Re: [SI-LIST] : MECL System Design Handbook

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From: Chris Padilla (cpad@cisco.com)
Date: Thu May 10 2001 - 09:45:44 PDT


Lee,

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.

Thanks----->Chris

>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
>false
>data.
>
>Lee

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