[SI-LIST] Re: Diff.Pairs

  • From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
  • To: "San Miguel, Shane" <shane.san.miguel@xxxxxxxxx>,"silist" <si-list@xxxxxxxxxxxxx>
  • Date: Thu, 9 Oct 2003 18:05:37 -0700

Shane,

Why are your anticipating a difference in propagation velocity?

Lee


> [Original Message]
> From: San Miguel, Shane <shane.san.miguel@xxxxxxxxx>
> To: silist <si-list@xxxxxxxxxxxxx>
> Date: 10/9/2003 3:48:54 PM
> Subject: [SI-LIST] Re: Diff.Pairs
>
> When routing differential pairs (say clk and /clk) how does one =
> accomodate the change in propagation velocity relative to the data =
> signals?  Do you increase the trace length (time of flight) for the data =
> signals to compensate for the timing delta?
>
> Shane San Miguel=20
>
>
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Chris McGrath
> Sent: Thursday, October 09, 2003 12:04 PM
> To: silist
> Subject: [SI-LIST] Re: Diff.Pairs
>
>
>
> My experience has generally been that routing the differential pairs
> close together has the benefit of allowing the designer to increase
> routing density and can be routed closer together than two single ended
> signals.  I am very interested in understanding if there are benefits of
> a tightly coupled differential pair where the electromagnetic coupling
> yields better SI or EMI (or other) characteristics.
>
> -Chris
>
>
> > -----Original Message-----
> > From: Scott McMorrow [mailto:scott@xxxxxxxxxxxxx]=3D20
> > Sent: Thursday, October 09, 2003 2:41 PM
> > To: leeritchey@xxxxxxxxxxxxx; silist
> > Subject: [SI-LIST] Re: Diff.Pairs
> >=3D20
> >=3D20
> > Lee,
> > You said about differntial pair nets:
> >=3D20
> >     "unless they are placed close enough together that there is some
> >     interaction. This interaction is not beneficial."
> >=3D20
> > You have yet to prove that the coupled interaction of closely =
> spaced=3D20
> > differential pairs is not beneficial.  Please show the proof and =
> the=3D20
> > data.  Analytically, electromagnetically and observationally there =
> is=3D20
> > not a problem with using close spaced differential pairs.   You =
> are=3D20
> > stating your opinion as an absolute fact that is not supported by=3D20
> > science.  This is quite contrary to your stated belief in good=3D20
> > engineering and science.
> >=3D20
> > scott
> >=3D20
> >=3D20
> > Lee Ritchey wrote:
> >=3D20
> > >Why do people try so hard to make the coupling between the=3D20
> > two members=3D20
> > >of a pair so important.  These are two independent signals=3D20
> > that travel=3D20
> > >over planes independently unless they are placed close=3D20
> > enough together=3D20
> > >that there is some interaction.  This interaction is not beneficial.
> > >
> > >Lee
> > >
> > >
> > > =3D20
> > >
> > >>[Original Message]
> > >>From: Knighten, Jim L <JK100005@xxxxxxxxxxxxxxxx>
> > >>To: <leeritchey@xxxxxxxxxxxxx>; Doug Brooks <doug@xxxxxxxxxx>;
> > >>   =3D20
> > >>
> > ><si-list@xxxxxxxxxxxxx>
> > > =3D20
> > >
> > >>Date: 10/9/2003 10:40:29 AM
> > >>Subject: RE: [SI-LIST] Re: Diff.Pairs
> > >>
> > >>Lee,
> > >>
> > >>Your post is interesting!
