Our
last meeting was
Can
Just Anyone Understand Electromagnetic Fields?
Download the presentation here
Pictures
from the meeting
Presenter:
Professor Edward Kuester Department of Electrical and Computer
Engineering, University
of Colorado at Boulder
Date :
September 22 2000
Time :
1:30 pm - 4:30pm
Location:
National Center for Atmospheric Research Mesa Lab
and Fleischmann Building, 1850 Table Mesa Drive,
Boulder CO. Look for the Main Seminar Room. Directions
What we
saw: This talk was part seminar,
part tutorial, part give-and-take with the
audience. Historically, an electrical engineer's
education provided a solid background in circuit
analysis, and touched somewhat on other subjects
(like computers, power conversion,
electromagnetics, etc.). Much of what a working
engineer was called upon to do could be
accomplished by building on this foundation of
circuit theory. As our use of the frequency
spectrum pushes ever higher (1 GHz computer
processors, cell phones at microwave band, and so
on), designs can no longer be made purely on the
basis of classical circuit concepts. Professor
Edward Kuester tells students in the beginning
electromagnetics class that EM fields are really
the basis of everything we do outside the quantum
level in electrical engineering. Does this mean
that you have to be an expert in EM to design
anything these days? Or can the impact of
Maxwell's equations be understood in a simpler
way, using ideas already familiar from electric
circuits?
Twenty-eight
intrepid folks turned up to see Professor Edward
Kuester emphatically gave a "yes"
answer to the second question. He looked at
several issues that arise in practical
applications (use of computers to calculate
fields, the effect of EM fields between
neighboring circuits, and others) and tries to
show how readily understood techniques of circuit
analysis can be used to deal with these problems.
Professor Kuester
started his talk right at the beginning -
Maxwells Equations. He briefly reviewed the four
sets of equations and showed that although most
engineers are concerned with approximating
Maxwells Equations, they are themselves an
approximation of Quantum Electrodynamics. We then
reviewed some of the basics of field theory as a
reminder and as a nice lead into how, by keeping
element size small with respect to a wavelength,
lumped-circuit theory can be obtained from EM
fields in the low frequency limit. Professor
Kuester then travelled back in time to 1850 and
introduced Lord Kelvin who developed the
telegraphers equations, an analytical connection
between circuits and fields. He then posed the
question - Can we go the other way. That is from
Fields to Circuits? The answer was yes by taking
the finite difference approximation for Maxwells
curl equations and do it for all three space
directions. A circuit was then shown that
approximated the field description with the
advantage that the circuit can be described in
Spice and used as a computing tool. Professor
Kuester then discussed the numerical computation
of fields with some of the advantages and
drawbacks. Keeping to the focus of talk,
Professor Kuester then analysed printed circuit
traces and described a way of making a
"real" circuit model that models the
actual currents on the traces rather than fields
that we have little interest in. That is when we
learned about the PEEC or Partial Element
Equivalent Circuit Method. Professor Kuester then
walked us through the connection between fields
and circuits and then really stirred up the pot
with a discussion on Partial Inductance. Finally
at the end of the talk, the question -
Understanding?.We learned that equations for EM
fields can be reduced to equivalent circuit
equations. Professor Edward Kuester opened up the
discussion with the audience and fielded
questions for about an hour afterwards
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