RE: [SI-LIST] : May 9th Presentation: "Radiation from Edge Effects in Printed Circuit Boards (PCBs)"

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From: Mary (mary@advocate.net)
Date: Fri May 05 2000 - 14:49:47 PDT


This is a fascinating discussion group. My background is in the
microwave circuits area, so I can't be sure how much of what is
posted here is correct. However, I have come to the conclusion
that most of the information posted concerning the 20H rule was
bogus.

Based on what I know about microstrip patch antennas, it seems
unintuitive to me that a small change in the size of a power
plane would have any significant effect on the radiation from a
power-ground plane pair. (And I am fairly certain that the
resonant frequencies cannot be shifted by a factor of 2 to 3.)
I tried to find out more about this, but there is virtually nothing
in the literature about the 20H rule.

I will be unable to attend the SCV EMC meeting, but I hope
that someone will provide an overview of their presentation here
or on the web (particularly if they discuss the 20H rule).

Mary

-----Original Message-----
From: owner-si-list@silab.eng.sun.com
[mailto:owner-si-list@silab.eng.sun.com]On Behalf Of Hans Mellberg
Sent: Friday, May 05, 2000 9:23 AM
To: si-list@silab.eng.sun.com; emc-pstc@ieee.org
Subject: [SI-LIST] : May 9th Presentation: "Radiation from Edge Effects
in Printed Circuit Boards (PCBs)"

Bring a colleague
Please Post
Free Admission

The Santa Clara Valley Chapter of the IEEE EMC Society
is presenting on May 9th, at:

Silicon Graphic's Cafe Iris
Building 5, 2025 Stierling Court
Mountain View CA

Dinner: 5:30-7:30pm
Presentation: 7:30-9:00pm

May IEEE EMC Chapter Meeting Presentation

Presenters: Dr. Zorica Pantic-Tanner, Director, School
of Engineering, San Francisco State University,

Franz Gisin, EMC Manager, Nortel Networks

Title: "Radiation from Edge Effects in Printed Circuit
Boards (PCBs)"

Details
---------
Propagating electromagnetic fields are generated
whenever charge is accelerated. The polarization,
direction, and mode of these fields are dependent on
the structure that contains the accelerated charge.
In printed circuit boards (PCBs), they include
radiation from unwanted parasitic modes associated
with tangential (planar) structures such as traces
routed on outside layers (microstrip), and traces
routed between ground and power planes (striplines).
Structures normal to the ground and power planes such
as vias also generate surface waves in the dielectric
strata directly adjacent to the outside ground/power
planes, and radial TEM waves between internal ground
and power planes. As these fields propagate outward,
they encounter the edge of the PCB. The edge presents
a boundary discontinuity, and a portion of the energy
in the propagating fields is reflected back into the
PCB structure, a portion radiates outward from the
edges of the PCB, and, depending on the angle of
incidence, a portion also propagates tangentially
around the edge of the PCB, exciting natural resonant
modes within the PCB that also contribute to the total
radiated energy.

Using analytical modeling tools such as the Finite
Difference Time Domain (FDTD) method and Fast Fourier
Transform (FFT) algorithms, one can isolate the time
and frequency domain components each of these various
propagating modes have on the total radiation from PCB
edges, and evaluate the effectiveness of such popular
edge radiation minimization techniques as adding a row
of closely spaced vias that short together all the
ground planes within a multi-layer PCB (fences), and
pulling back the power planes from the edges.

The presentation includes a brief theoretical analysis
of each of the different kinds of propagating modes,
the effect the PCB edge has on each mode, and how
fences and pulled-back power planes affect the total
radiation efficiency from the PCB edge. The
presentation also includes several time-domain
animations that enhance the physical understanding of
how these propagating modes produce radiation along
PCB edges.

Dr. Zorica Pantic-Tanner is Director of the SFSU
School of Engineering, and Director of the SFSU Center
for Applied Electromagnetics, a research facility that
provides resources for theoretical and experimental
studies in applied electromagnetics. She received her
B.S., M.S., and Ph.D. degrees in Electrical
Engineering from the University of Nish in 1975, 1978,
and 1982, respectively. After graduating she became
an Assistant Professor and then Associate Professor in
the Department of Electronic Engineering at the
University of Nish. In 1984 she was awarded a
Fulbright Scholarship for postdoctoral research in the
area of Applied Electromagnetics with the
Electromagnetics & Communications Lab of the
University of Illinois at Urbana-Champaign. In 1989
she joined the School of Engineering at San Francisco
State University. Dr. Pantic-Tanner's research and
teaching interests are in the areas of Electromagnetic
Field Theory, Applied Electromagnetics and
Electromagnetic Compatibility (EMC). She has
published over 50 conference and journal papers in
these areas. Dr. Pantic-Tanner is Chair of the Santa
Clara Valley Chapter of the IEEE EMC Society, a member
of the IEEE EMC Society Education Committee, and
Vice-Chair of the IEEE EMC Society Technical Committee
TC-9 on Computational Electromagnetics. Under the
IEEE EMC Society sponsorship, she has also developed
and taught several EMC courses.

Franz Gisin is EMC Manager at Nortel Networks. He
received his B.S. degree in electrical engineering
from the University of Idaho in 1972, and his M.S.
degree in Applied Mathematics from the University of
Santa Clara in 1986. Franz has been active in the EMC
community for over 25 years, and has published
numerous papers ranging from measurement uncertainties
associated with 1/R extrapolation on OATS to
mechanisms of common mode radiation from PCBs with
attached cables. He is a past EMC Society
Distinguished Lecturer and a past member of the EMC
Society Board of Directors. Currently he is steering
committee chair of the 2004 IEEE International
Symposium on Electromagnetic Compatibility. He also
teaches electromagnetics (on a part-time basis) at
SFSU.

=====
Best Regards
Hans Mellberg
EMC Consultant

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