> > >>
> > >>Differential signaling is usually implemented with coupled=3D20
> > >>transmission lines.  The mutual coupling between the traces=3D20
> > affect the=3D20
> > >>two modes that
> > >>   =3D20
> > >>
> > >are
> > > =3D20
> > >
> > >>always present (even and odd modes). In the traditional=3D20
> > configuration,=3D20
> > >>the two traces are parallel and of the same width and thickness =
> and=3D20
> > >>located adjacent to a plane.  The degree of coupling between =
> the=3D20
> > >>traces is usually described as "loosely coupled" or=3D20
> > "tightly coupled." =3D20
> > >>In either case, if
> > >>   =3D20
> > >>
> > >the
> > > =3D20
> > >
> > >>signal and signal traces are perfectly differential (i.e., no=3D20
> > >>imbalance, perfectly symmetrical), then there is always=3D20
> > current in the=3D20
> > >>adjacent
> > >>   =3D20
> > >>
> > >ground
> > > =3D20
> > >
> > >>plane, but the net current in the longitudinal direction (the=3D20
> > >>direction of the traces) is zero.  The currents that exist in =
> the=3D20
> > >>adjacent plane are circulating currents that reflect the=3D20
> > distributed=3D20
> > >>coupling between the traces down the length of the=3D20
> > transmission line.
> > >>
> > >>So, what if the two coupled traces are not co-planar, i.e.,=3D20
> > not in the
> > >>   =3D20
> > >>
> > >same
> > > =3D20
> > >
> > >>plane?  Well, you still have two coupled transmission lines, but the
> > >>   =3D20
> > >>
> > >mutual
> > > =3D20
> > >
> > >>capacitance and inductance between them may be different=3D20
> > than if they=3D20
> > >>were co-planar, hence the even and odd mode impedances may be=3D20
> > >>different.  These non-co-planar coupled lines can still carry=3D20
> > >>differential signals, though.
> > >>   =3D20
> > >>
> > >
> > > =3D20
> > >
> > >>What if the two coupled lines were not co-planar and=3D20
> > actually had the
> > >>   =3D20
> > >>
> > >ground
> > > =3D20
> > >
> > >>plane between them?  This is just a special case of the =
> "loosely=3D20
> > >>coupled" case, in that the lines are now not coupled at=3D20
> > all.  Still,=3D20
> > >>the lines can support differential signaling, but the =
> relationships=3D20
> > >>between even and odd modes are not quite the same as when they =
> were=3D20
> > >>coupled. (Perhaps even mode and odd mode impedances are equal?)
> > >>
> > >>So, how about current in the ground plane?  For perfect=3D20
> > differential=3D20
> > >>signaling, the net current in the plane is zero.  When you=3D20
> > introduce=3D20
> > >>imbalance, either in the signal source, or in the signal path, =
> you=3D20
> > >>create net longitudinal current in the ground plane.  This=3D20
> > is the even=3D20
> > >>mode
> > >>   =3D20
> > >>
> > >signal,
> > > =3D20
> > >
> > >>which has no bearing on your intended differential signal (the =
> odd=3D20
> > >>mode)
> > >>   =3D20
> > >>
> > >and
> > > =3D20
> > >
> > >>represents an EMI source on the ground plane.
> > >>
> > >>If you route differential signals on different layers, it=3D20
> > may be more=3D20
> > >>difficult to maintain balance (symmetry) in the traces than if =
> the=3D20
> > >>traces were co-planar.  If this is true, you have more=3D20
> > potential for=3D20
> > >>EMI issues.
> > >>
> > >>...My thoughts
> > >>
> > >>Jim
> > >>
> > >>________________________
> > >>James L. Knighten, Ph.D.
> > >>Teradata, a division of NCR                 http://www.ncr.com
> > >>17095 Via del Campo
> > >>San Diego, CA 92127
> > >>tel: 858-485-2537
> > >>fax: 858-485-3788
> > >>
> > >>
> > >>-----Original Message-----
> > >>From: Lee Ritchey [mailto:leeritchey@xxxxxxxxxxxxx]
> > >>Sent: Thursday, October 09, 2003 9:30 AM
> > >>To: Doug Brooks; si-list@xxxxxxxxxxxxx
> > >>Subject: [SI-LIST] Re: Diff.Pairs
> > >>
> > >>If this discussion is about differential pairs travelling over =
> the=3D20
> > >>planes of a PCB, the return current for each member of the pair=3D20
> > >>travels on the plane over which it travels, not on the=3D20
> > other wire.  If=3D20
> > >>they are very tightly coupled to each other, perhaps 5% of=3D20
> > the current=3D20
> > >>from one travels in the other.  It is coincidental that the two=3D20
> > >>currents are equal in magnitude and opposite.  They don't=3D20
> > have to be. =3D20
> > >>Their "return currents" still travel on the plane, not on the =
> other=3D20
> > >>wire.
