View source for X band

[[File:Radar antennas on USS Theodore Roosevelt SPS-64.jpg|right|thumb|An X-band [[marine radar]] antenna on a ship]]

X band is used in radar applications, including [[continuous wave|continuous-wave]], pulsed, single-[[polarization (waves)|polarization]], dual-polarization, [[synthetic aperture radar]], and [[phased array]]s. X-band radar frequency sub-bands are used in [[civilian|civil]], [[armed force|military]], and [[government]] institutions for [[weather radar|weather monitoring]], [[air traffic control]], [[Vessel Traffic Service|maritime vessel traffic control]], [[Fire-control radar|defense tracking]], and [[Radar gun|vehicle speed detection]] for law enforcement.<ref>{{Cite web |url=http://www.everythingweather.com/weather-radar/bands.shtml |title=Radar Bands |website=www.everythingweather.com}}</ref><ref>{{cite web |title=What are S- and X-Band Radar and How Are They Used Today? |url=https://www.leonardodrs.com/news/thought-leadership/what-are-s-and-x-band-radar-and-how-are-they-used-today/ |website=Leonardo.com |publisher=[[Leonardo DRS]] |access-date=3 July 2024 |date=December 19, 2022}}</ref>

X band is often used in modern radars. The shorter [[wavelength]]s of the X&nbsp;band provide higher-resolution imagery from [[high-resolution]] [[imaging radar]]s for target identification and discrimination. X-band weather radars offer significant potential for short-range observations, but the loss of signal strength ([[attenuation]]) under rainy conditions limits their use at longer range.<ref>Matrosov, S.&nbsp;Y., Kennedy, P.&nbsp;C. and Cifelli, R., 2014. Experimentally based estimates of relations between X-band radar signal attenuation characteristics and differential phase in rain. Journal of Atmospheric and Oceanic Technology, 31(11), pp.&nbsp;2442–2450.</ref>

=== Terrestrial communications and networking ===
The X band 10.15 to 10.7&nbsp;GHz segment is used for terrestrial [[broadband]] in many countries, such as Brazil, Mexico, Saudi Arabia, Denmark, Ukraine, Spain and Ireland.<ref name="Ogier">{{cite web |title=Broadband Wireless |url=http://ogierelectronics.com/broadband-wireless.php |access-date=5 May 2020}}</ref> [[Alvarion]], [[Cambridge Broadband|CBNL]], CableFree and Ogier make systems for this, though each has a proprietary airlink. [[DOCSIS]] (Data Over Cable Service Interface Specification) the standard used for providing [[cable internet]] to customers, uses some X band frequencies. The home / business [[customer-premises equipment]] (CPE) has a single coaxial cable with a power adapter connecting to an ordinary cable modem. The local oscillator is usually 9750&nbsp;MHz, the same as for K<sub>u</sub> band satellite TV LNB. Two way applications such as broadband typically use a 350&nbsp;MHz TX offset.

=== Space communications ===
{{Further|X Band Satellite Communication}}

=== Space communications for science and research ===
[[File:Canberra Deep Dish Communications Complex - GPN-2000-000502.jpg|thumb|upright=1.1|[[DSS-43]] 70 meter X-band spacecraft communication antenna at the [[Canberra Deep Space Communication Complex]], Australia.]]

Small portions of the X band are assigned by the [[International Telecommunication Union]] (ITU) exclusively for deep space telecommunications. The primary user of [[Deep space bands|this allocation]] is the American [[NASA]] [[Deep Space Network]] (DSN). DSN facilities are  in [[Goldstone, California]] (in the [[Mojave Desert]]), near [[Canberra, Australia]], and near [[Madrid, Spain]], and provide continual communications from the Earth to almost any point in the [[Solar System]] independent of Earth rotation. (DSN stations are also capable of using the older and lower [[S band]] deep-space radio communications allocations, and some higher frequencies on a more-or-less experimental basis, such as in the [[K band (IEEE)|K band]].)

