EMI and EMC

The terms Electromagnetic interference (EMI) and electromagnetic compatibility (EMC) are often used interchangeably when referring to the regulatory testing of electronic components and consumer goods. Any electronic device generates some amount of electromagnetic radiation. Sources of EMI can sometimes be naturally occurring environmental events, such as electrical storms and solar radiation; but more often than not, the EMI source is another electronic device or electrical system.

While EMI can be generated from any electronic device, certain equipment and components – such as cell phones, welders, motors and LED screens – are more likely to create disturbances than others. Because it is rare for electronics to operate in isolation, products are generally engineered to function in the presence of some amount of EMI. This is particularly important in military-grade and avionics equipment, as well as devices requiring superior reliability in all situations. EMC is a measure of a device's ability to operate as intended in its shared operating environment while, at the same time, not affecting the ability of other equipment within the same environment to operate as intended. Evaluating how a device will react when exposed to electromagnetic energy is one component of this, known as immunity (or susceptibility) testing. Measuring the amount of EMI generated by the device’s internal electrical systems – a process known as emissions testing – is another.

Both aspects of EMC are important design and engineering considerations in any system. Failing to properly anticipate the EMC of a device can have a number of negative consequences, including safety risks, product failure and data loss. As a result, a wide range of testing equipment for EMC and EMI has been developed to give engineers a clearer picture of how a device will operate in real-world conditions.An EMI/EMC anechoic chamber represents a substantial investment.

A number of careful considerations must be weighted in an anechoic chamber project. The screened room must be designed to provide an environment free of extraneous signals. The suitable type of RF absorber must be chosen to line the entire inner surface of the shielded room in order to simulate a free-space environment with no reflection from the walls, ceiling, and floor.