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Encyclopedia > Extremely high frequency
extremely high frequency (EHF)
Cycles per second: 30 GHz to 300 GHz

Wavelength: 10 mm to 1 mm

Extremely high frequency is the highest radio frequency band. EHF runs the range of frequencies from 30 to 300 gigahertz, above which electromagnetic radiation is considered to be low (or far) infrared light, also referred to as Terahertz radiation. This band has a wavelength of ten to one millimetre, giving it the name millimeter band or millimetre wave, sometimes abbreviated MMW or mmW. It has been suggested that this article or section be merged with Radio waves. ... A band is a small section of the spectrum of radio communication frequencies, in which channels are usually used or set aside for the same purpose. ... Look up range in Wiktionary, the free dictionary. ... Sine waves of various frequencies; the lower waves have higher frequencies than those above. ... A gigahertz is a billion hertz or a thousand megahertz, a measure of frequency. ... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... For other uses, see Infrared (disambiguation). ... This article does not cite any references or sources. ... Electromagnetic waves sent at terahertz frequencies, known as terahertz radiation, terahertz waves, terahertz light, T-rays, T-light, T-lux and THz, are in the region of the electromagnetic spectrum between 300 gigahertz (3x1011 Hz) and 3 terahertz (3x1012 Hz), corresponding to the wavelength range starting at submillimeter (<1 millimeter... For other uses, see Wavelength (disambiguation). ... A millimetre (American spelling: millimeter, symbol mm) is an SI unit of length that is equal to one thousandth of a metre. ...


Compared to lower bands terrestrial radio signals in this band are extremely prone to atmospheric attenuation, making them of very little use over long distances. In particular, signals in the 57-64 GHz region are subject to a resonance of the oxygen molecule and are severely attenuated. Even over relatively short distances, rain fade is a serious problem, caused when absorption by rain reduces signal strength. In climates other than deserts absorption due to humidity also has an impact on propagation. While this absorption limits potential communications range, it also allows for smaller frequency reuse distances than lower frequencies. The small wavelength allows modest size antennas to have a small beam width, further increasing frequency reuse potential. In telecommunication, signalling (or signaling) has the following meanings: The use of signals for controlling communications. ... Atmosphere may refer to: a celestial body atmosphere, e. ... Attenuation is the decrease in intensity of electromagnetic radiation due to absorption or scattering of photons. ... Distance is a numerical description of how far apart objects are at any given moment in time. ... This article is about resonance in physics. ... General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colorless (gas) pale blue (liquid) Standard atomic weight 15. ... In satellite communications, rain fade refers to the absorption of a microwave Radio Frequency (RF) signal by rain or snow, and is especially prevalent in frequencies above 11 GHz. ... Absorption, in optics, is the process by which the energy of a photon is taken up by another entity, for example, by an atom whose valence electrons make a transition between two electronic energy levels. ... This article is about precipitation. ... In telecommunications, and particularly in radio, signal strength transmitted signal is being received, measured, or predicted, at a reference point that is a significant distance from the transmitting antenna. ... This article or section is not written in the formal tone expected of an encyclopedia article. ... For other uses, see Wavelength (disambiguation). ...

Contents

Applications

This band is commonly used in radio astronomy and remote sensing. Ground-based radio astronomy is limited to high altitude sites such as Kitt Peak and Atacama Large Millimeter Array (ALMA) due to atmospheric absorption issues. Satellite-based remote sensing near 60 GHz can determine temperature distributions in the upper atmosphere by measuring radiation emitted from oxygen molecules that is a function of temperature and pressure. The Very Large Array, a radio interferometer in New Mexico, USA Radio astronomy is a subfield of astronomy that studies celestial objects in the radio frequency portion of the electromagnetic spectrum. ... For the purported psychic ability to sense remotely, see Remote viewing right Synthetic aperture radar image of Death Valley colored using polarimetry In the broadest sense, remote sensing is the short or large-scale acquisition of information of an object or phenomenon, by the use of either recording or real... The Kitt Peak National Observatory (KPNO) is located on a 6,875 ft peak of the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono Oodham Nation, 55 miles southwest of Tucson. ... Look up alma in Wiktionary, the free dictionary. ... Earths atmosphere is the layer of gases surrounding the planet Earth and retained by the Earths gravity. ...


