The most common type of EMI occurs in the radio frequency (RF) range of the electromagnetic (EM) spectrum, from 104 to 1012 Hertz. This energy can be radiated by computer circuits, radio transmitters, fluorescent lamps, electric motors, overhead power lines, lightning, and many other sources.
Device failures caused by interference—or “noise”—from electromagnetic energy are increasing due to the growing number of products that contain sensitive electronic components. The smaller size and faster operating speeds of these components make it more difficult to manage the EM pollution they create. Increased device frequencies (applications over 10 GHz are now common) cause proportionally decreased wavelengths that can penetrate very small openings in housings and containers.
Increasingly strict regulations address a product’s emissions. At the same time, a product’s immunity to external EMI determines its commercial success or failure. To comply with regulations on both emissions and immunity (or susceptibility), designers and manufacturers integrate shielding in their product designs through a working knowledge of EMI behavior and shielding techniques.