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Basics of EMI Shielding

• Publicado por John Scott 1 de dezembro de 2023 - Arquivado em Negócios - #EMI Shielding  - 4 visualizações

  EMI Shielding is defined as a process that prevents the leakage of powerful electromagnetic fields that can interfere with sensitive devices and signals. They can be installed to isolate the source of the electromagnetic field or as an enclosure for the item that requires protection. Electromagnetic interference, often known as rfi interference, is an issue for most electronics since it can reduce circuit performance. Electronic devices work with modest voltages and currents that can be quickly disrupted by an electromagnetic field.

   

  Electromagnetic Interference (EMI)

   

  As we are familiar, electromagnetic interference is the coupling of signals from one system to another impacting the electronic device. An EMI generally consists of three parts: the source, the path, and the receiver. 

   

  The source is the external circuit or phenomenon responsible for the disturbance, which can be either natural or man-made. The receiver is the sensitive signal or equipment whose output signal is altered by interference. The path is where signal coupling takes place, and it can go through the following four different modes:

   

  • Capacitive EMI: This arises when two conductors in a system are very close to each other, often less than a wavelength apart. This little gap generates parasitic capacitance, which stores and transfers electric charge via charge differentials. The electric fields released by the conductors cause charge differentials.

   

  • Conducted EMI: It occurs when there is a conductive path between two circuits through which stray signals or currents can travel. Conducted EMI is either common-mode or differential-mode. Stray current from the two systems travels in the same direction through a grounding link that serves as a common return channel in the common mode. In the differential mode, the unwanted current flows in opposing directions across the two systems via the power supply lines and is independent of the ground.

   

  • Magnetic EMI: This is the same as capacitive coupling, which happens at short distances. Through electromagnetic induction, a current is created across another conductor to send a signal. When the current in the first conductor varies or oscillates, this is feasible.

   

  • Radiated EMI: This travels via the open area between the source and the receiver. An electromagnetic wave is emitted by a source and is unintentionally sent to a circuit. Cables and circuit board traces can function as antennae, transmitting and receiving an external electromagnetic wave.

   

  Importance of EMI Shielding

   

  People are aware of the negative impacts of EMI and also know the significance of shielding in the electronic sector. EMI shielding attempts to isolate a device's energy so that it does not harm what is around it and prevents external energy from attacking. Every new electronic equipment emits some electromagnetic radiation and has no EMI resistance. Some of the impacts of EMI are listed below.

   

  • Signals received by communication devices that are jammed or distorted
  • Electricity outages, fluctuations in electricity, and electrical fast transitions (EFT).
  • Total failure or damage to an electrical circuit.
  • Electronic system life and performance are reduced.
  • Burns and electric shock.
  • Possible ignition of the source.

   

  With a better understanding of the nature of rfi interference, it is evident that it can have a variety of effects on its surroundings. It can have an impact on electronics that are in direct touch (conducted EMI), in close vicinity without direct contact (capacitive and magnetic EMI), and even at long distances (radiated EMI). The increased use of electronics for data processing and communication, along with other disturbances caused by electrical transmission and distribution systems and natural phenomena such as lightning strikes and solar flares, contributes significantly to the pollution of the electromagnetic wave spectrum as the information age progresses.