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20 High Frequency Electronics

High Frequency Design

USING EDA TOOLS

How to Get the
Most from Today’s
Advanced EDA Tools

By Gary Breed
Editorial Director

T

his article covers
two aspects of

Electronic Design
Automation (EDA) tools
and how they are used.
First, a number of sug­gestions are offered to
help you use these tools
more efficiently and effec­tively. Then we’ll describe

recent efforts by major EDA companies to
make their software easier to use for both
novice users and advanced designers.

EDA tools have become essential in the
design of all electronic circuits and systems. It
is a useful reminder to list the major reasons
why they are so important:

EDA tools use the speed and power of com­puters—Of course, this is obvious. But, it is

still worth remembering that developing
mathematical descriptions of physical phe­nomena is a serious research task, and cap­turing those increasingly complex mathemat­ics is a challenge for software developers.

They use the organizational power of com­puters—Once a project is underway, comput-

ers are an ideal way to store, track, analyze,
print and share the results. Over the past few
years, this part of EDA technology has
improved dramatically.

They capture valuable knowledge of the
technology—First, the results of research are

captured and coded by the EDA development
team. Next, the computations are matched to
the engineering design process through in­house testing and user feedback. Finally, the
successful results of each user become a valu­able part of his or her company’s Intellectual
Property (IP) resources.

One rule to remember

In my 30+ years of experience, I have
heard the following advice many times, given
by the best engineers: Computers don’t design,
engineers do.

This statement does not mean that begin­ners should not rely on EDA tools to create
new designs, or that we shouldn’t trust the
results. After all, the experience of many bril­liant designers is embedded in these tools!

This rule is only meant to remind us of the
classic computer problem of “garbage in =
garbage out.” Even the best software will
sometimes provide unworkable results. The
user simply needs to have either the experi­ence or the supervision to confirm that the
problems are properly set up and that the
results are legitimate.

Here are tutorial-level

recommendations for users

of modern EDA tools, plus

a summary of EDA vendors’

efforts to help new and

experienced users achieve

success with their high

frequency designs

This month’s cover depicts some of the sim­ulations that an EDA user might perform.

From September 2002 High Frequency Electronics

Copyright © 2002, Summit Technical Media, LLC

22 High Frequency Electronics

High Frequency Design

USING EDA TOOLS

EDA usage recommendations

The following series of hints,
reminders and suggestions has been
developed over many years through
the author’s involvement in the RF
and microwave engineering profes­sion. These are not necessarily in a
priority order:

First, understand the problem on
paper—It is hard to perform any

engineering task without an orga­nized approach, and the EDA envi­ronment magnifies errors that arise
from a poorly-conceived problem.
There is an unconscious tendency to
believe what the computer tells you,
especially by others in your design
team who may not be aware that your
work is less well-defined than it
should be.

Use your knowledge first, then add
the knowledge contained in the soft­ware—This is an extension of the

above concept. The standard circuits
available in the EDA tools’ libraries
may be perfectly acceptable for por­tions of many designs, but it is impor­tant to understand when they are
not. This requires in-depth knowl­edge of the tool and its capabilities. I
have heard too many stories about
engineers who simply use what’s
available from the software because
it’s easy, then let someone else fix it.

Keep the documentation current—
This needs several exclamation
points, according to top engineers.
The latest versions of today’s EDA
tools have better built-in data man­agement than earlier releases. But, it
is too easy to discard previous itera­tions after they have been improved.
A disk drive “file trail” is just as
important as your engineering note­book’s “paper trail.” Engineers in
small companies should beware; the
discipline required to maintain good
records is a special challenge, but the
development of valuable intellectual
property requires it.

Use the right tool for the job—This
seems obvious, but in the heat of the
battle to get a project completed, it
may seem convenient to “get close

enough” with a simulation method
that is not up to the task. When EDA
vendors emphasize the need to aug­ment linear and non-linear circuit
theory simulation with electromag­netic analysis, it’s not all sales pitch.
This year’s designs are at higher fre­quencies than last year’s, and EM
analysis is more important than ever
to assure that the effects of physical
size, layout and packaging are taken
into account.

Tend to the design details—This
covers a lot of scenarios, from choos­ing right type of segmentation for an
EM analysis problem, to using the
component model that has the neces­sary accuracy for your application. A
current trend is for full-system simu­lation, where the size of the analysis
problem is extremely large. It is
essential that each part of the system
is executed properly, since it affects
the overall signal chain.

Finally, the pet peeve of more
than a few engineering managers:

Use the optimizer last, not first—
Yes, there has been much research
into optimization algorithms that do
not have false convergence at a “local
minimum.” But, it is still important
for an engineer to be close enough to
the final answer before optimization
to have full confidence that his tools
have delivered the right answer.

There is an exception to this rule
for the exploration of different topolo­gies. For example, an engineer might
want to try out several matching net­works. A small-size problem can be
quickly set up and run through the
optimizer. The results can be com­pared to see which topology provides
the necessary bandwidth, or if a good

match can be obtained using a config­uration with DC continuity for bias­ing. This trial result is then added to
the larger circuit and thoroughly
analyzed before a final optimization.

These recommendations are fun­damental instructions that we all
learned long ago, yet are regularly
forgotten or bypassed under the pres­sure to get the current job finished!

Taming Complexity,
Connecting With Users

The headline on this issue’s cover
refers to the efforts of EDA vendors
to make their tools more accessible.
The work toward making these
increasingly complex tools “easier to
use” focuses in these main areas:
Helping novice users learn to use the
software more quickly; making expe­rienced designers more productive;
and helping design teams share
results and handle large problems.
These issues are at opposite ends of
the user spectrum, but they repre­sent the reality of engineering—get­ting as much done as possible while
remembering to bring the next gener­ation of designers up to speed.

The first area to note is the on­screen user interface. Placing menus,
lists, plots, etc. in logical places on the
screen is both an engineering and
artistic challenge. That challenge
continues with organizing the nested
commands that are required to
access the more detailed functions.
All companies are working on this
issue, each with variations in the
approach. Users should carefully
evaluate how easy it is to navigate
around each vendor’s product.

In the area of help for new engi­neers, some EDA companies offer
“student version” and “free trial” poli­cies. Ten years ago, this would have
been heresy, since many users would
simply rely on the limited-perfor­mance free versions. But those free
versions, while useful for pieces of the
design puzzle, fall far short of han­dling problems of significant size.
However, they give students and

...the EDA environment

magnifies errors that

arise from a poorly-

conceived problem.