headers
Loyer, Jeff | 1 Oct 2007 04:47
Picon
Favicon

Re: AC Coupled Signals

Hi Istvan,
Could you point me towards more information on the "voltage transfer
ratio", and the difference between it and s21/s12?  When I did the pulse
response of a system where S21 =3D S12 (though S11 and S22 were very
different, and the reflections were significant), it came out equal (p21
=3D p12, see my posting of 9/15).  Thus, I think the eye diagram will =
come
out equal if S21 =3D S12.  =20

Thanks,
Jeff Loyer


-----Original Message-----
From: si-list-bounce-uGLqWuYN4qMgsBAKwltoeQ <at> public.gmane.org [mailto:si-list-bounce-uGLqWuYN4qMgsBAKwltoeQ <at> public.gmane.org]
On Behalf Of Istvan Novak
Sent: Saturday, September 29, 2007 12:38 AM
To: Chris.Cheng-sN2YdCRo948 <at> public.gmane.org
Cc: lifeatthesharpend; signalintegrity-Wuw85uim5zDR7s880joybQ <at> public.gmane.org; ron-Zo3/zdQu5IxBDgjK7y7TUQ <at> public.gmane.org;
si-list-uGLqWuYN4qMgsBAKwltoeQ <at> public.gmane.org
Subject: [SI-LIST] Re: AC Coupled Signals

Chris and All,

I think the source of misunderstandigs might stem from the fact that in
linear, time-invariant, reciprocal networks S21=3DS12 regardless of the
sequence of the smaller building blocks within the network, BUT, the eye
diagram shows us voltage transfer ratio between source and load, and it
is NOT S21; the voltage transfer ratio DOES depend on the sequence of
contributing blocks.  This happens also with linear source and load and
(Continue reading)

Permalink | Reply | 7 comments |
headers
istvan novak | 1 Oct 2007 13:46
Picon

Re: AC Coupled Signals

Hi Jeff,

Let me see if I can summarize this in simple physical terms. The 
scattering matrix
deals with power values.  In a reciprocal  network, the 'through' power 
is the
same regardless of the direction we go.  The node voltages, on the other 
hand,
depend on the local impedance levels, which are related to S11, S22 and
source and load reflection coefficients. 

So probably a more generalized condition is that we can shuffle around 
reciprocal
building blocks inside a cascaded network, and the resulting eye diagram 
will
stay the same as long as we do not change S11 and S22.

Going back to your simulations: if you calculate the pulse response of your
example circuits strictly from S21 of the network, I agree, it will not 
change,
since S21 will not change as you move the reciprocal building blocks 
around. 
Your eye diagram, however, should be usually calculated as Vout/Vsource
(and for sake of simplicity, we usually assume linear driver and receiver
impedances, where their linearity does not change this argument). This 
voltage
transfer ratio can be analytically calculated if you wish, from the 
S-parameter
flow graph.  The resulting formula is symmetrical in S12 and S21, but
asymmetrical in S11, S22 as well as source and load reflection
(Continue reading)

Permalink | Reply | 6 comments |
headers
Loyer, Jeff | 1 Oct 2007 16:34
Picon
Favicon

Re: AC Coupled Signals

Hello Istvan,
You're keying in to what was surprising to me.  For the asymmetric lossy
network I simulated, I noted that the pulse response remained constant,
regardless of direction of simulation.  Of course, S11 and S22 changed
dramatically.

The pulse response was not a derivation of the s-params; it was merely
Vout (the circuit driven with an arbitrarily chosen 2V source) of a
simulation of the actual network (3 lossy lines).

So, it appears that the pulse response and insertion loss remained
constant, even though the return loss varied dramatically.  I wasn't
surprised to have the insertion loss stay constant, but couldn't have
predicted whether the pulse reponse would also remain constant, though I
suspected it would.  This implies the eye diagram would also be the
same, regardless of direction of excitation.

Having the pulse response remain constant appears contrary to your
experience.  Any explanation?

Thanks for your thoughts,
Jeff Loyer

-----Original Message-----
From: Istvan.Novak@... [mailto:Istvan.Novak@...]=20
Sent: Monday, October 01, 2007 4:46 AM
To: Loyer, Jeff
Cc: istvan.novak@...; si-list@...
Subject: Re: [SI-LIST] Re: AC Coupled Signals
(Continue reading)

Permalink | Reply | 5 comments |
headers
Dmitriev-Zdorov, Vladimir | 1 Oct 2007 17:46
Favicon

Re: si-list Digest V7 #326

Hi Jeff,

Excuse me for jumping in. It just happened to me recently to refresh my
memory about the relation between S parameters and "voltage transfer
ratio", VTR, (where the latter I think is the ratio of the voltage
across the load to the voltage on the input voltage source, in AC mode).

