[ibis-macro] Re: On impulse and step responses.
- From: "Todd Westerhoff" <twesterh@xxxxxxxxxx>
- To: <ibis-macro@xxxxxxxxxxxxx>
- Date: Thu, 27 Jun 2013 11:02:50 -0400 (EDT)
Dave,
I think this issue has been settled - the units of the impulse response
matrix are volts/sec. This is how the existing EDA tools and models
operate.
The resulting action is to draft a BIRD that updates the description of
the impulse response matrix on pages 163-165 to make it clear that the
units are volts/sec. Can you take that one?
Todd.
Todd Westerhoff
VP, Software Products
Signal Integrity Software Inc. . www.sisoft.com
6 Clock Tower Place . Suite 250 . Maynard, MA 01754
(978) 461-0449 x24 . twesterh@xxxxxxxxxx
"I want to live like that"
-Sidewalk Prophets
From: ibis-macro-bounce@xxxxxxxxxxxxx
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Mike Steinberger
Sent: Thursday, June 27, 2013 10:54 AM
To: ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Re: On impulse and step responses.
volt/sec at SiSoft
On 06/26/2013 08:24 PM, Kumar Keshavan wrote:
volt/sec in cadence
________________________________________
From: ibis-macro-bounce@xxxxxxxxxxxxx [ibis-macro-bounce@xxxxxxxxxxxxx] On
Behalf Of fangyi_rao@xxxxxxxxxxx [fangyi_rao@xxxxxxxxxxx]
Sent: Wednesday, June 26, 2013 9:17 PM
To: Arpad_Muranyi@xxxxxxxxxx; ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Re: On impulse and step responses.
Volt/sec in ADS too.
Fangyi
From: ibis-macro-bounce@xxxxxxxxxxxxx
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Muranyi, Arpad
Sent: Wednesday, June 26, 2013 3:43 PM
To: ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Re: On impulse and step responses.
As far as we are concerned, we do the equivalent of
the time derivative of a step function, i.e. the
unit of the impulse response is in volts/seconds.
Arpad
=====================================================
From: ibis-macro-bounce@xxxxxxxxxxxxx
<mailto:ibis-macro-bounce@xxxxxxxxxxxxx>
<mailto:ibis-macro-bounce@xxxxxxxxxxxxx>
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of David Banas
Sent: Wednesday, June 26, 2013 5:27 PM
To: Todd Westerhoff
Cc: ibis-macro@xxxxxxxxxxxxx <mailto:ibis-macro@xxxxxxxxxxxxx>
<mailto:ibis-macro@xxxxxxxxxxxxx>
Subject: [ibis-macro] Re: On impulse and step responses.
Almost; I'm not sure about #3. It seems some EDA tools are assuming that
the proper units are "Volts/sec.", which is not how I read the spec., as
per my previous response to you. Perhaps, we could get all the EDA tool
vendors to comment?
-db
From: Todd Westerhoff [mailto:twesterh@xxxxxxxxxx]
Sent: Wednesday, June 26, 2013 1:37 PM
To: David Banas
Cc: ibis-macro@xxxxxxxxxxxxx <mailto:ibis-macro@xxxxxxxxxxxxx>
<mailto:ibis-macro@xxxxxxxxxxxxx>
Subject: RE: On impulse and step responses.
Dave,
Thanks for your response.
From a specification standpoint, it seems to me that you're saying the
following:
1. The language in the current spec describing the impulse response
matrix is imprecise and should be improved
2. As we're dealing with a discrete time application, we should
spell that our more precisely when describing the impulse response
3. Given (1) and (2), the impulse responses currently being
generated by EDA tools and the AMI models that use them are OK as-is and
do not need to be changed.
Did I get that right?
Todd.
