EMI
Introduction
Electromagnetic Interference (EMI), also known as radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit through electromagnetic induction, electrostatic coupling, or conduction. The disturbance may degrade the performance of the circuit or even stop it from functioning. In the case of a data path, these effects can range from an increase in error rate to a total loss of the data.
Sources of EMI
EMI can originate from a variety of sources. These sources can be broadly categorized into two types: natural and man-made. Natural sources of EMI include solar flares, lightning, and auroras. Man-made sources include electrical and electronic devices, power lines, and transmitters.
Natural Sources
Natural sources of EMI are typically less controllable than man-made sources. Solar flares, for instance, can produce high levels of radio frequency radiation that can interfere with communication systems and power grids. Lightning strikes can generate EMI by creating large electromagnetic fields due to the rapid movement of large amounts of electrical charge.
Man-made Sources
Man-made sources of EMI are numerous and varied, ranging from devices as simple as a hair dryer to complex systems like a digital computer. These devices can generate EMI through the switching of electrical currents, the operation of electronic circuits, or the transmission of radio waves.
Effects of EMI
The effects of EMI can range from minor annoyances to serious disruptions. In a home setting, EMI can cause static on a television screen or noise on a radio. In a more critical setting, such as a hospital or an aircraft, EMI can interfere with the operation of life-supporting devices or navigation systems, respectively.
EMI Control and Mitigation
There are several strategies for controlling and mitigating EMI. These include EMI filtering, shielding, grounding, and the use of EMI cancellation techniques.
EMI Filtering
EMI filtering is a technique that is used to suppress the unwanted signals that are generated by a device. This is typically achieved by using a combination of passive electronic components such as capacitors, inductors, and resistors to form a filter circuit that can attenuate the unwanted signals.
Shielding
Shielding is a technique that is used to prevent the EMI from reaching the sensitive parts of an electronic device. This is typically achieved by enclosing the device in a conductive material that can absorb the EMI and dissipate it as heat.
Grounding
Grounding is a technique that is used to provide a path for the EMI to flow into the earth, thereby preventing it from affecting the operation of the device. This is typically achieved by connecting the device to a grounding conductor that is in turn connected to the earth.
EMI Cancellation
EMI cancellation is a technique that is used to reduce the EMI by generating a signal that is equal in magnitude but opposite in phase to the EMI. This results in the two signals cancelling each other out.
EMI Standards and Regulations
There are several international standards and regulations that govern the emission and immunity of devices to EMI. These include the International Electrotechnical Commission (IEC) standards, the European Union's Electromagnetic Compatibility (EMC) Directive, and the United States' Federal Communications Commission (FCC) regulations.