From: Ritchey Lee (firstname.lastname@example.org)
Date: Tue May 15 2001 - 05:17:24 PDT
Sorry, on the last answer, I asked Chris to share his measurements and
test setup. I should have asked Tom for these.
Dagostino, Tom wrote:
> If you look at the cross section of the trace at the bend it gets
> wider. A wider trace has more C per unit length. More C will look
> like a lower Zo. I've seen dips in impedance TDR'ing right angles.
> Tom Dagostino
> IBIS and Tau Modeling Manager
> Mentor Graphics Corp.
> -----Original Message-----
> From: Chris Padilla [mailto:email@example.com]
> Sent: Thursday, May 10, 2001 9:46 AM
> To: firstname.lastname@example.org
> Subject: Re: [SI-LIST] : MECL System Design Handbook
> It is not a myth, there is "some kind of effect" from right angle
> The real question is, I believe, "Do I care, given the speed and/or
> frequency content of the signals I am dealing with?"
> For most of us right now, on this list, we probably *should not* care
> you point out.
> If one is designing a 50 GHz antenna, then it might make a world of
> Out of curiosity, what kind of rise time were you pushing through that
> right angle bend? 100 ps? I am farily certain that I've seen some
> dips (aka capacitance) through right angle bends but I cannot honestly
> that it was directly attributed to the bend.
> >Any of you who want to know how the myth about right angle bends got
> >started, look
> >at figure 7.17 on page 155. This alleges that right angle bends can
> >seen by a
> >TDR. I've done this measurement dozens of times and coiuld never see
> a right
> >angle bend.
> >A few years ago, I called Mr. Blood the author of the book and asked
> >about the
> >diagram. His reply was that he knew the diagram was flawed, but
> >wasn't time
> >to fix it before the book went to press.
> >As a result, thousands of engineers have spend countless time
> >about right
> >angle bends.
> >When we publish technical information such as this, it is important
> >insure it
> >is accurate.
> >This applies especially to applications notes, whic often contain
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