X band in the context of "Institute of Electrical and Electronics Engineers"

Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequencies between 300 MHz and 300 GHz, broadly construed. A more common definition in radio-frequency engineering is the range between 1 and 100 GHz (wavelengths between 30 cm and 3 mm), or between 1 and 3000 GHz (30 cm and 0.1 mm). In all cases, microwaves include the entire super high frequency (SHF) band (3 to 30 GHz, or 10 to 1 cm) at minimum. The boundaries between far infrared, terahertz radiation, microwaves, and ultra-high-frequency (UHF) are fairly arbitrary and differ between different fields of study.

The prefix micro- in microwave indicates that microwaves are small (having shorter wavelengths), compared to the radio waves used in prior radio technology. Frequencies in the microwave range are often referred to by their IEEE radar band designations: S, C, X, K_u, K, or K_a band, or by similar NATO or EU designations.

Super high frequency (SHF) is the ITU designation for radio frequencies (RF) in the range between 3 and 30 gigahertz (GHz). This band of frequencies is also known as the centimetre band or centimetre wave as the wavelengths range from one to ten centimetres. These frequencies fall within the microwave band, so radio waves with these frequencies are called microwaves. The small wavelength of microwaves allows them to be directed in narrow beams by aperture antennas such as parabolic dishes and horn antennas, so they are used for point-to-point communication and data links and for radar. This frequency range is used for most radar transmitters, wireless LANs, satellite communication, microwave radio relay links, satellite phones (S band), and numerous short range terrestrial data links. They are also used for heating in industrial microwave heating, medical diathermy, microwave hyperthermy to treat cancer, and to cook food in microwave ovens.

Frequencies in the SHF range are often referred to by their IEEE radar band designations: S, C, X, K_u, K, or K_a band, or by similar NATO or EU designations.

Marine radars are X band or S band radars on ships, used to detect other ships and land hazards, to provide bearing and distance for collision avoidance and navigation at sea. They are electronic navigation instruments that use a rotating antenna to sweep a narrow beam of microwaves around the water surface surrounding the ship to the horizon, detecting targets by microwaves reflected from them, generating a picture of the ship's surroundings on a display. The X-Band and S-Band radar has different characteristics and detection capabilities compared with each other. Most merchant ships carry at least one of each type to ensure adequate target detection and response. For example, the S-band operates better in sea clutter and rain than the X-band, however, the X-band has greater definition and accuracy in clear weather.

Radar is a vital navigation component for safety at sea and near the shore. It allows a 'lookout' to be maintained, being one of the approved available means for compliance with Rule 5, keeping a proper lookout under the International Regulations for Preventing Collisions at Sea. Captains and the bridge teams of ships need to be able to maneuver their ships in close proximity to navigational hazards in the worst of conditions. These include a need to navigate "blind", when there is poor or no visibility at night or due to bad weather such as fog. In addition to vessel-based marine radars, in port or in harbour, shore-based vessel traffic service radar systems are used by harbormasters and coast guard to monitor and regulate ship movements in busy waters.

The Spaceborne Imaging Radar (SIR) – full name 'Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR)', is a synthetic aperture radar which flew on two separate shuttle missions. Once from the Space Shuttle Endeavour in April 1994 on (STS-59) and again in October 1994 on (STS-68). The radar was run by NASA's Space Radar Laboratory. SIR utilizes 3 radar frequencies: L band (24 cm wavelength), C band (6 cm) and X band (3 cm), allowing for study of geology, hydrology, ecology and oceanography. Comparing radar images to data collected by teams of people on the ground as well as aircraft and ships using simultaneous measurements of vegetation, soil moisture, sea state, snow and weather conditions during each flight. The imaging radar was able to take images anytime regardless of clouds cover. The Radar-C system was built and operated by NASA's Jet Propulsion Laboratory (JPL). The mission was a joint work of NASA with the German and Italian space agencies. Each of the week long mission scanned about 50 million square kilometers of the Earth's surface, (19.3 million square miles).

The SIR mission revealed hidden river channels in the Sahara Desert indicating significant climate change in the past. SIR was also used for volcano research by keeping researchers a safe distance from hazardous and often inaccessible areas. The radar was also used to generate detailed three dimensional mappings of the Earth's surface.

Svalbard Satellite Station (Norwegian: Svalbard satellittstasjon) or SvalSat is a satellite ground station located on Platåberget near Longyearbyen in Svalbard, Norway. Opened in 1997, it is operated by Kongsberg Satellite Services (KSAT), a joint venture between Kongsberg Defence & Aerospace and the Norwegian Space Centre (NSC). SvalSat and KSAT's Troll Satellite Station (TrollSat) in Antarctica are the only ground stations that can see a low altitude polar orbiting satellite (e.g., in Sun-synchronous orbit) on every revolution as the Earth rotates. As of 2021, the facility consists of 100 multi-mission and customer-dedicated antennas which operate in the C, L, S, X and K bands. The station provides ground services to more satellites than any other facility in the world.

Customers with their own installations include the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), the National Aeronautics and Space Administration (NASA), the European Space Agency (ESA) and the National Oceanic and Atmospheric Administration (NOAA). The station also reads and distributes data from the Japanese Hinode solar research satellite. The facility has seen a large increase in smaller customers after 2004, when the Svalbard Undersea Cable System started providing a fiber Internet connection. Concessions for downloading are only issued to civilian satellites, yet some data has been indirectly used by armed forces. There is a disagreement as to whether this constitutes a breach of the Svalbard Treaty.