Actually, VTR is completely defined by S21 if:

- S-parameters were measured for the entire 2-port where the 1-st port
is to attach the source and the 2-nd port is for load;
- the source's internal impedance and the load's impedance are equal the
corresponding S-parameter reference impedances (these two are often
equal but this is not necessary)

If either of these two conditions isn't true, S21 and VTR are not
related with a factor 0.5 (VTR # 0.5*S12)

Vladimir

-----Original Message-----
From: FreeLists Mailing List Manager [mailto:ecartis@...]=20
Sent: Sunday, September 30, 2007 9:21 PM
To: si-list digest users
Subject: si-list Digest V7 #326

Subject: [SI-LIST] Re: AC Coupled Signals
Date: Sun, 30 Sep 2007 19:47:54 -0700
From: "Loyer, Jeff" <jeff.loyer@...>
(Continue reading)

Permalink | Reply | 0 comments |
headers
Xin Wu | 1 Oct 2007 21:48
Picon
Favicon

Re: What to do with "isolation" conductors in ribbon cable?

Hi Jeff,=0AIf the isolation line ties to the ground directly, the character=
istic impedance of the signal net changes -- it is simliar to the change fr=
om a microstrip line to a stripline. =0AI think the best approach may proba=
bly be terminating the iso_line with matched loads on both ends.=0ABest, =
=0AXin=0A =0AXin Wu, Ph.D=0AProduct Manager, Ansys Inc.=0AAustin, TX 78749=
=0A=0A=0A----- Original Message ----=0AFrom: "Loyer, Jeff" <jeff.loyer <at> inte=
l.com>=0ATo: si-list@...=0ASent: Thursday, September 27,
2007 4:1=
3:39 PM=0ASubject: [SI-LIST] What to do with "isolation" conductors in ribb=
on cable?=0A=0A=0AI have a design where I have extra conductors in my ribbo=
n cable=0A("off-the-shelf, same-thing-we've-been-using FOREVER", no shieldi=
ng,=0Aribbon cable), allowing me to put grounds (or whatever I want) betwee=
n=0Asignals.  But, I'm not sure that grounds provide the best isolation.=0A=
I'm wondering if those isolation conductors shouldn't be terminated to=0Agr=
ound using 50 ohm resistors (or whatever the impedance of the cable=0Ais).=
=0A=0A=0AFor example, the pinout may be:=0A=0AGND  S1  ISOLATION_CONDUCTOR =
 S2  GND =0A=0A=0A=0AKeep in mind that all conductors are identical while t=
hey're in the=0Aribbon cable environment.  GND, S1, ISOLATION_CONDUCTOR, et=
c. have no=0Aidea whether they're supposed to a signal, ground, or whatever=
.=0A=0A=0A=0AIs the "ISOLATION_CONDUCTOR" (between S1 and S2) best tied dir=
ectly to=0AGND at both ends of the connector, or better tied to GND through=
 a=0Aresistor matching the characteristic impedance of the cable?=0A=0A=0A=
=0AIf it's tied directly to ground, it seems to represent a resonant=0Astru=
cture. Or, in the time domain, the FEXT/NEXT induced on it would be=0Acoupl=
ed to the other signal, and also bounce back at the interface with=0Aground=
 (rho =3D -1). But, if half the return current is flowing in it=0A(which, b=
y symmetry, it is), I don't want the discontinuity at the=0Aresistor.=0A=0A=
=0A=0ATerminated at both ends, I think it would couple less energy between =
the=0Asignals. =0A=0A=0A=0AThe only empirical data I have remotely tied to =
this is when I had a GND=0Aconductor which was only tied to GND on one end =
(Continue reading)

Permalink | Reply | 0 comments |
headers
Patrick Lam | 2 Oct 2007 00:05

Free Webinar about Co-Design b/w IC and Package for Power Integrity

=20
Hi All,

Apache and Optimal will have a free webinar about IC and Package design =
for  Power Integrity. Please see the  registration info. and details =
below.=20

Topic : Towards True Co-Design: Bridging the Gap between IC and Package =
Design for Power Integrity=20

=20

Overview:=20

For many years, the need for chip-package co-design to rapidly meet =
increasingly tight signal and power integrity (SI/PI) constraints in a =
cost-effective way has been more than obvious. Increasing functional =
integration, higher speed input-output signaling, and low-power design =
techniques have continued to exacerbate this need. "Co-design" as it is =
practiced today, however, is often little more than isolated design of =
the chip and package followed by co-optimization across product =
generations. Existing EDA tools and analysis techniques address SI/PI =
issues at the package and chip levels, but not with an integrated =
approach, which is needed for accurate and actionable tradeoff analyses.

