From: chasgra ([email protected])
Date: Wed Nov 01 2000 - 21:03:48 PST
RE: [SI-LIST] : differential impedance calculationsHi Larry - Thanks for your comments.
If you are referring to slides 45 & 46 I think you misunderstand the intent.
Dr Bogatin was, I believe, trying to show comparisons between Ist order
approximations and a field solver. I do not belive any assumptions were
being made. Indeed as I recall he did nake the statement that one should
not always trust approximation BECAUSE of the assumptions.
Charles Grasso
----- Original Message -----
From: Larry Miller
To: Charles Grasso ; Gary Peterson ; si-list
Cc: eric
Sent: Wednesday, November 01, 2000 2:04 PM
Subject: RE: [SI-LIST] : differential impedance calculations
Unfortunately, the piece by Dr Bogatin makes and refers to the very assumptions that Dr Johnson refers to.
All roads lead to the National App Note AN-905.
(I have been battling this same fight myself.)
Larry Miller
-----Original Message-----
From: Charles Grasso [SMTP:[email protected]]
Sent: Wednesday, November 01, 2000 2:23 PM
To: Gary Peterson; si-list
Cc: eric
Subject: Re: [SI-LIST] : differential impedance calculations
Hello - There is an excellent presentation available for download called
"Differential Impedance finally made Simple" authored by Dr Bogatin that
should help answer this question.
Please goto http://www.ewh.ieee.org/rmcemc Click on Last Meeting and
follow the instructions for the presentation download.
Enjoy!!
Charles Grasso
Ansoft Corporartion
p: 303-666-1400
f: 303-666-1499
----- Original Message -----
From: "Gary Peterson" <[email protected]>
To: <[email protected]>
Sent: Wednesday, November 01, 2000 12:50 PM
Subject: [SI-LIST] : differential impedance calculations
>
>
> I seem to recall Dr. Howard Johnson mentioning that impedance calculation
> formulas made assumptions (since closed-form solutions aren't possible).
>
> Can someone comment on assumptions made for the equation for differential
> impedance shown below? Seems to me that as traces get closer together,
the
> single ended impedance would be affected. When I calculate single-point
> values for differential impedance using Hyperlynx LineSim, I do see the
> single-ended impedance change when the spacing between the pair gets
small.
>
> Thanks,
>
> Gary Peterson
>
>
>
> (Embedded image moved to file: pic27894.pcx)
>
>
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