Microwave

A telecommunications tower with a variety of dish antennas for microwave relay links on Frazier Peak, Ventura County, California. The apertures of the dishes are covered by plastic sheets (radomes) to keep out moisture.

Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves (as originally discovered) but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequencies between 300 MHz and 300 GHz, broadly construed.[1][2][3][4][5][6] A more common definition in radio-frequency engineering is the range between 1 and 100 GHz (wavelengths between 30 cm and 3 mm),[2] or between 1 and 3000 GHz (30 cm and 0.1 mm).[7][8] The prefix micro- in microwave is not meant to suggest a wavelength in the micrometer range; rather, it indicates that microwaves are small (having shorter wavelengths), compared to the radio waves used in prior radio technology.

The boundaries between far infrared, terahertz radiation, microwaves, and ultra-high-frequency (UHF) are fairly arbitrary and are used variously between different fields of study. In all cases, microwaves include the entire super high frequency (SHF) band (3 to 30 GHz, or 10 to 1 cm) at minimum. A broader definition includes UHF and extremely high frequency(EHF) (millimeter wave; 30 to 300 GHz) bands as well.

Extremely high frequency is the International Telecommunication Union designation for the band of radio frequencies in the electromagnetic spectrum from 30 to 300 gigahertz (GHz)

Frequencies in the microwave range are often referred to by their IEEE radar band designations: S, C, X, Ku, K, or Ka band, or by similar NATO or EU designations.

Microwaves travel by line-of-sight; unlike lower frequency radio waves, they do not diffract around hills, follow the earth's surface as ground waves, or reflect from the ionosphere, so terrestrial microwave communication links are limited by the visual horizon to about 40 miles (64 km). At the high end of the band, they are absorbed by gases in the atmosphere, limiting practical communication distances to around a kilometer.

Microwaves are widely used in modern technology, for example in point-to-point communication links, wireless networks, microwave radio relay networks, radar, satellite and spacecraft communication, medical diathermy and cancer treatment, remote sensing, radio astronomy, particle accelerators, spectroscopy, industrial heating, collision avoidance systems, garage door openers and keyless entry systems, and for cooking food in microwave ovens.

  1. ^ Hitchcock, R. Timothy (2004). Radio-frequency and Microwave Radiation. American Industrial Hygiene Assn. p. 1. ISBN 978-1931504553.
  2. ^ a b Kumar, Sanjay; Shukla, Saurabh (2014). Concepts and Applications of Microwave Engineering. PHI Learning Pvt. Ltd. p. 3. ISBN 978-8120349353.
  3. ^ Jones, Graham A.; Layer, David H.; Osenkowsky, Thomas G. (2013). National Association of Broadcasters Engineering Handbook, 10th Ed. Taylor & Francis. p. 6. ISBN 978-1136034107.
  4. ^ Pozar, David M. (1993). Microwave Engineering Addison–Wesley Publishing Company. ISBN 0-201-50418-9.
  5. ^ Sorrentino, R. and Bianchi, Giovanni (2010) Microwave and RF Engineering, John Wiley & Sons, p. 4, ISBN 047066021X.
  6. ^ "Electromagnetic radiation - Microwaves, Wavelengths, Frequency | Britannica". www.britannica.com. Retrieved 2023-08-15.
  7. ^ "Details for IEV number 713-06-03: "microwave"". International Electrotechnical Vocabulary (in Japanese). Retrieved 2024-03-27.
  8. ^ "Details for IEV number 701-02-12: "radio wave"". International Electrotechnical Vocabulary (in Japanese). Retrieved 2024-03-27.