2011 EMC Directory & Design Guide - Interference Technology

design
EMI Sources and Their Most Significant Effects
Electromagnetic Interference Sources and
Their Most Significant Effects
The increasing number of EMI sources is creating greater
challenges for those responsible for maintaining the interoperability
of products and systems
Anthony A. DiBiase
Spec-Hardened Systems
Rochester, New York USA
As the density of the electromagnetic
environment (EME) continues to
increase the concern for its effects
from sources producing EMI also increases.
Advances in technology and the number of
products produced, is having a significant
effect on the efforts aimed at maintaining
the required operation and inter operability
of products and systems used in our society.
These events have added challenges for
those who are responsible for keeping pace
with the effort required in maintaining the
required level of electromagnetic compatibility
(EMC) in these products and systems.
SOURCES
EMI sources both natural and man made
that compose the EME can be categorized
into several primary categories. Some of
these classifications of sources are listed
below.
(1) Ambient EME that is composed of
numerous sources of which the most significant
are:
• Television transmissions both analog and
digital
• Radio AM, FM, and Satellite
• Solar Magnetic Storms which peak on a
eleven year cycle
• Lightning which occurs as a very high
voltage and high current event
• Utility power grid transmission lines
which have high voltage, low current,
and low frequency characteristics. In this
category is also the new technology of
Broadband over Power Lines (BPL) digital
signals.
• Other ambient EME sources include airport
port radar, telecom transmissions,
electrostatic discharge (ESD), and white
noise. Also in this category is the earth’s
magnetic field flux which has a value of
about 500 milligauss.
• Some other major product and system’s
emissions sources include switching
mode power supplies, arc welders, motor
bushes, and electrical contacts
(2) High Powered Electromagnetic Pulse
(HEMP) threats which are intended to disable
electrical and electronic equipment.
These sources are designed to be utilized
by terrorist and military organizations.
Currently existing HEMP devices include
the following:
• Intentional Electromagnetic Interference
(IEMI) source – a high powered pulse
device utilized by combat, sabotage and
terrorist organizations
• High Altitude Nuclear Electromagnetic
Pulse (HNEMP) – produced by the detonation
of a nuclear device high above the
earth’s atmosphere
• High Powered Microwave Weapon (HPM)
– a device utilized by the military as a
combat weapon
• E-Bomb – a HEMP weapon employed by
122 interference technology emc Directory & design guide 2011