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

From: Hassan Ali ([email protected])
Date: Mon Aug 14 2000 - 09:32:35 PDT

Linda,

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!

developments in the last five years.

Thanks.

Hassan.

-----Original Message-----
From: linda walling [mailto:[email protected]]
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 [email protected]
Markus Kopp (FL) 954-571-0243 [email protected]
Liza Ma (CA) 310-375-7126 [email protected]
David Perry (NH) 603-643-5340 [email protected]
Richard Remski (TX) 817-516-7133 [email protected]
Steve Rousselle (CA) 310-937-1684 [email protected]
James Sherman (FL) 727-394-1023 [email protected]
John Silvestro (PA) 412-261-3200x127 [email protected]
Linda Walling (NM) 505-828-2103 [email protected]

***************************************************************
Ansoft's customer support for installation issues:
Louis Reash (PA), 412-261-3200x165 [email protected]

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

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-----Original Message-----
From: Hassan Ali [mailto:[email protected]]
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:[email protected] <mailto:[email protected]> ]
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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