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The C band is a designation by the
Institute of Electrical and Electronics Engineers The Institute of Electrical and Electronics Engineers (IEEE) is a 501(c)(3) professional association for electronic engineering and electrical engineering (and associated disciplines) with its corporate office in New York City and its operation ...
(IEEE) for a portion of the
electromagnetic spectrum The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies. The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from ...
in the
microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ran ...
range of frequencies ranging from 4.0 to 8.0 
gigahertz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one h ...
(GHz). However, the U.S. Federal Communications Commission C band proceeding and auction, designated 3.7–4.2 GHz as C band. The C band is used for many
satellite communications A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. C ...
transmissions, some
Wi-Fi Wi-Fi () is a family of wireless network protocols, based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio wave ...
devices, some
cordless telephones A cordless telephone or portable telephone has a portable telephone handset that connects by radio to a base station connected to the public telephone network. The operational range is limited, usually to the same building or within some short ...
, as well as some
Radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...
and weather radar systems.


Use in satellite communication

The communications C band was the first frequency band that was allocated for commercial telecommunications via satellites. The same frequencies were already in use for terrestrial
microwave radio relay Microwave transmission is the transmission of information by electromagnetic waves with wavelengths in the microwave frequency range of 300MHz to 300GHz(1 m - 1 mm wavelength) of the electromagnetic spectrum. Microwave signals are normally lim ...
chains. Nearly all C-band communication satellites use the band of frequencies from 3.7 to 4.2 GHz for their downlinks, and the band of frequencies from 5.925 to 6.425 GHz for their uplinks. Note that by using the band from 3.7 to 4.0 GHz, this C band overlaps somewhat with the IEEE
S band 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 convention ...
for radars. The C-band communication satellites typically have 24 radio
transponders In telecommunications, a transponder is a device that, upon receiving a signal, emits a different signal in response. The term is a blend of ''transmitter'' and ''responder''. In air navigation or radio frequency identification, a flight trans ...
spaced 20 MHz apart, but with the adjacent transponders on opposite polarizations such that transponders on the ''same'' polarization are always 40 MHz apart. Of this 40 MHz, each transponder utilizes about 36 MHz. (The unused 4.0 MHz between the pairs of transponders acts as "guard bands" for the likely case of imperfections in the microwave
electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...
.) One use of the C band is for satellite communication, whether for full-time satellite television networks or raw satellite feeds, although subscription programming also exists. This use contrasts with
direct-broadcast satellite Satellite television is a service that delivers television programming to viewers by relaying it from a communications satellite orbiting the Earth directly to the viewer's location. The signals are received via an outdoor parabolic antenna commo ...
, which is a completely closed system used to deliver subscription programming to small satellite dishes that are connected with proprietary receiving equipment. The satellite communications portion of the C band is highly associated with
television receive-only Television receive-only (TVRO) is a term used chiefly in North America, South America to refer to the reception of satellite television from FSS-type satellites, generally on C-band analog; free-to-air and unconnected to a commercial DBS prov ...
satellite reception systems, commonly called "big dish" systems, since small receiving antennas are not optimal for C band. Typical antenna sizes on C-band-capable systems range from 6 to 12 feet (1.8 to 3.5 meters) on consumer satellite dishes, although larger ones also can be used. For satellite communications, the microwave frequencies of the C band perform better under adverse weather conditions in comparison with the Ku band (11.2–14.5 
GHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...
), microwave frequencies used by other
communication satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. C ...
s.
Rain fade Rain fade refers primarily to the absorption (optics), absorption of a microwave radio frequency (RF) signal by atmospheric rain, snow, or ice, and losses which are especially prevalent at frequencies above 11 GHz. It also refers to the degradation ...
the collective name for the negative effects of adverse weather conditions on transmission is mostly a consequence of
precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...
and moisture in the air.


Other uses of C-band frequencies

The C band also includes the 5.8 GHz
ISM band The ISM radio bands are portions of the radio spectrum reserved internationally for industrial, scientific and medical (ISM) purposes, excluding applications in telecommunications. Examples of applications for the use of radio frequency (RF) ener ...
between 5.725 and 5.875 GHz, which is used for medical and industrial heating applications and many unlicensed short-range microwave communication systems, such as
cordless phone A cordless telephone or portable telephone has a portable telephone handset that connects by radio to a base station connected to the public telephone network. The operational range is limited, usually to the same building or within some short ...
s,
baby monitor A baby monitor, also known as a baby alarm, is a radio system used to remotely listen to sounds made by an infant. An audio monitor consists of a transmitter unit, equipped with a microphone, placed near to the child. It transmits the sounds by ...
s, and
keyless entry A remote keyless system (RKS), also known as keyless entry or remote central locking, is an electronic lock that controls access to a building or vehicle by using an electronic remote control (activated by a handheld device or automatically b ...
systems for vehicles. The C-band frequencies of 5.4 GHz band .15 to 5.35 GHz, 5.47 to 5.725 GHz, or 5.725 to 5.875 GHz, depending on the region of the worldare used for
IEEE 802.11 IEEE 802.11 is part of the IEEE 802 set of local area network (LAN) technical standards, and specifies the set of media access control (MAC) and physical layer (PHY) protocols for implementing wireless local area network (WLAN) computer commun ...
a
Wi-Fi Wi-Fi () is a family of wireless network protocols, based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio wave ...
wireless computer networks.