> > >>
> > >>As far as EMI is concerned, it has been demonstrated many=3D20
> > times, once=3D20
> > >>in the paper done by Doug Brooks with the staff at UMR, that =
> traces=3D20
> > >>traveling over planes are not a detectable source of EMI. =3D20
> > Therefore,=3D20
> > >>constraining the routing of differential pairs to prevent them =
> from=3D20
> > >>creating EMI is not appropriate or necessary.
> > >>
> > >>It is still true that the two members of a differential=3D20
> > pair are two=3D20
> > >>independent signals traveling on two independent=3D20
> > transmission lines.=3D20
> > >>All they have in common is that the have equal amplitudes=3D20
> > and are 180=3D20
> > >>degrees out of phase with each other.  If the protocol is=3D20
> > LVDS, each=3D20
> > >>member of the pair should be parallel terminated in an=3D20
> > impedance equal=3D20
> > >>to Zo for that line to Vref (about 1.25V) which is half way =
> between=3D20
> > >>the two logic levels.
> > >>
> > >>As long as the two signals switch at the same time, the current=3D20
> > >>flowing
> > >>   =3D20
> > >>
> > >out
> > > =3D20
> > >
> > >>of Vref into one line is the same magnitude an opposite in=3D20
> > polarity to
> > >>   =3D20
> > >>
> > >that
> > > =3D20
> > >
> > >>flowing into the other.  The net current into and out of the =
> Vref=3D20
> > >>terminal is zero, so we can omit the connection.  When we=3D20
> > do this, we=3D20
> > >>have two resistors, each of value Zo across the ends of the two=3D20
> > >>transmission
> > >>   =3D20
> > >>
> > >lines.
> > > =3D20
> > >
> > >>For convenience, we use one resistor of value 2 X Zo.  This=3D20
> > is not a=3D20
> > >>differential impedance of 100 ohms, but two parallel=3D20
> > terminations of=3D20
> > >>value Zo terminating two transmission lines each of impedance Zo.
> > >>
> > >>As long as the two edges switch at the same time, there is=3D20
> > no current=3D20
> > >>imbalance and all is well.  Soon as one edge switches before =
> the=3D20
> > >>other, there is a need for a momentary current spike to=3D20
> > flow into or=3D20
> > >>out of the Vref terminal.  If there is no connection to=3D20
> > Vref for the=3D20
> > >>current flow,
> > >>   =3D20
> > >>
> > >the
> > > =3D20
> > >
> > >>result is the edges are degraded.  To avoid this=3D20
> > degradation, a very=3D20
> > >>small capacitor is often connected between the two resistors =
> and=3D20
> > >>ground.  This
> > >>   =3D20
> > >>
> > >is
> > > =3D20
> > >
> > >>a very common termination for 2.4 GB/S signal links.
> > >>
> > >>It is time to stop representing differential signals as=3D20
> > needing to be=3D20
> > >>tightly coupled to each other in order to operate properly.  It =
> is=3D20
> > >>simply not so.  I have routed thousands of differential=3D20
> > signal where=3D20
> > >>each member of the pair is on a different layer.  If this were =
> not=3D20
> > >>possible, 1 mm
> > >>   =3D20
> > >>
> > >pitch
> > > =3D20
> > >
> > >>BGAs with differential signals would be un routable.  There=3D20
> > are tens=3D20
> > >>of thousands of such parts being shipped every month on PCBs =
> where=3D20
> > >>they are routed apart from each other.
