In antenna theory, the electromagnetic field around an antenna is divided into two main regions: the near field and the far field.
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Near Field Region: This is the area close to the antenna, typically within a distance of less than one wavelength from the antenna. In this region, the electric and magnetic fields do not propagate as waves but instead exhibit reactive characteristics. The near field is characterized by a complex interaction of field components, and it is used primarily for applications that require close interaction with the antenna. Wireless applications using the near field include Near Field Communication (NFC), RFID (Radio-Frequency Identification) systems, and certain types of medical devices that rely on short-range wireless power transfer.
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Far Field Region: Located at a distance greater than a few wavelengths from the antenna, the far field region is where the radiated electromagnetic waves propagate as plane waves. The effects of the antenna's radiation pattern become dominant in this area, making it suitable for long-range communication. Applications relying on far field wave propagation include traditional radio broadcasting, cellular communications, satellite communications, and Wi-Fi.
In summary, the near field supports short-range interactive applications while the far field enables long-distance communication.