[SI-LIST] Re: DC-blocking transmission-line
- From: "Grasso, Charles" <Charles.Grasso@xxxxxxxxxxxx>
- To: <tfox@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Mon, 2 Jul 2007 16:43:35 -0600
Terry - A quick check shows that your results were derived using a
microstrip cross section with no mask coating. Is that correct?=20
Best Regards
Charles Grasso
Compliance Engineer
Echostar Communications Corp.
Tel: 303-706-5467
Fax: 303-799-6222
Cell: 303-204-2974
Pager/Short Message: 3032042974@xxxxxxxxx
Email: charles.grasso@xxxxxxxxxxxx
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Terry Fox
Sent: Monday, July 02, 2007 4:17 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: DC-blocking transmission-line
Aubrey, Ron,
I always appreciate learning something through the experience of others=20
rather than having to get it the hard way.
I suspect there is a certain amount of conflict in our terminology.
I placed a short explanation about what I was talking about on=20
http://www.siemc.com/SI_List.htm
The link has a schematic and two simulation examples. One example is
very=20
close trace to trace spacing, the other has very wide trace to trace=20
spacing. In both cases the traces are 20 inches long using a PCI
Express=20
driver.
The difference between the two is about 10% in eye opening.
I am happy to do more simulations to illustrate your points, I just want
a=20
common picture from which we can all work.
TFox
At 12:22 PM 6/28/2007, Aubrey_Sparkman@xxxxxxxx wrote:
>I don't believe in public stoning....
>
>What you have said is pretty much true for the special case where the
>two 50 Ohm traces are far enough appart to have negligible coupling.
>Take a look at cases where there is significant coupling. For
instance,
>make a 100 Ohm diff pair from two 60 Ohm traces. Let me know...
>
>
>Aubrey Sparkman
>Enterprise Engineering Signal Integrity Team
>Dell, Inc.
>Aubrey_Sparkman@xxxxxxxx
>(512) 723-3592
>
>The Greatest Pleasure in Life is Doing what People say can't be done...
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
>On Behalf Of Terry Fox
>Sent: Thursday, June 28, 2007 12:29 PM
>To: gkorony@xxxxxxxxx; Si-List
>Subject: [SI-LIST] Re: DC-blocking transmission-line
>
>At risk of being stoned...the "differential impedance" has very little
>to do with anything.
>
>The key issues is the impedance of the individual lines to their
>reference.
>
>The number "differential impedance" comes from 2 X Z0 which is the
>characteristic impedance of each of the individual lines.
>
>If these lines are balanced mirror images, the current through each of
>the two Z0 50 ohm resistors cancels and there is no net current out the
>reference...hence you can use a single 100ohm resistor rather than two
>50 ohm resistors.
>
>The out fall of this is that everyone thinks differential imp[edance is
>some magical thing.
>
>In my experience it is not.
>
>He has touched the holy thing...let us now begin the stoning.
>
>TFox
>
>At 07:59 AM 6/28/2007, George Korony wrote:
>
> >Content-Type: multipart/alternative;
> > boundary=3D"----=3D_NextPart_002_0008_01C7B973.5B78CED0"
> >
> >------=3D_NextPart_002_0008_01C7B973.5B78CED0
> >Content-Type: text/plain;
> > charset=3D"iso-8859-1"
> >Content-Transfer-Encoding: 7bit
> >
> >BlankHi All,
> >I am not a board designer, but I do design parts that other people
put
> >on boards. We are working on a new (patent protected) concept: the "
> >DC-blocking transmission-line".
> >Basically the idea is to build a pair of capacitors that can be
> >intercalated on the differential signal traces, having a controlled
> >characteristic impedance between the two capacitors, the obvious
scope
> >is to reduce the reflections that may show up due the DC-blocking
>capacitors.
> >One request, we have, is that the characteristic impedance between
the
> >two capacitors (treated as a simple transmission line) should be 100
>Ohm.
> >Of course things are not so simple; and my question is: does anyone
> >have a different approach to this problem?
> >Thanks for any suggestion, George.
> >
> >
> >
> >
> >
> >------=3D_NextPart_002_0008_01C7B973.5B78CED0
> >Content-Type: text/html;
> > charset=3D"iso-8859-1"
> >Content-Transfer-Encoding: quoted-printable
> >
> ><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> Hi
All,
> >I am not a board designer, but I =3D do design=3D20 parts that other
people
>
> >put on boards. We are working on =3D a new =3D20 (patent protected)
>concept:
> >the " DC-blocking =3D transmission-line".
> >Basically the idea is to build a =3D pair of=3D20 capacitors that can =
be
> >intercalated on the differential signal =3D traces,=3D20 having a
> >controlled characteristic impedance between the two capacitors, =3D
> >the=3D20 obvious scope is to reduce the reflections that may show up
due
> >the =3D DC-blocking capacitors.
> >One request, we have, is that the=3D20 characteristic impedance =
between
> >the two capacitors (treated as a simple =3D transmission line) should
be
>100 Ohm.
> >Of course things are not so =3D simple; and my=3D20 question is: does
> >anyone have a different approach to this =3D problem?
> >Thanks for any suggestion,=3D20 George.
> >
> >
> >
> >
> >------=3D_NextPart_002_0008_01C7B973.5B78CED0--
> >
> >
> >-- Binary/unsupported file stripped by Ecartis --
> >-- Type: image/gif
> >-- File: Blank Bkgrd.gif
> >
> >
> >
> >-- Binary/unsupported file stripped by Ecartis --
> >-- Type: text/x-vcard
> >-- File: George Korony.vcf
> >
> >
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