In the United States, the band 38.6 - 40.0 GHz is used for licensed high-speed microwave data links, and the 60 GHz band can be used for unlicensed short range (1.7 km) data links with data throughputs up to 2.5 Gbit/s (gigabits per second). It is used commonly in flat terrain.


The 71-76, 81-86 and 92-95 GHz bands are also used for point-to-point high-bandwidth communication links. These frequencies, as opposed to the 60 GHz frequency, require a transmitting license in the US from the FCC, though they do not suffer from the effects of oxygen absorption as the 60 GHz does. There are plans for 10 Gbit/s links using these frequencies as well. In the case of the 92-95 GHz band, a small 100 MHz range has been reserved for space-borne radios, making this reserved range limited to a transmission rate of under a few gigabits per second. The abbreviation FCC can refer to: Face-centered cubic (usually fcc), a crystallographic structure Federal Communications Commission, a US government organization Farm Credit Corporation/Farm Credit Canada, a Canadian government organization Families with Children from China, an adoption support organization Florida Christian College, a college in central Florida Fresno City...


The band is essentially undeveloped and available for use in a broad range of new products and services, including high-speed, point-to-point wireless local area networks and broadband Internet access. Highly directional, "pencil-beam" signal characteristics permit systems in these bands to be engineered in close proximity to one another without causing interference. Potential applications include radar systems with very high resolution. For other uses, see Radar (disambiguation). ...


Uses of the millimeter wave bands includes point-to-point communications, intersatellite links, and point-to-multipoint communications.


Because of shorter wavelengths, the band permits the use of smaller antennas than would be required for similar circumstances in the lower bands, to achieve the same high directivity and high gain. The immediate consequence of this high directivity, coupled with the high free space loss at these frequencies, is the possibility of a more efficient use of the spectrum for point-to-multipoint applications. Since a greater number of high directive antennas can be placed than less directive antennas in a given area, the net result is higher reuse of the spectrum, and higher density of users, as compared to lower frequencies. Furthermore, due to the fact that one can place more voice channels or broadband information using a higher frequency to transmit the information, this spectrum could potentially be used as a replacement for or supplement to fiber optics. [citation needed]


The U.S. Air Force is reported to have developed a nonlethal weapon system called Active Denial System (ADS) which emits a beam of radiation with a wavelength of 3mm [2]. The weapon is reportedly not painful, but rather makes the target feel as if his or her clothes are going to catch fire [3]. // Humvee with ADS mounted. ...


Security

A recent development has been imagers for security applications as clothing and other organic materials are translucent in some mm-wave atmospheric windows. [4] Privacy advocates are concerned about the use of this technology because it allows screens to see airport passengers without clothing.


The TSA is planning to deploy several machines in airports for testing in the United States in early Spring[citation needed]. These machines have been deployed in the Jersey City PATH train system as well[1]. TSA emblem The Transportation Security Administration (TSA) is a U.S. government agency that was created as part of the Aviation and Transportation Security Act passed by the U.S. Congress and signed into law by President George W. Bush on November 19, 2001. ... The skyline of Jersey City, as seen from Lower New York Bay. ...


Currently the technology does not mask any part of the bodies of the people who are being scanned and proposed remedies for privacy concerns include only scanning people who are detected to be carrying an object that may be a weapon and developing technology[citation needed] to mask genitals and other 'private parts', and an article about the PATH system states that an unnamed government official stated this technology is already in place[1], leading the journalist to conclude "there are no...privacy issues for travelers".


Three security scanners using millimeter waves were put into use at Schiphol Airport in Amsterdam on 15 May 2007, with more expected to be installed later. The passenger's head is masked from the view of the security personnel. The security scan is a device to frisk a person without making physical contact. ... Schiphol (IATA: AMS, ICAO: EHAM) (municipality Haarlemmermeer) is the Netherlands main airport. ... is the 135th day of the year (136th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ...


