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Ku band

The Ku band (pronunciation: /ˌkeɪˈjuː/) is the 12–18 GHz portion of the electromagnetic spectrum in the

microwave range of frequencies. This symbol refers to "K-under" (originally German: Kurz-unter)—in other

words, the band directly below the K-band. In radar applications, it ranges from 12-18 GHz according to the

formal definition of radar frequency band nomenclature in IEEE Standard 521-2002.[1][2]

Ku band is primarily used for satellite communications, most notably for fixed and broadcast services, and for

specific applications such as NASA's Tracking Data Relay Satellite used for both space shuttle and

International Space Station (ISS) communications. 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 into multiple segments that vary by geographical region by the International

Telecommunication Union (ITU). 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 used for vehicle speed detection by law enforcement, especially in

 

Europe.[3]

Segments and regions
The Americas
Segments in most of North and South America are represented by ITU Region 2 from 11.7 to 12.2 GHz (Local

Oscillator Frequency (LOF) 10.750 to 11.250 GHz), allocated to the FSS (fixed satellite service), uplink from

14.0 to 14.5 GHz. There are more than 22 FSS Ku band satellites orbiting over North America, each carrying 12

to 48 transponders, 20 to 120 watts per transponder, and requiring a 0.8-m to 1.5-m antenna for clear

reception.

 

The 12.2 to 12.7 GHz (LOF 11.250 to 11.750 GHz) segment is allocated to the BSS (broadcasting satellite

service). BSS (DBS direct broadcast satellites) normally carry 16 to 32 transponders of 27 MHz bandwidth

running at 100 to 240 watts of power, allowing the use of receiver antennas as small as 18 inches (450 mm).

 

Europe and Africa[edit]
Segments in those regions are represented by ITU Region 1 and they are, the 11.45 to 11.7 and 12.5 to 12.75

GHz bands are allocated to the FSS (fixed satellite service, uplink 14.0 to 14.5 GHz). In Europe Ku band is

used from 10.7 to 12.75 GHz (LOF Low 9.750 GHz, LOF High 10.600 GHz) for direct broadcast satellite services

such as those carried by the Astra satellites. The 11.7 to 12.5 GHz segment is allocated to the BSS

(broadcasting satellite service).

 

Australia
Australia is part of ITU Region 3 and the Australian regulatory environment provides a class license that

covers downlinking from 11.70 GHz to 12.75 GHz and uplinking from 14.0 GHz to 14.5 GHz.[4]

 

Indonesia
The ITU has categorized Indonesia as Region P, countries with very high rain precipitation. This statement has

made many people unsure about using Ku-band (11 – 18 GHz) in Indonesia. If frequencies higher than 10 GHz are

used in a heavy rain area, a decrease in communication availability results. This problem can be solved by

using an appropriate link budget when designing the wireless communication link. Higher power can overcome the

loss to rain fade.

 

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, in

addition to 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.

The use of the Ku-band for satellite communications in tropical regions like Indonesia is becoming more

frequent. Several satellites above Indonesia have Ku-band transponders, and even Ka band transponders.

Newskies (NSS 6), launched in December 2002 and positioned at 95° East, contains only Ku-band transponders

with a footprint on Indonesia (Sumatra, Java, Borneo, Celebes, Bali, Nusa Tenggara, Moluccas). The iPSTAR

satellite, launched in 2004 also uses Ku band footprints. Other satellites that provides Ku band covers

Indonesia are Palapa D, MEASAT 3/3A, JSAT Corporation JCSAT 4B, AsiaSat 5, ST 2, Chinasat 11, Korea Telecom

Koreasat 8/ABS 2 (2nd half 2013).

 

Others
Other ITU allocations have been made within the Ku band to the fixed service (microwave towers), radio

astronomy service, space research service, mobile service, mobile satellite service, radiolocation service

(radar), amateur radio service, and radionavigation. However, not all of these services are actually operating

in this band and others are only minor users.

 

Advantages
Compared with C-band, Ku band is not similarly restricted in power to avoid interference with terrestrial

microwave systems, and the power of its uplinks and downlinks can be increased. This higher power also

translates into smaller receiving dishes and points out a generalization between a satellite's transmission

and a dish's size. As the power increases, the dish's size can decrease.[5] This is because the purpose of the

dish element of the antenna is to collect the incident waves over an area and focus them all onto the

antenna's actual receiving element, mounted in front of the dish (and pointed back towards its face); if the

waves are more intense, fewer of them need to be collected to achieve the same intensity at the receiving

element.

 

Also, as frequencies increase, parabolic reflectors become more efficient at focusing them. The focusing is

equivalent given the size of the reflector is the same with respect to the wavelength. 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

of a focus beam. 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).[6] Ku band is

also less vulnerable to rain fade than the Ka band frequency spectrum.

 

The satellite operator's Earth Station antenna does require more accurate position control when operating at

Ku band due to its much narrower focus beam 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.

 

Disadvantages
There are, however, some disadvantages of Ku band system. Especially at frequencies higher than 10 GHz in

heavy rainfall areas, a noticeable degradation occurs, due to the problems caused by and proportional to the

amount of rainfall (commonly known as "rain fade").[7] This problem can be mitigated, however, by deploying an

appropriate link budget strategy when designing the satellite network, and allocating a higher power

consumption to compensate rain fade loss. The Ku band is not only used for television transmission, which some

sources imply, but also very much for digital data transmission via satellites, and for voice/audio

transmissions.

 

The higher frequency spectrum of the Ku band is particularly susceptible to signal degradation, considerably

more so than C-band satellite frequency spectrum. A similar phenomenon, called "snow fade" (where snow or ice

accumulation significantly alters the focal point of a dish) can also occur during winter precipitation. Also,

the Ku band satellites typically require considerably more power to transmit than the C-band satellites. Under

both "rain fade" and "snow fade" conditions, Ka and Ku band losses can be marginally reduced using super-

hydrophobic Lotus effect coatings. Moreover, snow fade is caused not only by snow accumulation on the antenna,

but also by attenuation caused by airborne snow along the RF signal path.

 

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