> > >>
> > >>This is all described in my recently published book, "Right=3D20
> > the First
> > >>   =3D20
> > >>
> > >Time,
> > > =3D20
> > >
> > >>A Practical Handbook on High Speed PCB and System Design". =3D20
> > It is also=3D20
> > >>covered in Howard Johnson's new book whose title escapes me at the
> > >>   =3D20
> > >>
> > >moment..
> > > =3D20
> > >
> > >>Lee
> > >>
> > >>
> > >>   =3D20
> > >>
> > >>>[Original Message]
> > >>>From: Doug Brooks <doug@xxxxxxxxxx>
> > >>>To: <si-list@xxxxxxxxxxxxx>
> > >>>Date: 10/3/2003 1:02:25 PM
> > >>>Subject: [SI-LIST] Re: Diff.Pairs
> > >>>
> > >>>Tight may be a relative word. But a differential pair constitutes a
> > >>>     =3D20
> > >>>
> > >>"loop"
> > >>   =3D20
> > >>
> > >>>in EMI terms. That is, the loop is the area encompassed by=3D20
> > the signal
> > >>>     =3D20
> > >>>
> > >and
> > > =3D20
> > >
> > >>>its return. Smaller loop areas perform better than larger=3D20
> > loop areas
> > >>>     =3D20
> > >>>
> > >when
> > > =3D20
> > >
> > >>>EMI is a concern. The closer the differential pair, the smaller =
> is=3D20
> > >>>the
> > >>>loop. If we are NOT concerned about EMI, then this is not=3D20
> > an issue. If
> > >>>     =3D20
> > >>>
> > >we
> > > =3D20
> > >
> > >>>ARE, then we might want to pay attention to this and keep the =
> loop=3D20
> > >>>small
> > >>>     =3D20
> > >>>
> > >>by
> > >>   =3D20
> > >>
> > >>>routing the traces close together.
> > >>>
> > >>>The equal spacing "requirement" comes from the control of=3D20
> > reflections
> > >>>     =3D20
> > >>>
> > >(ie
> > > =3D20
> > >
> > >>>transmission line termination issues.) IF we are concerned about
> > >>>reflections, THEN we need a constant impedance everywhere along the
> > >>>     =3D20
> > >>>
> > >>trace.
> > >>   =3D20
> > >>
> > >>>IF the (differential) traces are close together (for EMI =
> reasons)=3D20
> > >>>THEN
> > >>>     =3D20
> > >>>
> > >>they
> > >>   =3D20
> > >>
> > >>>will interact (a very special case of crosstalk, which in this
> > >>>     =3D20
> > >>>
> > >particular
> > > =3D20
> > >
> > >>>case [signals --- being equal and opposite --- are exactly=3D20
> > correlated
> > >>>     =3D20
> > >>>
> > >>with
> > >>   =3D20
> > >>
> > >>>each other] is not a problem.) IF we want to keep a constant=3D20
> > >>>impedance
> > >>>along the traces, THEN we must keep a "constant" spacing=3D20
> > between them,=3D20
> > >>>because the coupling between them, and therefore the =
> differential=3D20
> > >>>impedance, will vary if we don't.
> > >>>
> > >>>There is a further design rule you sometimes hear, that being =
> that=3D20
> > >>>the
> > >>>differential traces must be equal length. This is NOT for timing
> > >>>     =3D20
> > >>>
> > >reasons,
> > > =3D20
> > >
> > >>>but for common mode reasons. A strong assumption we make about
> > >>>     =3D20
> > >>>
> > >>differential
> > >>   =3D20
> > >>
> > >>>signals is that they are equal and opposite, and therefore=3D20
> > there is=3D20
> > >>>no
> > >>>return signal through the ground system. Even if the signals are
> > >>>     =3D20
> > >>>
> > >perfect,
> > > =3D20
> > >
> > >>>if the traces are different length, then the signal will=3D20
> > not arrive=3D20
> > >>>at
> > >>>     =3D20
> > >>>
> > >>the
> > >>   =3D20
> > >>
> > >>>far end at exactly the same time and the signals will not=3D20
> > be "equal=3D20
> > >>>and
> > >>>opposite" at the receiver. Just a couple of degrees phase=3D20
> > shift can make
> > >>>     =3D20
> > >>>
> > >>a
> > >>   =3D20
> > >>
> > >>>surprising difference between the signals when we are talking about
> > >>>(square-wave) clock signals. If the signals are not=3D20
> > exactly equal and=3D20
> > >>>opposite, then there MUST be a net current flowing=3D20
> > somewhere else. This=3D20
> > >>>will quite likely be a common mode noise current that=3D20
> > might cause an EMI
> > >>>     =3D20
> > >>>
> > >>issue.
