Chapter 3

Fundamentals of Electromagnetic Interference

Before beginning our study of electromagnetic interference (EMI) and electromagnetic compatibility (EMC) we need to lay down a few fundamentals. We need to know these things in order to diagnose and eliminate the problems in equipment.

FUNDAMENTAL CAUSES OF EMI

The fundamental causes of EMI problems can be broken into three categories:

1. Fundamental overload

2. Intermodulation

3. Spurious emissions from a transmitter

Fundamental Overload

Fundamental overload is overload of the affected equipment by the transmitter’s fundamental frequency. The overload may be on-channel or off-channel (or channels may not be involved at all!). The susceptible equipment must be able to do two things: ...

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