Product Code Database
The Ku band () is the portion of the electromagnetic spectrum in the microwave range of frequencies from 12 to 18 gigahertz (GHz). The symbol is short for "K-under" (originally ), because it is the lower part of the original NATO K band, which was split into three bands (Ku, K, and Ka band) 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. In radar applications, it ranges from 12 to 18 Hertz according to the formal definition of radar frequency band nomenclature in IEEE Standard 521–2002. IEEE Std 521 - 2002 URL only available to IEEE membersNote that in the band 11.2–12 GHz the working definitions of Ku band and X band overlap; satellite communications engineers would generally regard frequencies above 11.2 GHz as being part of the Ku band.
Ku band is primarily used for satellite communications, most notably the downlink used by direct broadcast satellites to broadcast satellite television, and for specific applications such as NASA's Tracking Data Relay Satellite used for International Space Station (ISS) communications and SpaceX Starlink satellites. Ku band satellites are also used for backhauls and particularly for satellite from remote locations back to a television network's studio for editing and broadcasting. The band is split by the International Telecommunication Union (ITU) into multiple segments that vary by geographical region. NBC was the first television network to uplink a majority of its affiliate feeds via Ku band in 1983.
Some frequencies in this radio band are employed in used by law enforcement to detect vehicles speeding, especially in Europe. Radar Detectors Glossary
The 12.2 to 12.7 GHz (LOF 11.25 to 11.75 GHz) segment is allocated to the BSS (broadcasting satellite service). BSS (DBS direct broadcast satellites) normally carry 16 to 32 transponders of 27 Megahertz bandwidth running at 100 to 240 watts of power, allowing the use of receiver antennas as small as 18 inches (450 mm).
Measurements of rain attenuation in Indonesia have been done for satellite communication links in Padang, Cibinong, Surabaya and Bandung. The DAH Model for rain attenuation prediction is valid for Indonesia, as is the ITU model. The DAH model has become an ITU recommendation since 2001 (Recommendation No. ITU-R P.618-7). This model can create a 99.7% available link so that Ku-band can be applied in Indonesia.
Use of the Ku-band for satellite communications in tropical regions like Indonesia is becoming more frequent. Several satellites above Indonesia have Ku-band , and even Ka band transponders. NSS 6, launched in December 2002 and positioned at 95° East, contains only Ku-band transponders with a footprint on Indonesia (Sumatra, Java, Borneo, Sulawesi, Bali, Nusa Tenggara, Moluccas). NSS 6 is intended to be replaced by SES-12 at the same location, which launched in June 2018 and carries 54 Ku-band transponders. The IPSTAR 1 satellite, launched in 2004 also uses Ku band footprints. Other satellites that provides Ku band covers Indonesia are MEASAT-3b, JCSAT-4B, AsiaSat 5, ST-2, Chinasat 11, Koreasat 8/ABS-2, SES-8, SES-9, Telkom-3S, and Nusantara Satu.
A major attraction of the band over lower frequency microwave bands is that the shorter wavelengths allow sufficient angular resolution to separate the signals of different communication satellites to be achieved with smaller terrestrial parabolic antennas. From the Rayleigh criterion, the diameter of a parabolic dish required to create a radiation pattern with a given angular FWHM (antenna gain) is proportional to the wavelength, and thus inversely proportional to the frequency. At 12 GHz a 1-meter dish is capable of focusing on one satellite while sufficiently rejecting the signal from another satellite only 2 degrees away. This is important because satellites in FSS (Fixed Satellite Service) service (11.7-12.2 GHz in the U.S.) are only 2 degrees apart. At 4 GHz (C-band) a 3-meter dish is required to achieve this narrow angular resolution. Note the inverse linear correlation between dish size and frequency. For Ku satellites in DBS (Direct Broadcast Satellite) service (12.2-12.7 GHz in the U.S.) dishes much smaller than 1-meter can be used because those satellites are spaced 9 degrees apart. As power levels on both C and Ku band satellites have increased over the years, dish beam-width has become much more critical than gain.
The Ku band also offers a user more flexibility. A smaller dish size and a Ku band system's freedom from terrestrial operations simplifies finding a suitable dish site. For the end users Ku band is generally cheaper and enables smaller antennas (both because of the higher frequency and a more focused beam). Satellite Communications: Advantage and Disadvantages Ku band is also less vulnerable to rain fade than the Ka band frequency spectrum.
Another weather-caused degradation called "snow fade" is not specific to the Ku band. It is due to snow or ice accumulation on a dish significantly altering its focal point.
The satellite operator's Earth station antenna requires more accurate position control when operating at Ku band due to its much narrower beam focus compared to C band for a dish of a given size. Position feedback accuracies are higher and the antenna may require a closed loop control system to maintain position under wind loading of the dish surface.
|
|