According to Farran Technologies, a manufacturer of one model of the millimeter wave scanner, the technology exists to extend the search area to as far as 50 meters beyond the scanning area which would allow security workers to scan a large number of people without their awareness that they are being scanned [5].


Notes

  1. ^ a b [1] Mirror for Star Ledger Article "PATH riders to face anti-terror screening -- Program will begin at station in Jersey City" 2006/07/12 Wed Pg 014

See also

Radio spectrum
ELF SLF ULF VLF LF MF HF VHF UHF SHF EHF
3 Hz 30 Hz 300 Hz 3 kHz 30 kHz 300 kHz 3 MHz 30 MHz 300 MHz 3 GHz 30 GHz
30 Hz 300 Hz 3 kHz 30 kHz 300 kHz 3 MHz 30 MHz 300 MHz 3 GHz 30 GHz 300 GHz


Electromagnetic waves sent at terahertz frequencies, known as terahertz radiation, terahertz waves, terahertz light, T-rays, T-light, T-lux and THz, are in the region of the electromagnetic spectrum between 300 gigahertz (3x1011 Hz) and 3 terahertz (3x1012 Hz), corresponding to the wavelength range starting at submillimeter (<1 millimeter... Microwave Slang for small waves, like at a beach, often used by surfers. ... In electromagnetic wave propagation, the knife-edge effect is a redirection by diffraction of a portion of the incident radiation that strikes a well-defined obstacle such as a mountain range or the edge of a building. ... Radio frequency, or RF, refers to that portion of the electromagnetic spectrum in which electromagnetic waves can be generated by alternating current fed to an antenna. ... Extremely low frequency (ELF) is the band of radio frequencies from 3 to 30 Hz. ... Super Low Frequency (SLF) is the frequency range between 30 hertz and 300 hertz. ... Ultra Low Frequency (ULF) is the frequency range between 300 hertz and 3000 hertz. ... Very low frequency or VLF refers to radio frequencies (RF) in the range of 3 to 30 kHz. ... Low Frequency or LF refers to Radio Frequencies (RF) in the range of 30–300 kHz. ... Medium frequency (MF) refers to radio frequencies (RF) in the range of 300 kHz to 3000 kHz. ... High frequency (HF) radio frequencies are between 3 and 30 MHz. ... Very high frequency (VHF) is the radio frequency range from 30 MHz (wavelength 10 m) to 300 MHz (wavelength 1 m). ... This article is about the radio frequency. ... Microwave Slang for small waves, like at a beach, often used by surfers. ...

