[ibis-macro] Re: Question about "impulse response"

  • From: Mike Steinberger <msteinb@xxxxxxxxxx>
  • To: ibis-macro@xxxxxxxxxxxxx
  • Date: Mon, 6 Nov 2017 11:53:43 -0600


I responded to your e-mail will a clear and complete interpretation of your example- an interpretation, by the way, which concluded that you were off by a factor of two. I never did get any response to that e-mail, so maybe it somehow didn't make it into your in-box.

Do I need to resend that e-mail?

Mike S.

On 11/6/2017 11:41 AM, Muranyi, Arpad wrote:


I think I gave all that information in my illustration, which is now on

the bottom of this email.  Please let me know if that is not clear and

I will try another way…




*From:*ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] *On Behalf Of *Mike Steinberger
*Sent:* Monday, November 6, 2017 11:31 AM
*To:* ibis-macro@xxxxxxxxxxxxx
*Subject:* [ibis-macro] Re: Question about "impulse response"


Is the 800mV swing a single ended voltage swing or a differential voltage swing? The input signal to the receiver is a differential voltage. If we confuse single ended with differential, we'll be mixing apples and oranges, and end up with a dog's breakfast.

I cannot agree to Todd's interpretation until I get your answer to this question.

Mike Steinberger

On 11/6/2017 11:11 AM, Muranyi, Arpad wrote:


    Thanks for that clarification.  Yes this is with the assumption that

    the IR is derived from a step response, but all other methods

    would need to provide equivalent results…

    Would everyone on this email list agree with Todd’s interpretation?




    *From:*Todd Westerhoff [mailto:twesterh@xxxxxxxxxx]
    *Sent:* Monday, November 6, 2017 10:33 AM
    *To:* Muranyi, Arpad <Arpad_Muranyi@xxxxxxxxxx>
    <mailto:Arpad_Muranyi@xxxxxxxxxx>; ibis-macro@xxxxxxxxxxxxx
    *Subject:* RE: [ibis-macro] Re: Question about "impulse response"


    My interpretation is that the channel impulse response passed to
    Tx_Init will be the result of differentiating the 800 mV
    differential step response, as you say.

    That, of course, is assuming that the impulse response is derived
    from a step response and not through some other method …


    *Todd Westerhoff*

    VP, Semiconductor Relations

    Signal Integrity Software Inc. • www.sisoft.com

    6 Clock Tower Place • Suite 250 • Maynard, MA 01754

    (978) 461-0449 <978-461-0449> x124  • twesterh@xxxxxxxxxx

    *“*I want to live like that”

                                                 -Sidewalk Prophets

    [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] *On Behalf Of *Muranyi, Arpad
    *Sent:* Thursday, November 2, 2017 2:27 PM
    *To:* ibis-macro@xxxxxxxxxxxxx <mailto:ibis-macro@xxxxxxxxxxxxx>
    *Subject:* [ibis-macro] Re: Question about "impulse response"


    I am trying to apply what you are saying to IBIS-AMI.  Let’s use
    an example in which

    the differential Tx buffer has a 400 mV voltage swing on each of
    its outputs, and as a

    result, the difference step waveform at the Rx goes from -400 mV
    to +400 mV (i.e.

    the amplitude of the step waveform is 800 mV).  The simulator will
    differentiate this

    step waveform and pass it into the AMI Tx Init function as the
    impulse response of

    the channel (or convolve with the output of the Tx GetWave
    function for the time

    domain AMI simulation).  Is this the correct interpretation of
    “impulse response” in

    the IBIS-AMI specification?  Or should the 800 mV difference step
    waveform be

    divided by 2 first before differentiating it to become the
    “impulse response” for the

    purposes if AMI simulations?




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