Ultra high frequency

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Ultra high frequency
Ultra high frequency (ITU)
Frequency range
300 MHz to 3 GHz
Wavelength range
1 m to 1 dm
Related bands
Ultra high frequency (IEEE)
Frequency range
300 MHz to 1 GHz
Wavelength range
1 m to 3 dm
Related bands

Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300  megahertz (MHz) and 3  gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (one decimeter). Radio waves with frequencies above the UHF band fall into the super-high frequency (SHF) or microwave frequency range. Lower frequency signals fall into the VHF (very high frequency) or lower bands. UHF radio waves propagate mainly by line of sight; they are blocked by hills and large buildings although the transmission through building walls is strong enough for indoor reception. They are used for television broadcasting, cell phones, satellite communication including GPS, personal radio services including Wi-Fi and Bluetooth, walkie-talkies, cordless phones, and numerous other applications.

Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around twenty thousand times per second to around three hundred billion times per second. This is roughly between the upper limit of audio frequencies and the lower limit of infrared frequencies; these are the frequencies at which energy from an oscillating current can radiate off a conductor into space as radio waves. Different sources specify different upper and lower bounds for the frequency range.

Microwave form of electromagnetic radiation

Microwaves are a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter; with frequencies between 300 MHz (1 m) and 300 GHz (1 mm). Different sources define different frequency ranges as microwaves; the above broad definition includes both UHF and EHF bands. A more common definition in radio engineering is the range between 1 and 100 GHz. In all cases, microwaves include the entire SHF band at minimum. 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.

Very high frequency The range 30-300 MHz of the electromagnetic spectrum

Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter. Frequencies immediately below VHF are denoted high frequency (HF), and the next higher frequencies are known as ultra high frequency (UHF).

Contents

The IEEE defines the UHF radar band as frequencies between 300 MHz and 1 GHz. [1] Two other IEEE radar bands overlap the ITU UHF band: the L band between 1 and 2 GHz and the S band between 2 and 4 GHz.

Institute of Electrical and Electronics Engineers scholarly society, publisher and standards organization, headquartered in US

The Institute of Electrical and Electronics Engineers (IEEE) is a professional association for electronic engineering and electrical engineering with its corporate office in New York City and its operations center in Piscataway, New Jersey. It was formed in by Dr.Madhusudhan S in 1963 from the amalgamation of the American Institute of Electrical Engineers and the Institute of Radio Engineers.

The L band is the Institute of Electrical and Electronics Engineers (IEEE) designation for the range of frequencies in the radio spectrum from 1 to 2 gigahertz (GHz).

The S band is a designation by the Institute of Electrical and Electronics Engineers (IEEE) for a part of the microwave band of the electromagnetic spectrum covering frequencies from 2 to 4 gigahertz (GHz). Thus it crosses the conventional boundary between the UHF and SHF bands at 3.0 GHz. The S band is used by airport surveillance radar for air traffic control, weather radar, surface ship radar, and some communications satellites, especially those used by NASA to communicate with the Space Shuttle and the International Space Station. The 10 cm radar short-band ranges roughly from 1.55 to 5.2 GHz. The S band also contains the 2.4–2.483 GHz ISM band, widely used for low power unlicensed microwave devices such as cordless phones, wireless headphones (Bluetooth), wireless networking (WiFi), garage door openers, keyless vehicle locks, baby monitors as well as for medical diathermy machines and microwave ovens. India’s regional satellite navigation network (IRNSS) broadcasts on 2.483778 to 2.500278 GHz.

UHF television antenna on a residence. This type of antenna, called a Yagi-Uda antenna, is widely used at UHF frequencies. UHF TV Antenna 001.JPG
UHF television antenna on a residence. This type of antenna, called a Yagi-Uda antenna, is widely used at UHF frequencies.
Another antenna type common at UHF; a reflective array TV antenna consisting of two high-bandwidth "bow tie" dipoles in front of a flat reflector screen. The antenna is oriented so as to receive vertically-polarized radio waves, while most UHF TV stations transmit horizontally polarized waves. Reflective array, bow tie, grid, or panel UHF television antenna,.jpg
Another antenna type common at UHF; a reflective array TV antenna consisting of two high-bandwidth "bow tie" dipoles in front of a flat reflector screen. The antenna is oriented so as to receive vertically-polarized radio waves, while most UHF TV stations transmit horizontally polarized waves.