Legend γ = Gamma rays HX = Hard X-rays SX = Soft X-Rays EUV = Extreme ultraviolet NUV = Near ultraviolet Visible light NIR = Near infrared MIR = Moderate infrared FIR = Far infrared Radio waves EHF = Extremely high frequency (Microwaves) SHF = Super high frequency (Microwaves) UHF = Ultra high frequency VHF = Very high frequency HF = High... This article is about electromagnetic radiation. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... For other uses, see Ultraviolet (disambiguation). ... “Visible light” redirects here. ... For other uses, see Infrared (disambiguation). ... Electromagnetic waves sent at terahertz frequencies, known as terahertz radiation, terahertz waves, terahertz light, T-rays, T-light, T-lux and THz, are in the region of the electromagnetic spectrum between 300 gigahertz (3x1011 Hz) and 3 terahertz (3x1012 Hz), corresponding to the wavelength range starting at submillimeter (<1 millimeter... This article is about the type of Electromagnetic radiation. ... Radio waves are electromagnetic waves occurring on the radio frequency portion of the electromagnetic spectrum. ... “Visible light” redirects here. ... Violet (named after the flower violet) is used in two senses: first, referring to the color of light at the short-wavelength end of the visible spectrum, approximately 380–420 nanometres (this is a spectral color). ... For other uses, see Blue (disambiguation). ... For other uses, see Green (disambiguation). ... A yellow Tulip. ... The orange, the fruit from which the modern name of the orange colour comes. ... For other uses, see Red (disambiguation). ... This article is about the type of Electromagnetic radiation. ... The W band of the microwave part of the electromagnetic spectrum and ranges from 75 to 111 GHz. ... The V band (vee-band) of the electromagnetic spectrum ranges from 50 to 75 GHz. ... The Ka band (kurz-above band) is a portion of the K band of the microwave band of the electromagnetic spectrum. ... K band is a portion of the electromagnetic spectrum in the microwave range of frequencies ranging between 12 to 63 GHz. ... The Ku band (kay-yoo kurz-under band) is a portion of the electromagnetic spectrum in the microwave range of frequencies ranging from 11 to 18 GHz. ... The X band (3-cm radar spot-band) of the microwave band of the electromagnetic spectrum roughly ranges from 5. ... C band (compromise band) is a portion of electromagnetic spectrum in the microwave range of frequencies ranging from 4 to 6 GHz. ... The S band ranges from 2 to 4 GHz. ... L band (20-cm radar long-band) is a portion of the microwave band of the electromagnetic spectrum ranging roughly from 0. ... Radio frequency, or RF, refers to that portion of the electromagnetic spectrum in which electromagnetic waves can be generated by alternating current fed to an antenna. ... Microwave Slang for small waves, like at a beach, often used by surfers. ... This article is about the radio frequency. ... Very high frequency (VHF) is the radio frequency range from 30 MHz (wavelength 10 m) to 300 MHz (wavelength 1 m). ... High frequency (HF) radio frequencies are between 3 and 30 MHz. ... Medium frequency (MF) refers to radio frequencies (RF) in the range of 300 kHz to 3000 kHz. ... Low Frequency or LF refers to Radio Frequencies (RF) in the range of 30–300 kHz. ... Very low frequency or VLF refers to radio frequencies (RF) in the range of 3 to 30 kHz. ... Ultra Low Frequency (ULF) is the frequency range between 300 hertz and 3000 hertz. ... Super Low Frequency (SLF) is the frequency range between 30 hertz and 300 hertz. ... Extremely low frequency (ELF) is the band of radio frequencies from 3 to 30 Hz. ... For other uses, see Wavelength (disambiguation). ... This article is about the type of Electromagnetic radiation. ... A solid-state, analog shortwave receiver Shortwave radio operates between the frequencies of 3 MHz (3,000 kHz) and 30 MHz (30,000 kHz) [1] and came to be referred to as such in the early days of radio because the wavelengths associated with this frequency range were shorter than... Mediumwave radio transmissions serves as the most common band for broadcasting. ... This article does not cite any references or sources. ...

External links

  • FCC bulletin on MMW propagation
  • Asyrmatos Millimeter Wave Communication System
  • L-3 Communications ProVision™ Body Screening System
  • FCC 70/80/90 GHz overview.
  • FCC 57-64 GHz rules.
  • Civil mm-wave Regulation in US

Academic

  • Tomislav Stimac, "Definition of frequency bands (VLF, ELF... etc.)". IK1QFK Home Page (vlf.it).
  • Millimetre-Wave Technology Group at Rutherford-Appleton Laboratory
  • St. Andrews University mm-wave group
  • A Survey of University Capabilities for a New Canadian Radio Telescope



  Results from FactBites:
 
Extremely high frequency - Wikipedia, the free encyclopedia (173 words)
Extremely high frequency is the highest radio frequency band.
EHF runs the range of frequencies from 30 to 300 gigahertz, above which electromagnetic radiation is considered to be low (or far) infrared light.
Radio signals in this band are extremely prone to atmospheric attenuation, making them of very little use over long distances.
Ultra high frequency - Wikipedia, the free encyclopedia (963 words)
Ultra high frequency (UHF) designates a range (band) of electromagnetic waves whose frequency is between 300 MHz (Wavelength 1 meter) and 3.0 GHz (Wavelength 10 centimetres).
Waves whose frequency is above the UHF band fall into the microwave or higher bands, while lower frequency signals fall into the VHF or lower bands.
Modern mobile phones also transmit and receive within the UHF spectrum, and UHF is widely used for two-way radio communication (usually using narrowband frequency modulation, but digital services are on the rise) by both public service agencies and the general public.
  More results at FactBites »

 
 

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