[ibis-macro] Re: "AMI Impulse Response"
- From: "Muranyi, Arpad" <Arpad_Muranyi@xxxxxxxxxx>
- To: "ibis-macro@xxxxxxxxxxxxx" <ibis-macro@xxxxxxxxxxxxx>
- Date: Mon, 3 Jun 2013 19:43:40 +0000
Mike,
Regarding “the data signal driving the transmitter has unity amplitude”, this
is not
entirely correct. Considering slide 4 in this presentation:
http://www.vhdl.org/pub/ibis/macromodel_wip/archive/20130108/arpadmuranyi/Analog%20Modeling%20Discussion/AnalogModelingDiscussion.pdf
the “input” to the [Model] in IBIS is a digital signal or an
“event” which acts as a selector between the pullup or pulldown
I-V curves of the transmitter. A digital signal has no amplitude.
The amplitude of the signal at the pad of the [Model] depends on
the reference voltages seen at the supply terminals, the impedance
of the buffer and the impedance of the load.
While I agree that this concept does include the so-called “gain
or loss” effects of the transmitter, the input or stimulus is
really not a unit step.
The difference I see between what is shown on slide 4 and the
proposed S-parameter buffer modeling method (shown on slides 12
and 15 in a slightly different context) is that in the latter
case, the stimulus is an analog signal and that the amplitude
on the pad of the transmitter is determined by the amplitude of
this stimulus instead of the voltages between the power supply
reference terminals (plus the impedance relationship between the
buffer and the load). In this configuration we do have an input
to output relationship and the question of step vs. unit step
becomes important.
I will let our mathematically inclined experts make the necessary
conclusions from this to figure out what the proper definitions
of impulse response could or should be for IBIS-AMI, but I don’t
see how legacy IBIS [Model]s could help us in defining these
terms.
Thanks,
Arpad
===================================================================
From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx]
On Behalf Of Mike Steinberger
Sent: Monday, June 03, 2013 1:01 PM
To: ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Re: "AMI Impulse Response"
Greg, Walter, Vladimir-
I understand that someone in the last IBIS-ATM meeting pointed out (and I
agree) that this entire concern can be resolved by observing that we've always
assumed (perhaps implicitly) that the data signal driving the transmitter has
unity amplitude. Therefore the impulse response presented to downstream models
must include the gain/loss of the transmitter, and truly is an impulse response
in the commonly used, rigorous mathematical sense. Given the unity amplitude
assumption, the associated equations are rigorously defined and straightforward.
We don't need any new concepts or new terminology here. It might, however, be a
good idea to add an explicit statement of the unity amplitude assumption to the
IBIS standard so that we don't have to have this conversation again in the
future.
Thanks.
Mike Steinberger
On 06/03/2013 09:11 AM, Gregory R Edlund wrote:
Walter,
How would you define the other two terms?
AMI Impulse Response : Unit Impulse Response scaled by non-unit voltage swing
Unit Impulse Response : ??
Impulse Response : ??
Greg Edlund
Senior Engineer
Signal Integrity and System Timing
IBM Systems & Technology Group
3605 Hwy. 52 N Bldg 050-3
Rochester, MN 55901
[Inactive hide details for "Walter Katz" ---06/01/2013
04:32:22 PM---All,]"Walter Katz" ---06/01/2013 04:32:22 PM---All,
From: "Walter Katz" <wkatz@xxxxxxxxxx><mailto:wkatz@xxxxxxxxxx>
To: "IBIS-ATM" <ibis-macro@xxxxxxxxxxxxx><mailto:ibis-macro@xxxxxxxxxxxxx>
Date: 06/01/2013 04:32 PM
Subject: [ibis-macro] "AMI Impulse Response"
Sent by: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx>
________________________________
All,
We will be going around in linguistic circles unless we careful define how we
should be using Step Response and Impulse Response. First we can no longer call
the input to Tx AMI_Init an “Impulse Response”. We need to start calling this
an “AMI Impulse Response” understanding that the “AMI Impulse Response” is
the “Unit Impulse Response” scaled by a non-Unit voltage swing. In BIRD 158 we
should in addition only reference the “AMI Step Response”. Thus eliminating any
confusion between “AMI Step Response” and “Unit Step Response” and “Step
Response”, and between “AMI Impulse Response” and “Unit Impulse Response” and
“Impulse Response”.
Walter
Walter Katz
wkatz@xxxxxxxxxx<mailto:wkatz@xxxxxxxxxx>
Phone 303.449-2308
Mobile 303.335-6156
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