Notable deep [[space probe]] programs that have employed X band communications include the [[Viking program|Viking Mars landers]]; the [[Voyager program|Voyager]] missions to [[Jupiter]], [[Saturn]], and beyond; the [[Galileo (spacecraft)|Galileo Jupiter orbiter]]; the [[New Horizons]] mission to [[Pluto]] and the [[Kuiper belt]], the [[Curiosity rover]] and the [[Cassini-Huygens]] Saturn orbiter.<ref>{{cite web |title=Radio Science Subsystem (RSS) |url=https://solarsystem.nasa.gov/missions/cassini/mission/spacecraft/cassini-orbiter/radio-science-subsystem/ |website=NASA Science Solar System Exploration |access-date=23 August 2022}}</ref>

An important use of the X band communications came with the two [[Viking program]] landers. When the planet Mars was passing near or behind the Sun, as seen from the Earth, a Viking lander would transmit two simultaneous continuous-wave carriers, one in the S band and one in the X band in the direction of the Earth, where they were picked up by [[DSN Corporation|DSN]] ground stations. By making simultaneous measurements at the two different frequencies, the resulting data enabled theoretical physicists to verify the mathematical predictions of [[Albert Einstein]]'s [[General Theory of Relativity]]. These results are some of the best confirmations of the General Theory of Relativity.{{cn|date=December 2023}}

The new European double Mars Mission [[ExoMars]] will also use X band communication, on the instrument LaRa, to study the internal structure of Mars, and to make precise measurements of the rotation and orientation of Mars by monitoring two-way Doppler frequency shifts between the surface platform and Earth. It will also detect variations in angular momentum due to the redistribution of masses, such as the migration of ice from the polar caps to the atmosphere.{{cn|date=December 2023}}

===X band NATO frequency requirements===
The International Telecommunication Union (ITU), the international body which allocates radio frequencies for civilian use, is not  authorised to allocate frequency bands for military [[radio communication]].  This is also the case pertaining to X band military [[communications satellite]]s. However, in order to meet military radio spectrum requirements, e.g. for [[fixed-satellite service]] and [[mobile-satellite service]], the [[North Atlantic Treaty Organization|NATO]] nations negotiated the [[NATO Joint Civil/Military Frequency Agreement]] (NJFA).<ref>{{Cite web|url=http://www.akos-rs.si/files/Zakonodaja/Direktive_in_priporocila/mednarodni_sporazumi/CM-Ag.pdf|title=''NATO Joint Civil/Military Frequency Agreement (NJFA)''|access-date=2016-01-08|archive-date=2016-03-04|archive-url=https://web.archive.org/web/20160304102758/http://www.akos-rs.si/files/Zakonodaja/Direktive_in_priporocila/mednarodni_sporazumi/CM-Ag.pdf|url-status=dead}}</ref>

{| class="wikitable"
|- align="center"
! (a) || (b) || (c) || (d)
|-align="center"
| colspan="4" bgcolor="DCDCDC"| 
|-7250
|7250-7750<br />MHz
| FIXED<br />FIXED-SATELLlTE (s-E), <br />MOBILE-SATELLlTE (s-E) <br />(S5.461)
|1. Essential military requirements for satellite downlinks; the mobile satellite sub-band 7250-7300&nbsp;MHz is for naval and [[land mobile earth station]]s.<br />2. Military requirement for fixed systems in some countries.
|1. This is a harmonised NATO band type 1for satellite downlinks.<br />
2. 7250-7300&nbsp;MHz is paired with 7975-8025&nbsp;MHz for the MOBILE-SATELLlTE allocation.<br />3. The FIXED and MOBILE services are not to be implemented in the band 7250-7300&nbsp;MHz in most NATO countries, including ITU Region 2.<br />4. In the band 7300-7750&nbsp;MHz the transportable [[earth station]]s cannot claim protection
from the other services.
|-7750 
|7750-7900<br />MHz|| FIXED|| Military requirements for existing NATO fixed systems in some countries.||
|- 
|7900-8400<br />MHz
| FIXED-SATELLlTE (E-s),<br />MOBILE-SATELLlTE (E-s) (S5.461), <br />FIXED<br />[[Earth exploration-satellite service|Earth exploration-satellite]] (s-E)<br /> (S5.462A),<br /> 
|1. Essential military requirements for satellite uplinks; the mobile satellite sub-band 7975-8025&nbsp;MHz is for naval and land mobile satellite earth stations. <br />2. Military requirement for earth exploration satellite (downlink) purposes in the band 8025-8400&nbsp;MHz. <br />3. Military requirement for fixed systems in some countries.
|1. This is a harmonised NATO band type 1 for satellite uplinks. <br />2. 7975-8025&nbsp;MHz is paired with 7250-7300&nbsp;MHz for the MOBILE-SATELLlTE allocation. <br />3. The FIXED and MOBILE services are not to be implemented in 7975-8025&nbsp;MHz in most NATO countries, including ITU Region 2.<br />4. In the bands 7900-7975 and 8025-8400&nbsp;MHz the transportable earth stations must not cause harmful interference to other services.
|-
|8500&nbsp;MHz-<br />10.5&nbsp;GHz <br />|| RADIOLOCATION <br />Radiolocation || Military requirement for land, airborne and naval radars. ||Harmonised NATO band type 2 in selected sub-bands is desirable.
|-
|}

