EMC

The longer one waits to implement Electromagnetic Environmental Effects (EEE) engineering during a system’s or unit’s development cycle, the faster the opportunities for optimization disappear, and the higher the cost to implement corrections become.

Electromagnetic Environmental Effects (EEE)

EEE encompasses all electromagnetic disciplines, electromagnetic compatibility; electromagnetic interference, electromagnetic vulnerability; electromagnetic pulse; electronic protection; hazards of electromagnetic radiation to personnel, ordnances, and volatile materials; and natural phenomena effects of lightning (direct and indirect effects) and p-static. MIL-STD-464, Electromagnetic Environmental Effects, Requirements for Systems calls out various test documents, environment definitions, and operational considerations for qualification of electronic equipment for military applications. The European Community has adopted the EN

Electromagnetic Compatibility (EMC)

Electromagnetic Compatibility is the ability of equipment to operate in its intended environment at its designed functionality without causing electromagnetic interference. EMC can be divided into four categories:

Radiated Emissions (from the unit or system)

Radiated Immunity (of the unit or system)

Conducted Emissions (from the unit or system)

Conducted Immunity (of the unit or system)

The military community uses the term susceptibility instead of immunity. Designing equipment and/or systems for EMC can be broken down into four general areas:

Grounding

Shielding

Filtering

Signal Waveform Control (sometimes referred to as signal fidelity or signal integrity)

Considerations in all four areas are required to pass governmental requirements such as Military, Federal Communications Commission, European Community, and FDA for example. The governmental requirements are imposed on electrical/electronic equipment for public safety, to maintain the communication systems through the country in case of emergencies and provide a somewhat stable electromagnetic environment for introductions of new units or systems.

Electromagnetic Interference (EMI)

Electromagnetic Interference is an electrical disturbance from either natural phenomena or other electrical/electronic devices or systems thus causing an undesired response from the victim unit or system. EMI is considered the opposite of EMC. Radiated and Conducted Immunity testing is performed to determine the ability of a unit or system to resist EMI. Radio Frequency Interference (RFI) is a form of EMI where energy from an intentional transmitter (such as a radio tower) causes a unit or system to malfunction. Amateur radio operators sometime run into these issues. Adjacent channel, spurious emission, and harmonic emissions are some of the issues found when operating a number of systems with intentional transmitters and/or receivers in a confined area. An example of which is aircraft which can have HF, UHF, VHF, IFF, TACAN, INS, GPS, MLS, VOR, Glideslope, DME and many other systems all on the same platform. Ships, trains, building and even cars are becoming more populated with transmitter and/or receiver systems every day. Cars have your typical radio, cell phone, LoJack, GPS, and sometimes a UHF or VHF radio to name a few. Many buildings have their roof tops rented or sold to companies for microwave towers, cell phone towers, and television towers to name a few. EMI comes from all types or sources and can interfere with all types of electrical/electronic equipment.