The Ka band (pronounced as either "kay-ay band" or "ka band") is a portion of the microwave part of the electromagnetic spectrum. The designation "Ka-band" is from Kurz-above, which stems from the German word kurz, meaning "short".[1]
There is no standard definition of Ka-band. IEEE Standard letter designations for Radar Bands define the nominal frequency range for Ka band in the range 27–40 gigahertz (GHz) in Tables 1 and 2 of IEEE Standard 521[2]
i.e. wavelengths from slightly over one centimeter down to 7.5 millimeters.[3]
The ITU however approves Ka-band satellite networks in the 17.3-31 GHz frequency range,[4]
with most Ka-band satellite networks having uplinks in the 27.5-31 GHz and downlinks in the 17.7-21.2 GHz range.[4]
The band is called Ka, short for "K-above" because it is the upper part of the original (now obsolete) NATO K band, which was split into three bands because of the presence of the atmospheric water vapor resonance peak at 22.24 GHz (1.35 cm), which made the center unusable for long range transmission. The 30/20 GHz band is used in communications satelliteuplinks in either the 27.5 GHz or 31 GHz bands,[5] and in high-resolution, close-range targeting radars aboard military airplanes. Some frequencies in this radio band are used for vehicle speed detection by law enforcement.[6] The Kepler Mission used this frequency range to downlink the scientific data collected by the space telescope.[7] This frequency is also used for remote sensing of clouds by radar, by both ground-based[8] or satellite[9] systems such as INCUS.
Planned future satellite projects using the Ka-band include Amazon's Project Kuipersatellite internet constellation in LEO,[18]SES's multi-orbit satellite internet system of the SES-17 satellite in GEO (launched in October 2021; in position and fully operational in June 2022)[19] and the O3b mPOWER constellation in MEO (first two satellites launched December 2022, nine more 2023-2024, and starting service in Q3 2023).[20][21][22]