> > >>   =3D20
> > >>
> > >>>None of the differential signal trace design rules are =
> necessary=3D20
> > >>>taken
> > >>>     =3D20
> > >>>
> > >by
> > > =3D20
> > >
> > >>>themselves. This is important to recognize. But if are =
> concerned=3D20
> > >>>about
> > >>>certain SI issues, they might lead to some design=3D20
> > considerations which
> > >>>     =3D20
> > >>>
> > >>THEN
> > >>   =3D20
> > >>
> > >>>might cascade (like a domino effect) into other areas.
> > >>>
> > >>>This is in my book, too...............
> > >>>
> > >>>Doug Brooks
> > >>>
> > >>>
> > >>>
> > >>>
> > >>>At 11:41 AM 10/3/2003 -0700, Lee Ritchey wrote:
> > >>>     =3D20
> > >>>
> > >>>>More than that, it does not have any benefit.  Tight coupling =
> of=3D20
> > >>>>differential pairs forces the traces to be narrower=3D20
> > increasing the=3D20
> > >>>>skin effect losses.  Also, this tight coupling is going=3D20
> > to result in=3D20
> > >>>>good
> > >>>>       =3D20
> > >>>>
> > >old
> > > =3D20
> > >
> > >>>>cross talk that actually degrades the edges.
> > >>>>
> > >>>>How the notion of tight coupling of differential pairs as=3D20
> > beneficial
> > >>>>       =3D20
> > >>>>
> > >got
> > > =3D20
> > >
> > >>>>started is a mystery to me.  There are several references=3D20
> > that show
> > >>>>       =3D20
> > >>>>
> > >that
> > > =3D20
> > >
> > >>>>tight coupling is not beneficial, one of them is Howard Johnson's
> > >>>>       =3D20
> > >>>>
> > >latest
> > > =3D20
> > >
> > >>>>book, at least one column he has written and my recently =
> released=3D20
> > >>>>book.
> > >>>>
> > >>>>Lee Ritchey
> > >>>>
> > >>>>
> > >>>>       =3D20
> > >>>>
> > >>>>>[Original Message]
> > >>>>>From: Duane Takahashi <duanet@xxxxxxxxxxxxxxxxxxxxxx>
> > >>>>>To: <si-list@xxxxxxxxxxxxx>
> > >>>>>Date: 10/2/2003 3:58:59 PM
> > >>>>>Subject: [SI-LIST] Re: Diff.Pairs
> > >>>>>
> > >>>>>Hi Juergen:
> > >>>>>
> > >>>>>Aligning the stack up for the broadside coupled diff lines is
> > >>>>>         =3D20
> > >>>>>
> > >>expensive.
> > >>   =3D20
> > >>
> > >>>>>   You can do this, but it drives up the cost of the board.