Propagation characteristics

Walkie talkies which operate on the 446 MHz PMR (Professional Mobile Radio) band. The 67 cm wavelength permits them to use very short "Rubber Ducky" antennas. Binatone MR 200 radio 1.jpg
Walkie talkies which operate on the 446 MHz PMR (Professional Mobile Radio) band. The 67 cm wavelength permits them to use very short "Rubber Ducky" antennas.

Radio waves in the UHF band travel almost entirely by line-of-sight propagation (LOS) and ground reflection; unlike in the HF band there is little to no reflection from the ionosphere (skywave propagation), or ground wave. [2] UHF radio waves are blocked by hills and cannot travel beyond the horizon, but can penetrate foliage and buildings for indoor reception. Since the wavelengths of UHF waves are comparable to the size of buildings, trees, vehicles and other common objects, reflection and diffraction from these objects can cause fading due to multipath propagation, especially in built-up urban areas. Atmospheric moisture reduces, or attenuates, the strength of UHF signals over long distances, and the attenuation increases with frequency. UHF TV signals are generally more degraded by moisture than lower bands, such as VHF TV signals.

Line-of-sight propagation characteristic of electromagnetic radiation or acoustic wave propagation which means waves which travel in a direct path from the source to the receiver

Line-of-sight propagation is a characteristic of electromagnetic radiation or acoustic wave propagation which means waves travel in a direct path from the source to the receiver. Electromagnetic transmission includes light emissions traveling in a straight line. The rays or waves may be diffracted, refracted, reflected, or absorbed by the atmosphere and obstructions with material and generally cannot travel over the horizon or behind obstacles.

High frequency The range 3-30 MHz of the electromagnetic spectrum

High frequency (HF) is the ITU designation for the range of radio frequency electromagnetic waves between 3 to 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten decameters. Frequencies immediately below HF are denoted medium frequency (MF), while the next band of higher frequencies is known as the very high frequency (VHF) band. The HF band is a major part of the shortwave band of frequencies, so communication at these frequencies is often called shortwave radio. Because radio waves in this band can be reflected back to Earth by the ionosphere layer in the atmosphere – a method known as "skip" or "skywave" propagation – these frequencies are suitable for long-distance communication across intercontinental distances and for mountainous terrains which prevent line-of-sight communications. The band is used by international shortwave broadcasting stations (2.31–25.82 MHz), aviation communication, government time stations, weather stations, amateur radio and citizens band services, among other uses.

Ionosphere The ionized part of Earths upper atmosphere

The ionosphere is the ionized part of Earth's upper atmosphere, from about 60 km (37 mi) to 1,000 km (620 mi) altitude, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays an important role in atmospheric electricity and forms the inner edge of the magnetosphere. It has practical importance because, among other functions, it influences radio propagation to distant places on the Earth. The region below the ionosphere is called neutral atmosphere, or neutrosphere.

Since UHF transmission is limited by the visual horizon to 30–40 miles (48–64 km) and usually to shorter distances by local terrain, it allows the same frequency channels to be reused by other users in neighboring geographic areas (frequency reuse). Radio repeaters are used to retransmit UHF signals when a distance greater than the line of sight is required.

Repeater Relay station

In telecommunications, a repeater is an electronic device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction.

Occasionally when conditions are right, UHF radio waves can travel long distances by tropospheric ducting as the atmosphere warms and cools throughout the day.

Antennas

Corner reflector UHF-TV antenna from 1950s Corner reflector TV antenna.png
Corner reflector UHF-TV antenna from 1950s

The length of an antenna is related to the length of the radio waves used. Due to the short wavelengths, UHF antennas are conveniently stubby and short; at UHF frequencies a quarter-wave monopole, the most common omnidirectional antenna is between 2.5 and 25 cm long. UHF wavelengths are short enough that efficient transmitting antennas are small enough to mount on handheld and mobile devices, so these frequencies are used for two way land mobile radio systems, such as walkie-talkies, two way radios in vehicles, and for portable wireless devices; cordless phones and cell phones. Omnidirectional UHF antennas used on mobile devices are usually short whips, sleeve dipoles, rubber ducky antennas or the planar inverted F antenna (PIFA) used in cellphones. Higher gain omnidirectional UHF antennas can be made of collinear arrays of dipoles and are used for mobile base stations and cellular base station antennas.

