[SI-LIST] Re: Preparing S-Parameters for Simulation

Hi,
 

I received some requests for more references about the method we patented. Here 
you go:

1) US Patent Application 20080281893, Serial Number 747007, Series Code 11, 
"Optimization Of Spectrum Extrapolation For Causal Impulse Response Calculation 
Using The Hilbert Transform"

 

2) "The Need for Impulse Response Models and an Accurate Method for Impulse 
Generation from Band-Limited S-Parameters" DesignCon 2008, by Fangyi Rao, Chad 
Morgan, Sanjeev Gupta, and Vuk Borich

 

Best,

-- Colin

http://signal-integrity-tips.com <http://signal-integrity-tips.com/>  

 

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On 
Behalf Of WARWICK,COLIN (A-Americas,ex1)
Sent: Thursday, February 26, 2009 3:46 AM
To: scott@xxxxxxxxxxxxx; BADESHA,AMOLAK (A-SantaClara,ex1)
Cc: shlepnev@xxxxxxxxxxxxx; tim@xxxxxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Preparing S-Parameters for Simulation

 

Hi Scott,

 

 

Here's a 2007 paper about our (patented) technique for getting causal impulse 
responses from S-parameters, including a comparison:

 

 

 

http://eesof.tm.agilent.com/pdf/si_seminar_2007_transient_simulation.pdf

 

 

 

The key thing to bear in mind is that applying an IFFT to S-parameters to try 
to get an impulse response will guarantee the wrong answer: the output of an 
IFFT is by definition a piece of periodic waveform: not a single impulse at 
all, but a truncation (one period of a train of impulses). It's true you can 
use band-aids like windowing to try to minimize the Gibbs phenomenon but this 
doesn't get the heart of the problem, which is this:

 

To get an impulse response in general you'd need the frequency response in the 
complex plane (s = alpha + j*omega) and then do an inverse *Laplace* transform. 
Fortunately, it turns out that don't need all that data because for causal 
systems the Kramers-Kroenig relations:

 

 

 

http://en.wikipedia.org/wiki/Kramers-Kronig_relations

 

 

 

...allow you to reconstruct the response using just the steady state frequency 
response (alpha=0 locus) i.e. the information in the S-parameters file. The 
resulting fit is guaranteed causal.

 

For more info on our implementation please see:

 

http://www.agilent.com/find/signal-integrity 

 

Hope this helps,

 

-- Colin

 

http://signal-integrity-tips.com <http://signal-integrity-tips.com/>  

 

 

 

-----Original Message-----

From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On 
Behalf Of Scott McMorrow

Sent: Wednesday, February 25, 2009 4:08 PM

To: BADESHA,AMOLAK (A-SantaClara,ex1)

Cc: shlepnev@xxxxxxxxxxxxx; tim@xxxxxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx

Subject: [SI-LIST] Re: Preparing S-Parameters for Simulation

 

 

 

Amolak

 

 

 

Is there documentation on how those causality/passivity corrections are 

 

performed?  Any way to compare the before and after results?

 

 

 

regards,

 

 

 

Scott

 

 

 

 

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