C-Band Alliance

The C-Band Alliance was an industry consortium of four large
communications satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. C ...
operators in 2018–2020. In response to a Notice of Proposed Rulemaking of July 2018 from the US
Federal Communications Commission The Federal Communications Commission (FCC) is an independent agency of the United States federal government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisdiction ...
(FCC) to make the 3.7 to 4.2 GHz spectrum available for next-generation terrestrial fixed and mobile broadband services, the C-Band Alliance (CBA) was established in September 2018 by the four satellite operators—
Intelsat Intelsat S.A. (formerly INTEL-SAT, INTELSAT, Intelsat) is a multinational satellite services provider with corporate headquarters in Luxembourg and administrative headquarters in Tysons Corner, Virginia, United States. Originally formed as In ...
,
SES SES, S.E.S., Ses and similar variants can refere to: Business and economics * Socioeconomic status * Scottish Economic Society, a learned society in Scotland * SES, callsign of the TV station SES/RTS (Mount Gambier, South Australia) * SES S.A., ...
,
Eutelsat Eutelsat S.A. is a French satellite operator. Providing coverage over the entire European continent, the Middle East, Africa, Asia and the Americas, it is the world's third-largest satellite operator in terms of revenues. Eutelsat's satellit ...
and
Telesat Telesat, formerly Telesat Canada, is a Canadian satellite communications company founded on May 2, 1969. The company is headquartered in Ottawa. History Telesat began as Telesat Canada, a Canadian Crown corporation created by an Act of Parli ...
—that provide the majority of C-band satellite services in the US, including media distribution reaching 100 million US households. The consortium made a proposal to the FCC to act as a facilitator for the clearing and repurposing of a 200 MHz portion of C-band spectrum to accelerate the deployment of next generation 5G services, while protecting incumbent users and their content distribution and data networks in the US from potential interference. The C-Band Alliance lobbied for a private sale, but the FCC and some
members of Congress A Member of Congress (MOC) is a person who has been appointed or elected and inducted into an official body called a congress, typically to represent a particular constituency in a legislature. The term member of parliament (MP) is an equivalen ...
wanted an
auction An auction is usually a process of buying and selling goods or services by offering them up for bids, taking bids, and then selling the item to the highest bidder or buying the item from the lowest bidder. Some exceptions to this definition ex ...
. In November 2019, the FCC announced that an auction was planned, which took place in December 2020. Cable operators wanted to be compensated for the loss of 200 MHz, which would not include a guard band of 20 MHz to prevent interference. By late 2019, the commercial alliance had weakened. Eutelsat formally pulled out of the consortium in September 2019 over internal disagreements. By February 2020, it became even less of a factor in C-band spectrum reallocation as Intelsat pulled out of the alliance and communicated to the FCC that the C-Band Alliance was dead. Among other claims, Intelsat argued that it was obvious that the FCC was already treating each satellite operator individually and that it therefore made business sense for each company to respond to the FCC from its own commercial perspective. One of the major members of the C-Band Alliance, Intelsat, filed for
bankruptcy Bankruptcy is a legal process through which people or other entities who cannot repay debts to creditors may seek relief from some or all of their debts. In most jurisdictions, bankruptcy is imposed by a court order, often initiated by the debtor ...
on 14 May 2020, just before the new 5G
spectrum auction A spectrum auction is a process whereby a government uses an auction system to sell the rights to transmit signals over specific bands of the electromagnetic spectrum and to assign scarce spectrum resources. Depending on the specific auction form ...
s were to take place, with over in total debt. Public information showed that the company had been considering bankruptcy protection from at least as early as February 2020.https://www.satellitetoday.com/business/2020/02/05/intelsat-reportedly-hires-bankruptcy-firm/
5 February 2020, accessed 14 May 2020.


Differences in frequency range by geographic area

Slight variations in the assignments of C-band frequencies have been approved for use in various parts of the world, depending on their locations in the three
ITU The International Telecommunication Union is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established on 17 May 1865 as the International Telegraph Unio ...
radio regions. Note that one region includes all of
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
and
Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
, plus all of
Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...
; a second includes all of the Americas, and the third region includes all of Asia outside of Russia, plus
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
and
New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
. This latter region is the most populous one, since it includes
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
,
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
,
Pakistan Pakistan ( ur, ), officially the Islamic Republic of Pakistan ( ur, , label=none), is a country in South Asia. It is the world's List of countries and dependencies by population, fifth-most populous country, with a population of almost 24 ...
,
Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
, and
Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical United Nations geoscheme for Asia#South-eastern Asia, south-eastern region of Asia, consistin ...
.