Todd Westerhoff
VP, Software Products
Signal Integrity Software Inc. . www.sisoft.com <http://www.sisoft.com>
<http://www.sisoft.com>
6 Clock Tower Place . Suite 250 . Maynard, MA 01754
(978) 461-0449 x24 . twesterh@xxxxxxxxxx <mailto:twesterh@xxxxxxxxxx>
<mailto:twesterh@xxxxxxxxxx>
"I want to live like that"
-Sidewalk Prophets
From: David Banas [mailto:DBanas@xxxxxxxxxx]
Sent: Wednesday, June 26, 2013 1:07 PM
To: Todd Westerhoff
Cc: ibis-macro@xxxxxxxxxxxxx <mailto:ibis-macro@xxxxxxxxxxxxx>
<mailto:ibis-macro@xxxxxxxxxxxxx>
Subject: RE: On impulse and step responses.
Hi Todd,
There are two things being discussed, which is probably adding to the
confusion.
Firstly, I'm challenging Mike's belief that the discrete time equivalent
to the Dirac delta is the sequence, {<sample_rate>, 0, 0, .}. I believe
the discrete time equivalent to the Dirac delta is the sequence, {1, 0, 0,
.}. I think this one has probably been exhausted, unfortunately without
resolution.
Secondly, the current spec. fails to name the units, which are to be
assumed for the values passed into Init(), via the impulse_matrix
parameter. This is the issue, which is less academic, more practical, and
more worthy of the committee's time. Here is the current relevant
language, excerpted from IBIS v5.1:
"impulse_matrix" points to a memory location where the collection of
channel voltage impulse responses, . The algorithmic model is expected to
modify the impulse responses in place by applying a filtering behavior,
for example, an equalization function, if modeled in the AMI_Init
function. .
(Note that my omissions of any original text are indicated by ellipses,
and any emphasis is entirely mine.)
Now, the language "impulse response" is vague in signal processing
parlance, as it can refer to either:
1. The continuous time "impulse response function", or
2. The discrete time "unit pulse response sequence",
both of which are more precise concepts.
In deciding which of the two interpretations, above, to accept, one notes
the use of the language, "voltage" (i.e. - NOT "volts/sec."), as a
qualifying preface to the term, "impulse response." Therefore, one could
defensibly argue that `2' should be assumed, since the continuous time
impulse response function must have units of "Volts/sec.", as has been
pointed out now numerous times in this discussion.
Further confidence in choice '2' is gained, by noting that ours is a
necessarily discrete time application. (It takes place entirely within the
state space of a digital computer, and the interface between the model and
the rest of the system is a discrete sequence of numbers.)
Finally, the language, "in place by applying a filtering behavior,"
suggests that the model should expect to be receiving values with units
most natural to direct digital filter application to the unmodified input,
which would be "Volts".
-db
From: Todd Westerhoff [mailto:twesterh@xxxxxxxxxx]
Sent: Wednesday, June 26, 2013 7:39 AM
To: David Banas
Cc: ibis-macro@xxxxxxxxxxxxx <mailto:ibis-macro@xxxxxxxxxxxxx>
<mailto:ibis-macro@xxxxxxxxxxxxx>
Subject: On impulse and step responses.
Dave,
Can I ask you to confirm your initial question on this subject? I want to
make sure I understand what we're saying before we get too deep into the
math.
It seems to me that you've called into question the mathematics behind
impulse responses being created for current IBIS-AMI models, and therefore
how IBIS-AMI models must be written to process those impulse responses.
If there is indeed a problem with the math, it follows that the current
standard would need to be either updated or extended, depending on how the
details play out.
Is that what you're saying?
Todd.
Todd Westerhoff
VP, Software Products
Signal Integrity Software Inc. . www.sisoft.com <http://www.sisoft.com>
<http://www.sisoft.com>
6 Clock Tower Place . Suite 250 . Maynard, MA 01754
(978) 461-0449 x24 . twesterh@xxxxxxxxxx <mailto:twesterh@xxxxxxxxxx>
<mailto:twesterh@xxxxxxxxxx>
"I want to live like that"
-Sidewalk Prophets
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