RE: [SI-LIST] : Tools for high-speed interconnect design

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From: linda walling (lwalling@uswest.net)
Date: Mon Aug 14 2000 - 10:53:58 PDT


RE: [SI-LIST] : Tools for high-speed interconnect designDear Hassan,

I agree with you that finite element simulation is not
practical by itself for simulating large circuits.
I don't believe that is the intent of HFSS V8. I
believe the correct usage of HFSS V8 would be to extract
parts of circuits that need full-wave simulation, then export
those models into SPICE to incorporate into larger models
that contain the rest of the circuit.

What is meant by Full-Wave Spice is simply that you can take
structures (or parts of structures) that require full-wave 3D
simulation, and export a spice model. These structures can
be quite complex with coupled conductor terminals. They can
have lumped RLC elements contained inside the FEM model. But,
the engineer is still needed to intelligently create the full-circuit
spice model which incorporates the 3D FEM models along with all the
other typical spice models one might need to represent the full circuit.

linda

********************************************************************
Linda Walling
High Frequency Applications Engineer
Southwest Region
********************************************************************
Ansoft's U.S. customer support group for high-frequency products:

Michael Brenneman (CA) 408-261-9095 brenneman@ansoft.com
Markus Kopp (FL) 954-571-0243 kopp@ansoft.com
Liza Ma (CA) 310-375-7126 lma@ansoft.com
David Perry (NH) 603-643-5340 perry@ansoft.com
Richard Remski (TX) 817-516-7133 remski@ansoft.com
Steve Rousselle (CA) 310-937-1684 rousselle@ansoft.com
James Sherman (FL) 727-394-1023 sherman@ansoft.com
John Silvestro (PA) 412-261-3200x127 silvestro@ansoft.com
Linda Walling (NM) 505-828-2103 walling@ansoft.com

***************************************************************
Ansoft's customer support for installation issues:
Louis Reash (PA), 412-261-3200x165 louis@ansoft.com

********************************************************************
Check out Ansoft's WWW site at http://www.ansoft.com for product
information, technical support, employment opportunities, etc.
********************************************************************

Haved you donated food today to a hungry person?
http://www.thehungersite.com/

  -----Original Message-----
  From: Hassan Ali [mailto:hali@nortelnetworks.com]
  Sent: Monday, August 14, 2000 10:33 AM
  To: linda walling; Charles Grasso; Ray Anderson; si-list
  Subject: RE: [SI-LIST] : Tools for high-speed interconnect design

  Linda,

  Thanks for your response.

  For the benefit of the SI-list users it would be very appreciated if
you
could elaborate further on what you (Ansoft) mean by a "full-wave spice
tool". I personally take it to be a tool that is capable of performing
electronic circuit simulation using a full-wave approach i.e. a method
which
makes no assumptions about the nature and propagation of electromagnetic
field in the problem of interest. For example, it doesn't assume that
the
field is quasi-TEM (mostly in transverse direction and negligible axial
component). And that is exactly where I have a problem comprehending.

  In my opinion, to create a meaningful "full-wave spice" is not
practical.
Take for example a simple electronic circuit comprising of a voltage
source
and a one-inch of a microstrip line terminated with a 50-ohm resistor to
ground. To perform a full-wave simulation of that circuit (say with
Ansoft's
favourite Finite Element Method) you need to capture the material and
exact
geometry of the microstrip line and the resistor, and represent the
voltage
source vectorially (its magnitude and polarisation). Using FEM (or any
other
full-wave electromagnetic field solution technique), you will have to
discretize the geometry into smaller elements as the method dictates and
do
a time-domain solution. This solution process is practically impossible
with
thousands of circuits in a typical printed circuit board with thousands
of
components of various sizes and material compositions. The problem is
exacerbated by the presence of active components with non-linear
behaviour.
(Most electromagnetic field solution tools assume linearity in many
aspects). That's why I think it is virtually impossible (at least in the
next while) to have a true full-wave electronic circuit simulation tool.

