Engineering Specification
ES-3U5T-1B257-AA
EMC Design Guide for Printed Circuit Boards
Frame 9 of 78
Rev. A
10/01/2002
Printed copies are uncontrolled
PART II: GENERAL EMC
2. EMC OVERVIEW
The application of electronic components and devices is increasing in all area of consumer
products as well as within the industrial production environment. This provides an
electromagnetic environment with an increasing overall noise floor due to digital control
applications in virtually any niche of daily life and an ever increasing demand on mobile
telecommunications facilities.
The noise margin observations in the early 90's have revealed an increase of approximately
3 dB per year poses an increasing threat onto the immunity margins of the electronic
components. In contrast to the aggression, the immunity margin is falling due to the drastic
increase in the complexity of the components, calling for a reduction in power consumption
in order to control thermal effects for instance. The attempt of controlling costs also leads
towards a trend of replacing solid metal housings with plastics or composites, which decrease
shielding capabilities.
In summary, the trend in Electronics' applications, a raise of a harsh electromagnetic ambient
has to be noticed with a loss of safety margins, making applications more susceptible to
electromagnetic interference and calling for regulations to keep the problems arising under
control.
2.1. The Elements
Electromagnetic radiation due to the operation of electrical or electronic devices may be
grouped into two types:
·
Intentional Emissions
·
Unintentional Emissions
Examples of the first type are television and radio broadcasting systems, communication
and radar systems, and transmitters for navigational purposes. However, even when
performing properly such equipment may also generate undesired electromagnetic
emissions of the second type. This might interfere with the system itself or the overall
emissions might affect other sensitive equipment nearby. In order to control these kind of
effects frequency management is necessary in the first place due to the fact that a certain
part of the emission profile contains valuable information and is intended to be there.
Electronic components provide a frequency band and due to non-linearities in active
devices unintentional harmonics may be created, and modulations might occur. In
general, sources of coherent electromagnetic emission at a given frequency or within a
specified frequency band are intentional transmitters, but both coherent as well as non-
coherent emission bear the potential for electromagnetic interference problems.
Electromagnetic emissions may thus be divided into:
Summary :
The Elements Electromagnetic radiation due to the operation of electrical or electronic devices may be grouped into two types: · Intentional Emissions · Unintentional Emissions Examples of the first type are television and radio broadcasting systems, communication and radar systems, and transmitters for navigational purposes. In general, sources of coherent electromagnetic emission at a given frequency or within a specified frequency band are intentional transmitters, but both coherent as well as non- coherent emission bear the potential for electromagnetic interference problems.
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