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

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From: David Instone ([email protected])
Date: Fri May 11 2001 - 08:32:38 PDT

  Thanks, yes, I know allegro can do radiused corners, use it all the
time. What I was referring too was a sharp 90 on the inside of the bend
and the outside of the bend cut off at 45 deg. Means you can't plot
that trace all in one go.

Don't know about whether its necessary at gbaud frequencies but our PCB
guys have got so skilled at radii and curves they can layout edge
coupled differential traces with no problem at all.


[email protected] wrote:
> Hi all,
> David, allegro can do radius'd traces relatively easy. I've had the
> opportunity to do them once or twice, and didn't have a problem. The
> problem I do have with any cad tool is to do "chamfer'd" corners. But
> then, at what speed do I need them? Answer me that and I might buy your
> property in the everglades. :) The times I've done the radius'd corners
> was on analog boards where the engineer was incredibly finicky with the
> copper geometries, and I was sure not to let many people know how easy
> it was to do. Again, what speeds is this necessary? (Got more property
> in the everglades?) I've worked on boards (layout) running at 10Ghz and
> they still were doing 45 degree geometries. The boards running at 40Ghz
> had more problems than just copper geometries.
> Best of luck out there.
> Mitch
> (No, I'm not from Florida :)
> ---------Included Message----------
> > From: "David Instone" <[email protected]>
> > Subject: Re: [SI-LIST] : MECL System Design Handbook
> >
> > Scott,
> > What CAD tools do you have in mind? As far as I know the
> > Cadence/Allegro PCB layout software for one does not, unless of
> course
> > there is a little known command to make it do so. Then of course
> you
> > are dependent on the layout to gerber conversion. Remember most
> lines
> (snip)
> > Scott McMorrow wrote:
> (snip)
> > > a little extra CAD effort. Radiused bends can be used, but
> they
> > > are extremely difficult to perform in most CAD systems. They
> should
> > > be avoided.
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Dave Instone. Compliance Engineer Storage Systems Development, MP24/22 Xyratex, Langstone Rd., Havant, Hampshire, P09 1SA, UK. Tel: +44 (0)23-92-496862 (direct line) Fax: +44 (0)23-92-496014 Tel: +44 (0)23-92-496000

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