Antenna (electromagnetism)

Article By:

Baird, Christopher S. Department of Chemistry and Physics, West Texas A&M University, Canyon, Texas.

Last reviewed:March 2022

DOI:https://doi.org/10.1036/1097-8542.038400

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• Antenna (electromagnetism), published August 2019:Download PDF Get Adobe Acrobat Reader

A conductor whose purpose is to emit and/or receive electromagnetic waves using the bulk oscillations of electric charges within the conductor. The conduction electrons in antennas are free to move throughout the conductor. The electrons form a bulk oscillating electric current in response to applied forces from an electric circuit. As a result, the electromagnetic field surrounding the current also oscillates, forming self-sustaining electromagnetic waves that travel away from the antenna. Because the oscillation of the wave is created by the oscillation of the current in the antenna, the frequency and the waveform of the wave equals the frequency and waveform of the current in the antenna. This fact makes antennas very useful in transmitting and receiving information using electromagnetic waves (see illustration). Due to the symmetry between how oscillating currents create electromagnetic waves and how electromagnetic waves create oscillating currents, the same antenna can be used to both generate and capture electromagnetic waves. This makes an antenna very useful in two-way wireless communications, where the same antenna can quickly switch between transmitting and receiving modes. See also: Electric charge; Electrical circuit; Electric current; Electrical conductor; Electromagnetic field; Electromagnetic radiation; Electromagnetic wave; Electron; Frequency (wave motion); Oscillation; Wave motion

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