[ibis-macro] Re: On impulse and step responses.
- From: David Banas <DBanas@xxxxxxxxxx>
- To: "twesterh@xxxxxxxxxx" <twesterh@xxxxxxxxxx>, "ibis-macro@xxxxxxxxxxxxx" <ibis-macro@xxxxxxxxxxxxx>
- Date: Thu, 27 Jun 2013 08:08:51 -0700
Yes, I guess it's only fair that I write it up, since I opened this can of
worms. ;-)
I will draft the BIRD.
If there is anyone out there, whom hasn't spoken up and whom sides with me on
this in believing that the language of the current spec. (IBIS v5.1) implies
that "Volts" are actually the correct unit to be assumed for this quantity,
please, speak now or forever hold your peace.
Thanks,
-db
From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx]
On Behalf Of Todd Westerhoff
Sent: Thursday, June 27, 2013 8:03 AM
To: ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Re: On impulse and step responses.
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<http://www.sisoft.com>
6 Clock Tower Place * Suite 250 * Maynard, MA 01754
(978) 461-0449 x24 * twesterh@xxxxxxxxxx<mailto:twesterh@xxxxxxxxxx>
"I want to live like that"
-Sidewalk Prophets
From: ibis-macro-bounce@xxxxxxxxxxxxx<mailto: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<mailto: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<mailto:ibis-macro-bounce@xxxxxxxxxxxxx>
[ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx>] On
Behalf Of fangyi_rao@xxxxxxxxxxx<mailto:fangyi_rao@xxxxxxxxxxx>
[fangyi_rao@xxxxxxxxxxx<mailto:fangyi_rao@xxxxxxxxxxx>]
Sent: Wednesday, June 26, 2013 9:17 PM
To: Arpad_Muranyi@xxxxxxxxxx<mailto:Arpad_Muranyi@xxxxxxxxxx>;
ibis-macro@xxxxxxxxxxxxx<mailto: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>
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Muranyi, Arpad
Sent: Wednesday, June 26, 2013 3:43 PM
To: ibis-macro@xxxxxxxxxxxxx<mailto: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
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[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><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><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><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><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><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><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><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><mailto:twesterh@xxxxxxxxxx>
"I want to live like that"
-Sidewalk Prophets
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