Antenna (radio) electrical device which converts electric power into radio waves, and vice versa

In radio engineering, an antenna is the interface between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver. In transmission, a radio transmitter supplies an electric current to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves. In reception, an antenna intercepts some of the power of a radio wave in order to produce an electric current at its terminals, that is applied to a receiver to be amplified. Antennas are essential components of all radio equipment.

Monopole antenna type of radio antenna

A monopole antenna is a class of radio antenna consisting of a straight rod-shaped conductor, often mounted perpendicularly over some type of conductive surface, called a ground plane. The driving signal from the transmitter is applied, or for receiving antennas the output signal to the receiver is taken, between the lower end of the monopole and the ground plane. One side of the antenna feedline is attached to the lower end of the monopole, and the other side is attached to the ground plane, which is often the Earth. This contrasts with a dipole antenna which consists of two identical rod conductors, with the signal from the transmitter applied between the two halves of the antenna.

Omnidirectional antenna radio antenna that sends signals in every direction

In radio communication, an omnidirectional antenna is a class of antenna which radiates equal radio power in all directions perpendicular to an axis, with power varying with angle to the axis, declining to zero on the axis. When graphed in three dimensions (see graph) this radiation pattern is often described as doughnut-shaped. Note that this is different from an isotropic antenna, which radiates equal power in all directions, having a spherical radiation pattern. Omnidirectional antennas oriented vertically are widely used for nondirectional antennas on the surface of the Earth because they radiate equally in all horizontal directions, while the power radiated drops off with elevation angle so little radio energy is aimed into the sky or down toward the earth and wasted. Omnidirectional antennas are widely used for radio broadcasting antennas, and in mobile devices that use radio such as cell phones, FM radios, walkie-talkies, wireless computer networks, cordless phones, GPS, as well as for base stations that communicate with mobile radios, such as police and taxi dispatchers and aircraft communications.

The short wavelengths also allow high gain antennas to be conveniently small. High gain antennas for point-to-point communication links and UHF television reception are usually Yagi, log periodic, corner reflectors, or reflective array antennas. At the top end of the band slot antennas and parabolic dishes become practical. For satellite communication, helical, and turnstile antennas are used since satellites typically employ circular polarization which is not sensitive to the relative orientation of the transmitting and receiving antennas. For television broadcasting specialized vertical radiators that are mostly modifications of the slot antenna or reflective array antenna are used: the slotted cylinder, zig-zag, and panel antennas.

Applications

UHF television broadcasting fulfilled the demand for additional over-the-air television channels in urban areas. Today, much of the bandwidth has been reallocated to land mobile, trunked radio and mobile telephone use. UHF channels are still used for digital television.

Since at UHF frequencies transmitting antennas are small enough to install on portable devices, the UHF spectrum is used worldwide for land mobile radio systems, two-way radios used for voice communication for commercial, industrial, public safety, and military purposes. Examples of personal radio services are GMRS, PMR446, and UHF CB. Some wireless computer networks use UHF frequencies. The widely adopted GSM and UMTS cellular networks use UHF cellular frequencies.

Major telecommunications providers have deployed voice and data cellular networks in UHF/VHF range. This allows mobile phones and mobile computing devices to be connected to the public switched telephone network and public Internet.

UHF radars are said to be effective at tracking stealth fighters, if not stealth bombers. [3]

Examples of UHF frequency allocations

Australia

Canada

United Kingdom

United States

UHF channels are used for digital television broadcasting on both over the air channels and cable television channels. Since 1962, UHF channel tuners (at the time, channels 14-83) have been required in television receivers by the All-Channel Receiver Act. However, because of their more limited range, and because few sets could receive them until older sets were replaced, UHF channels were less desirable to broadcasters than VHF channels (and licenses sold for lower prices).

A complete list of US Television Frequency allocations can be found at North American Television Frequencies.

