RE: [SI-LIST] : FW: Spectraquest Vs. XTK/XNS

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From: Chris Rokusek (crokusek@innoveda.com)
Date: Thu Oct 05 2000 - 10:37:55 PDT


Hassan,

(In answer to your request for more detail on how CM is calculated...)

Although I think you may be requesting too much info to be communicated over
this medium, here is a shot:

Innoveda offers three EMI tools in all:

        QUIET Expert - http://www.emclab.umr.edu/consortium/index.html
        QUIET - Built atop a Time-Domain SI --> FFT --> Green's function.
        QUIET3D - FDTD, predicts common mode currents on cables in a 3D system.

There is also a few applications of the tools here:

        http://www.innoveda.com/support/innovate/innews_06.html

QUIET Expert was co-developed in association with UMR. A number of white
papers describing UMR research may be found in the UMR link above. Most if
not all are IEEE copyrighted. Essentially the Expert System works
backwards, finding the dominant antennae, determine each's CM input
impedance, and then applying worst case noise to them that is result of DM
signal(s) analysis. This system's purpose is NOT to calculate actual EMI to
within a few dB, its purpose is to locate the MOST LIKELY problem areas of a
REAL BOARD and offer advice on how to improve them.

QUIET & QUIET3D can link together such that QUIET3D computes a transfer
function from a common mode noise source on the board to a common mode
current (small) segment on the cable (for all freq's of interest). This
transfer function is then used by QUIET to drive the cable. The long term
goal of QUIET & QUIET3D IS to accurately predict emissions from a PCB.
Since the "real PCB" problem is too complex for today's computer's to solve
in a reasonable amount of time so it must make assumptions and therefore
loses some accuracy. For example, one of its simplifications is that the
phase relation between signals is ignored--it stimulates one net at a time.

I encourage you to evaluate each EDA vendor's tool(s) at your site with the
docs and a real design (or a real problem).

Chris Rokusek
Innoveda

-----Original Message-----
From: owner-si-list@silab.eng.sun.com
[mailto:owner-si-list@silab.eng.sun.com]On Behalf Of Hassan Ali
Sent: Thursday, October 05, 2000 7:45 AM
To: Heiko Dudek
Cc: si-list
Subject: RE: [SI-LIST] : FW: Spectraquest Vs. XTK/XNS

I understand that common-mode (CM) emissions on a PCB result from many
phenomena and it is important for one to understand which of those phenomena
a particular EDA tool is capable of modeling.
For example, a CM voltage may result whenever there is any kind of physical
imbalance between the sending and the return path of a signal. This is the
case with many signals on a PCB. That kind of CM emission can indeed be
easily modelled with the Method of Moments just as the differential-mode
(DM) emission.
CM voltage may also result from ground-bounce (on ground planes) and voltage
drop on power planes. Signal traces (on the board) and external I/O cables
may be excited with this kind of CM voltage and radiate in a normal dipole
or folded dipole mode. This kind of CM emission, however, is very
complicated to model correctly with any of the presently available EDA
tools. Yes, indeed, a power plane modelling tool may help, but the problem
is trying to understand how various voltage differences on the power/ground
planes would excite several (in thousands) associated "antennas" (traces)
and come up with a good estimate of what would be the aggregate CM emission
value. And these voltage differences are not static - they are dynamic,
depending on gate switching scenarios.
And then there is CM emission due to voltage coupled on PCB traces and I/O
cables from apertures and seams of shielded enclosures. And on any diff-pair
line you have CM currents due to P and N signal timing skews and current
imbalance. In short, there are just too many phenomena that give rise to CM
emission and that's why so far, the only way to deal with it is to use
suppression techniques such as the use of filters, decoupling, CM chokes,
etc. and good board design techniques rather than using any kind of
prediction techniques.
So, Heiko (and others who spoke about various EDA tools), you may help us a
lot if you specify how your tools model CM emissions. Only saying that they
do model CM emissions is certainly not enough and can be misleading.
Hassan.

-----Original Message-----
From: Heiko Dudek [mailto:heikod@cadence.com]
Sent: Wednesday, October 04, 2000 6:22 PM
To: Ken Cantrell; Jim Freeman; Donald Telian
Cc: May, John; si-list
Subject: RE: [SI-LIST] : FW: Spectraquest Vs. XTK/XNS

