From: Ritchey Lee ([email protected])
Date: Tue May 15 2001 - 05:14:12 PDT
If there is "some kind of effect" the claimer should be able to show it in a
repeatable way. I have never see any such demonstation. When I ask for one, I get
hand waving much like that in you response.
I used an 18 pSEC edge for my tests. The first harmonic of such an edge is well
above 20 GHz and even then there is no visible effect of the bend.
Is in meaningful t speculate about there might be some effect at some very high
frequency when the context of the hadbook and this discussion is high speed logic
Chris Padilla wrote:
> It is not a myth, there is "some kind of effect" from right angle bends.
> 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 as
> you point out.
> If one is designing a 50 GHz antenna, then it might make a world of difference!
> 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 small
> dips (aka capacitance) through right angle bends but I cannot honestly say
> 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 be
> >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 there
> >wasn't time
> >to fix it before the book went to press.
> >As a result, thousands of engineers have spend countless time worrying
> >about right
> >angle bends.
> >When we publish technical information such as this, it is important to
> >insure it
> >is accurate.
> >This applies especially to applications notes, whic often contain entirely
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