RE: [SI-LIST] : TDR Risetime (Was: Plane Splits Inspection)

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From: Michael Khusid (mkhusid@sitaranetworks.com)
Date: Fri Nov 10 2000 - 08:52:53 PST


From what I've seen, most people use build-in TDR mathematical functions to
change the risetimes.
For Tektronix TDRs, it's called filtering, for HP TDRs, it's called "change
risetime".
TDR measures the waveforms at default 35psec, and then uses convolution to
display waveforms "at different risetimes". Mathematically, that would be
equivalent to FT of TDR waveform, then reducing of spectrum to match the
slower risetime, and then IFT.
There are multiple issues with implementation of convolution in TDRs, as
well as correctness of this approach in general.

Mike Khusid
Sitara Networks

> -----Original Message-----
> From: Zabinski, Patrick J. [mailto:zabinski.patrick@mayo.edu]
> Sent: Friday, November 10, 2000 11:24 AM
> To: jeff.w.loyer@intel.com; Zabinski, Patrick J.
> Cc: si-list@silab.eng.sun.com
> Subject: RE: [SI-LIST] : Plane Splits Inspection
>
>
> Jeff,
>
> Picosecond Pulse Labs (http://www.picosecond.com) offers edge
> rate filters. They work great.
>
> Pat
>
>
> >>
> >> "We kept our measurements to TDR and TDT, with 35 psec, 250 psec,
> >> 500 psec, 750 psec, and 1000 psec (1 nsec) edge rates."
> >>
> >>
> >I'm dying to know how you changed your edge rates. Right
> now, I'm using
> >lossy cable to do it, but it's not very adjustable. Anything you can
> share?
> >
> >
> >Jeff Loyer
> >(253) 371-8093
>
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