There is a considerable amount of lawful unlicensed activity (cordless phones, wireless networking) clustered around 900 MHz and 2.4 GHz, regulated under Title 47 CFR Part 15. These ISM bands – frequencies with a higher unlicensed power permitted for use originally by Industrial, Scientific, Medical apparatus – are now some of the most crowded in the spectrum because they are open to everyone. The 2.45 GHz frequency is the standard for use by microwave ovens, adjacent to the frequencies allocated for Bluetooth network devices.

The spectrum from 806 MHz to 890 MHz (UHF channels 70–83) was taken away from TV broadcast services in 1983, primarily for analog mobile telephony.

In 2009, as part of the transition from analog to digital over-the-air broadcast of television, the spectrum from 698 MHz to 806 MHz (UHF channels 52–69) was removed from TV broadcasting, making it available for other uses. Channel 55, for instance, was sold to Qualcomm for their MediaFLO service, which was later sold to AT&T, and discontinued in 2011. Some US broadcasters had been offered incentives to vacate this channel early, permitting its immediate mobile use. The FCC's scheduled auction for this newly available spectrum was completed in March 2008. [8]

The FCC has allowed Americans to connect any device and any application to the 22 MHz of radio spectrum that people are calling the 700 MHz band. The FCC did not include a wholesale condition, which would have required the owner of the band to resell bandwidth to third parties who could then service the end user. Google argued that the wholesale requirement would have stimulated internet competition. As of 2007, 96% of the country's broadband access was controlled by DSL and cable providers. A wholesale condition could have meant a third option for internet service. [9]

See also

Related Research Articles

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Radio spectrum part of the electromagnetic spectrum from 3 Hz to 3000 GHz (3 THz)

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AO-51

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High-speed multimedia radio

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A spectrum auction is a process whereby a government uses an auction system to sell the rights (licenses) to transmit signals over specific bands of the electromagnetic spectrum and to assign scarce spectrum resources. Depending on the specific auction format used, a spectrum auction can last from a single day to several months from the opening bid to the final winning bid. With a well-designed auction, resources are allocated efficiently to the parties that value them the most, the government securing revenue in the process. Spectrum auctions are a step toward market-based spectrum management and privatization of public airwaves, and are a way for governments to allocate scarce resources. Alternatives to auctions include administrative licensing, such as the comparative hearings conducted historically, or lotteries.

Advanced Wireless Services (AWS) is a wireless telecommunications spectrum band used for mobile voice and data services, video, and messaging. AWS is used in the United States, Argentina, Canada, Colombia, Mexico, Chile, Paraguay, Peru, Ecuador, Uruguay and Venezuela. It replaces some of the spectrum formerly allocated to Multipoint Multichannel Distribution Service (MMDS), sometimes referred to as Wireless Cable, that existed from 2150 to 2162 MHz.

The United States 700 MHz FCC wireless spectrum auction, officially known as Auction 73, was started by the Federal Communications Commission (FCC) on January 24, 2008 for the rights to operate the 700 MHz radio frequency band in the United States. The details of process were the subject of debate among several telecommunications companies, including Verizon Wireless, AT&T Mobility, as well as the Internet company Google. Much of the debate swirled around the open access requirements set down by the Second Report and Order released by the FCC determining the process and rules for the auction. All bidding was required by law to commence by January 28.

Wireless Medical Telemetry Service (WMTS) is a wireless service specifically defined in the United States by the Federal Communications Commission (FCC) for transmission of data related to a patient's health (biotelemetry). It was created in 2000 because of interference issues due to establishment of digital television. The bands defined are 608-614 MHz, 1395-1400 MHz and 1427-1432 MHz. Devices using these bands are typically proprietary. Further, the use of these bands has not been internationally agreed to, so many times devices cannot be marketed or used freely in countries other than the United States.

The digital dividend refers to the radio spectrum which is released in the process of digital television transition. When television broadcasters switch from analog TV to digital-only platforms, part of the electromagnetic spectrum that has been used for broadcasting will be freed-up because digital television needs less spectrum than analog television. One reason is that new digital video compression technology can transmit numerous digital subchannels using the same amount of spectrum used to transmit one analog TV channel. However, the primary reason is that digital transmissions require much less of a guard band on either side, since they are not nearly as prone to RF interference from adjacent channels. Because of this, there is no longer any need to leave empty channels to protect stations from each other, in turn allowing stations to be repacked into fewer channels, leaving more contiguous spectrum to be allocated for other wireless services.

