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Frequency range | 8.0–12.0GHz |
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Wavelength range | 3.75–2.5cm |
Related bands |
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TheX band is the designation for a band offrequencies in themicrowaveradio region of theelectromagnetic spectrum. In some cases, such as incommunication engineering, the frequency range of the X band is set at approximately 7.0–11.2 GHz.[citation needed] Inradar engineering, the frequency range is specified by theInstitute of Electrical and Electronics Engineers (IEEE) as 8.0–12.0 GHz. The X band is used for radar,satellite communication, andwireless computer networks.
X band is used in radar applications, includingcontinuous-wave, pulsed, single-polarization, dual-polarization,synthetic aperture radar, andphased arrays. X-band radar frequency sub-bands are used incivil,military, andgovernment institutions forweather monitoring,air traffic control,maritime vessel traffic control,defense tracking, andvehicle speed detection for law enforcement.[1][2]
X band is often used in modern radars. The shorterwavelengths of the X band provide higher-resolution imagery fromhigh-resolutionimaging radars 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.[3]
The X band 10.15 to 10.7 GHz segment is used for terrestrialbroadband in many countries, such as Brazil, Mexico, Saudi Arabia, Denmark, Ukraine, Spain and Ireland.[4]Alvarion,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 providingcable internet to customers, uses some X band frequencies. The home / businesscustomer-premises equipment (CPE) has a single coaxial cable with a power adapter connecting to an ordinary cable modem. The local oscillator is usually 9750 MHz, the same as for Ku band satellite TV LNB. Two way applications such as broadband typically use a 350 MHz TX offset.
Small portions of the X band are assigned by theInternational Telecommunication Union (ITU) exclusively for deep space telecommunications. The primary user ofthis allocation is the AmericanNASADeep Space Network (DSN). DSN facilities are inGoldstone, California (in theMojave Desert), nearCanberra, Australia, and nearMadrid, Spain, and provide continual communications from the Earth to almost any point in theSolar System independent of Earth rotation. (DSN stations are also capable of using the older and lowerS band deep-space radio communications allocations, and some higher frequencies on a more-or-less experimental basis, such as in theK band.)
Notable deepspace probe programs that have employed X band communications include theViking Mars landers; theVoyager missions toJupiter,Saturn, and beyond; theGalileo Jupiter orbiter; theNew Horizons mission toPluto and theKuiper belt, theCuriosity rover and theCassini-Huygens Saturn orbiter.[5]
An important use of the X band communications came with the twoViking 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 byDSN ground stations. By making simultaneous measurements at the two different frequencies, the resulting data enabled theoretical physicists to verify the mathematical predictions ofAlbert Einstein'sGeneral Theory of Relativity. These results are some of the best confirmations of the General Theory of Relativity.[citation needed]
The new European double Mars MissionExoMars 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.[citation needed]
The International Telecommunication Union (ITU), the international body which allocates radio frequencies for civilian use, is not authorised to allocate frequency bands for militaryradio communication. This is also the case pertaining to X band militarycommunications satellites. However, in order to meet military radio spectrum requirements, e.g. forfixed-satellite service andmobile-satellite service, theNATO nations negotiated theNATO Joint Civil/Military Frequency Agreement (NJFA).[6]
| (a) | (b) | (c) | (d) |
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| 7250-7750 MHz | FIXED FIXED-SATELLlTE (s-E), MOBILE-SATELLlTE (s-E) (S5.461) | 1. Essential military requirements for satellite downlinks; the mobile satellite sub-band 7250-7300 MHz is for naval andland mobile earth stations. 2. Military requirement for fixed systems in some countries. | 1. This is a harmonised NATO band type 1for satellite downlinks. 2. 7250-7300 MHz is paired with 7975-8025 MHz for the MOBILE-SATELLlTE allocation. |
| 7750-7900 MHz | FIXED | Military requirements for existing NATO fixed systems in some countries. | |
| 7900-8400 MHz | FIXED-SATELLlTE (E-s), MOBILE-SATELLlTE (E-s) (S5.461), FIXED Earth exploration-satellite (s-E) (S5.462A), | 1. Essential military requirements for satellite uplinks; the mobile satellite sub-band 7975-8025 MHz is for naval and land mobile satellite earth stations. 2. Military requirement for earth exploration satellite (downlink) purposes in the band 8025-8400 MHz. 3. Military requirement for fixed systems in some countries. | 1. This is a harmonised NATO band type 1 for satellite uplinks. 2. 7975-8025 MHz is paired with 7250-7300 MHz for the MOBILE-SATELLlTE allocation. 3. The FIXED and MOBILE services are not to be implemented in 7975-8025 MHz in most NATO countries, including ITU Region 2. 4. In the bands 7900-7975 and 8025-8400 MHz the transportable earth stations must not cause harmful interference to other services. |
| 8500 MHz- 10.5 GHz | RADIOLOCATION Radiolocation | Military requirement for land, airborne and naval radars. | Harmonised NATO band type 2 in selected sub-bands is desirable. |
The Radio Regulations of the International Telecommunication Union allowamateur radio operations in the frequency range 10.000 to 10.500 GHz,[7] andamateur satellite operations are allowed in the range 10.450 to 10.500 GHz. This is known as the3-centimeter band by amateurs and the X-band byAMSAT.
Motion detectors often use 10.525 GHz.[8] 10.4 GHz is proposed fortraffic light crossing detectors. Comreg in Ireland has allocated 10.450 GHz for traffic sensors as SRD.[9]
Manyelectron paramagnetic resonance (EPR) spectrometers operate near 9.8 GHz.
Particle accelerators may be powered by X-bandRF sources. The frequencies are then standardized at 11.9942 GHz (Europe) or 11.424 GHz (US),[10][11] which is the second harmonic ofC-band and fourth harmonic ofS-band. The European X-band frequency is used for theCompact Linear Collider (CLIC).
ManyRadio Astronomy facilities have receivers which work in the X-band including theGreen Bank Telescope[12] and theVery Large Array[13].Radio Astronomy has a Frequency Allocation for (quiet) bands at 10.6-10.68 GHz, and 10.68-10.7 GHz, but the receivers work across a much wider range of the entire X-band (e.g. 7-12 GHz) trying to take advantages of as much bandwidth as possible to be sensitive to faint astronomical sources.
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