eEngineer Introduction:  EMI, EMC, RFI
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EMC Regulations affecting the U.S. are provided primarily by the following three agencies:

1. The Federal Communications Commission (FCC)
The FCC regulates the use of all licensed radio and wire communications in the USA. Three sections of the FCC Rules are applicable to non-licensed electronic equipment: Part 15 (RF devices), Part 18 (industrial, scientific, and medical eqpt.), and Part 68. All have sections governing the control of interference. Part 15 generally covers RF Devices capable of emitting by radiation or conduction, any electromagnetic energy in the 10 kHz to 3 GHz frequency range. Measurement techniques may be done in an open area test site. Part 18 refers to devices that use radio waves for industrial, scientific, or medical purposes.

2. The U.S. Department of Defense (DoD)
Most of the Military Standards (MIL-STD) relating to EMI/EMC are more stringent than the FCC limits set for commercial electronic equipment. These generally cover the frequency range of 30 Hz to 40 GHz and measurement techniques require a special shielded room. Tests are required for radiated emissions (RE), conducted emissions (CE), radiated susceptibility (RS), and conducted susceptibility (CS).

3. International Special Committee on Radio Interference (CISPR)
CISPR, a technical committee of the International Electrotechnical Commission (IEC), is considered as part of the international harmonization effort for EMI/EMC. CISPR's primary responsibility is at the higher end of the IEC frequency range, starting at 9 kHz and extending upwards. It prepares standards that offer protection of radio reception from interference sources such as electrical appliances of all types; the electrical supply system; industrial, scientific and electromedical RF; broadcast receivers (radio and TV) and information technology (IT) equipment (ITE). Europe uses the CISPR test limits and the FCC has adopted some of its limits since the U.S is a member of CISPR.

One or more of the following types of EMI/EMC Tests are applicable to commercial and military electronic equipment as determined by the intended application: Conducted Emissions (CE), Radiated Emissions (RE), Conducted Susceptibility (CS), and Radiated Susceptibility (RS). The Emissions Tests (CE & RE) record any undesirable emissions from the test article. This data is plotted against the applicable specification limits. The Susceptibility Tests (CS & RS) determine the test article's ability to operate in the typical operating environment. The test article is exposed to electromagnetic signals at the levels and frequency ranges required by the applicable specification.

This web site offers information which may be used to design, evaluate, and trouble-shoot electronic equipment for EMI, EMC. The site resources include Radio Frequency Interference (RFI) topics, circuit design guidelines; typical EMI/EMC test descriptions, EMI/EMC reference documents; document Search Engine access; and EMI/EMC related links for additional information.


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