01-08-2012, 04:37 PM
Solving Electromagnetic Coupling Problems by Spatial Component
Placement.
Electromagnetic_Coupling(best).pdf (Size: 624.45 KB / Downloads: 183)
ABSTRACT
More and more demand is being placed
on The Appliance Industry to meet
Global Electromagnetic Compatibility
performance standards. The
sophistication of these appliances with
the use of electronic controls and
switching power supplies increases the
challenge of solving EMC problems.
The most effective way of solving EMC
problems is to intervene at the
interference sources, i.e. to tackle
them at the component placement level.
Several EMC phenomena take place in
electronic circuits, which can be
minimized by using simple placement
rules.
INTRODUCTION
The sophistication of today’s
home appliances with the use of
electronic controls and switching power
supplies increases the challenge of
solving EMC problems. It is a known
fact that the most effective way of
solving EMC problems is to intervene at
the sources, on the printed circuit board
(PCB).
Signal Lines
All input and output power and signal
lines that connect to system cables
should be filtered with: common mode
chokes, differential mode inductors, or
capacitors. [1][3][7]
There must be, at the very least, an LC
filter at the power feed in order to aid in
reducing conducted emissions. These
filters should be placed as near as
possible to the power entry. Power
supplies or power converters will
probably require common-mode and
differential-mode filtering. They are
noisy devices, which can cause both
conducted and radiated problems.
Capacitors
Capacitors are used for various
functions within a PCB, including
minimizing ground bounce, shunting RF
energy, and removing common-mode
and differential-mode RF currents. [1][3][7]
Capacitors are used in one of three
configurations:
Connectors and Interconnect
Use partitioning in the connector
section. Separating reset lines from
clock lines and noisy signals from quiet
signals can significantly suppress noise
emissions. Lower speed signals should
be placed on connector pins that have
longer paths. Ground pins should
surround all single ended 50 Mbps or
higher frequency signals. Place at least
one ground pin beside each noisy signal
and ground pin should be placed next to
sensitive lines like reset lines.