In this webinar, we explore the symmetrical use of package-aware chip =
analysis and chip-aware package analysis to address true IC-Package =
co-design. The chip-package core power delivery network (PDN) is =
analyzed for static IR drop and dynamic voltage drop (DvD), pointing to =
design improvements through floor planning, decoupling capacitance, and =
(Continue reading)

Permalink | Reply | 0 comments |
headers
istvan novak | 2 Oct 2007 01:14
Picon

Re: AC Coupled Signals

Jeff,

My talented friend, Gustavo Blando, with whom we analyzed this situation 
a few
years back, reminded me that the voltage-transfer function formulas can be
found for instance in "MicroWave Transistor Amplifiers", Guillermo 
Gonzales, Page 185.
You can also look at L. S. Dutta, T. Hillmann-Ruge, “Application of Ring 
Oscillators to
Characterise Transmission Lines in VLSI Circuits,” IEEE Transactions on 
Components,
Packaging, and Manufacturing Technology - Part B., Vol. 18, No. 4, 
November 1995,
pp. 651-657. Note that you will find various expressions; you may want 
to pick the
Vout/Vsource formulas, as opposed to Vout/Vin. You will see that the 
voltage transfer
ratio is, in general, different from S21.

Regards,
Istvan Novak
SUN Microsystems

Loyer, Jeff wrote:

>Hello Istvan,
>You're keying in to what was surprising to me.  For the asymmetric lossy
>network I simulated, I noted that the pulse response remained constant,
>regardless of direction of simulation.  Of course, S11 and S22 changed
>dramatically.
(Continue reading)

Permalink | Reply | 4 comments |
headers
stebla01 | 2 Oct 2007 09:43

Re: What to do with "isolation" conductors in ribbon cable?

I've simulated this situation to look at the effect of inductively 
coupled noise into the ribbon cable. Each signal conductor was adjacent 
to a spare conductor. The result of the simulation was that the spare 
conductors should be tied to ground at both ends and that the 
inductively coupled noise was smallest on the signal conductors nearest 
the centre of the ribbon cable. However, in my case the inductive noise 
was at 20kHz and so the cable much less that a wavelength so I did not 
model the ribbon cable as a transmission line. However, it seems to me 
that the idea is to use the spare conductors to try to approximate a 
ground plane made out out a mesh of discrete wires; hence connecting 
the spare conductors to ground would still make sense at higher 
frequency.

Stephen

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

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

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

List technical documents are available at:
                http://www.si-list.net

List archives are viewable at:     
		http://www.freelists.org/archives/si-list
(Continue reading)

Permalink | Reply | 2 comments |
headers
Alex Li | 2 Oct 2007 11:43
Picon

How to qualify Component Video(YPrPb)??

Content-Type: text/plain;
	charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
 =20

Hi, Seniors:

=20

Do any body know how to qualify Component Video(YPrPb) signal, thanks~

=20

=20

Best Regards~

Alex Li

=20

-- Binary/unsupported file stripped by Ecartis --
-- Type: image/gif
-- File: image001.gif
-- Desc: image001.gif

------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@... with 'unsubscribe' in the Subject field
(Continue reading)

Permalink | Reply | 2 comments |
headers
Kunal Sabavat | 2 Oct 2007 16:46
Picon
Favicon

Emission level vary for same type of SATA cables but different vendors

Hello,

  I am seeing different levels of EMI measured values from lab for same type of SATA cables but from two
different vendors. One of the vendors cable shows much higher EMI values compared with another vendor
cable. measurement setup is same for two vendors cables. I still don't have full measurement report.
these are SATA internal cables, length of the cable is half meter.

  Can someone explain what could be wrong with the cable showing higher EMI level? Taking cable TDR Impedance
scan will help us understand?

  --
  Kunal

---------------------------------
 Did you know? You can CHAT without downloading messenger.  Click here

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

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

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

List technical documents are available at:
                http://www.si-list.net

List archives are viewable at:
(Continue reading)

Permalink | Reply | 2 comments |

Gmane