[SI-LIST] Re: Right Angle Bends
- From: Mick zhou <mick.zhou@xxxxxxxxx>
- To: Lee Ritchey <leeritchey@xxxxxxxxxxxxx>
- Date: Fri, 15 Jul 2011 16:32:15 -0400
Maybe it is not a simple YES or NO although in most SI work it is NO. We
may want to think about electrical dimensions and what/how they are
connected. I think this is well-documented in papers and books. The problem
is some enginners may misunderstand the conclusions in the way they like. We
like tips/points to remember etc but forget the conditions.
There are measured data showing bends matter in certain configurations. For
example, section 8.16 in Signal Integrity--simplified presents an example.
A serpentine line is another extreme example.
Regards,
On Fri, Jul 15, 2011 at 1:43 PM, Lee Ritchey <leeritchey@xxxxxxxxxxxxx>wrote:
> None of these calculations are substantiated by actual measurements.
>
> There are several published works with actual testing out to 20+ GHz
> measuring signal traces that show there is no detectable effect on signal
> quality.
>
> I have a half dozen test PCBs which have been used to make the same
> measurements and I have published the results as well as shown them to
> 8000+
> students in my public and private classes.
>
> Our industry has a problem with people doing simulations from which
> conclusions are drawn without validating the simulations. Often, as in the
> case of right angle bends, much time and money is spent by designers making
> something go away that is of no consequence.
>
> Simulations without validation can be very dangerous.
>
> Lee Ritchey
>
>
>
> --------------------------------------------------
> From: "Zabinski, Patrick" <zabinski.patrick@xxxxxxxx>
> Sent: Friday, July 15, 2011 9:46 AM
> To: <si-list@xxxxxxxxxxxxx>
> Subject: [SI-LIST] Re: Right Angle Bends
>
> > Here are a few of the earlier references on the topic.
> >
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > TITLE Calculation of Microstrip Bends and Y-Junctions With Arbitrary
> > Angle
> > AUTHOR Reza Mehran
> > SOURCE IEEE Transactions on MTT, MTT-26
> > DATE June, 1978
> > PAGES 400-405
> >
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > TITLE Microstrip - A New Transmission Technique for the Kilomegacycle
> > Range
> > AUTHOR D. D. Grieg & H. F. Engelmann
> > SOURCE Proceedings of the IRE
> > VOLUME 40
> > DATE December, 1952
> > PAGES 1644-1650
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > These offer related info.
> >
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > TITLE Equivalent Circuit Modeling of Interconnects From Time-Domain
> > Measurements
> > AUTHOR Jyh-Ming Jong, Bozidar Janko, and Vijai Tripathi
> > SOURCE IEEE Trans. on CHMT
> > VOLUME 16
> > NUMBER 1
> > DATE February, 1993
> > PAGES 119-126
> >
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > TITLE Equivalent Circuits for Discontinuities in Balanced Transmission
> > Strip Lines
> > AUTHOR Arthur A. Oliner
> > SOURCE IRE Trans Micorwave Theory & Techniques
> > VOLUME MTT-3
> > DATE March, 1955
> > PAGES 134-143
> >
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > TITLE Experimental Determination of the Properties of Microstrip
> > Components
> > AUTHOR Maurice Ardit
> > SOURCE Electrical Communication
> > VOLUME 30
> > DATE December, 1953
> > PAGES 283-293
> >
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > TITLE Time-Domain Characterization of Interconnect Discontinuities in
> > High-Speed Circuits
> > AUTHOR Jyh-Ming Jong and Vijai K. Tripathi
> > SOURCE IEEE Trans on CHMT
> > VOLUME 15
> > NUMBER 4
> > DATE August, 1992
> > PAGES 497-504
> >
> > ~~~~~~~~~~~~<done>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > Enjoy,
> > Pat Zabinski
> > Mayo Clinic
> >
> > -----Original Message-----
> > From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> > On Behalf Of Lee Ritchey
> > Sent: Friday, July 15, 2011 11:33 AM
> > To: si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Re: Right Angle Bends
> >
> > Does anyone know the origin of the myth that right angle bends cause
> > signal integrity problems?
> >
> > I though this myth had died a long time ago, but had a conversation last
> > week with a well known fabricator who was told by a customer that right
> > angle bends were a no no.
> >
> > This was a customer who should know better.
> >
> > Lee Ritchey
> > Speeding Edge
> >
> >
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