== Amateur radio ==
The Radio Regulations of the International Telecommunication Union allow [[amateur radio]] operations in the frequency range 10.000 to 10.500&nbsp;GHz,<ref>{{Cite web|url=http://www.iaru-r1.org/VHF_Handbook_V5_11.pdf|archive-url=https://web.archive.org/web/20090205161745/http://www.iaru-r1.org/VHF_Handbook_V5_11.pdf |url-status=dead |title=VHF Handbook of IARU Region 1 (2006), pg. 50|archive-date=February 5, 2009}}</ref> and [[amateur satellite]] operations are allowed in the range 10.450 to 10.500&nbsp;GHz.  This is known as the [[3-centimeter band]] by amateurs and the X-band by [[AMSAT]].

== Other uses ==
[[Motion detector]]s often use 10.525&nbsp;GHz.<ref>{{Cite web|url=http://www.g3pho.free-online.co.uk/microwaves/wideband.htm|title=10GHz wideband transceiver|website=www.g3pho.free-online.co.uk}}</ref>  10.4&nbsp;GHz is proposed for [[traffic light]] crossing detectors. Comreg in Ireland has allocated 10.450&nbsp;GHz for traffic sensors as SRD.<ref>{{cite web|url=http://www.comreg.ie/radio_spectrum/exemptions.541.488.rslicensing.html |title=Radio Spectrum |access-date=June 1, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20120318235802/http://www.comreg.ie/radio_spectrum/exemptions.541.488.rslicensing.html |archive-date=March 18, 2012 }}</ref>

Many [[electron paramagnetic resonance]] (EPR) spectrometers operate near 9.8&nbsp;GHz.

[[Particle accelerator]]s may be powered by X-band [[RF]] sources. The frequencies are then standardized at 11.9942&nbsp;GHz (Europe) or 11.424&nbsp;GHz (US),<ref>F. Peauger, A. Hamdi, S. Curt,  S. Doebert, G. McMonagle, G. Rossat, K.M. Schirm, I. Syratchev, L. Timeo, S. Kuzikhov, A.A. Vikharev, A. Haase, D. Sprehn, A. Jensen, E.N. Jongewaard, C.D. Nantista and A. Vlieks: [http://accelconf.web.cern.ch/AccelConf/IPAC10/papers/THPEB053.pdf A 12&nbsp;GHz RF POWER SOURC E FOR THE CLIC STUDY]</ref><ref>{{cite web|url=https://www.jlab.org/conferences/FLS2012/talks/Thur/isu_jlab39_fls2012_57_final.PDF |title=Performance Comparison of S-band, C-band, and X-band RF Linac based XFELs| access-date=2023-09-10}}</ref> which is the second harmonic of [[C band (IEEE)#Particle accelerators|C-band]] and fourth harmonic of [[S band#Other uses|S-band]]. The European X-band frequency is used for the [[Compact Linear Collider]] (CLIC).

==See also==
*[[Cassegrain reflector]]
*[[Directional antenna]]
*[[XTAR]]
*[[Sea-based X-band Radar|Sea-based X band Radar]]
*[[New Horizons#Telecommunications and data handling|New Horizons telecommunications]]
*[[Voyager program#Spacecraft design]]
*[[Earth observation satellites transmission frequencies]]
*[[TerraSAR-X]]: a German Earth observation satellite

==References==
{{Reflist}}

==External links==
*[https://www.ntia.doc.gov/osmhome/allochrt.pdf United States Frequency Allocations]
*[http://www.g3pho.free-online.co.uk/microwaves/wideband.htm 10GHz wideband transceiver]

{{radio spectrum}}
{{EMSpectrum}}

[[Category:Microwave bands]]
[[Category:Radar]]
[[Category:Radio frequency propagation]]
[[Category:X band radar| ]]