> > >>>>>
> > >>>>>Duane
> > >>>>>
> > >>>>>         =3D20
> > >>>>>
> > >>>>>>Hi Juergen,
> > >>>>>>You can find lots of  application notes
> > >>>>>>especially with respect to process variation
> > >>>>>>on differential pairs here:
> > >>>>>>
> > >>>>>>
> > >>>>>>www.polarinstruments.com/support/cits/cits_index.html
> > >>>>>>
> > >>>>>>In particular this one may be of interest:
> > >>>>>>
> > >>>>>>
> > >>>>>>How measured impedance may vary from field solver calculations
> > >>>>>>           =3D20
> > >>>>>>
> > >when
> > > =3D20
> > >
> > >>>>>>using woven glass reinforced=3D20
> > >>>>>><http://www.polarinstruments.com/support/cits/AP139.html
> > >laminates
> > >>>>>>
> > >>>>>>www.polarinstruments.com/support/cits/AP139.html
> > >>>>>>
> > >>>>>>
> > >>>>>>And this note:
> > >>>>>>
> > >>>>>>Copper thickness, edge coupled lines and
> > >>>>>>characteristic=3D20
> > >>>>>><http://www.polarinstruments.com/support/cits/AP151.html
> > >impedance
> > >>>>>>
> > >>>>>>
> > >>>>>>www.polarinstruments.com/support/cits/AP151.html
> > >>>>>>
> > >>>>>>
> > >>>>>>
> > >>>>>>Hope this helps....
> > >>>>>>
> > >>>>>>
> > >>>>>>Kind regards
> > >>>>>>Martyn Gaudion
> > >>>>>>www.polarinstruments.com
> > >>>>>>T: +44 1481 253081
> > >>>>>>F: +44 1481 252476
> > >>>>>>M: +44 7710 522748
> > >>>>>>E: martyn@xxxxxxxxxxxxxxxxxxxx
> > >>>>>>
> > =3D
>
>>>>>>=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D=
> 3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D
> =3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D=
> 3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D
> > >>>>>>  Controlled Impedance & Signal integrity tools
> > >>>>>>  for the Printed circuit fabrication industry=3D20
> > =3D
>
>>>>>>=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D=
> 3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D
> =3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D=
> 3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D
> > >>>>>>
> > >>>>>>
> > >>>>>>
> > >>>>>>
> > >>>>>>
> > >>>>>>
> > >>>>>>At 19:00 02/10/2003, you wrote:
> > >>>>>>
> > >>>>>>           =3D20
> > >>>>>>
> > >>>>>>>I am seeking help in finding enlightenment regarding=3D20
> > electrical=3D20
> > >>>>>>>performance pros and cons and how manufacturing=3D20
> > tolerances play a
> > >>>>>>>             =3D20
> > >>>>>>>
> > >>role
> > >>   =3D20
> > >>
> > >>>>>>>when comparing side by side and tandem differential pairs. I'd
> > >>>>>>>             =3D20
> > >>>>>>>
> > >>>>appreciate
> > >>>>       =3D20
> > >>>>
> > >>>>>>>your opinion, experience, analysis, pointers to papers and
> > >>>>>>>             =3D20
> > >>>>>>>
> > >articels,
> > > =3D20
> > >
> > >>>>etc.
> > >>>>       =3D20
> > >>>>
> > >>>>>>>In return, I would offer to share a summary of the
> > >>>>>>>             =3D20
> > >>>>>>>
> > >>finding/discoveries
> > >>   =3D20
> > >>
> > >>>>>>>with interested parties.