  The idea that was floating around in academic circles about 5 years
ago
(when I last checked), was to find a way of formulating the problem in
such
away that the sections of the problem that lend itself well to
SPICE-like
solution (e.g. parts that have non-linear I/O devices) are formulated
using
SPICE-like techniques, and those sections that need 3D electromagnetic
field
solution (e.g. transmission lines, 3D vias, 3D packages) are handled
with 3D
electromagnetic field solution techniques. A mechanism were to be
created
for the two formulations to implicitly (internally) exchange inputs and
outputs and give rise to a single, unified matrix equation to be solved.
But
even that approach is far from being called a full-wave solution!

  I'd really appreciate knowing more about this matter especially new
developments in the last five years.

  Thanks.

  Hassan.

    -----Original Message-----
    From: linda walling [mailto:lwalling@uswest.net]
    Sent: Friday, August 11, 2000 3:52 PM
    To: Ali, Hassan [KAN:0G15:EXCH]; Charles Grasso; Ray Anderson;
si-list
    Subject: RE: [SI-LIST] : Tools for high-speed interconnect design

    Hassan, Charles, & All,

    HFSS V8 will have a number of enhancements that make it a full-wave
spice tool.
    The enhancements that will most directly focus on SI applications
    include Modal-to-modal transformations, which enable a structure to
have
multiple
    coupled conductors at the ports (or terminals), Spice model export
(to
Maxwell Spice,
    PSPICE and HSPICE), lumped RLC elements,
    and interpolative discrete sweeps, which will allow extremely large
problems to run
    faster and smaller and allow for very accurate emissions testing.

    I am not sure when V8 will be released - I believe the scheduled
date is
around the end of
    the year, but it has not been announced yet.

    linda

    ********************************************************************
    Linda Walling
    High Frequency Applications Engineer
    Southwest Region
    ********************************************************************
    Ansoft's U.S. customer support group for high-frequency products:

    Michael Brenneman (CA) 408-261-9095 brenneman@ansoft.com
    Markus Kopp (FL) 954-571-0243 kopp@ansoft.com
    Liza Ma (CA) 310-375-7126 lma@ansoft.com
    David Perry (NH) 603-643-5340 perry@ansoft.com
    Richard Remski (TX) 817-516-7133 remski@ansoft.com
    Steve Rousselle (CA) 310-937-1684 rousselle@ansoft.com
    James Sherman (FL) 727-394-1023 sherman@ansoft.com
    John Silvestro (PA) 412-261-3200x127 silvestro@ansoft.com
    Linda Walling (NM) 505-828-2103 walling@ansoft.com

    ***************************************************************
    Ansoft's customer support for installation issues:
    Louis Reash (PA), 412-261-3200x165 louis@ansoft.com

    ********************************************************************
    Check out Ansoft's WWW site at http://www.ansoft.com for product
    information, technical support, employment opportunities, etc.
    ********************************************************************

    Haved you donated food today to a hungry person?
http://www.thehungersite.com/

      -----Original Message-----
      From: Hassan Ali [mailto:hali@nortelnetworks.com]
      Sent: Friday, August 11, 2000 1:33 PM
      To: Charles Grasso; Ray Anderson; si-list
      Cc: lwalling
      Subject: RE: [SI-LIST] : Tools for high-speed interconnect design

      Charles,

      "Modes to nodes" thing won't give you a SPICE model from the way I
understood that concept from the Ansoft people and from my own past
research. I understood it to be a technique of coupling (interfacing)
the
traditional SPICE-based electrical circuit (nodal) simulation with 3D EM
field (modal) simulation. In this technique the models of the
interconnects
are implicitly generated and utilised. The generated interconnect models
would mean nothing to external SPICE-based simulators. Ansoft people may
correct me if I'm wrong.

      And BTW, is Ansoft HFSS 8 already available?

      Regards.

      Hassan.

      -----Original Message-----
      From: Charles Grasso [mailto:chasgra@msn.com]
      Sent: Friday, August 11, 2000 2:28 PM
      To: Ray Anderson; si-list
      Cc: lwalling
      Subject: Re: [SI-LIST] : Tools for high-speed interconnect design

      Hello,

      Ansofts HFSS version 8 translates modes to nodes , in other words
you
can
      get
      a fully coulped SPICE model of the device of interest to a very
high
      bandwidth.

      Thank you.

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