pulse to
zero. Rather, we leave it one sample wide, as being the narrowest pulse we can
generate in that domain. The sampled data equivalent of the (continuous time
domain) Dirac delta function therefore has a width of one sample and an
amplitude of one over the sample interval.
People, these are fundamental concepts that each of us should have learned in
college. Do they really require discussion on a public reflector?
Cheers,
Mike Steinberger
On 06/20/2013 11:54 AM, Gregory R Edlund wrote:
The Math is the Math. Do not question it!
Seriously, though. The other way to define an impulse response is the response
of a network to a very narrow triangular or Gaussian stimulus (Dirac delta
function), right? This waveform certainly has unit of Volts. The math must
necessarily be different in these two cases for it to be physically meaningful.
Greg Edlund
Senior Engineer
Signal Integrity and System Timing
IBM Systems & Technology Group
3605 Hwy. 52 N Bldg 050-3
Rochester, MN 55901
Inactivehide details for David Banas ---06/20/2013 09:52:18 AM---Hiall, In our
work, we often take as a priori that the impulDavid Banas ---06/20/2013
09:52:18 AM---Hi all, In our work, we often take as a priori that the impulse
response is the time derivative of t
From: David Banas <DBanas@xxxxxxxxxx><mailto:DBanas@xxxxxxxxxx>
To: "ibis-macro@xxxxxxxxxxxxx"<mailto:ibis-macro@xxxxxxxxxxxxx>
<ibis-macro@xxxxxxxxxxxxx><mailto:ibis-macro@xxxxxxxxxxxxx>
Date: 06/20/2013 09:52 AM
Subject: [ibis-macro] On impulse and step responses.
Sent by: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx>
_____
Hi all,
In our work, we often take as a priori that the impulse response is the time
derivative of the step response. As I puzzle over this further, I realize that
I’m stumped by something very fundamental, which is this:
A quantity, which is the time derivative of some other quantity, cannot have
the same units as that other quantity. And, yet, when we
discuss/measure/simulate either a step response or an impulse response, we
expect to be talking about / measuring / viewing a voltage as a function of
time, in both cases! How can this be?
Thanks,
-db
_____
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