KU BAND
Satellite Communications Glossary
Satellite Communications — Satellite Frequencies — Ku Band
Information on Ku Band
To avoid the congestion in C band, newer satellite communications
satellites operate in the higher frequency bands such as Ku
band. Most modern satellites have a mix of C-band
and Ku-band transponders, with the proportion depending on their area
of operations. In addition to an increase in capacity, Ku
band has the advantage that portions of the band
are not shared with terrestrial radio networks and coordination is
therefore not required.
The ITU has allocated three portions within
Ku band to different satellite communications services within different
regions. The 14/12-GHz portion (14.00-14.50 GHz uplink and 11.70-12.20 GHz
downlink) is allocated within Region 2 (the Americas) for FSS
and is not shared with terrestrial systems. Regions 1 and
3 are allocated the 14/11-GHz portion (14.00-14.50 GHz uplink and
10.95-11.70 GHz downlink) for FSS and must coordinate for the
downlink frequencies due to sharing with terrestrial services. The third
portion of Ku band, 18/12 GHz, is allocated to
the BSS (broadcast television and other direct-to-home transmissions) and is
not shared with terrestrial services. These broadcast services can be
delivered to smaller, less-expensive antennas because of the higher frequency
of Ku band and the higher transmit powers (60-120W
rather than 20-40W) that are possible because sharing is not
required. To reduce interference between satellites, Ku-band BSS satellites are
spaced 6-9° apart (compared with a 2° spacing for FSS
satellites).
The main disadvantage of Ku band for satellite communications
is that the higher frequencies are more heavily affected by
atmospheric attenuation and, in particular, by rain. While the link
margin required depends on the actual frequency in use and
the elevation angle (that is, on slant range through the
atmosphere), as an indication, Ku-band link margins are of the
order of 8 dB compared with approximately 2 dB required
in C band. Fortunately, due to the reduced requirement for
sharing, higher satellite powers can compensate for the higher fade
margins. The greater link margin, however, tends to reduce the
application of Ku-band satellites in tropical regions.
Other topics in our resources on Satellite Communications related to Ku Band include:
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