EMC Technologies - Independant EMI/EMC Test Laboratory

PRODUCT EMISSIONS - AN OVERVIEW

This page provides an overview of the sources, emission paths and minimisation strategies of electromagnetic interference (EMI) emissions.

Emissions can be divided into two main types:

conducted
radiated

CONDUCTED EMISSIONS can propagate along cables via external ports such as an AC power connection and cause interference to other devices on the same AC power loop. Effects may range from bothersome noise on your stereo to the malfunction of a life support system in a hospital.

RADIATED EMISSIONS can be emitted from all features of a device that may act as antennas. This ranges from circuit board tracks, wiring within a piece of equipment, re-radiation from the enclosure to radiation from resonant cables attached to the equipment.

As with all EMI/EMC problems, the cure begins at the source. For emissions this means reducing the power of potential RF sources in the circuit by applying a number of strategies such as increasing clock and power-switching rise times and providing enveloping ground planes by using multi-layer PCBs. Once you've applied noise reduction techniques at this level, the challenge is to minimise transmission/radiation of the electromagnetic emissions from the enclosure and cables.

CONTENTS

General

Commercial Emissions Limits - The Design Challenge

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