The Pan-American television frequencies are different for terrestrial and cable television systems. Terrestrial television channels are divided into two bands: the VHF band which comprises channels 2 through 13 and occupies frequencies between 54 through 216 MHz, and the UHF band, which comprises channels 14 through 51 and occupies frequencies between 470 and 700 MHz. These bands are different enough in frequency that they often require separate antennas to receive, and separate tuning controls on the television set. The VHF band is further divided into two frequency ranges: VHF low band between 54 and 86 MHz, containing channels 2 through 6, and VHF high band between 174 and 216 MHz, containing channels 7 through 13. The wide spacing between these frequency bands is responsible for the complicated design of rooftop TV antennas. The UHF band has higher noise and greater attenuation, so higher gain antennas are often required for UHF.

C band (IEEE) 4-8GHz

The C band is a designation by the Institute of Electrical and Electronics Engineers (IEEE) for a portion of the electromagnetic spectrum in the microwave range of frequencies ranging from 4.0 to 8.0 gigahertz (GHz); however, this definition is the one used by radar manufacturers and users, not necessarily by microwave radio telecommunications users. The C band is used for many satellite communications transmissions, some Wi-Fi devices, some cordless telephones as well as some surveillance and weather radar systems.

References

  1. "IEEE 521-2002 - IEEE Standard Letter Designations for Radar-Frequency Bands". Standards.ieee.org. Retrieved 17 December 2017.
  2. Seybold, John S. (2005). Introduction to RF Propagation. John Wiley and Sons. pp. 55–58. ISBN   0471743682.
  3. MINNICK, WENDELL (22 November 2014). "China's Anti-Stealth Radar Comes to Fruition". Defensenews.com. Gannett. Retrieved 25 November 2014.
  4. https://www.acma.gov.au/-/media/Spectrum-Engineering/Information/pdf/Radiocommunications-Assignment-and-Licensing-Instruction-RALI-MS22-400-MHz-Plan.pdf
  5. "Digital Audio Broadcasting (DAB) - History of Canadian Broadcasting". Broadcasting-history.ca. Retrieved 15 October 2017.
  6. UK Digital Terrestrial Television Transmitter Frequency and Site Data, Ofcom, retrieved 16 October 2013
  7. "800 MHz & 2.6 GHz Combined Award". The Office of Communications. Retrieved 2014-11-21.
  8. Hansell, Saul. "Going Once…Going Twice…The 700 Mhz Spectrum is Sold". Bits.blos.nytimes.com. Retrieved 15 October 2017.
  9. FCC opens up US wireless spectrum, The Register, 1 August 2007, Cade Metz
  10. [ dead link ]
  11. "T-Band Report" (PDF). Npstc.org. Retrieved 17 December 2017.
  12. "Wireless Medical Telemetry Service (WMTS)". Fcc.gov. Retrieved 17 December 2017.
  13. 1 2 "TerreStar Corporation Request for Temporary Waiver of Substantial Service Requirements for 1.4 GHz Licenses" (PDF). the FCC. 2017-10-10. Retrieved 2017-10-11.
  14. 1 2 3 "Ligado Ex Parte re Iridium Analysis (PUBLIC 11-2-2016)" (PDF). Ecfsapi.fcc.gov. Retrieved 17 December 2017.
  15. "Galileo Signal Plan". Navipedia.net. Retrieved 17 December 2017.
  16. "REQUEST FOR WAIVER AND PUBLIC INTEREST STATEMENT". FCC. 2016-06-04. Retrieved 2018-04-02.
  17. "AWS-3 Transition". Ntia.doc.gov. Retrieved 17 December 2017.
  18. 1 2 "AT&T Mobility Petition for Limited Waiver of Interim Performance Requirement for 2.3 GHz WCS C and D Block Licenses" (PDF). Ecfsapi.fcc.gov. Retrieved 17 December 2017.
  19. "Globalstar Overview" (PDF). Globalstar.com. Retrieved 17 December 2017.
  20. "Broadband Radio Service & Education Broadband Service". The FCC. Retrieved 2018-06-05.