> > >>>>>>>
> > >>>>>>>Thanks
> > >>>>>>>
> > >>>>>>>Juergen
> > >>>>>>>
> > >>>>>>>
> > >>>>>>>
> > >>>>>>>-------------------------------------------------------
> > ----------
> > >>>>>>>-
> > >>>>>>>To unsubscribe from si-list:
> > >>>>>>>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject
> > >>>>>>>             =3D20
> > >>>>>>>
> > >>field
> > >>   =3D20
> > >>
> > >>>>>>>or to administer your membership from a web page, go to:=3D20
> > >>>>>>>//www.freelists.org/webpage/si-list
> > >>>>>>>
> > >>>>>>>For help:
> > >>>>>>>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> > >>>>>>>
> > >>>>>>>List archives are viewable at:
> > >>>>>>>               //www.freelists.org/archives/si-list
> > >>>>>>>or at our remote archives:
> > >>>>>>>               http://groups.yahoo.com/group/si-list/messages
> > >>>>>>>Old (prior to June 6, 2001) list archives are viewable at:
> > >>>>>>>               http://www.qsl.net/wb6tpu
> > >>>>>>>
> > >>>>>>>             =3D20
> > >>>>>>>
> > >>>>>>
> > >>>>>>--------------------------------------------------------
> > ----------
> > >>>>>>To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx =
> with=3D20
> > >>>>>>'unsubscribe' in the Subject
> > >>>>>>           =3D20
> > >>>>>>
> > >>field
> > >>   =3D20
> > >>
> > >>>>>>or to administer your membership from a web page, go to:=3D20
> > >>>>>>//www.freelists.org/webpage/si-list
> > >>>>>>
> > >>>>>>For help:
> > >>>>>>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> > >>>>>>
> > >>>>>>List archives are viewable at:
> > >>>>>>            //www.freelists.org/archives/si-list
> > >>>>>>or at our remote archives:
> > >>>>>>            http://groups.yahoo.com/group/si-list/messages
> > >>>>>>Old (prior to June 6, 2001) list archives are viewable at:
> > >>>>>>            http://www.qsl.net/wb6tpu
> > >>>>>>
> > >>>>>>           =3D20
> > >>>>>>
> > >>>>>--
> > >>>>>Duane Takahashi              phone: 408-720-4200
> > >>>>>Greenfield Networks            fax: 408-720-4210
> > >>>>>255 Santa Ana Court          email: duanet@xxxxxxxxxxxxxxxxxxxxxx
> > >>>>>Sunnyvale, CA 94085
> > >>>>>
> > >>>>>* MOVING!  Please note new numbers and address *
> > >>>>>
> > >>>>>---------------------------------------------------------
> > ---------
> > >>>>>To unsubscribe from si-list:
> > >>>>>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject
> > >>>>>         =3D20
> > >>>>>
> > >field
> > > =3D20
> > >
> > >>>>>or to administer your membership from a web page, go to:=3D20
> > >>>>>//www.freelists.org/webpage/si-list
> > >>>>>
> > >>>>>For help:
> > >>>>>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> > >>>>>
> > >>>>>List archives are viewable at:
> > >>>>>              //www.freelists.org/archives/si-list
> > >>>>>or at our remote archives:
> > >>>>>              http://groups.yahoo.com/group/si-list/messages
> > >>>>>Old (prior to June 6, 2001) list archives are viewable at:
> > >>>>>              http://www.qsl.net/wb6tpu
> > >>>>>
> > >>>>>         =3D20
> > >>>>>
> > >>>>
> > >>>>------------------------------------------------------------------
> > >>>>To unsubscribe from si-list:
> > >>>>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the =
> Subject=3D20
> > >>>>field
> > >>>>
> > >>>>or to administer your membership from a web page, go to:=3D20
> > >>>>//www.freelists.org/webpage/si-list
> > >>>>
> > >>>>For help:
> > >>>>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> > >>>>
> > >>>>List archives are viewable at:
> > >>>>                //www.freelists.org/archives/si-list
> > >>>>or at our remote archives:
> > >>>>                http://groups.yahoo.com/group/si-list/messages
> > >>>>Old (prior to June 6, 2001) list archives are viewable at:
> > >>>>                http://www.qsl.net/wb6tpu
> > >>>>
> > >>>>       =3D20
> > >>>>
> > >>>Doug Brooks' new book, "Signal Integrity Issues and Printed Circuit
> > >>>     =3D20
> > >>>
> > >Board
> > > =3D20
> > >
> > >>>Design" has just been released by Prentice Hall. See details and
> > >>>     =3D20
> > >>>
> > >ordering
> > > =3D20
> > >
> > >>>info at www.ultracad.com
> > >>>
> > >>>     =3D20
> > >>>
> > >_____________________________________________________________
> > __________
> > >_____
> > > =3D20
> > >
> > >>__
> > >>   =3D20
> > >>
