[SI-LIST] Re: DC-blocking transmission-line
- From: olaney@xxxxxxxx
- To: tfox@xxxxxxxxx
- Date: Mon, 2 Jul 2007 16:18:03 -0700
Um, "mil" as in one thousandth of an inch, has only one L. The other is
a type of factory.
Small point but it hurts my eyes...
On Mon, 02 Jul 2007 16:09:25 -0700 Terry Fox <tfox@xxxxxxxxx> writes:
> Charles,
>
> The simulation was made with both differential signal traces on the
> top
> layer of the PCB.
>
> There was 0.5 oz solder mask (Er of 3.3) on top of a
> 0.5 oz copper trace that was 5 mills wide.
> 3 mills of dielectric Er 4.3 loss tangent 0.02
> 1 oz solid plane.
>
> The two pictures showed a trace to trace separation of 1 mills ...
> ie 1X
> trace to plane distance and 30 mills ... ie 10X trace to plane
> distance.
>
> In both cases the traces were 5 mills wide and 3 mills above the
> ground plane.
>
>
> TFox
>
> At 03:43 PM 7/2/2007, Grasso, Charles wrote:
>
> >Terry - A quick check shows that your results were derived using a
> >microstrip cross section with no mask coating. Is that correct?
> >
> >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
> >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
> >http://www.siemc.com/SI_List.htm
> >
> >The link has a schematic and two simulation examples. One example
> is
> >very
> >close trace to trace spacing, the other has very wide trace to
> trace
> >spacing. In both cases the traces are 20 inches long using a PCI
> >Express
> >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
> >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="----=_NextPart_002_0008_01C7B973.5B78CED0"
> > > >
> > > >------=_NextPart_002_0008_01C7B973.5B78CED0
> > > >Content-Type: text/plain;
> > > > charset="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.
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >------=_NextPart_002_0008_01C7B973.5B78CED0
> > > >Content-Type: text/html;
> > > > charset="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 = do design=20 parts that
> other
> >people
> > >
> > > >put on boards. We are working on = a new =20 (patent protected)
> > >concept:
> > > >the " DC-blocking = transmission-line".
> > > >Basically the idea is to build a = pair of=20 capacitors that
> can be
> > > >intercalated on the differential signal = traces,=20 having a
> > > >controlled characteristic impedance between the two capacitors,
> =
> > > >the=20 obvious scope is to reduce the reflections that may show
> up
> >due
> > > >the = DC-blocking capacitors.
> > > >One request, we have, is that the=20 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=20 question is:
> does
> > > >anyone have a different approach to this = problem?
> > > >Thanks for any suggestion,=20 George.
> > > >
> > > >
> > > >
> > > >
> > > >------=_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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