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Electromagnetic Interference

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Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction.Shortly, EMI is an electronic noise that disturbs the cable signal and reduces signal integrity.

What is EMC?
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What is EMC?


EMC(Electro Magnetic Compatibility),refers to the ability of a device or system to comply with the requirements in its electromagnetic environment without causing unacceptable electromagnetic interference to any device in its environment. Therefore, EMC includes two requirements: on the one hand, the electromagnetic interference generated by the equipment in the normal operation of the environment cannot exceed a certain limit; on the other hand, the appliance should have a certain resistance of the electromagnetic interference in the environment, namely, electromagnetic sensitivity.


A variety of operating power equipments associate and affect each other by the electromagnetic conduction, electromagnetic induction and electromagnetic radiation, which under certain conditions will do harm to the running equipment and personnel. The purpose of electromagnetic compatibility is to ensure that the electrical components or devices in the electromagnetic environment can have the ability to work properly, and signal and interference can coexist without compromising the information contained in the signal.


Electromagnetic Compatibility Design

In order to get a good electromagnetic compatibility, you need to pay special attention to the electromagnetic compatibility design. Electromagnetic compatibility design generally includes the following aspects:


Ground Design

Many electromagnetic interference problems are generated by the ground, because the ground potential is the reference potential of the entire circuit work. If the ground is not properly designed, ground potential is then instable, which will lead to circuit failure. The purpose of the ground design is to ensure that the ground potential is as stable as possible, thus eliminating the interference phenomenon.


Circuit Board Design

Whether the equipment generates electromagnetic interference or is disturbed by external interference, or the circuit is interfered with each other, the circuit board is the core of the problem. Therefore, designing the circuit board is of great significance to ensure the electromagnetic compatibility of the equipment. The purpose of the circuit board design is to reduce the electromagnetic radiation on circuit board and the sensitivity of interference to the outside world, reducing the interaction between the circuits.


Filter Design

For any device, filtering is one of the key technologies to solve electromagnetic interference. Because the wires in the device are highly efficient to receive and radiate the antenna, most of the radiation generated by the device is achieved through various wires, and the external disturbances are often first received by the wires and then tied into the equipment. The purpose of filtering is to eliminate these interference signals on the wires, to prevent the wire to receive the interference signal into the circuit.


Shielding Design

For most of the equipment, shielding is necessary. Especially with the increasing frequency of circuit work, simply relying on circuit board design cannot meet the requirements of electromagnetic compatibility standards. There are many differences between chassis mask design and the traditional structural design. Generally if the electromagnetic shielding is not taken into account in structural design, it is difficult to add the shield effect to the chassis. Therefore, for modern electronic product design, the shielding must be considered from the beginning.


Statement: This post is only the personal view of the author and does not represent the opinions of

Andreas Jonsson

Very valuable!

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