Ken,
I slightly disagree ... let me explain.
The differentiation between common and differential mode emissions has a
very practical
background: the radiation from PCB structures can be categorized into
differential mode
and common mode emitters (I think this was first introduced by W. L. Weeks
in "Electro-
magnetic Theory for Engineering Applications", Wiley, 1964). A current loop
'antenna'
would be an emitter for differential mode emissions and a dipole or point
source 'antenna'
would be a common mode emitter. Differential mode emissions are relatively
easy to handle
even as a pre-layout estimation (SPECCTRAQuest SigXp can do this for you),
since the
loop area (formed by the signal path - the trace - and the return path -
somewhere on the
reference plane(s)) - as well as frequency and loop current (signal current,
calculated in a
standard SI simulation) can be determined. Dipole emitters (e.g. the voltage
drop along a
return current path on reference plane structure building dipoles at the
edges of a cut-out
or similar things happening in peripheral (conducting components around the
PCB) are
way more complicated to model. SPECCTRAQuest uses a 'method of moments'
approach
to calculate (both differential and common mode) emissions (you can actually
get the near-
field results as well as the far-field emissions) - while not taking
anything else into account
than the PCB itself.
And here's where I disagree. Cables are not the origin for common mode
emissions, they are
just the emitters (the 'antennas' for TEM waves between reference planes,
exited by point
source antennas - large switching currents through vias connecting pwr / gnd
to decaps /
comps - if you like). So the real evil to fight is SSN - or, in other words,
get your power supply
decoupled correctly. For this purpose we recently announced SQ Power Plane
Designer,
it's a DESIGN approach (vs post-layout verification) to get decoupling
right.
  - Heiko
At 10:19 AM 10/3/00 -0600, Ken Cantrell wrote:
>Donald,
>Correct me if I'm wrong (Jim), but SQuest, or any of the other vendors
other
>than Innoveda(Quiet Ext), only do a differential mode emissions analysis.
>This means that you are not able to analyze the Vcm created between the
>board and the cable(s), where most of your emissions issues come from.
>Don't get me wrong, I'm not pro-Innoveda either, I'm just a user. There
are
>issues with all of the packages. Innoveda XTK is antiquated and hard to
>use, plus you have to buy XTK to support Quiet and AC/Grade. They should
>have an XTK lite so that the user has a choice, or make Quiet and AC/Grade
>stand alone. SQuest, HyperLynx, and ICX are more user friendly, but don't
>do common mode. HyperLynx (PADS and Innoveda merged, so HyperLynx is under
>the Innoveda banner now), deserves special note. If you are not designing
>chips, just doing boards, it is the most user friendly and intuitive tool
>out there, and it will do 90% of what you need to do at about 10% of the
>cost. If you are in a multiple product line, manufacturing driven
>situation, and are using Cadence, SQuest has a lot of elements that will
>make your life easier. They make the most highly integrated (with CAD,
Mfg,
>and design)package. I also like the agressive pricing that Cadence started
>about a year ago. They give you a lot of bang for the buck. I haven't had
>the chance to review Mentor ICX yet, hopefully later this month. I've had
>problems just getting the package in, both in Seattle and Springs. They
>seem to be responsive on the phone or e-mail, but there is a disconnect
>there somewhere. I have reviewed their FPGA sim pak, Advantage, and it is
>very good. Detailed, but easy to use. I'm hoping their SI pak is as good.
>User to user, Donald, the EDA industry is extremely competitive right now.
>Each vendor leap-frogs the other just about every couple of months on
>feature sets. I used to go for getting everything from one vendor, but now
>I'm mixing and matching, typically doing the one year lease instead of the
>lifetime buy.
>Ken
>Sim Manager
>SRC Computers
>
>-----Original Message-----
>From: owner-si-list@silab.eng.sun.com
>[mailto:owner-si-list@silab.eng.sun.com]On Behalf Of Jim Freeman
>Sent: Monday, October 02, 2000 7:53 PM
>To: Donald Telian
>Cc: May, John; 'si-list@silab.eng.sun.com'
>Subject: Re: [SI-LIST] : FW: Spectraquest Vs. XTK/XNS
>
>
>
>The problem is that the Hspice models are using the M format.
>
>Jim Freeman
>
>
>Donald Telian wrote:
>
> > John,
> >
> > Answers for SPECCTRAQuest are below.
> >
> > Thanks for asking,
> > Donald T.
> > CADENCE
> >
> > At 01:48 PM 9/25/00 -0400, May, John wrote:
> > >
> > >
> > >> -----Original Message-----
> > >> From: May, John
> > >> Sent: Monday, September 25, 2000 1:20 PM
> > >> To: 'si-list@silba.eng.sun.com'
> > >> Subject: Spectraquest Vs. XTK/XNS
> > >>
> > >> Hi all - My group is looking into purchasing one of these tool suites
>for
> > >> SI analysis. I'm wondering what the tradeoffs and limitations of each
>are.
> > >> For instance:
> > >>
> > >> 1) Can botth suites handle HSPICE models in a mixed environment with
>IBIS
> > >> models?
> > >>
> >
> > SPECCTRAQuest uses an optimized spice engine for analysis. As such, all
> > types of spice models can be used with the exception of transistor-based
> > models (M elements). Naturally, IBIS models can be used as well. If
you
> > want to use both IBIS and transistor-level IO models, we have a netlist
> > converter that will translate our proprietary spice netlist (extracted
>from
> > PCB layouts or topology drawings) into a variety of other spice formats.
> >
> > >> 2) Do either of the tools have trouble with differential inputs(high
>and
> > >> low inputs used with a differential receiver)?
> > >>
> >
> > SPECCTRAQuest has support for differential drivers and receivers.
> >
> > >> 3) Connector stitching: How easy is it to use these tools for going
> > >> through connectors to model paths that traverse multiple modules?
> > >>
> >
> > It is quite simple to join multiple board layout files together in
> > SPECCTRAQuest for simulation. And that includes package layout (.mcm)
> > files as well. A variety of connector or cable models can be easily
>placed
> > between the boards. The simplest being RLC or RLGC representations, but
> > fully-coupled connector models can also be integrated into the
simulation.
> > This normally requires some re-formatting of the data from the connector
> > vendor, but it is not too hard to do assuming you understand how to
build
> > and call spice subcircuits.
> >
> > >> John
> > >
> > >**** To unsubscribe from si-list or si-list-digest: send e-mail to
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> > >
> > >
> > >
> > Donald Telian
> > Cadence Design Systems
> > phone: 408-944-7791
> > donaldt@cadence.com
> >
> > **** To unsubscribe from si-list or si-list-digest: send e-mail to
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>
>
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>
>
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     Heiko Dudek
     Technical Marketing Manager | High Speed Systems Design & IC Packaging
     Cadence Design Systems | 270 Billerica Road | Chelmsford, MA 01824

     ph: (978) 262-6384
     fx: (978) 446-6798
     email: heikod@cadence.com

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