> > >>>------------------------------------------------------------------
> > >>>To unsubscribe from si-list:
> > >>>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the=3D20
> > Subject field
> > >>>
> > >>>or to administer your membership from a web page, go to:=3D20
> > >>>//www.freelists.org/webpage/si-list
> > >>>
> > >>>For help:
> > >>>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> > >>>
> > >>>List archives are viewable at:    =3D20
> > >>>         //www.freelists.org/archives/si-list
> > >>>or at our remote archives:
> > >>>         http://groups.yahoo.com/group/si-list/messages
> > >>>Old (prior to June 6, 2001) list archives are viewable at:
> > >>>                 http://www.qsl.net/wb6tpu
> > >>> =3D20
> > >>>     =3D20
> > >>>
> > >>
> > >>------------------------------------------------------------------
> > >>To unsubscribe from si-list:
> > >>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the=3D20
> > Subject field
> > >>
> > >>or to administer your membership from a web page, go to:=3D20
> > >>//www.freelists.org/webpage/si-list
> > >>
> > >>For help:
> > >>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> > >>
> > >>List archives are viewable at:    =3D20
> > >>          //www.freelists.org/archives/si-list
> > >>or at our remote archives:
> > >>          http://groups.yahoo.com/group/si-list/messages
> > >>Old (prior to June 6, 2001) list archives are viewable at:
> > >>          http://www.qsl.net/wb6tpu
> > >> =3D20
> > >>   =3D20
> > >>
> > >
> > >
> > >
> > >------------------------------------------------------------------
> > >To unsubscribe from si-list:
> > >si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
> > >
> > >or to administer your membership from a web page, go to:=3D20
> > >//www.freelists.org/webpage/si-list
> > >
> > >For help:
> > >si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> > >
> > >List archives are viewable at:    =3D20
> > >           //www.freelists.org/archives/si-list
> > >or at our remote archives:
> > >           http://groups.yahoo.com/group/si-list/messages
> > >Old (prior to June 6, 2001) list archives are viewable at:
> > >           http://www.qsl.net/wb6tpu
> > > =3D20
> > >
> > > =3D20
> > >
> >=3D20
> > --=3D20
> > Scott McMorrow
> > Teraspeed Consulting Group LLC
> > 2926 SE Yamhill St.
> > Portland, OR 97214
> > (503) 239-5536
> > http://www.teraspeed.com
> >=3D20
> >=3D20
> >=3D20
> >=3D20
> > ------------------------------------------------------------------
> > To unsubscribe from si-list:
> > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
> >=3D20
> > or to administer your membership from a web page, go to:=3D20
> > //www.freelists.org/webpage/si-list
> >=3D20
> > For help:
> >=3D20
> > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> >=3D20
> > List archives are viewable at:    =3D20
> >             //www.freelists.org/archives/si-list
> > or at our remote archives:
> >             http://groups.yahoo.com/group/si-list/messages=3D20
> > Old (prior to June 6, 2001) list archives are viewable at:
> >             http://www.qsl.net/wb6tpu
> >  =3D20
> >=3D20
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
> or to administer your membership from a web page, go to:
> //www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
> List archives are viewable at:    =20
>               //www.freelists.org/archives/si-list
> or at our remote archives:
>               http://groups.yahoo.com/group/si-list/messages=20
> Old (prior to June 6, 2001) list archives are viewable at:
>               http://www.qsl.net/wb6tpu
>  =20
>
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
> or to administer your membership from a web page, go to:
> //www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
> List archives are viewable at:     
>               //www.freelists.org/archives/si-list
> or at our remote archives:
>               http://groups.yahoo.com/group/si-list/messages 
> Old (prior to June 6, 2001) list archives are viewable at:
>               http://www.qsl.net/wb6tpu
>   



------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List archives are viewable at:     
                //www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages 
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
  

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