Page 23 - Satellite Communications, Fourth Edition

Overview of Satellite Systems 3

to as direct broadcast satellite (DBS) service [in Europe it may be known
as direct-to-home (DTH) service]. Mobile satellite services would include
land mobile, maritime mobile, and aeronautical mobile. Navigational
satellite services include global positioning systems (GPS), and satel-
lites intended for the meteorological services often provide a search
and rescue service.
Table 1.1 lists the frequency band designations in common use for
satellite services. The Ku band signifies the band under the K band, and
the Ka band is the band above the K band. The Ku band is the one used
at present for DBS, and it is also used for certain FSS. The C band is
used for FSS, and no DBS is allowed in this band. The very high fre-
quency (VHF) band is used for certain mobile and navigational services
and for data transfer from weather satellites. The L band is used for
mobile satellite services and navigation systems. For the FSS in the C
band, the most widely used subrange is approximately 4 to 6 GHz. The
higher frequency is nearly always used for the uplink to the satellite,
for reasons that will be explained later, and common practice is to denote
the C band by 6/4 GHz, giving the uplink frequency first. For the direct
broadcast service in the Ku band, the most widely used range is approxi-
mately 12 to 14 GHz, which is denoted by 14/12 GHz. Although frequency
assignments are made much more precisely, and they may lie somewhat
outside the values quoted here (an example of assigned frequencies in
the Ku band is 14,030 and 11,730 MHz), the approximate values stated
are quite satisfactory for use in calculations involving frequency, as will
be shown later in the text.
Care must be exercised when using published references to frequency
bands, because the designations have been developed somewhat differ-
ently for radar and communications applications; in addition, not all
countries use the same designations.

TABLE 1.1 Frequency Band Designations
Frequency range, (GHz) Band designation
0.1–0.3 VHF
0.3–1.0 UHF
1.0–2.0 L
2.0–4.0 S
4.0–8.0 C
8.0–12.0 X
12.0–18.0 Ku
18.0–27.0 K
27.0–40.0 Ka
40.0–75 V
75–110 W
110–300 mm
300–3000 μm