Amateur radio

The Radio Regulations of the
International Telecommunication Union The International Telecommunication Union is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established on 17 May 1865 as the International Telegraph Unio ...
allow
amateur radio Amateur radio, also known as ham radio, is the use of the radio frequency spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emergency communic ...
operations in the frequency range 5.650 to 5.925 GHz, and
amateur satellite An amateur radio satellite is an artificial satellite built and used by amateur radio operators. It forms part of the Amateur-satellite service. These satellites use amateur radio frequency allocations to facilitate communication between amat ...
operations are allowed in the ranges 5.830 to 5.850 GHz for down-links and 5.650 to 5.670 GHz for up-links. This is known as the 5-centimeter band by amateurs and the C band by
AMSAT AMSAT is a name for amateur radio satellite organizations worldwide, but in particular the Radio Amateur Satellite Corporation (AMSAT) with headquarters at Washington, D.C. AMSAT organizations design, build, arrange launches for, and then opera ...
.


Particle accelerators

Particle accelerators may be powered by C-band RF sources. The frequencies are then standardized at 5.996 GHz (Europe) or 5.712 GHz (US), which is the second harmonic of
S band 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 convention ...
.


Nuclear fusion experiments

Several
tokamak A tokamak (; russian: токамáк; otk, 𐱃𐰸𐰢𐰴, Toḳamaḳ) is a device which uses a powerful magnetic field to confine plasma in the shape of a torus. The tokamak is one of several types of magnetic confinement devices being d ...
fusion reactors use high-power C-band RF sources to sustain the toroidal plasma current. Common frequencies include 3.7 GHz (
Joint European Torus The Joint European Torus, or JET, is an operational Magnetic confinement fusion, magnetically confined Plasma (physics), plasma physics experiment, located at Culham Centre for Fusion Energy in Oxfordshire, United Kingdom, UK. Based on a tokamak ...
,
WEST (formerly Tore Supra) WEST, Tungsten (chemical symbol "W") Environment in Steady-state Tokamak, (formerly Tore Supra) is a French tokamak that originally began operating as Tore Supra after the discontinuation of TFR (Tokamak of Fontenay-aux-Roses) and of Petula (in G ...
), 4.6 GHz (Alcator C,
Alcator C-Mod Alcator C-Mod was a tokamak (a type of magnetically confined fusion device) that operated between 1991 and 2016 at the Massachusetts Institute of Technology (MIT) Plasma Science and Fusion Center (PSFC). Notable for its high toroidal magnetic ...
,
EAST East or Orient is one of the four cardinal directions or points of the compass. It is the opposite direction from west and is the direction from which the Sun rises on the Earth. Etymology As in other languages, the word is formed from the fa ...
,
DIII-D DIII-D is a tokamak that has been operated since the late 1980s by General Atomics (GA) in San Diego, USA, for the U.S. Department of Energy. The DIII-D National Fusion Facility is part of the ongoing effort to achieve magnetically confined fusio ...
), 5 GHz (
KSTAR The KSTAR (or Korea Superconducting Tokamak Advanced Research; ko, 초전도 핵융합연구장치, literally "superconducting nuclear fusion research device") is a magnetic fusion device at the Korea Institute of Fusion Energy in Daejeon, So ...
,
ITER ITER (initially the International Thermonuclear Experimental Reactor, ''iter'' meaning "the way" or "the path" in Latin) is an international nuclear fusion research and engineering megaproject aimed at creating energy by replicating, on Earth ...
) and 8 GHz (
Frascati Tokamak Upgrade The Frascati Tokamak Upgrade (FTU) is a tokamak operating at Frascati, Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranea ...
).


Aeronautical radionavigation service

The band 4.2–4.4 GHz is currently allocated to the aeronautical radionavigation service (ARNS) on a primary worldwide basis. RR No. 5.438 notes specifically that this band is reserved exclusively for
radar altimeter A radar altimeter (RA), also called a radio altimeter (RALT), electronic altimeter, reflection altimeter, or low-range radio altimeter (LRRA), measures altitude above the terrain presently beneath an aircraft or spacecraft by timing how long it t ...
installed on board aircraft and for the associated transponders on the ground.


Cellular telephony

In February 2020, the U.S. Federal Communications Commission adopted rules for the C band at 3.7–4.2 GHz that allocated the lower 280 megahertz of the band, at 3.7–3.98 GHz, for terrestrial wireless use. Existing satellite operators will have to repack their operations into the upper 200 megahertz of the band, from 4.0 to 4.2 GHz, and there is a 20-megahertz guard band at 3.98–4.0 GHz. Licenses to use the 3.7–3.98 GHz band were auctioned in December 2020. Verizon, AT&T and T-Mobile are main winners of th
auction
Verizon, AT&T, and T-Mobile spent approximately $45 billion, $23 billion, and $9 billion respectively during the auction. In December 2021, Boeing and Airbus called on the US government to delay the rollout of new 5G phone service that uses C band due to concern of the interference with some sensitive aircraft instruments, especially radio altimeters operating at 4.2–4.4 GHz. On January 18, 2022, Verizon and AT&T announced that they would delay their C-band 5G rollout near airports in response to those concerns.


References


External links


The VSAT Installation Manual Video Presentation shows examples of the arrangement of the Feed for c-band polarization requirements

VSAT Installation Manual with explanation of c-band polarization requirements for a VSAT
{{DEFAULTSORT:C Band Microwave bands Satellite broadcasting